JP2016081905A - Solid electrolyte layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte layer capable of suppressing the generation of a short circuit during charging.SOLUTION: The present invention provides a solid electrolyte layer used for an all-solid lithium battery. The solid electrolyte layer contains: a sulfide solid electrolyte material; and an inorganic solid material represented by MO(where, M represents a metal element, and x and y each represent an arbitrary number). In the solid electrolyte layer, the inorganic solid material is a secondary particle formed by the aggregation of primary particles, 66≤A/B≤208 is satisfied where A and B represent an average particle size of primary particles of the sulfide solid electrolyte material and an average particle size of the primary particles of the inorganic solid material, respectively, 2.4≤C/B≤4.6 is satisfied where C represents an average particle size of the secondary particles of the inorganic solid material, and the content of the inorganic solid material is within a range of 0.1-1.0 wt.%.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a solid electrolyte layer capable of suppressing the occurrence of a short circuit during charging.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been regarded as important. Also in the automobile industry and the like, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is being promoted. Currently, lithium batteries are attracting attention among various batteries from the viewpoint of high energy density.

  Since lithium batteries currently on the market use an electrolyte solution containing a flammable organic solvent, a safety device for preventing a temperature rise at the time of a short circuit and a structure for preventing a short circuit are required. In contrast, a lithium battery in which the electrolyte is changed to a solid electrolyte layer to make the battery completely solid does not use a flammable organic solvent in the battery, so the safety device can be simplified, and manufacturing costs and productivity can be reduced. It is considered excellent.

  Patent Document 1 includes a solid electrolyte layer containing first solid electrolyte particles and second solid electrolyte particles, and the average particle size C of the second solid electrolyte particles is the average particle size of the first solid electrolyte particles. An all solid state battery smaller than B is disclosed. Furthermore, the particle size ratio of the first solid electrolyte particles and the second solid electrolyte particles and the respective contents thereof are disclosed. Further, this technique is a technique for obtaining a solid electrolyte layer having a low ion conduction resistance and a high filling rate.

In Patent Document 2, a raw material composition containing an amorphous sulfide solid electrolyte material and an oxide (for example, SiO ₂ ) is heated, and the amorphous sulfide solid electrolyte material is crystallized. A sulfide solid electrolyte material having an oxide content of 40% by mass or less is disclosed. Furthermore, the range of 10 mass%-40 mass% is disclosed as content of an oxide. In addition, this technique is a technique in which an oxide is added to an amorphous sulfide solid electrolyte material, followed by crystallization, thereby producing an amorphous-like crystal and improving ion conductivity.

JP 2013-157084 A JP 2012-022801 A

  In Patent Document 1, when the solid electrolyte layer is thinned and the filling rate of the solid electrolyte layer is low, the conductive material contained in the electrode active material layer is mixed into the solid electrolyte layer, and a short circuit is likely to occur. Is described. Furthermore, in order to suppress the occurrence of a short circuit, it is described that the filling rate is improved by using finely divided solid electrolyte particles. Note that Patent Document 1 assumes a short circuit when a battery is manufactured.

  On the other hand, during charging, dendritic Li (Li dendrite) may be deposited on the negative electrode side. When Li dendrite grows, penetrates the solid electrolyte layer and contacts the positive electrode, a short circuit occurs. Here, as described in Patent Document 1, it is possible to suppress Li dendrite from penetrating the solid electrolyte layer to some extent by using fine solid electrolyte particles and improving the filling rate. There is sex. However, since the Li dendrite grows in accordance with the three-dimensional shape of the through hole of the solid electrolyte layer, it is necessary to remove the through hole of the solid electrolyte layer in order to suppress a short circuit due to the Li dendrite. Therefore, it is difficult to suppress a short circuit due to Li dendrite simply by improving the filling rate.

  This invention is made | formed in view of the said situation, and it aims at providing the solid electrolyte layer which can suppress generation | occurrence | production of the short circuit at the time of charge.

  In order to solve the above problems, as a result of intensive studies by the present inventors, by adding a small amount of oxide (inorganic solid material) sufficiently smaller than the sulfide solid electrolyte material to the solid electrolyte layer, It discovered that the short circuit by Li dendrite could be suppressed. In this way, the present invention has been completed.

That is, in the present invention, a solid electrolyte layer used in an all-solid lithium battery, which is a sulfide solid electrolyte material and M _x O _y (M is a metal element, and x and y are arbitrary numbers). The inorganic solid material is a secondary particle in which primary particles are aggregated, the average particle diameter of primary particles of the sulfide solid electrolyte material, and the inorganic solid material When the average particle size of the primary particles is A and B, respectively, 66 ≦ A / B ≦ 208 is satisfied, and when the average particle size of the secondary particles of the inorganic solid material is C, 2 The solid electrolyte layer satisfying .4 ≦ C / B ≦ 4.6 and the content of the inorganic solid material is in the range of 0.1 wt% to 1.0 wt%.

  According to the present invention, the average particle size (average particle size of primary particles) of the sulfide solid electrolyte material and the inorganic solid material has a specific relationship, and the average particle size of the primary particles and secondary particles in the inorganic solid material is specified. Furthermore, it can be set as the solid electrolyte layer which suppressed generation | occurrence | production of the short circuit at the time of charge because content of an inorganic solid material exists in a specific range.

  The solid electrolyte layer of the present invention has an effect of suppressing the occurrence of a short circuit during charging.

It is a schematic sectional drawing which shows an example of the all-solid-state lithium battery of this invention. It is a schematic sectional drawing which shows the other example of the all-solid-state lithium battery of this invention. It is a schematic sectional drawing which shows the other example of the all-solid-state lithium battery of this invention. It is the result of the charging / discharging measurement with respect to the battery for evaluation obtained in Examples 1-3 and the comparative example 1. FIG. It is the result of the charging / discharging measurement with respect to the battery for evaluation obtained by Comparative Examples 2-7.

  Hereinafter, the solid electrolyte layer and the all solid lithium battery of the present invention will be described in detail.

A. Solid Electrolyte Layer The solid electrolyte layer of the present invention is a solid electrolyte layer used for an all-solid lithium battery, which is a sulfide solid electrolyte material, M _x O _y (M is a metal element, x and y are arbitrary The inorganic solid material is a secondary particle in which primary particles are aggregated, the average particle diameter of the primary particles of the sulfide solid electrolyte material, and the above When the average particle size of the primary particles of the inorganic solid material is A and B, respectively, 66 ≦ A / B ≦ 208 is satisfied, and the average particle size of the secondary particles of the inorganic solid material is C. In this case, 2.4 ≦ C / B ≦ 4.6 is satisfied, and the content of the inorganic solid material is in the range of 0.1 wt% to 1.0 wt%.

  According to the present invention, the average particle size (average particle size of primary particles) of the sulfide solid electrolyte material and the inorganic solid material has a specific relationship, and the average particle size of the primary particles and secondary particles in the inorganic solid material is specified. Furthermore, it can be set as the solid electrolyte layer which suppressed generation | occurrence | production of the short circuit at the time of charge because content of an inorganic solid material exists in a specific range.

  Here, since the sulfide solid electrolyte material has sulfur, it is a material that is easily plastically deformed. Further, when the solid electrolyte layer is formed, the sulfide solid electrolyte material particles (electrolyte particles) are plastically deformed by pressing in the thickness direction. When the solid electrolyte layer does not contain an inorganic solid material as in the past, it is considered that the fluidity of the electrolyte particles in the solid electrolyte layer forming material is low, and the arrangement of the electrolyte particles is also non-uniform. Therefore, it is considered that the press pressure is not uniformly transmitted, and voids (particularly through holes) are likely to remain in the solid electrolyte layer after pressing.

  On the other hand, in the present invention, it has been found that the filling rate of the solid electrolyte layer is improved by slightly adding inorganic solid material particles (inorganic solid particles) sufficiently smaller than the sulfide solid electrolyte material. It was. This is presumably because the addition of inorganic solid particles improved the fluidity of the electrolyte particles during mixing of the mixture. Specifically, when mixing materials, small particles (inorganic solid particles) are attracted around large particles (electrolyte particles), and small particles are placed between large particles to suppress aggregation of large particles. As a result, it is considered that the fluidity of large particles is improved. Therefore, the part which electrolyte particle aggregates reduces, and it can suppress that a space | gap (especially through-hole) arises because a press pressure is transmitted uniformly.

  In addition, in order to suppress a short circuit due to Li dendrite, the relationship between hardness of electrolyte particles that are easily plastically deformed and inorganic solid particles that are difficult to be plastically deformed is also important. That is, it is important to combine electrolyte particles and inorganic solid particles harder than the electrolyte particles. The hardness can be determined by, for example, Vickers hardness.

  In the present invention, when a press pressure is applied, force is applied to the hard inorganic solid particles dispersed in the solid electrolyte layer. The force applied to each inorganic solid particle is transmitted to the electrolyte particles inside the solid electrolyte layer, and the soft electrolyte particles are plastically deformed starting from the inorganic solid particles. As a result, the electrolyte particles are easily plastically deformed, and the generation of voids can be suppressed. The sulfide solid electrolyte material has elasticity. By using a hard inorganic solid material, it is thought that the crack resulting from the elastic change of the sulfide solid electrolyte material by the pressurization and pressure reduction at the time of shaping | molding can be suppressed.

Patent Document 1 includes a solid electrolyte layer containing first solid electrolyte particles and second solid electrolyte particles, and the average particle size C of the second solid electrolyte particles is the average of the first solid electrolyte particles. An all solid state battery smaller than the particle size B is disclosed. However, both the first solid electrolyte particles and the second solid electrolyte particles are materials that are easily plastically deformed. In this case, as described in Comparative Examples 6 and 7, which will be described later, the filling rate may be improved, but the occurrence of a short circuit during charging cannot be suppressed. That is, it is difficult to suppress a short circuit due to Li dendrite simply by improving the filling rate. Patent Document 1 is different in concept from the present invention in consideration of the fluidity and hardness of particles. On the other hand, Patent Document 2 discloses a range of 10% by mass to 40% by mass as the content of oxides, but does not describe or suggest the slight addition of oxides. In Patent Document 2, an oxide is added in order to obtain an amorphous-like crystal, and the idea is different from that of the present invention considering the fluidity and hardness of particles.
Hereinafter, the solid electrolyte layer of the present invention will be described in more detail.

1. Sulfide solid electrolyte material The sulfide solid electrolyte material in the present invention usually has a sulfur element as an anion element. Examples of the sulfide solid electrolyte material include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₅ —LiI, Li ₂ S—P ₂ S ₅ —LiCl, and Li ₂ S—P ₂ S ₅ —. _{LiBr, Li 2 S-P 2} S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2, Li 2 S-SiS 2 -LiI, Li 2 S- _{SiS 2 -LiBr, Li 2 S-} SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3 _{, Li 2 S-P 2 S} 5 -Z m S n ( however, m, n is the number of positive .Z is, Ge, Zn, one of _{Ga.), Li 2 S-} GeS 2, Li 2 S- _{SiS 2 -Li 3 PO 4, Li} 2 S-SiS 2 -Li x MO (However, x, y is a positive number .M is, P, Si, Ge, B , Al, Ga, either an _In.), May be mentioned Li ₁₀ GeP _{2 S 12} or the like. The sulfide solid electrolyte material may be amorphous, crystalline, or glass ceramic.

The sulfide solid electrolyte material preferably has an ionic conductor having Li element, P element and S element. The ionic conductor is usually composed of a Li cation and an anionic structure containing P and S. Among them, the ion conductor preferably contains a _PS ^{4 3-} structure mainly anionic structures (more than 50 mol%). Among them, the proportion of _PS ^{4 3-} structure, the total anion structure of the ion conductor is preferably at least 70 mol%, more preferably at least 90 mol%. Note that the ratio of the PS ₄ ^3- structure can be determined by Raman spectroscopy, NMR, XPS, or the like.

  The sulfide solid electrolyte material preferably has the above ionic conductor as a main component. The ratio of the ionic conductor in the sulfide solid electrolyte material is preferably 65 mol% or more, and more preferably 75 mol% or more. Moreover, the sulfide solid electrolyte material may be comprised only from the said ion conductor, and may contain the other component. Examples of other components include LiI.

The ratio of LiI is, for example, 5 mol% or more, and preferably 20 mol% or more. On the other hand, the ratio of LiI is, for example, 35 mol% or less, and preferably 30 mol% or less. In particular, the sulfide solid electrolyte material has a composition of xLiI · (100−x) (yLi ₂ S · (1-y) P ₂ S ₅ ) (20 ≦ x ≦ 30, 0.7 ≦ y ≦ 0.8). It is preferable to have. In addition, it is preferable that y is 0.72 or more, and it is more preferable that it is 0.74 or more. Moreover, y is preferably 0.78 or less, and more preferably 0.76 or less.

The sulfide solid electrolyte material preferably has high Li ion conductivity, and the Li ion conductivity at room temperature (25 ° C.) is preferably 1 × 10 ⁻⁴ S / cm or more, for example, 1 × 10 ^−3. More preferably, it is S / cm or more.

2. Inorganic Solid Material The inorganic solid material in the present invention is an oxide represented by M _x O _y (M is a metal element, and x and y are arbitrary numbers). Therefore, the material is harder than the sulfide solid electrolyte material. The inorganic solid material is preferably an insulating material. This is because the reaction with the sulfide solid electrolyte material can be suppressed. Examples of M include at least one of Si, Al, and Ti. M may be one kind or two or more kinds. X and _y in M _x O _y are not particularly limited as long as they are values that can provide oxides that can exist in nature. Usually, from the viewpoint of electrical neutrality, the value of y is determined corresponding to the valence of M and the value of x. Examples of the inorganic solid material include at least one of SiO ₂ , Al ₂ O ₃ , and TiO ₂ . The inorganic solid material is preferably a material that does not function as an active material. It is because it can suppress that it reacts with sulfide solid electrolyte material and a sulfide solid electrolyte material deteriorates.

3. Solid electrolyte layer The solid electrolyte layer of the present invention contains a sulfide solid electrolyte material and an inorganic solid material. These materials are preferably dispersed uniformly. Here, the inorganic solid material in the present invention is secondary particles in which primary particles are aggregated. On the other hand, the sulfide solid electrolyte material in the present invention is an aggregate in which primary particles are aggregated. In the sulfide solid electrolyte material, primary particles are agglomerated, but it is difficult to strictly determine whether or not it has a shape as a particle (whether it corresponds to a secondary particle). Expressed as an aggregate. The average particle size of the primary particles of the sulfide solid electrolyte material, the average particle size of the primary particles of the inorganic solid material, and the average particle size of the secondary particles of the inorganic solid material are A, B, and C, respectively. The average particle diameter refers to the D ₅₀ in the particle size distribution. The particle size distribution is an index indicating what size (particle size) particles are contained in what proportion (relative distribution amount with 100% as a whole). Commercially available materials usually have only one distribution peak. Further, for example, the particle size distribution of particles whose particle size is adjusted by pulverization with a ball mill or the like generally follows a normal distribution, and there is only one distribution amount peak. The average particle diameter can be determined, for example, by observation with an SEM and a particle size distribution measuring device.

  The average particle diameter A of the primary particles of the sulfide solid electrolyte material is larger than the average particle diameter B of the primary particles of the inorganic solid material. The value of A / B is usually 66 or more, preferably 70 or more, and more preferably 100 or more. On the other hand, the value of A / B is usually 208 or less, and preferably 180 or less. The average particle diameter A of the primary particles of the sulfide solid electrolyte material is not particularly limited, but is, for example, in the range of 0.01 μm to 10 μm, and preferably in the range of 0.05 μm to 2 μm. . In addition, the average particle diameter of the aggregate of the primary particles is, for example, in the range of 0.5 μm to 30 μm, and preferably in the range of 1 μm to 20 μm. On the other hand, the average particle diameter B of the primary particles of the inorganic solid material is not particularly limited, but is, for example, 1 nm or more and preferably 5 nm or more. On the other hand, the average particle diameter B is, for example, 100 nm or less, preferably 50 nm or less, and more preferably 20 nm or less.

  The average particle size C of the secondary particles of the inorganic solid material is larger than the average particle size B of the primary particles of the inorganic solid material. The value of C / B is usually 2.4 or more and preferably 2.5 or more. On the other hand, the value of C / B is usually 4.6 or less and preferably 4.5 or less. The average particle size C of the secondary particles of the inorganic solid material is, for example, 3 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. On the other hand, the average particle diameter C is, for example, 150 nm or less, preferably 100 nm or less, and more preferably 60 nm or less.

  The content of the inorganic solid material contained in the solid electrolyte layer is usually 0.1% by weight or more, and preferably 0.3% by weight or more. On the other hand, the content of the inorganic solid material is usually 1.0% by weight or less, and preferably 0.8% by weight or less. Further, the total content of the sulfide solid electrolyte material and the inorganic solid material contained in the solid electrolyte layer is, for example, preferably 80% by weight or more, more preferably 90% by weight or more, and 95% by weight or more. More preferably.

  The solid electrolyte layer of the present invention may contain only a sulfide solid electrolyte material and an inorganic solid material, or may contain other materials. Examples of the other material include a binder. Examples of the binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF).

The filling rate of the solid electrolyte layer is preferably higher. Specifically, it is preferably 95% or more, more preferably 96% or more, and further preferably 97% or more. The Li ion conductivity of the solid electrolyte layer is preferably higher, and the Li ion conductivity at room temperature (25 ° C.) is preferably 1 × 10 ⁻⁴ S / cm or more, for example, 1 × 10 ⁻³ S. / Cm or more is more preferable.

  The thickness of the solid electrolyte layer is, for example, 1000 μm or less, preferably 500 μm or less, and more preferably 300 μm or less. On the other hand, the thickness of the solid electrolyte layer is, for example, 1 μm or more, and preferably 10 μm or more. In addition, the thickness of a solid electrolyte layer means the average thickness of a solid electrolyte layer.

In this invention, the manufacturing method of the solid electrolyte layer mentioned above can also be provided. That is, a method for producing a solid electrolyte layer used for an all-solid lithium battery, represented by a sulfide solid electrolyte material and M _x O _y (M is a metal element, and x and y are arbitrary numbers). And pressing the electrolyte mixture containing the inorganic solid material, wherein the inorganic solid material is a secondary particle in which the primary particles are aggregated, and the average particle size of the primary particles of the sulfide solid electrolyte material When the average particle size and the average particle size of the primary particles of the inorganic solid material are A and B, respectively, 66 ≦ A / B ≦ 208 is satisfied, and the average particle size of the secondary particles of the inorganic solid material When the diameter is C, 2.4 ≦ C / B ≦ 4.6 is satisfied, and the content of the inorganic solid material is in the range of 0.1 wt% to 1.0 wt%. It is also possible to provide a method for producing a solid electrolyte layer that is characterized .

B. All-solid-state lithium battery The all-solid-state lithium battery of the present invention includes the above-described solid electrolyte layer.

  According to this invention, it can be set as the all-solid-state lithium battery which suppressed generation | occurrence | production of the short circuit at the time of charge by providing the above-mentioned solid electrolyte layer. Although the all-solid-state lithium battery of this invention will not be specifically limited if it is provided with the solid electrolyte layer mentioned above, It is preferable that it is in any one of the 1st embodiment-3rd embodiment mentioned later.

1. First Embodiment The all solid lithium battery of the first embodiment is a general battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer. Specifically, a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer are provided. It is a solid electrolyte layer described in “Solid electrolyte layer”.

  FIG. 1 is a schematic cross-sectional view showing an example of the all solid lithium battery of the first embodiment. 1 includes a positive electrode active material layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3 formed between the positive electrode active material layer 1 and the negative electrode active material layer 2, and a positive electrode active material. It has a positive electrode current collector 4 that collects current from the layer 1, a negative electrode current collector 5 that collects current from the negative electrode active material layer 2, and a battery case 6 that houses these members.

(1) Positive electrode active material layer The positive electrode active material layer in the first embodiment is a layer containing at least a positive electrode active material. The positive electrode active material layer may contain at least one of a conductive material, a binder, and a solid electrolyte material in addition to the positive electrode active material.

Examples of the positive electrode active material include an oxide active material. As the oxide active material, specifically, rock salt layer type active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ And spinel type active materials such as Li (Ni _0.5 Mn _1.5 ) O ₄ , and olivine type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCuPO ₄ . It is _also possible to use a _{Li 2 FeSiO 4, Li 2 MnSiO} 4 as a positive electrode active material.

The surface of the positive electrode active material may be coated with a coat layer. This is because the reaction between the positive electrode active material and the sulfide solid electrolyte material can be suppressed. Examples of the material for the coat layer include Li ion conductive oxides such as LiNbO ₃ , Li ₃ PO ₄ , and LiPON. For example, the average thickness of the coat layer is preferably in the range of 1 nm to 20 nm, and more preferably in the range of 1 nm to 10 nm.

  Examples of the conductive material include carbon materials such as acetylene black, ketjen black, VGCF, and graphite. Examples of the binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF). Examples of the solid electrolyte material include a sulfide solid electrolyte material and an oxide solid electrolyte material. The thickness of the positive electrode active material layer varies greatly depending on the configuration of the battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.

(2) Negative electrode active material layer The negative electrode active material layer in the first embodiment is a layer containing at least a negative electrode active material. The negative electrode active material layer may contain at least one of a conductive material, a binder, and a solid electrolyte material in addition to the negative electrode active material.

  Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. The content of the negative electrode active material is preferably higher from the viewpoint of capacity, for example, preferably in the range of 60 wt% to 99 wt%, and more preferably in the range of 70 wt% to 95 wt%.

  The conductive material, the binder, and the solid electrolyte material are the same as described above. The thickness of the negative electrode active material layer varies greatly depending on the configuration of the battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.

(3) Solid Electrolyte Layer The solid electrolyte layer in the first embodiment is the same as the contents described in the above “A. Solid electrolyte layer”, so description thereof is omitted here.

(4) Other configurations The all-solid-state lithium battery of the first embodiment usually has a positive electrode current collector that collects current from the positive electrode active material layer and a negative electrode current collector that collects current from the negative electrode active material layer. . Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Moreover, the battery case of a general battery can be used for a battery case. Examples of the battery case include a SUS battery case.

(5) All-solid-state lithium battery The all-solid-state lithium battery of the first embodiment may have a charge control unit that controls the current density during charging. Current density at the time of charging, but is not particularly limited as long as the current density does not occur short circuit is for example 0.026mA / cm ² or more, preferably 0.26 mA / cm ² or more, 1 more preferably .3mA / cm ² or more, further preferably 2.6 mA / cm ² or more. On the other hand, the current density at the time of charge, for example, 52 mA / cm ² or less, is preferably 10.4 mA / cm ² or less, and more preferably 5.2 mA / cm ² or less.

  The all solid lithium battery of the first embodiment may be provided with a restraining pressure in the thickness direction by a restraining member. The kind of restraint member is not specifically limited, A general restraint member can be used. The restraining pressure (surface pressure) is not particularly limited, but is, for example, 0.1 MPa or more, and preferably 1 MPa or more. By increasing the restraint pressure, there is an advantage that it is easy to maintain contact between particles such as contact between active material particles and electrolyte particles. On the other hand, the restraint pressure (surface pressure) is, for example, 100 MPa or less, and preferably 50 MPa or less. This is because if the restraint pressure is too large, the restraint member is required to have high rigidity, and the restraint member may be increased in size.

  The all solid lithium battery of the first embodiment is not particularly limited as long as it has the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Further, the all solid lithium battery may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. The primary battery includes primary battery use (use for the purpose of discharging only once after charging). In addition, examples of the shape of the all solid lithium battery include a coin type, a laminate type, a cylindrical type, and a square type.

  In the first embodiment, the above-described method for producing an all-solid lithium battery can also be provided. That is, the manufacturing method of the all-solid-state lithium battery characterized by having the solid electrolyte layer formation process which forms the solid electrolyte layer mentioned above can also be provided.

2. Second Embodiment The all-solid lithium battery of the second embodiment is a battery in which a negative electrode active material layer is not provided at the time of assembly, and Li metal as a negative electrode active material is deposited by subsequent charging. Specifically, a negative electrode current collector, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector are provided in this order, the solid electrolyte layer is provided on the surface of the negative electrode current collector, and the solid electrolyte layer is provided. Is an all-solid-state lithium battery characterized in that it is the solid electrolyte layer described in “A. Solid electrolyte layer” above.

  FIG. 2 is a schematic cross-sectional view showing an example of the all solid lithium battery of the second embodiment. The all solid lithium battery 10 in FIG. 2 includes a negative electrode current collector 5, a solid electrolyte layer 3, a positive electrode active material layer 1, and a positive electrode current collector 4 in this order. The solid electrolyte layer 3 is disposed on the surface of the negative electrode current collector 5, and both are in contact with each other.

  The all-solid-state lithium battery in which the negative electrode active material layer is not provided at the time of assembly and Li metal as a negative electrode active material is deposited by the subsequent charging is higher than the all-solid-state lithium battery in which the negative electrode active material layer is provided at the time of assembly. There is a peculiar problem that short-circuiting due to is likely to occur remarkably. When an all-solid lithium battery provided with a negative electrode active material layer is charged during assembly, Li is inserted into the negative electrode active material (for example, carbon), so usually Li deposition occurs immediately on the surface of the negative electrode active material. Absent. On the other hand, when the negative electrode active material layer is not provided at the time of assembly, Li deposition occurs on the surface of the negative electrode current collector at the time of charging, so that a short circuit due to Li dendrite is likely to occur.

  Thus, although the all-solid-state lithium battery of the second embodiment is structurally easily short-circuited, the occurrence of a short-circuit can be effectively suppressed by using the above-described solid electrolyte layer. The configuration of the all-solid lithium battery of the second embodiment is basically the same as the configuration of the all-solid lithium battery of the first embodiment except that the negative electrode active material layer is not provided during assembly.

  In the second embodiment, the material of the negative electrode current collector is preferably a material that does not alloy with Li. Specific examples include SUS, copper, nickel, and carbon. Examples of the form of the negative electrode current collector include a foil shape, a plate shape, a mesh shape, and a porous shape. Moreover, the battery case may have the function of a negative electrode current collector. Although the thickness of a negative electrode collector is not specifically limited, For example, it exists in the range of 1 micrometer-50 micrometers, and it is preferable that it exists in the range of 5 micrometers-20 micrometers.

  In the second embodiment, it is preferable that the sulfide solid electrolyte material contained in the solid electrolyte layer does not contain a metal element such as Ge or Si. This is because the reduction resistance is high and it is difficult to react with Li.

3. Third Embodiment The all solid lithium battery of the third embodiment is a battery obtained by charging the all solid lithium battery of the second embodiment. A negative electrode current collector, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector are provided in this order, and a negative electrode active material layer that is Li metal deposited on the surface of the negative electrode current collector on the solid electrolyte layer side is provided. The all-solid-state lithium battery is characterized in that the solid electrolyte layer is the solid electrolyte layer described in "A. Solid electrolyte layer" above.

  FIG. 3 is a schematic cross-sectional view showing an example of the all solid lithium battery of the third embodiment. The all solid lithium battery 10 in FIG. 3 includes a negative electrode current collector 5, a solid electrolyte layer 3, a positive electrode active material layer 1, and a positive electrode current collector 4 in this order. Furthermore, the negative electrode active material layer 2 which is Li metal deposited on the solid electrolyte layer 3 side of the negative electrode current collector 5 is provided. The configuration of the all-solid lithium battery of the third embodiment is basically the same as the configuration of the all-solid lithium battery of the second embodiment except that it includes a negative electrode active material layer that is deposited Li metal.

  The fact that Li metal is deposited on the surface of the negative electrode current collector can be confirmed by observing the interface between the two. For example, a field emission scanning electron microscope (FE-SEM) can be used for observation of the interface. For example, when Li metal is arranged in advance by vapor deposition, the Li metal exists uniformly in a dense state. For example, when Li metal foil is previously arranged, if an appropriate pressing force is applied, Li metal exists uniformly in a dense state. On the other hand, when Li metal is deposited, Li metal exists relatively following the electrolyte in a slightly sparse state. Moreover, the surface of the deposited Li metal may be fibrous (about 100 nm in diameter).

  The thickness of the Li metal deposited on the surface of the negative electrode current collector also varies depending on the state of charge. The maximum thickness of the Li metal is, for example, 50 μm or less, preferably 30 μm or less, and more preferably 20 μm or less. Note that the maximum thickness of the Li metal can be calculated as an average thickness in a state in which charging is most advanced.

  In the third embodiment, Li metal that precipitates during charging is used as the negative electrode active material. Therefore, the amount of Li in the entire battery usually matches the amount of Li in the positive electrode active material layer and the solid electrolyte layer. Further, when an electrochemical redox decomposition reaction or the like does not occur in the solid electrolyte layer, the amount of Li in the solid electrolyte layer is constant, so that the amount of Li decreased from the positive electrode active material layer during charging and the negative electrode during charging This corresponds to the amount of Li deposited on the current collector. Further, in a state where the charging is completely advanced, the positive electrode active material may not contain Li.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
(Preparation of sulfide solid electrolyte material)
As starting materials, lithium sulfide (Li ₂ S, purity 99.9%, manufactured by Nippon Chemical Industry Co., Ltd.), diphosphorus pentasulfide (P ₂ S ₅ , purity 99%, manufactured by Aldrich), and lithium iodide (LiI) , Purity 99.9%, manufactured by Aldrich). Next, in a glove box under an Ar atmosphere (dew point −70 ° C.), Li ₂ S, P ₂ S ₅ and LiI are combined in a composition ratio of 20LiI · 80 (0.75Li ₂ S · 0.25P ₂ S ₅ ). Mixed. 2 g of this mixture is charged into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is charged, and ZrO ₂ balls (φ = 5 mm, 53 g) are charged. The container was completely sealed (Ar atmosphere). This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed 40 times with a base plate rotation speed of 500 rpm and a one-hour treatment and a 15-minute pause. Next, in order to remove heptane, drying was performed at 100 ° C. for 1 hour. Thereby, sulfide glass was obtained. Thereafter, the obtained sulfide glass was subjected to heat treatment under conditions of Ar atmosphere, 180 ° C., and 3 hours to crystallize the sulfide glass to obtain glass ceramics (sulfide solid electrolyte material).

(Production of electrolyte mixture)
The resulting sulfide solid electrolyte material was ground to adjust the average particle diameter D ₅₀ of the primary particles in the 2.5 [mu] m. This sulfide solid electrolyte material and an inorganic solid material (SiO ₂ , average primary particle size 12 nm, average secondary particle size 30 nm) are mixed with a weight of sulfide solid electrolyte material: inorganic solid material = 99.9: 0.1. Weighed by ratio. Next, dehydrated heptane was added as a dispersion medium and mixed with an ultrasonic homogenizer. Next, in order to remove heptane, drying was performed at 100 ° C. for 1 hour. This obtained the electrolyte compound material.

(Preparation of positive electrode mixture)
LiCoO ₂ (manufactured by Nippon Chemical Industry Co., Ltd., trade name cell seed, average particle size D ₅₀ = 10 μm) was prepared as a positive electrode active material. A coating layer (average thickness of 10 nm) composed of LiNbO ₃ was formed on the surface of this positive electrode active material using a tumbling fluidized coating apparatus (MP01, manufactured by POWREC).

The obtained positive electrode active material (LiCoO ₂ coated with LiNbO ₃ ), sulfide solid electrolyte material (20LiI · 80 (0.75Li ₂ S · 0.25P ₂ S ₅ ), glass ceramics, average particle size of primary particles D ₅₀ = 0.8 μm) was weighed at a weight ratio of positive electrode active material: sulfide solid electrolyte material = 93: 7. The average particle size of the primary particles of the sulfide solid electrolyte material was adjusted by pulverizing with a ball mill. Next, dehydrated heptane was added as a dispersion medium and mixed with an ultrasonic homogenizer. Next, in order to remove heptane, drying was performed at 100 ° C. for 1 hour. This obtained the positive electrode compound material.

(Production of evaluation battery)
A solid electrolyte layer was molded by putting 100 mg of the electrolyte mixture in a cylinder made of Macor and pressing it at 98 MPa. Next, 20.4 mg of the positive electrode mixture was put on one surface of the solid electrolyte layer, and the positive electrode active material layer was molded by pressing at 784 MPa. A battery for evaluation was obtained by sandwiching both surfaces of the obtained laminate with a SUS piston and tightening with three bolts (torque = 2 Nm, surface pressure = 15 MPa). Thereafter, the evaluation battery was sealed in a glass container (Ar atmosphere). In addition, all operations using the sulfide solid electrolyte material were performed in a glove box in a dry Ar atmosphere. Moreover, the battery for evaluation is a battery which does not provide a negative electrode active material layer at the time of assembly, but deposits Li metal as a negative electrode active material by subsequent charging. The thickness of the solid electrolyte layer was 480 μm.

[Example 2]
An evaluation battery was prepared in the same manner as in Example 1 except that the weight ratio of the sulfide solid electrolyte material and the inorganic solid material was changed to sulfide solid electrolyte material: inorganic solid material = 99.0: 1.0. Obtained.

[Example 3]
Except that the average particle diameter D ₅₀ of the primary particles of the sulfide solid electrolyte material was changed to 0.8 [mu] m, in the same manner as in Example 1 to obtain a test battery.

[Example 4]
A battery for evaluation was obtained in the same manner as in Example 1 except that SiO ₂ having an average primary particle size of 12 nm and an average secondary particle size of 54 nm was used as the inorganic solid material.

[Example 5]
As the inorganic solid material, SiO ₂ having an average primary particle size of 12 nm and an average secondary particle size of 54 nm is used, and the weight ratio of the sulfide solid electrolyte material and the inorganic solid material is set to sulfide solid electrolyte material: inorganic solid material = 99.0. : A battery for evaluation was obtained in the same manner as in Example 1 except that it was changed to 1.0.

[Comparative Example 1]
A battery for evaluation was obtained in the same manner as in Example 1 except that the inorganic solid material was not used.

[Comparative Example 2]
An evaluation battery was prepared in the same manner as in Example 1 except that the weight ratio of the sulfide solid electrolyte material and the inorganic solid material was changed to sulfide solid electrolyte material: inorganic solid material = 95.0: 5.0. Obtained.

[Comparative Example 3]
An evaluation battery was prepared in the same manner as in Example 1 except that the weight ratio of the sulfide solid electrolyte material and the inorganic solid material was changed to sulfide solid electrolyte material: inorganic solid material = 90.0: 10.0. Obtained.

[Comparative Example 4]
A battery for evaluation was obtained in the same manner as in Example 1 except that SiO ₂ (average particle diameter D ₅₀ = 0.8 μm), which is primary particles not aggregated, was used as the inorganic solid material.

[Comparative Example 5]
The average particle diameter D ₅₀ of the primary particles of the sulfide solid electrolyte material is changed to 0.8 μm, and SiO ₂ (average particle diameter D ₅₀ = 0.8 μm), which is an unaggregated primary particle, is used as the inorganic solid material. A battery for evaluation was obtained in the same manner as in Example 1 except that.

[Comparative Example 6]
Instead of the inorganic solid material, a sulfide solid electrolyte material (20LiI · 80 (0.75Li ₂ S · 0.25P ₂ S ₅ ), glass ceramics, average particle size D ₅₀ = 0.8 μm of primary particles) was used. A battery for evaluation was obtained in the same manner as in Example 1 except that.

[Comparative Example 7]
Instead of the inorganic solid material, a sulfide solid electrolyte material (20LiI · 80 (0.75Li ₂ S · 0.25P ₂ S ₅ ), glass ceramics, average particle diameter D ₅₀ = 0.8 μm of primary particles) The weight ratio of sulfide solid electrolyte material A having an average primary particle diameter D ₅₀ = 2.5 μm and sulfide solid electrolyte material B having an average primary particle diameter D ₅₀ = 0.8 μm is defined as A: B = An evaluation battery was obtained in the same manner as in Example 1 except that the ratio was changed to 75:25.

[Comparative Example 8]
A battery for evaluation was obtained in the same manner as in Example 1 except that SiO ₂ having an average primary particle size of 12 nm and an average secondary particle size of 100 nm was used as the inorganic solid material.

[Comparative Example 9]
As the inorganic solid material, SiO ₂ having an average primary particle size of 12 nm and an average secondary particle size of 100 nm is used, and the weight ratio of the sulfide solid electrolyte material and the inorganic solid material is determined as follows: sulfide solid electrolyte material: inorganic solid material = 99.0 : A battery for evaluation was obtained in the same manner as in Example 1 except that it was changed to 1.0. Table 1 shows the conditions of Examples 1 to 5 and Comparative Examples 1 to 9.

[Evaluation]
(Charge / discharge measurement)
Charge / discharge measurements were performed using the evaluation batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 7. In Examples 4 and 5 and Comparative Examples 8 and 9, no charge / discharge measurement is performed. Measurement conditions were 25 ° C., the potential range 3.0V～4.2V, current density ^{0.26mA / cm 2, 1.3mA / cm} 2 or 2.6 mA / ^cm 2, CC charge and discharge. When an internal short circuit occurred, charging did not end. In that case, charging was terminated and discharged in 20 hours. Moreover, coulomb efficiency was computed from the obtained charging / discharging capacity | capacitance. In addition, the presence or absence of the internal short circuit was judged from the presence or absence of a rapid voltage drop during charging and the coulomb efficiency. Specifically, the sudden voltage drop at the time of charging means that the charging curve has a waveform disturbance. Normally, the voltage increases sideways. The results of the charge / discharge measurement are shown in FIGS.

As shown in FIGS. 4A to 4C, in Examples 1 to 3, no obvious short circuit was confirmed at a current density of 0.26 mA / cm ^{2 to} 2.6 mA / cm ² , and charge and discharge were possible. there were. In contrast, as shown in FIG. 4 (d), in Comparative Example 1, although the apparent short circuit at a current density of 0.26 mA / cm ² was confirmed, 1.3 mA / cm ² or more current density A short circuit occurred during charging. FIG. 4 (e) is an enlarged view of FIG. 4 (d). In FIG. 4 (e), a rapid voltage drop during charging can be confirmed.

Similarly to Comparative Example 1, in Comparative Example 4 (FIG. 5 (c)) and Comparative Example 5 (FIG. 5 (d)), no obvious short circuit was observed at a current density of 0.26 mA / cm ² . However, a short circuit occurred during charging at a current density of 1.3 mA / cm ² or more. Further, in Comparative Example 2 (FIG. 5A), Comparative Example 3 (FIG. 5B), Comparative Example 6 (FIG. 5E), and Comparative Example 7 (FIG. 5F), 0.26 mA. Even at a current density of / cm ^2, a short circuit occurred and the battery could hardly be charged.

  As shown in Table 2, Examples 1 and 2 and Comparative Examples 2 and 3 have the same A / B value and C / B value, and the ratio of the inorganic solid material is different. The occurrence of a short circuit could be suppressed when it was within the range of 0.1 wt% to 1 wt%. In Examples 1 and 3 and Comparative Examples 4 and 5, the proportion of the inorganic solid material was common, but when the A / B value was in the range of 66 to 208, the occurrence of a short circuit could be suppressed. In Comparative Examples 6 and 7, a sulfide solid electrolyte material was used instead of the inorganic solid material, but a short circuit occurred. It has been confirmed that using a hard material such as an inorganic solid material is effective in suppressing a short circuit.

As shown in Table 2, Examples 1 to 3 showed a high Coulomb efficiency of 80% or more at a current density of 0.26 mA / cm ^{2 to} 2.6 mA / cm ² . In Comparative Examples 1, 4, and 5, since a short circuit occurred during charging at a current density of 1.3 mA / cm ² or more, the Coulomb efficiency was greatly reduced. Since Comparative Examples 2, 3, 6, and 7 could hardly be charged, the Coulomb efficiency was not calculated.

(Filling rate measurement and Li ion conductivity measurement)
A solid electrolyte layer was molded by putting 100 mg of the electrolyte mixture produced in Examples 1 to 5 and Comparative Examples 1 to 9 into a cylinder made by Macor and pressing it at 784 MPa. Next, both surfaces of the obtained solid electrolyte layer were sandwiched between SUS pistons and tightened with three bolts (torque = 2 Nm, surface pressure = 15 MPa). Next, the apparent density was calculated by measuring the thickness of the solid electrolyte layer. Apparent density of solid electrolyte layer = weight / (thickness × pellet area (1 cm ² )). Further, the true density of the solid electrolyte layer was calculated from the true density and content of the constituent components of the solid electrolyte layer. Incidentally, the true density of _{20LiI · 80 (0.75Li 2 S ·} 0.25P 2 S 5) and SiO ₂ are each 2.2 g / cm ³ and 2.65 g / cm ^3. True density of solid electrolyte layer = weight / (content of component / true density of component). From the apparent density and the true density, the filling rate of the solid electrolyte layer was calculated. Moreover, the impedance measurement was performed with respect to the solid electrolyte layer using the electrolyte compound material produced in Examples 1-3 and Comparative Examples 1-7, and Li ion conductivity was calculated | required. In Examples 4 and 5 and Comparative Examples 8 and 9, Li ion conductivity measurement is not performed. The results are shown in Table 2 above.

  As shown in Table 2, Examples 1 and 2 and Comparative Examples 2 and 3 have the same A / B value and C / B value, and the ratio of the inorganic solid material is different. Along with this, the Li ion conductivity decreased. Further, when the filling rate of Comparative Example 1 was used as a reference, the filling rate was improved in Examples 1 and 2, and the filling rate was lowered in Comparative Examples 2 and 3. Therefore, it was suggested that the improvement of the filling rate of the solid electrolyte layer contributed to the suppression of the short circuit. Examples 1 and 2 and Examples 4 and 5 have the same A / B value and different C / B values, but Example 4 is an example in which the content of the inorganic solid material is the same. The filling rate was higher than 1, and similarly, Example 5 had a higher filling rate than Example 2 in which the content of the inorganic solid material was the same. Therefore, it was suggested that generation | occurrence | production of a short circuit can be suppressed.

  Examples 1, 3, 4 and Comparative Examples 4, 5, 8 have the same ratio of the inorganic solid material. However, when the filling rate of Comparative Example 1 is used as a reference, Examples 1, 3, 4 have a filling rate of It improved and the filling rate fell in Comparative Examples 4, 5, and 8. Further, Comparative Example 8 and Comparative Example 9 had the same A / B value and C / B value, and differed in the proportion of the inorganic solid material, but the filling rate was similar. Thus, when the A / B value is in the range of 66 to 208 and the C / B value is in the range of 2.4 to 4.6, the filling rate of the solid electrolyte layer is improved. It was suggested that the short circuit could be suppressed. In addition, although the filling rate of Comparative Examples 6 and 7 became higher than the filling rate of Comparative Example 1, a short circuit occurred. This is because in the absence of inorganic solid material, the press pressure is difficult to be transmitted uniformly, or cracking due to the elastic change of the sulfide solid electrolyte material due to pressurization and depressurization during molding tends to occur. This is presumably due to the failure to remove the holes.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 6 ... Battery case 10 ... All solid lithium battery

Claims (1)

A solid electrolyte layer used in an all-solid lithium battery,
A sulfide solid electrolyte material, and an inorganic solid material represented by M _x O _y (M is a metal element, x and y are arbitrary numbers),
The inorganic solid material is a secondary particle in which primary particles are aggregated,
When the average particle size of the primary particles of the sulfide solid electrolyte material and the average particle size of the primary particles of the inorganic solid material are A and B, respectively, 66 ≦ A / B ≦ 208 is satisfied,
When the average particle size of the secondary particles of the inorganic solid material is C, 2.4 ≦ C / B ≦ 4.6 is satisfied,
The solid electrolyte layer, wherein the content of the inorganic solid material is in the range of 0.1 wt% to 1.0 wt%.

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