JP2019114348A - All solid secondary battery - Google Patents

Abstract

To provide an all solid secondary battery which has a negative electrode including an Si alloy-based active material and in which an increase in internal resistance due to charge and discharge is suppressed.SOLUTION: In an all solid secondary battery including a positive electrode, a negative electrode and a solid electrolyte layer disposed between the positive electrode and the negative electrode, the negative electrode has a negative electrode collector and a negative electrode mixture layer disposed between the negative electrode collector and the solid electrolyte layer. The negative electrode mixture layer contains an Si alloy-based active material and a solid electrolyte, and, when the negative electrode mixture layer in a state-of-discharge is divided by a plane composed of the center points of the shortest distance between a solid electrolyte layer interface and a negative electrode collector interface, the Si content on a collector side is more than that on an electrolyte layer side.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to an all solid secondary battery.

  The Si-containing active material (Si alloy-based active material) capable of forming an alloy with Li etc. has a large theoretical capacity per volume compared to a carbon-based negative electrode active material. An all solid secondary battery using a substance for the negative electrode has been proposed.

  Patent Document 1 discloses an all-solid lithium ion battery including a negative electrode composite material for a secondary battery using an alloy active material having an average particle diameter of 10 μm or less as a negative electrode active material powder, and a negative electrode layer containing the negative electrode active material powder. Is disclosed.

JP, 2013-069416, A

However, in the all solid secondary battery using the Si alloy based active material as the negative electrode active material described in Patent Document 1, there is a problem that the internal resistance increases with charge and discharge.
In view of the above situation, the present disclosure aims to provide an all-solid secondary battery including a negative electrode including a Si alloy-based active material and suppressing an increase in internal resistance associated with charge and discharge.

  The all solid secondary battery of the present disclosure is an all solid secondary battery including a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode is a negative electrode current collector, A negative electrode mixture layer disposed between the negative electrode current collector and the solid electrolyte layer, wherein the negative electrode mixture layer contains a Si alloy active material and a solid electrolyte, and the negative electrode mixture in a discharge state When the layer is divided by a plane constituted by the center point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface, the Si content on the current collector side is larger than the Si content on the electrolyte layer side , It is characterized.

  According to the present disclosure, it is an object of the present invention to provide an all-solid secondary battery which has a negative electrode containing a Si alloy based active material and in which an increase in internal resistance due to charge and discharge is suppressed.

It is a schematic diagram which shows the structural example of an all-solid-state secondary battery. It is a schematic diagram of the negative electrode (mixture material layer) which many Si alloy system active materials are unevenly distributed on the current collector side. It is a schematic diagram of the negative electrode (mixture layer) with which Si alloy system active material is distributed uniformly. It is a schematic diagram of the negative electrode (mixture layer) which many Si alloy system active materials unevenly distribute on the solid electrolyte layer side. It is a figure which shows the electron microscope image of the negative electrode cross section which Si alloy type active material distributes uniformly. It is the electron-beam-diffraction pattern of the Si-alloy type | system | group active material which was made amorphous on the solid electrolyte layer side. It is the electron-beam-diffraction pattern of Si alloy type | system | group active material which hold | maintained the crystallinity by the side of a collector.

  The all solid secondary battery of the present disclosure is an all solid secondary battery including a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode is a negative electrode current collector, A negative electrode mixture layer disposed between the negative electrode current collector and the solid electrolyte layer, wherein the negative electrode mixture layer contains a Si alloy active material and a solid electrolyte, and the negative electrode mixture in a discharge state When the layer is divided by a plane constituted by the center point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface, the Si content on the current collector side is larger than the Si content on the electrolyte layer side , It is characterized.

FIG. 1 shows a configuration example of a general all-solid secondary battery. As shown in FIG. 1, the negative electrode mixture layer 3-1 is disposed between the solid electrolyte layer 1 and the negative electrode current collector 3-2.
The present inventors studied the all-solid secondary battery 101 having the negative electrode mixture layer 3-1 including the Si alloy-based active material and the solid electrolyte as described above, and the negative electrode 3 including the negative electrode current collector 3-2. In the above, it was found that internal resistance was increased as a result of remarkable cracking especially in the solid electrolyte layer side of the negative electrode mixture layer with charge and discharge.

  The present inventors examined the cause of significant cracking on the solid electrolyte layer side of the negative electrode mixture layer, but only the Si alloy based active material on the solid electrolyte layer side is involved in the charge and discharge reaction, It has become clear that the Si alloy based active material on the side of the electrical conductor hardly participates in the charge and discharge reaction.

Here, when using a Si alloy based active material as the negative electrode active material, so-called electrochemical alloying reaction occurs as shown in the following formula (1) at the negative electrode along with charging of the all-solid secondary battery.
Formula (1) xM ⁺ + xe ⁻ + ySi → M _x Si _y
Further, with the discharge of the all-solid secondary battery, in the negative electrode, as shown in the following formula (2), a separation reaction of M ions occurs from the alloy of Si and the metal element M.
Formula (2) M _x Si _y → xM ⁺ + xe ⁻ + ySi
In the all solid secondary battery using the Si alloy based active material as the negative electrode active material, the volume change due to the insertion / detachment reaction of the metal element M shown in the above formulas (1) and (2) is large.

  Therefore, in the negative electrode mixture layer on the side of the solid electrolyte layer containing a large amount of Si alloy active material involved in charge and discharge reaction, the volume change of the Si alloy active material due to charge and discharge reaction is large, and cracks easily occur. In addition, the negative electrode mixture layer on the solid electrolyte layer side hardly participates in the charge / discharge reaction, and therefore, there is little change in volume. Stress generated between the negative electrode mixture layer on the negative electrode collector side and the solid electrolyte does not occur. It is thought that cracking occurs notably because the stress generated at the interface with the above also occurs.

  In the all solid secondary battery of the present disclosure, the content of the Si alloy based active material on the solid electrolyte layer side is reduced, and the content of the Si alloy based active material on the current collector side is increased, and the Si alloy based active material is unevenly distributed. By using the negative electrode mixture layer, the charge / discharge reaction proceeds in the entire negative electrode mixture layer. Therefore, on the solid electrolyte layer side of the negative electrode mixture layer, the volume change of the Si alloy active material due to charge and discharge reaction is reduced, and the stress generated at the interface with the negative electrode mixture layer on the negative electrode collector side and the solid electrolyte layer It can be considered that it is possible to reduce the increase in internal resistance associated with charge and discharge.

  Hereinafter, the all-solid-state secondary battery of the present disclosure will be described in detail.

1. Negative Electrode The negative electrode of the all solid lithium ion battery of the present disclosure has a negative electrode current collector, and a negative electrode mixture layer disposed between the negative electrode current collector and the solid electrolyte layer. As shown in FIG. 1, the negative electrode 3 has a negative electrode current collector 3-2 and a negative electrode mixture layer 3-1, and on the side opposite to the positive electrode 2, the solid electrolyte layer 1 and the negative electrode mixture layer 3-1. The negative electrode mixture layer 3-1 and the negative electrode current collector 3-2 are joined to each other on the side surface opposite to the solid electrolyte layer 1.

1-1. Anode Current Collector The anode current collector used in the present disclosure is not particularly limited as long as it can be used for an all solid 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. In addition, as long as the surface of a negative electrode collector is comprised with the said material, the inside may be comprised with the material different from a surface. When the battery of the present disclosure is a Li-ion battery, Ni or SUS may be used from the viewpoint of resistance to reduction of Li.
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.

1-2. Negative Electrode Mixture Layer In the present disclosure, the negative electrode mixture layer contains a Si alloy-based active material and a solid electrolyte. The negative electrode mixture layer may contain other materials such as a conductive material and a binder as required.

(Si alloy based active material)
In the present disclosure, the Si alloy-based active material includes at least one active material selected from the group consisting of elemental Si and an alloy of elemental Si and the metal element M.
The metal element M is not particularly limited as long as it is a metal that can be inserted into and released from Si in accordance with the so-called electrochemical alloying reaction shown in the above formulas (1) and (2). Examples of the metal M capable of forming an alloy with Si include Li, Na, K, Mg, Ca and the like, and among them, Li, Na or Li may be used.

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

(Solid electrolyte)
The raw material of the solid electrolyte is not particularly limited as long as it can be used for the all solid secondary battery. For example, when the battery of the present disclosure is a Li-ion battery, an oxide-based amorphous solid electrolyte having high conductivity of Li ion, a sulfide-based amorphous solid electrolyte, a crystalline oxide / nitride, etc. 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 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. As the like the crystalline _{oxide-nitride, LiI, 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, Li 3 PO _{(4-3 / 2 w)} N _w (w <1), Li _3.6 Si _0.6 P _0.4 O _{4 and the} like can be mentioned.
The proportion of the solid electrolyte in the negative electrode mixture layer is not particularly limited, but is, for example, 10% by mass or more, and 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 not particularly limited, and examples thereof include a particle shape, a film shape and the like, and may be a particle shape.

(Other ingredients)
The negative electrode mixture layer may contain other components such as a conductive material and a binder in addition to the above components.
Since the energy density is high, the negative electrode mixture layer according to the present disclosure may have a small amount of components other than the Si alloy active material.
The conductive material is not particularly limited as long as it can be used for an all solid secondary battery. For example, 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.
The carbon nanotube may be at least one carbon-based material selected from the group consisting of carbon nanotubes and carbon nanofibers from the viewpoint of electron conductivity, and the carbon nanotubes and carbon nanofibers may be VGCF (vapor grown carbon fibers) ) May be.
The proportion of the conductive material in the negative electrode mixture 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. And 2.0% by mass to 10.0% by mass.

  As the binder, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), butylene rubber (BR), styrene-butadiene rubber (SBR), polyvinyl butyral (PVB), acrylic resin, etc. may be used. And may be polyvinylidene fluoride (PVdF).

(Structure of negative electrode mixture layer)
In the case where the negative electrode mixture layer is divided by a plane constituted by the central point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface in a discharge state, the Si content on the current collector side is the electrolyte layer It is characterized by having more than Si content of the side.

FIG. 3 shows a schematic view of the cross section of the all-solid secondary battery of the prior art in which the Si alloy based active material is uniformly distributed in the negative electrode mixture layer. As shown in FIG. 3, in the discharge state, when the negative electrode mixture layer is a boundary formed by the center point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface, the Si content on the current collector side The Si content on the electrolyte layer side is equal.
A battery of the prior art having such a structure was fabricated, charge and discharge were repeated several times, and then electron microscopic observation and X-ray crystallographic analysis of the cross section were carried out in a discharged state, as shown in FIGS. The single Si particles on the solid electrolyte layer side of the negative electrode mixture layer were amorphous, but the single Si particles on the negative electrode current collector side of the negative electrode mixture layer maintained the crystal structure.
Here, it is known that when crystal particles of simple substance Si are used as a raw material of the Si alloy based active material, the crystalline structure of simple substance Si becomes amorphous while repeating insertion and detachment of metal M by charge and discharge. There is.
Therefore, from FIG. 5 to FIG. 7, in the all solid secondary battery of the prior art, only the Si alloy based active material on the solid electrolyte layer side is involved in the charge and discharge reaction, and the Si alloy based active material on the current collector side is It can be seen that it hardly participates in the charge / discharge reaction.
Since only the Si alloy active material on the solid electrolyte layer side is involved in the charge and discharge reaction, the volume change associated with charge and discharge is concentrated on the solid electrolyte layer side, and cracking occurs in the negative electrode composite material layer. Is considered to increase.

  In the battery of the present disclosure, as shown in FIG. 2, the Si alloy active material is unevenly distributed so that the Si content on the current collector side is larger than the Si content on the electrolyte layer side. By increasing the Si content on the current collector side, the Si alloy active material involved in the charge and discharge reaction increases, and the volume change associated with the charge and discharge also occurs in the entire negative electrode mixture layer. Therefore, stress can be concentrated on a part of the negative electrode mixture layer, and generation of cracks and the like can be prevented, so that it is considered that an increase in internal resistance can be suppressed.

  In the battery shown in FIG. 4 in which the Si alloy active material is unevenly distributed so that the Si content on the electrolyte layer side is larger than the Si content on the current collector side, the Si alloy active material is uniformly distributed. The increase in internal resistance associated with charge and discharge is promoted compared to the prior art all solid secondary battery. Since the amount of the Si alloy-based active material involved in the charge and discharge reaction increases on the electrolyte layer side, it is considered that the volume change associated with the charge and discharge is further concentrated.

  When the negative electrode mixture layer in the discharge state is divided by a plane constituted by the center point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface, the Si content on the current collector side is the electrolyte layer There is no particular limitation on the method of determining whether the content is higher than the Si content on the side.

  For example, the cross section of the battery in a discharged state is observed with an electron microscope as in FIG. 5, and the Si distribution ratio on the electrolyte layer side and the Si distribution ratio on the current collector side can be determined and evaluated according to the following procedure.

(1) In the image observed with an electron microscope, a line constituted by the central point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface is drawn.
(2) A region surrounded by the line constituted by the central point and the solid electrolyte layer interface (solid electrolyte layer side area), and a region surrounded by the line constituted by the central point and the negative electrode current collector interface (negative electrode The area of the current collector side region is calculated respectively.
(3) The cross sectional area of the Si alloy based active material in the solid electrolyte layer side region and the cross sectional area of the Si alloy based active material in the negative electrode current collector side region are respectively calculated.
(4) The ratio of the cross sectional area of the Si alloy based active material to the cross sectional area of the solid electrolyte layer side region and the ratio of the cross sectional area of the Si alloy active material to the cross sectional area of the negative electrode current collector side region are calculated.
(5) The solid electrolyte layer side Si distribution ratio and the negative electrode current collector side Si distribution ratio are calculated from the following calculation formula, and comparison is made.

Calculation formula 1: Solid electrolyte layer side Si distribution ratio = solid electrolyte layer side Si area ratio / (solid electrolyte layer side Si area ratio + negative electrode current collector side Si area ratio) x 100
Calculation formula 2: negative electrode current collector side Si distribution ratio = negative electrode current collector side Si area ratio / (solid electrolyte layer side Si area ratio + negative electrode current collector side Si area ratio) × 100

  In addition, the negative electrode mixture layer is sampled from the battery in a discharged state, and cut by a plane constituted by the central point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface, and elemental analysis is performed on each sample. The content of the Si element may be measured to compare the measured values.

The method for producing the negative electrode mixture layer included in the all solid secondary battery of the present disclosure is not particularly limited as long as it can be produced such that the Si content on the current collector side is greater than the Si content on the electrolyte layer side. For example, the method of compression-molding the powder of the raw material for negative mix is mentioned. In the case of compression molding, for example, powder of a raw material for negative electrode mixture having a relatively small content of Si alloy active material is put into a compression cylinder of powder compression molding, and deposited to a uniform thickness. The powder of the raw material for the negative electrode mixture having a relatively high content of the Si alloy active material is placed on top and deposited to a uniform thickness, and the powder having the two-layer powder deposition layer formed in this way The negative electrode mixture layer may be produced by compression molding the deposited body at one time.
When the powder of the raw material for the negative electrode mixture is compression molded, a pressing pressure of about 400 to 1000 MPa is usually applied. Alternatively, compression molding may be performed using a roll press, and in that case, the linear pressure may be set to 10 to 100 kN / cm.

Alternatively, a dispersion of a material for negative electrode mixture containing a solvent may be coated on a solid electrolyte layer or on a negative electrode current collector and dried to obtain a negative electrode mixture layer.
For example, a coating liquid is formed by applying a dispersion containing a solvent and a raw material for an anode mixture relatively containing a relatively small amount of a Si alloy active material, and a solvent to form a coating film, whereby a relative Si alloy is obtained. After forming a coating film by applying on the negative electrode current collector a dispersion containing a powder of a raw material for a negative electrode mixture having a large content of a system active material, and a solvent, these coated films are overlapped. By drying and bonding in the state, a negative electrode current collector and a negative electrode mixture layer disposed between the negative electrode current collector and the solid electrolyte layer may be obtained.
In addition, the negative electrode mixture layer may be formed on a support other than the solid electrolyte layer and the current collector. In that case, the negative electrode mixture layer is peeled off from the support, and the peeled negative electrode mixture layer is bonded onto the solid electrolyte layer or the negative electrode current collector.

2. Positive Electrode The positive electrode is not particularly limited as long as it contains a positive electrode active material containing a metal element M and functions as a positive electrode of an all solid secondary battery. For example, as shown in FIG. 1, in the present disclosure, the positive electrode 2 includes the positive electrode active material, and, if necessary, a positive electrode mixture layer 2 including other components such as a binder, a solid electrolyte, and a conductive material. 1 and the positive electrode current collector 2-2 may be included.
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. It is not particularly limited as long as it is a substance which functions as a positive electrode active material on battery chemical reaction in relation to the negative electrode active material and advances the battery chemical reaction accompanied by the movement of the metal element M ion described above, and is used as a positive electrode active material And materials conventionally known as positive electrode active materials for all solid secondary batteries can also be used in the present disclosure.
For example, in the case where the all solid secondary battery of the present disclosure is an all solid lithium ion secondary battery, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), manganese as a raw material of 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 (where L is Al, Mg, Co, Fe, Ni , A different element substituted Li-Mn spinel having a composition represented by one or more elements selected from Zn, lithium titanate (Li _x TiO _y ), lithium metal phosphate (LiLPO ₄ , L = Fe, Mn, Co) , Ni, etc.).
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 the 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 film-like or particle-like.
The proportion of the positive electrode active material in the positive electrode is not particularly limited, but is, for example, 60% by mass or more, and may be in the range of 70% by mass to 95% by mass, 80% by mass to 90% by mass It may be in the range of

The raw material of the solid electrolyte used in the positive electrode is not particularly limited as long as it can be used for the all solid secondary battery, but like the raw material of the solid electrolyte used in the negative electrode, the conductivity of M ions is high Oxide-based amorphous solid electrolytes, sulfide-based amorphous solid electrolytes, crystalline oxides, nitrides and the like are preferably used.
As materials for the conductive material and the binder, the same materials as those used in the negative electrode can be used.

As a method of forming a positive electrode mixture layer, for example, a method of compression-molding a powder of a material for a positive electrode mixture can be mentioned. When the powder of the raw material for the positive electrode mixture is compression molded, usually, a pressing pressure of about 400 to 1000 MPa is applied. Alternatively, compression molding may be performed using a roll press, and in that case, the linear pressure may be set to 10 to 100 kN / cm.
Also, for example, after a coating liquid is formed by applying a dispersion containing a raw material for a positive electrode mixture and a solvent on a solid electrolyte layer or a current collector, a method of drying this coating liquid may be used. Good.

3. Solid Electrolyte Layer The solid electrolyte layer is also not particularly limited as long as it contains an M ion conductive solid electrolyte raw material and functions as a solid electrolyte layer of an all solid secondary battery, but usually the M ion conductive solid In addition to the electrolyte raw material, other components such as a binding agent may be included, if necessary.
As materials for the solid electrolyte and the binder, the same materials as used in the positive electrode and the negative electrode can be used.

The proportion of the solid electrolyte material in the solid electrolyte layer is not particularly limited, but is, for example, 50% by mass or more, and may be in the range of 70% by mass to 99.99% by mass, 90% by mass It may be in the range of -99.9% by mass.
Examples of the method of forming a 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 pressing pressure of about 400 to 1000 MPa is usually applied, as in the case of compression molding of the raw material powder of the negative electrode composite material. Alternatively, compression molding may be performed using a roll press, and in that case, the linear pressure may be set to 10 to 100 kN / cm.
Further, as another method, it is possible to carry out a cast film forming method using a solution or dispersion liquid of a solid electrolyte material containing a solid electrolyte raw material and, if necessary, other components.

4. All Solid Secondary Battery The all solid secondary battery of the present disclosure has the positive electrode, the negative electrode, and the solid electrolyte layer disposed between the positive electrode and the negative electrode.
As shown in FIG. 1, the all solid secondary battery of the present disclosure typically includes a positive electrode 2, a negative electrode 3, and a solid electrolyte layer 1 disposed between the positive electrode 2 and the negative electrode 3, A positive electrode-solid electrolyte layer-negative electrode assembly 101 is configured.
The positive electrode-solid electrolyte layer-negative electrode assembly 101 is a cell which is a functional unit. The cell may be used as it is as an all solid secondary battery of the present disclosure, or may be used as an all solid secondary battery of the present disclosure as a cell assembly by integrating and electrically connecting a plurality of cells. Good.
The thickness of each of the positive electrode and the negative electrode 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 mixture layer, the solid electrolyte layer, the negative electrode mixture layer, and the negative electrode current collector manufactured as described above are listed in this order You may join in the state arrange | positioned.
Also, for example, as described above, two raw material powder layers for the negative electrode mixture are formed in the compression cylinder for powder compression molding, and the solid electrolyte powder and the negative electrode material raw material powder deposition layer are formed. If necessary, powder of solid electrolyte layer material containing other components is added and deposited in uniform thickness to form a solid electrolyte layer material powder layer, and the positive electrode active material is deposited on the solid electrolyte layer material powder layer. The powder of the raw material for the positive electrode mixture layer containing the substance is added and deposited to a uniform thickness to form the raw material powder layer for the positive electrode mixture layer, and then the powder having the powder deposition layer of four layers formed in this way The battery may be manufactured by compression-depositing the deposited body at one time and then bonding a current collector.

1. Production of all solid secondary battery [Example 1]
(1) Preparation of Negative Electrode 0.4 g of sulfide solid electrolyte particles represented by the composition of 0.75Li ₂ S-0.25P ₂ S ₅ which is a solid electrolyte material, and having an average particle diameter of 3 μm which is a negative electrode active material 0.8 g of Si single particles, 0.06 g of VGCF as a conductive material, and 0.32 g of a 5 mass% butyl acetate solution of PVDF resin as a binder were added to a polypropylene container. The container was subjected to ultrasonic treatment for 30 seconds in an ultrasonic dispersion apparatus, and then subjected to penetration treatment for 30 minutes using a shaker to prepare a raw material A for a negative electrode mixture having a relatively large negative electrode active material content.
0.7 g of sulfide solid electrolyte particles represented by the composition of 0.75 Li ₂ S-0.25 P ₂ S ₅ which is a solid electrolyte material, and 0.6 g of Si single particles having an average particle diameter of 3 μm which is a negative electrode active material material Then, 0.06 g of VGCF, which is a conductive material, and 0.24 g of a 5% by mass butyl acetate solution of PVDF-based resin, which is a binder, were added to a polypropylene container. The container was subjected to ultrasonic treatment for 30 seconds in an ultrasonic dispersion apparatus, and then subjected to permeation treatment using a shaker for 30 minutes to prepare a raw material B for a negative electrode mixture having a relatively low negative electrode active material content.
The raw material A for the negative electrode mixture having a large content of the negative electrode active material thus prepared was coated on a copper foil as a current collector by a blade method using an applicator and naturally dried for 60 minutes.
Subsequently, the raw material B for the negative electrode mixture having a small content of the negative electrode active material is coated on the surface of the raw material A for the negative electrode mixture naturally dried by the blade method using an applicator, and naturally dried for 60 minutes. I got
The negative electrode precursor thus obtained was dried on a hot plate adjusted to 100 ° C. for 30 minutes.

(2) Preparation of Positive Electrode 0.3 g of sulfide solid electrolyte particles represented by the composition of 0.75Li ₂ S-0.25P ₂ S ₅ which is a solid electrolyte raw material, LiNi _1/3 Co ₁ which is a positive electrode active material raw material _/ 3 _Mn 1/3 _{O 2} particles 2g, a conductive material VGCF0.03G, and was 5 wt% butyl acetate solution 0.3g of PVDF resin as a binder, was added to a polypropylene container. The container was subjected to ultrasonic treatment for 30 seconds in an ultrasonic dispersion apparatus, and then treated with a shaker for 30 minutes to prepare a raw material for positive electrode mixture.
The raw material for positive electrode mixture prepared in this manner was coated on an aluminum foil as a current collector by a blade method using an applicator, and naturally dried for 60 minutes to obtain a positive electrode precursor.
The positive electrode precursor thus obtained was dried on a hot plate adjusted to 100 ° C. for 30 minutes.

(3) Preparation of solid electrolyte layer 0.4 g of a solid electrolyte represented by the composition of 0.75 Li ₂ S-0.25 P ₂ S ₅ having an average particle diameter of 2 μm, which is a solid electrolyte raw material, and a binder 0.05 g of a 5% by mass heptane solution of an ABR resin was added to a polypropylene container. The container was subjected to ultrasonic treatment in an ultrasonic dispersion device for 30 seconds, and then treated with a shaker for 30 minutes to prepare a paste for a solid electrolyte layer.
The solid electrolyte layer paste prepared in this manner is applied onto the base Al foil by a blade method using an applicator, and dried for 30 minutes on a hot plate adjusted to 100 ° C. to obtain a solid electrolyte layer. Obtained.

(4) Fabrication of Battery The negative electrode obtained in (1) to (3), the solid electrolyte layer, and the positive electrode were laminated in this order so as to be in contact with each other. A pressure of 200 MPa at 130 ° C. was applied for 3 minutes to the negative electrode-solid electrolyte layer-positive electrode laminate, to obtain an all solid battery of Example 1.
The all-solid-state battery of Example 1 obtained as described above was energized at a constant current at 0.1 C to a predetermined voltage to perform initial charging.

Comparative Example 1
An all solid secondary battery of Comparative Example 1 was produced in the same manner as Example 1 except that the negative electrode was produced as follows.
0.62 g of solid electrolyte particles represented by the composition of 0.75 Li ₂ S-0.25 P ₂ S ₅ which is a solid electrolyte material, 0.8 g of Si single particles having an average particle diameter of 3 μm which is a negative electrode active material material, 0.06 g of VGCF which is a material, and 0.32 g of a 5% by mass butyl acetate solution of PVDF-based resin which is a binder were added to a polypropylene container. The container was subjected to ultrasonic treatment for 30 seconds in an ultrasonic dispersion device, and then permeabilized for 30 minutes using a shaker to prepare a raw material C for negative electrode mixture.
The raw material C for negative electrode mixture thus prepared was coated on a copper foil as a current collector by a blade method using an applicator, and then naturally dried for 60 minutes to obtain a negative electrode precursor.
The negative electrode precursor thus obtained was dried on a hot plate adjusted to 100 ° C. for 30 minutes.

Comparative Example 2
An all solid secondary battery of Comparative Example 2 was produced in the same manner as Example 1, except that the negative electrode was produced as follows.
Raw material B for a negative electrode mixture having a small content of negative electrode active material prepared as in Example 1 was coated on a copper foil as a current collector by a blade method using an applicator, and naturally dried for 60 minutes.
Subsequently, the raw material A for the negative electrode mixture having a large content of the negative electrode active material is coated on the surface of the naturally dried raw material B for the negative electrode mixture by the blade method using an applicator and naturally dried for 60 minutes. I got
The negative electrode precursor thus obtained was dried on a hot plate adjusted to 100 ° C. for 30 minutes.

2. Evaluation 2-1. Calculation of solid electrolyte layer side Si distribution ratio and negative electrode current collector side Si distribution ratio Conducting electron microscope observation about the discharge state (SOC 0%) battery cross section, according to the following procedure, solid electrolyte layer side Si distribution ratio and negative electrode current collection The body side Si distribution ratio was calculated.
(1) In the image observed with an electron microscope, a line composed of the central point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface was drawn.
(2) A region surrounded by the line constituted by the central point and the solid electrolyte layer interface (solid electrolyte layer side area), and a region surrounded by the line constituted by the central point and the negative electrode current collector interface (negative electrode The area of the current collector side region was measured.
(3) The cross sectional area of the Si alloy based active material in the solid electrolyte layer side region and the cross sectional area of the Si alloy based active material in the negative electrode current collector side region were each measured.
(4) The ratio of the cross-sectional area of the Si alloy based active material to the cross-sectional area of the solid electrolyte layer side region and the ratio of the cross-sectional area of the Si alloy based active material to the cross-sectional area of the negative electrode current collector side region were calculated.
(5) The solid electrolyte layer side Si distribution ratio and the negative electrode current collector side Si distribution ratio were calculated from the following calculation formula, and comparisons were made.

Calculation formula 1: Solid electrolyte layer side Si distribution ratio = solid electrolyte layer side Si area ratio / (solid electrolyte layer side Si area ratio + negative electrode current collector side Si area ratio) x 100
Calculation formula 2: negative electrode current collector side Si distribution ratio = negative electrode current collector side Si area ratio / (solid electrolyte layer side Si area ratio + negative electrode current collector side Si area ratio) × 100

2-2. Deterioration Test A deterioration test was performed on the all solid secondary batteries of Example 1 and Comparative Examples 1 and 2.
The all solid lithium ion secondary batteries of Examples 1 to 5 and Comparative Example 1 charged as described above were discharged (ending current 1/100 C). The battery after discharge was charged at a constant current to 4.1 V at 2 C and discharged at a constant current to 3.1 V. The internal resistance at 3.4 V was measured for the all solid state battery after the end of the first cycle.
Under the same conditions, a deterioration test in which charge and discharge cycles were repeated for 14 days was conducted, and the internal resistance at 3.4 V was measured on the all solid battery after the deterioration test.
Using the internal resistance value of the first cycle obtained as described above and the internal resistance value after the deterioration test, the internal resistance increase rate was calculated from the following formula 3.

  Formula 3: Internal resistance increase rate (%) = internal resistance value after deterioration test / internal resistance value at first cycle × 100

3. Results In Table 1, the internal resistance increase of each all solid battery when the solid electrolyte layer side Si distribution ratio, the negative electrode collector side Si distribution ratio, and the internal resistance increase rate of the all solid battery of Comparative Example 1 are 1, Indicates the percentage of the rate. In addition, the quantity of Si alloy type active material contained in the negative electrode compound material layer of each all-solid-state battery is equal.

As shown in Table 1, in the all-solid-state battery of Comparative Example 1, the Si distribution ratio on the solid electrolyte layer side and the Si distribution ratio on the negative electrode current collector side are each 50%, and in the negative electrode mixture layer, the Si alloy active material Were distributed uniformly.
On the other hand, in the all solid battery of Example 1, the Si distribution ratio on the solid electrolyte layer side is 46% and the Si distribution ratio on the negative electrode current collector side is 54%, and the Si alloy on the current collector side in the negative electrode mixture layer The amount of the active material was larger than that of the Si alloy active material on the solid electrolyte layer side.

  When the internal resistance increase rate of the all-solid battery of Comparative Example 1 is 1, the internal resistance increase rate of the all-solid battery of Example 1 is 0.68, and in the all-solid battery of Example 1, the internal resistivity is It became clear that the increase was suppressed.

  Further, in the all solid battery of Comparative Example 2, the Si distribution ratio on the solid electrolyte layer side is 53%, and the Si distribution ratio on the negative electrode current collector side is 47%, and in the negative electrode mixture layer, the Si alloy system on the solid electrolyte layer side The active material was more than the Si alloy active material on the current collector side.

  When the internal resistance increase rate of the all solid state battery of Comparative Example 1 is 1, the internal resistance increase rate of the all solid state battery of Comparative Example 2 is 1.18, and the all solid state battery of Comparative Example 2 has an internal resistivity of It became clear that the increase was promoted.

  From the above results, it is an all solid secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the negative electrode is a negative electrode current collector, and the negative electrode current collector A negative electrode mixture layer disposed between the body and the solid electrolyte layer, wherein the negative electrode mixture layer contains a Si alloy-based active material and a solid electrolyte, and the negative electrode mixture layer in a discharge state is the solid When divided by a plane constituted by the center point of the shortest distance between the electrolyte layer interface and the negative electrode current collector interface, the Si content on the current collector side is larger than the Si content on the electrolyte layer side The all-solid secondary battery of the present disclosure has been found to have good cycle characteristics.

1 solid electrolyte layer 2 positive electrode 2-1 positive electrode mixture layer 2-2 positive electrode current collector 3 negative electrode 3-1 negative electrode mixture layer 3-2 negative electrode current collector 101 all solid secondary battery

Claims (1)

An all solid secondary battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode,
The negative electrode includes a negative electrode current collector, and a negative electrode mixture layer disposed between the negative electrode current collector and the solid electrolyte layer,
The negative electrode mixture layer contains a Si alloy-based active material and a solid electrolyte, and the negative electrode mixture layer in a discharge state is constituted by a central point of the shortest distance between the solid electrolyte layer interface and the negative electrode current collector interface. In the case of division on the surface side, the Si content on the current collector side is greater than the Si content on the electrolyte layer side,
An all solid secondary battery characterized by