JP6927106B2 - All-solid-state secondary battery - Google Patents

Description

The present disclosure relates to an all-solid-state secondary battery.

All-solid-state batteries that use solid electrolytes without using electrolytes are attracting attention due to their high energy density. When manufacturing such an all-solid-state battery, a method has been proposed in which an electrode material is formed into an electrode shape using a slurry in which an electrode material is dispersed or dissolved in a solvent, and then the solvent is removed to manufacture the electrode.

Patent Document 1 discloses a slurry for a positive electrode for a sulfide-based solid-state battery containing at least a fluorine-based copolymer containing a vinylidene fluoride monomer unit, a positive electrode active material, and a solvent or a dispersion medium. Patent Document 1 describes that butyl butyrate is preferable as the solvent or dispersion medium used in the slurry.

Japanese Unexamined Patent Publication No. 2014-007138

However, the present researchers have found that the capacity of an all-solid-state battery manufactured using butyl butyrate as a solvent or dispersion medium may decrease when charging and discharging are repeated.
In view of the above circumstances, it is an object of the present disclosure to provide an all-solid-state secondary battery having a high capacity retention rate.

The all-solid-state secondary battery of the present disclosure is an all-solid-state secondary battery including a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer, and the all-solid-state battery contains butyl butyrate and has the positive electrode activity. When the total mass of the material layer, the negative electrode active material layer, and the solid electrolyte layer is 100% by mass, the content ratio of the butyl butyrate exceeds 0% by mass and is 0.158% by mass or less. do.

According to the present disclosure, it is possible to provide an all-solid-state secondary battery having a high capacity retention rate.

It is a schematic diagram of the structural example of the all-solid-state secondary battery of this disclosure. It is a graph which shows the relationship between the content ratio of butyl butyrate and the specific volume retention rate (%) when the total mass of a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer is 100% by mass. It is a graph which shows the relationship between the content ratio of butyl butyrate and the initial discharge specific volume when the total mass of a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer is 100% by mass.

The all-solid secondary battery of the present disclosure is an all-solid secondary battery including a negative electrode active material layer, a positive electrode active material layer, and a solid electrolyte layer, and the all-solid secondary battery contains butyl butyrate. When the total mass of the negative electrode active material layer, the positive electrode active material layer, and the solid electrolyte layer is 100% by mass, the content ratio of the butyl butyrate exceeds 0% by mass and is 0.158% by mass or less. It is a feature.

Butyl butyrate has the characteristics of low reactivity with solid electrolyte under general conditions, slow settling rate when the electrode material is dispersed or dissolved in a solvent, and moderate volatilization speed. It is known that it is suitable as a solvent when an electrode is produced using a dispersed or dissolved slurry.

Further, such a solvent is removed by drying or the like after being formed into an electrode shape using a slurry, but it is difficult to completely remove such a solvent from the viewpoint of manufacturing efficiency, etc., and one of them is contained in the obtained electrode. It is known that the part remains. In a battery manufactured using butyl butyrate as a solvent, if a small amount of butyl butyrate remains, it has a positive effect on the dispersibility of the raw material and the migration of the binder in the electrode, and a relatively large amount remains. Even in this case, it has been considered preferable because it has a smaller effect on the performance such as the discharge capacity of the battery as compared with other solvents.

However, as a result of further studies, the researchers found that in an all-solid-state battery using a solid electrolyte, the capacity retention rate may decrease if more than a specific amount of butyl butyrate remains in the battery. bottom.
The mechanism by which butyl butyrate reduces the capacity retention rate is not clear, but analysis of all-solid-state secondary batteries in which the reduction in capacity retention rate was confirmed revealed that the solid electrolyte particles in the electrode active material layer were porous. ) The part that has become is confirmed. From this, when a high potential is repeatedly applied to the electrode due to charging and discharging, the solid electrolyte particles react with butyl butyrate remaining in a specific amount or more, the solid electrolyte particles deteriorate and the resistance increases, so that the capacity retention rate decreases. It is estimated that.

In the all-solid-state secondary battery of the present disclosure, it is considered that the decrease in the capacity retention rate can be suppressed by setting the content of butyl butyrate in a range lower than the residual amount allowed in the conventional battery.
Hereinafter, the all-solid-state secondary battery of the present disclosure will be described in detail.

(1) Negative electrode active material layer In the all-solid secondary battery of the present disclosure, the negative electrode active material layer is not particularly limited as long as it functions as the negative electrode of the all-solid secondary battery together with the current collector, but is usually a negative electrode. It contains active materials and, if necessary, other components such as solid electrolytes, binders, and conductive materials.
As shown in FIG. 1, the negative electrode 3 usually has a negative electrode current collector 3-2 and a negative electrode active material layer 3-1 and has a solid electrolyte layer 1 and a negative electrode active material layer 3 on a side surface opposite to the positive electrode 2. -1 is bonded, and further, the negative electrode active material layer 3-1 and the negative electrode current collector 3-2 are bonded on the side surface opposite to the solid electrolyte layer 1.

The negative electrode current collector used in the present disclosure is not particularly limited as long as it can be used for an all-solid-state secondary battery. The material of the negative electrode current collector may be at least one metal material selected from the group consisting of Al, Zn, Sn, Ni, SUS, and Cu. As long as the surface of the negative electrode current collector is made of the above material, the inside may be made of a material different from the surface. When the battery of the present disclosure is a Li ion battery, Ni or SUS may be used from the viewpoint of Li reduction resistance. The shape of the negative electrode current collector can be, for example, a foil shape, a plate shape, a mesh shape, a punching metal shape, a foam, or the like.

(Negative electrode active material)
In the present disclosure, the negative electrode active material functions as a negative electrode active material in the battery chemical reaction in relation to the positive electrode active material in the all-solid secondary battery, and promotes an electrochemical reaction accompanied by the movement of the metal element M ion. As long as it is a substance, it can be used as a negative electrode active material without particular limitation, and a material conventionally known as a negative electrode active material of an all-solid secondary battery can also be used in the present disclosure.
Examples of raw materials for the negative electrode active material include carbon-based active materials such as graphite, hard carbon, and CNT, alloy-based active materials such as Si alloy-based active materials, Sn alloy-based active materials, and lithium titanate. And so on.

In the negative electrode used with the alloy-based active material, the volume change due to charging and discharging is large. As described above, in the fragile solid electrolyte particles contained in the all-solid-state secondary battery of the prior art, which are porous due to charging and discharging, the particle structure itself is destroyed by the volume change, so that the capacity retention rate is greatly affected.
Therefore, the all-solid-state secondary battery of the present disclosure in which the content ratio of butyl butyrate is set to be low is considered to be highly effective in a negative electrode using an alloy-based active material as the negative electrode active material.

The ratio of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is, for example, 40% by mass or more, may be in the range of 50% by mass to 90% by mass, and is 50% by mass to 90% by mass. It may be in the range of 70% by mass.
The shape of the negative electrode active material is also not particularly limited, and examples thereof include a particle-like shape and a film-like shape, and may be a particle-like shape.

(Solid electrolyte)
The solid electrolyte used for the negative electrode active material layer in the present disclosure is not particularly limited as long as it can be used for an all-solid secondary battery. For example, when the battery of the present disclosure is a Li ion battery, an oxide-based amorphous solid electrolyte, a sulfide-based amorphous solid electrolyte, a crystalline oxide / nitride, etc. having high Li ion conductivity may be used. It is preferably used.
Examples of the oxide-based amorphous solid electrolyte include Li ₂ O-B ₂ O _3- P ₂ O ₃ , Li ₂ O-SiO _{2, and the} like, and examples of the sulfide-based amorphous solid electrolyte include Li 2 O-B 2 O 3-P 2 O 3. For example, Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ S-P ₂ S ₅ , LiI-Li ₃ PO _4- P ₂ S ₅ , Li ₂ S-P ₂ S _5, etc. Can be mentioned. Examples of the crystalline oxide / nitride include Li I, Li ₃ N, Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li _{6 BaLa 2} Ta ₂ O ₁₂ , and Li ₃ PO. _{(4-3 / 2w)} N _w (w <1), Li _3.6 Si _0.6 P _0.4 O _{4 and the} like can be mentioned.
Compared with the oxide-based solid electrolyte, the sulfide-based solid electrolyte is more likely to become porous with charge and discharge.
Therefore, it is considered that the all-solid-state secondary battery of the present disclosure in which the content ratio of butyl butyrate is set to be low is highly effective when a sulfide-based solid electrolyte is used as the solid electrolyte.
The ratio of the solid electrolyte in the negative electrode active material layer is not particularly limited, but is, for example, 10% by mass or more, may be in the range of 20% by mass to 50% by mass, and 25% by mass to 45%. It may be in the range of mass%.
The shape of the solid electrolyte is also not particularly limited, and examples thereof include a particle-like shape and a film-like shape, and may be a particle-like shape.

(Conductive material)
The conductive material used for the negative electrode active material layer in the present disclosure is not particularly limited as long as it can be used for an all-solid-state secondary battery. For example, the raw material of the conductive material may be at least one carbon-based material selected from the group consisting of carbon black such as acetylene black and furnace black, carbon nanotubes, and carbon nanofibers.
From the viewpoint of electron conductivity, it may be at least one carbon-based material selected from the group consisting of carbon nanotubes and carbon nanofibers, and the carbon nanotubes and carbon nanofibers are VGCF (gas phase carbon fibers). ) May be.
The ratio of the conductive material in the negative electrode active material layer is not particularly limited, but may be, for example, 1.0% by mass or more, and may be in the range of 1.0% by mass to 12.0% by mass. , 2.0% by mass to 10.0% by mass.

(Binder)
The negative electrode active material layer may further contain a binder, if necessary.
As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), butylene rubber (BR), styrene-butadiene rubber (SBR), polyvinyl butyral (PVB), acrylic resin and the like can be used. It can be polyvinylidene fluoride (PVdF).
The ratio of the binder in the negative electrode active material layer is not particularly limited, but may be, for example, in the range of 0.1 to 10% (vol / vol), and may be in the range of 1 to 5% (vol / vol /). It may be within the range of vol).

The method for producing the all-solid-state secondary battery of the present disclosure is not particularly limited, but usually at least one of the negative electrode active material layer and the positive electrode active material layer described later uses butyl butyrate as a solvent as a raw material for the electrode. Manufactured using suspended slurries. Both the negative electrode active material layer and the positive electrode active material layer may be produced by using a slurry in which the raw material of the electrode is suspended in butyl butyrate as a solvent.
When only the negative electrode active material layer is produced using a slurry in which the electrode raw material is suspended in butyl butyrate as a solvent, a solid electrolyte layer in which the electrode raw material is suspended in butyl butyrate as a solvent will be described later. When the total mass of the negative electrode active material layer, the positive electrode active material layer, and the solid electrolyte layer is 100% by mass, the butyric acid is finally applied and dried on the above or on the negative electrode current collector. It is manufactured so that the butyl content is removed until it exceeds 0% by mass and becomes 0.158% by mass or less.
When both the negative electrode active material layer and the positive electrode active material layer are produced using a slurry in which the electrode raw material is suspended in butyl butyrate as a solvent, a slurry in which the electrode raw material is suspended in butyl butyrate as a solvent. Was applied and dried on the solid electrolyte layer or the negative electrode current collector, and finally, the total mass of the negative electrode active material layer, the positive electrode active material layer, and the solid electrolyte layer was set to 100% by mass. Occasionally, it is manufactured so that the content of butyl butyrate in the negative electrode active material layer and the positive electrode active material layer is removed until it exceeds 0% by mass and becomes 0.158% by mass or less.
Further, the negative electrode active material layer may be formed on a support other than the solid electrolyte layer or the current collector. In that case, the negative electrode active material layer is peeled from the support, and the peeled negative electrode active material layer is bonded onto the solid electrolyte layer or the negative electrode current collector.

Further, only the positive electrode active material layer is produced by using a slurry in which the electrode raw material is suspended in butyl butyrate as a solvent, and the negative electrode active material layer is manufactured by suspending the electrode raw material in butyl butyrate as a solvent. When it is produced without using it, for example, the powder of the raw material for the negative electrode active material layer may be compression-molded. In the case of compression molding, for example, the negative electrode active material layer may be produced by adding powder of the raw material for the negative electrode active material layer, depositing the powder to a uniform thickness, and compression molding.
When the powder of the raw material for the negative electrode active material layer is compression-molded, a press pressure of about 400 to 1000 MPa is usually applied. Further, compression molding may be performed using a roll press, in which case the linear pressure may be set to 10 to 100 kN / cm.

(2) Positive Electrode Active Material Layer In the all-solid secondary battery of the present disclosure, the positive electrode active material layer is not particularly limited as long as it functions as the positive electrode of the all-solid secondary battery together with the current collector, but is usually a metal. It contains a positive electrode active material containing the element M, and if necessary, contains other components such as a binder, a solid electrolyte, and a conductive material. For example, as shown in FIG. 1, in the present disclosure, the positive electrode 2 is a positive electrode active material layer 2 containing the positive electrode active material and, if necessary, other components such as a binder, a solid electrolyte, and a conductive material. It may have -1 and a positive electrode current collector 2-2.
The current collector of the positive electrode is not particularly limited, and for example, Cu and a copper alloy, and Cu plated or vapor-deposited with Ni, Cr, C or the like can be used.
In the present disclosure, the positive electrode active material is not particularly limited as long as it is an active material containing the metal element M. Any substance that functions as a positive electrode active material in the battery chemical reaction in relation to the negative electrode active material and promotes the battery chemical reaction accompanied by the movement of the above-mentioned metal element M ion is used as the positive electrode active material without particular limitation. A substance conventionally known as a positive electrode active material for an all-solid secondary battery can also be used in the present disclosure.
For example, when the all-solid secondary battery of the present disclosure is an all-solid lithium ion secondary battery, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and manganese can be used as raw materials for the positive electrode active material. Lithium oxide (LiMn ₂ O ₄ ), Li _{1 + x} Ni _1/3 Mn _1/3 Co _1/3 O ₂ , Li _{1 + x} Mn _2-xy L _y O ₄ (L is Al, Mg, Co, Fe, Ni , different element substituted Li-Mn spinel composition represented by selected one or more elements are) from Zn, lithium titanate _(Li x _TiO y), phosphate metal lithium _{(LiLPO 4, L = Fe,} Mn, Co , Ni, etc.) and the like.
The positive electrode active material may have a coating layer having M ion conductivity and containing a substance that does not flow even when in contact with the active material or a solid electrolyte. When the battery of the present disclosure is a Li ion battery, examples of the substance include LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , and Li ₃ PO ₄ .
The shape of the positive electrode active material is not particularly limited, but may be in the form of a film or particles.
The ratio of the positive electrode active material in the positive electrode is not particularly limited, but is, for example, 60% by mass or more, may be in the range of 70% by mass to 95% by mass, and 80% by mass to 90% by mass. It may be within the range of.

The raw material of the solid electrolyte used in the positive electrode active material layer is not particularly limited as long as it can be used in an all-solid secondary battery, but the conduction of M ions is the same as the raw material of the solid electrolyte used in the negative electrode. Oxide-based amorphous solid electrolytes, sulfide-based amorphous solid electrolytes, crystalline oxides / nitrides, and the like having a high degree of degree are preferably used.
As the raw materials for the conductive material and the binder, the same materials as those used for the negative electrode can be used.
For example, the positive electrode active material layer can be produced by the same method as the negative electrode active material layer.

(3) Solid Electrolyte Layer The solid electrolyte layer is not particularly limited as long as it also contains an M ion conductive solid electrolyte raw material and functions as a solid electrolyte layer of an all-solid secondary battery, but is usually the M ion. In addition to the conductive solid electrolyte raw material, it contains other components such as a binder, if necessary.
As the raw materials for the solid electrolyte and the binder, the same materials as those used for the positive electrode and the negative electrode can be used.
The ratio of the solid electrolyte raw material in the solid electrolyte layer is not particularly limited, but is, for example, 50% by mass or more, may be in the range of 70% by mass to 99.99% by mass, and 90% by mass. It may be in the range of ~ 99.9% by mass.

Examples of the method for forming the solid electrolyte layer include a method of compression molding a powder of a solid electrolyte material containing a solid electrolyte raw material and, if necessary, other components. When the powder of the solid electrolyte material is compression-molded, a press pressure of about 400 to 1000 MPa is usually applied as in the case of compression-molding the raw material powder of the negative electrode mixture. Further, compression molding may be performed using a roll press, in which case the linear pressure may be set to 10 to 100 kN / cm.
Further, as another method, a cast film forming method using a solution or dispersion of a solid electrolyte raw material and a solid electrolyte material containing other components as needed can be performed.

4. All-solid-state secondary battery The all-solid-state secondary battery of the present disclosure is an all-solid-state battery including a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer, and the all-solid-state battery contains butyl butyrate. When the total mass of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is 100% by mass, the content ratio of the butyl butyrate exceeds 0% by mass and is 0.158% by mass or less. It is characterized by. The content ratio of the butyl butyrate is preferably in the range of 0.05 to 0.158% by mass, more preferably in the range of 0.05 to 0.95% by mass.
In the all-solid-state battery of the present disclosure, the cycle characteristics can be improved by limiting the content of butyl butyrate contained in the all-solid-state battery to the above-mentioned specific range lower than the range allowed by the solid-state battery of the prior art. It has become possible.

The all-solid-state secondary battery of the present disclosure typically comprises a positive electrode 2, a negative electrode 3, and a solid electrolyte layer 1 arranged between the positive electrode 2 and the negative electrode 3, as shown in FIG. It is configured as a positive electrode-solid electrolyte layer-negative electrode aggregate 101.
The positive electrode-solid electrolyte layer-negative electrode aggregate 101 becomes a cell which is a functional unit. The cell may be used as it is as the all-solid-state secondary battery of the present disclosure, or may be used as an all-solid-state secondary battery of the present disclosure as a cell aggregate by integrating and electrically connecting a plurality of cells. good.
The thickness of each of the positive electrode active material layer and the negative electrode active material layer is usually about 0.1 μm to 10 mm, and the thickness of the solid electrolyte layer is usually about 0.01 μm to 1 mm.

The method for producing the battery is not particularly limited, and the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector manufactured as described above are arranged in this order. It may be joined in the state of being arranged in.

1. 1. Manufacture of an all-solid-state secondary battery [Example 1]
(1) Manufacture of negative electrode Li _{2 SP 2} S ₅ system amorphous solid electrolyte containing LiBr and LiI which are solid electrolyte materials 400 mg, Si single particles which are negative electrode active material 500 mg, PVdF which is a binder 1200 mg of a 5 mass% butyl butyrate solution of the system resin and 40 mg of VGCF, which is a conductive additive material, were added to the polypropylene container. The container was ultrasonically treated in an ultrasonic disperser for 30 seconds and then permeated for 30 minutes using a shaker to prepare a slurry for forming a negative electrode active material layer.
The slurry for forming the negative electrode active material layer thus prepared was applied onto a Cu foil as a current collector by a blade method using an applicator, and dried on a hot plate adjusted to 100 ° C. for 30 minutes.

_{(2) Preparation of positive electrode Li Ni 1/3} Co _{1 containing 350 mg of Li 2 SP 2} S ₅ system amorphous solid electrolyte containing LiBr and Li I, which are raw materials for solid electrolytes, and an average particle size of 6 μm, which is a raw material for positive electrode active materials. _{/ 3} Mn _1/3 O ₂ particles 2200 mg, a 5 mass% butyl butyrate solution of PVdF resin as a binder 1400 mg, and a conductive auxiliary agent VGCF 30 mg were added to a polypropylene container. The container was ultrasonically treated in an ultrasonic disperser for 30 seconds and then permeated for 30 minutes using a shaker to prepare a slurry for forming a positive electrode active material layer.
The slurry for forming the positive electrode active material layer thus prepared was applied onto an Al foil as a current collector by a blade method using an applicator, and dried on a hot plate adjusted to 100 ° C. for 30 minutes.

_{(3) Preparation of solid electrolyte layer Li 2 SP 2} S ₅ system amorphous solid electrolyte 500 mg containing LiBr and LiI, which are solid electrolyte raw materials with an average particle size of 1 μm, and butylene rubber system as a binder. 750 mg of a 5 mass% butyl butyrate solution of resin was added to the polypropylene container. The container was ultrasonically treated in an ultrasonic disperser for 30 seconds and then permeated for 30 minutes using a shaker to prepare a slurry for forming a solid electrolyte layer.
The slurry for forming the solid electrolyte layer prepared in this way is applied onto the Al foil as the base by the blade method using an applicator, and dried on a hot plate adjusted to 100 ° C. for 30 minutes to obtain the solid electrolyte layer. Got A total of three solid electrolyte layers were prepared in the same manner.

(4) Preparation of battery In a glove box prepared so that the saturation of butyl butyrate is 50 ppm, the negative electrode is placed in contact with the negative electrode active material layer obtained in (1) and (3) and the solid electrolyte layer. And the solid electrolyte member were laminated. A pressure of 5 kN / cm is applied to the negative electrode member-solid electrolyte layer-aluminum foil laminate using a roll press under the conditions of a gap between rolls of 100 μm and a feed rate of 0.5 m / min for the purpose of densification. bottom. The aluminum foil used as the base of the solid electrolyte layer was peeled off to obtain a negative electrode-solid electrolyte layer laminate.
The positive electrode and the solid electrolyte layer were laminated so that the positive electrode active material layer obtained in (2) and (3) was in contact with the solid electrolyte layer. A pressure of 5 kN / cm was applied to the positive electrode-solid electrolyte layer-aluminum foil laminate using a roll press under the conditions of a gap between rolls of 100 μm and a feed rate of 0.5 m / min for the purpose of densification. .. The aluminum foil used as the base of the solid electrolyte layer was peeled off to obtain a positive electrode-solid electrolyte layer laminate.
The solid electrolyte layer prepared in (3) was further laminated on the negative electrode-solid electrolyte layer laminate so that the solid electrolyte layers were in contact with each other, and then the aluminum foil used as the base was peeled off from the solid electrolyte layer prepared in (3). ..
The positive electrode-solid electrolyte layer laminate is located on the negative electrode-solid electrolyte layer laminate to which this solid electrolyte layer is transferred, and the solid electrolyte layers are superposed so as to be in contact with each other, and the pressure is 200 MPa at 130 ° C. Was applied for 1 minute to obtain a battery (25 cm × 6 cm) having a current collector.
The battery thus obtained was held in a glove box prepared so that the saturation of butyl butyrate was 50 ppm for 30 minutes, and then a sealable jig was installed on the battery to restrain the pressure at 20 MPa. Was given.

The battery obtained as described above was first charged by energizing the battery at 1.0 C with a constant current up to 4.55 V and then energizing with a constant voltage up to a final current of 1/100 C. The lithium-ion solid-state battery of Example 1 was obtained by discharging the battery after the initial charge at a constant current of 1.0 C to 2.5 V and then discharging the battery at a constant voltage up to a final current of 1/100 C.

[Example 2]
A lithium ion solid-state battery of Example 2 was produced in the same manner as in Example 1 except that the battery was held in a glove box prepared so that the saturation of butyl butyrate was 350 ppm.

[Comparative Example 1]
Lithium-ion solid of Comparative Example 1 as in Example 1 except that all butyl butyrate used as a solvent in Example 1 was replaced with heptane and the saturation of butyl butyrate in the glove box was set to 0 ppm. A battery was manufactured.

[Comparative Example 2]
A lithium ion solid-state battery of Comparative Example 2 was produced in the same manner as in Example 1 except that the battery was held in a glove box prepared so that the saturation of butyl butyrate was 850 ppm.

[Comparative Example 3]
A lithium ion solid-state battery of Comparative Example 3 was produced in the same manner as in Example 1 except that the battery was held in a glove box prepared so that the saturation of butyl butyrate was 1700 ppm.

[Comparative Example 4]
A lithium ion solid-state battery of Comparative Example 4 was produced in the same manner as in Example 1 except that the battery was held in a glove box prepared so that the saturation of butyl butyrate was 2000 ppm.

2. Evaluation of all-solid-state battery (1) Evaluation of cycle characteristics The all-solid-state lithium-ion secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 4 were subjected to constant current-constant voltage discharge. First, the all-solid-state lithium-ion secondary battery obtained as described above was discharged (termination current 1 / 100C). The discharged battery is charged at a rate of 3 hours (1 / 3C) to a predetermined voltage under constant voltage-constant current conditions, then discharged under constant current-constant voltage discharge conditions, and the discharge capacity of the first cycle. Was measured.
Under the same conditions, the charge / discharge cycle was repeated for 5 cycles, and the discharge capacity at the 5th cycle was measured.
The capacity retention rate in the 5th cycle was calculated by dividing the discharge capacity in the 5th cycle by the discharge capacity in the 1st cycle.

3. 3. Results Table 1 shows the type of solvent used in battery production, the content ratio of butyl butyrate when the total mass of the negative electrode active material layer, the positive electrode active material layer, and the solid electrolyte layer is 100% by mass, and all of Comparative Example 1. The 1st cycle specific capacity of each battery when the 1st cycle capacity of the solid lithium ion secondary battery is 100%, and the 5th cycle capacity retention rate of each battery of the all solid lithium ion secondary battery of Comparative Example 1. Is shown as the 5th cycle specific capacity retention rate when is set to 100%.

As shown in Table 1, assuming that the 5-cycle capacity retention rate of the battery of Comparative Example 1 having no butyl butyrate is 100%, the batteries of Comparative Examples 2 to 4 having a butyl butyrate content of 0.166% or more. The 5-cycle specific capacity retention rate was 99% or less.

On the other hand, the 5-cycle specific capacity retention rate of the battery of Example 1 in which the content ratio of butyl butyrate is 0.05% is 110%, and the content ratio of butyl butyrate is 0.095% in 5 cycles of Example 2. The specific capacity retention rate was as high as 109%.
As shown in FIG. 2, in the range where the content ratio of butyl butyrate exceeds 0% by mass and is 0.158% by mass or less, the 5-cycle specific volume retention rate exceeds 100% and has a high volume retention rate. It was confirmed that it was an all-solid-state secondary battery.

As shown in Table 1 and FIG. 3, when the specific volume of the first cycle is compared, there is no significant influence on the volume until the content ratio of butyl butyrate exceeds 0.285% by mass. For this reason, it is considered that conventionally, it was determined that butyl butyrate does not affect the battery performance if it is 0.285% by mass or less.

From the above results, it is an all-solid secondary battery including a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer. The all-solid-state battery contains butyl butyrate, and the positive electrode active material layer and the negative electrode. The present disclosure is characterized in that, when the total mass of the active material layer and the solid electrolyte layer is 100% by mass, the content ratio of the butyl butyrate exceeds 0% by mass and is 0.158% by mass or less. It was revealed that the all-solid-state secondary battery has a high capacity retention rate.

1 Solid electrolyte layer 2 Positive electrode 2-1 Positive electrode active material layer 2-2 Positive electrode current collector 3 Negative electrode 3-1 Negative electrode active material layer 3-2 Negative electrode current collector 101 All-solid secondary battery

Claims (1)

An all-solid-state secondary battery including a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer.
The all-solid-state secondary battery contains butyl butyrate, and when the total mass of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is 100% by mass, the content ratio of the butyl butyrate is 0. An all-solid-state secondary battery characterized by having an amount of 050% by mass or more and 0.095% by mass or less.

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