JP6497282B2 - Negative electrode for all-solid-state battery - Google Patents

Description

  The present invention relates to a negative electrode for an all solid state battery.

  Metal ion secondary battery having a solid electrolyte layer using a flame retardant solid electrolyte (for example, a lithium ion secondary battery, etc. In the following, a lithium ion secondary battery having a solid electrolyte layer is referred to as an “all solid battery”. May have a merit that it is easy to simplify a system for ensuring safety.

  For example, Patent Document 1 discloses a current collector made of a copper foil base material, a roughening treatment layer having an uneven surface formed on the current collector, and a roughening treatment layer. A negative electrode for a lithium ion secondary battery comprising a negative electrode active material layer formed thereon, the negative electrode active material layer comprising Sn-C, which is amorphous carbon containing Sn, and Sn-C And a void ratio, which is a ratio occupied by voids in the negative electrode active material layer, in a cross-sectional view when cut in the plate thickness direction. A negative electrode for a lithium ion secondary battery is disclosed. Further, Patent Document 2 discloses an anode, a cathode, a solid electrolyte layer disposed between the anode and the cathode, and a configuration material of the anode and a solid electrolyte layer formed at an interface between the anode and the solid electrolyte layer. And at least one of a first mixing region containing a material and a second mixing region containing a constituent material of the cathode and a constituent material of the solid electrolyte layer formed at an interface between the cathode and the solid electrolyte layer. , An all-solid-state lithium ion secondary battery is disclosed. Claim 4 of Patent Document 2 discloses that the anode contains Sn, Si, or the like. Further, in claim 5, it is disclosed that the anode contains a composite material in which Sn, Si or the like is supported in the pores of the carbon porous body.

JP 2011-108362 A JP 2008-251225 A

  The lithium ion secondary batteries disclosed in Patent Documents 1 and 2 contain the capacity (charge capacity and discharge capacity of the all-solid-state battery) by containing Si or Sn in the carbon in the negative electrode active material. In addition, the discharge capacity is sometimes collectively referred to as “capacity”). However, if the carbon in the negative electrode active material contains only Si or Sn, the expansion and contraction of the negative electrode active material due to charge / discharge is suppressed, and the stress and strain on the solid electrolyte due to the expansion and contraction of the negative electrode active material. In addition, there is a problem that the solid electrolyte is cracked due to expansion and contraction of the negative electrode active material depending on the particle size of Si or Sn. That is, in the lithium ion secondary batteries disclosed in Patent Documents 1 and 2, it is difficult to achieve both a high capacity and an excellent capacity maintenance rate.

  Then, this invention makes it a subject to provide the negative electrode for all-solid-state batteries which can make a high cell volume energy density and the outstanding capacity maintenance rate compatible in all-solid-state batteries.

  As a result of intensive studies, the inventor has limited the particle size of Si or Sn to be contained in the negative electrode active material and the negative electrode active material containing the Si or Sn, and uses the negative electrode active material and the sulfide solid electrolyte. It was found that by limiting the porosity of the negative electrode, it was possible to obtain an all-solid-state battery having both a high cell volume energy density and an excellent capacity retention rate. The present invention has been completed based on this finding.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention is a negative electrode for an all-solid battery having a sulfide solid electrolyte and a negative electrode active material, wherein the negative electrode active material is a composite particle having a carbon material containing Si or Sn, and the particle diameter of Si or Sn Is 94 nm or less, the particle diameter of the negative electrode active material is 15 μm or less, and the negative electrode has a porosity of 5% to 30%.

Here, “the particle diameter of Si or Sn” means that, in a transmission electron microscope (TEM) image of the negative electrode active material, 10 particles are selected from the Si or Sn particles contained in the negative electrode active material. It is an average value calculated from the particle diameter of Si or Sn particles.
The “particle diameter of the negative electrode active material” is an average particle diameter (D ₅₀ ) of the negative electrode active material measured using a laser particle size distribution meter.
The “porosity” is the ratio of the volume of voids in the negative electrode to the entire negative electrode, obtained by dividing the porosity by A and the weight of each material contained in the negative electrode active material by the true density of each material. A value calculated by A (%) = (1−x / y) × 100, where x is the total volume obtained and y is the volume obtained from the actual negative electrode dimensions.

  The negative electrode for an all-solid battery according to the present invention can suppress local expansion and contraction of the negative electrode active material and cracking of the solid electrolyte caused by the expansion and contraction of the negative electrode active material. Thereby, the contact state of a negative electrode active material and a solid electrolyte can be made favorable.

  ADVANTAGE OF THE INVENTION According to this invention, the negative electrode for all-solid-state batteries which can obtain the all-solid-state battery which makes a high cell volume energy density and the outstanding capacity maintenance rate compatible can be provided.

It is a figure explaining the negative electrode 10 for all-solid-state batteries which concerns on one Embodiment of this invention. It is a figure explaining the all-solid-state battery 100 which concerns on one Embodiment of this invention. It is a figure explaining the relationship between a cell volume energy density and a capacity | capacitance maintenance factor, and the mass percentage of Si in a negative electrode active material. It is a figure explaining the relationship between a cell volume energy density and a capacity | capacitance maintenance factor, and the particle diameter of a negative electrode active material. It is a figure explaining the relationship between a cell volume energy density and a capacity | capacitance maintenance factor, and the particle diameter of Si. It is a figure explaining the relationship between a cell volume energy density and a capacity | capacitance maintenance factor, and a porosity.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

  FIG. 1 is a diagram illustrating an all-solid battery negative electrode 10 (hereinafter, also referred to as “negative electrode 10”) according to an embodiment of the present invention. The negative electrode 1 has at least a sulfide solid electrolyte 1, a negative electrode active material 2, and a void 3.

  The negative electrode active material 2 is a composite particle having a carbon material 5 containing fine particles 4. The particle diameter of the negative electrode active material 2 is 15 μm or less, and the particle diameter of the fine particles 4 is 94 nm or less. The void 3 is a gap surrounded by the adjacent sulfide solid electrolyte 1 and / or the negative electrode active material 2. The ratio (void ratio) of the void 3 in the negative electrode 10 is 5% to 30%.

  According to the negative electrode 10 according to the present invention, it is possible to suppress local expansion and contraction of the negative electrode active material and cracking of the solid electrolyte caused by the expansion and contraction of the negative electrode active material. Thereby, the contact state of a negative electrode active material and a solid electrolyte can be made favorable. That is, it is possible to provide an all-solid battery negative electrode capable of obtaining an all-solid battery having both a high cell volume energy density and an excellent capacity retention rate.

As the sulfide solid electrolyte 1, a sulfide solid electrolyte that can be used in an all-solid battery can be appropriately used. Examples of such sulfide solid electrolytes include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ S—P ₂ S ₅ , LiI—Li ₂ S—P ₂ O ₅ , LiI—. Examples include Li ₃ PO ₄ —P ₂ S ₅ , Li ₂ S—P ₂ S ₅ , Li ₃ PSi _{4, and the} like. The sulfide solid electrolyte may be crystalline, non-crystalline, or glass ceramic.

  The negative electrode active material 2 is a composite particle having a carbon material 5 containing fine particles 4. The particle diameter of the negative electrode active material 2 is 15 μm or less. When the particle diameter of the negative electrode active material is 15 μm or less, local expansion and contraction of the negative electrode active material 2 and cracking of the sulfide solid electrolyte 1 caused by the expansion and contraction of the negative electrode active material 2 can be suppressed. .

  The fine particles 4 are a metal containing Si or Sn, and may be a simple substance or an alloy. By including the fine particles 4 in the negative electrode active material 2, it is possible to improve the cell volume energy density of the all-solid-state battery.

  On the other hand, when a negative electrode active material containing Si or Sn is used, it reacts with more Li than a normally used negative electrode active material, so that the volume of the negative electrode active material expands to about 3 to 4 times. It has been. For this reason, the expanded negative electrode active material may compress the surrounding solid electrolyte, causing cracks in the solid electrolyte, which may break the Li ion conduction path. Furthermore, the negative electrode active material may also crack due to its own expansion. This causes the negative electrode active material to be pulverized and isolated, which may break the Li ion conduction path with the surroundings. That is, if the interface between the negative electrode active material and the solid electrolyte cannot be maintained, and the Li ion conduction path of the solid electrolyte phase cannot be maintained, charging / discharging cannot be performed, and there is a possibility that sufficient capacity cannot be taken out due to a significant capacity reduction.

  Therefore, the particle diameter of the fine particles 4 according to the present invention is set to 94 nm or less. When the particle diameter of the fine particles 4 is 94 nm or less, it is possible to achieve both a high cell volume energy density and an excellent capacity retention rate. On the other hand, when the particle diameter of the fine particles 4 exceeds 94 nm, local expansion and contraction of the negative electrode active material 2 and cracking of the sulfide solid electrolyte 1 caused by the expansion and contraction of the negative electrode active material 2 cannot be suppressed. The rate drops.

  The mass percentage of the fine particles 4 in the negative electrode active material 2 is preferably in the range of 20 wt% to 95 wt%. When the mass percentage of the fine particles 4 is in the range of 20 wt% to 95 wt%, it is possible to achieve both a high cell volume energy density and an excellent capacity maintenance rate. On the other hand, when the mass percentage of the fine particles 4 is less than 20 wt%, the cell volume energy density decreases. Further, if the mass percentage of the fine particles 4 exceeds 95 wt%, the cell volume energy density is improved, but the capacity retention ratio is lowered, so that a high cell volume energy density and an excellent capacity maintenance ratio cannot be achieved at the same time.

  The fine particles 4 may be contained in the carbon material 5, but it is particularly preferable that they are arranged in a dispersed manner. By disperse | distributing the microparticles | fine-particles 4 to the negative electrode active material 2, the crack of the solid electrolyte 1 which arises with the local expansion / contraction of the negative electrode active material 2 and the expansion / contraction of the negative electrode active material 2 can be suppressed. It becomes possible.

  Furthermore, the fine particles 4 may contain Fe, Co, Ni, Ti, Cr, B, and P in addition to Si or Sn.

  As the carbon material 5, a carbon material that can be used as a negative electrode active material of an all-solid battery can be appropriately used. Such a carbon material is not particularly limited as long as it contains at least carbon. Graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, soft carbon, carbon blacks (acetylene) Black, ketjen black, etc.).

  The void 3 is a gap surrounded by the adjacent sulfide solid electrolyte 1 and / or the negative electrode active material 2. The porosity of the negative electrode 10 is 5% to 30%. When the porosity is in the range of 5% to 30%, an expansion space when the negative electrode active material 2 and Li react can be secured in advance, and the sulfide solid electrolyte 1 around the negative electrode active material 2 can be pressed. Can be suppressed. As a result, in an all-solid-state battery, cracks in the solid electrolyte during the initial charge and subsequent charge / discharge and gaps formed between the solid electrolyte and the negative electrode active material can be suppressed, so that the Li ion conduction path is prevented from being cut. be able to. That is, since the contact between the negative electrode active material 2 and the surrounding sulfide solid electrolyte 1 is maintained, the Li ion conduction of the negative electrode 10 does not decrease, and as a result, a high cell volume energy density and an excellent capacity maintenance rate are achieved. It becomes possible to achieve both. On the other hand, when the porosity is less than 5%, damage to the negative electrode 10 increases when the negative electrode active material 2 expands, and thus the capacity retention rate decreases. On the other hand, when the porosity exceeds 30%, the contact between the sulfide solid electrolyte 1 and the negative electrode active material 2 becomes insufficient, and the cell volume energy density and the capacity retention rate are lowered.

  Moreover, the negative electrode 1 can contain a conductive material, a binder, etc. suitably as needed. Conductive materials include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), carbon nanofiber (CNF), and all-sulfide solids. A metal material that can withstand the environment when the battery is used can be exemplified. Examples of the binder include acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), and the like.

  Examples of the method for producing the negative electrode 10 include a method for producing a negative electrode using a slurry-like negative electrode composition prepared by dispersing the negative electrode active material or the like in a liquid. Examples of the liquid in which the negative electrode active material and the like are dispersed include heptane and the like, and a nonpolar solvent can be preferably used. Further, the thickness of the negative electrode is, for example, preferably from 0.1 μm to 1 mm, and more preferably from 1 μm to 100 μm. Moreover, in order to make it easy to improve the performance of the all-solid-state battery, the negative electrode is preferably manufactured through a pressing process. In this invention, the pressure at the time of pressing a negative electrode can be about 100 Mpa, for example.

  Here, although the all-solid-state battery 100 using the negative electrode 10 which concerns on this invention is demonstrated, this invention is not limited to the said form.

  As shown in FIG. 2, the all-solid battery 100 includes a negative electrode current collector 10a, a negative electrode 10 connected to the negative electrode current collector, a positive electrode current collector 20a, and a positive electrode 20 connected to the positive electrode current collector. And a solid electrolyte layer 30 disposed between the negative electrode and the positive electrode.

  The negative electrode current collector 10 a is a conductor connected to the negative electrode 10. A metal that can be used as a current collector for an all-solid battery can be used for the negative electrode current collector 10a. As such a metal, a metal containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Materials can be exemplified.

  The positive electrode current collector 20 a is a conductor connected to the positive electrode 20. As the positive electrode current collector 20a, a metal that can be used as a current collector of a solid state battery can be used. As such a metal, a metal containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Materials can be exemplified.

  The positive electrode 20 includes at least a positive electrode active material, and can contain a sulfide solid electrolyte, a conductive material, a binder, and the like as needed.

As the positive electrode active material to be contained in the positive electrode 20, a positive electrode active material that can be used in an all-solid battery can be appropriately used. Examples of such a positive electrode active material include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium nickel cobalt manganese composite oxide (LiNi _x Co _y Mn _(1-xy) O ₂ (however, In addition to layered active materials such as 0 <x <1, 0 <y <1, 0 <x + y <1)), olivine-type active materials such as olivine-type lithium iron phosphate (LiFePO ₄ ), and spinel-type lithium manganate Examples thereof include spinel active materials such as (LiMn ₂ O ₄ ) and NAC-based active materials such as nickel cobalt lithium aluminate (Li (Ni—Co—Al) O ₂ ). The shape of the positive electrode active material can be, for example, particulate or thin film. The average particle diameter (D ₅₀ ) of the positive electrode active material is, for example, preferably from 1 nm to 100 μm, and more preferably from 10 nm to 30 μm. Moreover, the content of the positive electrode active material in the positive electrode 20 is not particularly limited, but is preferably 40 wt% or more and 99 wt% or less in mass percentage, for example.

  Examples of the sulfide solid electrolyte that can be contained in the positive electrode 20 include the sulfide solid electrolyte that can be contained in the negative electrode. Moreover, as a binder which can be contained in a positive electrode, the said binder which can be contained in a negative electrode can be illustrated. Furthermore, examples of the conductive material that can be contained in the positive electrode include the conductive materials that can be contained in the negative electrode.

  When producing a positive electrode using a positive electrode active material, a sulfide solid electrolyte, and a slurry-like positive electrode composition prepared by dispersing a binder in a liquid, heptane or the like can be exemplified as a usable liquid. A nonpolar solvent can be preferably used. Further, the thickness of the positive electrode is, for example, preferably from 0.1 μm to 1 mm, and more preferably from 1 μm to 100 μm. Moreover, in order to make it easy to improve the performance of the all-solid-state battery, the positive electrode is preferably manufactured through a pressing process. In this invention, the pressure at the time of pressing a positive electrode can be about 100 MPa, for example.

  The solid electrolyte layer 30 is a layer containing at least a sulfide solid electrolyte, and can appropriately contain a binder in addition to the sulfide solid electrolyte. Examples of the sulfide solid electrolyte that can be contained in the solid electrolyte layer 30 include the sulfide solid electrolyte that can be contained in the positive electrode and the negative electrode. Examples of the binder that can be contained in the solid electrolyte layer 30 include the binder that can be contained in the negative electrode 10 and the positive electrode 20. However, in order to easily increase the output of the all-solid-state battery, excessive aggregation of the sulfide solid electrolyte is prevented, and the solid electrolyte layer 30 having the sulfide solid electrolyte dispersed uniformly can be formed. From the viewpoint, when the solid electrolyte layer 30 contains a binder, the content is preferably 5 wt% or less. Further, when a separate layer is produced through a process of applying a slurry-like sulfide solid electrolyte composition prepared by dispersing the sulfide solid electrolyte or the like in a liquid to a substrate such as the negative electrode 10 or the positive electrode 20, Examples of the liquid for dispersing the solid electrolyte and the like include heptane and the like, and a nonpolar solvent can be preferably used. The content of the sulfide solid electrolyte in the solid electrolyte layer 30 is a mass percentage, for example, 60 wt% or more, preferably 70 wt% or more, and particularly preferably 80 wt% or more. The thickness of the solid electrolyte layer 30 varies greatly depending on the configuration of the battery. For example, the thickness is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. In order to easily improve the performance of the all-solid-state battery 100, the solid electrolyte layer 30 is preferably manufactured through a pressing process. In this invention, the pressure at the time of pressing the solid electrolyte layer 30 can be about 100 Mpa, for example.

  The present invention will be further described with reference to examples.

  All-solid batteries according to Examples 1 to 20 and Comparative Examples 1 to 10 were produced as follows, and the cell volume energy density and the capacity retention rate were evaluated. The results are shown in Tables 1-4. Moreover, what graphed each of Tables 1-4 was shown in FIGS.

<Example 1>
(Synthesis of sulfide solid electrolyte)
LiS ₂ (true density 1.66 g / cm ³ , manufactured by Nippon Chemical Industry Co., Ltd.) and P ₂ S ₅ (true density 2.1 m ³ , manufactured by Aldrich) were used as starting materials. 0.7656 g of LiS ₂ and 1.2344 g of P ₂ S ₅ were weighed and mixed in an agate mortar for 5 minutes, and then 4 g of heptane (manufactured by Kanto Chemical Co., Inc.) was put into a planetary ball mill (P7 manufactured by Fritsch). The same was performed for 40 minutes to obtain a sulfide solid electrolyte.

(Preparation of negative electrode mixture)
Si powder (true density 2.33 g / cm ³ ) and carbon material (true density 2.0 g / cm ³ ) were weighed so as to have a mass ratio of 20:80. The obtained Si powder and carbon material were put into a planetary ball mill and mechanical alloying was performed at 270 rpm for 24 hours. Then, coarse particles were removed by passing through a sieve having an opening of 20 μm to obtain a negative electrode active material. The particle size (D ₅₀ ) of this negative electrode active material was measured using a laser particle size distribution meter (manufactured by Horiba, Ltd.). Moreover, the particle diameter of Si contained in the negative electrode active material was calculated using TEM (manufactured by JEOL). Next, 5.05 mg of the obtained negative electrode active material and 5.14 mg of sulfide solid electrolyte were mixed to prepare a negative electrode mixture.

(Preparation of positive electrode mixture)
LiNi _3/5 Co _1/5 Mn _1/5 O ₂ subjected to surface treatment of LiNbO ₃ was used as the positive electrode active material. By mixing 12.03 g of this positive electrode active material, 0.51 mg of vapor-grown carbon fiber (VGCF) (manufactured by Showa Denko KK) which is conductive carbon, and 5.14 mg of a sulfide solid electrolyte, An agent was prepared.

(Production of all-solid battery)
A solid electrolyte layer was prepared by weighing 18 mg of a sulfide solid electrolyte into a 1 cm ² ceramic mold and pressing it at 0.98 MPa. A positive electrode was prepared by putting 15.7 mg of the positive electrode mixture on one side of the solid electrolyte layer and pressing it at 4.5 MPa. A negative electrode mixture with a porosity of 20% was prepared by placing 5.14 mg of a negative electrode mixture on the side opposite to the side on which the positive electrode of the solid electrolyte layer was prepared, and pressing the mixture at 4.5 MPa. Then, an aluminum foil as a positive electrode current collector was disposed on the surface of the positive electrode, and a copper foil as a negative electrode current collector was disposed on the surface of the negative electrode, whereby an all-solid battery according to Example 1 was produced.

<Example 2>
The all-solid-state battery according to Example 2 is the same as Example 1 except that the mass ratio of Si powder and carbon material is set to Si powder: carbon material = 30: 70 when the negative electrode mixture is produced. Was made.

<Example 3>
The all solid state battery according to Example 3 in the same manner as in Example 1 except that the mass ratio of Si powder and carbon material was set to Si powder: carbon material = 50: 50 when the negative electrode mixture was produced. Was made.

<Example 4>
The all-solid-state battery according to Example 4 is the same as Example 1 except that the mass ratio of Si powder to carbon material is set to Si powder: carbon material = 70: 30 when the negative electrode mixture is produced. Was made.

<Example 5>
The all-solid-state battery according to Example 5 is the same as Example 1 except that the mass ratio of Si powder and carbon material is Si powder: carbon material = 95: 5 when the negative electrode mixture is produced. Was made.

<Example 6>
An all-solid-state battery according to Example 6 was produced in the same manner as in Example 3 except that the negative electrode active material had a particle diameter of 1 μm when the negative electrode mixture was produced.

<Example 7>
An all-solid-state battery according to Example 7 was produced in the same manner as in Example 3 except that the negative electrode active material had a particle diameter of 6 μm when the negative electrode mixture was produced.

<Example 8>
An all solid state battery according to Example 8 was prepared in the same manner as in Example 3 except that the negative electrode active material had a particle diameter of 8 μm when the negative electrode mixture was prepared.

<Example 9>
An all-solid battery according to Example 9 was produced in the same manner as in Example 3 except that the negative electrode active material had a particle diameter of 10 μm when the negative electrode mixture was produced.

<Example 10>
An all-solid battery according to Example 10 was produced in the same manner as in Example 3 except that the negative electrode active material had a particle diameter of 15 μm when the negative electrode mixture was produced.

<Example 11>
An all-solid-state battery according to Example 11 was produced in the same manner as in Example 3 except that the particle size of Si was changed to 5 nm when producing the negative electrode mixture.

<Example 12>
An all-solid-state battery according to Example 12 was produced in the same manner as in Example 3, except that the particle diameter of Si was changed to 10 nm when producing the negative electrode mixture.

<Example 13>
An all-solid-state battery according to Example 13 was produced in the same manner as Example 3 except that the particle size of Si was changed to 27 nm when producing the negative electrode mixture.

<Example 14>
An all-solid battery according to Example 14 was produced in the same manner as in Example 3 except that the particle diameter of Si was changed to 76 nm when producing the negative electrode mixture.

<Example 15>
An all-solid-state battery according to Example 15 was produced in the same manner as in Example 3 except that the particle size of Si was set to 94 nm when producing the negative electrode mixture.

<Example 16>
An all solid state battery according to Example 16 was produced in the same manner as in Example 3 except that the negative electrode had a porosity of 5% when the negative electrode was produced.

<Example 17>
An all solid state battery according to Example 17 was produced in the same manner as Example 3 except that the porosity of the negative electrode was changed to 9% when the negative electrode was produced.

<Example 18>
An all-solid-state battery according to Example 18 was produced in the same manner as in Example 3 except that the negative electrode had a porosity of 17% when the negative electrode was produced.

<Example 19>
An all-solid-state battery according to Example 19 was produced in the same manner as in Example 3 except that the negative electrode had a porosity of 25% when the negative electrode was produced.

<Example 20>
An all solid state battery according to Example 20 was produced in the same manner as Example 3 except that the porosity of the negative electrode was changed to 30% when producing the negative electrode.

<Comparative Example 1>
The all-solid-state battery according to Comparative Example 1 is the same as Example 1 except that the mass ratio of Si powder to carbon material is set to Si powder: carbon material = 0: 100 when producing the negative electrode mixture. Was made. The particle diameter of the negative electrode active material according to Comparative Example 1 was 10 μm.

<Comparative example 2>
The all-solid-state battery according to Comparative Example 2 is the same as Example 1 except that the mass ratio of Si powder to carbon material is set to Si powder: carbon material = 10: 90 when the negative electrode mixture is produced. Was made.

<Comparative Example 3>
The all-solid-state battery according to Comparative Example 3 is the same as Example 1 except that the mass ratio of Si powder and carbon material is Si powder: carbon material = 98: 2 when the negative electrode mixture is prepared. Was made.

<Comparative example 4>
The all-solid-state battery according to Comparative Example 4 is the same as Example 1 except that the mass ratio of Si powder to carbon material is set to Si powder: carbon material = 100: 0 when the negative electrode mixture is produced. Was made.

<Comparative Example 5>
An all-solid battery according to Comparative Example 5 was produced in the same manner as in Example 3 except that the negative electrode active material had a particle size of 20 μm when the negative electrode mixture was produced.

<Comparative Example 6>
An all-solid battery according to Comparative Example 6 was produced in the same manner as in Example 3 except that the negative electrode active material had a particle diameter of 128 nm when the negative electrode mixture was produced.

<Comparative Example 7>
An all-solid-state battery according to Comparative Example 7 was prepared in the same manner as in Example 3 except that the particle size of Si was 231 nm when the negative electrode mixture was prepared.

<Comparative Example 8>
An all-solid-state battery according to Comparative Example 8 was produced in the same manner as in Example 3 except that the porosity of the negative electrode was changed to 3% when producing the negative electrode.

<Comparative Example 9>
An all-solid battery according to Comparative Example 9 was prepared in the same manner as in Example 3 except that the negative electrode had a porosity of 35% when the negative electrode was prepared.

<Comparative Example 10>
An all-solid-state battery according to Comparative Example 10 was produced in the same manner as in Example 3 except that the negative electrode had a porosity of 38% when the negative electrode was produced.

  Next, the cell volume energy density and the capacity retention rate were evaluated for all solid state batteries according to Examples 1 to 20 and Comparative Examples 1 to 10.

(Evaluation of cell volume energy density)
The cell volume energy density was calculated from the following formula.
(Cell volume energy density) = (initial discharge capacity) × (initial discharge voltage) ÷ (negative electrode volume)
In addition, in Tables 1-4 and FIGS. 3-6, the cell volume energy density of the comparative example 1 is set to 100, and each cell volume energy density is represented as a relative value.

(Evaluation of capacity maintenance rate)
Charging / discharging was performed by the following method, and the capacity retention rate was calculated using the discharge capacity at the 701st cycle as the numerator and the discharge capacity at the first cycle as the denominator.
First cycle: After constant voltage constant current (CC / CV) charge to 4.4 V at 0.25 mA, constant voltage constant current (CC / CV) discharge was performed to 3.0 V at 0.25 mA.
-2 to 700 cycles: After constant voltage constant current (CC / CV) charging to 4.4 V at 1.5 mA, constant voltage constant current (CC / CV) discharging was performed to 3.0 V at 0.25 mA.
-701st cycle: After constant voltage constant current (CC / CV) charge to 4.4V at 0.35 mA, constant voltage constant current (CC / CV) discharge was performed to 3.0V at 0.25 mA.

  Table 1 is a table for explaining the relationship between the cell volume energy density and the capacity retention ratio and the mass percentage of Si in the negative electrode active material, and summarizes the results of Examples 1 to 5 and Comparative Examples 1 to 4. Moreover, the relationship between the cell volume energy density and capacity retention ratio shown in Table 1 and the mass percentage of Si in the negative electrode active material is shown in FIG. The vertical axis in FIG. 3 is the cell volume energy density and the capacity retention rate, and the horizontal axis is the mass percentage (wt%) of Si in the negative electrode active material.

  As shown in Table 1, the cell volume energy density of the all solid state batteries according to Examples 1 to 5 was in the range of 103 to 135, and was higher than the cell volume energy density of the all solid state battery according to Comparative Example 1. In particular, the cell volume energy density of the all solid state battery according to Example 5 was 135, which was a very high value. Moreover, the capacity maintenance rate of the all-solid-state battery which concerns on Examples 1-5 was in the range of 75%-85%, and was excellent. That is, it was found that an all solid state battery having a mass percentage of Si in the negative electrode active material in the range of 20 wt% to 95 wt% achieves both a high cell volume energy density and an excellent capacity retention rate. On the other hand, the cell volume energy density of the all solid state battery according to Comparative Example 2 in which the mass percentage of Si in the negative electrode active material is 10 wt% was lower than the cell volume energy density of the all solid state battery according to Comparative Example 1. . Further, in the all solid state batteries according to Comparative Examples 3 and 4 in which the mass percentage of Si in the negative electrode active material exceeded 98 wt%, the cell volume energy density showed a very high value, but the capacity retention rate was 46%, The value was as low as 30%. That is, the all-solid-state batteries according to Comparative Examples 1 to 4 could not achieve both a high cell volume energy density and an excellent capacity maintenance rate.

  Table 2 is a table for explaining the relationship between the cell volume energy density and capacity retention rate and the particle size of the negative electrode active material, and summarizes the results of Examples 3, 6 to 10, and Comparative Example 5. Moreover, the relationship between the cell volume energy density and capacity retention ratio shown in Table 2 and the particle diameter of the negative electrode active material is shown in FIG. The vertical axis in FIG. 4 is the cell volume energy density and capacity retention rate, and the horizontal axis is the particle diameter (μm) of the negative electrode active material.

  As shown in Table 2, the cell volume energy density of the all solid state batteries according to Examples 3 and 6 to 10 is in the range of 113 to 116, which is higher than the cell volume energy density of the all solid state battery according to Comparative Example 1. It was. Moreover, the capacity maintenance rate of the all-solid-state battery which concerns on Example 3, 6-10 was in the range of 70%-84%, and was excellent. That is, it was found that an all solid state battery having a negative electrode active material particle size in the range of 1 μm to 25 μm achieves both a high cell volume energy density and an excellent capacity retention rate. In contrast, the all-solid battery according to Comparative Example 5 in which the particle size of the negative electrode active material was 20 μm had a cell volume energy density equivalent to that of the all-solid battery according to Examples 9 and 10, but the capacity The maintenance rate was as low as 32%. That is, the all-solid-state battery according to Comparative Example 5 could not achieve both a high cell volume energy density and an excellent capacity retention rate.

  Table 3 is a table for explaining the relationship between the cell volume energy density and capacity retention rate, and the particle diameter of Si, and summarizes the results of Examples 3, 11-15, and Comparative Examples 6-7. The relationship between the cell volume energy density and capacity retention rate shown in Table 3 and the Si particle diameter is shown in FIG. The vertical axis in FIG. 5 is the cell volume energy density and the capacity retention rate, and the horizontal axis is the particle diameter (nm) of Si contained in the negative electrode active material.

  As shown in Table 3, the cell volume energy density of the all solid state batteries according to Examples 3, 11 to 15 is in the range of 115 to 118, which is higher than the cell volume energy density of the all solid state battery according to Comparative Example 1. It was. Moreover, the capacity maintenance rate of the all-solid-state battery which concerns on Example 3, 11-15 was in the range of 75%-85%, and was excellent. That is, it was found that the all-solid-state battery having a Si particle size in the range of 5 nm to 94 nm achieves both a high cell volume energy density and an excellent capacity retention rate. In contrast, the all solid state batteries according to Comparative Examples 6 and 7 having Si particle sizes of 128 nm and 231 nm, respectively, showed a higher cell volume energy density than that of Comparative Example 1, but the capacity retention ratio was 45 respectively. % And 21%. That is, in the all solid state batteries according to Comparative Examples 6 and 7, a high cell volume energy density and an excellent capacity maintenance rate were not compatible.

  Table 4 is a table for explaining the relationship between the cell volume energy density and capacity retention rate and the porosity, and summarizes the results of Examples 3, 16 to 20 and Comparative Examples 8 to 10. Moreover, the relationship between the cell volume energy density and capacity retention rate shown in Table 4 and the porosity is shown in FIG. The vertical axis in FIG. 6 is the cell volume energy density and the capacity retention rate, and the horizontal axis is the porosity (%).

  As shown in Table 4, the cell volume energy density of the all solid state batteries according to Examples 3 and 16 to 20 is in the range of 113 to 118, which is higher than the cell volume energy density of the all solid state battery according to Comparative Example 1. It was. Moreover, the capacity maintenance rate of the all-solid-state battery which concerns on Example 3, 16-20 was in the range of 69%-84%, and was excellent. That is, it was found that an all solid state battery having a porosity in the range of 5% to 30% achieves both a high cell volume energy density and an excellent capacity retention rate. In contrast, the all solid state battery according to Comparative Example 9 had a cell volume energy density higher than that of the all solid state battery according to Comparative Example 1, but the capacity retention rate was a low value of 42%. . Moreover, the all-solid-state battery which concerns on the comparative example 10 was a low value in both cell volume energy density and a capacity | capacitance maintenance factor. That is, in the all solid state batteries according to Comparative Examples 9 and 10, a high cell volume energy density and an excellent capacity maintenance rate were not compatible.

DESCRIPTION OF SYMBOLS 1 Sulfide solid electrolyte 2 Negative electrode active material 3 Cavity 4 Fine particle 5 Carbon material 10 Negative electrode 10a Negative electrode collector 20 Positive electrode 20a Positive electrode collector 30 Solid electrolyte layer 100 All-solid-state battery

Claims (1)

A negative electrode for an all-solid battery having a sulfide solid electrolyte and a negative electrode active material,
The negative electrode active material is a composite particle having a carbon material containing Si ,
The particle diameter of the Si is 94 nm or less, and the particle diameter of the negative electrode active material is 15 μm or less;
Wherein Ri anode porosity of 5% to 30% der,
The mass percentage of Si in the negative electrode active material is 20 wt% to 95 wt%.
Negative electrode for all solid state batteries.

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