JP2019003901A - Negative electrode material for all solid lithium ion secondary battery, negative electrode member, and manufacturing method of all solid lithium ion secondary battery using the same - Google Patents

Abstract

To provide a negative electrode material suitable for manufacturing an all solid lithium ion secondary battery having a negative electrode containing an alloy of Si and Li as a negative electrode active material and having good cycling characteristics even with a low constraint, and a negative electrode member, and a manufacturing method of all solid lithium ion secondary battery using the same.SOLUTION: There is provided a negative electrode material for an all solid lithium ion secondary battery containing a simple substance of Si having a pore density of 1.5 g/cmor less as a negative electrode active material.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a negative electrode raw material for an all solid lithium ion secondary battery, a negative electrode member, and a method for producing an all solid lithium ion secondary battery using these.

  Since an alloy-based active material containing Si (Si alloy-based active material) has a larger theoretical capacity per volume than a carbon-based negative electrode active material, a lithium ion battery using the Si alloy-based active material as a negative electrode Has been proposed.

  Patent Document 1 discloses a method of manufacturing a solid battery including a negative electrode containing Si as an active material, a positive electrode, and a solid electrolyte. In an example of Patent Document 1, it is described that pressure forming is performed when a positive electrode, a solid electrolyte, and a negative electrode are bonded together.

JP 2013-066941 A

However, according to the study by the present inventors, in order to maintain a high capacity in an all-solid-state lithium ion secondary battery using a simple substance of Si as a negative electrode active material raw material disclosed in Patent Document 1, a large restraint is required. It has been found that it is necessary to apply a high restraint pressure to the battery using a tool, and that the capacity maintenance rate decreases when attempting to reduce the restraint.
In view of the above circumstances, the present disclosure has a negative electrode containing an alloy of Si and Li as a negative electrode active material, and is suitable for the production of an all-solid-state lithium ion secondary battery having good cycle characteristics even at a low restraint pressure. An object of the present invention is to provide a negative electrode member and a method for producing an all solid lithium ion secondary battery using these.

The negative electrode raw material for an all-solid-state lithium ion secondary battery according to the present disclosure contains Si as a negative electrode active material raw material having a density of 1.5 g / cm ³ or less and having pores.
The negative electrode material for an all-solid-state lithium ion secondary battery according to the present disclosure preferably has the Si simple substance having closed pores containing He gas.

The negative electrode member for an all-solid-state lithium ion secondary battery according to the present disclosure contains Si as a negative electrode active material material having a density of 1.5 g / cm ³ or less and having pores.
In the negative electrode member for an all-solid-state lithium ion secondary battery of the present disclosure, it is preferable that the Si simple substance having the pores has closed pores containing He gas.

The manufacturing method of this indication is a manufacturing method of an all-solid-state lithium ion secondary battery provided with the negative electrode containing the alloy of Si and Li as a negative electrode active material, Comprising: The said negative electrode member, a positive electrode member, and a solid electrolyte member are provided. A step of preparing a battery member; and an energization step of energizing the battery member.
In the manufacturing method of the all-solid-state lithium ion secondary battery according to the present disclosure, the all-solid-state lithium ion secondary battery further includes a restraining tool capable of applying a restraining pressure in the arrangement direction of the positive electrode, the solid electrolyte layer, and the negative electrode. A step of applying a first pressure in the arrangement direction of the negative electrode member and the solid electrolyte member to crimp the negative electrode member and the solid electrolyte member, and a restraint pressure of the restraining tool lower than the first pressure. And adjusting to 2 pressures.
In the manufacturing method of the all-solid-state lithium ion secondary battery of this indication, it is preferable that a said 2nd pressure is 7 Mpa or less.

  According to the present disclosure, a negative electrode material and a negative electrode member suitable for manufacturing an all solid lithium ion secondary battery having low cycle pressure and good cycle characteristics, and a method for manufacturing an all solid lithium ion secondary battery using these materials are provided. can do.

3 is a SEM image of a cross section of a single Si film formed in Example 1. FIG. It is an EELS spectrum in the selection part of the Si single-piece | unit film | membrane formed into a film in Example 1. FIG. 6 is a diagram showing a He gas distribution in a cross section of a single Si film formed in Example 1. FIG. 3 is a graph showing the relationship between the number of cycles and the capacity in the cycle characteristic evaluation cell of Example 1. FIG. 4 is a graph showing the relationship between the number of cycles and the capacity in a cycle characteristic evaluation cell of Example 2. 5 is a graph showing the relationship between the number of cycles and capacity in a cycle characteristic evaluation cell of Comparative Example 1; 6 is a graph showing the relationship between the number of cycles and capacity in a cycle characteristic evaluation cell of Comparative Example 2. 10 is a graph showing the relationship between the number of cycles and capacity in a cycle characteristic evaluation cell of Comparative Example 3. 10 is a graph showing the relationship between the number of cycles and capacity in a cycle characteristic evaluation cell of Comparative Example 4;

The negative electrode raw material for an all-solid-state lithium ion secondary battery according to the present disclosure contains Si as a negative electrode active material raw material having a density of 1.5 g / cm ³ or less and having pores.

In a lithium ion secondary battery that uses an alloy of Si and Li as the negative electrode active material, a so-called electrochemical alloying reaction as shown in the following formula (1) occurs in the negative electrode as the lithium ion secondary battery is charged. Happens.
Equation ^{(1) xLi + + xe -} + ySi → Li x Si y
Further, along with the discharge of the lithium ion battery, in the negative electrode, as shown in the following formula (2), the separation reaction of Li ions occurs from the alloy of Si and Li.
Formula (2) Li _x Si _y → xLi ⁺ + xe ⁻ + ySi

In a lithium ion secondary battery using an alloy of Si and Li as a negative electrode active material, the volume change accompanying Li insertion / release reaction shown in the above formulas (1) and (2) is large.
Therefore, in an all-solid-state lithium ion secondary battery that uses a solid electrolyte instead of a fluid electrolyte as an electrolyte, the solid electrolyte layer and the negative electrode that can follow the volume change of the negative electrode itself containing an alloy of Si and Li. It is difficult to form an interface, and peeling or the like occurs at the interface. Therefore, Li ions hardly move between the solid electrolyte and the negative electrode mainly when the negative electrode (alloy of Si and Li) contracts (discharges), and lithium metal is deposited at the interface.
For these reasons, in an all-solid-state lithium ion secondary battery containing an alloy of Si and Li (hereinafter sometimes referred to as an SiLi alloy) as a negative electrode active material, a charge / discharge cycle is performed under low restraint pressure conditions. It is considered that the capacity retention rate decreases when repeated.

  In addition, as described above, by applying a high restraint pressure to the battery, the influence on the interface between the solid electrolyte layer and the negative electrode due to the volume change of the SiLi alloy as the negative electrode active material can be reduced. Therefore, even when a Si alloy active material having a large theoretical capacity per volume was used, the energy density of the entire battery could not be improved.

In the negative electrode raw material and negative electrode member for an all-solid-state lithium ion secondary battery of the present disclosure, the Si simple substance having a density of 1.5 g / cm ³ or less and having pores is used as the negative electrode active material raw material. Therefore, volume expansion associated with an alloying reaction with Li and volume shrinkage associated with a reaction where Li is released from the Li-Si alloy are reduced. Therefore, in the all-solid-state lithium ion secondary battery including the negative electrode manufactured from the negative electrode raw material and the negative electrode member, the volume change of the negative electrode accompanying charge / discharge and the influence on the interface between the solid electrolyte layer and the negative electrode can be reduced. .
For these reasons, in an all-solid-state lithium ion secondary battery including a negative electrode manufactured from the negative electrode material and the negative electrode member of the present disclosure, it is considered that the capacity retention rate can be kept high even at a low restraint pressure. .

  Hereinafter, the negative electrode raw material, the negative electrode member, and the manufacturing method of the all solid lithium ion secondary battery according to the present disclosure will be described in detail in the order.

1. Negative electrode raw material The negative electrode raw material of the present disclosure is a negative electrode raw material used for the production of an all-solid-state lithium ion secondary battery, and includes a Si simple substance having a density of 1.5 g / cm ³ or less as a negative electrode active material raw material. There is no particular limitation as long as it does.
In the energization process described later, the Si simple substance having the pores in the negative electrode member obtained from the negative electrode material of the present disclosure is alloyed with Li by the reaction of the above-described formula (1). A negative electrode containing an alloy of Li and Li is obtained.
It is known that a solid Si simple substance having no pores inside has a volume four times as large as the Li ion insertion reaction of the above formula (1).
Since the negative electrode raw material of the present disclosure uses Si simple substance having pores as the negative electrode active material raw material, by inducing volume expansion in the internal direction of the Si simple substance, it is possible to absorb the volume change accompanying the insertion reaction of Li ions. Therefore, it is possible to reduce the volume change of the Si simple substance having pores as the negative electrode active material raw material and the LiSi alloy as the negative electrode active material.

The Si simple substance having pores contained in the negative electrode material of the present disclosure as the negative electrode active material material has a density of 1.5 g / cm ³ or less. In the case of Si alone having a density exceeding 1.5 g / cm ³ , the number of pores is too small to sufficiently absorb the volume change accompanying alloying. Therefore, in an all-solid-state lithium ion secondary battery manufactured from a negative electrode raw material containing Si alone having a density exceeding 1.5 g / cm ³ as a negative electrode active material, the volume change of the negative electrode accompanying charge / discharge, and the solid electrolyte The influence on the interface of the negative electrode cannot be reduced, and the capacity retention rate cannot be kept high at a low restraint pressure.
Further, from the viewpoint of energy density, the Si simple substance having the pores may have a density of 0.6 g / cm ³ or more, or 1.0 g / cm ³ or more.
In addition, the density of the solid Si simple substance which does not have a pore is about 2.3 g / cm < ³ >.

  In the present disclosure, the density refers to a density calculated by including pores (including internal voids) contained in Si alone as a volume. The density measurement method is not particularly limited, but it can be calculated by dividing the mass of Si alone by the volume of Si alone including pores. For example, when the Si simple substance is a film, the volume of the Si simple substance including the pores can be calculated by the area of the Si simple substance × the thickness of the Si simple substance. It can be measured by an expression profiling system (trade name: Dektak, manufactured by BRUKER) or the like. In addition, for example, when Si is granular, it can be measured by a known method that can measure the volume of Si including pores, such as a bead replacement method.

Si simple substance which the negative electrode raw material of this indication contains as a negative electrode active material raw material has a pore. In the present disclosure, the Si simple substance having pores may be a Si simple substance having a large number of pores.
The distribution of the pores in the Si simple substance is not particularly limited, but the pores may be uniformly distributed in the Si simple substance. Moreover, although there is no restriction | limiting in particular in the size of the said pore, the internal diameter of a pore may be 0.001-1 micrometer and 0.001-0.1 micrometer may be sufficient.

The pores may be closed pores or open pores. Further, the pores may have closed pores in which He gas is included. By having the closed pores in which the He gas is included, a repulsive force against the volume expansion is generated, so that it is possible to reduce the volume expansion associated with charging and discharging.
Although there is no particular limitation on a method for determining whether or not the Si simple substance has closed pores containing He gas, it can be determined by STEM-EELS (Scanning Transmission Electron Microscope-Electron Energy Loss Spectroscopy) observation. .

  The shape of the Si simple substance contained in the negative electrode raw material of the present disclosure as the negative electrode active material raw material is not particularly limited, and examples thereof include Si simple substances such as a film shape and a granular shape. From the viewpoint of energy density, it may be a film.

Moreover, the said Si simple substance may be doped with the trace amount dopant which is metal elements other than Si from a viewpoint of electronic conductivity.
The Si simple substance may be a commercially available one, or may be manufactured and prepared. Although there is no restriction | limiting in particular also in the manufacturing method of the said Si single-piece | unit, What was manufactured by the sputtering method using discharge gas containing He gas may be used.

The negative electrode raw material may include other raw materials such as a conductive material, a solid electrolyte, and a binder as required in addition to the negative electrode active material raw material.
A negative electrode manufactured from a negative electrode raw material having a density of 1.5 g / cm ³ or less as a negative electrode active material raw material and containing a simple substance of Si having pores can absorb a change in volume accompanying charge and discharge. This is because even a negative electrode manufactured from a negative electrode raw material containing any of the above components can reduce a change in volume accompanying charge / discharge.
Examples of the conductive material include carbon materials such as acetylene black and carbon fiber.
The solid electrolyte may be any of a solid electrolyte crystal, an amorphous solid electrolyte, and a solid electrolyte glass ceramic, and the same materials as those of the solid electrolyte member described later can be used.
Examples of the binder include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), butylene rubber (BR), styrene-butadiene rubber (SBR), polyvinyl butyral (PVB), and an acrylic resin. it can.

Since the energy density of the obtained battery increases as the amount of components other than the negative electrode active material raw material decreases, the negative electrode raw material of the present disclosure may include only the negative electrode active material raw material, and the density is 1.5 g. / Si ³ or less, and may include only Si having pores.

  Further, the negative electrode raw material may contain a component other than the negative electrode active material raw material including the Si simple substance having pores, and the conductive material, the solid electrolyte, and the binder raw material contained as necessary. In addition, a component that is removed during the formation of the negative electrode member described later may be included. Examples of the component that is contained in the negative electrode raw material but is removed during the formation of the negative electrode member include a solvent and a removable binder. The removable binder functions as a binder when forming the negative electrode member, but is removed by decomposition or volatilization by firing in the step of obtaining the negative electrode member, and does not include the binder. A binder can be used. Examples of such removable binders include polyvinyl butylfural and acrylic resins.

2. Negative Electrode Member The negative electrode member for an all-solid-state lithium ion secondary battery of the present disclosure contains Si as a negative electrode active material raw material having a density of 1.5 g / cm ³ or less and having pores. Regarding the negative electrode active material and other raw materials contained in the negative electrode member, and preferred compositions, Since it was described in the negative electrode raw material, the description is omitted.

There is no particular limitation on the method for producing the negative electrode member. In a negative electrode manufactured from a negative electrode member using a simple substance of Si having a density of 1.5 g / cm ³ or less and used as a negative electrode active material raw material, the negative electrode as a whole accompanying charge and discharge is used regardless of the manufacturing method. This is because the volume change is considered to be small.

Examples of a method for forming the negative electrode member include a method in which the negative electrode raw material powder is compression-molded. When the negative electrode raw material powder is compression-molded, a press pressure of about 1 to 400 MPa is usually applied.
In addition, a method of removing a binder by compressing and molding a negative electrode raw material powder containing a removable binder, or a solid dispersion of a negative electrode raw material containing a solvent and a removable binder. Examples of the method include a method of removing the binder by firing after forming on the electrolyte member or another support such as a current collector and drying to form the shape of the negative electrode member.

In addition, when the negative electrode member of the present disclosure has only a density of 1.5 g / cm ³ that is a negative electrode active material material and includes only a Si simple film having pores, a discharge gas containing He gas is used. Alternatively, a film may be formed on another support such as a current collector or a solid electrolyte member described later by a sputtering method.

3. Manufacturing method of all-solid-state lithium ion secondary battery The manufacturing method of the all-solid-state lithium ion secondary battery provided with the negative electrode containing the alloy of Si and Li as a negative electrode active material of this indication is the said negative electrode member, a positive electrode member, and solid electrolyte A step of preparing a battery member including the member, and an energization step of energizing the battery member.

3-1. Step of preparing a battery member including a negative electrode member, a positive electrode member, and a solid electrolyte member. Therefore, examples of the positive electrode member, the solid electrolyte member, and the battery member will be described below.

3-1-1. Positive Electrode Member In the production method of the present disclosure, the positive electrode member usually includes a positive electrode active material material containing Li, and optionally includes other positive electrode materials such as a binder, a solid electrolyte, and a conductive material. The positive electrode member becomes a positive electrode of an all-solid lithium secondary battery through an energization process described later.
In the present disclosure, the positive electrode active material raw material containing Li is not particularly limited as long as it is a substance that functions as a positive electrode on the battery chemical reaction in relation to the negative electrode active material and advances the battery chemical reaction accompanied by the movement of Li ions. Any material that can be used as a positive electrode active material, and conventionally known as a positive electrode active material of a lithium ion battery can also be used in the manufacturing method of the present disclosure.
Examples of the positive electrode active material material include lithium-containing metal oxides. Examples of the lithium-containing metal oxide include rock salt layer type active materials such as LiCoO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li (Ni _{0). .5} Mn _1.5) spinel active material _{O 4} or the _like, can be cited LiFePO _4, LiMnPO _4, LiNiPO 4, LiCoPO olivine active material such as _4.
The shape of the positive electrode active material raw material is not particularly limited, but may be a film shape or a particle shape.
The ratio of the positive electrode active material raw material in the positive electrode raw material is not particularly limited, but is, for example, 50% by mass or more, preferably in the range of 60% by mass to 100% by mass, and 70% by mass to 100%. More preferably, it is in the range of mass%.

  As the raw material for the binder, the conductive material, and the solid electrolyte, the same materials as those used for the negative electrode material can be used.

The positive electrode raw material for forming the positive electrode member may further contain a component that is removed during the formation of the positive electrode member. The components that are contained in the positive electrode raw material but are removed during the formation of the positive electrode member include the same components as the solvent that can be contained in the negative electrode raw material and the removable binder.
Examples of the method for forming the positive electrode member include the same methods as the method for forming the negative electrode member.

3-1-2. Solid Electrolyte Member In the manufacturing method of the present disclosure, the solid electrolyte member includes, for example, a solid electrolyte, and includes other components as necessary. The solid electrolyte member becomes a solid electrolyte layer of an all-solid lithium secondary battery through an energization process described later.
As the solid electrolyte, an oxide solid electrolyte having a high Li ion conductivity and a sulfide solid electrolyte are preferably used.
Examples of the oxide-based solid electrolyte include Li _6.25 La ₃ Zr ₂ Al _0.25 O ₁₂ , Li ₃ PO ₄ , LiPON, and the like. Examples of the sulfide-based solid electrolyte include Li ₇ P _{3 S 11, Li 3 PS 4} , Li 8 P 2 S 9, Li 13 GeP 3 S 16, Li 10 GeP 2 S 12 , and the like.

  Although the ratio of the solid electrolyte in a solid electrolyte member is not specifically limited, For example, it is 50 mass% or more, and it is preferable to exist in the range of 60 mass%-100 mass%, and 70 mass%-100 mass. % Is more preferable.

Examples of the method for forming the solid electrolyte member include a method of compression molding a solid electrolyte and a raw material powder for producing a solid electrolyte layer containing other components as necessary. When the powder of the raw material for producing the solid electrolyte layer is compression-molded, a press pressure of about 1 to 400 MPa is usually applied as in the case of compression-molding the powder of the negative electrode material.
Moreover, as another method, the cast film-forming method etc. which used the solution or dispersion liquid of the raw material for solid electrolyte layers manufacture containing a solid electrolyte and another component as needed can be performed.

3-1-3. Battery member In the manufacturing method of the present disclosure, for example, the battery member includes a positive electrode member, a solid electrolyte member, and a negative electrode member arranged in this order, and joined directly or via a portion made of another material. The side opposite to the position where the solid electrolyte member exists on the positive electrode member (outside of the positive electrode mixture) and the side opposite to the position where the solid electrolyte member exists on the negative electrode member (outside of the negative electrode mixture) ) On one side or both sides of each other, an assembly of each part having an array structure in which portions made of other materials may be joined (positive electrode member-solid electrolyte member-negative electrode member assembly). The battery member becomes an all-solid-state lithium ion secondary battery through an energization process described later.
As long as the battery member can be energized in a direction from the positive electrode member side to the negative electrode member side via the solid electrolyte member, a portion made of another material may be attached. Between the positive electrode member and the solid electrolyte member, for example, a coating layer such as LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , or Li ₃ PO ₄ may be provided. For example, a current collector or an exterior body may be attached to one or both of the outer side of the positive electrode member and the outer side of the negative electrode member.
The battery member typically includes a positive electrode member, a negative electrode member, and a solid electrolyte member disposed between the positive electrode member and the negative electrode member, and the outer side of the positive electrode member and the negative electrode member. It is an aggregate | assembly which has the arrangement | sequence structure in which the part which consists of another material is not joined to any of the outward side of.

  The method for producing the battery member is not particularly limited. For example, the negative electrode raw material powder is placed in a compression cylinder for powder compression molding and deposited to a uniform thickness to form a negative electrode raw material powder layer. Then, on the anode raw material powder layer, the solid electrolyte powder and the raw material powder for producing the solid electrolyte layer containing other components as required are deposited and deposited to a uniform thickness to form the raw material powder layer for producing the solid electrolyte layer Then, a positive electrode raw material powder containing a positive electrode active material containing Li is placed on the raw material powder layer for producing the solid electrolyte layer and deposited to a uniform thickness to form a positive electrode raw material powder layer. The battery member may be manufactured by compressing and molding a powder deposited body having three powder deposited layers formed at the same time.

Moreover, you may produce a solid electrolyte member, a negative electrode member, and a positive electrode member by methods other than powder compression molding. The specific method is as described above in this specification. For example, the solid electrolyte member may be formed by a cast film forming method using a solution or dispersion of a raw material for producing a solid electrolyte layer containing a solid electrolyte, or a coating method using a die coater. The negative electrode member and the positive electrode member are formed by, for example, forming a coating film by applying a negative electrode raw material or a positive electrode raw material dispersion containing a removable binder onto the solid electrolyte member, and then heating the coating film. A method of removing the binder from the film, or a negative electrode raw material or a positive electrode raw material powder containing a removable binder is compression-molded to form a positive electrode member or a negative electrode member, and then the molded body is heated. Alternatively, it may be formed by a method of removing the binder from the coating film. About a negative electrode member and a positive electrode member, in order to raise an electrode density, you may perform densification press previously before compression molding.
Moreover, you may form a negative electrode member and a positive electrode member on support bodies other than a solid electrolyte member. In that case, the negative electrode member and the positive electrode member are peeled from the support, and the peeled negative electrode member or positive electrode member is bonded onto the solid electrolyte member.

3-2. The energization process which supplies with electricity to a battery member The manufacturing method of this indication has the process of energizing in the direction which reaches the negative electrode member side via a solid electrolyte member from the positive electrode member side. That is, by energization, an electrochemical alloying reaction in which Li ions in the positive electrode active material are inserted into the Si simple substance in the negative electrode member through the solid electrolyte member proceeds, and the negative electrode member becomes Si as the negative electrode active material. By forming a negative electrode containing an alloy of Li and Li, an all-solid-state lithium ion secondary battery can be obtained.
The method for energizing the battery member is not particularly limited, but the current density is 0.001 to 10 mA / cm ² in order to efficiently proceed the electrochemical alloying reaction as shown in the above formula (1). The voltage may be in the range, or the voltage may be in the range of 0.01 to 0.1 V (vs Li / Li ⁺ ).

3-3. Manufacturing method of all-solid-state lithium ion secondary battery provided with restraint tool When manufacturing an all-solid-state lithium ion secondary battery provided with a restraint tool capable of applying a restraining pressure in the arrangement direction of the positive electrode, the solid electrolyte layer, and the negative electrode Further includes applying a first pressure to pressure-bond the negative electrode member and the solid electrolyte member in a state where at least the negative electrode member and the solid electrolyte member are overlapped, A step of adjusting to a second pressure lower than the first pressure may be included.
By forming a strong interface between the negative electrode member and the solid electrolyte member in advance by applying a relatively high first pressure and crimping the negative electrode member and the solid electrolyte member, the second pressure is relatively low. Even when the all solid lithium ion secondary battery is constrained, the capacity retention rate of the obtained all solid lithium ion secondary battery can be kept high.
Since the strong negative electrode member and solid electrolyte member interface can be formed, the first pressure may be 100 MPa or more, or 200 MPa or more.

The step of adjusting the restraining pressure of the restraining tool to the second pressure lower than the first pressure may be before the energizing step of energizing the battery member or after the energizing step. Since the influence of the volume change when Si as a negative electrode active material raw material becomes an alloy of Si and Li as the negative electrode active material can be reduced, the effect on the interface between the negative electrode member and the solid electrolyte member can be reduced. It may be before the process.
Since the restraint can be reduced in size, the second pressure may be 7 MPa or less.

4). All-solid lithium ion secondary battery There is no particular limitation on the configuration of the all-solid lithium ion secondary battery produced from the negative electrode raw material and the negative electrode member of the present disclosure as long as it functions as a secondary battery. A positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode are provided, and a positive electrode-solid electrolyte layer-negative electrode assembly is configured. In the positive electrode-solid electrolyte layer-negative electrode assembly, the positive electrode, the solid electrolyte, and the negative electrode may be arranged in this order, and may be joined directly or via a portion made of another material. Further, the solid electrolyte on the positive electrode One or both of the side opposite to the position where the layer is present (the outer side of the positive electrode) and the side opposite to the position where the solid electrolyte layer is present on the negative electrode (the outer side of the negative electrode) It is the aggregate | assembly of each part which has the arrangement | sequence structure which the part which consists of another material may join.
By attaching another member such as a current collector to the positive electrode-solid electrolyte layer-negative electrode assembly, a cell which is a functional unit of an all-solid battery is obtained, and the cell is used as an all-solid lithium ion battery as it is. It may be used, or may be used as an all-solid-state lithium ion battery of the present disclosure as a cell aggregate by integrating and electrically connecting a plurality of cells.
The thickness of each of the positive electrode and the negative electrode of the positive electrode-solid electrolyte layer-negative electrode assembly is usually about 0.1 μm to 10 mm, and the thickness of the solid electrolyte is usually about 0.01 μm to 1 mm.
The all-solid-state lithium ion secondary battery may include a restraining tool. It is possible to further increase the capacity maintenance rate by restraining the all-solid-state lithium ion secondary battery by the second pressure using the restraint, but the battery becomes larger if the restraint is provided. The presence / absence and size of the restraint may be determined according to the performance.

4-1. Negative electrode The negative electrode manufactured from the negative electrode member of the present disclosure includes an alloy of Si and Li as a negative electrode active material.
When the battery member is energized as described above, in the negative electrode member, the insertion reaction of Li ions with respect to the Si simple substance shown in the above formula (1) proceeds, and the negative electrode includes a negative electrode containing an alloy of Si and Li as a negative electrode active material. It becomes an all-solid-state lithium ion secondary battery.

Since the porous Si simple substance having a density of 1.5 g / cm ³ or less is used as the negative electrode active material raw material, the negative electrode active material, which is a SiLi alloy, is included in the negative electrode active material in a discharge state with a small amount of Li insertion. There are pores derived from the raw material.
In the charging reaction in which Li ions are inserted into the negative electrode active material that is a SiLi alloy, volume change of the negative electrode accompanying charging can be reduced by inducing volume expansion into the pores of the negative electrode active material.
Further, in the discharge reaction in which Li ions, which are SiLi alloys, are released, the pores corresponding to the volume of the released Li are recovered in the negative electrode active material, so that the volume change of the negative electrode accompanying discharge can be reduced.
Thus, in the negative electrode raw material of the present disclosure and the negative electrode manufactured from the negative electrode member, there is little volume change due to charging and discharging, and damage to the interface between the negative electrode and the solid electrolyte layer is suppressed. In an all-solid-state lithium ion secondary battery including a negative electrode manufactured from a negative electrode member, the capacity retention rate can be kept high even at a low restraint pressure.

  The alloy of Si and Li contained as the negative electrode active material may have a closed pore in which He gas is included.

  Although there is no particular limitation on the method for determining whether the alloy of Si and Li has closed pores in which He gas is included, STEM-EELS (Scanning Transmission Electron Microscopic Energy Loss Spectroscopy as well as Si simple substance) ) Can be judged by observation.

  There is no restriction | limiting in particular also in the shape of the said SiLi alloy, For example, the shape of a particle form, a film | membrane form, etc. are mentioned. Since the SiLi alloy that is the negative electrode active material can function as the negative electrode even if there is no component other than the alloy, it may have a film shape.

  In addition to the negative electrode active material, the negative electrode may contain other components such as a binder, a conductive material, and a solid electrolyte, which are included in the negative electrode member, as necessary. Other components such as the binder, the conductive material, and the solid electrolyte are the same as the materials used in the negative electrode member.

  Since the energy density increases as the amount of components other than the negative electrode active material decreases, the negative electrode may include only the negative electrode active material, or the negative electrode active material includes only an alloy of Si and Li. It may be.

4-2. Positive electrode The positive electrode is not particularly limited as long as it functions as a positive electrode of an all-solid-state lithium ion secondary battery, but usually contains a positive electrode active material containing Li, and if necessary, a binder, a solid electrolyte And other components such as a conductive material.
The positive electrode active material, the binder, the conductive material, and the solid electrolyte are the same as the materials used for the positive electrode member.

4-3. Solid Electrolyte Layer The solid electrolyte layer is not particularly limited as long as it functions as a solid electrolyte layer of an all-solid lithium secondary battery, but usually includes a solid electrolyte and, if necessary, includes other components.
The solid electrolyte and other components are the same as the materials used for the solid electrolyte member.

4-4. Restraint The negative electrode raw material of the present disclosure and the all-solid-state lithium ion secondary battery manufactured from the negative electrode member may include a restraint tool as necessary in the arrangement direction of the positive electrode, the solid electrolyte layer, and the negative electrode. Although there is no restriction | limiting in particular if it can apply | coat, The restraint tool which can apply a uniform restraint pressure to the arrangement direction of a positive electrode, a solid electrolyte layer, and a negative electrode by bolting normally is used.

(Synthesis of solid electrolyte)
Li ₂ S and P ₂ S ₅ were used as starting materials. These powders were mixed in a glove box under an argon atmosphere so as to have a stoichiometric composition (4: 1 molar ratio) to obtain a raw material composition. Next, 1 g of the raw material composition was placed in a zirconia pot (45 ml) together with zirconia balls (5 mmφ, 80 pieces), and the pot was completely sealed (argon atmosphere). This pot was attached to a planetary ball mill (trade name: P7, manufactured by Fritsch Japan Co., Ltd.), and mechanical milling was performed at a base plate rotation speed of 500 rpm for 20 hours. Thus, to obtain a powder of _Li 8 _P 2 _{S 9} as a solid electrolyte.

(Preparation of cell for cycle characteristic evaluation)
[Example 1]
Using a RF / DC magnetron sputtering apparatus (trade name: SPAD-2240UM, manufactured by AOV Co., Ltd.), a He gas as a discharge gas is formed on the surface of a stainless steel plate, which is a current collector, using a film of Si as a negative electrode material. A negative electrode member of Example 1 was obtained by film formation by the sputtering method used. In Example 1, since the negative electrode material does not contain any components other than the negative electrode active material, the negative electrode active material is the negative electrode material.
A counter electrode material (LiIn foil) was prepared by attaching Li foil (manufactured by Honjo Chemical Co., Ltd.) to In foil (manufactured by Niraco, φ10 mm, thickness 0.1 mm).
150 mg of the solid electrolyte powder was added to a cylinder made by Macor and pressed at 340 MPa (3.5 ton / cm ² ) to obtain a solid electrolyte member.
A LiIn foil was placed on one surface of the solid electrolyte member and pressed at 100 MPa (5 ton / cm ² ).
The negative electrode member of Example 1 was arrange | positioned on the other surface of the said solid electrolyte member, and LiIn foil-solid electrolyte member-negative electrode composite material assembly was obtained.
A restraint was placed on the LiIn foil-solid electrolyte member-negative electrode member assembly obtained in this way, and a restraint pressure of 7 MPa was applied in the arrangement direction of the LiIn foil, solid electrolyte member, and negative electrode member, and 0. Electricity was supplied at a constant current of 1 mA / cm ² until the voltage reached 2.5 V (vs Li / Li ⁺ ), and the cycle characteristic evaluation cell of Example 1 was obtained.
[Comparative Example 1]
In Example 1, a negative electrode member and a cycle characteristic evaluation cell of Comparative Example 1 were prepared in the same manner as in Example 1 except that the discharge gas was changed to Ar gas.

[Example 2]
In Example 1, except that a pressure of 100 MPa was applied in a state where the negative electrode member of Example 2 was disposed on the surface of the solid electrolyte member, the negative electrode mixture and cycle characteristic evaluation of Example 2 were performed in the same manner as in Example 1. A cell was prepared.

[Comparative Example 2-4]
In Example 2, the negative electrode member and the cycle characteristic evaluation cell of Comparative Example 2-4 were prepared in the same manner as in Example 2 except that the sputtering conditions such as the discharge gas species were changed as shown in Table 4.

[Reference Example 1]
In Example 2, except that a restraint was installed on the LiIn foil-solid electrolyte member-negative electrode member assembly, and a high restraint pressure of 100 MPa was applied in the arrangement direction of the LiIn foil, solid electrolyte member, and negative electrode member. Similarly to Example 2, the negative electrode member of Reference Example 1 and a cell for evaluating cycle characteristics were prepared.

[Reference Comparative Example 1-3]
In Comparative Example 2-4, a restraint was installed on the LiIn foil-solid electrolyte member-negative electrode member assembly, and a high restraint pressure of 100 MPa was applied in the arrangement direction of the LiIn foil, solid electrolyte member, and negative electrode member. Similarly to Comparative Example 2-4, the negative electrode composite material and cycle characteristic evaluation cell of Reference Comparative Example 1-3 were prepared.

(Evaluation method)
1. STEM-EELS Observation STEM-EELS observation on a single Si film, which is a negative electrode active material formed in Examples and Comparative Examples, was performed under the conditions described in Table 1 below using an atomic resolution analytical electron microscope (trade name: JEM-ARM200F). (HR), manufactured by JEOL Ltd.).

2. Measurement of capacity retention rate Charging / discharging with a constant current of 0.1 mA / cm ² and a voltage range of 2.5 V to 0.01 (vs Li / Li ⁺ ) using a cell for cycle characteristic evaluation The cycle was performed with 100 cycles as a target (when the capacity retention rate was low, the charge / discharge cycle was completed before reaching 100 cycles). The capacity retention rate at the maximum cycle number was calculated by dividing the discharge capacity at the maximum cycle number from 1 by the maximum discharge capacity confirmed during the maximum cycle.

(result)
A method for confirming the presence or absence of closed pores containing He gas from the STEM-EELS observation results will be described with reference to FIGS.
FIG. 1 is an SEM image of a cross section of a single Si film formed in Example 1. As shown in the SEM image of FIG. 1, pores were confirmed in the entire Si single film formed in Example 1.
As a result of STEM-EELS observation on the pores in the range shown in FIG. 1 under the conditions shown in Table 1, the EELS spectrum shown in FIG. 2 was obtained. In the EELS spectrum of FIG. 2, an energy loss peak was confirmed in the vicinity of 22 eV indicating the presence of He gas.
From the above results, since the He gas is considered to be contained in the pores during the deposition of the Si simple film by the sputtering method, there is He gas in the pores in the range selected in FIG. Therefore, it can be determined that the pore is a closed pore.
Next, STEM-EELS observation was performed on the entire photograph of FIG. 1 and the background was removed from the obtained EELS spectrum, and then the EELS intensity was integrated. FIG. 3 shows an image of a cross section of the Si simple film of Example 1 in which image processing is performed such that the higher the obtained EELS intensity integrated value (that is, the higher the He gas concentration), the whiter the image processing is.
As shown in FIG. 3, it was confirmed that closed pores containing He gas were distributed throughout.
With respect to the Si simple substance film other than Example 1, the presence or absence of closed pores containing He gas was confirmed by the same method.

  First, the capacity of the cell for evaluating cycle characteristics of Reference Example 1 and Reference Comparative Examples 1 to 3 in which the solid electrolyte member and the negative electrode member were pressure-bonded at 100 MPa as a reference, and a constraint pressure of 100 MPa was applied to the evaluation cell itself. Table 2 shows the measurement results of the maintenance rate.

As shown in Table 2, the negative electrode member of Reference Comparative Example 3 contained as a negative electrode active material raw material, and a simple Si film formed using Ar gas as a discharge gas has a film density of 2.3 g / cm ³ . No pores were confirmed by SEM observation, and closed pores containing He gas were not confirmed by STEM-EELS observation, which is considered to be almost solid. The capacity of the 100th cycle of Reference Comparative Example 3 using a solid Si film as a negative electrode active material material under the condition that the solid electrolyte member and the negative electrode member are pressure-bonded at 100 MPa and a high restraint pressure of 100 MPa is applied. The maintenance rate was 70%.
Moreover, the film | membrane of the single-piece | unit Si formed into a film by the sputtering method using the discharge gas containing He gas which the negative electrode member of Reference Example 1, Reference Comparative Example 1, and Reference Comparative Example 2 contains as a negative electrode active material raw material is The film density was 1.4 to 2.2 g / cm ³ , pores were confirmed by SEM observation, and closed pores containing He gas were confirmed by STEM-EELS observation. Reference Example 1 in which the solid electrolyte member and the negative electrode member were pressure-bonded at 100 MPa and a film of a simple substance of Si having pores was used as a negative electrode active material raw material under the conditions of applying a high pressure of 100 MPa as described above. In Reference Comparative Example 1 and Reference Comparative Example 2, the capacity retention rate at the 100th cycle was 91% or more.

  Next, Table 3 shows the measurement results of the capacity retention ratios of the cells for evaluating the cycle characteristics of Example 1 and Comparative Example 1 that were manufactured without pressure bonding the solid electrolyte member and the negative electrode member and the constraint pressure was as low as 7 MPa. . FIG. 4 is a graph showing the relationship between the cycle number and capacity in the cycle characteristic evaluation cell of Example 1, and FIG. 6 is a graph showing the relationship between the cycle number and capacity in the cycle characteristic evaluation cell of Comparative Example 1. It was shown to.

The film of the simple substance of Si, which is formed by using the Ar gas as the discharge gas, contained in the negative electrode member of Comparative Example 1 as the negative electrode active material raw material has a film density of 2.3 g / cm ³ , and no pores are confirmed by SEM observation. In addition, since closed pores containing He gas were not confirmed in STEM-EELS observation, it is considered to be almost solid as in Reference Comparative Example 3.
In the cycle characteristic evaluation cell of Comparative Example 1 manufactured from the negative electrode member of Comparative Example 1 containing a solid Si film as a negative electrode active material, the capacity retention rate at the 15th cycle was 25%. The charge / discharge cycle of 15 cycles or more could not be carried out.
Even when a solid Si single film is used as the negative electrode active material, the solid electrolyte member and the negative electrode member are pressure-bonded at 100 MPa as in Reference Comparative Example 3, and the evaluation cell itself is as high as 100 MPa. Although a relatively high capacity retention rate can be maintained by applying the restraining pressure, the cell for evaluating cycle characteristics of Comparative Example 1 does not press the solid electrolyte member and the negative electrode member, and the restraining pressure is 7 MPa. Therefore, it was considered that peeling occurred at the interface between the solid electrolyte and the negative electrode due to the volume change of the negative electrode itself.

On the other hand, the film of the Si simple substance formed by sputtering using He gas, which is contained in the negative electrode member of Example 1 as a negative electrode active material material, has a film density of 1.5 g / cm ³ . As described above, pores were confirmed by SEM observation, and closed pores containing He gas were confirmed by STEM-EELS observation.
Thus, in the cell for evaluating cycle characteristics of Example 1 manufactured from the negative electrode member of Example 1 containing a film of Si alone having pores as a negative electrode active material material, the capacity retention rate at the time of 50 cycles was 59%. Compared with the cell for evaluating cycle characteristics of Comparative Example 1, it was extremely high.
Since a simple Si film having pores was used as a negative electrode active material, volume change of the obtained negative electrode was suppressed, and the solid electrolyte member and the negative electrode member were not pressure-bonded, and the restraint pressure was as low as 7 MPa. It is thought that the high capacity maintenance rate was shown.

  Subsequently, the solid electrolyte member and the negative electrode composite material are pressure-bonded and manufactured, and the measurement results of the capacity retention rate of the cell for evaluating cycle characteristics of Example 2 and Comparative Examples 2 to 4 having a low restraint pressure of 7 MPa are shown. Table 4 shows. FIG. 5 is a graph showing the relationship between the cycle number and capacity in the cycle characteristic evaluation cell of Example 2, and FIG. 5 is a graph showing the relationship between the cycle number and capacity in the cycle characteristic evaluation cell of Comparative Examples 2 to 4. It was shown in FIGS.

The film of the simple substance of Si, which was formed using Ar gas as the discharge gas, contained in the negative electrode member of Comparative Example 4 as the negative electrode active material material, had a film density of 2.3 g / cm ³ , and pores were confirmed by SEM observation. In addition, since closed pores containing He gas were not confirmed in STEM-EELS observation, it is considered to be almost solid as in Comparative Example 1 and Reference Comparative Example 3.
For the cycle characteristic evaluation of Comparative Example 4 manufactured by press-bonding the solid electrolyte member and the negative electrode member at 100 MPa using the negative electrode member of Comparative Example 4 containing a solid Si simple substance film as the negative electrode active material material. In the cell, since the charge / discharge cycle could be performed up to 100 cycles, it can be evaluated that the cycle characteristics are superior to the cell for evaluating cycle characteristics of Comparative Example 1 manufactured without going through the crimping process. However, in the cell for evaluating cycle characteristics of Reference Comparative Example 3 in which the same negative electrode member was used and the solid electrolyte member and the negative electrode member were pressure-bonded at 100 MPa and a high restraint pressure of 100 MPa was applied to the evaluation cell itself, While the capacity retention rate at the 100th discharge cycle was 70%, the capacity retention rate at the 100th cycle was extremely low at 4% in the cycle characteristic evaluation cell of Comparative Example 4. It was thought that the capacity retention rate could not be maintained high if the solid elemental Si film was a negative electrode active material material and the restraint pressure of the evaluation cell itself was lowered.

The film of Si alone, which is formed by using the mixed gas of Ar and He as the discharge gas and contained in the negative electrode member of Comparative Example 3 as the negative electrode active material raw material, has a film density of 2.2 g / cm ^3. Since pores were confirmed, and closed pores containing He gas were also confirmed in STEM-EELS observation, it is considered to be porous.
A cell for evaluating cycle characteristics of Comparative Example 3 manufactured by press-bonding a solid electrolyte member and a negative electrode member using the negative electrode member of Comparative Example 3 containing a simple Si film having pores as a negative electrode active material material. However, the capacity retention rate at the 100th cycle was extremely low at 4%.
Further, the Si simple substance film formed using the mixed gas of Ar and He as the discharge gas, which is contained in the negative electrode member of Comparative Example 2 as the negative electrode active material raw material, has a film density of 2.1 g / cm ³ and is observed by SEM. Then, pores were confirmed, and closed pores containing He gas were also confirmed in STEM-EELS observation, so it is considered to be porous.
Thus, for the evaluation of cycle characteristics of Comparative Example 2 manufactured by press-bonding a solid electrolyte member and a negative electrode mixture using the negative electrode member of Comparative Example 2 containing a film of Si alone having pores as a negative electrode active material raw material Even in the cell, the capacity maintenance rate at the 100th cycle was as low as 12%.
Even when Si alone having pores is used as a negative electrode active material raw material, if the density is 2.1 g / cm ³ or more, there are too few pores, so that the volume change accompanying alloying can be sufficiently absorbed. Therefore, it became clear that the capacity retention rate could not be increased if the restraining pressure of the evaluation cell itself was lowered.

On the other hand, the film of the Si simple substance formed by sputtering using He gas as the discharge gas, which the negative electrode member of Example 2 contains as the negative electrode active material material, has a film density of 1.4 g / cm ³ . SEM observation confirmed pores, and STEM-EELS observation confirmed closed pores containing He gas.
Thus, the solid electrolyte member and the negative electrode member were pressure-bonded using the negative electrode member of Example 2 having a film density of 1.4 g / cm ³ and containing a porous Si simple substance film as a negative electrode active material material. In the cell for evaluation of cycle characteristics of Example 2, which is manufactured and has a low restraint pressure of 7 MPa, the capacity retention rate at the time of 100 cycles is 83%, compared with the cell for evaluation of cycle characteristics of Comparative Examples 2 to 4. It was extremely expensive.
When the density is 1.5 g / cm ³ or less, it is considered that the volume change accompanying alloying can be absorbed by the pores even if the restraining pressure is lowered to 7 MPa.
In addition, the cell for evaluating cycle characteristics of Example 2 manufactured by press-bonding the solid electrolyte member and the negative electrode member has a higher capacity retention rate than the cell for evaluating cycle characteristics of Example 1 manufactured without going through the pressing process. Indicated. By pressure bonding the negative electrode member and the solid electrolyte member, the negative electrode and the solid electrolyte are more strongly bonded, and even when the restraining pressure is as low as 7 MPa, the influence on the negative electrode volume change on the interface between the negative electrode and the solid electrolyte can be reduced. It is thought that it was because it was made.

In the results of Reference Example 1, Reference Comparative Example 1, and Reference Comparative Example 2 under the condition of high restraint pressure, the capacity retention rate is 91 to 91 when the film density is in the range of 1.4 to 2.2 g / cm ^3. There is no big difference with 96%. Therefore, there is almost no effect of maintaining the capacity in the range where the film density exceeds 1.5 g / cm ³ under low restraint pressure conditions, and the capacity is maintained extremely high by setting the range to 1.5 g / cm ³ or less. It is extremely difficult to predict that it will be possible.

From the above results, the negative electrode active material raw material having a density of 1.5 g / cm ³ or lower and containing Si alone having pores, and the negative electrode active material raw material having a density of 1.5 g / cm ³ or lower It has been clarified that an all-solid lithium ion secondary battery having good cycle characteristics with a low restraint pressure can be produced by a negative electrode member containing simple Si having pores.

Claims (7)

A negative electrode material for an all-solid-state lithium ion secondary battery, which contains Si as a negative electrode active material material having a density of 1.5 g / cm ³ or less and having pores.   2. The negative electrode material for an all-solid-state lithium ion secondary battery according to claim 1, wherein the Si simple substance having pores has closed pores containing He gas. A negative electrode member for an all-solid-state lithium ion secondary battery containing Si alone having pores having a density of 1.5 g / cm ³ or less as a negative electrode active material raw material.   The negative electrode member for an all-solid-state lithium ion secondary battery according to claim 3, wherein the Si simple substance having the pores has closed pores containing He gas. A method for producing an all solid lithium ion secondary battery comprising a negative electrode containing an alloy of Si and Li as a negative electrode active material,
Preparing a battery member comprising the negative electrode member according to claim 3 or 4, the positive electrode member, and a solid electrolyte member;
An energization step of energizing the battery member. A method for producing an all-solid-state lithium ion secondary battery. The all-solid-state lithium ion secondary battery further includes a restraining tool capable of applying a restraining pressure in the arrangement direction of the positive electrode, the solid electrolyte layer, and the negative electrode,
A step of applying a first pressure and crimping the negative electrode mixture and the solid electrolyte member in a state where at least the negative electrode member and the solid electrolyte member are stacked;
The method of manufacturing the all-solid-state lithium ion secondary battery of Claim 5 which has the process of adjusting the restraint pressure of the said restraint tool to 2nd pressure lower than 1st pressure.   The manufacturing method of the all-solid-state lithium ion secondary battery of Claim 6 whose said 2nd pressure is 7 Mpa or less.