THREE-DIMENSIONAL BATTERY HAVING CURRENT-REDUCING DEVICES CORRESPONDING TO ELECTRODES

Abstract

Various three-dimensional battery structures are disclosed, in certain embodiments comprising a battery enclosure and a first plurality of electrodes within the enclosure. The first plurality of electrodes includes a plurality of cathodes and a plurality of anodes. The first plurality of electrodes includes a second plurality of electrodes selected from the first plurality of electrodes. The three-dimensional battery includes a first structural layer within the battery enclosure. Each of the second plurality of electrodes protrudes from the first structural layer. The three-dimensional battery includes a plurality of electrical current-reducing devices within the enclosure. Each of the second plurality of electrodes is coupled to one of the plurality of current-reducing devices.

Claims

1. A three-dimensional battery, comprising: a battery enclosure; a first plurality of electrodes within the enclosure, the first plurality of electrodes including a plurality of cathodes and a plurality of anodes, the first plurality of electrodes including a second plurality of electrodes selected from the first plurality of electrodes; a first structural layer within the battery enclosure, each of the second plurality of electrodes protruding from the first structural layer; and a plurality of electrical current-reducing devices within the enclosure; wherein each of the second plurality of electrodes is coupled to one of the plurality of current-reducing devices.

2. The three-dimensional battery of claim 1 wherein the plurality of current-reducing devices comprises a plurality of regions of a PTC layer including positive-temperature-coefficient (PTC) material that is in contact with each of the second plurality of electrodes.

3. The three-dimensional battery of claim 2 wherein the PTC material is a conductive-polymer PTC material.

4. The three-dimensional battery of claim 3 wherein the PTC material comprises polyethylene including graphite particles.

5. The three-dimensional battery of claim 2 wherein the PTC material comprises barium titanate.

6. The three-dimensional battery of claim 1 wherein the plurality of current-reducing devices comprises a plurality of current collectors that include positive-temperature-coefficient (PTC) material, each of the plurality of current collectors being in contact with a respective one of the second plurality of electrodes.

7. The three-dimensional battery of claim 6 wherein the PTC material is a conductive-polymer PTC material.

8. The three-dimensional battery of claim 7 wherein the PTC material comprises polyethylene including graphite particles.

9. The three-dimensional battery of claim 6 wherein the PTC material comprises barium titanate.

10. The three-dimensional battery of claim 1 wherein the plurality of current-reducing devices comprises a plurality of solid state switches.

11. The three-dimensional battery of claim 1 wherein the plurality of current-reducing devices comprises a plurality of fuses.

12. The three-dimensional battery of claim 1 wherein the first plurality of electrodes comprises lithium ion insertion electrodes.

13. The three-dimensional battery of claim 6 wherein the first plurality of electrodes comprises a material selected from the group consisting of LiCoO.sub.2, Li(Ni.sub.xCo.sub.yAl.sub.z)O.sub.2, LiFePO.sub.4, and Li.sub.2MnO.sub.4.

14. The three-dimensional battery of claim 1 wherein the first plurality of electrodes comprises an interdigitated array of electrodes.

15. The three-dimensional battery of claim 1 wherein the first plurality of electrodes comprises a plurality of fins protruding at least 50 microns from the first structural layer.

16. The three-dimensional battery of claim 1 wherein the second plurality of electrodes includes fewer electrodes than the first plurality of electrodes.

17. The three-dimensional battery of claim 16 wherein the second plurality of electrodes includes the plurality of anodes but not the plurality of cathodes.

18. The three-dimensional battery of claim 16 wherein the second plurality of electrodes includes the plurality of cathodes but not the plurality of anodes.

19. The three-dimensional battery of claim 16 further comprising a second structural layer within the battery enclosure, wherein the first plurality of electrodes further includes a third plurality of electrodes selected from the first plurality of electrodes, each of the third plurality of electrodes protruding from the second structural layer.

20. The three-dimensional battery of claim 19 wherein the third plurality of electrodes includes the plurality of anodes but not the plurality of cathodes.

21. The three-dimensional battery of claim 19 wherein the third plurality of electrodes includes the plurality of cathodes but not the plurality of anodes.

22. The three-dimensional battery of claim 1 wherein the second plurality of electrodes is the same as the first plurality of electrodes.

23. The three-dimensional battery of claim 1 wherein each of the second plurality of electrodes comprises a protrusion that protrudes from the first structural layer and has an electrically conductive outer surface, and an electrode layer on the conductive outer surface.

24. The three-dimensional battery of claim 23 wherein the protrusion comprises a non-active backbone structure that protrudes from the first structural layer, and an electrically conductive layer on the non-active backbone layer.

25. A three-dimensional battery, comprising: a structural layer; a plurality of electrodes each protruding from the structural layer; and means for substantially reducing an electrical current through one of the plurality of electrodes without substantially reducing an electrical current through another of the plurality of electrodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic illustration of a cross section of one example of a three-dimensional lithium-ion battery that has been proposed in the literature.

[0012] FIG. 2A-2D are schematic illustrations of some three-dimensional energy storage system architectures that may be used with an embodiment of the present invention.

[0013] FIG. 3 is a cross-sectional schematic representation of a three-dimensional battery where a current collector also functions to dissipate heat, according to an embodiment of the invention.

[0014] FIG. 4 is a schematic representation of the use of a PTC material integrated into an interdigitated fin design for a three-dimensional battery, according to an embodiment of the invention.

[0015] FIG. 5 is a schematic representation of the use of a PTC material integrated into an interdigitated pillar design for a three-dimensional battery with a top-side electrical connection, according to an embodiment of the invention.

[0016] FIG. 6 is a schematic representation of the use of a PTC material integrated into a three-dimensional battery in an individual electrode unit level, according to an embodiment of the invention.

DETAILED DESCRIPTION

[0017] Existing energy storage devices, such as batteries, fuel cells, and electrochemical capacitors, typically have two-dimensional laminar architectures (e.g., planar or spiral-wound laminates) with a surface area of each laminate being roughly equal to its geometrical footprint (ignoring porosity and surface roughness). A three-dimensional energy storage device can be one in which an anode, a cathode, and/or a separator are non-laminar in nature. For example, if electrodes protrude sufficiently from a backplane to form a non-laminar active battery component, then the surface area for such a non-laminar component may be greater than twice the geometrical footprint of its backplane. In some instances, given mutually orthogonal X,Y,Z directions, a separation between two constant-Z backplanes should be at least greater than a spacing between electrodes in an X-Y plane, divided by the square root of two.

[0018] Some examples of three-dimensional architectures that are capable of use with certain embodiments of the present invention, and that have cathodes and anodes protruding from the same backplane, are shown in FIG. 2. FIG. 2A shows a three-dimensional assembly with cathodes and anodes in the shape of pillars, FIG. 2B shows a three-dimensional assembly with cathodes and anodes in the shape of plates, FIG. 2C shows a three-dimensional assembly with cathodes and anodes in the shape of concentric circles, and FIG. 2D shows a three-dimensional assembly with cathodes and anodes in the shape of waves. Other configurations, such as honeycomb structures and spirals might also be used with certain embodiments of the present invention. In FIG. 2, cathodes 20 and anodes 21 protrude from the same backplane and are alternating in a periodic fashion. However, in other embodiments the cathodes 20 may protrude from a different backplane than anodes 21.

[0019] Described herein is the use of safety mechanisms for reducing temperature related reliability issues in three-dimensional energy storage systems and devices. Safety mechanisms according to certain embodiments of the present invention can be incorporated into a three-dimensional battery (e.g., a three-dimensional rechargeable lithium-ion battery), such that the safety mechanisms are internal to the battery. However, in conjunction with the disclosed internal safety mechanisms, an external protection mechanism (external thermal fuse, external circuit breaker) may also be used with a three-dimensional architecture. A shutdown separator may also be used for providing internal thermal protection.

[0020] The ability to reduce operating temperature by having a more thermally conductive electrode/current collector interface may be one mechanism for increasing stability. For example, a current collector and/or backbone structure for a three-dimensional battery may act as a heat sink, which in turn can reduce the probability of thermal runaway in case of a short-circuit (short) or other high temperature event. FIG. 3 provides an example of a three-dimensional battery with components that also serve as heat sinks, among other things. In this example, the battery is constructed with a non-active backbone structure 30 on top of which an electrically conductive current collector 32 is deposited. A cathode 31 and an anode 33 are deposited using any of various methods on top of the current collector 32. The whole assembly can be submerged into a separator matrix to form the battery.

[0021] The battery of FIG. 3 has better heat sink characteristics, in part because of the availability of a higher surface area of the highly conductive current collector 32 relative to cathode or anode materials. In a two-dimensional design, a current collector may not transfer much heat since a transport of heat from an electrode/separator interface (which is where many high-temperature reactions occur) to the current collector can be significantly slower due to large transport distances through a mildly conducting active material porous matrix. By contrast, in certain three-dimensional arrays, transport distances are smaller, and a surface area of a current collector that is in contact with an electrode material can be significantly greater, thereby increasing heat transport. Heat dissipation can also be enhanced by the backbone structure 30 itself. For example, a thermal conductivity of the backbone structure 30 can be tailored to provide enhanced heat dissipation, while maintaining other desired properties for the backbone structure 30.

[0022] However, it would be preferable to design the electrode and current collector architecture to optimize other performance metrics, such as energy density, rather than to constrain the design of the electrode and current collector architecture based on their performance as a heat sink. Accordingly, three-dimensional designs that incorporate PTC materials in an integrated manner, including up to an individual electrode or sub-electrode level, are disclosed herein. Integrating the PTC material at the individual electrode level can increase sensitivity and provide more reliable isolation in the event of a short. Also, the use of such materials can lead to adequate safety even where the electrodes and current collectors do not function well as heat sinks.

[0023] Conducting polymer PTC materials typically comprise a polymer having electrically conductive particles. Under normal operating conditions many of the electrically conductive particles are in contact with each other so that the PTC material has a relatively low electrical resistance. However, when the temperature rises above a glass transition temperature of the PTC materials, for example if too high a current passes through the PTC material, then thermal expansion of the PTC material causes the conducting particles to separate and causes the electrical circuit to substantially open. In this state, the PTC material presents a higher electrical resistance to the current flow and thereby reduces the electrical current to a lower and safer level. Examples of such PTC materials include high density polyethylene loaded with graphite particles, titanate ceramic materials such as barium titanate, and so forth.

[0024] In certain embodiments of the present invention, PTC materials are integrated at a more fundamental level in a three-dimensional battery architecture, in order to provide enhanced safety. One such example is the architecture shown in FIG. 4. This architecture includes a battery enclosure 4 and a plurality of parallel plate electrodes (cathodes 42 and anodes 43) within the battery enclosure 4. The cathodes 42 preferably but not necessarily include lithium ion insertion electrodes comprising LiCoO.sub.2, Li(Ni.sub.xCo.sub.yAl.sub.z)O.sub.2, LiFePO.sub.4, Li.sub.2MnO.sub.4, or the like. The anodes 43 preferably comprise a material such as graphite, a titanate, silicon, aluminum, and/or tin. The cathodes 42 and anodes 43 are preferably assembled with a separator 44 between them. Each of a second plurality of electrodes (e.g., cathodes 42), selected from the first plurality of electrodes, protrudes from a first structural layer (e.g., current collector layer 40 or a layer underlying current collector layer 40) through a current-reducing device (e.g., an adjacent region of PTC material 41). Preferably, but not necessarily, the parallel plate electrodes comprise fins that protrude from the first structural layer at least 50 microns. Also within the battery enclosure 4, a third plurality of electrodes (e.g., anodes 43), selected from the first plurality of electrodes, protrudes from a second structural layer (e.g., current collector layer 46 or a layer underlying current collector layer 46) through current-reducing devices (e.g., adjacent regions of PTC material 45). The PTC material 41 provides a local fuse for each of the cathodes 42 and the PTC material 45 provides a local fuse for each of the anodes 43. In the event of a short involving one of the cathodes 42, a local isolation of that particular cathode 42 can take place due to a local expansion of the PTC material 41 Likewise, in the event of a short involving one of the anodes 43, a local isolation of that particular anode 43 can take place due to a local expansion of the PTC material 45. In addition to providing the ability to cut off individual sub-units in the battery, this architecture also increases the reliability of a shut-off process in the battery. This is due to an increase in the ability to detect heat in these sub-units.

[0025] A characteristic of some three-dimensional batteries is that there are sub-unit micro-cells that contribute current to an overall larger cell. For example, if each sub-unit micro-cell in FIG. 4 is 100 microns, and the overall cell is 1 cm wide, there will be 100 cathodes and 100 anodes in the overall cell. Each cathode will, in normal operation, have 1/100 of a total current passing through it. However, in the case of an electrical short, a current increases to an amount much higher than the normal current. This rapid increase in current will trigger a corresponding local increase in heat and ensure that the PTC material 41 is reliably triggered. This integration of a self-regulating fuse into a three-dimensional battery provides an advantageous safety feature, namely the ability to respond to shorts within an overall cell. This intra-cell shorting response feature is accomplished in certain embodiments due to the three-dimensional architecture and integrated PTC materials, wherein a current is split into multiple micro-cells within the overall cell. Each of these micro-cells can be independently monitored and regulated to provide increased level of safety.

[0026] FIG. 5 shows another example of an integration scheme for a PTC material 51, 56 on a three-dimensional architecture that includes a first plurality of electrodes within a battery enclosure 5, the first plurality of electrodes comprising an interdigitated array of pillars 52, 53. Each of a second plurality of electrodes (e.g., pillar-shaped cathodes 52), selected from the first plurality of electrodes, protrudes from a first structural layer 57. Also within the battery enclosure 5, a third plurality of electrodes (e.g., pillar-shaped anodes 53), selected from the first plurality of electrodes, protrudes from a second structural layer 58. Structural layers 57 and 58 may be electrically conductive or include an electrically conductive coating.

[0027] In the embodiment of FIG. 5, current collector 50 provides an electrical path to cathodes 52 via PTC material 51. This approach provides flexibility to incorporate the PTC material 51 in a variable fashion. For example, the PTC material 51 can be added at any place along the current collector 50. A design may specify or optimize a specific number of cathodes 52 that are connected without being separated by the PTC material 51. Likewise, current collector 55 provides an electrical path to anodes 53 via PTC material 56. The PTC material 56 can be added at any place along the current collector 55. A design may specify or optimize a specific number of anodes 53 that are connected without being separated by the PTC material 56.

[0028] That is, the PTC material 51 provides a local fuse for groups of cathodes 52 and the PTC material 56 provides a local fuse for groups of anodes 53. In the event of a short involving one of the cathodes 52, a local isolation of its associated group of cathodes 52 can take place due to a local expansion of the PTC material 51. Likewise, in the event of a short involving one of the anodes 53, a local isolation of its associated group of anodes 53 can take place due to a local expansion of the PTC material 56. This provides the ability to cut off particular sub-groups of electrodes within the battery enclosure 5, and thereby increases the reliability of a shut-off process in the battery.

[0029] FIG. 6 addresses another approach to use a PTC material 64 in a three-dimensional battery. This approach allows isolation of each cathode 61 and anode 62 in the event of a temperature increase. In this approach, the PTC material 64 is integrated into every cathode 61 and anode 62 before it is connected to a current collector 60. In this case, a separator 63 inhibits the PTC material 64 from shorting.

[0030] The embodiment of FIG. 6 includes a battery enclosure 6 and a first plurality of electrodes (cathodes 62 and anodes 63) within the battery enclosure 6. The cathodes 62 and anodes 63 preferably but not necessarily include lithium ion insertion electrodes comprising LiCoO.sub.2 or the like, and are assembled with a separator 61 in between. Each of a second plurality of electrodes (e.g., anodes 63), selected from the first plurality of electrodes, protrudes from a first structural layer (e.g., current collector layer 65 or a layer underlying current collector layer 65) through a current-reducing device (e.g., PTC material 66). Also within the battery enclosure 6, a third plurality of electrodes (e.g., cathodes 62), selected from the first plurality of electrodes, protrudes from a second structural layer (e.g., current collector layer 60 or a layer underlying current collector layer 60) through current-reducing devices (e.g., PTC material 64). The PTC material 64 provides a local fuse for each of the cathodes 62 and the PTC material 66 provides a local fuse for each of the anodes 63. In the event of a short involving one of the cathodes 62, a local isolation of that particular cathode 62 can take place due to a local expansion of the PTC material 64 Likewise, in the event of a short involving one of the anodes 63, a local isolation of that particular anode 63 can take place due to a local expansion of the PTC material 66.

[0031] Traditional PTC materials can be reversible in nature, which means that an isolated electrode may be electrically reconnected once an event that changed the state of the PTC material has passed. This provides the advantage of maintaining the capacity of an energy storage device. A similar result may be obtained by replacing the PTC material with solid-state switches that are responsive to a detector of current or temperature. However, in certain embodiments of the present invention, the PTC materials can be replaced with fuse-like materials that provide permanent open circuits in the event of a short, thereby isolating that particular electrode permanently. Such a permanent mechanism may be preferable in certain three-dimensional batteries, for example where each micro-cell accounts for very small values in terms of total current and capacity. Such a battery can continue to operate at a high level of efficiency even when a few micro-cells are permanently isolated in response to shorting.

[0032] While the invention has been described with reference to the specific exemplary embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention as defined by the appended claims. It is contemplated that various features and aspects of the invention may be used individually or jointly and possibly in a different environment or application. The specification and drawings are, accordingly, to be regarded as illustrative and exemplary rather than restrictive. Comprising, including, and having, are intended to be open-ended terms.