RUGGED, GEL-FREE, LITHIUM-FREE, HIGH ENERGY DENSITY SOLID-STATE ELECTROCHEMICAL ENERGY STORAGE DEVICES

Abstract

Described are solid-state electrochemical energy storage devices and methods of making solid-state electrochemical energy storage devices in which components of the batteries are truly solid-state and do not comprise a gel. Nor do they rely on lithium-containing electrolytes. Electrolytes useful with the solid-state electrochemical energy storage described herein include, for example, ceramic electrolytes exhibiting a crystal structure including voids or crystallographic defects that permit conduction or migration of oxygen ions across a layer of the ceramic electrolyte. Disclosed methods of making solid-state electrochemical energy storage devices include multi-stage deposition processes, in which an electrode is deposited in a first stage and an electrolyte is deposited in a second stage.

Claims

1-5. (canceled)

1. A Faradaic solid-state energy storage device comprising: a first electrode comprising a first redox-supporting metal, an oxide/hydride/nitride of the first redox-supporting metal, or a combination of the first redox-supporting metal and the oxide/hydride/nitride of the first redox-supporting metal, wherein the first electrode has a first thickness greater than 1 nm and less than or equal to 80 nm; a solid electrolyte positioned in direct contact with the first electrode and comprising a solid-state, ion conducting ceramic electrolyte, wherein the solid electrolyte has a second thickness greater than 1 nm and less than or equal to 500 nm; a second electrode positioned in direct contact with the solid electrolyte and comprising a second redox-supporting metal, an oxide/hydride/nitride of the second redox-supporting metal, or a combination of the second redox-supporting metal and the oxide/hydride/nitride of the second redox-supporting metal, wherein the second electrode has a third thickness greater than 1 nm and less than or equal to 80 nm; and an oxygen/hydrogen/nitrogen storage structure flanking and in gaseous communication with the solid electrolyte for providing oxygen/hydrogen/nitrogen to interstices within a crystalline structure of the solid electrolyte.

2. The Faradaic solid-state energy storage device of claim 1, wherein the oxygen/hydrogen/nitrogen storage structure comprises a crystalline layer of an oxygen/hydrogen/nitrogen sponge material.

3. The Faradaic solid-state energy storage device of claim 1, wherein the oxygen/hydrogen/nitrogen storage structure comprises cobalt, a cobalt salt, cerium, or ceria.

4. The Faradaic solid-state energy storage device of claim 1, wherein the oxygen/hydrogen/nitrogen storage structure comprises strontium cobaltite or [{(2,6-bis(N,N-bis(2-pyridylmethyl)-aminomethyl)-4-tert-butylphenolato)Co.sub.2.sup.II(NO.sub.3)}.sub.2(2-amino-1,4-benzenedicarboxylate)](NO.sub.3).sub.2.H.sub.2O.

5. The Faradaic solid-state energy storage device of claim 1, wherein the oxygen/hydrogen/nitrogen storage structure provides oxygen/hydrogen/nitrogen ions to the solid electrolyte for participation in redox reactions at the first electrode or the second electrode.

6. The Faradaic solid-state energy storage device of claim 1, wherein a density of oxygen absorbed at the oxygen/hydrogen/nitrogen storage structure exceeds a density of oxygen in atmospheric air.

7. The Faradaic solid-state energy storage device of claim 1, wherein the solid-state, ion conducting ceramic electrolyte has a crystal structure including vacancies that permit conduction or migration of ions through the crystal structure.

8. The Faradaic solid-state energy storage device of claim 1, wherein first redox-supporting metal, the second redox-supporting metal, or both the first redox-supporting metal and the second redox-supporting metal comprise one or more transition metals

9. The Faradaic solid-state energy storage device of claim 1, wherein the first redox-supporting metal, the second redox-supporting metal, or both the first redox-supporting metal and the second redox-supporting metal comprise a same metal.

10. The Faradaic solid-state energy storage device of claim 1, wherein the first redox-supporting metal and the second redox-supporting metal independently comprise Mn, Fe, Co, Ni, Cu, Mo, Tc, Ru, Rh, Pd, Ag, Au, W, Re, Os, Ir, or Pt.

11. The Faradaic solid-state energy storage device of claim 1, wherein the first redox-supporting metal and the second redox-supporting metal independently comprise Zn, V, Bi, Ti, La, Na, K, Rb, or Cs.

12. The Faradaic solid-state energy storage device of claim 1, wherein the Faradaic solid-state energy storage device is free of or does not include any liquids or gels.

13. The Faradaic solid-state energy storage device of claim 1, further comprising: one or more solid electrolyte and electrode bi-layers positioned in direct contact with a topmost electrode.

14. The Faradaic solid-state energy storage device of claim 1, wherein the first electrode, solid electrolyte, and second electrode are provided in an interdigitated configuration.

15. The Faradaic solid-state energy storage device of claim 1, wherein one or more components of the Faradaic solid-state energy storage device are independently fabricated using a controllable deposition method including one or more techniques selected from atomic layer deposition, magnetron sputtering, spin deposition, chemical vapor deposition, ultraviolet lithography, x-ray lithography, holographic lithography, laser ablation, or thermal evaporation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 provides a plot illustrating the relationship of ionic conductivity and temperature for a variety of solid-state electrolytes in the bulk.

[0045] FIG. 2A provides a schematic overview of charging a solid-state electrochemical energy storage device and FIG. 2B provides a schematic overview of discharging a solid-state electrochemical energy storage device.

[0046] FIG. 3 provides a schematic illustration of processes taking place within a solid-state electrochemical energy storage device.

[0047] FIG. 4A and FIG. 4B provide overviews of processes for making solid-state electrochemical energy storage devices.

[0048] FIG. 5 provides a schematic illustration of the crystal structure of a solid electrolyte, in accordance with some embodiments.

[0049] FIG. 6 provides a schematic illustration of the crystal structure of a solid electrolyte, in accordance with some embodiments.

[0050] FIG. 7 provides a schematic illustration of a system including electrochemical energy storage devices distributed throughout the circuit.

[0051] FIG. 8 provides a schematic illustration of a multilayer electrochemical energy storage device.

[0052] FIG. 9 provides a schematic cross-sectional illustration of an integrated circuit including multilayer electrochemical energy storage devices.

[0053] FIG. 10A and FIG. 10B provides schematic cross-sectional illustrations of an photovoltaic device including multilayer electrochemical energy storage devices.

DETAILED DESCRIPTION

[0054] The present application provides electrochemical energy storage devices and methods of making these devices. The devices are based on a unique architecture involving a pair of metal or metal oxide electrodes with a solid-state electrolyte (also referred to herein as a solid electrolyte) positioned in between the electrodes. For example, the metal or metal oxide electrodes may correspond to certain transition metals or metal oxides. For example, the solid-state electrolyte may correspond to certain ceramics capable of conducting ions through their crystal structure.

[0055] Advantageously, electrochemical energy storage device embodiments may be of an entirely solid-state construction. For example, all electrically active layers may also provide structural functions, such that the electrochemical energy storage device is not only entirely self-supporting but capable of reinforcing other elements to which it is conjoined.

[0056] FIG. 1 provides details of the ionic conductivity of a number of solid-state ceramic materials in the bulk. It will be appreciated that the conductivity of most of these materials only reaches appreciable values at temperatures exceeding about 300 C. At room temperature, the conductivity values of these ceramic materials are extremely small, making them very effective insulating materials.

[0057] The inventors have discovered, however, that thin films of certain solid-state ceramic materials, such as films having thickness of less than about 700 nm in some embodiments, may be engineered to exhibit high ionic conductivity at room temperature. This property allows the solid-state ceramics to function as electrolyte materials, and to exploit this engineered characteristic to permit transmission of ions. Such observation is entirely contrary to the electrical behavior of the solid-state ceramics in the bulk described above.

[0058] The conduction of ions through the solid-state electrolyte provides the basis for charge storage in some embodiments disclosed herein. FIG. 2A and FIG. 2B provides schematic overviews of charging (FIG. 2A) and discharging (FIG. 2B) of an example solid-state electrochemical charge storage device 200. Here, solid-state electrochemical charge storage device 200 includes a first electrode 210, an electrolyte 220, and a second electrode 230. As shown in FIG. 2A, during a charging operation, anions may be driven from the first electrode 210, through the electrolyte 220, to second electrode 230, while cations may be driven from the second electrode 230, through the electrolyte 220, to first electrode 210. As shown in FIG. 2B, during a discharging operation, cations may be driven from first electrode 210, through the electrolyte 220, to second electrode 230, while anions may be driven from the second electrode 230, through the electrolyte 220, to first electrode 210. It will be appreciated that in some embodiments only a single anionic species may correspond to the working ion, while in other embodiments only a single cationic species may correspond to the working ion. Embodiments are contemplated, however, where multiple ionic species are the working ions, such as multiple anionic species, multiple cationic species, or combinations of anionic species and cationic species. Such identities will be established by the specific chemistry utilized in a specific electrochemical energy storage device.

[0059] As depicted in FIG. 2A, during charging, electrons may be provided by a voltage source 240 to the first electrode 210. In embodiments where oxygen anions (O.sup.2) correspond to the working ion, the electrons may be used in a reduction reaction at the first electrode where oxygen anions may be released. The oxygen anions may be conducted through the solid electrolyte 220 to the second electrode 230, where they may be taken up by the second electrode and electrons may be released to the voltage source in an oxidation reaction. It will be appreciated that the energy required for the redox reactions, provided by the voltage source, may correspond, at least in part, to the energy electrochemically stored by the electrodes. Other energy storage mechanisms may also contribute to the energy stored by the system, including capacitive energy storage and/or inductive energy storage. Physical/chemical changes to the electrodes may be observed during charging. For example, in embodiments, the first electrode 210 will undergo loss of oxygen atoms and the second electrode 230 will undergo gain of oxygen atoms during charging.

[0060] FIG. 2B depicts discharging of the solid-state electrochemical energy storage device 200. The stored energy may be used during discharging by a load 250. In embodiments where oxygen anions (O.sup.2) correspond to the working ion, the electrons passed through the load 250 may be used in a reduction reaction at the second electrode where oxygen anions may be released. The oxygen anions may be conducted through the solid electrolyte 220 to the second electrode 230, where they may be taken up by the second electrode and electrons may be released to the voltage source in an oxidation reaction. It will be appreciated that the energy used by the load may correspond, at least in part, to energy electrochemically stored by the electrodes, but other energy storage mechanisms may also contribute, such as capacitive energy storage and/or inductive energy storage. Physical/chemical changes to the electrodes may also be observed during discharging. For example, in one embodiment, the first electrode 210 will undergo gain of oxygen atoms and the second electrode 230 will undergo loss of oxygen atoms during discharging.

[0061] FIG. 3 provides a schematic overview of charging and discharging of an electrochemical energy storage device where oxygen anions correspond to the working ion. The electrochemical energy storage device of FIG. 3 includes a first electrode 310, a solid electrolyte 320, and a second electrode 330. As illustrated first electrode 310 includes an oxide (M1O.sub.A) of a first metal, M1, and second electrode 330 includes an oxide (M2O.sub.B) of a second metal M2. It will be appreciated that the two metals may be the same or different and the levels of oxygen present in the different electrodes may also be the same or different.

[0062] Additionally, each electrode optionally includes a conductive supporting matrix, in which the metals are distributed. In some embodiments, the conductive supporting matrix may correspond to a carbonaceous material, such as carbon black or graphite, for example. Inclusion of a conductive supporting matrix may be useful for increasing a usable surface area of an electrode. In some embodiments, only a thin layer of the electrode may take part in electrochemical reactions, and so increasing the surface area of the electrode may allow for an increase in the overall amount of the electrode that may take part in the electrochemical reactions.

[0063] In the uncharged configuration, bound oxygen atoms may be included in the first electrode 310, the solid electrolyte 320, and the second electrode 330. During charging, however, some of the oxygen atoms may become unbound, such as due to the addition of electrons to the first electrode 310, where the oxygen atoms may become free ions, such as oxygen anions (O.sup.2). These oxygen anions may move from first electrode 310 into the solid electrolyte 320. Oxygen ions added to the solid electrolyte 320 may migrate through the solid electrolyte 320 and pass to the second electrode 330. In some circumstances, the oxygen anions added to the solid electrolyte 320 may become bound in the structure of the solid electrolyte 320 and a different oxygen atom may be released from the structure of the solid electrolyte 320 as an oxygen anion, creating an effective migration of the oxygen anion through the solid electrolyte. The oxygen ions that are added to the second electrode 330 may be incorporated into the structure of the second electrode 330.

[0064] In the charged configuration, the amounts of oxygen in the first electrode 310 and the second electrode 330 may be different from that in the uncharged configuration. As illustrated, after charging the first electrode 310 may have fewer oxygen atoms included in the structure, as compared to the structure of the first electrode 310 in the uncharged state. Similarly, as illustrated, after charging the second electrode 330 may have more oxygen atoms included in the structure, as compared to the structure of the first electrode 330 in the uncharged state. Thus, the first electrode 310 is illustrated as having a formula of M1O.sub.A+, while the second electrode is illustrated as having a formula M2O.sub.A.

[0065] During discharging, the opposite migration of oxygen occurs. Some of the oxygen atoms in the second electrode 330 may become unbound, such as due to the addition of electrons, and the unbound oxygen atoms may become oxygen anions. These oxygen anions may move from third electrode 330 into the solid electrolyte 320. Oxygen ions added to the solid electrolyte 320 may migrate through the solid electrolyte 320 and pass to the first electrode 310. The oxygen ions that are added to the first electrode 310 may be reincorporated into the structure of the first electrode 310

[0066] Advantageously, for certain embodiments, each electrode may be used as an anode or a cathode, depending on a charging configuration used when initially charging the electrochemical energy storage devices. For example, a first of the two electrodes may be connected to a negative terminal of a voltage source and a second of the two electrodes may be connected to a positive terminal of the voltage source during charging of the electrochemical energy storage device. After charging, the first electrode may function as an anode and the second electrode may function as the cathode. Upon discharging, the electrochemical energy storage device may be recharged in the opposite configuration, i.e., where the first electrode may be connected to the positive terminal of the voltage source and the second electrode may be connected to the negative terminal of the voltage source. After this charging cycle, the first electrode may function as the cathode and the second electrode may function as the anode.

[0067] This advantageous configuration may be achieved, in embodiments, by the charge storage mechanism and the chemistry involved. For example, in embodiments, the electrodes may comprise an oxide of the same metal, though levels of oxidation of each of the electrodes may be different and may change during charging and discharging. For example, in a specific embodiment, the electrodes may both comprise an iron oxide. Other examples are possible, including where different metals or metal oxides comprise the different electrodes.

[0068] As noted above, in some embodiments, only a small layer of the electrode proximal to the electrolyte may experience significant changes in oxidation state. For example, oxygen ions may be driven to or obtained from shallow depths in the electrodes, in some embodiments, such as a few nm. Accordingly, it may be desirable to form the electrodes as thin as practical so as not to include excess electrode material that is incapable of taking part in electrochemical reactions. Thus, in some embodiments, the electrode thickness may range from about 1 nm to about 10 nm, about 1 nm to about 15 nm, from about 1 nm to about 20 nm, about 1 nm to about 25 nm, from about 1 nm to about 30 nm, about 1 nm to about 35 nm, from about 1 nm to about 40 nm, about 1 nm to about 45 nm, from about 1 nm to about 50 nm, about 1 nm to about 55 nm, from about 1 nm to about 60 nm, about 1 nm to about 65 nm, from about 1 nm to about 70 nm, about 1 nm to about 75 nm. In embodiments, the electrochemical energy storage devices can operate using electrodes of any thickness, including electrodes thicker than about 75 nm, but as noted above, such thicknesses may not be the most efficient use of the electrode material and may contribute weight to the electrochemical energy storage device while not contributing to the energy storage capacity.

[0069] Advantageously, the disclosed electrochemical charge storage devices may operate under a variety of different voltage regimes. For example, an initial charging operation may correspond to a first reduction of metal in an anode such that oxygen anions are released by the anode to the solid electrolyte. The oxygen anions may take part in a reaction at the cathode where oxygen anions are adsorbed or otherwise taken up by the cathode to form metal oxides.

[0070] The cathode will thus be in a more oxidized state after charging. This oxidation may take on different levels as more and more oxygen is driven into the cathode during charging.

[0071] Use of certain metals in the cathode may benefit from this increased oxidation, as some metal species are capable of exhibiting different oxidation states. In the case of iron, for example, iron atoms exhibit oxidation states of +1, +2, +3, +4, +5, and +6, though the oxidation states of +2 and +3 may be the most common. If the electrode comprises Fe, a first charging stage may result in electrochemical creation in the cathode of FeO at a first charging voltage. As the FeO becomes saturated with oxygen, a second charging stage may occur, where the FeO becomes further oxidized to form Fe.sub.2O.sub.3. This process may continue, with the creation of Fe.sub.3O.sub.4, Fe.sub.5O.sub.6, Fe.sub.6O.sub.7, etc., each formed at increasing charging voltages. It will be appreciated that iron is used here for illustrative purposes and that other metals, such as Mn, Co, Ni, Cu, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir, and/or Pt, may be preferable for use as electrodes, though the principal of the operation of the energy storage device by creation of different oxides at increasing voltages may be applicable. Table 1 and Table 2 respectively summarize different half reactions that may take place during charging and discharging in some embodiments.

[0072] It will be appreciated that this increasing oxidation mechanism may allow the electrochemical energy storage devices, in embodiments, to be charged to high voltages, such as where the charged voltage corresponds to a voltage difference between a voltage of a first electrode and a voltage of a second electrode proximal where a single solid electrolyte is positioned between the first and second electrodes. Such charging voltages may be considerably higher than allowed by previous battery chemistries. For example, in embodiments, the electrochemical energy storage devices may be charged to a voltage between about 0 V and about 0.5 V, between about 0 V and about 1 V, between about 0 V and about 1.5 V, between about 0 V and about 2 V, between about 0 V and about 2.5 V, between about 0 V and about 3 V, between about 0 V and about 3.5 V, between about 0 V and about 4 V, between about 0 V and about 4.5 V, between about 0 V and about 5 V, between about 0 V and about 5.5 V, between about 0 V and about 6 V, between about 0 V and about 6.5 V, between about 0 V and about 7 V, between about 0 V and about 7.5 V, between about 0 V and about 8 V, between about 0 V and about 8.5 V, between about 0 V and about 9 V, between about 0 V and about 9.5 V, or between about 0 V and about 10 V. In some embodiments, the electrochemical energy storage devices may be charged to a voltage greater than about 5 V, greater than about 10 V, greater than about 15 V, or greater than about 20 V. It will be appreciated that, in some embodiments, as higher and higher voltages are encountered, an electrical discharge may occur between electrodes and through the solid electrolyte, resulting in loss of stored charge and potential damage to the devices.

TABLE-US-00001 TABLE 1 Overview of redox chemistry during charging Anode Half Reaction Cathode Half Reaction Stage 1 Charging M1O.sub.X + 2e.sup. .fwdarw. M1O.sub.X1 + O.sup.2 M2O.sub.Y + O.sup.2 .fwdarw. M2O.sub.Y+1 + 2e.sup. Overall Reaction: M1O.sub.X + M2O.sub.Y .fwdarw. M1O.sub.X1 + M2O.sub.Y+1 Stage 2 Charging M1O.sub.X1 + 2e.sup. .fwdarw. M1O.sub.X2 + O.sup.2 M2O.sub.Y+1 + O.sup.2 .fwdarw. M2O.sub.Y+2 + 2e.sup. Overall Reaction: M1O.sub.X1 + M1O.sub.Y+1 .fwdarw. M2O.sub.X2 + M2O.sub.Y+2 . . . Stage N Charging M1O.sub.X(N1) + 2e.sup. .fwdarw. M1O.sub.XN + M2O.sub.Y+(N1) + O.sup.2 .fwdarw. M2O.sub.Y+N + 2e.sup. O.sup.2 Overall Reaction: M1O.sub.X(N1) + M2O.sub.Y+(N1) .fwdarw. M1O.sub.XN + M2O.sub.Y+N

TABLE-US-00002 TABLE 2 Overview of redox chemistry during discharging Anode Half Reaction Cathode Half Reaction Stage 1 Discharging M1O.sub.X + O.sup.2 .fwdarw. M1O.sub.X+1 + 2e.sup. M2O.sub.Y + 2e.sup. .fwdarw. M2O.sub.Y1 + O.sup.2 Overall Reaction: M1O.sub.X + M2O.sub.Y .fwdarw. M1O.sub.X+1 + M2O.sub.Y1 Stage 2 Discharging M1O.sub.X+1 + O.sup.2 .fwdarw. M1O.sub.X+2 + 2e.sup. M2O.sub.Y1 + 2e.sup. .fwdarw. M2O.sub.Y2 + O.sup.2 Overall Reaction: M1O.sub.X+1 + M2O.sub.Y1 .fwdarw. M1O.sub.X+2 + M2O.sub.Y2 . . . Stage N Discharging M1O.sub.X+(N1) + O.sup.2 .fwdarw. M1O.sub.X+N + 2e.sup. M2O.sub.Y(N1) + 2e.sup. .fwdarw. M2O.sub.YN + O.sup.2 Overall Reaction: M1O.sub.X+(N1) + M2O.sub.Y(N1) .fwdarw. M1O.sub.X+N + M2O.sub.YN

[0073] Optionally, a solid-state electrochemical energy storage device is fabricated by means of atomic layer deposition, a form of chemical vapor deposition involving precursor chemicals and a two stage deposition process where the deposition chamber must be purged between processing stages. Atomic layer deposition (ALD) permits the formation of layers having a thickness of several nanometers or less and intricate surface features of similar dimensions. Advanced magnetron sputtering may also correspond to a useful deposition technique. Multiple deposition chambers may be useful for performing sequential deposition operations.

[0074] It will be appreciated that the above reference to ALD does not preclude the use of other nanofabrication techniques applicable to micro-circuitry either extant or in development, including CVD, thermal evaporation, epitaxial techniques, ultraviolet or X-ray lithography, holographic lithography, thermal evaporation, laser ablation or deposition.

[0075] In exemplary embodiments, individual sandwiches or cells comprise electrolytic layers alternating with metal or metal oxide electrodes. Actual charge storage occurs within the electrodes, such as by a process in which oxygen ions are adsorbed on or within the electrodes.

[0076] The benefits of the ALD and advanced magnetron sputtering fabrication technique useful with embodiments described herein are several. For example, they permit a high degree of consistency and repeatability and thus a low defect rate. In addition, because they support the formation of three dimensional, high radius features at very small scales, it permits the designer to increase interfacial surface area by many multiples over that afforded by featureless flat surfaces within the same volume. For example, surfaces having contoured topologies that provide increased surface area are useful with various embodiments.

[0077] In addition, cells of various embodiments may be built up incrementally, layer by layer. Capacity within a given footprint may be optionally controlled by varying the number of layers and the dimension of depth. The disclosed solid-state electrochemical energy storage devices further lend themselves to the construction of power distribution networks where the electrochemical energy storage devices are made modular and modules are interspersed with active circuitry or transducers. It will be appreciated that strategic depositions performed according to the ALD process or advanced magnetron sputtering can support such architectures. Optionally, the number of modules within such overall architectures may be arbitrarily small or large in number, such as 2 or 3 or as many as about 10 or more than about 10. Modules residing within such architectures may collectively assume the form of star and hub networks, redundant rings, or meshes, for example.

[0078] It will be appreciated that, in embodiments, the term gel refers to a non-fluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid.

[0079] As used herein, gels are expressly excluded from consideration as solid materials. Example electrolytes that comprise a gel include, but are not limited to, Nafion, LiPON, etc., which may be used, for example, in thin film lithium batteries. In some embodiments, electrolytes that comprise a gel cannot be prepared by high temperature deposition methods. It will be appreciated that solid-state electrolytes that comprise a gel cannot be prepared by atomic layer deposition. In addition, electrolytes that comprise a gel cannot withstand exposure to temperatures exceeding, for example 100 C., 200 C., 300 C., etc., without undergoing substantial damage to the electrolyte structure and/or without resulting in a substantial decrease in the ionic conductivity of the electrolyte structure.

[0080] FIG. 4A provides an overview of a process for making an electrochemical energy storage device, in accordance with some embodiments. Initially, a substrate 405 is subjected to a deposition process 408, such as an atomic layer deposition process, where material of a first electrode 410 is deposited onto substrate 405. Use of atomic layer deposition processes is advantageous for controlling the thickness of first electrode 410. Substrate 405 may correspond to any suitable substrate. As an example, substrate 405 may correspond to a portion of an integrated circuit, for example. Substrate 405 may alternatively correspond to a topmost layer of another electrochemical energy storage device.

[0081] Next, first electrode 410 is subjected to a second deposition process 413, in order to form a solid electrolyte 420 over the first electrode 410. For example, second deposition process 413 may correspond to an atomic layer deposition process to form a ceramic solid electrolyte. Use of atomic layer deposition processes is advantageous for controlling the thickness of solid electrolyte 420, as is advanced commercial sputtering.

[0082] Next, solid electrolyte 420 is subjected to a third deposition process 423, such as an atomic layer deposition process, where material of a second electrode 430 is deposited onto the solid electrolyte 420. Use of atomic layer deposition processes is advantageous for controlling the thickness of second electrode 430, as is advanced commercial sputtering.

[0083] Certain properties of the electrochemical energy storage systems described herein are strongly interrelated. For example, the highest level of performance may be achieved through system synergies in which the physical disposition of the active materials supports the most complete electrochemical reactions. As noted above, in some embodiments, higher performance may correspond to using electrodes that are particularly thin or that exhibit high surface area. In some embodiments, higher performance may be achieved by using both sides of one or more electrodes in an electrochemical energy storage device, which may be obtained using a stacked geometry in which a first surface of an electrode is positioned proximal to a first solid electrolyte and a second surface of the electrode is positioned proximal to a second solid electrolyte.

[0084] In some embodiments, an electrochemical energy storage device may thus comprise several or hundreds of cells, or more, stacked together in a multi-layer arrangement. In some embodiments, a multi-layer arrangement may comprise a series of stacked electrochemical energy storage cells in which the anode of one cell serves as the cathode of the cell stacked adjacent to it. In some embodiments, a multi-layer arrangement may comprise a plurality of stacked electrochemical energy storage cells in which the anode of one cell also serves as the anode of an adjacent cell and/or in which the cathode of one cell also serves as the cathode of an adjacent cell.

[0085] FIG. 4B provides an overview of a process for making a stacked electrochemical energy storage device, in accordance with some embodiments, and continues the process depicted in FIG. 4A. Second electrode 430 is subjected to a fourth deposition process 433, in order to form a second solid electrolyte 440 over the second electrode 430. For example, fourth deposition process 433 may correspond to an atomic layer deposition process to form a ceramic solid electrolyte. Use of atomic layer deposition processes is advantageous for controlling the thickness of second solid electrolyte 440.

[0086] Next, second solid electrolyte 440 is subjected to a fifth deposition process 443, such as an atomic layer deposition process, where material of a third electrode 450 is deposited onto second solid electrolyte 440. Use of atomic layer deposition processes is advantageous for controlling the thickness of third electrode 450.

[0087] It will be appreciated that additional electrolyte/electrode bilayers may be deposited over an uppermost electrode, similar to the processing depicted in FIG. 4B, in order to form stacked electrochemical energy storage devices of any desired thickness and number of layers.

[0088] In some embodiments, a solid electrolyte may exhibit a crystalline structure. The solid electrolyte may exhibit a variety of crystal forms, including single crystal and polycrystal. In embodiments where the solid electrolyte includes crystalline material, the solid electrolyte may take on different crystal forms, depending on the specific material configuration of the solid electrolyte. FIG. 5 provides a schematic illustration of a first example crystal structure 500 of a solid electrolyte. It will be appreciated that the crystal structure 500 illustrated may correspond to a ceria or zirconium crystal structure, which is provided here as an example only, and that other crystal structures are possible. For example, in embodiments, the solid electrolyte may comprise a perovskite ceramic, a ceramic having a perovskite structure, a zirconium ceramic, a ceria-gadolinia ceramic, an alumina ceramic, any variant of these, including any doped variant, and any combination of these.

[0089] In FIG. 5, various chemical elements make up the crystal structure 500. For example, a first atoms 505, such as metal atoms, may comprise a portion of the crystal structure 500, and second atoms 510, such as oxygen atoms, may comprise a portion of the crystal structure 500. Various defects may be included in the crystal structure 500, which may be naturally occurring or intentionally introduced. As illustrated, crystal structure 500 includes voids or crystallographic defects 515, which may correspond to vacancy defects, for example, where atoms of the crystal structure are missing. Voids and crystallographic defects 515 may be useful for allowing transmission of oxygen anions through the crystal structure 500, and provide for the ability of oxygen anions to efficiently migrate through the solid electrolyte. It will be appreciated that other crystal structure features beyond voids or crystallographic defects such as vacancy defects may also exist in the solid electrolyte, such as crystallographic defects including interstitial defects, line defects, planar defects, bulk defects, and lattice imperfections. An interstitial defect 520 is illustrated. Each of the voids or crystallographic defects may, in some embodiments, contribute to the ability of ions to efficiently migrate through a solid electrolyte.

[0090] FIG. 6 provides a schematic illustration of another crystal structure 600, which includes a first metal 605, oxygen atoms 610, and crystallographic defects 615. Here, crystallographic defects 615 may correspond to vacancy defects. The crystallographic defects 615 may be generated, for example, by introduction of one or more dopants 620 into the crystal structure 600. In some embodiments, the dopants 620 and crystallographic defects 615 may be introduced, for example, during the formation of the crystal structure, such as during an atomic layer deposition process. In some embodiments, the dopants 620 and crystallographic defects 615 may be introduced after the crystal structure 600 is formed, such as by an ion implantation process. Useful dopants include, but are not limited to, alkali metal dopants, alkaline earth dopants, group 3 dopants, lanthanide dopants, titanium oxide dopants, hydrogen dopants, silver dopants, and/or lead dopants.

[0091] In embodiments, when an oxygen anion is added to the crystal structure 600 at a crystallographic defect 615, the electronic configuration of the crystal structure may change, such as due to the extra electrons carried by the oxygen anion. This configuration may create an unstable structure, and so the oxygen atoms may rearrange to accommodate the extra material added to the crystal structure and in this way allow oxygen anions to migrate through the crystal structure.

[0092] It will be appreciated that, in some embodiments, the electrochemical energy storage devices described herein may comprise extremely small devices, as the electrodes and electrolyte may comprise layers having thicknesses as small as about 1 nm. For example, total thicknesses of a unit cell may be as small as about 3 nm, for example, or as large as about 1 m. Some unit cell embodiments may comprise larger thicknesses, however, and multi-cell devices may take on any suitable thickness, as the number of unit cells is virtually without limit. These small unit cell dimensions may provide for a number of the advantageous properties of the devices. For example, in embodiments, the devices may exhibit extremely large electrical energy densities when charged, such as greater than about 10 J/cm.sup.3, greater than about 50 J/cm.sup.3, greater than about 200 J/cm.sup.3, or greater than about 500 J/cm.sup.3. Although the amount of energy stored by a single cell may be small, the dimensionality of the cells may allow many hundreds or thousands or more cells to be included within a small volume, magnifying the overall energy storage capacity greatly.

[0093] Lateral dimensions for the devices, however may take on any suitable value, and may (at least) linearly contribute to the amount of energy stored by the devices. For example, in some embodiments, the lateral dimensions of the electrodes and the solid electrolyte may be as small as about 20 nm or less, and may be limited by the deposition abilities used during fabrication. Various masking and lithographic processes may be used, for example, to achieve lateral dimensions as small as about 10 nm. In other embodiments, the lateral dimensions may take on larger values, such as greater than 1 m, greater than 10 m, greater than 100 m, greater than 1 mm, greater than 1 cm, or greater than 10 cm. Again, the maximum lateral dimensions achievable may be limited by the deposition abilities used, but are virtually without limit.

[0094] One advantage of such miniaturized energy storage devices is that multiple individual devices may be attached to one another to form an energy distribution network. Energy distribution networks of this nature may be useful for providing power at the point of load, minimizing power transmission distances and associated resistive losses and heat generation. Energy distribution networks may also be useful for sequestering attached devices from fluctuating electrical loads engendered by other components. For example, when included in an integrated circuit, such as in combination with inductive coupling, an energy distribution network may protect circuits from electrical fluctuations generated by circuit blocks elsewhere on the wafer.

[0095] Another advantage is that backup power may be provided in the event of the failure of any one of the storage devices in the distribution network, and a portfolio of energy resources may be provided within the confines of a single system on a chip, for example. Networking of the devices in an energy distribution may optionally be achieved using one or more addressable switching transistors, which can be used to isolate individual blocks or electrochemical energy storage cells/stacks and/or to route current/voltage to components that have had a failure of their primary power source.

[0096] Optionally, the individual cells may in an energy distribution network be connected in series or in parallel and any combinations of series and parallel connections may be made. Such connections may be made highly configurable by the inclusion of switching transistors to set up and dismantle temporary circuit paths.

[0097] FIG. 7 provides a schematic overview of a system 700 including a variety of electrochemical energy storage devices 705, 710, 715. System 700 may correspond to a single integrated circuit configured as a system-on-chip, or may correspond to individual or integrated components, in any configuration. The energy storage devices 705, 710, 715 may be used individually as energy sources for one or more other components of system 700, but may also be used in an energy distribution network, as described above, to provide power to any one or more components. In such a configuration, a transistor network may be included, for example, to allow for individually switching the flow of electrical current from any individual energy storage device 705, 710, 715 to any individual component.

[0098] As illustrated, however, energy storage devices 705, 710, 715 are shown as separate energy storage devices, providing power to only one or a subset of components of system 700. For example, energy storage device 705 is illustrated as providing power to a central processing unit comprising four individual processing cores. Energy storage device 710 is illustrated as providing power to a memory unit, a network unit, and an input/output unit. Energy storage device 715 is illustrated as providing power to the input/output and a graphics processor. It will be appreciated that the electrical connection providing power from the energy storage devices to another component may be switchably achieved, such as by using one or more transistors, relays, or other controllable switching circuits.

[0099] FIG. 8 provides a schematic illustration of a multilayer electrochemical energy storage device 800. Here, alternating electrodes are connected in a parallel configuration, such that the device comprises a single parallelized energy storage device. For example, every other electrode is electrically connected on a first end, while the remaining electrodes are electrically connected on the opposite end. Other configurations are possible, including series configuration, combined series and parallel configuration, and electrical connections to the electrodes may be made at any suitable position. As illustrated, a first set of electrodes exhibit a first potential (V.sub.1), while a second set of the electrodes, interspersed between the first set of electrodes, exhibit a second potential (V.sub.2), such that a potential difference between the electrodes is V.sub.1-V.sub.2. Solid electrolytes are positioned between each adjacent electrode in FIG. 8.

[0100] FIG. 9 provides a cross-sectional schematic illustration of an integrated circuit 900 including electrochemical energy storage devices 905 and 910, positioned over a substrate 915. Each of the electrochemical energy storage devices 905 and 910 are illustrated as including multiple unit cells. A transistor 920 is included in the circuit 900, including source, drain, and gate elements. Various insulating/dielectric layers 925 are included, as well as conductive traces 930 between various layers and device components. It will be appreciated that the electrochemical energy storage devices may be distributed and/or networked throughout the integrated circuit as described above.

[0101] Inclusion of one or more electrochemical energy storage devices in an integrated circuit, as illustrated in FIG. 9, may be achieved, in embodiments, because the component materials and characteristics may be compatible with the semiconductor fabrication processes used to manufacture the integrated circuit. Further, the techniques used to make the electrochemical energy storage devices, such as atomic layer deposition, magnetron sputtering, masking, lithography, etc., may be already utilized in the fabrication of the semiconductor devices, so additional processing systems and techniques may not have to be developed.

[0102] FIG. 10A and FIG. 10B provide cross-sectional schematic illustrations of a photovoltaic cell 1000 integrated with an electrochemical energy storage device 1030. Photovoltaic cell 1000 may optionally comprise any suitable photovoltaic material that is compatible with electrochemical energy storage device 1030 and the fabrication processes for making electrochemical energy storage device 1030. For example, in the embodiments illustrated in FIGS. 10A and 10B, photovoltaic cell 1000 comprises a bottom electrode 1005, a p-type silicon layer 1010, an n-type silicon layer 1015 and a top electrode 1020. Electrochemical energy storage device 1030 comprises multiple layers of electrodes and electrolytes, for example similar to multilayer electrochemical energy storage device 800 described above. A first set of electrodes of electrochemical energy storage device 1030 is illustrated as in electrical communication with top electrode 1020 and a second set of electrodes of electrochemical energy storage device 1030 is illustrated as in electrical communication with bottom electrode 1005. A load 1025 is also illustrated as electrically connected between bottom electrode 1005 and top electrode 1020.

[0103] In FIG. 10A, the electrochemical energy storage device 1030 is positioned directly below and optionally in contact with bottom electrode 1005. Such a configuration may be desirable for example, to allow the first electrode of electrochemical energy storage device 1030 to be deposited directly on bottom electrode 1005 during the manufacturing process. Other examples are possible, such as where an interleaving material, such as an insulator, semiconductor, or other conducting material is positioned between bottom electrode 1005 and electrochemical energy storage device 1030. Additionally, different physical arrangements of the photovoltaic cell 1000 and electrochemical energy storage device 1030 are contemplated. As an example, in FIG. 10B, the photovoltaic cell 1000 and electrochemical energy storage device 1030 are positioned side-by-side. Such a configuration may be desirable to allow electrochemical energy storage device 1030 to be positioned within the spaces between adjacent photovoltaic cells, for example. Further arrangements are contemplated, including where the electrochemical energy storage device 1030 and photovoltaic cell 1000 are independent components and where the electrochemical energy storage device 1030 is used as a standalone energy storage backup module.

[0104] It will be appreciated that providing electrochemical energy storage devices in electrical communication with photovoltaic cells may be useful, in embodiments, for modulating the output of the photovoltaic cell and minimizing variability in cell output. Additionally, when exposed to light, the excess electrical energy generated by the photovoltaic cell may be used to charge the electrochemical energy storage device to store the excess energy. The stored energy may then be provided by the electrochemical energy storage device as voltage output during non-peak times, such as during the night or on cloudy days, for example. Including the electrochemical energy storage devices directly on the same structure as the electrochemical cell is further advantageous for simplifying construction, integration, shipping, etc. Additionally, the use of the electrochemical energy storage devices described herein may be beneficial, for example, as the electrochemical energy storage devices may have large power densities and can receive and provide large current densities as needed, without damaging the electrochemical energy storage devices or degrading their storage capacities. Further, the electrochemical energy storage devices may exhibit large cycle lives without resulting in component degradation or capacity loss, making them beneficial for use in these photovoltaic applications as well as other energy storage applications.

[0105] Additional related description may be found in U.S. patent application Ser. No. 13/536,029, filed on Jun. 28, 2012, and U.S. Provisional Application 61/502,797, filed on Jun. 29, 2011, which are hereby incorporated by reference in their entireties.

[0106] The present invention may be further understood by reference to the following non-limiting examples.

[0107] A. Architecture

[0108] Like batteries, the solid-state electrochemical energy storage devices and systems described herein make use of conduction of ions through an electrolyte. For example, the disclosed electrochemical energy storage devices and make use of reversible electrochemical redox reactions that take place at the electrodes with ions that pass through the electrolyte. In the disclosed electrochemical energy storage devices, these reversible redox reactions can occur without limit, and permit full discharge without damage. In some embodiments, an electrochemical energy storage device comprises a simple construction, where two electrodes are separated by a solid-state electrolyte.

[0109] B. Temperature

[0110] Unlike battery chemistries such as lead/acid and lithium-ion, electrochemical energy storage devices described herein are not restricted by temperature and remain capable of operating within a wide range of temperatures, such as, for example between about 100 C. and about 700 C., although some embodiments may exhibit a certain amount of temperature sensitivity. It will be appreciated that the electrochemical energy storage devices of some embodiments can withstand this temperature range due to the use of ceramic electrolytes instead of liquid, gel, or polymer electrolytes. It will be appreciated that the ceramic materials used as electrolytes herein are not commonly seen to represent electrolytes at ambient temperatures when in bulk, but rather as dielectrics through which neither electrons nor positive ions can move.

[0111] C. Electrolyte Materials & Scale

[0112] In some embodiments, the disclosed electrochemical energy storage devices use specially doped and extremely thin ceramic films, where the ceramic presents a crystalline lattice with oxygen vacancies through which oxygen ions can flow to interface with the electrodes. The length scales used to achieve the conductivity of oxygen ions vary somewhat from material to material. In some embodiments, the thickness of the ceramic solid-state electrolyte is between about 30 nm and about 100 nm. If the electrolyte exceeds its limits, it reverts to a dielectric rather than an electrolyte, and thus will not function for energy storage, and so in no case does the thickness equal or exceed 1 m. Conversely, if the electrolyte is too thin, opportunities exist for catastrophic failure by shorting out, such as due to surface roughage or electrostatic discharge from one electrode to the other through the electrolyte.

[0113] D. Doping

[0114] Basic ceramic materials such as alumina and zirconium in pure form may present monolithic and nonconductive surfaces to the electrodes if used in an electrochemical energy storage device. In order to present a lattice that contains the oxygen vacancies useful for ionic conductivity, some pure ceramic materials may require doping. The doping may, for example, create lattice imperfections, crystallographic defects, or ion carrier sites that the extremely small thickness scale can exploit. In some cases, this amounts to creating an alloy, such as where the dopant is as much as 50% of the material. Na+ doped alumina (B-alumina), is an example.

[0115] E. Energy Density & Charge

[0116] Due to the small amounts of material incorporated into the electrochemical energy storage devices at the scales used in various embodiments, only small amounts of charge will be stored, even with a relatively high energy density. In certain embodiments, however, such as integrated into electronic circuitry in semiconductor chip fabrication, this small amount of charge can provide power at the point of load on an instantaneous basis. In addition, inductive coupling from a nearby source can be used in some embodiments to continuously recharge the electrochemical energy storage devices.

[0117] In more general applications, such as replacement batteries for a consumer electronic device, such as a smart phone or laptop battery, embodiments may require multiple layers or cells to provide the needed current. For example, multiple layers of electrochemical energy storage devices may be constructed on top of one another to achieve larger amounts of charge storage. Given the small thicknesses, many thousands of layers of electrodes and solid-state electrolytes can, in embodiments, be constructed within common battery pack sizes, such as on the order of about 1 cm to about 10 cm. Techniques, such as advanced commercial magnetron sputtering, atomic layer deposition, and other nanoscale deposition techniques allow economical fabrication of such multi-celled devices.

[0118] In a specific embodiment, a combination of two electrodes and one electrolyte layer constitutes a single cell. Optionally, the electrochemical energy storage device may consist of a single cell or less than about 50 cells, such as in a continuous stacking configuration. The electrochemical energy storage device may optionally be reduced to a depth that is commensurate with complete integration into a wafer based microcircuit where the electrochemical energy storage device shares the same wafer as the active circuitry.

[0119] F. Field Specifics

[0120] In some embodiments, multi-celled electrochemical energy storage devices comprising multiple layers of electrodes in between electrolytes may deliver even more energy storage/unit size than lithium-ion can attain. In embodiments, replacement devices can use drop-in replacement form factors, where the electrochemical energy storage device may measure a few microns to a few mm in thickness or larger, with the remaining form consisting of a case enabling direct replacement in existing devices. Using inductive charging, some embodiments may store enough charge that electronic devices would never need direct, wired, charging beyond the first time.

[0121] G. Chip Integration

[0122] As described in more detail below, many batteries identified as solid-state batteries are not truly solid-state. For example, the electrolyte in these batteries typically comprises a gel or a powder or a colloidal suspension. It will be appreciated that these materials cannot withstand large temperature variations used in common semiconductor fabrication process, and thus are incompatible with integrated circuits, for example. Gel electrolytes behave analogously to aqueous electrolytes where crystallinity is not present and ions are not bound but are free to pass across the fluid or semifluid medium, impelled by electrical forces. Other devices may have a crystalline electrolyte, but use a liquid electrode.

[0123] In contrast, the electrochemical energy storage devices described herein make use of rigid crystalline lattice structures. For example, defects may be deliberately and artfully introduced to the crystal lattice in order to provide transient pathways for the movement of ions. These pathways may be engineered and organized by various techniques involving the introduction of chemical dopants or by the imposition of strain or by the application of outside forces, either transient or persisting. Such forces tend to deform the lattice structure such that paths for ionic migration become present, for example. These design strategies executed on the molecular and supramolecular level may be used to regulate the volume of ionic flow, and the process may involve beneficial nonlinearities with respect to ionic volume that may be exploited.

[0124] H. Electrochemical Energy Storage Device Architecture

[0125] In a solid electrolyte, such as a thin ceria stabilized zirconia layer situated between two metal or metal oxide electrodes, oxygen ions may shuttle between the electrodes bearing opposing charges. Without wishing to be bound by any theory, the inventors believe that the positive ions move by traversing through the interstices of a fairly rigid crystalline lattice of extremely limited depth (thin-film), but rich in oxygen vacancies, and it is the oxygen vacancies that permit the free movement of positive ions. A trade-off exists between high ionic conductivity and multiple-layer requirements. The movement of ions through the solid-state electrolyte may also be further tuned by the imposition of external stresses, such as those caused by a bi- or multi-layer electrolyte, that deform the lattice and widen the passageways for ionic movement. In either stressed or unstressed cases, the ions participating in electrochemical storage act as replacements for atoms distributed within the electrolyte, and these ions hop from site to site.

[0126] Temperature Range and Integrated Circuit Integration

[0127] The completely solid, gel-free electrochemical energy storage devices disclosed herein are capable of withstanding very large temperature variations. For example, some embodiments may be useful between about 100 C. and about 800 C. In addition, the devices, due to the lack of liquid or gel materials, may be rugged and capable of integration into active semiconductor circuitry. In terms of size reduction, this can reduce, for example, the size of an integrated circuit, such as a central processing unit, by about 70%, due to the elimination of pin connectors and attendant circuitry, in some embodiments, which may be accompanied by a corresponding reduction of heat generation. In addition, the electrochemical energy storage devices, such as when coupled inductively, permit redundant instantaneous power at point of load.

[0128] Additionally, the electrochemical energy storage can take the form, in some embodiments, of a network of cells. Printed conductive traces may convey the stored energy to its destination and switching matrices may allow for powering any of the circuit components by any of the cells, in any combination. For example, some cells may power logic circuits, while other cells may power mixed signal circuits.

[0129] Switching between and among energy storage cells may take the form of star and hub architectures, redundant rings, or mesh networks with or without intelligence. Such architectures may serve to support power at the point of load design strategies or islanding of defective cells or adjustments in voltage and current by making cell to cell connection switchable.

[0130] It will be appreciated that, because of the flexibility afforded by the materials and architectures used in the electrochemical energy storage devices, an array of cells may be planar, three dimensional, or may comprise a succession of stacked planes, for example. In addition, planar inductors may, optionally, be incorporated along with the storage cells such that islands of energy storage may be inductively coupled with one another, reducing the number of conductive pathways and the mass and volume of an integrated circuit incorporating energy storage.

[0131] In some embodiments, the materials that comprise an electrochemical energy storage device may be rendered rigid and unyielding or flexible, depending upon the thickness of the material and the presence or absence of porosity within it. Energy storage may thus be incorporated in flexible thin films such as displays or thin film photovoltaic cells or in energy harvesting devices dependent upon the movement of membranes to generate electrical power, for example. In addition, caseless batteries may constructed in which the electrodes and electrolytes provide structural integrity to the batteries. In some embodiments, the electrochemical energy storage devices may also be integrated with planar energy harvesting radio frequency antennas or with generator and actuator MEMS elements, so that microelectromechanical energy storage, power electronics, and signal processing may be incorporated into a single wafer with a high degree of synergy and integration among the separate elements.

[0132] J. Gel-Free

[0133] Embodiments of the present invention relate to solid-state electrochemical energy storage devices and methods of making solid-state electrochemical energy storage device in which components of the devices are truly solid-state (i.e., they do not comprise a gel). The solid-state battery nomenclature is not new but it has always been misleading in the prior art. Many solid-state batteries utilize either gels or in some case powders for the electrolyte layers and never homogenous, consolidated solid materials that can integrate into semiconductor chips directly, for example. Gel materials prohibit both incorporation within VLSI/ULSI chips, and restrict temperature ranges to approximately ambient.

[0134] True solid-state electrolyte layers have been utilized in solid oxide fuel cells. When used in a solid oxide fuel cell, solid-state electrolyte layers normally conduct ions at a practical rate only at extremely elevated temperature, such as exceeding 600 C. However, the solid electrolyte layers described herein exhibit high ionic conductivity, which may approximate or exceed that of liquid or gel electrolytes, even at ambient or near ambient temperatures. The ambient temperature ionic conduction exploited herein also offers a further advantage of preserving high electrical resistance and dielectric strength, which are commonly sacrificed in solid-state supertonic conductors at high temperatures.

[0135] In exemplary embodiments, gaseous oxygen (O.sub.2) and/or oxygen ions (e.g., O.sup.+ or O.sup.2) are responsible for charge transport and formation of the electrochemical bonds (redox) by which electrical charge is stored and conserved. A number of transport mechanisms may invoke the passage of oxygen ions through the crystalline structure of the solid electrolyte layer. For example, oxygen vacancies within the crystal lattice may be an important source of ion transport.

[0136] It will be appreciated that oxygen vacancies may represent defects, and may be present when the ceramic has been doped with another chemical which results in a departure from the regularity of the crystalline structure present in the pure ceramic. Such defects may be analogous to holes in P type semiconductors, for example. It may be advantageous if the ceramic and/or the dopant contains the element that will be ionized, and some of that element may be dislodged from the crystal structure. Additional ions may be drawn from the anode or the cathode, or from the atmospheric air if oxygen ions participate in the electrochemical reactions.

[0137] The ionic conduction modes in ceramic electrolytes are very different from those present in aqueous or polymer electrolytes where no crystalline lattice is present and where ions are released by means of electrolysis or simply pass through the fluid medium from the electrodes. In true solid electrolytes, as opposed to gels, both chemistry and mechanical forces play a role in ionic migration as does the phase of the crystalline structure, i.e. whether it is amorphous or cubic.

[0138] The addition of dopants alone may not provide a high degree of ionic conductivity under ordinary circumstances, and some solid electrolyte materials will not conduct ions at all at macro scale thicknesses and at ambient temperatures, for example. In some embodiments, violent flexures and dislocations of the lattice structure are required to support interstitial movements of ions.

[0139] Such flexures may take the form of phonons, that is, thermally induced periodic oscillations at audio frequencies or more enduring surface strains imposed by the fabrication process or by the presence of micro-actuators such as piezoelectric elements that exert shear forces. Either mechanism may provide spaces through which positive ions may be transported.

[0140] It will be appreciated that zirconia and other ceramics may be suitable as solid electrolytes. In some embodiments, useful ceramics include doped ceramics. For example, calcium, magnesium, yttrium, aluminum, and ceria stabilized zirconias may also be useful solid electrolytes.

[0141] K. Fabrication

[0142] In embodiments, a solid-state electrolyte layer, which may be a consolidated structural layer, offers many performance advantages. For example, the structural integrity conferred by a solid electrolyte combined with solid electrodes may eliminate the need for an external case, in some embodiments. For example, in one embodiment, the electrochemical energy storage device can be naked, i.e., not associated with any other structural materials. In some embodiments, the electrochemical energy storage device may be built up as an integral circuit element within a larger microcircuit with wafer fabrication techniques. These examples may not possible with conventional battery technologies. The solid-state electrochemical cells described herein also may possess inherent physical robustness and a high immunity to shock, vibration, and temperature extremes. In addition, the solid-state electrochemical energy storage devices described herein are highly scalable such that they may be closely coupled to such entities as MEMS devices and microfluidic systems.

[0143] In exemplary embodiments, a solid-state electrochemical energy storage device becomes, in essence, another circuit element in an integrated circuit and facilitates the realization of optimal circuit paths and grounding schemes because it lends itself to strategic placement within the overall circuit. In some embodiments, this can eliminate as much as 70% of the circuitry (e.g., the portion served by power pins) in existing VLSI/ULSI chips, greatly reducing size and heat generation.

[0144] L. Point of Load Power and Inductive Charging

[0145] Solid-state construction has implications that are as potentially as revolutionary with respect to electrical charge storage as they have been to active circuitry when transistors largely replaced vacuum tubes (thermionic valves) more than a half-century ago. For example, just as transistors invoke different mechanisms for controlling the passage of current through a circuit and realization of voltage and current gain, solid-state electrochemical energy storage devices may utilize unique mechanisms for storing and releasing electrical charge at the point of load. Also importantly, solid-state electrochemical energy storage devices exhibit an ability to charge rapidly by inductive coupling (rapidity due to the ability to resist overcharging), permitting wireless charging and potentially eliminating need for nearby power sources entirely.

[0146] It should be understood that, in various embodiments, the solid-state electrochemical energy storage devices described herein categorically reference redox reactions. In this text, oxygen may stand for any of those. In exemplary embodiments, charge storage may be achieved through truly reversible redox reactions occurring adsorptively some little distance into the depths of the electrode layer. That depth may be in the angstroms or into the low nanometers, and, to be more specific, less than 10 nanometers. Oxygen ions may form the basis of the electrochemical reactions.

[0147] Without wishing to be bound by any theory, oxygen ions may enter and leave the electrodes during the charge/discharge cycles, and are adsorbed to depths of about 0.2 nm to about 10 nm, such as about 0.5 nm, about 1 nm, about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, or any combination of ranges between any of these specific values. In exemplary embodiments, the electrodes themselves range in overall depth/thickness from between about 7 nm to about 50 nm.

[0148] Uniquely, multiple redox reactions may be invoked, and successively higher oxides may be formed at successively higher input voltages. For example, in some embodiments, exemplary electrode materials comprise, consist of, or consist essentially of elemental metals or metal oxides capable of forming a sequence of oxides of progressively greater molecular weight. These may include, for example, monoxides, dioxides, trioxides, tetroxides, pentoxides, hexoxides, heptoxides, and so on. In some embodiments, hydrides or nitrides may be substituted for oxides. Work functions for candidate materials may, for example, range between about 4 electron volts and about 5 electron volts and may also include values between these limits.

[0149] In exemplary embodiments, electrolyte layers comprise ceramic compositions supporting expeditious transfer of positive oxygen ions from the anode to the cathode or from the cathode to the anode at ambient or near ambient temperatures. Transfer rates optionally range from about 10 to about 50 Siemens per centimeter, and these rates may be greater in architectures where the electrolyte thickness is less than about 58 nm. Useful ceramic compositions include a number of perovskites and perovskite-related oxides, as well as many zirconium ceramics, such as zirconia-scandia, Zr.sub.1-xSc.sub.xO.sub.2- and the cheaper zirconium stabilized by yttria, and ceria-gadolinia, Ce.sub.1-xGd.sub.xO.sub.2-(CGO), alumina and (3-alumina formulated with a number of dopants such as ceramic forms of Na.sup.+, K.sup.+, Li.sup.+, Ag.sup.+, Pb.sub.2.sup.+, Sr.sub.2.sup.+ or Ba.sub.2, TiO, TiO.sub.2, Ti.sub.2O.sub.3, etc.

[0150] M. Evacuated Electrolyte

[0151] Alternatively, the electrolyte layer may be largely evacuated, and the resulting cavity may be supported with minute spacers measuring between about 20 nm and about 100 nm, for example. In such instances, the cavity is optionally filled with gaseous oxygen (or hydrogen or nitrogen) at a pressure of about 0.1 bar, or about 0.2 bar or about 0.3 bar, or at fractional or intermediate values or ranges between these stated numbers.

[0152] In one embodiment, the gas may, for example, be ionized by a pair of lateral electrodes that impose a transient high voltage on the gas, such as a voltage that imparts an electric field of sufficient strength to ionize the gas.

[0153] N. Enhanced Ionic Conductivity Dependencies

[0154] Thin-film scale and temperatures. Invoking high ionic conductivity for purposes of fabricating electrochemical energy storage devices via thin-film deposition of the solid-state electrolytes may involve two aspects. The first, thickness of the film, may dominate at all enhanced ionic conductivity temperatures. Temperature itself plays a significant role, especially at thicker (but still thin) films.

[0155] Enhanced ionic conductivity in the sense of orders of magnitude greater than bulk ionic conduction for the above mentioned solid-state electrolytes is exhibited below a particular thickness, which may vary from material to material. As an example, the enhancement for electrolytes in the zirconium family begins at below about 700 nm. Thicker than that, bulk material characteristics dominate and the well-known Arrhenius formula apply. In smaller thickness electrolytes, the enhanced ionic migration is observed and embodiments described herein may make use of this advantageous property.

[0156] Temperature-dependent enhanced ionic conductivity is observed, in embodiments, when the interface conductance is greater than that of the bulkthat is, thinner than a threshold of about 700 nm. Invoking ambient temperature performance requires films with acceptable ranges, for example, lower than about 62 nm, in some embodiments. The range from 30 nm to 1 nm may provide exceptional performance, with 1 nm providing negligible resistance to ionic flow while still continuing electron holdoff.

[0157] Strained interfaces. Another technique for invoking enhanced ionic migration involves a strained membrane or film. This may be achieved via deposition of heterogeneous electrolyte materials in sandwiched form, such as perovskites/zirconium compounds/perovskites, or the reverse order. Films of substantially less than 1 m may be useful for achieving the enhanced ionic migration in this way.

[0158] Advantageous aspects of the described electrochemical energy storage devices include, but are not limited to: [0159] A true, gel-free, solid-state electrochemical energy storage device with solid metallic or metal oxide electrodes and solid electrolyte layers having structural as well as electrical properties. The electrolyte layers consist of glass or ceramic compositions capable of supporting massive ionic migrations at the dimensions specified, and at ambient or near ambient temperature. [0160] Bi-layer electrodes capable of forming oxides and successions of higher oxides in the presence of an electrical charge. [0161] An elementary unit consisting of a single cell comprised of two electrodes and an electrolyte layer all of solid, consolidated construction. [0162] A structural electrochemical energy storage device that is self-supporting and requires no external case. [0163] Methods of construction such as atomic layer deposition and advanced commercial sputtering that permit full integration of storage into integrated circuits. [0164] An elementary unit consisting of two electrodes separated by spacers or an open framework which is constructed on the nano-scale and affords a volume for containing gaseous oxygen as a source of ions. [0165] A means of ionizing the confined oxygen. [0166] A cell thickness of less than about 200 nanometers and as little as about 30 nanometers and any intermediate value. [0167] An electrode thickness of less than about 50 nanometers and more than about 5 nanometers. [0168] An electrolyte layer thickness of less than about 150 nanometers and no less than about 20 nanometers. [0169] A multi-layer construction ranging from 2 cells up to thousands of cells and any number in between. [0170] A multi-layer construction having any combination of series and parallel connections between and among cells. [0171] A modular design incorporating dispersed energy storage units. [0172] A switching network for addressing dispersed energy storage units. [0173] A capability of undergoing full discharge without incurring damage or degradation. [0174] A formula that enables selection of appropriate electrode materials based on a variety of factors including work function, oxidation number, performance under various temperatures, and availability. [0175] A formula that enables the selection of appropriate solid electrolyte materials based on factors including atomic voids and/or band gaps and membrane stress that permit oxygen ion migration through the electrolyte, and performance under various temperatures.

[0176] It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.