Patent Application
20230369688
The embodiment discussed herein relates to a solid-state battery and a solid-state battery manufacturing method.
Solid-state batteries in which a solid electrolyte is used as an electrolyte in place of an electrolyte solution are known. A technique for covering the surface of a battery element in which a solid electrolyte layer is located between a positive electrode layer and a negative electrode layer opposite each other with a protection layer containing a high polymer is known regarding the solid-state batteries. Furthermore, a technique for covering the surface of a battery element with a protection layer made of an insulating material other than resin is known. In this case, a crack or falling off caused by adsorbing moisture or gas is less likely to occur, bonding strength between the battery element and the protection layer is high, and falling off caused by vibration, shock, or the like is less likely to occur, compared with the protection layer containing a high polymer. In addition, a technique for using glass or a ceramic as such an insulating material is known.
By the way, a solid-state battery in which a solid-state battery body including an electrolyte layer and a positive electrode layer and a negative electrode layer partially formed on both principal planes of the electrolyte layer is covered with a protection layer formed by the use of a solid electrolyte is known. With a solid-state battery in which a solid electrolyte is used in this way as a protection layer, however, it may be that sufficient strength is not obtained depending on implementation or environment in which it is used. Lack of the strength of a solid-state battery may lead to a crack or a chip in the protection layer or, for example, entrance of moisture or gas into the inside of the solid-state battery caused by the crack or the chip. As a result, the performance of the solid-state battery may deteriorate.
According to an aspect, there is provided a solid-state battery including a laminated body having an electrolyte layer containing a solid electrolyte, a positive electrode layer provided on a part of a first principal plane of the electrolyte layer, and a negative electrode layer provided on a part of a second principal plane of the electrolyte layer opposite to the first principal plane and an insulating coating film which covers the laminated body so as to expose a first portion of the positive electrode layer and a second portion of the negative electrode layer and which has a hardness higher than a hardness of the solid electrolyte.
The object and advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the disclosure.
(Solid-State Battery)
A solid-state battery 1 illustrated in
The solid-state battery body 10 includes an electrolyte layer 13, a positive electrode layer 11 laminated on one principal plane 13a (also referred to as a first principal plane) of the electrolyte layer 13, and a negative electrode layer 12 laminated on the other principal plane 13b (also referred to as a second principal plane) of the electrolyte layer 13 opposite to the principal plane 13a. The solid-state battery body 10 is an example of a laminated body of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12.
The electrolyte layer 13 contains a solid electrolyte. An oxide solid electrolyte is used as the solid electrolyte contained in the electrolyte layer 13. For example, LAGP which is a kind of Na super ionic conductor (NASICON) type oxide solid electrolyte is used for forming the electrolyte layer 13. LAGP is an oxide solid electrolyte expressed by the general formula Li1+xAlxGe2−x(PO4)3 (0<x≤1) and is referred to as aluminum-substituted germanium lithium phosphate or the like. For example, Li1.5Al0.5Ge1.5(PO4)3 obtained in the case of composition ratio x=0.5 in the above general formula is used as LAGP used for forming the electrolyte layer 13.
The positive electrode layer 11 laminated on the one principal plane 13a of the electrolyte layer 13 contains a positive electrode active material. For example, lithium cobalt pyrophosphate (Li2CoP2O7; hereinafter this will be referred to as “LCPO”) is used as the positive electrode active material contained in the positive electrode layer 11. The positive electrode layer 11 may contain not only the positive electrode active material but also a solid electrolyte and a conductive assistant. For example, the oxide solid electrolyte used for forming the electrolyte layer 13 and a material used as the solid electrolyte contained in the positive electrode layer 11 are of the same kind. That is to say, in this example LAGP is used as an oxide solid electrolyte contained in the positive electrode layer 11. A carbon material, such as carbon fiber, carbon black, graphite, graphene, or carbon nanotube, is used as the conductive assistant contained in the positive electrode layer 11.
The negative electrode layer 12 laminated on the other principal plane 13b of the electrolyte layer 13 contains a negative electrode active material. For example, titanium oxide (TiO2) is used as the negative electrode active material contained in the negative electrode layer 12. The negative electrode layer 12 may contain not only the negative electrode active material but also a solid electrolyte and a conductive assistant. For example, the oxide solid electrolyte used for forming the electrolyte layer 13 and a material used as the solid electrolyte contained in the negative electrode layer 12 are of the same kind. That is to say, in this example LAGP is used as an oxide solid electrolyte contained in the negative electrode layer 12. A carbon material, such as carbon fiber, carbon black, graphite, graphene, or carbon nanotube, is used as the conductive assistant contained in the negative electrode layer 12.
In the solid-state battery body 10 which is a laminated body of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12, the positive electrode layer 11 is formed on part of the principal plane 13a of the electrolyte layer 13, the negative electrode layer 12 is formed on part of the principal plane 13b of the electrolyte layer 13, and the positive electrode layer 11 and the negative electrode layer 12 overlap each other with the electrolyte layer 13 therebetween.
In the solid-state battery body 10 lithium ions are conducted from the positive electrode layer 11 via the electrolyte layer 13 to the negative electrode layer 12 and are taken in, at charging time. At discharging time, lithium ions are conducted from the negative electrode layer 12 via the electrolyte layer 13 to the positive electrode layer 11 and are taken in. In the solid-state battery body 10 charging and discharging operations are realized by the above lithium ion conduction.
The coating film 20 covers the solid-state battery body 10 so as to expose part of the positive electrode layer 11 of the solid-state battery body 10 and part of the negative electrode layer 12 of the solid-state battery body 10. In this example the coating film 20 covers the solid-state battery body 10 so as to expose a portion 11a (also referred to as a first portion) of a side of the positive electrode layer 11 and a portion 12a (also referred to as a second portion) of a side of the negative electrode layer 12. The portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 are opposite each other in a direction perpendicular to the direction in which the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 are laminated. The portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 exposed from the coating film 20 are used for electrical connection with the outside of the solid-state battery body 10. In this case, a side of the solid-state battery 1 on which the portion 11a of the positive electrode layer 11 is exposed from the coating film 20 will be referred to as a positive electrode lead surface 1a and a side of the solid-state battery 1 on which the portion 12a of the negative electrode layer 12 is exposed from the coating film 20 will be referred to as a negative electrode lead surface 1b.
The positive electrode layer 11 is formed on the part of the principal plane 13a of the electrolyte layer 13. The coating film 20 covers the solid-state battery body 10 so as to be in contact with the other part of the principal plane 13a of the electrolyte layer 13 and the surface of the positive electrode layer 11 except the portion 11a exposed on the positive electrode lead surface 1a. The negative electrode layer 12 is formed on the part of the principal plane 13b of the electrolyte layer 13. The coating film 20 covers the solid-state battery body 10 so as to be in contact with the other part of the principal plane 13b of the electrolyte layer 13 and the surface of the negative electrode layer 12 except the portion 12a exposed on the negative electrode lead surface 1b. Furthermore, the coating film 20 covers the solid-state battery body 10 so as to be in contact with sides (surfaces which connect the principal plane 13a and the principal plane 13b) of the electrolyte layer 13 except the positive electrode lead surface 1a and the negative electrode lead surface 1b.
An insulating coating film 20 having hardness higher than that of the solid electrolytes used in the solid-state battery body 10 is used as the coating film 20 which covers the solid-state battery body 10 so as to expose the portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 on the positive electrode lead surface 1a and the negative electrode lead surface 1b, respectively, of the solid-state battery 1. For example, an insulating coating film 20 having hardness higher than that of the solid electrolyte used in the electrolyte layer 13. Alternatively, an insulating coating film 20 having hardness higher than that of the solid electrolyte used in the electrolyte layer 13, the solid electrolyte used in the positive electrode layer 11, and the solid electrolyte used in the negative electrode layer 12 is used. The insulating property of the coating film 20 is such that lithium ion conduction or electron conduction in the solid-state battery body 10 is not affected or is affected sufficiently slightly. For example, glass or a ceramic is used for forming the insulating coating film 20 having hardness higher than that of the solid electrolytes used in the solid-state battery body 10.
The coating film 20 has the function of protecting the solid-state battery body 10 against force applied from the outside or from an external environment. Accordingly, a coating film which has the above hardness and insulating property, which has low permeability to moisture or gas, such as hydrogen or oxygen, and which realizes good sealability is used as the coating film 20. Furthermore, it is desirable to use as the coating film 20 a coating film having a thermal expansion coefficient which is approximately the same as that of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 of the solid-state battery body 10 and to use as the coating film 20 a coating film having good adhesion to each layer. Glass or a ceramic is a kind of material having these properties and is suitable as a material used for forming the coating film 20 which covers the solid-state battery body 10.
For example, the solid-state battery 1 having the above structure is manufactured in accordance with the following procedure. First a structural body is formed. The structural body includes the solid-state battery body 10 having the electrolyte layer 13 and the positive electrode layer 11 and the negative electrode layer 12 laminated on the principal plane 13a and the principal plane 13b, respectively, of the electrolyte layer 13 and a material (referred to as a “coating material”) which covers the solid-state battery body 10 so as to expose the portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 used for electrical connection with the outside. Furthermore, the structural body is burned at a determined temperature (also referred to as a first temperature). The coating material which covers the solid-state battery body 10 is sintered by this burning and the insulating coating film 20 having hardness higher than that of the solid electrolytes used in the solid-state battery body 10 is formed from the coating material.
For example, when this burning is performed, the solid electrolytes used in the solid-state battery body 10 may be sintered and the coating material which covers the solid-state battery body 10 may be sintered. As a result, the coating film 20 is formed. That is to say, materials which are equal or approximately equal in sintering temperature may be used as the solid electrolytes used in the solid-state battery body 10 and the coating material which covers the solid-state battery body 10, and the solid electrolytes and the coating material may be sintered in block by performing burning under one condition.
As stated above, with the solid-state battery 1, the solid-state battery body 10 is covered with the coating film 20 having hardness higher than that of the solid electrolytes used in the solid-state battery body 10 so that the portion 11a of the positive electrode layer 11 will be exposed on the positive electrode lead surface 1a and so that the portion 12a of the negative electrode layer 12 will be exposed on the negative electrode lead surface 1b. The coating film 20 is used as a protection layer of the solid-state battery body 10. This suppresses the appearance of a crack or a chip caused by force applied from the outside, compared with a case where, for example, a solid electrolyte is used as a protection layer. In addition, entrance of moisture or gas through a crack portion or a chip portion is effectively suppressed and deterioration in the performance of the solid-state battery 1, such as a short circuit or an increase in resistance, caused by entrance of moisture or gas is effectively suppressed.
With the solid-state battery 1, part of the above coating film 20 having high hardness is formed on a portion of the principal plane 13a of the electrolyte layer 13 on which the positive electrode layer 11 is not formed and a portion of the principal plane 13b of the electrolyte layer 13 on which the negative electrode layer 12 is not formed, that is to say, on portions of the electrolyte layer 13 which are inwardly depressed from the sides. The coating film 20 is formed on an irregular surface of the solid-state battery body 10. This increases bonding strength between the coating film 20 and the solid-state battery body 10 and effectively suppresses peeling of the coating film 20 off the solid-state battery body 10.
By using the above coating film 20 as a protection layer of the above solid-state battery body 10, the solid-state battery 1 which is excellent in strength and environment resistance is realized.
Furthermore, with the solid-state battery 1 the coating film 20 is formed by the use of a material which is approximately equal in thermal expansion coefficient to each layer of the solid-state battery body 10. This suppresses interlayer peeling caused by expansion and contraction of each layer in an external temperature environment. In addition, with the solid-state battery 1 a coating film having good adhesion to each layer of the solid-state battery body 10 is used as the coating film 20. This suppresses peeling of the coating film 20 off the solid-state battery body 10 which may occur when force is applied from the outside or when each layer expands and contracts. Moreover, with the solid-state battery 1 the coating film 20 is formed by the use of a material sintered at a relatively low temperature, for example, at a temperature equal to or lower than 900° C. For example, the coating film 20 is formed by the use of a material sintered at a temperature equal to or lower than 650° C. This sintering temperature is the same or approximately the same with a solid electrolyte. This suppresses thermal degradation of the solid-state battery body 10 caused by the formation of the coating film 20. Furthermore, an increase in man-hours is suppressed by sintering the coating material and the solid electrolytes in block. By adopting the above coating film 20, the solid-state battery 1 which is excellent in strength and environment resistance is also realized. In addition, the solid-state battery 1 is efficiently manufactured.
(Configuration Example of Solid-State Battery)
A configuration example of a solid-state battery will now be described.
A solid-state battery 1A illustrated in
As illustrated in
For example, an electrolyte layer containing LAGP, which is an oxide solid electrolyte, is used as each electrolyte layer 13 of the solid-state battery body 10A. For example, a positive electrode layer containing LCPO, which is a positive electrode active material, LAGP, which is an oxide solid electrolyte, and a carbon material, which is a conductive assistant, is used as each positive electrode layer 11 of the solid-state battery body 10A. For example, a negative electrode layer containing TiO2, which is a negative electrode active material, LAGP, which is an oxide solid electrolyte, and a carbon material, which is a conductive assistant, is used as each negative electrode layer 12 of the solid-state battery body 10A.
In the solid-state battery body 10A lithium ions are conducted from a positive electrode layer 11 through an electrolyte layer 13 to a negative electrode layer 12 and are taken in, at charging time. At discharging time, lithium ions are conducted from the negative electrode layer 12 through the electrolyte layer 13 to the positive electrode layer 11 and are taken in. In the solid-state battery body 10A charging and discharging operations are realized by the above lithium ion conduction between the positive electrode layer 11 and the negative electrode layer 12 opposite each other through the electrolyte layer 13 intervening between them.
As illustrated in
The positive electrode layer 11 is formed on part of the principal plane 13a of the electrolyte layer 13. As illustrated in
An insulating coating film 20A having hardness higher than that of the solid electrolyte used in the solid-state battery body 10A is used as the coating film 20A. For example, an insulating coating film 20A having hardness higher than that of the solid electrolyte contained in the electrolyte layer 13 or the solid electrolytes used in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 is used as the coating film 20A. A coating film which has high hardness and an insulating property, which has low permeability to moisture or gas, such as hydrogen or oxygen, and which realizes good sealability is used as the coating film 20A. Furthermore, it is desirable to use as the coating film 20A a coating film having a thermal expansion coefficient which is approximately the same as that of each layer included in the solid-state battery body 10A and to use as the coating film 20 a coating film having good adhesion to each layer. Glass, a ceramic, or the like is used for forming the coating film 20A.
As illustrated in
As stated above, with the solid-state battery 1A the solid-state battery body 10A except the positive electrode lead surface 1Aa and the negative electrode lead surface 1Ab is covered with the coating film 20A having hardness higher than that of the solid electrolytes used in the solid-state battery body 10A. This suppresses the appearance of a crack or a chip in the coating film 20A caused by force applied from the outside. In addition, entrance of moisture or gas through a crack portion or a chip portion is effectively suppressed and deterioration in the performance of the solid-state battery 1A, such as a short circuit or an increase in resistance, caused by entrance of moisture or gas is effectively suppressed.
With the solid-state battery 1A part of the coating film 20A is formed on the portions of the electrolyte layer 13 which are inwardly depressed from the sides. As a result, an anchor effect is obtained. This effectively suppresses peeling of the coating film 20A off the solid-state battery body 10A.
Furthermore, part of the coating film 20A is formed in a portion in the positive electrode lead surface 1Aa inwardly depressed from the sides of the electrolyte layers 13 which are paired opposite each other with the negative electrode layer 12 therebetween. This enhances strength between the electrolyte layers 13 paired and strengthens the support of the positive electrode layers 11 laminated on the electrolyte layers 13. As a result, the strength of the positive electrode layers 11 on the positive electrode lead surface 1Aa is enhanced and the appearance of a crack or a chip is suppressed. Similarly, part of the coating film 20A is formed in a portion in the negative electrode lead surface 1Ab inwardly depressed from the sides of the electrolyte layers 13 which are paired opposite each other with the positive electrode layer 11 therebetween. This enhances strength between the electrolyte layers 13 paired and strengthens the support of the negative electrode layers 12 laminated on the electrolyte layers 13. As a result, the strength of the negative electrode layers 12 on the negative electrode lead surface 1Ab is enhanced and the appearance of a crack or a chip is suppressed.
By using the above coating film 20A as a protection layer of the above solid-state battery body 10A, the solid-state battery 1A which is excellent in strength and environment resistance is realized.
Furthermore, with the solid-state battery 1A the coating film 20A is formed by the use of a material which is approximately equal in thermal expansion coefficient to each layer of the solid-state battery body 10A. This suppresses interlayer peeling caused by expansion and contraction of each layer in an external temperature environment. In addition, with the solid-state battery 1A a coating film having good adhesion to each layer of the solid-state battery body 10A is used as the coating film 20A. This suppresses peeling of the coating film 20A off the solid-state battery body 10A which may occur when force is applied from the outside or when each layer expands and contracts. By using this coating film 20A, the solid-state battery 1A which is excellent in strength and environment resistance is also realized.
For example, to manufacture the solid-state battery 1A, first a structural body is formed. The structural body includes the solid-state battery body 10A having the electrolyte layer 13 and the positive electrode layer 11 and the negative electrode layer 12 laminated on the principal plane 13a and the principal plane 13b, respectively, of the electrolyte layer 13 and a coating material which covers the solid-state battery body 10A so as to expose the portion 11a of the positive electrode layer 11 and the portion 12a of the negative electrode layer 12 connected to the external electrode 31 and the external electrode 32 respectively. Furthermore, the structural body is burned at a determined temperature (also referred to as a first temperature). By doing so, the coating material which covers the solid-state battery body 10A is sintered and the coating film 20A is formed. If a material sintered at a relatively low temperature, for example, at a temperature equal to or lower than 900° C. is used as the coating material, for example, if a material sintered at a temperature equal to or lower than 650° C. is used as the coating material, then thermal degradation of the solid-state battery body 10A caused by the formation of the coating film 20A is suppressed. In addition, if a material which is equal or approximately equal in sintering temperature to the solid electrolytes used in the solid-state battery body 10A is used as the coating material, then the solid electrolytes and the coating material are sintered in block by performing burning under one condition. The details of a method for manufacturing the solid-state battery 1A will be described later.
Glass, a ceramic, or the like is used as the coating film 20A formed by burning the coating material. The coating film 20A may take various forms. For example, the coating film 20A may take the form of glass, crystalline glass, polycrystalline, a single crystal, or the like. The coating film 20A may contain one material phase or two or more material phases. The coating film 20A may contain two or more material phases which differ in physical property, for example, which differ in hardness.
As illustrated in
The coating film 20A contains the material phase 21 of glass or a ceramic in which the material phase 22 having hardness higher than that of the material phase 21 is contained. By adopting this coating film 20A, hardness as the coating film 20A is enhanced further, compared with a case where the coating film 20A contains only the material phase 21. Because the solid-state battery body 10A is covered with this coating film 20A, the solid-state battery 1A which is excellent in strength and environment resistance is realized.
(Solid-State Battery Manufacturing Method)
A method for manufacturing a solid-state battery having the above structure will now be described.
First an example of the formation of each of an electrolyte paste, a positive electrode paste, a negative electrode paste, and a coating material paste and a coating material sheet will be described.
(Electrolyte Paste)
An electrolyte paste containing a solid electrolyte, a binder, a plasticizer, a dispersant, and a diluent is prepared. For example, an electrolyte paste containing LAGP, which is an oxide solid electrolyte, as a solid electrolyte is prepared.
(Positive Electrode Paste)
A positive electrode paste containing a positive electrode active material, a solid electrolyte, a conductive assistant, a binder, a plasticizer, a dispersant, and a diluent is prepared. For example, a positive electrode paste containing LCPO as a positive electrode active material, LAGP, which is an oxide solid electrolyte, as a solid electrolyte, and a carbon nanofiber as a conductive assistant is prepared.
(Negative Electrode Paste)
A negative electrode paste containing a negative electrode active material, a solid electrolyte, a conductive assistant, a binder, a plasticizer, a dispersant, and a diluent is prepared. For example, a negative electrode paste containing TiO2 as a negative electrode active material, LAGP, which is an oxide solid electrolyte, as a solid electrolyte, and a carbon nanofiber as a conductive assistant is prepared.
(Coating Material Paste and Coating Material Sheet)
A glass paste containing a glass component is prepared as a coating material paste. For example, a glass paste containing a glass component referred to as low melting point glass melted and sintered by performing burning at a temperature of about 600° C. is prepared. By painting and drying the prepared glass paste, a glass sheet as a coating material sheet is formed. A coating material paste and a coating material sheet are a form of a coating material formed as the coating film 20A by burning.
A material having hardness after burning higher than that of the solid electrolytes contained in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 after burning is used as a coating material paste and a coating material sheet. Furthermore, it is desirable to use as a coating material paste and a coating material sheet a material after burning which is approximately equal in thermal expansion coefficient to the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 after burning. In addition, it is desirable to use as a coating material paste and a coating material sheet a material after burning which has good adhesion to the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 after burning. Moreover, a ceramic material, such as Al2O3 in the form of particles, may be added to a coating material paste and a coating material sheet. In this case, a glass component contained in the coating material paste and the coating material sheet is a first material phase and the ceramic material, such as Al2O3 in the form of particles, is a second material phase.
A first example of forming a structural body by the use of the electrolyte paste, the positive electrode paste, the negative electrode paste, and the coating material paste and the coating material sheet prepared in the above way will now be described by reference to
(Formation of Positive Electrode Layer Part)
For example, a polyethylene terephthalate (PET) film is used as a support 50 illustrated in
Next, as illustrated in
For example, by performing the subprocesses illustrated in
When the positive electrode layer part is formed, coating the support 50 with the positive electrode paste and coating the periphery of the positive electrode layer 11 with the coating material paste may be performed alternately and repetitively more than one time in order to, for example, adjust the thickness of the positive electrode layer 11 and the amount of the active material. In this case, drying the positive electrode paste and drying the coating material paste may be performed each time after coating. Alternatively, drying the positive electrode paste and drying the coating material paste may be performed in block after coating the support 50 with the positive electrode paste and coating the periphery of the positive electrode layer 11 with the coating material paste are performed more than one time.
Furthermore, when the positive electrode layer part is formed, coating the positive electrode layer 11 and the part of the coating material layer 24 formed therearound with the electrolyte paste and coating the part of the coating material layer 24 with the coating material paste may be performed alternately and repetitively more than one time in order to, for example, adjust the thickness of the electrolyte layer 13. In this case, drying the electrolyte paste and drying the coating material paste may be performed each time after coating. Alternatively, drying the electrolyte paste and drying the coating material paste may be performed in block after coating the positive electrode layer 11 and the part of the coating material layer 24 formed therearound with the electrolyte paste and coating the part of the coating material layer 24 with the coating material paste are performed more than one time.
In addition, in the example illustrated in
(Formation of Negative Electrode Layer Part)
As illustrated in
Next, as illustrated in
For example, by performing the subprocesses illustrated in
When the negative electrode layer part is formed, coating the support 50 with the negative electrode paste and coating the periphery of the negative electrode layer 12 with the coating material paste may be performed alternately and repetitively more than one time in order to, for example, adjust the thickness of the negative electrode layer 12 and the amount of the active material. In this case, drying the negative electrode paste and drying the coating material paste may be performed each time after coating. Alternatively, drying the negative electrode paste and drying the coating material paste may be performed in block after coating the support 50 with the negative electrode paste and coating the periphery of the negative electrode layer 12 with the coating material paste are performed more than one time.
Furthermore, when the negative electrode layer part is formed, coating the negative electrode layer 12 and the part of the coating material layer 24 formed therearound with the electrolyte paste and coating the part of the coating material layer 24 with the coating material paste may be performed alternately and repetitively more than one time in order to, for example, adjust the thickness of the electrolyte layer 13. In this case, drying the electrolyte paste and drying the coating material paste may be performed each time after coating. Alternatively, drying the electrolyte paste and drying the coating material paste may be performed in block after coating the negative electrode layer 12 and the part of the coating material layer 24 formed therearound with the electrolyte paste and coating the part of the coating material layer 24 with the coating material paste are performed more than one time.
In addition, in the example illustrated in
(Formation of Structural Body)
For example, the positive electrode layer part in a determined form and the negative electrode layer part in a determined form obtained in the above way are laminated in a way illustrated in
When the structural body 5 is formed in this way, the positive electrode layer part and the negative electrode layer part are laminated so that the negative electrode layer 12 and the positive electrode layer 11 opposite each other with the electrolyte layer 13 therebetween will overlap in the section illustrated in
The positive electrode layer part and the negative electrode layer part are laminated so that one of the negative electrode layer 12 and the positive electrode layer 11 opposite each other with the electrolyte layer 13 therebetween will wholly be superimposed over the other is realized in a section perpendicular to the section illustrated in
By performing the process illustrated in
A second example of forming a structural body by the use of the electrolyte paste, the positive electrode paste, the negative electrode paste, and the coating material paste and the coating material sheet prepared in the above way will now be described by reference to
In the second example, as illustrated in
Next, as illustrated in
Next, as illustrated in
After that, as illustrated in
Coating the coating material sheet 23 with the negative electrode paste and the coating material paste (
Furthermore, coating the electrolyte layer 13 with the positive electrode paste (
By performing the process illustrated in
(Cutting of Structural Body)
The structural body 5 formed by the method described in the above first example (
(Heat Treatment of Structural Body)
As illustrated in
The solid electrolyte contained in the electrolyte layer 13 of the structural body 5a is sintered by the heat treatment for burning. Furthermore, the solid electrolytes contained in the positive electrode layer 11 and the negative electrode layer 12 of the structural body 5a are sintered. As a result, the solid-state battery body 10A illustrated in
In addition, as a result of the heat treatment for burning, the coating material contained in the coating material sheet 23 and the coating material layer 24 of the structural body 5a is sintered and the coating material sheet 23 incorporates with the coating material layer 24. As a result, the insulating coating film 20A illustrated in
The coating film 20A formed by the burning may take various forms. For example, the coating film 20A formed by the burning may take the form of glass, crystalline glass, a polycrystal, or a single crystal. The coating film 20A may contain one phase or may contain two or more phases which differ in physical property. If a ceramic material, such as Al2O3 in the form of particles, is added to a coating material for the coating film 20A, then the coating film 20A having high hardness may be formed compared with a case where a coating material to which a ceramic material is not added is used. The coating film 20A is bonded to the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 of the solid-state battery body 10A by this heat treatment. The coating film 20A obtained by the burning may have a thermal expansion coefficient which is approximately the same as that of each layer of the solid-state battery body 10A and may have good adhesion to each layer of the solid-state battery body 10A, depending on the characteristics of a coating material used for forming the coating film 20A.
A section of the structural body 5a illustrated in
After the heat treatment is performed, the external electrode 31 is formed on the positive electrode lead surface 1Aa of the structural body 5a and the external electrode 32 is formed on the negative electrode lead surface 1Ab of the structural body 5a. For example, the external electrode 31 and the external electrode 32 are formed on the positive electrode lead surface 1Aa and the negative electrode lead surface 1Ab, respectively, of the structural body 5a after the heat treatment by the use of a method in which the positive electrode lead surface 1Aa and the negative electrode lead surface 1Ab are coated with a conductive paste, the conductive paste is dried, and the conductive paste is hardened or a method in which metal is deposited by sputtering, plating, or the like. By doing so, the solid-state battery 1A illustrated in
With the solid-state battery 1A the solid-state battery body 10A except the positive electrode lead surface 1Aa and the negative electrode lead surface 1Ab is covered with the coating film 20A having hardness higher than that of the solid electrolytes used in the solid-state battery body 10A. This effectively suppresses the appearance of a crack or a chip in the coating film 20A, entrance of moisture or gas caused by the appearance of a crack or a chip, or deterioration in the performance of the solid-state battery 1A caused by entrance of moisture or gas. Furthermore, with the solid-state battery 1A part of the coating film 20A is formed as buried layers on the portions of the electrolyte layer 13 which are inwardly depressed from the sides. This effectively suppresses peeling of the coating film 20A by an anchor effect and enhances the support and strength of each positive electrode layer 11 on the positive electrode lead surface 1Aa and each negative electrode layer 12 on the negative electrode lead surface 1Ab.
The solid-state battery 1A which is excellent in strength and environment resistance is manufactured by the above method.
In order to manufacture a solid-state battery, a method illustrated in
As illustrated in
Next, as illustrated in
For example, by performing the subprocesses illustrated in
If a positive electrode layer part is formed as an electrode layer part, then the positive electrode layer 11 and the electrolyte layer 13 are formed so that part (part on the side of a positive electrode lead surface 1Ba described later) of the positive electrode layer 11 will protrude outside the electrolyte layer 13. Furthermore, if a negative electrode layer part is formed as an electrode layer part, then the negative electrode layer 12 and the electrolyte layer 13 are formed so that part (part on the side of a negative electrode lead surface 1Bb described later) of the negative electrode layer 12 will protrude outside the electrolyte layer 13.
In the example illustrated in
The electrode layer part formed in this way is used. As illustrated in
Furthermore, the method illustrated in the above second example (
The structural body 7 illustrated in
In addition, the structural body 7a after cutting illustrated in
With the solid-state battery 1B, only the positive electrode layer 11 (portion 11a of the positive electrode layer 11) of the solid-state battery body 10B is exposed on the positive electrode lead surface 1Ba and the positive electrode layer 11 is supported on part of the coating film 20B having hardness higher than that of the electrolyte layer 13. Furthermore, only the negative electrode layer 12 (portion 12a of the negative electrode layer 12) of the solid-state battery body 10B is exposed on the negative electrode lead surface 1Bb and the negative electrode layer 12 is supported on part of the coating film 20B having hardness higher than that of the electrolyte layer 13. With the solid-state battery 1B this further enhances the support and strength of the positive electrode layer 11 on the positive electrode lead surface 1Ba and the negative electrode layer 12 on the negative electrode lead surface 1Bb.
[Evaluation of Coating Film]
Results obtained by evaluating the hardness of a coating film used in a solid-state battery will now be described. The results are indicated in Table 1.
In order to evaluate the hardness of a coating film, samples obtained by performing coating, drying, and heat treatment of the coating material paste used for forming the coating films 20A and 20B of the above solid-state batteries 1A and 1B, respectively, under the same conditions that are imposed when the solid-state batteries 1A and 1B are manufactured are prepared. In this case, two kinds of coating material pastes containing different glass components and obtained by performing coating, drying, and heat treatment under determined conditions are prepared as samples (“Glass 1” and “Glass 2” in Table 1). Furthermore, two kinds of coating material pastes which contain different glass components and to which 10 weight percent Al2O3 particles are added are prepared as samples (“Glass 1+10 wt. % Al2O3” and “Glass 2+10 wt. % Al2O3” in Table 1). In addition, the electrolyte paste used for forming the electrolyte layer 13 of the above solid-state batteries 1A and 1B and obtained by performing coating, drying, and heat treatment under the same conditions that are imposed when the solid-state batteries 1A and 1B are manufactured is prepared as a sample for comparison (“Electrolyte” in Table 1). After mirror finishing is performed on these five samples prepared, measurement is performed five or more times at a load of 200 g, 500 g, and 1000 g by the use of a Vickers hardness meter. A mean value is calculated as Vickers hardness (GPa).
It is ascertained from Table 1 that the Vickers hardness of the samples (“Glass 1” and “Glass 2”) formed from the two kinds of coating material pastes containing different glass components is higher than that of the sample (“Electrolyte”) formed from the electrolyte paste. Furthermore, it is ascertained that the Vickers hardness of the samples (“Glass 1+10 wt. % Al2O3” and “Glass 2+10 wt. % Al2O3”) formed from the two kinds of coating material pastes which contain different glass components and to which 10 weight percent Al2O3 particles are added is higher than that of the samples (“Glass 1” and “Glass 2”) to which 10 weight percent Al2O3 particles are not added.
From these evaluation results, a coating material paste containing a glass component or a coating material paste which contains a glass component and to which Al2O3 particles are added is used for forming the coating films 20A and 20B of the solid-state batteries 1A and 1B respectively. This makes it possible to cover the solid-state battery bodies 10A and 10B with the coating films 20A and 20B having hardness higher than that of the solid electrolytes used in the solid-state battery bodies 10A and 10B respectively.
[Modification]
In the above description, the example in which the solid-state battery body 10 including the one positive electrode layer 11 and the one negative electrode layer 12 is covered with the coating film 20 and the example in which the solid-state battery bodies 10A and 10B including the two positive electrode layers 11 and the two negative electrode layers 12 is covered with the coating films 20A and 20B respectively are given. However, the number of positive electrode layers 11 and negative electrode layers 12 included in a solid-state battery body covered with a coating film is not limited to the above examples. A solid-state battery body including three or more positive electrode layers 11 and three or more negative electrode layers 12 may be covered with the above coating film.
Furthermore, in the above description the coating material sheet 23 and the coating material layer 24, which is a buried layer, may be formed from coating material pastes which differ in composition. For example, as long as the coating material sheet 23 and the coating material layer 24 are sintered by the above heat treatment, the coating material sheet 23 incorporates with the coating material layer 24 by the above heat treatment, and the coating films 20A and 20B having hardness higher than that of the solid electrolytes used in the solid-state battery bodies 10A and 10B respectively are obtained, the coating material sheet 23 and the coating material layer 24 may be formed from coating material pastes which differ in composition. In addition, if the coating material layer 24 is formed by performing coating more than one time by the use of a coating material paste, then different coating material pastes may be used.
Furthermore, in the above description the example in which an oxide solid electrolyte is used in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12 and in which LAGP is used as the oxide solid electrolyte is given. However, amorphous LAGP, crystalline LAGP, or both of crystalline LAGP and amorphous LAGP may be used as LAGP.
The composition of LAGP in the electrolyte layer 13 is not limited to Li1.5Al0.5Ge1.5(PO4)3. NASICON type LAGP having another composition, such as Li1.4Al0.4Ge1.6(PO4)3, may be used. An oxide solid electrolyte other than LAGP, such as Li1.3Al0.3Ti1.7(PO4)3 which is one of NASICON-type LATP (general formula Li1+zAlzTi2-z(PO4)3 where 0<z≤1), garnet-type lanthanum lithium zirconate (Li7La3Zr2O12 hereinafter referred to as “LLZ”), perovskite-type lanthanum lithium titanate (Li0.5La0.5TiO3 hereinafter referred to as “LLT”), or partially nitrided γ-lithium phosphate (γ-Li3PO4 hereinafter referred to as “LiPON”), may be used in the electrolyte layer 13.
As long as a constant performance is realized in combination with an active material used, an oxide solid electrolyte other than LAGP, such as LATP, LLZ, LLT, or LiPON, may be used in the positive electrode layer 11 and the negative electrode layer 12.
For example, a NASICON-type oxide solid electrolyte expressed by the general formula Li1+yAlyM2−y(PO4)3 is suitable for the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12. In the above general formula, the composition ratio y is in the range of 0<y≤1 and M is one or both of germanium (Ge) and titanium (Ti).
Oxide solid electrolytes which are of the same kind may be used in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12. Alternatively, oxide solid electrolytes which are of different kinds may be used in the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12. One kind of oxide solid electrolyte may be used in each of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12. Alternatively, two or more kinds of oxide solid electrolytes may be used in each of the electrolyte layer 13, the positive electrode layer 11, and the negative electrode layer 12.
In addition, in the above description the example in which LCPO is used as a positive electrode active material contained in the positive electrode layer 11 is given. However, cobalt lithium phosphate (LiCoPO4), vanadium lithium phosphate (Li3V2(PO4)3 hereinafter referred to as “LVP”), or the like may be used as a positive electrode active material. One kind of material may be used as a positive electrode active material contained in the positive electrode layer 11. Alternatively, two or more kinds of materials may be used as a positive electrode active material contained in the positive electrode layer 11.
Furthermore, in the above description the example in which TiO2 is used as a negative electrode active material contained in the negative electrode layer 12 is given. However, metal silicide or the like may be used as a negative electrode active material. For example, LATP, LVP, niobium oxide (Nb2O5), nickel (Ni), or the like may be used as a negative electrode active material.
According to an aspect, a solid-state battery having excellent strength is realized.
All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the disclosure and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the disclosure. Although one or more embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-055338 | Mar 2021 | JP | national |
This application is a continuation application of International Application PCT/JP2022/000421 filed on Jan. 7, 2022, which designated the U.S., which is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2021-055338, filed on Mar. 29, 2021, the entire contents of each are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/000421 | Jan 2022 | US |
| Child | 18223729 | US |
