METHOD FOR MANUFACTURING ALL-SOLID-STATE BATTERY

Abstract

Electrodes are formed by, as a dry method, alternately applying electrode active material and electrolyte particles as thin-film layers. Furthermore, the films are formed wholly or partially by employing an aerosol deposition method. Moreover, high-density layers can be formed and adhesion is improved by, as a wet method, impactfully and alternately colliding, with a target object, slurry made primarily from an electrode active material and solvent and a slurry made primarily from electrolyte particles and a solvent, adhering same in thin films and layering same. A slurry made primarily from a conductivity aid and a solvent is independently prepared, and a small quantity thereof is applied diffusely at a desired position. Moreover, by using no binder or keeping binder content low, residual carbon can be eliminated or kept low so as to improve battery performance.

Claims

1. A method for manufacturing an all-solid-state battery having a positive electrode, an electrolyte, and a negative electrode in layers, comprising: selecting at least two materials selected from the group consisting of positive electrode active material particles, electrolyte particles or short fibers, negative electrode active material particles or short fibers, conductive assistant particles or short fibers, and a binder; and by using each coating device for the respective materials, applying the materials alternately on an object so as to form multiple thin layers, wherein the object is at least one selected from the group consisting of a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative electrode current collector.

2. The method according to claim 1, wherein the number of the layers made of the particles or the fibers is 2 to 30.

3. The method according to claim 1, wherein the at least two materials are positive electrode active material particles and electrolyte particles or short fibers.

4. The method according to claim 1, wherein the at least two materials are at least three materials, the conductive assistant is selected from at least one of carbon nanofibers, porous carbon particles, carbon nanotubes, and graphene, the conductive assistant and the active material are alternately applied, and the conductive assistant is at least scattered thereby the conductive assistant do not form a continuous layer.

5. The method according to claim 1, wherein the electrolyte is sulfide, and the positive electrode active material is porous carbon particles or carbon short fibers and metallic silicon or silicon oxide (SiOx).

6. The method according to claim 1, wherein the object is an oxide electrolyte, and the positive active material and the conductive assistant are alternately applied.

7. The method according to claim 6, wherein a base of the oxide electrolyte is lithium lanthanum zirconia, the positive electrode active material is sulfur particles, and the conductive assistant is at least one selected from the group consisting of carbon nanofibers, mesoporous carbon particles, carbon nanotubes, and graphene.

8. The method according to claim 1, wherein at least two slurries comprising a solvent and at least one selected from the positive electrode active material particles, electrolyte particles or short fibers, negative electrode active material particles or short fibers, conductive assistant particles or short fibers, and binder are alternately applied on the object to form the multiple thin layers.

9. The method according to claim 8, wherein each slurry is applied to the object in the form of particles in order to form fine irregularities at least at an interface between the positive electrode layer and the electrolyte layer, or at an interface between the electrolyte layer and the negative electrode layer of the positive electrode active material particles, electrolyte particles or short fibers, negative electrode active material particles or short fibers, conductive assistant particles or short fibers, and binder to increase a surface area of each interface.

10. The method according to claim 9, wherein the slurry is applied as particles with a pulsed dosing device or a pulsed splay coating device head, pulses are applied at 1 to 1000 Hz, and a distance between the head and the object is 1 to 60 mm.

11. The method according to claim 9, wherein the fine irregularities promote volatilization of the solvent of the slurry particles by heating the object, and the fine irregularities include a combination of irregularities of trajectory caused by lapping of pulsed spray pattern and fine irregularities caused by the spray particles.

12. The method according to claim 1, further comprising filling or applying alternately the at least two materials selected from the group consisting of positive electrode active material particles, electrolyte particles or short fibers, negative electrode active material particles or short fibers, conductive assistant particles or short fibers, and binder on at least one substrate in advance so as to form the multiple thin layers, and transporting the filled or applied materials with a pressure difference to the upstream of the object under vacuum to apply and deposit the materials onto the object by splaying.

13. The method according to claim 12, wherein the filling or applying of the at least two materials onto the at least one substrate in the form of the multiple thin layers is filling or applying onto separate substrates, and the materials on the separate substrates are transported to the upstream of the object with a pressure difference under vacuum to apply and deposit the material alternately onto the object by splaying.

14. The method according to claim 12, wherein the filling or applying of the at least two materials onto the at least one substrate in the form of the multiple thin layers is to apply the at least two slurries comprising a solvent and at least one selected selected from the positive electrode active material particles, electrolyte particles or short fibers, negative electrode active material particles or short fibers, conductive assistant particles or short fibers, and binder.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0058] FIG. 1 shows a schematic diagram of spraying active material onto an object (current collector) and then dispersing and coating the active material particles so that the conductive assistant adheres to them, according to the present embodiment.

[0059] FIG. 2 shows a schematic diagram for electrolyte particles and different (e.g., conductive assistant) particles being splayed onto the active material particles attached on the object, according to the present embodiment.

[0060] FIG. 3 shows a schematic cross-sectional view of two types of particles laminated together, according to the present embodiment.

[0061] FIG. 4 shows a schematic cross-sectional view of a current collector, positive electrode layer, electrolyte layer, negative electrode layer, and current collector laminated together, according to the present embodiment.

[0062] FIG. 5 shows a schematic cross-sectional view of electrode slurries being splayed onto the objects (current collector and electrolyte layer), according to the present embodiment.

[0063] FIG. 6 shows a schematic cross-sectional view of the splay on the objects (electrolyte layer and electrode layer), according to the present embodiment.

[0064] FIG. 7 shows a schematic cross-sectional view of the splay on the object (electrolyte layer), according to the present embodiment.

[0065] FIG. 8 shows a schematic cross-sectional view of the lamination by the alternated splaying of different materials onto the object (current collector) in a pulsed manner and with a time difference, according to the present embodiment.

[0066] FIG. 9 shows a schematic cross-sectional view of a plurality of materials stacked on a substrate using a plurality of coating devices in advance of applying or depositing the materials on the object.

DESCRIPTION OF EMBODIMENTS

[0067] Now, a preferred embodiment of the present invention will be described with reference to the drawings. However, the embodiment below is only an example for facilitating the understanding of the present invention. Addition, replacement, deformation, or the like executable by those skilled in the art can be made thereto without departing from the technical idea of the present invention.

[0068] The drawings schematically show the preferred embodiment of the present invention.

[0069] In FIG. 1, a slurry containing electrode active material particles and a solvent or a slurry containing active material particles, a solvent and a binder is sprayed from a spray head 21 onto a current collector 1 as an object, resulting that active material spray particles 2 are attached thereon. A conductive assistant 9 or 9′ can be applied to the active material from another spray head 27 and dispersed on the active material 2′. The object can be a sheet or a long sheet. The coating device can be either batch type or roll-to-roll type. Any type of the active material particles can be used. When an electrolyte is made of sulfide, a positive electrode active material such as lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA) or the like reacts with sulfur, resulting that it is difficult for lithium ions to pass through. Therefore, the active material particles may be coated with a thin layer of lithium niobate or other materials. The active material particles or electrolyte particles may be encapsulated with the electrolyte or the active material, respectively, which makes the process shorter and simpler, and thus more productive. Adhesion can be improved by pulsed spraying and attaching the spray particles to the current collector with impact at a high speed. The impact on the sprayed particles 2 can be archived by keeping the distance between the object and the spray head close, e.g., 1 to 60 mm, and by pulsed splaying at a gas pressure of 0.15 to 0.3 MPa using a two-fluid nozzle with a splay pattern of a narrow splay angle, e.g., at 30 degrees or less, preferably 20 degrees or less. The number of pulses per second is preferably 10 Hz or higher for productivity. The shorter the distance and the narrower the splay pattern angle, the higher the impact. A slurry containing mainly the electrolyte particles and solvent may be sprayed first. It is preferable that a room where the spray is applied such as a booth, is under exhausted conditions. If the electrolyte is sulfide, the supplied gas should be dehumidified. The lower a dew point temperature, the better the dehumidification. For example, an all-solid-state battery with almost no hydrogen sulfide and good performance can be produced at a temperature of minus 80 degrees Celsius or less. For materials that need to avoid oxidation, a heating process, for example, may be performed under an inert gas (e.g., argon) atmosphere to suppress oxidation reaction if necessary.

[0070] FIG. 2 shows dispersed applying of particles 3 and 3′ in a thin layer by splaying a slurry (containing, e.g., electrolyte particles) different from that of FIG. 1 around and on top of the thin layer such as a single layer (e.g., made of an active material 2) with a head 22. The splay of the active material from the head 21 in FIG. 1 and the splay of the electrolyte from the head 22 may be applied alternately to build up multiple thin layers. Instead of or in addition to the electrolyte particles, a solution or slurry including a conductive assistant such as lithium iodide or at least one conductive assistant selected from the group consisting of carbon particles, carbon fibers and carbon nanotubes, or a slurry of the mixture of them with the electrode active material or the electrolyte particles is sprayed from the spray head 22 and then the sprayed particles 3 are adhered. Pore carbon and nanocarbon with large surface area, which is the conductive assistant, are excellent. For example, when it has 2,000 square meters per gram or more in BET plot, and preferably 3,500 square meters or more, the electrode performance can be improved by encapsulating the sulfur or the active materials in the positive electrode and nano-level silicon in the negative electrode, in the nano-level pores in advance.

[0071] In FIG. 3, the electrode active materials 2 and electrolyte particles 3 are applied alternately to make multiple layers. Weight ratio per unit area of each can be freely selected, and the ratio can be easily adjusted by selecting the number of pulses, especially by performing pulsed spraying. Furthermore, a different spray head can be used to disperse and apply the desired amount of conductive assistant around the electrolyte and electrode active material to achieve the adhesion.

[0072] In FIG. 4, a positive electrode layer 11 and a negative electrode layer 13 are applied on both sides of an electrolyte layer 12, and the electrodes 11 and 13 are sandwiched between the current collectors 1 and 10. A laminated structure for the all-solid-state battery is completed by pressing it under heated condition or at room temperature. As the current collector, aluminum foil and copper foil are generally used for the positive electrode and the negative electrode, respectively, but not limited thereto, stainless steel sheet may be used depending on the types of the active material and electrolyte.

[0073] In FIG. 5, an electrolyte slurry and a negative electrode active material slurry are alternately sprayed from the spray heads 24 and 23, respectively, to form the negative electrode layer on the positive electrode current collector 1, the positive electrode layer 11, the electrolyte layer 12 and on the negative electrode current collector, and then pressing is performed using rolls 31 and 31′. When this pressing is performed in the subsequent process, the pressing pressure can be almost none or low. The rolls may be heated, and the current collector, electrode layer, and electrolyte layer may also be heated in advance to promote the volatilization of the solvent contained in the sprayed particles 4 and 5.

[0074] In FIG. 6, the electrolyte slurry, an electrode active material slurry or both is sprayed to the interface between the electrolyte layer 12 and the negative electrode layer 13 with a spray head 25. A slurry containing the electrolyte particles and electrode active material may also be sprayed. It is also possible to increase adhesive strength of the interface by spraying the solvent or the like to instantly swell the binder or the like at the respective interface. It is moved by the rolls 31 and 31′ with or without the pressing pressure. There is no limit to the load, diameter, or number of press rolls.

[0075] In FIG. 7, the slurry for the electrolyte layer or the solvent is sprayed onto the electrolyte layers formed on both the positive and negative electrode layers on flexible current collectors. The effect is as described above. A separately manufactured electrolyte thin plate or a flexible electrolyte membrane with which a porous substrate is filled can be sandwiched between the positive and negative electrodes without the electrolyte layer.

[0076] In this case, the electrolyte slurry, each active material slurry, binder solution, or solvent can be applied to the surface of the electrolyte or each electrode to improve the adhesion.

[0077] In FIG. 8, the negative electrode active material slurry is sprayed onto the negative electrode current collector 10 from the spray head 23 in a pulsed manner to form sprayed particle clusters 7. On the other hand, the electrolyte slurry is pulsed sprayed from the spray head 24 to form sprayed particle clusters 8, and each sprayed particle cluster is alternately applied on the negative electrode current collector. Preferably, it is multiple thin layers.

[0078] Similarly, a slurry containing mainly the positive electrode active material and solvent and a slurry containing mainly the electrolyte and solvent can be alternately applied on the positive electrode current collector. Furthermore, an additional head, not shown in the figure, can be used to splay a small amount of conductive assistant slurry in a pulsed manner alternately from the head 23 or 24.

[0079] If the electrolyte is a sulfide, these operations should be performed in a dehumidified environment, e.g., sufficiently dehumidified at a dew point −40° C. or less, where hydrogen sulfide is not generated.

[0080] The object may be a long R to R current collector or porous sheet for the electrolyte layer, or it may be a single leaf current collector, a porous sheet for the electrolyte or a sheet with electrodes formed on the current collector. The electrode may have a periphery formed by intermittent coating with a slot nozzle to weld tabs or other components at the end of the current collector by a laser beam. Masks can also be used in spraying, or the perimeter can be formed by the application at close range.

[0081] In FIG. 9, two kinds of materials are alternately applied to a moving substrate (belt) 120 by coating devices 111 and 112 to make multiple layers. The more times the materials are stacked, the better the result is. The two materials may be the electrode active material and the electrolyte, or they may be other materials. Three or four kinds of materials can be stacked. The belt can be porous to suck gas during suction and produce an ideal gas-powder mixture. A connecting means 150 such as a pipe is connected between the stacked material 101 and the object 130 in the vacuum chamber 202, and the differential pressure between the coating chamber 201 and the vacuum chamber causes the suction of stacked material in the entrance of the pipe to splay the material at the exit thereof, and material collides with the object to form a film on the object, and then a composite 150 of the film is wound up by the winding device 160. The composite 140 may be a dense coating layer instead of the film. The composite 140 may be pressed in a press (not shown). The vacuum chamber should be at a vacuum pressure suitable for aerosol deposition. For better film deposition, the active material should be relatively soft. Powder binder particles are easier to deposit. A pre-vacuum chamber 203 can be installed before and after the vacuum chamber to maintain the vacuum pressure of the vacuum chamber 202 at the desired vacuum pressure. The vacuum can be sucked by vacuum pumps 300, 301 and 302 to achieve the desired vacuum value. The coating chamber can also be vacuumed and an inert gas such as argon gas can be introduced from outside on the opposite side of the porous belt 120 where a laminated body of the material is sucked if the laminated material is an oxygen averse material.

[0082] In this invention, slot nozzles can be used to apply the slurry at high speed to objects having a wide of, for example, 1500 mm in order to increase productivity. In addition, a head group including 100 to 200 spray heads arranged in one or more rows orthogonal to the direction of movement of an object with a width of, for example, 1500 mm can spray with impact in order to increase the productivity. If necessary, the head group can be moved back and forth (swung) in the head arrangement direction by, for example, 15 mm to sufficiently lap a pattern of, for example, 15 mm. The heads can be arranged for the required type of the slurry and for the desired number of laminations to meet the required speed.

[0083] When the structure of the head wants to be simplified, grooves, for example, every 10 millimeters in the width direction (disclosed in JPH08-309269A, of which inventor is the same as the present inventor) are formed by using a wide roll capable of forming grooves, for example, every 10 millimeters in the width direction (disclosed in JPH08-309269A, of which inventor is the same as the present inventor) and the slurry filled in the grooves is converted into particles by compressed gas, which can be adhered to the object. The speed of the object can theoretically be 100 meters per minute or more. Preferably, the number of roll devices to be placed orthogonal to the direction of movement of the object is determined according to the type of the slurry and the number of laminations.

[0084] In addition, a plurality of rotary screens can be installed in the direction of movement, based on the invention of the present inventor in JPH06-86956. A cylindrical screen or seamless belt with a width equal to or wider than the width of the object to be coated, equipped with numerous through holes (e.g., 150 micrometer diameter holes) filled with the slurry or powder, may be used. When this cylindrical screen or seamless belt faces the object, the slurry is converted into fine particles to spray them by liquefied or compressed gas and evenly adhere to the entire surface of the object. Instead, a commercially available rotary screen for screen printing can be used to reduce the cost. The same effect can also be obtained by using a cylindrical pipe wider than the object, for example, with staggered holes of about 0.3 mm or 0.5 mm in diameter with a pitch of 1.5 mm.

[0085] For the above two methods, the distance between the object and the location where the particles are blown out should be 1 to 60 millimeters to improve the impact effect. In the above two methods which also double as a volumetric feeding method, the line can be followed by changing the rotation speed, so there is no need for expensive pumps or controllers, and in the roll-to-roll process of a roll coater or rotary screen printer, equipment design and manufacturing can be performed and it is also possible to modify and use the electrode lines of some conventional lithium batteries.

[0086] In this invention, the slurry can be made into particles and moved by pressure difference, and the particleization can be performed by inkjet. It can also be particleized by a disc or bell rotating atomizer used in the general coating field. Other methods such as atomization with a bubbler or ultrasonic waves and further refinement by hitting a rotating roll at close range with a spray stream are also acceptable. A particle group converted into particles may be transferred by carrier gas and attached to the object by differential pressure.

[0087] The impact of the differential pressure can be increased by using a higher gas pressure just before attachment to draw out the particles with an ejector effect and make them collide at high speed.

[0088] Furthermore, if the movement is performed in pulses, the adhesion efficiency and impact will be increased, which is even better.

INDUSTRIAL APPLICABILITY

[0089] According to this embodiment, an all-solid-state battery with low interfacial resistance and high adhesiveness, which has a laminated structure including electrolyte, electrodes, and current collectors, can be manufactured with high quality.

DESCRIPTION OF THE REFERENCE NUMERAL

[0090] 1 Positive electrode current collector [0091] 2, 4 Active material splay particles [0092] 2′ Electrode active material [0093] 3, 5 Electrolyte splay particles [0094] 3′ Electrolyte particles [0095] 6 Solvent splay particles or the like [0096] 7 Electrode active material splay particle group [0097] 8 Electrolyte spray particle group [0098] 9, 9′ Conductive assistant [0099] 10 Negative electrode current collector [0100] 11 Positive layer [0101] 12 Electrolyte layer [0102] 13 Negative layer [0103] 21, 22, 23, 24, 25, 27, 111, 112 Spray head (coating device) [0104] 31, 31′ Roll [0105] 101 Stacked material [0106] 110 Unwinding device (belt) of an object [0107] 120 Substrate (belt) [0108] 130 Object [0109] 140 Composite [0110] 150 Connecting pipe [0111] 160 Winding device [0112] 170 Free roll [0113] 201 Coating chamber [0114] 202 Vacuum chamber [0115] 203 Pre-vacuum chamber [0116] 300, 301, 302 Vacuum pump