All-solid-state battery

Abstract

To provide an all-solid battery capable of realizing a satisfactory capacity balance while suppressing constriction mismatching between a cathode and an anode in a sintering process.SOLUTION: An all-solid battery comprises: an oxide-based solid electrolyte layer; a cathode layer provided on a first principal surface of the oxide-based solid electrolyte layer; and an anode layer provided on a second principal surface of the oxide-based solid electrolyte layer. Any one electrode layer of the cathode layer and the anode layer contains an active material of which the electron conductivity during charge is higher than that during no charge and the volume specific capacity is smaller than that of an active material in the other electrode layer. An active material volume ratio is higher than that of the other electrode layer, and a volume ratio of a conductive assistance is lower than that of the other electrode layer. A ratio T1 / T2 of an average thickness T1 of the one electrode layer to an average thickness T2 of the other electrode layer is 0.75 or more and 1.3 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery. [Background technology]

[0002] In recent years, secondary batteries have been used in a variety of fields. Secondary batteries using electrolytes have problems such as electrolyte leakage. Therefore, development of all-solid-state batteries, which are equipped with solid electrolytes and other solid-state elemental technologies, is underway.

[0003] When combining positive electrode active materials and negative electrode active materials with different specific capacities, in a typical secondary battery, the active materials are filled in the electrode layers of the positive and negative electrodes in the maximum amount, and the thicknesses of the electrode layers are changed to balance the capacities of the positive and negative electrodes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-164484 [Non-patent literature]

[0005] [Non-Patent Document 1] 61st Battery Symposium Abstracts 3J18 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, Patent Document 1 discloses an all-solid-state battery in which the packing density of graphite, the negative electrode active material, is increased and combined with an NCA-based positive electrode active material. In this battery, graphite has a higher volumetric capacity and a higher packing density, so to balance the capacity with the positive electrode, the positive electrode layer must be thick. Sulfide-based all-solid-state batteries can be fabricated using pressure, making it possible to balance the capacity through thickness. However, in all-solid-state batteries using oxide-based solid electrolytes, which require a sintering process, the capacity varies greatly depending on the combination of materials and the sintering temperature, making it difficult to balance the capacity through thickness.

[0007] As described in Non-Patent Document 1, when trying to balance the capacity by adjusting the thickness of the positive and negative electrode layers, problems such as layer separation and warping occur due to a shrinkage mismatch between the positive and negative electrodes during the sintering process.

[0008] When the positive and negative electrode layers are made to have the same thickness, in order to increase the filling amount (volume ratio) of the electrode active material with the smaller volumetric capacity, it is necessary to reduce the filling amount (volume ratio) of the conductive additive and ion conductive additive (solid electrolyte) in the electrode layer, which results in a problem of reduced electronic conductivity and ionic conductivity.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide an all-solid-state battery that can achieve a good capacity balance while suppressing the shrinkage mismatch between positive and negative electrodes during the sintering process. [Means for solving the problem]

[0010] The all-solid-state battery according to the present invention comprises an oxide-based solid electrolyte layer, a positive electrode layer provided on a first main surface of the oxide-based solid electrolyte layer, and an negative electrode layer provided on a second main surface of the oxide-based solid electrolyte layer, wherein one of the positive electrode layer and the negative electrode layer contains an active material that exhibits higher electronic conductivity when charged than when uncharged and has a smaller volumetric capacity than the active material of the other electrode layer, has a higher active material volume ratio and a lower conductive additive volume ratio than the other electrode layer, and a ratio T1 / T2 of an average thickness T1 of the one electrode layer to an average thickness T2 of the other electrode layer is 0.75 or more and 1.3 or less.

[0011] In the all-solid-state battery, the one electrode layer may be the positive electrode layer, and the other electrode layer may be the negative electrode layer.

[0012] In the one electrode layer of the all-solid-state battery, the volume ratio of the ion-conductive solid electrolyte may be 30 Vol.% or more and 60 Vol.% or less.

[0013] In the all-solid-state battery, when the one electrode layer is the positive electrode layer, the active material having higher electronic conductivity when charged than when uncharged may be LiCoPO4, Li2CoP2O7, or Li6Co5(P2O7)4.

[0014] In the one electrode layer of the all-solid-state battery, the volume ratio of the active material may be 15 Vol.% or more and 55 Vol.% or less.

[0015] In the one electrode layer of the all-solid-state battery, the volume ratio of the conductive additive may be 8 Vol.% or more and 24 Vol.% or less.

[0016] In the all-solid-state battery, when the one electrode layer is the negative electrode layer, the active material having higher electron conductivity during charging than during uncharged is Li 1.3 Al 0.3 Ti 1.7 It may be (PO4)3, LiTi2(PO4)3, or LiTiOPO4. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an all-solid-state battery that can achieve a good capacity balance while suppressing the shrinkage mismatch between the positive and negative electrodes during the sintering process. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery. [Figure 2] FIG. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery. [Figure 3] FIG. 1 is a schematic cross-sectional view of a stacked-type all-solid-state battery. [Figure 4] FIG. 1 is a schematic cross-sectional view of another stacked-type all-solid-state battery. [Figure 5] FIG. 1 is a diagram illustrating a flow of a method for manufacturing an all-solid-state battery. [Figure 6] 1(a) and 1(b) are diagrams illustrating the lamination process. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments will be described with reference to the drawings.

[0020] (First embodiment) 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery 100 according to the first embodiment. As illustrated in FIG. 1, the all-solid-state battery 100 has a structure in which a solid electrolyte layer 30 is sandwiched between a positive electrode layer 10 and a negative electrode layer 20. For example, the positive electrode layer 10 is formed on a first main surface of the solid electrolyte layer 30, and the negative electrode layer 20 is formed on a second main surface of the solid electrolyte layer 30.

[0021] The solid electrolyte layer 30 is mainly composed of a solid electrolyte having ion conductivity. The solid electrolyte of the solid electrolyte layer 30 is, for example, an oxide-based solid electrolyte having lithium ion conductivity. The solid electrolyte is, for example, a phosphate-based solid electrolyte having a NASICON structure. The phosphate-based solid electrolyte having a NASICON structure has high conductivity and is stable in the air. The phosphate-based solid electrolyte is, for example, a phosphate containing lithium. The phosphate is not particularly limited, but examples include composite lithium phosphate salts with Ti (e.g., LiTi2(PO4)3). Alternatively, Ti can be partially or completely substituted with a tetravalent transition metal such as Ge, Sn, Hf, or Zr. Furthermore, to increase the Li content, it may be partially substituted with a trivalent transition metal such as Al, Ga, In, Y, or La. More specifically, for example, Li 1+x Al x Ge 2-x (PO4)3 and Li 1+x Al x Zr 2-x (PO4)3, Li 1+x Al x Ti 2-x (PO4)3, etc.

[0022] As illustrated in FIG. 2 , the positive electrode layer 10 includes a positive electrode active material 12, a conductive additive 13, a solid electrolyte 14, and the like. The negative electrode layer 20 includes a negative electrode active material 22, a conductive additive 23, a solid electrolyte 24, and the like. When the positive electrode layer 10 includes the positive electrode active material 12 and the negative electrode layer 20 includes the negative electrode active material 22, the all-solid-state battery 100 can be used as a secondary battery. When the positive electrode layer 10 includes the conductive additive 13 and the negative electrode layer 20 includes the conductive additive 23, the positive electrode layer 10 and the negative electrode layer 20 are electrically conductive. When the positive electrode layer 10 includes the solid electrolyte 14 and the negative electrode layer 20 includes the solid electrolyte 24, the positive electrode layer 10 and the negative electrode layer 20 are electrically conductive. Note that hatching is omitted for the solid electrolyte layer 30 in FIG. 2 . Hatching is also omitted for the solid electrolytes 14 and 24.

[0023] The positive electrode active material 12 is a positive electrode active material that has higher electronic conductivity when charged than when not charged (empty charging). The positive electrode active material 12 is, for example, LiCoPO4, Li2CoP2O7, or Li6Co5(P2O7)4.

[0024] The negative electrode active material 22 is not particularly limited as long as it is an active material having a negative electrode function, and examples thereof include Nb2O5, V2O5, and Ta2O5.

[0025] The conductive additives 13 and 23 are not particularly limited as long as they are conductive materials, and examples thereof include carbon materials. Alternatively, metals may be used as the conductive additives 13 and 23. Examples of metals for the conductive additives 13 and 23 include Pd, Ni, Cu, Fe, and alloys containing these.

[0026] The solid electrolytes 14 and 24 are not particularly limited as long as they are ion-conductive solid electrolytes. For example, the solid electrolyte that is the main component of the solid electrolyte layer 30 can be used as the solid electrolytes 14 and 24.

[0027] The negative electrode active material 22 is not particularly limited, but in the combination of the positive electrode active material 12 and the negative electrode active material 22, an active material having a smaller volumetric capacity than the negative electrode active material 22 is used as the positive electrode active material 12. The volume ratio of the positive electrode active material 12 in the positive electrode layer 10 is higher than the volume ratio of the negative electrode active material 22 in the negative electrode layer 20. The volume ratio of the conductive additive 13 in the positive electrode layer 10 is lower than the volume ratio of the conductive additive 23 in the negative electrode layer 20.

[0028] This configuration makes it possible to achieve a good capacity balance between the positive electrode layer 10 and the negative electrode layer 20 while minimizing the effect of decreased electronic conductivity. For example, when the positive electrode active material 12 has a smaller volumetric capacity than the negative electrode active material 22, it is desirable to increase the filling amount of the positive electrode active material 12 in order to achieve a capacity balance between the positive electrode layer 10 and the negative electrode layer 20 with the same electrode layer thickness. However, since reducing the amount of the conductive additive 13 reduces electronic conductivity and results in high resistance, the conductive additive 13 cannot be reduced. However, by using a positive electrode active material 12 whose electronic conductivity improves upon charging, electronic conductivity in the positive electrode layer 10 can be made sufficient in the charged state in which the battery is operated. Therefore, a good capacity balance can be achieved even if the difference in thickness between the positive electrode layer 10 and the negative electrode layer 20 is small.

[0029] Furthermore, in this embodiment, the ratio T1 / T2 of the average thickness T1 of the positive electrode layer 10 to the average thickness T2 of the negative electrode layer 20 is set to 0.75 or more and 1.3 or less. By setting the ratio T1 / T2 to 0.75 or more and 1.3 or less in this way, the difference in thickness between the positive electrode layer 10 and the negative electrode layer 20 is reduced. This makes it possible to suppress a shrinkage mismatch between the positive electrode layer 10 and the negative electrode layer 20 during the sintering process. This makes it possible to suppress warping in the all-solid-state battery 100 and to suppress the occurrence of cracks.

[0030] From the above, the all-solid-state battery 100 according to this embodiment can achieve a good capacity balance while suppressing the shrinkage mismatch between the positive and negative electrodes in the sintering process.

[0031] The average thickness T1 of the positive electrode layer 10 and the average thickness T2 of the negative electrode layer 20 can be measured by averaging the thicknesses at 10 locations in SEM observation of a cross section cut perpendicular to the lamination direction.

[0032] If the volume ratio of the positive electrode active material 12 in the positive electrode layer 10 is too small, sufficient capacity density may not be ensured. Therefore, it is preferable to set a lower limit for the volume ratio of the positive electrode active material 12 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the positive electrode active material 12 is preferably 15 Vol.% or more, more preferably 17.5 Vol.% or more, and even more preferably 20 Vol.% or more.

[0033] If the volume ratio of the positive electrode active material 12 in the positive electrode layer 10 is too high, there is a risk of insufficient sintering densification of the electrode and an increase in internal resistance due to reduced electronic and ionic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the positive electrode active material 12 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the positive electrode active material 12 is preferably 55 Vol.% or less, more preferably 50 Vol.% or less, and even more preferably 45 Vol.% or less.

[0034] If the volume ratio of the conductive additive 13 in the positive electrode layer 10 is too small, there is a risk of an increase in internal resistance due to a decrease in electronic conductivity. Therefore, it is preferable to set a lower limit for the volume ratio of the conductive additive 13 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the conductive additive 13 is preferably 8 vol.% or more, more preferably 9 vol.% or more, and even more preferably 10 vol.% or more.

[0035] If the volume ratio of the conductive additive 13 in the positive electrode layer 10 is too high, there is a risk of a decrease in capacity, insufficient sintering densification of the electrode, and an increase in internal resistance due to a decrease in ion conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the conductive additive 13 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the conductive additive 13 is preferably 24 Vol.% or less, more preferably 22 Vol.% or less, and even more preferably 20 Vol.% or less.

[0036] If the volume ratio of the solid electrolyte 14 in the positive electrode layer 10 is too small, there is a risk of reduced ion conductivity and insufficient sintering densification of the electrode. Therefore, it is preferable to set a lower limit for the volume ratio of the solid electrolyte 14 in the positive electrode layer 10. For example, the volume ratio of the solid electrolyte 14 in the positive electrode layer 10 is preferably 30 Vol.% or more, more preferably 35 Vol.% or more, and even more preferably 40 Vol.% or more.

[0037] If the volume ratio of the solid electrolyte 14 in the positive electrode layer 10 is too high, there is a risk of increased internal resistance due to a decrease in capacity and decreased electronic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the solid electrolyte 14 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the solid electrolyte 14 is preferably 65 Vol.% or less, more preferably 60 Vol.% or less, and even more preferably 55 Vol.% or less.

[0038] If the volume ratio of the anode active material 22 in the anode layer 20 is too small, sufficient capacity density may not be ensured. Therefore, it is preferable to set a lower limit for the volume ratio of the anode active material 22 in the anode layer 20. For example, in the anode layer 20, the volume ratio of the anode active material 22 is preferably 10 Vol.% or more, more preferably 12.5 Vol.% or more, and even more preferably 15 Vol.% or more.

[0039] If the volume ratio of the anode active material 22 in the anode layer 20 is too high, there is a risk of insufficient sintering densification of the electrode and an increase in internal resistance due to reduced electronic conductivity and ionic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the anode active material 22 in the anode layer 20. For example, in the anode layer 20, the volume ratio of the anode active material 22 is preferably 45 Vol.% or less, more preferably 40 Vol.% or less, and even more preferably 35 Vol.% or less.

[0040] If the volume ratio of the conductive additive 23 in the negative electrode layer 20 is too small, there is a risk of an increase in internal resistance due to a decrease in electronic conductivity. Therefore, it is preferable to set a lower limit for the volume ratio of the conductive additive 23 in the negative electrode layer 20. For example, in the negative electrode layer 20, the volume ratio of the conductive additive 23 is preferably 16 Vol.% or more, more preferably 18 Vol.% or more, and even more preferably 20 Vol.% or more.

[0041] If the volume ratio of the conductive additive 23 in the negative electrode layer 20 is too high, there is a risk of a decrease in capacity, insufficient sintering densification of the electrode, and an increase in internal resistance due to a decrease in ion conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the conductive additive 23 in the negative electrode layer 20. For example, in the negative electrode layer 20, the volume ratio of the conductive additive 23 is preferably 50 Vol.% or less, more preferably 45 Vol.% or less, and even more preferably 40 Vol.% or less.

[0042] If the volume ratio of the solid electrolyte 24 in the negative electrode layer 20 is too small, there is a risk of reduced ion conductivity and insufficient sintering densification of the electrode. Therefore, it is preferable to set a lower limit for the volume ratio of the solid electrolyte 24 in the negative electrode layer 20. For example, the volume ratio of the solid electrolyte 24 in the negative electrode layer 20 is preferably 30 Vol.% or more, more preferably 35 Vol.% or more, and even more preferably 40 Vol.% or more.

[0043] If the volume ratio of the solid electrolyte 24 in the anode layer 20 is too high, there is a risk of increased internal resistance due to a decrease in capacity and decreased electronic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the solid electrolyte 24 in the anode layer 20. For example, in the anode layer 20, the volume ratio of the solid electrolyte 24 is preferably 65 Vol.% or less, more preferably 60 Vol.% or less, and even more preferably 55 Vol.% or less.

[0044] From the viewpoint of suppressing the shrinkage mismatch between the positive electrode layer 10 and the negative electrode layer 20 during the sintering process, the ratio T1 / T2 is preferably 0.75 or more and 1.30 or less, and more preferably 0.80 or more and 1.25 or less.

[0045] With the spread of IoT devices and wearable equipment, there are high expectations for the adoption of all-solid-state batteries that are small and thin, yet offer high capacity, high output, and emphasize safety. Furthermore, for backup applications, there are demands for constant voltage (CV) charging and high-rate discharge (pulse discharge). CV-chargeable secondary batteries eliminate the need for a current control IC, reducing the number of components and the volume occupied by devices, and thus offering the advantage of smaller size and lower costs.

[0046] For example, a non-aqueous electrolyte secondary battery capable of large current pulse discharge on the order of milliamperes has been developed by etching the inner lid surface of the battery storage can to create a textured structure and reduce resistance. Alternatively, a coin-type lithium secondary battery has been developed that is resistant to battery resistance increases even when repeatedly operated under conditions for IoT devices, such as CV charging and pulse charging / discharging, by providing a carbon layer on the current collector and contacting it with a sintered electrode plate, with the contact maintained by pressure from the crimping of the storage can.

[0047] These secondary batteries are designed to minimize internal resistance and to prevent resistance from increasing, making them suitable for high-rate discharge such as pulse discharge. However, these secondary batteries require a limiting resistor to prevent a sudden large current from flowing during CV charging to simplify charging, making them unsuitable for applications where simplification of package and control circuit design is particularly desirable.

[0048] For example, if an all-solid-state battery is designed to have low resistance at any state of charge (SOC) to enable high-rate discharge, a large current will flow when CV charging is performed from a low SOC state, raising concerns about battery failure and circuit damage without a limiting resistor. On the other hand, if the battery resistance is increased, the amount of current during charging can be reduced, but it will not be suitable for high-rate discharge. Therefore, an all-solid-state battery is required that has high resistance at low SOC before charging and low resistance at high SOC after charging.

[0049] The all-solid-state battery 100 according to this embodiment uses a positive electrode active material 12 whose electronic conductivity is higher when fully charged than when uncharged, and the volume ratio of the conductive additive 13 in the positive electrode layer 10 is lower than the volume ratio of the conductive additive 23 in the negative electrode layer 20, so that a large current at a low SOC is suppressed and stable CV charging is possible. On the other hand, the electronic conductivity of the positive electrode active material 12, which is rate-limiting during charging, is increased at a high SOC, making high-rate discharge possible.

[0050] (Second embodiment) In the second embodiment, the anode layer 20 contains an anode active material 22 that has higher electronic conductivity when charged than when uncharged and a smaller volumetric capacity than the cathode active material 12 of the cathode layer 10, and has a higher active material volume ratio and a lower conductive additive volume ratio than the cathode layer 10. Differences from the first embodiment will be described below.

[0051] The negative electrode active material 22 is a negative electrode active material that has higher electronic conductivity when charged than when not charged (when empty-charged). 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiTiOPO4, etc.

[0052] The positive electrode active material 12 is not particularly limited as long as it is an active material having a positive electrode function, and examples thereof include LiFePO4, LiMnPO4, and LiMn2O4.

[0053] The positive electrode active material 12 is not particularly limited, but in the combination of the positive electrode active material 12 and the negative electrode active material 22, an active material having a smaller volumetric capacity than the positive electrode active material 12 is used as the negative electrode active material 22. The volume ratio of the negative electrode active material 22 in the negative electrode layer 20 is higher than the volume ratio of the positive electrode active material 12 in the positive electrode layer 10. The volume ratio of the conductive additive 23 in the negative electrode layer 20 is lower than the volume ratio of the conductive additive 13 in the positive electrode layer 10.

[0054] This configuration makes it possible to achieve a good capacity balance between the positive electrode layer 10 and the negative electrode layer 20 while minimizing the effect of a decrease in electronic conductivity.

[0055] In this embodiment, the average thickness of the negative electrode layer 20 is denoted as T1, and the average thickness of the positive electrode layer 10 is denoted as T2. In this embodiment, by setting the ratio T1 / T2 to be 0.75 or more and 1.3 or less, the difference between the thickness of the positive electrode layer 10 and the thickness of the negative electrode layer 20 is reduced. This makes it possible to suppress a shrinkage mismatch between the positive electrode layer 10 and the negative electrode layer 20 during the sintering process. This makes it possible to suppress warping in the all-solid-state battery 100, and to suppress the occurrence of cracks.

[0056] From the above, in this embodiment as well, it is possible to achieve a good capacity balance while suppressing the shrinkage mismatch between the positive and negative electrodes during the sintering process.

[0057] If the volume ratio of the positive electrode active material 12 in the positive electrode layer 10 is too small, sufficient capacity density may not be ensured. Therefore, it is preferable to set a lower limit for the volume ratio of the positive electrode active material 12 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the positive electrode active material 12 is preferably 10 Vol.% or more, more preferably 12.5 Vol.% or more, and even more preferably 15 Vol.% or more.

[0058] If the volume ratio of the positive electrode active material 12 in the positive electrode layer 10 is too high, there is a risk of insufficient sintering densification of the electrode and an increase in internal resistance due to a decrease in electronic conductivity and ionic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the positive electrode active material 12 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the positive electrode active material 12 is preferably 45 Vol.% or less, more preferably 40 Vol.% or less, and even more preferably 35 Vol.% or less.

[0059] If the volume ratio of the conductive additive 13 in the positive electrode layer 10 is too small, there is a risk of an increase in internal resistance due to a decrease in electronic conductivity. Therefore, it is preferable to set a lower limit for the volume ratio of the conductive additive 13 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the conductive additive 13 is preferably 16 Vol.% or more, more preferably 18 Vol.% or more, and even more preferably 20 Vol.% or more.

[0060] If the volume ratio of the conductive additive 13 in the positive electrode layer 10 is too high, there is a risk of a decrease in capacity, insufficient sintering densification of the electrode, and an increase in internal resistance due to a decrease in ion conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the conductive additive 13 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the conductive additive 13 is preferably 50 Vol.% or less, more preferably 45 Vol.% or less, and even more preferably 40 Vol.% or less.

[0061] If the volume ratio of the solid electrolyte 14 in the positive electrode layer 10 is too small, there is a risk of reduced ion conductivity and insufficient sintering densification of the electrode. Therefore, it is preferable to set a lower limit for the volume ratio of the solid electrolyte 14 in the positive electrode layer 10. For example, the volume ratio of the solid electrolyte 14 in the positive electrode layer 10 is preferably 30 Vol.% or more, more preferably 35 Vol.% or more, and even more preferably 40 Vol.% or more.

[0062] If the volume ratio of the solid electrolyte 14 in the positive electrode layer 10 is too high, there is a risk of increased internal resistance due to a decrease in capacity and decreased electronic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the solid electrolyte 14 in the positive electrode layer 10. For example, in the positive electrode layer 10, the volume ratio of the solid electrolyte 14 is preferably 65 Vol.% or less, more preferably 60 Vol.% or less, and even more preferably 55 Vol.% or less.

[0063] If the volume ratio of the anode active material 22 in the anode layer 20 is too small, sufficient capacity density may not be ensured. Therefore, it is preferable to set a lower limit for the volume ratio of the anode active material 22 in the anode layer 20. For example, in the anode layer 20, the volume ratio of the anode active material 22 is preferably 15 Vol.% or more, more preferably 17.5 Vol.% or more, and even more preferably 20 Vol.% or more.

[0064] If the volume ratio of the anode active material 22 in the anode layer 20 is too high, there is a risk of insufficient sintering densification of the electrode and an increase in internal resistance due to a decrease in electronic conductivity and ionic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the anode active material 22 in the anode layer 20. For example, in the anode layer 20, the volume ratio of the anode active material 22 is preferably 55 Vol.% or less, more preferably 50 Vol.% or less, and even more preferably 45 Vol.% or less.

[0065] If the volume ratio of the conductive additive 23 in the negative electrode layer 20 is too small, there is a risk of an increase in internal resistance due to a decrease in electronic conductivity. Therefore, it is preferable to set a lower limit for the volume ratio of the conductive additive 23 in the negative electrode layer 20. For example, in the negative electrode layer 20, the volume ratio of the conductive additive 23 is preferably 8 vol.% or more, more preferably 9 vol.% or more, and even more preferably 10 vol.% or more.

[0066] If the volume ratio of the conductive additive 23 in the negative electrode layer 20 is too high, there is a risk of a decrease in capacity, insufficient sintering densification of the electrode, and an increase in internal resistance due to a decrease in ion conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the conductive additive 23 in the negative electrode layer 20. For example, in the negative electrode layer 20, the volume ratio of the conductive additive 23 is preferably 24 Vol.% or less, more preferably 22 Vol.% or less, and even more preferably 20 Vol.% or less.

[0067] If the volume ratio of the solid electrolyte 24 in the negative electrode layer 20 is too small, there is a risk of reduced ion conductivity and insufficient sintering densification of the electrode. Therefore, it is preferable to set a lower limit for the volume ratio of the solid electrolyte 24 in the negative electrode layer 20. For example, the volume ratio of the solid electrolyte 24 in the negative electrode layer 20 is preferably 30 Vol.% or more, more preferably 35 Vol.% or more, and even more preferably 40 Vol.% or more.

[0068] If the volume ratio of the solid electrolyte 24 in the anode layer 20 is too high, there is a risk of increased internal resistance due to a decrease in capacity and decreased electronic conductivity. Therefore, it is preferable to set an upper limit on the volume ratio of the solid electrolyte 24 in the anode layer 20. For example, in the anode layer 20, the volume ratio of the solid electrolyte 24 is preferably 65 Vol.% or less, more preferably 60 Vol.% or less, and even more preferably 55 Vol.% or less.

[0069] In this embodiment, the negative electrode active material 22 is used, which has higher electronic conductivity when fully charged than when uncharged, and the volume ratio of the conductive additive 23 in the negative electrode layer 20 is lower than the volume ratio of the conductive additive 13 in the positive electrode layer 10, so that large currents at low SOCs are suppressed, enabling stable CV charging. On the other hand, the electronic conductivity of the negative electrode active material 22, which is rate-limiting during charging, increases at high SOCs, enabling high-rate discharge.

[0070] (Stacked all-solid-state battery) 3 is a schematic cross-sectional view of a stacked-type all-solid-state battery 100a in which a plurality of battery units are stacked. The all-solid-state battery 100a includes a stacked chip 60 having a substantially rectangular parallelepiped shape. In the stacked chip 60, a first external electrode 40a and a second external electrode 40b are provided so as to contact two side surfaces, which are two of the four surfaces other than the top and bottom surfaces at the ends in the stacking direction. The two side surfaces may be two adjacent side surfaces or two side surfaces facing each other. In this embodiment, the first external electrode 40a and the second external electrode 40b are provided so as to contact two side surfaces facing each other (hereinafter referred to as two end surfaces).

[0071] In the following description, components having the same composition range, the same thickness range, and the same particle size distribution range as those of the all-solid-state batteries 100 according to the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0072] In the all-solid-state battery 100a, multiple positive electrode layers 10 and multiple negative electrode layers 20 are alternately stacked with solid electrolyte layers 30 interposed therebetween. The edges of the multiple positive electrode layers 10 are exposed on the first end surface of the stacked chip 60 but not on the second end surface. The edges of the multiple negative electrode layers 20 are exposed on the second end surface of the stacked chip 60 but not on the first end surface. As a result, the positive electrode layers 10 and the negative electrode layers 20 are alternately electrically connected to the first external electrode 40a and the second external electrode 40b. The solid electrolyte layer 30 extends from the first external electrode 40a to the second external electrode 40b. In this way, the all-solid-state battery 100a has a structure in which multiple battery units are stacked.

[0073] A cover layer 50 is laminated on the upper surface of the laminated structure of the positive electrode layer 10, the solid electrolyte layer 30, and the negative electrode layer 20 (in the example of FIG. 3, on the upper surface of the uppermost positive electrode layer 10). In addition, a cover layer 50 is laminated on the lower surface of the laminated structure (in the example of FIG. 3, on the lower surface of the lowermost positive electrode layer 10). The cover layer 50 is mainly composed of an inorganic material containing, for example, Al, Zr, Ti, etc. (e.g., Al2O3, ZrO2, TiO2, etc.). The cover layer 50 may also contain the main component of the solid electrolyte layer 30 as a main component.

[0074] The positive electrode layer 10 and the negative electrode layer 20 may each include a current collector layer. For example, as illustrated in FIG. 4, a first current collector layer 11 may be provided within the positive electrode layer 10. Furthermore, a second current collector layer 21 may be provided within the negative electrode layer 20. The first current collector layer 11 and the second current collector layer 21 are mainly composed of a conductive material. For example, metal, carbon, or the like may be used as the conductive material for the first current collector layer 11 and the second current collector layer 21. Connecting the first current collector layer 11 to the first external electrode 40a and connecting the second current collector layer 21 to the second external electrode 40b improves current collection efficiency.

[0075] Next, a description will be given of a method for manufacturing the all-solid-state battery 100a illustrated in Fig. 3. Fig. 5 is a diagram illustrating a flow of the method for manufacturing the all-solid-state battery 100a.

[0076] (Process for producing raw material powder for solid electrolyte layer) First, raw material powder for the solid electrolyte layer that constitutes the above-described solid electrolyte layer 30 is prepared. For example, raw materials, additives, etc. are mixed and a solid-phase synthesis method or the like is used to prepare raw material powder for an oxide-based solid electrolyte. The obtained raw material powder can be dry-pulverized to adjust the average particle size to a desired value. For example, the desired average particle size is adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls.

[0077] (Cover layer raw material powder production process) First, a ceramic raw material powder for the cover layer 50 is prepared. For example, raw materials, additives, etc. are mixed and solid-phase synthesis is used to prepare the raw material powder for the cover layer. The obtained raw material powder can be adjusted to a desired average particle size by dry milling. For example, the desired average particle size is adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls. If the solid electrolyte layer 30 and the cover layer 50 have the same composition, the raw material powder for the solid electrolyte layer can be used instead.

[0078] (Electrode layer paste preparation process) Next, internal electrode pastes for producing the above-described positive electrode layer 10 and negative electrode layer 20 are separately prepared. For example, the internal electrode pastes can be obtained by uniformly dispersing a conductive additive, an electrode active material, a solid electrolyte material, a sintering additive, a binder, a plasticizer, and the like in water or an organic solvent. The above-described solid electrolyte paste may be used as the solid electrolyte material. A carbon material or the like may be used as the conductive additive. A metal may also be used as the conductive additive. Examples of metals for the conductive additive include Pd, Ni, Cu, Fe, and alloys containing these. Pd, Ni, Cu, Fe, alloys containing these, and various carbon materials may also be used.

[0079] The sintering aid of the internal electrode paste contains one or more glass components such as Li-BO based compounds, Li-Si-O based compounds, Li-CO based compounds, Li-SO based compounds, and Li-PO based compounds.

[0080] (External electrode paste manufacturing process) Next, an external electrode paste for producing the first external electrode 40a and the second external electrode 40b is prepared. For example, the external electrode paste can be obtained by uniformly dispersing a conductive material, glass frit, a binder, a plasticizer, etc. in water or an organic solvent.

[0081] (Solid electrolyte green sheet manufacturing process) The raw material powder for the solid electrolyte layer is uniformly dispersed in an aqueous or organic solvent along with a binder, dispersant, plasticizer, etc., and then wet-pulverized to obtain a solid electrolyte slurry with a desired average particle size. This process can be performed using a bead mill, wet jet mill, various kneaders, high-pressure homogenizers, etc., with the bead mill being preferred because it allows for simultaneous adjustment of particle size distribution and dispersion. A binder is added to the resulting solid electrolyte slurry to obtain a solid electrolyte paste. The resulting solid electrolyte paste can be coated to produce a solid electrolyte green sheet 51. The coating method is not particularly limited, and can include slot die coating, reverse coating, gravure coating, bar coating, doctor blade coating, etc. The particle size distribution after wet-pulverization can be measured, for example, using a laser diffraction measurement device using laser diffraction scattering.

[0082] (Lamination process) As shown in FIG. 6( a), an internal electrode paste 52 is printed on one side of a solid electrolyte green sheet 51. A reverse pattern 53 is printed on the areas of the solid electrolyte green sheet 51 where the internal electrode paste 52 is not printed. The reverse pattern 53 may be the same as the solid electrolyte green sheet 51. After printing, multiple solid electrolyte green sheets 51 are stacked with an alternating offset. As shown in FIG. 6( b), a laminate is obtained by pressing cover sheets 54 from above and below in the stacking direction. In this case, a laminate having a substantially rectangular parallelepiped shape is obtained, with the internal electrode paste 52 for the positive electrode layer 10 exposed on one end surface and the internal electrode paste 52 for the negative electrode layer 20 exposed on the other end surface. The cover sheet 54 can be formed by coating a raw material powder for the cover layer using a method similar to that used in the solid electrolyte green sheet preparation process. The cover sheet 54 is formed thicker than the solid electrolyte green sheet 51. The thickness may be increased during coating, or by stacking multiple coated sheets.

[0083] Next, external electrode paste 55 is applied to each of the two end faces by dipping or the like and then dried, thereby obtaining a molded body for forming the all-solid-state battery 100a.

[0084] (Firing process) Next, the obtained laminate is fired. The firing conditions are not particularly limited, and may be in an oxidizing atmosphere or a non-oxidizing atmosphere, with the maximum temperature preferably being 400°C to 1000°C, more preferably 500°C to 900°C. A step of maintaining the temperature in an oxidizing atmosphere at a temperature lower than the maximum temperature may be provided in order to thoroughly remove the binder before the maximum temperature is reached. In order to reduce process costs, it is desirable to fire at as low a temperature as possible. After firing, a re-oxidation treatment may be performed. Through the above steps, an all-solid-state battery 100a is produced.

[0085] In addition, by sequentially stacking an internal electrode paste, a current collector paste containing a conductive material, and an internal electrode paste, a current collector layer can be formed within the positive electrode layer 10 and the negative electrode layer 20. [Example]

[0086] Hereinafter, all-solid-state batteries were fabricated according to the embodiments, and their characteristics were investigated.

[0087] Example 1 The positive electrode active material is LiCoPO4 (LCP), whose electronic conductivity improves with charging. Its effective volumetric capacity is 450 mAh / cm. 3 ) was used, carbon powder (C) was used as the conductive additive, and Li-Al-Ge-PO-based ionic conductor (LAGP) was used as the solid electrolyte. An internal electrode paste for the positive electrode layer was prepared so that the volume ratio of LCP, C, and LAGP was 35:15:50.

[0088] The negative electrode active material is Nb2O5 (1V vs. Li / Li + Volumetric capacity up to 920mAh / cm 3) was used, carbon powder (C) was used as the conductive additive, and Li-Al-Ge-PO-based ionic conductor (LAGP) was used as the solid electrolyte. An internal electrode paste for the negative electrode layer was prepared with a volume ratio of Nb2O5, C, and LAGP of 17.5:32.5:50.

[0089] A 20 μm thick solid electrolyte green sheet was fabricated by tape casting using a slurry consisting of a solid electrolyte made of LAGP, an organic binder, a dispersant, a plasticizer, and an organic solvent.

[0090] An internal electrode paste for the positive electrode layer was applied onto a first solid electrolyte green sheet by screen printing. An internal electrode paste for the negative electrode layer was applied onto a second solid electrolyte green sheet by screen printing. The internal electrode paste for the positive electrode layer and the internal electrode paste for the negative electrode layer were made to the same thickness. A plurality of first solid electrolyte green sheets and a plurality of second solid electrolyte green sheets were stacked so that the positive electrode layers and the negative electrode layers were pulled out alternately to the left and right, resulting in a green chip for a stacked all-solid-state battery. The green chip was sintered by degreasing and firing, and external electrodes were formed by applying and curing an external electrode paste, resulting in a stacked all-solid-state battery.

[0091] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.20 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 1.15 mAh.

[0092] (Comparative Example 1) The positive electrode active material is LiFePO4 (LFP: volumetric capacity 610 mAh / cm), which does not increase electron conductivity after charging. 3 An all-solid-state battery was fabricated in the same manner as in Example 1, except that the volume ratio of LFP, C, and LAGP was 26:24:50.

[0093] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.21 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 0.67 mAh.

[0094] (Comparative Example 2) An internal electrode paste for the positive electrode layer was prepared so that the volume ratio of LCP, C, and LAGP was 20:30:50, and an all-solid-state battery was prepared in the same manner as in Example 1, except that the thickness of the positive electrode layer was 1.75 times the thickness of the negative electrode layer in order to balance the capacities of the positive and negative electrodes.

[0095] When the external appearance of the stacked all-solid-state battery was observed, cracks were observed. The capacity estimated from the total amount of positive electrode active material was 1.20 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh. However, when the battery characteristics were actually evaluated, the battery had an open circuit failure, and the capacity could not be measured.

[0096] (Comparative Example 3) An all-solid-state battery was produced in the same manner as in Example 1, except that the internal electrode paste for the positive electrode layer was produced so that the volume ratio of LCP, C, and LAGP was 17.5:32.5:50.

[0097] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 0.60 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 0.55 mAh.

[0098] Example 2 An internal electrode paste for the positive electrode layer was prepared so that the volume ratio of LCP, C, and LAGP was 28:22:50, and an all-solid-state battery was prepared in the same manner as in Example 1, except that the thickness of the positive electrode layer was 1.25 times the thickness of the negative electrode layer.

[0099] Observation of the exterior of the stacked all-solid-state battery revealed slight warping but no cracks. The capacity estimated from the total amount of positive electrode active material was 1.20 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh. However, when the battery characteristics were actually evaluated, the battery capacity was 1.12 mAh.

[0100] Comparative Example 4 An internal electrode paste for the positive electrode layer was prepared so that the volume ratio of LCP, C, and LAGP was 26:24:50, and the thickness of the positive electrode layer was 1.35 times the thickness of the negative electrode layer. An all-solid-state battery was prepared in the same manner as in Example 1.

[0101] When the external appearance of the stacked all-solid-state battery was observed, cracks were observed. The capacity estimated from the total amount of positive electrode active material was 1.20 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh. However, when the battery characteristics were actually evaluated, the battery had a short circuit failure, and the capacity could not be measured.

[0102] Example 3 An all-solid-state battery was fabricated in the same manner as in Example 1, except that the internal electrode paste for the negative electrode layer was prepared so that the volume ratio of Nb2O5, C, and LAGP was 25:25:50.

[0103] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.20 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.71 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 1.18 mAh.

[0104] (Comparative Example 5) An all-solid-state battery was fabricated in the same manner as in Example 1, except that an internal electrode paste for a positive electrode layer was prepared so that the volume ratio of LCP, C, and LAGP was 30:25:45, and an internal electrode paste for a negative electrode layer was prepared so that the volume ratio of NbO, C, and LAGP was 25:25:50.

[0105] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.03 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.71 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 0.99 mAh.

[0106] (Comparative Example 6) An all-solid-state battery was fabricated in the same manner as in Example 1, except that an internal electrode paste for a positive electrode layer was prepared so that the volume ratio of LCP, C, and LAGP was 30:25:45, and an internal electrode paste for a negative electrode layer was prepared so that the volume ratio of NbO, C, and LAGP was 35:15:50.

[0107] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.03 mAh, and the capacity estimated from the total amount of negative electrode active material was 2.39 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 0.92 mAh.

[0108] The results of Examples 1 to 3 and Comparative Examples 1 to 6 are shown in Tables 1 and 2. [Table 1] [Table 2]

[0109] Evaluations were made for Examples 1 to 3 and Comparative Examples 1 to 6. If the actual capacity [mAh] was 1 mAh or more and no warping or cracking occurred, it was judged as good "◎". If the actual capacity [mAh] was 1 mAh or more and warping occurred but no cracking occurred, it was judged as good "◯". If it was neither very good "◎" nor good "◯", it was judged as poor "×".

[0110] Examples 1 to 3 were judged to be very good or good. This is thought to be because the positive electrode layer contained an active material that exhibited higher electronic conductivity during charging than during uncharged charging and had a smaller volumetric capacity than the active material in the negative electrode layer, had a higher active material volume ratio than the negative electrode layer, a lower conductive additive volume ratio than the negative electrode layer, and a ratio T1 / T2 of the average thickness T1 of the positive electrode layer to the average thickness T2 of the negative electrode layer of 0.75 or more and 1.3 or less.

[0111] In contrast, Comparative Examples 1 to 6 were judged to be defective. In Comparative Example 1, this is presumably because LiFePO4, which does not increase electronic conductivity after charging, was used as the positive electrode active material. In Comparative Examples 2 and 4, this is presumably because T1 / T2 exceeded 1.3. In Comparative Example 3, this is presumably because the volume ratios of the active material in the positive electrode layer and the negative electrode layer were the same. In Comparative Example 5, this is presumably because the volume ratios of the conductive additive in the positive electrode layer and the negative electrode layer were the same. In Comparative Example 6, this is presumably because the volume ratio of the active material in the negative electrode layer was higher than that in the positive electrode layer.

[0112] For Examples 1 to 3 and Comparative Examples 1 to 6, the inrush current [mA] and the rate (C) per 1 mAh battery capacity were measured when CV charging was performed from an SOC of 0%. For Examples 1 to 3 and Comparative Examples 1 to 6, a pulse discharge test was conducted in which 20 mA / 100 μsec was repeated 100 times at 1-second intervals at an SOC of 100%, and the pulse voltage drop [V] was measured. These results are shown in Tables 1 and 2. Measurements were not possible for Comparative Examples 2 and 4 due to the occurrence of cracks. If the inrush current was 5 C or less, the CV charge was judged as good (◯); if it was not 5 C or less, the CV charge was judged as poor (×). For the pulse voltage drop, if it was 0.16 V or less, the pulse discharge was judged as good; if it was not 0.16 V or less, the pulse discharge was judged as poor (×).

[0113] In Examples 1 to 3, both CV charging and pulse discharging were evaluated as good (good). This is presumably because a positive electrode active material was used that exhibited higher electronic conductivity when fully charged than when uncharged, and the volume ratio of the conductive additive in the positive electrode layer was lower than the volume ratio of the conductive additive in the negative electrode layer.

[0114] Example 4 The negative electrode active material is Li, whose electronic conductivity improves with charging. 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP:1V vs. Li / Li + Volumetric capacity up to 350mAh / cm 3 The negative electrode layer internal electrode paste was prepared by using LiFePO4 (LFP: volumetric capacity 610 mAh / cm), which does not increase electron conductivity after charging, as the positive electrode active material. 3 ) was applied, and an internal electrode paste for the positive electrode layer was prepared so that the volume ratio of LFP, C, and LAGP was 20:25:55. The other conditions were the same as in Example 1.

[0115] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.22 mAh, and the capacity estimated from the total amount of negative electrode active material was 1.23 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 1.04 mAh.

[0116] (Comparative Example 7) An internal electrode paste for the negative electrode layer was prepared so that the volume ratio of LATP, C, and LAGP was 25:25:50, and an all-solid-state battery was prepared in the same manner as in Example 4, except that the volume ratio of LFP, C, and LAGP was 25:25:50.

[0117] When the external appearance of the stacked all-solid-state battery was observed, no warping or cracks were found. The capacity estimated from the total amount of positive electrode active material was 1.52 mAh, and the capacity estimated from the total amount of negative electrode active material was 0.88 mAh, but when the battery characteristics were actually evaluated, the battery capacity was 0.85 mAh.

[0118] The results of Example 4 and Comparative Example 7 are shown in Tables 3 and 4. [Table 3] [Table 4]

[0119] Evaluation was carried out for Example 4 and Comparative Example 7. If the actual capacity [mAh] was 1 mAh or more and no warping or cracking occurred, it was judged as good "◎". If the actual capacity [mAh] was 1 mAh or more and warping occurred but no cracking occurred, it was judged as good "◯". If it was neither very good "◎" nor good "◯", it was judged as poor "×".

[0120] In Example 4, the battery was judged to be very good or good. This is thought to be because the anode layer contained an active material that exhibited higher electronic conductivity during charging than during uncharging and had a smaller volumetric capacity than the active material in the cathode layer, had a higher active material volume ratio than the positive electrode layer, a lower conductive additive volume ratio than the positive electrode layer, and a ratio T1 / T2 of the average thickness T1 of the anode layer to the average thickness T2 of the positive electrode layer of 0.75 or more and 1.3 or less.

[0121] In contrast, Comparative Example 7 was judged to be defective. This is presumably because the volume ratio of the active material in the positive electrode layer and the negative electrode layer was the same in Comparative Example 7.

[0122] For Example 4 and Comparative Example 7, the inrush current [mA] and the rate (C) per 1 mAh battery capacity were measured when CV charging was performed from an SOC of 0%. For Example 4 and Comparative Example 7, a pulse discharge test was also conducted, in which 20 mA / 100 μsec was repeated 100 times at 1-second intervals at an SOC of 100%, and the pulse voltage drop [V] was measured. These results are shown in Tables 3 and 4. If the inrush current was 5 C or less, the CV charging was judged as good (◯); if it was not 5 C or less, the CV charging was judged as poor (×). For the pulse voltage drop, if it was 0.16 V or less, the pulse discharge was judged as good; if it was not 0.16 V or less, the pulse discharge was judged as poor (×).

[0123] In Example 4, both CV charging and pulse discharging were evaluated as good (good). This is presumably because the negative electrode active material used had higher electronic conductivity when fully charged than when uncharged, and the volume ratio of the conductive additive in the negative electrode layer was lower than the volume ratio of the conductive additive in the positive electrode layer.

[0124] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0125] 10 Positive electrode layer 11 First current collector layer 20 negative electrode layer 21 Second current collector layer 30 Solid electrolyte layer 40a First external electrode 40b 2nd external electrode 50 cover layers 51 Solid electrolyte green sheet 52 Internal electrode paste 53 Reverse pattern 54 Cover Sheet 55 External electrode paste 60 stacked chips 100,100a all-solid-state battery

Claims

1. an oxide-based solid electrolyte layer; a positive electrode layer provided on a first main surface of the oxide-based solid electrolyte layer; an anode layer provided on the second main surface of the oxide-based solid electrolyte layer, one of the positive electrode layer and the negative electrode layer contains an active material that exhibits higher electronic conductivity during charging than during uncharging and has a smaller volumetric capacity than the active material of the other electrode layer, and has a higher active material volume ratio than the other electrode layer and a lower conductive additive volume ratio than the other electrode layer; a ratio T1 / T2 of an average thickness T1 of the one electrode layer to an average thickness T2 of the other electrode layer is 0.75 or more and 1.3 or less.

2. the one electrode layer is the positive electrode layer, 2. The all-solid-state battery according to claim 1, wherein the other electrode layer is the negative electrode layer.

3. 3. The all-solid-state battery according to claim 1, wherein the volume ratio of the ion-conductive solid electrolyte in the one electrode layer is 30 vol. % or more and 65 vol. % or less.

4. When the one electrode layer is the positive electrode layer, the active material that exhibits higher electron conductivity during charging than during uncharging is LiCoPO ４ , Li ２ CoP ２ O ７ or Li ６ Co ５ (P ２ O ７ ) ４ The all-solid-state battery according to any one of claims 1 to 3,

5. 5. The all-solid-state battery according to claim 1, wherein the volume ratio of the active material in the one electrode layer is 15 vol. % or more and 55 vol. % or less.

6. 6. The all-solid-state battery according to claim 1, wherein the volume ratio of the conductive additive in the one electrode layer is 8 vol. % or more and 24 vol. % or less.

7. When the one electrode layer is the negative electrode layer, the active material that exhibits higher electron conductivity during charging than during uncharged is Li １．３ Al ０．３ Ti １．７ (P.O. ４ ) ３ , LiTi ２ (P.O. ４ ) ３ , or LiTiOPO ４ 2. The all-solid-state battery according to claim 1,

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