JP2007227362A - Method for producing solid-state battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a perfect solid-state battery having low internal resistance and high capacity. <P>SOLUTION: The method for producing the solid-state battery includes the steps of: obtaining active material slurry; obtaining solid electrolyte slurry; obtaining current collector slurry; forming an active material green sheet and a solid electrolyte green sheet; forming a green sheet group by laminating the solid electrolyte green sheet on one surface of the active material green sheet to form a first green sheet group, forming a current collector green sheet layer on the other surface of the active material green sheet with the current collector slurry to form a second green sheet group; heating the second green sheet group at 200-400°C in an oxidizing atmosphere; and baking the second green sheet group heated in the heating step at the baking temperature higher than the heating temperature in the heating step in a low oxygen atmosphere to obtain a laminate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solid battery including a laminate including an active material layer, a solid electrolyte layer, and a current collector layer.

  Along with the downsizing of electronic equipment, the battery used as the power source is also required to be downsized. In order to reduce the size of the battery, it is necessary to develop a battery having a high energy density. Among these, lithium ion secondary batteries are attracting attention because of their high voltage and high energy density.

In the lithium ion secondary battery, LiCoO ₂ , LiMnO ₂ or the like can be used as the positive electrode active material. As the negative electrode active material, a carbon material, a silicon alloy, Li ₄ Ti ₅ O ₁₂ or the like can be used. In addition, as the electrolytic solution, a solution in which a Li salt is dissolved in an organic solvent containing a carbonate ester and / or ether can be used.
However, since the electrolytic solution is a liquid, there is a possibility of leakage. Moreover, since electrolyte solution contains a combustible substance, it is necessary to improve the safety | security of the battery at the time of misuse.

  Therefore, development of an all-solid battery using a solid electrolyte is underway. However, the solid electrolyte has lower conductivity and power density than the liquid electrolyte.

  On the other hand, in Patent Document 1, in order to achieve high energy density, a stacked battery including one or more pairs of a positive electrode, a solid electrolyte, and a negative electrode and including an integrated laminate is proposed. Yes. Terminal electrodes connected to the positive electrode and the negative electrode are respectively provided on the side surface of the laminate and any one end surface selected from the upper and lower surfaces. A set of the positive electrode, the solid electrolyte, and the negative electrode is connected in parallel or in series by the terminal electrode. The terminal electrode is formed by plating, baking, vapor deposition, sputtering, or the like.

  In a stacked battery including a gel electrolyte containing a liquid electrolyte, it is difficult to form a terminal electrode using the above method. For example, in the case of plating, moisture contained in the plating solution is mixed into the battery. In the case of baking, boiling and evaporation of the electrolyte occurs. Furthermore, in the case of vapor deposition and sputtering, the terminal electrode needs to be formed in a reduced pressure atmosphere. Therefore, also in this case, boiling and evaporation of the electrolytic solution occur.

Perovskite-type Li _0.33 La _0.56 TiO ₃ and NASICON-type LiTi ₂ (PO ₄ ) ₃ are Li ion conductors capable of conducting Li ions at high speed. In recent years, all solid state batteries using such a solid electrolyte have been studied.

  A solid battery comprising an inorganic solid electrolyte, a positive electrode active material, and a negative electrode active material can be produced, for example, as follows. First, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer are sequentially laminated to form a laminate. Then, a solid battery can be obtained by sintering a laminated body by heat processing. By this method, the interface between the positive electrode active material layer and the solid electrolyte layer and the interface between the solid electrolyte layer and the negative electrode active material layer can be joined. However, using this method has been disadvantageous for various reasons.

For example, in Non-Patent Document 1, when LiCoO ₂ that is a positive electrode active material and LiTi ₂ (PO ₄ ) ₃ that is a solid electrolyte are sintered, both react in the sintering process, contributing to charge / discharge reactions. It has been reported that compounds such as CoTiO ₃ , Co ₂ TiO ₃ , Co ₂ TiO ₄ , and LiCoPO ₄ are formed. That is, by sintering, a material that is neither an active material nor a solid electrolyte is generated at the interface between the active material layer and the solid electrolyte layer, so that the interface between the active material layer and the solid electrolyte layer is electrochemically inactivated. May end up.

In order to solve such a problem, for example, Non-Patent Document 2 proposes the following manufacturing method. First, a three-layer pellet of LiMn ₂ O ₄ layer / Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ layer / Li ₄ Ti ₅ O ₁₂ layer is prepared. Thereafter, the three-layer pellet is sintered at 750 ° C. for 12 hours to obtain an electrode. Next, the electrode is polished to a thickness of 10 to 100 μm to produce a solid battery. Here, each layer includes LiBO ₂ -LiF as a sintering aid (mixing molar ratio 44:56).

However, at a low temperature of 750 ° C., the sintering of the three-layer pellet does not proceed sufficiently. For this reason, the bonding between the solid electrolyte and the active material becomes insufficient. Thus, the charge / discharge curve shown in Non-Patent Document 2 shows a very small current value of 10 μA / cm ² . That is, the internal resistance of the solid battery is considered to be very large.
In this case, in order to reduce the internal resistance of the solid state battery, it is conceivable to increase the firing temperature to promote the sintering. However, in this method, the reaction between the solid electrolyte and the active material causes an inactive layer at the interface between them, which may make it difficult to charge and discharge the battery.

  In Patent Document 2, a molded body of a positive electrode material containing a binder, a molded body of a solid electrolyte, and a molded body of a negative electrode material are laminated and sintered by microwave heating to produce a solid battery. It has been proposed. According to Patent Document 2, the molded body may be formed into a sheet shape, or after the raw material slurry is screen-printed on the substrate and dried, the molded body may be produced by removing the substrate. Are listed.

  Furthermore, Patent Document 2 describes that by using microwave heating, the reaction of each particle contained in the electrode and the solid electrolyte layer can be suppressed and the filling rate can be improved. However, in the combination of the active material and the solid electrolyte as described in the example of Patent Document 2, the active material and the solid electrolyte react at a high temperature and the interface does not have Li ion conductivity. A layer is produced. Therefore, even if the heating time by the microwave is shortened, it is difficult to suppress the formation of the inactive layer at the interface between the active material and the solid electrolyte layer. That is, with the method proposed in Patent Document 2, it is difficult to suppress an increase in resistance at the interface between the active material and the solid electrolyte, a decrease in capacity due to the modification of the active material, and the like.

On the other hand, Patent Document 3 discloses a thin film using lithium phosphorous oxynitride (Li _X PO _Y N _Z , where X = 2.8 and 3Z + 2Y = 7.8) as a solid electrolyte. Batteries have been proposed.
When a battery is manufactured by forming a thin film of an active material and a solid electrolyte on a substrate by a technique such as sputtering, the thin film is formed in an amorphous state. Generally used active materials such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , and Li ₄ Ti ₅ O ₁₂ cannot be charged and discharged in an amorphous state. Therefore, when using these active materials, it is necessary to crystallize the thin film by performing a heat treatment at about 400 to 700 ° C. after the thin film is formed.

  However, lithium phosphorous oxynitride is decomposed at about 300 ° C. Therefore, it is difficult to crystallize an active material by heat-treating a laminate in which a positive electrode, a solid electrolyte containing lithium phosphorous oxynitride, and a negative electrode are laminated.

When a solid electrolyte such as heat-resistant Perovskite type Li _0.33 La _0.56 TiO ₃ or NASICON type LiTi ₂ (PO ₄ ) ₃ is used, when heat treatment is performed together with a general active material, the active material and the solid electrolyte Impurities are generated at the interface. Therefore, it is difficult to charge and discharge in the obtained battery.

As described above, a side reaction in which a substance that does not contribute to the charge / discharge reaction is generated proceeds at the interface between the active material and the solid electrolyte. Therefore, it is difficult to form a good active material / solid electrolyte interface while densifying and crystallizing the active material layer and the solid electrolyte layer by heat treatment.
Japanese Patent Application No. 6-231796 Japanese Patent Laid-Open No. 2001-210360 US Pat. No. 5,597,660 Journal of Power Sources, 1999, 81-82, p. 863-866 Solid State Ionics, 1999, 118, p. 149-157

  By the way, a solid battery can also be produced as follows, for example. A solid electrolyte, an active material, and a current collector are dispersed in a solvent containing a binder and a plasticizer to prepare respective slurries. An active material green sheet, a solid electrolyte green sheet, and a current collector green sheet are produced using each slurry. The obtained green sheets are laminated, and then the obtained laminated body is sintered.

  In such a solid battery manufacturing method, it is necessary to perform thermal decomposition (debinding) of the binder and the plasticizer in the presence of oxygen at a temperature of about 300 to 400 ° C. However, if the binder is removed in the presence of high-temperature oxygen, metal materials such as copper and nickel contained in the current collector layer are oxidized, and the internal resistance of the obtained solid battery increases.

  Therefore, an object of the present invention is to provide a manufacturing method for obtaining an all-solid battery having a low internal resistance and a large capacity.

The present invention is a method for producing a solid battery comprising a laminate comprising a solid electrolyte layer, an active material layer, and a current collector layer, wherein the active material powder is dispersed in a solvent containing a binder and a plasticizer, A step of obtaining an active material slurry; a step of dispersing a solid electrolyte powder in a solvent containing a binder and a plasticizer to obtain a solid electrolyte slurry; and a step of dispersing a current collector powder in a solvent containing a binder and a plasticizer A step of obtaining a current collector slurry; a step of forming each of the active material green sheet and the solid electrolyte green sheet using the active material slurry and the solid electrolyte slurry; and a solid electrolyte on one surface of the active material green sheet A green sheet is laminated to obtain a first green sheet group, and a current collector green sheet layer is formed on the other surface of the active material green sheet using a current collector slurry to form a second green sheet. A green sheet group manufacturing process, a second green sheet group is heated in an oxidizing atmosphere at 200 ° C. or higher and 400 ° C. or lower; a heating process; a second green sheet group heated in the heating process is reduced Firing in an oxygen atmosphere at a firing temperature higher than the heating temperature of the heating step to obtain a laminate including a solid electrolyte layer, an active material layer, and a current collector layer; Regarding the method.
The firing temperature in the firing step is preferably 700 ° C. or higher and 1000 ° C. or lower.

  The current collector powder preferably contains at least one selected from the group consisting of copper, nickel, palladium, gold and platinum.

In the firing step, the equilibrium oxygen partial pressure (P1) atm and the firing temperature (T) ° C. in a low oxygen atmosphere are expressed by the following formula:
−0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1
It is preferable to satisfy.

  In the heating step, the oxidizing atmosphere contains oxygen gas, and the equilibrium partial pressure (P2) of the oxygen gas is preferably 0.1 atm or more and 1.0 atm or less.

  The green sheet group production step preferably further includes a cutting step of cutting the first green sheet group or the second green sheet group into a predetermined size.

  The method of the present invention preferably further includes a step of forming an external electrode connected to the current collector layer on the end face of the laminate after the firing step.

  The active material powder preferably contains a first phosphate compound capable of inserting and extracting lithium ions, and the solid electrolyte powder preferably contains a second phosphate compound having lithium ion conductivity.

The first phosphate compound has the following formula (1):
LiMPO ₄ (1)
(In the formula, M is at least one selected from the group consisting of Mn, Fe, Co, and Ni.)
It is preferable to be represented by

The second phosphate compound has the following formula (2):
Li _{1 + X} M ^III _X Ti ^IV _2-X (PO ₄ ) ₃ (2)
(In the formula, M ^III is at least one selected from the group consisting of Al, Y, Ga, In and La, and 0 ≦ X ≦ 0.6.)
It is preferable to be represented by

  In the present invention, after the second green sheet group including the current collector green sheet layer is heated, the second green sheet group is further fired in a low oxygen atmosphere and at a firing temperature higher than the heating temperature in the heating step. For this reason, even when the current collector made of a metal material is oxidized in the heating step, the oxidized current collector can be reduced in the firing step. Thus, since the oxidation of the current collector can be suppressed, the internal resistance of the solid state battery can be reduced.

  The method for producing a solid battery of the present invention is a method for producing a solid battery comprising a laminate comprising a solid electrolyte layer, an active material layer, and a current collector layer, wherein the active material is contained in a solvent containing a binder and a plasticizer. Dispersing powder to obtain an active material slurry; Dispersing solid electrolyte powder in a solvent containing a binder and a plasticizer to obtain a solid electrolyte slurry; and In a solvent containing a binder and a plasticizer A step of dispersing a current collector powder to obtain a current collector slurry; a step of forming an active material green sheet and a solid electrolyte green sheet using the active material slurry and the solid electrolyte slurry, respectively; A solid electrolyte green sheet is laminated on one side to obtain a first green sheet group, and a current collector green sheet is formed on the other side of the active material green sheet using a current collector slurry. Forming a second green sheet group to form a second green sheet group; heating the second green sheet group at 200 ° C. to 400 ° C. in an oxidizing atmosphere; heating the second green sheet group; Firing the two green sheets in a low oxygen atmosphere at a firing temperature higher than the heating temperature of the heating step to obtain a laminate including a solid electrolyte layer, an active material layer, and a current collector layer; including.

(1) First step (preparation of slurry)
In the step of obtaining the active material slurry, the active material powder is dispersed in a solvent containing a binder and a plasticizer to prepare an active material slurry. The average particle diameter of the active material powder is, for example, preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. The content of the binder in the active material slurry is, for example, 5 to 30 parts by weight per 100 parts by weight of the active material powder. The content of the plasticizer is, for example, 1 to 20 parts by weight per 100 parts by weight of the active material powder.

  In the step of obtaining the solid electrolyte slurry, the solid electrolyte powder is dispersed in a solvent containing a binder and a plasticizer to prepare a solid electrolyte slurry. The average particle size of the solid electrolyte powder is preferably, for example, 0.1 to 10 μm, and more preferably 0.5 to 5 μm. The content of the binder in the solid electrolyte slurry is, for example, 5 to 30 parts by weight per 100 parts by weight of the solid electrolyte powder. The content of the plasticizer is, for example, 1 to 20 parts by weight per 100 parts by weight of the solid electrolyte powder.

  The active material powder preferably contains a first phosphate compound that can occlude and release lithium ions. The solid electrolyte preferably contains a second phosphate compound having lithium ion conductivity. However, the first phosphate compound and the second phosphate compound are different phosphate compounds.

The first phosphate compound has the following formula (1):
LiMPO ₄ (1)
(In the formula, M is at least one selected from the group consisting of Mn, Fe, Co, and Ni.)
It is preferable to be represented by Of these compounds, LiCoPO ₄ is more preferable.

The second phosphate compound has the following formula (2):
Li _{1 + X} M ^III _X Ti ^IV _2-X (PO ₄ ) ₃ (2)
(In the formula, M ^III is at least one selected from the group consisting of Al, Y, Ga, In and La, and 0 ≦ X ≦ 0.6.)
It is preferable to be represented by Among these compounds, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ is more preferable.

  By using the first phosphoric acid compound as described above as the active material and the second phosphoric acid compound as described above as the solid electrolyte, the active material layer and the solid electrolyte layer are provided with an inert layer at the interface. Sintering can be performed without generating.

  In the step of obtaining the current collector slurry, the current collector slurry is prepared by dispersing the current collector powder in a solvent containing a binder and a plasticizer. The average particle size of the current collector powder is preferably, for example, 0.1 to 10 μm, and more preferably 0.5 to 5 μm. The content of the binder in the current collector slurry is, for example, 5 to 30 parts by weight per 100 parts by weight of the current collector powder. The content of the plasticizer is, for example, 1 to 20 parts by weight per 100 parts by weight of the current collector powder.

  A metal material having electron conductivity is used for the current collector powder. For example, as the current collector powder, at least one metal material selected from the group consisting of copper, nickel, palladium, gold and platinum can be used.

  The current collector slurry may further contain glass frit or the like having heat-fusibility. When glass frit is used, the softening point of the glass frit is preferably a low temperature of about 400 to 700 ° C. The amount of the glass frit is preferably 0.5 to 15 parts by weight per 100 parts by weight of the current collector powder.

  The binder and the plasticizer may be dispersed in a solvent or may be dissolved. As the binder, for example, polyvinyl butyral resin, methyl cellulose, polyvinyl alcohol, ethyl cellulose, cellulose acetate and the like can be used.

  Examples of the plasticizer include dibutyl phthalate, polyacrylate, polyvinyl acetate, and cellulose acetate. By adding a plasticizer to the green sheet, the green sheet can be given flexibility and elasticity.

  As the solvent, for example, alcohols such as ethanol, n-butyl acetate, ethyl acetate and the like can be used. Of these, n-butyl acetate, ethyl acetate and the like are preferably used.

(2) Second step (formation of green sheet)
In the second step, an active material green sheet and a solid electrolyte green sheet are formed using the active material slurry and the solid electrolyte slurry, respectively. The green sheet can be formed as follows, for example.
The active material slurry is coated on a support having a release agent layer on the surface. Next, the applied active material slurry can be dried to obtain an active material green sheet. Similarly, a solid electrolyte green sheet can be obtained using a solid electrolyte slurry.

  As the support, for example, polyethylene sheets and films can be used.

  The method for applying the slurry is not particularly limited as long as it is a method for obtaining a thin-film active material green sheet and a solid electrolyte green sheet. For example, a doctor blade method is mentioned.

(3) Third step (green sheet group production step)
In the third step, a green sheet group including an active material green sheet, a solid electrolyte green sheet, and a current collector green sheet layer is produced. Such a green sheet group can be produced as follows, for example.
First, an active material green sheet and a solid electrolyte green sheet are laminated to produce a first green sheet group. At this time, the number of active material green sheets may be one, or a plurality of active material green sheets may be continuously stacked. Similarly, the number of solid electrolyte green sheets may be one, or a plurality of solid electrolyte green sheets may be laminated continuously.

  Next, a current collector green sheet layer is formed on the first green sheet group including the active material green sheet and the solid electrolyte green sheet using the current collector slurry to obtain a second green sheet group. Note that a plurality of first green sheet groups may be stacked via the current collector green sheet layer. In that case, it arrange | positions so that the active material layer of the same kind may oppose through a collector green sheet layer.

  The current collector green sheet layer can be formed, for example, by directly applying the current collector slurry to the surface of the active material green sheet opposite to the surface in contact with the solid electrolyte green sheet. Alternatively, the current collector green sheet may be formed using the current collector slurry in the same manner as the method for producing the active material green sheet and the solid electrolyte green sheet. The current collector green sheet layer can be formed by laminating the obtained current collector green sheet on the surface of the active material green sheet opposite to the surface that is in contact with the solid electrolyte green sheet.

(4) Fourth step (heating step)
In the fourth step, the second green sheet group including the active material green sheet, the solid electrolyte green sheet, and the current collector green sheet layer is heated at 200 ° C. to 400 ° C. in an oxidizing atmosphere to remove the binder. (Low temperature heating). By the fourth step, the binder and the plasticizer contained in the active material green sheet, the solid electrolyte green sheet, and the current collector green sheet layer are decomposed and released as gas from the second green sheet group. That is, organic substances are removed from the second green sheet group. Furthermore, since the temperature of the heat treatment (heating temperature) is 200 ° C. or higher and 400 ° C. or lower, the current collector can be prevented from being oxidized. The temperature of the heat treatment is preferably 280 ° C. or higher and 380 ° C. or lower.

  Examples of the gas constituting the oxidizing atmosphere include oxygen gas and air.

In the fourth step, when the oxidizing atmosphere contains oxygen gas, the equilibrium partial pressure (P2) of the oxygen gas is preferably 0.1 atm or more and 1.0 atm or less (1 atm = 1.103 × 10 ⁵ Pa). When the equilibrium partial pressure of oxygen gas is 0.1 atm or more, carbonization of the binder and the plasticizer can be suppressed. This further facilitates the removal of organic substances (binder and plasticizer) from the active material green sheet, solid electrolyte green sheet and current collector green sheet layer. Therefore, sintering and densification of each layer included in the laminated body are not easily inhibited. In addition, self-discharge and internal short circuit derived from the conductivity of carbons generated by the above carbonization hardly occur. On the other hand, when the equilibrium partial pressure P2 of the oxygen gas is 1.0 atm or less, the oxidation of the active material and the solid electrolyte itself can be suppressed. In this case, the oxidizing atmosphere preferably contains an inert gas in addition to the oxygen gas. Examples of the inert gas include nitrogen gas and argon gas.

(5) Fifth step (firing step)
In the fifth step, the second green sheet group heated in the fourth step is fired in a low oxygen atmosphere at a firing temperature higher than the heating temperature in the fourth step (high temperature firing). Part of the metal material contained in the current collector layer may be oxidized in the fourth step. By firing the second green sheet group heated in the fourth step in a low oxygen atmosphere, the oxidized metal material can be reduced. As described above, since the oxidation of the current collector layer can be suppressed, the internal resistance of the solid state battery can be reduced.
In addition, it is preferable to perform a 4th process and a 5th process continuously.

  The firing temperature in the fifth step is preferably 700 ° C. or higher and 1000 ° C. or lower, and more preferably 850 to 950 ° C. When the firing temperature is 700 ° C. or higher, firing proceeds sufficiently, so that each layer included in the laminate can be further densified. Moreover, mutual diffusion of elements at the interface between the active material layer and the solid electrolyte layer can be further suppressed when the firing temperature is 1000 ° C. or lower. Therefore, the composition of the active material and the solid electrolyte is maintained, and a solid battery having good electrochemical characteristics can be obtained.

Furthermore, in the fifth step, the equilibrium oxygen partial pressure (P1) atm and the firing temperature (T) ° C. in a low oxygen atmosphere are expressed by the following equation (3)
−0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 (3)
It is preferable to satisfy. When the equilibrium oxygen partial pressure P1 is large, the current collector may be oxidized. Alternatively, the current collector layer oxidized in the fourth step may not be reduced. If the equilibrium oxygen partial pressure P1 is smaller than the above range, it may be difficult to suppress the generation of carbons in the current collector layer, the solid electrolyte layer, and the active material layer.

  In order to stably adjust the equilibrium oxygen partial pressure P1 within the above range, the low oxygen atmosphere includes at least a gas capable of releasing oxygen gas (for example, carbon dioxide gas) and a gas that reacts with oxygen gas (for example, Hydrogen gas) is preferably included. Examples of such a mixed gas include a mixed gas composed of carbon dioxide gas, hydrogen gas, and nitrogen gas. When the mixed gas contains hydrogen gas, the content of hydrogen gas in the mixed gas is preferably less than 4% by volume, which is the explosion limit concentration of hydrogen gas, for safety. Moreover, it is preferable that content of a carbon dioxide gas is 1-99 volume% of mixed gas.

In the mixed gas composed of carbon dioxide gas, hydrogen gas and nitrogen gas as described above, the following equations (4) and (5):
CO ₂ → CO + 1 / 2O ₂ (4)
H ₂ + 1 / 2O ₂ → H ₂ O (5)
The following reaction occurs. Oxygen gas is generated by the reaction of formula (4), and oxygen gas is consumed by the reaction of formula (5). Therefore, oxygen gas exists in the atmospheric gas, and its partial pressure is It will be maintained at a substantially constant value.

  The filling rate of the active material layer, the solid electrolyte layer, and the current collector layer can be controlled by adjusting the firing temperature in the fifth step, the temperature increase rate at that time, and the like. The rate of temperature increase during firing in the fifth step is preferably 500 ° C./h or more, and more preferably 900 ° C./h or more.

  After the firing step, an external electrode connected to the current collector layer may be formed on the end face of the obtained laminate.

  The laminate after being treated in the firing step is likely to crack during cutting. Therefore, the step of producing the green sheet group preferably includes a cutting step of cutting the first green sheet group or the second green sheet group into a predetermined size.

  The active material layer contained in the laminate produced by the above manufacturing method functions as a positive electrode active material layer in a solid state battery.

As the negative electrode active material, for example, metallic lithium or the like can be used. However, when the solid electrolyte layer and metallic lithium come into contact, the solid electrolyte may be reduced. Therefore, it is preferable to interpose a layer having Li ion conductivity between the metallic lithium and the solid electrolyte layer. Examples of such a layer include a PEO-LiTFSI layer containing polyethylene oxide (PEO) and LiN (SO ₂ CF ₃ ) ₂ (hereinafter referred to as LiTFSI). PEO and LiTFSI are preferably mixed so that the molar ratio of oxygen atoms of PEO to Li in LiTFSI: [O] / [Li] is 10-30. Moreover, the thickness of such a layer should just be 1-10 micrometers.

  Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples.

Example 1
A battery was fabricated by the following process.
(1) First Step LiCoPO ₄ having an average particle diameter of 1 μm was used as the active material powder. 15 parts by weight of polyvinyl butyral resin (binder) (Sleek BM-S manufactured by Sekisui Chemical Co., Ltd.), 7 parts by weight of dibutyl phthalate (plasticizer), and n-butyl acetate (solvent) (Kanto Chemical Co., Ltd.) (Manufactured) 130 parts by weight and 100 parts by weight of the active material powder were mixed. Thereafter, the obtained mixture was mixed with a zirconia ball using a ball mill for 24 hours to obtain an active material slurry.

As the solid electrolyte powder, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ having an average particle diameter of 1 μm was used. Polyvinyl butyral resin (binder) 15 parts by weight, dibutyl phthalate (plasticizer) 7 parts by weight, n-butyl acetate (solvent) 130 parts by weight, and solid electrolyte powder 100 parts by weight were mixed. Thereafter, the obtained mixture was mixed with a zirconia ball using a ball mill for 24 hours to obtain a solid electrolyte slurry.

  As the current collector powder, a copper powder having an average particle size of 1 μm was used. 15 parts by weight of a polyvinyl butyral resin (binder), 7 parts by weight of dibutyl phthalate (plasticizer), 130 parts by weight of n-butyl acetate (solvent), and 100 parts by weight of current collector powder were mixed. Then, the obtained mixture was mixed with a zirconia ball using a ball mill for 24 hours to obtain a current collector slurry.

(2) 2nd process The solid electrolyte slurry was apply | coated using the doctor blade on the carrier film 1 which has a polyester resin as a main component. Thereafter, the applied slurry was dried at 150 ° C. for 30 minutes to form a solid electrolyte green sheet 3 (thickness 25 μm) as shown in FIG. A release agent layer was formed on the surface of the carrier film 1 in advance.
Similarly, a positive electrode active material green sheet 4 (thickness 4 μm) as shown in FIG. 2 was formed on the carrier film 2 using the positive electrode active material slurry.

(3) Third Step As shown in FIG. 3, one surface of a polyester film 6 having an adhesive layer (not shown) on both surfaces thereof was pasted on a stainless steel support base 5. On the other surface of the polyester film 6, the surface of the solid electrolyte green sheet 3 that is not in contact with the carrier film 1 was placed.
A pressure of 100 kg / cm ² was applied from above the carrier film 1 at 80 ° C. Thereafter, as shown in FIG. 4, the carrier film 1 was peeled from the solid electrolyte green sheet 3.
On this solid electrolyte green sheet 3, a solid electrolyte green sheet 3 ′ formed on another carrier film 1 ′ produced in the same manner as described above was placed. From above the carrier film 1 ', temperature and pressure were applied in the same manner as described above. Thereby, the solid electrolyte green sheet 3 and the solid electrolyte green sheet 3 ′ were joined, and the carrier film 1 ′ was peeled off from the solid electrolyte green sheet 3 ′. This operation was repeated 20 times to produce a solid electrolyte green sheet group 7.

  Next, the positive electrode active material green sheet 4 was placed on the solid electrolyte green sheet group 7, and the temperature and pressure were applied from above the carrier film 2 in the same manner as described above. Thereby, the solid electrolyte green sheet group 7 and the positive electrode active material green sheet 4 were joined, and the carrier film 2 was peeled off from the positive electrode green sheet 4. Thus, the first green sheet group 8 shown in FIG. 5 was produced.

  The 1st green sheet group 8 was peeled from the polyester film 6, and it cut | disconnected to the magnitude | size of an area of 7 mm x 7 mm, and produced the green chip. The current collector slurry was applied to the surface of the green sheet of the positive electrode active material of the green chip and dried at 150 ° C. for 30 minutes to form a current collector green sheet layer 9. Thus, the second green sheet group 10 was produced.

(4) Fourth Step As shown in FIG. 6, the second green sheet group 10 was sandwiched between two alumina ceramic plates 11.
After the second green sheet group 10 sandwiched between two ceramic plates was heated in air (equilibrium partial pressure P2 of oxygen gas was 0.2 atm) to 350 ° C. at a temperature increase rate of 400 ° C./h, The organic substance (binder and plasticizer) was thermally decomposed by maintaining at 350 ° C. for 5 hours.

(5) Fifth Step The second green sheet group 10 heated in the fourth step is heated in a reducing gas with CO ₂ / H ₂ / N ₂ = 4.99 / 0.01 / 95 (volume ratio). The temperature was raised to 900 ° C. at 1000 ° C./h, and then immediately cooled at a cooling rate of 1000 ° C./h (calcination temperature T was 900 ° C.). The equilibrium oxygen partial pressure P1 was 10 ⁻¹¹ atm. That is, -logP1 is 11, which satisfies -0.0310T + 33.5≤-logP1≤-0.0300T + 38.1. In this way, a laminate including a solid electrolyte layer, an active material layer, and a current collector layer was obtained.

(6) Production of coin-shaped battery Using the obtained laminate, a coin-shaped battery 70 shown in FIG. 7 was produced as follows. The following steps were performed in dry air with a dew point of −50 ° C. or lower.
First, a metal lithium foil having a thickness of 300 μm was punched out to a diameter of 12 mm to obtain a negative electrode 73. The obtained negative electrode 73 was disposed on the inner bottom surface of the battery case 71 (made of stainless steel).

When the solid electrolyte is in direct contact with metallic lithium, the solid electrolyte is reduced to TiO ₂ . Therefore, a PEO-LiTFSI layer 74 containing polyethylene oxide (PEO) and LiN (SO ₂ CF ₃ ) ₂ (LiTFSI) and having Li ion conductivity was formed on the negative electrode 73 as follows. PEO having an average molecular weight of 1,000,000 and LiTFSI were dissolved in dehydrated acetonitrile so that the molar ratio [O] / [Li] of oxygen atoms of PEO and lithium atoms of LiTFSI was 20/1. In addition, in this solution, it prepared so that the density | concentration of Li might be 0.1 mol / L.
The obtained solution was spin-coated on the negative electrode 73 at 2000 rpm and vacuum-dried to form a PEO-LiTFSI layer 74. The thickness of the PEO-LiTFSI layer 74 was 5 μm.

  Next, the stacked body 78 including the solid electrolyte layer 78a, the positive electrode active material layer 78b, and the current collector layer 78c is disposed on the PEO-LiTFSI layer 74 so that the PEO-LiTFSI layer 74 and the solid electrolyte layer 78a are in contact with each other. did.

  On the current collector layer 78 c of the laminated body 78, a plate plate 75 welded with a disc spring 76 was arranged, and a sealing plate 72 (made of stainless steel) was arranged on the plate plate 75. The open end of the battery case 71 was caulked to the end of the sealing plate 72 via a gasket 77 (made of nylon). In this way, a coin-type battery 70 was produced.

Example 2
A battery was fabricated in the same manner as in Example 1 except that the heating temperature in the fourth step was 200 ° C.

Example 3
A battery was fabricated in the same manner as in Example 1 except that the heating temperature in the fourth step was 400 ° C.

Example 4
In the fourth step, instead of air, a mixed gas (total pressure: 1 atm) composed of 10% by volume of oxygen gas and 90% by volume of argon gas is used as the oxidizing atmosphere, and the equilibrium partial pressure (P2) of oxygen gas in the oxidizing atmosphere is set to 0. A battery was fabricated in the same manner as in Example 1 except that the pressure was set to 1 atm.

Example 5
A battery was fabricated in the same manner as in Example 1, except that, in the fourth step, an oxidizing atmosphere consisting only of oxygen gas was used instead of air, and the equilibrium pressure (P2) of oxygen gas was 1.0 atm.

Example 6
The firing temperature in the fifth step was 700 ° C., and the equilibrium oxygen partial pressure (P1) was 10 ^−15.9 atm (−log P1: 15.9). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 satisfies 11.8 ≦ 15.9 ≦ 17.1, which satisfies this condition. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) is adjusted to 10 ^−15.9 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 4.86 / 0.00947 / 95.13053 (volume ratio). did.

Example 7
The firing temperature in the fifth step was 1000 ° C., and the equilibrium oxygen partial pressure (P1) was 10 ^−5.0 atm (−log P1: 5.0). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 satisfies 2.5 ≦ 5.0 ≦ 8.1, which satisfies this condition. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−5.0 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 99.9985 / 0.0015 / 0 (volume ratio).

Example 8
The baking temperature in the fifth step was 700 ° C., the equilibrium oxygen partial pressure (P1) of 10 ^-11.8 atm (-logP1: 11.8) and the. At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 satisfies 11.8 ≦ 11.8 ≦ 17.1, which satisfies this condition. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−11.8 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 99.9982 / 0.0018 / 0 (volume ratio).

Example 9
The firing temperature in the fifth step was set to 700 ° C., and the equilibrium oxygen partial pressure (P1) was set to 10 ^−17.1 atm (−log P1: 17.1). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 satisfies 11.8 ≦ 17.1 ≦ 17.1, which satisfies this condition. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) is adjusted to 10 ^−17.1 atm in the reducing gas by ^setting CO ₂ / H ₂ / N ₂ = 1.2 / 0.01 / 98.79 (volume ratio). did.

Example 10
The firing temperature in the fifth step was 1000 ° C., and the equilibrium oxygen partial pressure (P1) was 10 ^−2.5 atm (−log P1: 2.5). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 satisfies 2.5 ≦ 2.5 ≦ 8.1, which satisfies this condition. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−2.5 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 99.9999 / 0.0001 / 0 (volume ratio).

Example 11
The firing temperature in the fifth step was set to 1000 ° C., and the equilibrium oxygen partial pressure (P1) was set to 10 ^−8.1 atm (−log P1: 8.1). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 satisfies 2.5 ≦ 8.1 ≦ 8.1, which satisfies this condition. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) is adjusted to 10 ^−8.1 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 18.0 / 0.01 / 89.99 (volume ratio). did.

<< Comparative Example 1 >>
A battery was fabricated in the same manner as in Example 1 except that the heating temperature in the fourth step was 150 ° C.
In the battery of Comparative Example 1, the second green sheet group was not sintered in the fifth step and cracked. For this reason, a battery could not be produced. The reason why the second green sheet was not sintered is considered to be that the heating temperature was low in the fourth step, so that the binder could not be sufficiently removed and the carbonization of the organic matter proceeded.

<< Comparative Example 2 >>
A battery was produced in the same manner as in Example 1 except that the heating temperature in the fourth step was 450 ° C.

Example 12
In the fourth step, instead of air, a mixed gas (total pressure: 1 atm) composed of 5% by volume of oxygen and 95% by volume of argon gas is used as the oxidizing atmosphere, and the equilibrium partial pressure (P2) of oxygen gas in the oxidizing atmosphere is set to 0. 0. A battery was fabricated in the same manner as in Example 1 except that the pressure was 05 atm.

Example 13
The firing temperature in the fifth step was 650 ° C., and the equilibrium oxygen partial pressure P1 was 10 ^−18.8 atm (−log P1: 18.8). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 is not satisfied. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−18.8 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 5 / 0.02 / 94.98 (volume ratio).

Example 14
The firing temperature in the fifth step was 1050 ° C., and the equilibrium oxygen partial pressure (P1) was 10 ^−7.2 atm (−log P1: 7.2). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 is not satisfied. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−7.2 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 5 / 0.01 / 94.99 (volume ratio).

Example 15
The baking temperature in the fifth step was 700 ° C., the equilibrium oxygen partial pressure (P1) of 10 ^-18.0 atm (-logP1: 18.0) and the. At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 is not satisfied. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) is adjusted to 10 ^−18.0 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 0.45 / 0.01 / 99.54 (volume ratio). did.

Example 16
The firing temperature in the fifth step was set to 700 ° C., and the equilibrium oxygen partial pressure (P1) was set to 10 ^−11.7 atm (−log P1: 11.7). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 is not satisfied. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−11.7 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 99.998 / 0.002 / 0 (volume ratio).

Example 17
The firing temperature in the fifth step was 1000 ° C., and the equilibrium oxygen partial pressure (P1) was 10 ^−9.0 atm (−log P1: 9.0). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 is not satisfied. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) is adjusted to 10 ^−9.0 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 6.5 / 0.01 / 93.49 (volume ratio). did.

Example 18
The firing temperature in the fifth step was 1000 ° C., and the equilibrium oxygen partial pressure (P1) was 10 ^−2.4 atm (−log P1: 2.4). At this time, −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1 is not satisfied. A battery was fabricated in the same manner as in Example 1 except for the above. The equilibrium oxygen partial pressure (P1) was adjusted to 10 ^−2.4 atm in the reducing gas by setting CO ₂ / H ₂ / N ₂ = 99.9999 / 0.0001 / 0 (volume ratio).

Example 19
A battery was fabricated in the same manner as in Example 1 except that iron powder (average particle size: 1 μm) was used as the current collector powder.

[Evaluation]
The open circuit voltage of each battery produced as described above was measured after the battery was produced. Each battery was charged and discharged once at a constant current of 1 μA in the range of 3.0 to 5.0 V, and the initial discharge capacity was measured. The results are shown in Table 1.

  The battery of Comparative Example 2 could not be charged. This is probably because the heating temperature in the fourth step is high, so that an inactive side reaction product is generated at the interface between the current collector layer and the positive electrode active material layer, which inhibits the charge / discharge reaction. .

On the other hand, as can be seen from the results of Examples 1 to 3, excellent initial charge / discharge characteristics were obtained when the heating temperature in the fourth step was in the range of 200 to 400 ° C.
The laminates of Example 1 before and after the fourth step were analyzed by X-ray diffraction (XRD) using Cu Kα rays. The X-ray diffraction patterns before and after the heat treatment are shown in FIG. In FIG. 8, the X-ray diffraction pattern after the fourth step is represented by A, and the X-ray diffraction pattern before the fourth step is represented by B. Before and after the fourth step, the position and pattern of the peak attributed to LiCoPO _{4 as the} positive electrode active material were maintained. On the other hand, regarding the current collector, in the X-ray chart of the laminate after the fourth step, in addition to the peak attributed to Cu, the peak attributed to CuO although the intensity is low in the range of 2θ = 35 to 38 °. Appeared. Moreover, since no peaks other than CuO appeared, it can be seen that an inactive side reaction product was not generated at the interface between the current collector and the positive electrode active material. It was also found that a part of Cu (current collector) was oxidized.

  Therefore, it turns out that it is preferable that the heating temperature in a 4th process exists in the range of 200-400 degreeC.

As can be seen from the results of Examples 1, 4 and 5, when the oxygen partial pressure (P2) of the oxidizing atmosphere used in the fourth step is in the range of 0.1 to 1.0 atm, excellent initial charge / discharge Characteristics were obtained.
On the other hand, the battery of Example 12 had an open circuit voltage as low as 2 V, and the initial discharge capacity was lower than that of the battery of Example 1. Since the battery of Example 12 had a low oxygen partial pressure in the fourth step, it seems that debinding (removal of binder and plasticizer) could not be performed sufficiently. Therefore, it is considered that self-discharge occurred due to an internal short circuit derived from the generated carbon, and the initial discharge capacity was lowered. Therefore, the oxygen partial pressure (P2) of the oxidizing atmosphere used in the fourth step is preferably in the range of 0.1 to 1.0 atm.

As can be seen from the results of Examples 1, 6, and 7, when the firing temperature in the fifth step is in the range of 700 to 1000 ° C., excellent initial charge / discharge characteristics were obtained.
In contrast, the battery of Example 13 had a lower initial discharge capacity than that of the battery of Example 1. This is probably because the firing temperature in the fifth step was low and firing was not sufficiently performed.

The battery of Example 14 has an open circuit voltage as low as 2 V, and the initial discharge capacity is lower than that of the battery of Example 1. In the battery of Example 14, the color of the positive electrode active material (LiCoPO ₄ ) layer after sintering becomes lighter than deep purple, which is the color of the positive electrode active material layer included in the battery of Example 1, and the solid electrolyte layer The color of the portion in contact with the positive electrode active material layer was slightly purple. From this, since the firing temperature in the fifth step was high, the constituent atoms of LiCoPO _{4 and} the constituent atoms of the solid electrolyte diffused, and an inactive layer was generated at the interface between the solid electrolyte and the active material. It is thought that it decreased. Therefore, the firing temperature in the fifth step is preferably in the range of 700 to 1000 ° C.

As can be seen from the results of Examples 6, 8, and 9, when the firing temperature in the fifth step is 700 ° C., the equilibrium oxygen partial pressure (P1) in the low oxygen atmosphere is in the range of 10 ^−17.1 ≦ P1 ≦ 10 ^−11.1 atm. (That is, satisfying −0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1), a battery having more excellent initial charge / discharge characteristics was obtained.

As can be seen from the results of Examples 7, 10 and 11, when the firing temperature in the fifth step is 1000 ° C., the equilibrium oxygen partial pressure P1 is in the range of 10 ^−8.1 ≦ P1 ≦ 10 ^−2.5 atm (that is, − When 0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1), a battery having more excellent initial charge / discharge characteristics was obtained.
In contrast, the batteries of Examples 15 and 17 had an open circuit voltage as low as 2 V, and the initial discharge capacity was lower than that of the battery of Example 1. This is presumably because the oxygen partial pressure P1 in the low oxygen atmosphere used in the fifth step was remarkably low, so that the binder could not be removed sufficiently and self-discharge occurred due to the generated carbon.

  The initial discharge capacities of the batteries of Example 16 and Example 18 were significantly lower than those of the battery of Example 1. About the laminated body contained in the battery of Example 16 and 18, after using for a 4th process, when the XRD measurement was performed similarly to Example 1, the peak attributed to Cu was hardly seen but it belonged to CuO. The intensity of the peak to be increased. Furthermore, most of the current collector was oxidized, and even when calcination was performed in a low oxygen atmosphere in the fifth step, the current collector was not sufficiently reduced and remained oxidized. For this reason, the batteries of Example 16 and Example 18 are considered to have an increased open circuit voltage and a reduced capacity.

As can be seen from the results of Example 1, when Cu was used as the current collector, excellent initial charge / discharge characteristics were obtained. On the other hand, the open circuit voltage and the initial discharge capacity of the battery of Example 19 in which Fe was used as the current collector were slightly small. When the XRD measurement was performed on the laminate included in the battery of Example 19 in the same manner as in Example 1, the peak attributed to Fe was hardly observed, and the intensity of the peak attributed to Fe ₂ O ₃ was high. It was. Furthermore, a peak derived from a side reaction material, which was considered to be generated by the reaction between iron as the current collector and the active material, was confirmed. Therefore, the reason for the decrease in the battery capacity of Example 19 is that most of the current collector is oxidized, and the current collector and the positive electrode active material react to form a current between the current collector layer and the positive electrode active material layer. This is probably because a side reaction product layer was formed between them.

  In the above embodiment, the case where the copper powder is used as the current collector powder is described. However, the effect of the present invention can be achieved even when the current collector powder made of nickel, palladium, gold, and / or platinum is used. Was confirmed.

Further, the above embodiment is used LiCoPO ₄ as an active material, even when using _{LiMn 0.5 Fe 0.5 PO 4, LiFePO} 4, the effect of the present invention was confirmed.

Further, in the above examples, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ was used as the solid electrolyte, but even when Li _1.3 Y _0.3 Ti _1.7 (PO ₄ ) ₃ was used, the effect of the present invention was confirmed. did it.

  According to the present invention, the solid electrolyte layer, the active material layer, and the current collector layer can be densified and crystallized. In addition, a laminate having an interface between an electrochemically active active material and a solid electrolyte can be formed. Furthermore, the oxidation of the current collector in the binder removal during the production of the stacked battery can be suppressed. Therefore, it is possible to provide a manufacturing method for obtaining an all-solid battery having a low internal resistance and a large capacity.

It is a longitudinal cross-sectional view which shows schematically the solid electrolyte green sheet formed on the carrier film. It is a longitudinal cross-sectional view which shows schematically the active material green sheet formed on the carrier film. It is a longitudinal cross-sectional view which shows schematically the solid electrolyte green sheet and carrier film which were mounted on the support body provided with a polyester film. It is a longitudinal cross-sectional view which shows roughly the state by which the carrier film was peeled off from the solid electrolyte green sheet mounted on the support body. It is a longitudinal section showing roughly the state where 20 solid electrolyte green sheets and one active material green sheet were put on a support provided with a polyester film. It is a longitudinal cross-sectional view which shows roughly the state which pinched | interposed the 2nd green sheet group between the ceramic plates. It is a longitudinal cross-sectional view which shows roughly the coin-type battery produced in the Example. It is an X-ray-diffraction pattern figure of the 2nd green sheet group produced in Example 1 before heat-processing at a heating process (B) and after heat processing (A).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Carrier film 3 Solid electrolyte green sheet 4 Positive electrode active material green sheet 5 Support body 6 Polyester film 7 Solid electrolyte green sheet group 8 1st green sheet group 9 Current collector green sheet layer 10 2nd green sheet group 11 Ceramic board 70 coin-type battery 71 battery case 72 sealing plate 73 negative electrode 74 PEO-LiTFSI layer 75 countersink 76 disc spring 77 gasket 78 laminate 78a solid electrolyte layer 78b positive electrode active material layer 78c current collector layer

Claims (10)

A method for producing a solid battery comprising a laminate including a solid electrolyte layer, an active material layer, and a current collector layer,
A step of dispersing an active material powder in a solvent containing a binder and a plasticizer to obtain an active material slurry;
Dispersing a solid electrolyte powder in a solvent containing a binder and a plasticizer to obtain a solid electrolyte slurry;
Dispersing the current collector powder in a solvent containing a binder and a plasticizer to obtain a current collector slurry;
Using the active material slurry and the solid electrolyte slurry to form an active material green sheet and a solid electrolyte green sheet,
The solid electrolyte green sheet is laminated on one surface of the active material green sheet to obtain a first green sheet group, and the current collector slurry is used on the other surface of the active material green sheet to collect a current collector. Forming a green sheet layer to obtain a second green sheet group;
Heating the second green sheet group at 200 ° C. or more and 400 ° C. or less in an oxidizing atmosphere;
The second green sheet group heated in the heating step is fired at a firing temperature higher than the heating temperature of the heating step in a low oxygen atmosphere, and includes a solid electrolyte layer, an active material layer, and a current collector layer Obtaining a body, firing step;
A method for producing a solid state battery.   The method for producing a solid battery according to claim 1, wherein a firing temperature in the firing step is 700 ° C. or higher and 1000 ° C. or lower.   The method for producing a solid state battery according to claim 1, wherein the current collector powder contains at least one selected from the group consisting of copper, nickel, palladium, gold, and platinum. In the firing step, the equilibrium oxygen partial pressure (P1) atm and the firing temperature (T) ° C. in the low oxygen atmosphere are expressed by the following formula:
−0.0310T + 33.5 ≦ −logP1 ≦ −0.0300T + 38.1
The manufacturing method of the solid battery of Claim 1 which satisfy | fills.   2. The method of manufacturing a solid state battery according to claim 1, wherein, in the heating step, the oxidizing atmosphere contains oxygen gas, and an equilibrium partial pressure (P2) of the oxygen gas is 0.1 atm or more and 1.0 atm or less.   The method for producing a solid state battery according to claim 1, wherein the green sheet group manufacturing step further includes a cutting step of cutting the first green sheet group or the second green sheet group into a predetermined size.   The method for producing a solid state battery according to claim 1, further comprising a step of forming an external electrode connected to the current collector layer on an end face of the laminate after the firing step.   The method for producing a solid state battery according to claim 1, wherein the active material powder includes a first phosphate compound capable of inserting and extracting lithium ions, and the solid electrolyte powder includes a second phosphate compound having lithium ion conductivity. . The first phosphoric acid compound has the following formula (1):
LiMPO ₄ (1)
(In the formula, M is at least one selected from the group consisting of Mn, Fe, Co, and Ni.)
The manufacturing method of the solid battery of Claim 8 represented by these. The second phosphate compound has the following formula (2):
Li _{1 + X} M ^III _X Ti ^IV _2-X (PO ₄ ) ₃ (2)
(In the formula, M ^III is at least one selected from the group consisting of Al, Y, Ga, In and La, and 0 ≦ X ≦ 0.6.)
The manufacturing method of the solid battery of Claim 8 represented by these.

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