JP7552635B2 - How to restore capacity in solid-state batteries - Google Patents

Description

This disclosure relates to a method for restoring capacity of an all-solid-state battery.

In recent years, with the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become important. In the automotive industry, too, development of high-output, high-capacity batteries for electric and hybrid vehicles is underway.

Patent Document 1 discloses a negative electrode using graphite particles, which can provide a non-aqueous lithium ion secondary battery with excellent input resistance characteristics.
Patent Documents 2 and 3 disclose methods for recovering the capacity of a lithium ion secondary battery by overdischarging.
Patent Document 4 discloses a solid-state secondary battery system capable of recovering from a decrease in output characteristics.

JP 2020-144978 A JP 2015-187938 A JP 1999-204148 A JP 2012-256430 A

In the case of liquid batteries, if the voltage is reduced below 1 V, the resistance increases due to side reactions in the electrolyte, and although the battery will be discharged to around 1 to 2 V, there is an issue that the recovery capacity is small.
In all-solid-state batteries, when an active material that undergoes large volume changes due to expansion and contraction during charging and discharging is used, if the voltage is reduced below 1 V, the conductive path is likely to be disconnected, resulting in a problem of a decrease in capacity and an increase in resistance.

This disclosure has been made in consideration of the above-mentioned circumstances, and its main objective is to provide a capacity recovery method for an all-solid-state battery that can recover capacity without increasing resistance.

The capacity recovery method of the all-solid-state battery disclosed herein is a capacity recovery method of an all-solid-state battery having a negative electrode layer containing lithium titanate as a negative electrode active material, comprising:
While superimposing a ripple current, constant current and constant voltage discharge is performed until the voltage reaches 0 V, and the voltage is maintained at 0 V for a predetermined period of time or more.

This disclosure provides a method for restoring capacity of an all-solid-state battery that allows capacity recovery without increasing resistance.

FIG. 1 is a diagram showing the results of the discharge capacity, discharge resistance, and charge resistance of an all-solid-state lithium ion secondary battery before and after a capacity recovery discharge treatment. FIG. 2 is a diagram showing the results of the discharge capacity, discharge resistance, and charge resistance of a liquid lithium ion secondary battery before and after a capacity recovery discharge treatment. FIG. 3 is a diagram showing the rate of change in capacity versus overdischarge treatment time with and without ripple current discharge.

Hereinafter, embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of an all-solid-state battery that does not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field.
In this specification, the use of "to" indicating a range of values means that the values before and after it are included as the lower limit and upper limit.
Furthermore, any combination of upper and lower limits in a numerical range can be used.

The capacity recovery method of the all-solid-state battery disclosed herein is a capacity recovery method of an all-solid-state battery having a negative electrode layer containing lithium titanate as a negative electrode active material, comprising:
While superimposing a ripple current, constant current and constant voltage discharge is performed until the voltage reaches 0 V, and the voltage is maintained at 0 V for a predetermined period of time or more.

The reason why the capacity recovery of the all-solid-state battery disclosed herein is higher than that of a liquid-based battery is presumably due to the fact that the Li ion concentration is maintained due to the absence of side reactions in the electrolyte.
The reason why resistance does not deteriorate in all-solid-state batteries is presumably because the formation of a coating on the electrodes due to a side reaction of the electrolyte does not occur in all-solid-state batteries.
The reason why the capacity recovery is accelerated by the superposition of the ripple current is presumed to be that the ripple charge/discharge causes Li ions to flow, generating thermal energy, which reduces the battery resistance.
In the case of active materials such as carbon, the active material expands and contracts when an electrical current is applied, and the active material with its conductive paths interrupted can no longer contribute to charging and discharging, leading to a decrease in capacity and making it impossible to recover capacity.
On the other hand, in the lithium titanate of the present disclosure, the expansion and contraction of the active material due to the current load is extremely small, so that the capacity recovery effect can be obtained. In addition, by taking advantage of the feature of small expansion and contraction, Li ions are mobilized by superimposing a ripple current during the discharge process, and thermal energy is generated, thereby reducing the battery resistance and efficiently recovering the capacity.

[Capacity recovery method]
The capacity recovery method disclosed herein involves discharging at a constant current and constant voltage until the voltage reaches 0 V while superimposing a ripple current, and then holding the voltage at 0 V for a predetermined period of time or longer.
The method of superimposing the ripple current can be appropriately selected from conventionally known methods.
The predetermined time for which the voltage is held at 0 V is not particularly limited, and may be, for example, the time until the current reaches a plateau.

[All-solid-state battery]
The all-solid-state battery of the present disclosure includes a negative electrode layer containing lithium titanate (LTO) as a negative electrode active material. The all-solid-state battery of the present disclosure may include a positive electrode, a solid electrolyte layer, and a negative electrode.

[Positive electrode]
The positive electrode has a positive electrode layer, and optionally a positive electrode current collector.

[Positive electrode layer]
The positive electrode layer contains a positive electrode active material, and may contain, as optional components, a conductive material, a solid electrolyte, a binder, and the like.

There is no particular limitation on the type of the positive electrode active material, and any material that can be used as an active material for an all-solid-state battery can be used. Examples of the positive electrode active material include lithium alloys, LiCoO ₂ , LiNi _x M _1-x O ₂ (x satisfies 0.5≦x<1, and M is at least one element selected from the group consisting of Co, Mn, and Al), LiMnO ₂ , Li-Mn spinel substituted with a different element, lithium titanate, lithium metal phosphate, LiCoN, Li ₂ SiO ₃ , Li ₄ SiO ₄ , transition metal oxides, TiS ₂ , Si, SiO ₂ , Si alloys, and lithium-storing intermetallic compounds.
_{Examples of} Li _{- Mn} spinels substituted _{with different} elements include _{LiMn1.5Ni0.5O4 , LiMn1.5Al0.5O4 , LiMn1.5Mg0.5O4 , LiMn1.5Co0.5O4} , _{LiMn1.5Fe0.5O4 , and LiMn1.5Zn0.5O4 .}
The lithium titanate is, for example, Li ₄ Ti ₅ O ₁₂ .
Examples of lithium metal phosphates include _LiFePO4 , _LiMnPO4 , _LiCoPO4 , and _LiNiPO4 .
Examples of transition metal oxides include _V2O5 and _MoO3 . Examples of _{lithium storage intermetallic compounds include Mg2Sn , Mg2Ge} , _Mg2Sb , and _Cu3Sb .
Examples of lithium alloys include Li-Au, Li-Mg, Li-Sn, Li-Si, Li-Al, Li-B, Li-C, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At. Examples of Si alloys include alloys with metals such as Li, and may also be alloys with at least one metal selected from the group consisting of Sn, Ge, and Al.
The shape of the positive electrode active material is not particularly limited, and may be particulate. When the positive electrode active material is particulate, the positive electrode active material may be primary particles or secondary particles.
A coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material, because this can suppress the reaction between the positive electrode active material and the solid electrolyte.
Examples of Li ion conductive oxides include LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , and Li ₃ PO ₄ . The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coating layer may cover, for example, 70% or more, or 90% or more of the surface of the positive electrode active material.

The conductive material may be a known material, such as a carbon material and metal particles. The carbon material may be at least one selected from the group consisting of acetylene black, furnace black, VGCF, carbon nanotubes, and carbon nanofibers. Among them, from the viewpoint of electronic conductivity, at least one selected from the group consisting of VGCF, carbon nanotubes, and carbon nanofibers may be used. The metal particles may be particles of Ni, Cu, Fe, SUS, etc.
The content of the conductive material in the positive electrode layer is not particularly limited.

As the solid electrolyte, the same ones as those exemplified in the solid electrolyte layer can be exemplified.
The content of the solid electrolyte in the positive electrode layer is not particularly limited, but may be, for example, within a range of 1 mass % to 80 mass % when the total mass of the positive electrode layer is taken as 100 mass %.

Examples of the binding agent (binder) include polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), and styrene butadiene rubber (SBR).
The content of the binder in the positive electrode layer is not particularly limited.

The thickness of the positive electrode layer is not particularly limited, but may be, for example, 10 to 100 μm.

The positive electrode layer can be formed by a conventionally known method.
For example, a positive electrode active material and, if necessary, other components are put into a solvent and stirred to prepare a paste for forming a positive electrode layer, and the paste for forming a positive electrode layer is applied onto one side of a support and dried to obtain a positive electrode layer.
Examples of the solvent include butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, and N-methyl-2-pyrrolidone (NMP).
The method for applying the paste for forming a positive electrode layer onto one surface of the support is not particularly limited, and examples thereof include a doctor blade method, a metal mask printing method, an electrostatic application method, a dip coating method, a spray coating method, a roll coating method, a gravure coating method, and a screen printing method.
The support can be appropriately selected from those having self-supporting properties and is not particularly limited. For example, metal foils such as Cu and Al can be used.

As another method for forming the positive electrode layer, the positive electrode layer may be formed by pressure molding a powder of a positive electrode mixture containing a positive electrode active material and other components as necessary. When the powder of the positive electrode mixture is pressure molded, a surface pressure of 1 MPa to 2000 MPa and a linear pressure of 1 ton/cm to 100 ton/cm are usually applied.
The method of applying pressure is not particularly limited, but examples thereof include a method of applying pressure using a plate press, a roll press, or the like.

[Positive electrode current collector]
The positive electrode current collector may be a known metal that can be used as a current collector for an all-solid-state battery. Examples of such metals include metal materials containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. The positive electrode current collector may be, for example, SUS, aluminum, nickel, iron, titanium, carbon, etc.
The shape of the positive electrode current collector is not particularly limited, and may be in various shapes such as a foil shape, a mesh shape, etc. The thickness of the positive electrode current collector varies depending on the shape, but may be, for example, in the range of 1 μm to 50 μm, or in the range of 5 μm to 20 μm.

[Negative electrode]
The negative electrode has a negative electrode layer, and optionally has a negative electrode current collector.

[Negative electrode layer]
The negative electrode layer contains at least a negative electrode active material, and optionally contains a solid electrolyte, a conductive material, a binder, and the like.
The negative electrode active material may be lithium titanate, such as Li ₄ Ti ₅ O ₁₂ .
The shape of the negative electrode active material is not particularly limited, and examples thereof include a particulate shape, a plate shape, etc. When the negative electrode active material is particulate, the negative electrode active material may be primary particles or secondary particles.
The conductive material and binder used in the negative electrode layer may be the same as those exemplified in the positive electrode layer, and the solid electrolyte used in the negative electrode layer may be the same as those exemplified in the solid electrolyte layer.
The thickness of the negative electrode layer is not particularly limited, but may be, for example, 10 to 100 μm.
The content of the negative electrode active material in the negative electrode layer is not particularly limited, but may be, for example, 20% by mass to 90% by mass.
The method for forming the negative electrode layer includes a method of applying a paste for forming the negative electrode layer containing a negative electrode active material onto a support and drying the paste, etc. The support may be the same as those exemplified for the positive electrode layer.

[Negative electrode current collector]
The material of the negative electrode current collector may be a material that does not alloy with Li, and examples of such materials include SUS, copper, and nickel. Examples of the shape of the negative electrode current collector include foil and plate. The planar shape of the negative electrode current collector is not particularly limited, and examples of such shapes include a circle, an ellipse, a rectangle, and any polygon. The thickness of the negative electrode current collector varies depending on the shape, and may be, for example, in the range of 1 μm to 50 μm, or in the range of 5 μm to 20 μm.

[Solid electrolyte layer]
The solid electrolyte layer includes at least a solid electrolyte.
As the solid electrolyte contained in the solid electrolyte layer, a known solid electrolyte that can be used in an all-solid-state battery can be appropriately used, and examples of such inorganic solid electrolytes include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, and a nitride-based solid electrolyte. The sulfide-based solid electrolyte may contain sulfur (S) as a main component of the anion element. The oxide-based solid electrolyte may contain oxygen (O) as a main component of the anion element. The hydride-based solid electrolyte may contain hydrogen (H) as a main component of the anion element. The halide-based solid electrolyte may contain a halogen (X) as a main component of the anion element. The nitride-based solid electrolyte may contain nitrogen (N) as a main component of the anion element.

The sulfide-based solid electrolyte may be a sulfide glass, a crystallized sulfide glass (glass ceramics), or a crystalline material obtained by subjecting a raw material composition to a solid-phase reaction treatment.
The crystalline state of the sulfide-based solid electrolyte can be confirmed, for example, by subjecting the sulfide-based solid electrolyte to powder X-ray diffraction measurement using CuKα radiation.

The sulfide glass can be obtained by subjecting a raw material composition (e.g., a mixture of _{Li2S and P2S5} ) to an amorphous process. Examples of the amorphous process include mechanical milling.

Glass ceramics can be obtained, for example, by heat treating a sulfide glass.
The heat treatment temperature may be any temperature higher than the crystallization temperature (Tc) of the sulfide glass observed by thermal analysis, and is usually 195° C. or higher. On the other hand, there is no particular upper limit to the heat treatment temperature.
The crystallization temperature (Tc) of the sulfide glass can be measured by differential thermal analysis (DTA).
The heat treatment time is not particularly limited as long as it is a time that can obtain the desired crystallinity of the glass ceramics, but is, for example, in the range of 1 minute to 24 hours, and particularly, in the range of 1 minute to 10 hours.
The method of heat treatment is not particularly limited, but for example, a method using a baking furnace can be mentioned.

Examples of oxide-based solid electrolytes include solid electrolytes containing Li element, Y element (Y is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O element. Specific examples of oxide-based solid electrolytes include _garnet -type solid electrolytes such as _Li7La3Zr2O12 , Li7 _{-xLa3 ( Zr2- xNbx ) O12} (0≦x≦2), and _Li5La3Nb2O12 ; perovskite-type solid electrolytes such as (Li, _La ) _TiO3 , (Li,La) _NbO3 , and (Li _{,Sr)(Ta,Zr)O3; Nasicon-type solid electrolytes such as Li(Al,Ti)(PO4)3 and Li ( Al ,} Ga)( _PO4 ) ₃ ; Li-P-O-based solid electrolytes such as _{Li3PO4 and} LIPON (a compound in which part of _the O in _Li3PO4 is replaced with N); and _{Li3BO 3} , and compounds in which part of O in Li ₃ BO ₃ is replaced with C.
In the present disclosure, the notation "(A, B, C)" in a chemical formula means "at least one selected from the group consisting of A, B, and C."

The hydride-based solid electrolyte contains, for example, Li and a complex anion containing hydrogen, such as (BH ₄ ) ⁻ , (NH ₂ ) ⁻ , (AlH ₄ ) ⁻ , and (AlH ₆ ) ³⁻ .

The halide-based solid electrolyte is, for example, represented by the following composition formula (1).
Li _α M _β X _γ ...Formula (1)
In the composition formula (1), α, β, and γ are each independently a value greater than 0. M includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li. X includes at least one element selected from the group consisting of F, Cl, Br, and I.
In the present disclosure, the term "metalloid elements" refers to B, Si, Ge, As, Sb, and Te. The term "metal elements" refers to all elements contained in Groups 1 to 12 of the periodic table except for hydrogen, and all elements contained in Groups 13 to 16 of the periodic table except for B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, the term "metalloid elements" or "metal elements" refers to a group of elements that can become cations when forming an inorganic compound with a halogen element.
More specifically, examples of halide-based solid electrolytes include _Li3YX6 , _{Li2MgX4 , Li2FeX4 , LiAlX4} , _{LiGaX4 , LiInX4} , _Li3AlX6 , _Li3GaX6 , and _Li3InX6 . Here, X is at least one selected from the group consisting of F, _Cl , _Br , and _I.

An example of the nitride-based solid electrolyte is Li ₃ N.

The solid electrolyte may be in the form of particles from the viewpoint of ease of handling.
The average particle size of the solid electrolyte particles is not particularly limited, but may be, for example, 10 nm or more, and may be 100 nm or more, whereas the average particle size of the solid electrolyte particles is, for example, 25 μm or less, and may be 10 μm or less.

In this disclosure, unless otherwise specified, the average particle size of particles is the volume-based median diameter (D50) value measured by laser diffraction/scattering particle size distribution measurement. In addition, in this disclosure, the median diameter (D50) is the diameter (volume average diameter) at which the cumulative volume of particles is half (50%) of the total volume when the particles are arranged in order from smallest to largest particle size.

The solid electrolyte may be used alone or in combination of two or more kinds. When two or more kinds of solid electrolytes are used, the two or more kinds of solid electrolytes may be mixed, or two or more layers of the solid electrolyte may be formed to form a multilayer structure.
The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, but is, for example, 50% by mass or more, may be in the range of 60% by mass or more and 100% by mass or less, may be in the range of 70% by mass or more and 100% by mass or less, or may be 100% by mass.

The solid electrolyte layer may contain a binder from the viewpoint of expressing plasticity. Examples of such binders include the materials exemplified as the binders used in the positive electrode layer. However, in order to facilitate high output, the binder may be contained in the solid electrolyte layer in an amount of 5 mass% or less from the viewpoint of preventing excessive aggregation of the solid electrolyte and enabling the formation of a solid electrolyte layer having a uniformly dispersed solid electrolyte.

The thickness of the solid electrolyte layer is not particularly limited, and is usually 0.1 μm or more and 1 mm or less.
The method for forming the solid electrolyte layer includes a method of applying a paste for forming a solid electrolyte layer containing a solid electrolyte onto a support and drying it, and a method of pressurizing a powder of a solid electrolyte material containing a solid electrolyte. The support may be the same as those exemplified for the positive electrode layer. When pressurizing the powder of the solid electrolyte material, a press pressure of about 1 MPa to 2000 MPa is usually applied.
The method of applying pressure is not particularly limited, but may be any of the pressure applying methods exemplified in the formation of the positive electrode layer.

The all-solid-state battery may, as necessary, include an exterior body that houses a laminate including a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector in this order, and a restraining member and the like.
The material of the exterior body is not particularly limited as long as it is stable with respect to the solid electrolyte, and examples of the material include polypropylene, polyethylene, and resins such as acrylic resin.
The restraining member may be any known member usable as a battery restraining member as long as it can apply a restraining pressure in the stacking direction to the laminate. For example, a restraining member having a plate-shaped portion that sandwiches both surfaces of the laminate, a rod-shaped portion that connects the two plate-shaped portions, and an adjustment portion that is connected to the rod-shaped portion and adjusts the restraining pressure by a screw structure or the like can be used. The adjustment portion can apply a desired restraining pressure to the laminate.
The restraining pressure is not particularly limited, but may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. By increasing the restraining pressure, there is an advantage that the contact between the layers is easily improved. On the other hand, the restraining pressure may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less. If the restraining pressure is too high, the restraining member is required to have high rigidity, and the restraining member may become large.

The all-solid-state battery may have only one of the laminates, or may be formed by stacking a plurality of the laminates.
The all-solid-state battery may be an all-solid-state lithium-ion secondary battery or the like.
Examples of the shape of the all-solid-state battery include a coin type, a laminate type, a cylindrical type, and a square type.
The use of the all-solid-state battery is not particularly limited, but examples thereof include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the all-solid-state battery may be used as a driving power source for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles. The all-solid-state battery of the present disclosure may also be used as a power source for moving objects other than vehicles (e.g., railways, ships, and aircraft), and may also be used as a power source for electrical products such as information processing devices.

In the manufacturing method of the all-solid-state battery disclosed herein, for example, a solid electrolyte layer is formed by first applying a paste for forming a solid electrolyte layer to a support and drying it. Then, a paste for forming a positive electrode layer containing a positive electrode active material is applied to one side of the solid electrolyte layer and dried to obtain a positive electrode layer. Thereafter, the support is peeled off from the solid electrolyte layer, and a paste for forming an anode layer is applied to the other side of the solid electrolyte layer and dried to form a negative electrode layer. If necessary, a positive electrode current collector is attached to the side of the positive electrode layer opposite the solid electrolyte layer, and a negative electrode current collector is attached to the side of the negative electrode layer opposite the solid electrolyte layer to form an all-solid-state battery.

Example 1
An all-solid-state lithium-ion secondary battery including a negative electrode layer containing lithium titanate as a negative electrode active material was prepared.
The all-solid-state lithium ion secondary battery was subjected to normal charging and discharging, and the discharge capacity, discharge resistance, and charge resistance before the capacity recovery discharge treatment were calculated.
Thereafter, as a capacity recovery discharge treatment, the fully charged all-solid-state lithium ion secondary battery was discharged at a constant current and constant voltage to 0 V while a ripple current was superimposed, and the voltage was maintained at 0 V for a predetermined time or more.
Thereafter, a normal charging resistance was performed on the all-solid-state lithium ion secondary battery, and the discharge capacity, discharge resistance, and charging resistance after the capacity recovery discharge treatment were calculated.
These results are shown in FIG.
Fig. 1 is a diagram showing the results of the discharge capacity, discharge resistance, and charge resistance before and after the capacity recovery discharge treatment of an all-solid-state lithium-ion secondary battery. Fig. 1 shows the discharge capacity, discharge resistance, and charge resistance after the capacity recovery discharge treatment, when the discharge capacity, discharge resistance, and charge resistance before the capacity recovery discharge treatment are each set to 100%.
As shown in FIG. 1, it has been confirmed that the present disclosure allows the discharge capacity to be restored without increasing the resistance.

(Comparative Example 1)
The discharge capacity, discharge resistance, and charge resistance before and after the capacity recovery discharge treatment were calculated in the same manner as in Example 1, except that a liquid-based lithium-ion secondary battery was prepared, which had a negative electrode layer containing lithium titanate as a negative electrode active material and used an electrolytic solution instead of a solid electrolyte layer.
These results are shown in FIG.
Fig. 2 is a diagram showing the results of the discharge capacity, discharge resistance, and charge resistance before and after the capacity recovery discharge treatment of a liquid lithium ion secondary battery. Fig. 2 shows the discharge capacity, discharge resistance, and charge resistance after the capacity recovery discharge treatment, when the discharge capacity, discharge resistance, and charge resistance before the capacity recovery discharge treatment are each set to 100%.
As shown in FIG. 2, it was confirmed that in the liquid lithium ion secondary battery, the resistance increased and the recovery rate of the discharge capacity was smaller than that in Example 1.

(Comparative Example 2)
The capacity recovery discharge treatment was carried out in the same manner as in Example 1, except that the ripple current was not superimposed.
FIG. 3 is a diagram showing the rate of change in capacity versus overdischarge treatment time with and without ripple current discharge.
As shown in FIG. 3, it is understood that the overdischarge treatment time required to recover to a desired capacity can be shortened by discharging the ripple current.

Claims (1)

A capacity recovery method for an all-solid-state battery having a negative electrode layer containing lithium titanate as a negative electrode active material, comprising:
While superimposing a ripple current, the voltage is discharged to 0 V at a constant current and constant voltage, and the voltage is maintained at 0 V for a predetermined time or more .
The capacity recovery method for an all -solid-state battery, wherein the predetermined time is a time until a current of the all-solid-state battery reaches a plateau .