Thermal evaporation process for manufacture of solid state battery devices

Abstract

A method for manufacturing a solid-state battery device. The method can include providing a substrate within a process region of an apparatus. A cathode source and an anode source can be subjected to one or more energy sources to transfer thermal energy into a portion of the source materials to evaporate into a vapor phase. An ionic species from an ion source can be introduced and a thickness of solid-state battery materials can be formed overlying the surface region by interacting the gaseous species derived from the plurality of electrons and the ionic species. During formation of the thickness of the solid-state battery materials, the surface region can be maintained in a vacuum environment from about 10.sup.−6 to 10.sup.−4 Torr. Active materials comprising cathode, electrolyte, and anode with non-reactive species can be deposited for the formation of modified modulus layers, such a void or voided porous like materials.

Claims

1. A method for manufacturing a cathode for a solid-state battery device using a flash process comprising: providing a substrate on a transfer device; continuously feeding a metal oxide cathode source material to an evaporation source, wherein the evaporation source is located under the substrate; subjecting the metal oxide cathode source material to thermal energy to cause a portion of the source to evaporate into a vapor phase free from undesirable metal oxide species; forming a metal oxide material layer overlying the substrate by condensing the vapor phase as the substrate moves either in a first direction or a second direction; subjecting the metal oxide material layer to an ion source while the thickness of metal oxide material layer is being formed to incorporate a nitrogen content of the metal oxide material layer of 2% to 4% to achieve an electrical conductivity of the metal oxide material layer of 10.sup.−6 to 10.sup.−5 S/m; and maintaining the substrate in a vacuum environment during the formation of the metal oxide material layer.

2. The method of claim 1, wherein the forming of the metal oxide material layer occurs at a rate of about 100 to 10,000 Angstroms per second per 100 square centimeters; wherein the ion source is an ion beam or an ion shower.

3. The method of claim 1, wherein the substrate moves at a rate of about 1 inches/min to about 10 feet/min.

4. The method of claim 1, wherein cathode source comprises vanadium oxide.

5. The method of claim 1, wherein the metal oxide cathode source comprises vanadium oxide, manganese oxide, iron oxide, nickel oxide, sulphur oxide, cobalt oxide, or magnesium oxide.

6. The method of claim 1, wherein subjecting the metal oxide layer comprises introducing a dopant species into the metal oxide material layer to cause an increase in conductivity of the metal oxide material layer and cause an increase in ionic diffusivity of the metal oxide material layer.

7. The method of claim 1, further comprising introducing a dopant species into the metal oxide material layer, the dopant comprising nitrogen, oxygen, carbon, fluorine, silver, molybdenum, copper, tin, aluminium, iodine, phosphorous, or silicon.

8. The method of claim 1, wherein the thermal energy is provided by an e-gun, a sputtering process or on a hot wall reactor region; wherein the hot wall reactor region is characterized by a temperature ranging from about 600 to 1200 Degrees Centigrade; wherein the metal oxide cathode material is vanadium oxide; wherein the ion source is provided at an energy from about 100 to about 400 electron volts.

9. The method of claim 8, wherein the thermal energy is provided by a region of a hot wall reactor and further comprising a shaped mask device configured between the region of the hot wall reactor and the substrate, the shaped mask device configured to be coupled to a heating device to maintain the shaped mask device essentially free from a residue from the metal oxide cathode source and positioned to allow either demarcation of the cathode source r oblique angle deposition for the formation of voids or a porous cathode or cathode modification layer.

10. The method of claim 1, wherein the transfer device comprises a first drum coupled to a second drum and configured in a reel to reel.

11. The method of claim 1, wherein the substrate is configured for single or multiple passes of the substrate in the vacuum environment.

12. The method of claim 1, wherein the cathode source is one of a plurality of sources within the vacuum environment.

13. The method of claim 1, wherein the metal oxide material layer comprises a mixture of cathode and anode material co-deposited to form a cathode layer in a partially or fully discharged state with modified intercalation stresses.

14. The method of claim 1, wherein the vapor phase comprises entrained non-reactive species in the shape of nano rods, cones, columns, fibers, or spheres, with or without a binder, to form voids or a voided porous cathode or cathode modification layer.

15. The method of claim 1, wherein the energy source comprises a plurality of respective energy sources which are configured to be combined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The following diagrams are merely examples, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. 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 process and scope of the appended claims.

(2) FIG. 1 is a simplified diagram illustrating a flash process for depositing a film of material for an electrochemical cell according to an embodiment of the present invention;

(3) FIGS. 2A-2H are simplified diagrams illustrating a method of fabricating an electrochemical cell according to an embodiment of the present invention;

(4) FIG. 3 is a simplified diagram of a processing apparatus according to an embodiment of the present invention;

(5) FIG. 4 is a simplified flow diagram of a process flow using a combination of energy evaporation source and ion beam doping according to an alternative embodiment of the present invention;

(6) FIG. 5 is an illustration of experimental results of electrochemical impedance spectroscopy (EIS) to measure cathode electronic conductivity according to examples of embodiments of the present invention; and

(7) FIG. 6 is a illustration of experimental results of electrochemical impedance spectroscopy (EIS) to measure electrolyte ionic conductivity according to examples of embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(8) According to the present invention, processing techniques related to manufacture of solid-state electrochemical cells are provided. More particularly, the present invention provides methods for manufacture of electrodes (cathode and anode) and electrolyte materials by flash evaporation processes for continuous roll-to-roll production, and ion-beam assisted processes for adjusting the required layer properties.

(9) Merely by way of example, the invention has been provided with a vacuum system configured for a multiple pass roll-to-roll coater, in which a substrate is coated with a sequence of steps by changing in direction of the movement of the substrate within a single vacuum chamber. In an alternative approach, the substrate may be moved in the same direction around the reels as a single pass deposition process, with conditions within the chamber periodically changed to result in the continuous build-up of deposited material over time. Alternatives can also be provided where steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein. Further details of the present method can be found throughout the present specification.

(10) FIG. 1 illustrates a schematic diagram of a flash process for depositing battery material onto a moving substrate in roll-to-roll configuration where the substrate moves from a reel to another reel according to an embodiment of the present invention.

(11) In particular, the flash deposition process of FIG. 1 comprises an evaporation source and an ion beam source to deposit thin film materials making up an electrochemical cell. The evaporation source is a hot wall reactor or an electron beam. The ion beam source is an ion beam or an ion shower. A source material is loaded in the source feeder and fed continuously onto a hot evaporation source to evaporate on contact during the process. In a specific embodiment, the evaporation occurs at a temperature of about 200 to about 1200° C., but can be others. The ion source provides reactive species to the substrate surface for ion beam assisted deposition. Of course, there can be other variations, modifications, and alternatives.

(12) FIG. 2A-2H illustrate simplified cross-sectional views of each process step showing an electrochemical cell layer formed according to an embodiment of the present invention. The process of each layer will follow the process flow steps by FIG. 4 and described later in this section. As shown, the process includes deposition of one or more of the following layers: a barrier, a cathode current collector, a cathode, an electrolyte, an anode, an anode current collector, and an interlayer barrier.

(13) FIG. 3 is a simplified schematic diagram illustrating an apparatus for depositing battery material onto a substrate according to an embodiment of the present invention.

(14) In particular, the apparatus of FIG. 3 comprises a vacuum deposition chamber. The chamber is made of stainless steel, but can be others. The chamber is subjected to a vacuum of about 10.sup.−6 to about 10.sup.−4 Torr. The vacuum deposition chamber is configured to deposit thin films of materials making up an electrochemical cell. In particular, the vacuum deposition chamber is in fluid communication with a plurality of material sources allowing deposition of one or more of the following layers: a barrier, a cathode current collector, a cathode, an electrolyte, an anode, an anode current collector, and an interlayer barrier.

(15) In a specific embodiment, the barrier can include an oxide of metal or metalloid, nitride of metal or metalloid, carbide of metal or metalloid, or phosphate of metal.

(16) In a specific embodiment, the cathode material can include vanadium oxide, manganese oxide, iron oxide, nickel oxide, sulfur oxide, cobalt oxide, or magnesium oxide.

(17) In a specific embodiment, the electrolyte material can include lithium oxide or lithium phosphide or lithium phosphate or lithium sulfate or lithium borate.

(18) In a specific embodiment, the anode material can include lithium metal or a lithium alloy.

(19) In a specific embodiment, the interlayer barrier material can include an oxide of metal or metalloid, nitride of metal or metalloid, carbide of metal or metalloid, or phosphate of metal.

(20) In a specific embodiment, the current collectors can include nickel or copper or aluminum or other conductive metals.

(21) Specifically, the vacuum deposition chamber is configured to have at least one evaporation source to deposit layers of battery materials onto a moving substrate. The vacuum deposition chamber also includes at least one ion beam source to provide reactive species to the active layers of battery cathode, electrolyte and anode materials. The deposition chamber is provided with at least one source feeder that deliver source materials to the evaporation sources during the flash deposition processes.

(22) In a specific embodiment, the flash process is a film deposition process delivering the metered stream of evaporant to the hot wall of the reactor in a pattern whereas the balance between mass delivered and mass evaporated is constant, without causing residence times which would degrade the evaporant or coat the reactor surface.

(23) FIG. 4 is a simplified flow diagram showing the steps of a process flow of forming a battery structure utilizing the flash evaporation process described in this invention. Specifically, in a first step, the reels and drum are rotated to move a substrate in a first direction through the deposition chamber. In this step, the substrate is prepared for deposition with conditions including web tension and temperature.

(24) In a second step, the barrier material is deposited on the substrate, which prevent any reaction between the substrate and battery materials during fabrication process and during the battery cycle life. This barrier also works as an insulating layer if the substrate is electrically conducting.

(25) In a third step, the number of cell layers is compared to the target value based on the battery capacity, and the process steps for the next cell layer continue until the final cell layer is made.

(26) In a fourth step, the current collector material for cathode or positive terminal is deposited. In a fifth step, the cathode material is deposited on the cathode current collector. Energy thermal source such as a hot wall reactor or an electron beam is used for the evaporation of metal oxide cathode material with an ion beam source providing dopant species into the thickness of metal oxide to increase conductivity of metal oxide material and cause an increase in ionic diffusivity of the thickness of the metal oxide material.

(27) In a sixth step, the material of the electrolyte is deposited over the cathode with slow rate as a first layer of the bi-layer electrolyte structure. Energy thermal source such as a hot wall reactor or an electron beam is used for the evaporation of an oxide and a phosphide or a phosphate or a sulfate or borate with an ion source introducing an ionic species to the deposited film to increase ionic conductivity of the electrolyte. Then, in a seventh step, a second layer of electrolyte is continuously deposited with faster deposition rate to form a sufficient thickness of bi-layer electrolyte. The ion-to-atom ratio remains the same by controlling the ion beam source throughout the two electrolyte processes (sixth and seventh steps) for uniform material composition and chemical characteristics, such as conductivity.

(28) In an eighth step, the anode material is deposited over the electrolyte. In a ninth step, the material of the anode current collector is deposited on the anode. In a tenth step, another barrier is deposited over the anode and anode current collector providing an insulation and separation between the anode and the next cell layer.

(29) Then, the process flow goes back to the third step to compare the number of cells layers to the target value. The process continues to build multiple cell layers until the target number of cell layers is made, which triggers the next step. In an eleventh step, a final barrier will be deposited over the full number of cell layers to provide hermetic seal to the battery materials.

(30) In a twelfth step, the battery films including multiple layers of barriers, current collectors, cathodes, electrolytes, and anodes are packaged for mechanical support and electrical connection.

(31) The above sequence of steps provides a process according to an embodiment of the present invention. As shown, the method uses a combination of steps including changes in deposition energy sources and ion beam sources with various gas species. Each process step, or a group of steps in the present invention can be done in a separate vacuum chamber equipped with specific combinations of processing tools. The substrate is to pass the series of chambers to completion. The sequence can also be realized by using a single vacuum chamber with changes in the direction of the substrate through the chamber, coupled with changes in deposition conditions within the chamber.

Example 1—Ion Beam Assisted Flash Evaporation Process for High Conductivity Vanadium Oxide Cathode by Nitrogen Doping

(32) This example demonstrates the process of manufacturing a cathode battery material with improved conductivity for high performing electrochemical cells by using ion beam source to provide dopant species. In particular, a vanadium oxide is the cathode material deposited on a polymer substrate in roll-to-roll configuration, and nitrogen is a dopant for conductivity enhancement.

(33) Deposition system as described in FIG. 3 is used for the process, with all the energy sources, ion beam source, and source feeder contained in one vacuum chamber. Vanadium oxide source material is loaded in the feeder prior to the vacuum process, and fed continuously into the evaporation source with a controlled rate throughout the deposition process. When the cathode source is provided on a hot wall reactor region where the hot wall reactor region is characterized by a temperature ranging from about 600 to 1200° C., the vanadium oxide material evaporates immediately on contact.

(34) The ion beam source is provided with nitrogen and argon gasses to form nitrogen and argon plasma where nitrogen is a reactive species and argon is an energy carrier. The ion beam is provided at energy from about 100 to about 400 electron volts, causes the nitrogen species to react with the evaporated vanadium oxide at the condensation region on the substrate. The process can be controlled by several variables including ion beam energy, ion beam gas ratio, and ion-to-atom ratio to determine the resulting cathode properties.

(35) FIG. 5 presents experimental data on the cathode conductivity from different ion beam process conditions. Three EIS measurements are shown in this graph; one from a cathode sample made with no additional ion beam during deposition, one from a cathode with ion beam assisted deposition to incorporate 2% nitrogen, and another from a cathode with ion beam assisted deposition with higher beam power to incorporate 4% nitrogen. By increasing the nitrogen doping in the thickness of cathode film, we can enhance its electrical conductivity from 10.sup.−8 Siemens/meter to about 10.sup.−5 Siemens/meter.

Example 2—Ion Beam Assisted Flash Evaporation Process for High Conductive Lithium Phosphorous Oxynitride Electrolyte with Bi-Layer Structure by Nitrogen and Oxygen Doping

(36) In this example, electrolyte process is demonstrated for high ionic conductivity by using a ion beam source with two active gas species. The electrolyte source material is lithium phosphate, and the ion beam species are nitrogen and oxygen. The source material is fed to the electron beam evaporation source continuously by the source feeder to maintain a pool of melt lithium phosphate source under the sweep of electron beam.

(37) A key to a high yield electrolyte process is making a bi-layer structure where the first layer is thin between 50 and 2000 Angstroms at a rate of less than about 10 Angstroms per second and an overlying second thickness of about 1000 to about 10,000 Angstroms at a rate greater than about 10 Angstroms per second.

(38) Ion beam is provided with nitrogen and oxygen gasses, and provide ionized nitrogen and oxygen to the condensing film to form lithium phosphorous oxynitride electrolyte on the substrate. The ion beam is provided at energy from about 100 to about 400 electron volts. The ion beam energy, nitrogen-to-oxygen ratio, and ion-to-atom ratio cause the compositional changes in the electrolyte and determine its conductivity.

(39) FIG. 6 illustrates experimental data on the electrolyte conductivity from different ion beam process conditions. One sample group is provided with 100% nitrogen to the ion beam source, while the other group is processed with partial oxygen content in the ion beam during deposition. The ionic conductivity of lithium phosphorous oxynitride has improved from 2×10.sup.−5 Siemens/meter to 1×10.sup.−4 Siemens/meter with the additional oxygen in the ion beam process.

(40) While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present invention which is defined by the appended claims.