JP6256451B2 - All solid battery - Google Patents

Description

  The present invention relates to an all solid state battery that achieves both battery performance and safety.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, the development of batteries that are excellent as power sources has been regarded as important. In fields other than information-related equipment and communication-related equipment, for example, in the automobile industry, development of lithium-ion batteries as batteries used in electric cars and hybrid cars is being promoted.

  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. Furthermore, among all solid state batteries, all solid state batteries using sulfide solid electrolyte materials have the advantage of excellent Li ion conductivity.

For example, Patent Document 1 discloses a solid battery using a glass ceramic sulfide solid electrolyte material obtained by mixing and heating sulfides such as Li ₂ S and P ₂ S ₅ and LiI.

  As a technique for improving the battery performance of a solid battery, Patent Document 2 discloses a technique for improving the cycle characteristics of a battery by forming two solid electrolyte layers made of different materials. Further, Patent Document 3 discloses a technique for improving the interlayer adhesion of a battery by laminating a positive electrode layer, a crystalline crystal electrolyte layer, a vitreous glass electrolyte layer, and a negative electrode layer in this order.

JP 2014-130733 A JP 2001-351615 A JP 2014-216131 A

  The all solid state battery is known to have high safety because an electrolyte containing a flammable organic solvent is not used. However, even if it is an all-solid-state battery, when a severe test such as a nail penetration test is performed, smoke may be emitted from the battery (for example, resin of the outer package of the laminate) due to Joule heat generation. On the other hand, for example, when the ionic resistance of the battery is increased in order to suppress Joule heat generation, the battery performance is deteriorated. Therefore, the all-solid-state battery has a problem that it is difficult to achieve both battery performance and safety.

  The present invention has been made in view of the above circumstances, and has as its main object to provide an all-solid-state battery that achieves both battery performance and safety.

In order to achieve the above object, in the present invention, a first sulfide is formed between a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and the positive electrode layer and the negative electrode layer. A solid electrolyte layer containing a solid electrolyte material, wherein the ratio of the ionic resistance of the whole solid battery to the ionic resistance of the solid electrolyte layer is 3.8 or less; An all-solid-state battery having an ionic resistance of 7.6 Ω · cm ² or more and 16 Ω · cm ² or less is provided.

  According to the present invention, since the ionic resistance of the solid electrolyte layer and the ionic resistance of the entire all-solid battery have the above-described relationship, an all-solid battery that achieves both battery performance and safety can be obtained.

  In the above invention, it is preferable that at least one of the positive electrode layer and the negative electrode layer further contains a second sulfide solid electrolyte material.

  In the above invention, the first sulfide solid electrolyte material and the second sulfide solid electrolyte material are preferably different materials.

  In the said invention, it is preferable that the ionic conductivity of said 2nd sulfide solid electrolyte material is larger than the ionic conductivity of said 1st sulfide solid electrolyte material.

  The all-solid-state battery of the present invention has an effect that both battery performance and safety can be achieved.

It is a schematic sectional drawing which shows an example of the all-solid-state battery of this invention. It is a graph shown about the ionic resistance, reaction resistance, and diffusion resistance of the solid electrolyte layer of the all-solid-state battery of Examples 1-3 and Comparative Examples 1-3. It is a graph which shows the discharge behavior and temperature change by the nail penetration test of Example 1, Example 3, and Comparative Example 1. It is a graph which shows the result of the temperature rise amount (K) of the nail penetration test in Examples 1-3 and Comparative Examples 1-4.

Hereinafter, details of the all solid state battery of the present invention will be described.
FIG. 1 is a schematic sectional view showing an example of the all solid state battery of the present invention. An all-solid battery 10 shown in FIG. 1 is formed between a positive electrode layer 1 containing a positive electrode active material 11, a negative electrode layer 2 containing a negative electrode active material 12, and a positive electrode layer 1 and a negative electrode layer 2, and is a sulfide solid. And a solid electrolyte layer 3 containing an electrolyte material 13. The all-solid-state battery 10 usually includes a positive electrode current collector 4 that collects current from the positive electrode layer 1 and a negative electrode current collector 5 that collects current from the negative electrode layer 2. Further, in the all solid state battery 10, the ratio of the ionic resistance of the whole solid state battery 10 to the ionic resistance of the solid state electrolyte layer 3 is 3.8 or less, and the ionic resistance of the solid state electrolyte layer 3 is 7.6 Ω · cm ² or more, It is 16 Ω · cm ² or less.

  According to the present invention, since the ionic resistance of the solid electrolyte layer and the ionic resistance of the entire all-solid battery have the above-described relationship, an all-solid battery that achieves both battery performance and safety can be obtained.

  Conventionally, it has been recognized that an all-solid battery is safer than a liquid battery. On the other hand, when the internal resistance of the battery is low and the battery has high performance, the stability of the all-solid battery may not necessarily be high. As the most severe safety test, there is a nail penetration test. For example, when a high performance all-solid-state battery is fully charged with a nail penetration test, the temperature around the nail exceeds, for example, 250 ° C. due to Joule heat generation. There is a case where smoke is emitted from a battery (for example, resin of an outer package of a laminate).

Joule heat generation is generated when a current is passed through a conductor, and is represented by the following equation.
Q = I · V · t = V / R · V · t = V ² / R · t
(In the formula, Q is Joule heat generation (J), I is current (A), V is voltage (V), R is resistance (Ω), and t is seconds.)
Joule heat generation is determined by the amount (current) and voltage of electrons (≈ion) and the temperature that actually increases in the battery is determined by Joule heat generation and heat capacity. The current is calculated from voltage / resistance (ion resistance). That is, in order to suppress Joule heat generation, it is desired to increase the ionic resistance of the all solid state battery. On the other hand, when the ionic resistance of the all solid state battery is increased, there is a problem that the battery performance (capacity performance and output performance) is lowered. Therefore, the all-solid-state battery has a problem that it is difficult to achieve both battery performance and safety.

  As a result of intensive studies to achieve both battery performance and safety, the present inventors have focused on the balance between the ionic resistance of the solid electrolyte layer and the ionic resistance of the entire all-solid battery. As a result, the present invention has been completed.

Elements of ionic resistance in all solid state batteries include ionic resistance (DC resistance) of the solid electrolyte layer, ionic resistance (interface resistance) between the solid electrolyte layer and the electrode layer (positive electrode layer or negative electrode layer), and There are three factors: ionic resistance (diffusion resistance). Among these, the interfacial resistance and the diffusion resistance are highly dependent on the SOC (State of charge) and discharge rate of the all solid state battery. On the other hand, the ionic resistance of the solid electrolyte layer is less dependent on the SOC and discharge rate than other elements, so that all solid state batteries can be stably manufactured even under high SOC and high rate discharges. It can be a resistor that suppresses heat generation. In the present invention, by deliberately increasing the ionic resistance of the solid electrolyte layer (7.6 Ω · cm ² or more) and further increasing the ratio of the ionic resistance, a highly safe all-solid battery can be obtained. .

  Conventionally, it has been recognized that an all-solid battery is safer than a liquid battery. In general, all solid state batteries have lower battery performance than liquid type batteries. For this reason, the safety of all solid state batteries has not been fully studied. On the other hand, since the battery performance of all-solid-state batteries is improving day by day, it is necessary to study safety.

  Hereinafter, the configuration of the all solid state battery of the present invention will be described.

1. Ratio of ion resistance The all solid state battery of the present invention is characterized in that the ratio of the ion resistance (B) of the whole all solid state battery to the ion resistance (A) of the solid electrolyte layer, that is, B / A is 3.8 or less. To do. B / A may be 3.8 or less, more preferably 3.0 or less, and still more preferably 1.9 or less. Moreover, B / A is 1.25 or more, for example. This is because if B / A is too large, it may be difficult to ensure sufficient safety.
The ionic resistance of the solid electrolyte layer can be measured as a DC resistance by an AC impedance method. Moreover, the ionic resistance of the whole all-solid-state battery is the sum of the ionic resistance, reaction resistance, and diffusion resistance of the solid electrolyte layer, and can be determined by DC-IR measurement. In addition, although the resistance value obtained by DC-IR measurement is a value including both ion resistance and electronic resistance, since the ratio of electronic resistance is usually very small (about 1%), Can be considered.

  The B / A is a value based on the ionic resistance of the solid electrolyte layer, but the reciprocal A / B is a value based on the ionic resistance of the entire all-solid battery. A / B should just be 0.26 or more, it is more preferable that it is 0.33 or more, and it is further more preferable that it is 0.53 or more. Moreover, A / B is 0.8 or less, for example.

The ionic resistance (A) of the solid electrolyte layer is usually 7.6 Ω · cm ² or more. The ionic resistance of the solid electrolyte layer is usually 16 Ω · cm ² or less. Ion resistance of the entire all-solid-state cell (B) is, for example, 10 [Omega · cm ² or more, may be 15 [Omega] · cm ² or more. The ion resistance of the entire all-solid-state cell (B) is, for example, 40 [Omega · cm ² or less, preferably 20 [Omega · cm ² or less.

  Note that the difference (B−A) between the ionic resistance (B) of the entire all-solid battery and the ionic resistance (A) of the solid electrolyte layer corresponds to the sum of the interface resistance (reaction resistance) and the diffusion resistance.

  In the all solid state battery of the present invention, the ion resistance of each layer is adjusted so that A and B have the above-described relationship. The ion resistance of each layer can be adjusted by selecting the type (composition, physical properties), ratio, and thickness of each layer of the sulfide solid electrolyte material.

2. Solid Electrolyte Layer The solid electrolyte layer in the present invention is formed between the positive electrode layer and the negative electrode layer and contains the first sulfide solid electrolyte material. The sulfide solid electrolyte material contained in the solid electrolyte layer is referred to as a first sulfide solid electrolyte material for convenience.

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 —Li ₂ O, and 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 are positive Z is one of Ge, Zn, and Ga.), Li ₂ S—GeS ₂ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —Li _x MO _y (where, x and y are positive numbers, M is P, Si, Ge, B, Al, Ga, I Either.), And the like. The description of “Li ₂ S—P ₂ S ₅ ” means a sulfide solid electrolyte material using a raw material composition containing Li ₂ S and P ₂ S _5, and the same applies to other descriptions. is there. In particular, the sulfide solid electrolyte material is preferably a material mainly composed of Li ₂ S—P ₂ S ₅ . Furthermore, the sulfide solid electrolyte material preferably contains halogen (F, Cl, Br, I).

Also, if the sulfide solid electrolyte material is _Li 2 _S-P 2 _{S 5} based, the proportion of Li ₂ S and _P 2 _{S 5} in molar _{ratio, Li 2 S: P 2 S} 5 = 50: 50~ 100: preferably 0 in the range of, inter alia _{Li 2 S: P 2 S 5} = 70: 30~80: is preferably 20.

The sulfide solid electrolyte material may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (ball mill or the like) on the raw material composition. Crystallized sulfide glass can be obtained, for example, by subjecting sulfide glass to a heat treatment at a temperature equal to or higher than the crystallization temperature. Further, the Li ion conductivity at normal temperature (25 ° C.) of the sulfide solid electrolyte material is preferably 1 × 10 ⁻⁵ S / cm or more, for example, and preferably 1 × 10 ⁻⁴ S / cm or more. More preferred. Li ion conductivity can be measured by an AC impedance method.

Examples of the shape of the sulfide solid electrolyte material in the present invention include particle shapes such as true spheres and ellipsoids, and thin film shapes. When the sulfide solid electrolyte material has a particle shape, the average particle diameter (D ₅₀ ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and more preferably 10 μm or less. More preferably. This is because it becomes easy to improve the filling rate in the positive electrode layer. On the other hand, the average particle diameter is preferably 0.01 μm or more, and more preferably 0.1 μm or more. In addition, an average particle diameter can be determined with a particle size distribution meter, for example.

  The content of the sulfide solid electrolyte material in the solid electrolyte layer is, for example, preferably in the range of 10% by weight to 100% by weight, and more preferably in the range of 50% by weight to 100% by weight.

  In addition to the above-described materials, the solid electrolyte layer contains a fluorine-containing binder such as acrylate butadiene rubber (ABR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE) or the like as necessary. May be. The thickness of the solid electrolyte layer is preferably in the range of 0.1 μm to 1000 μm, for example, and more preferably in the range of 0.1 μm to 300 μm.

3. Positive electrode layer The positive electrode layer in the present invention is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte material, a conductive material, and a binder as necessary.

The type of the positive electrode active material is appropriately selected according to the type of the all solid state battery, and examples thereof include an oxide active material and a sulfide active material. Examples of the oxide active material include rock salt layered 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 , LiNi _0. Examples include spinel active materials such as ₅ Mn _1.5 O ₄ , olivine active materials such as LiFePO ₄ and LiMnPO ₄ , and Si-containing active materials such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ . Moreover, as an oxide active material other than the above, for example, Li ₄ Ti ₅ O ₁₂ can be given.

Examples of the shape of the positive electrode active material include particles and thin films. When the positive electrode active material is in the form of particles, the average particle diameter (D ₅₀ ) is preferably in the range of, for example, 1 nm to 100 μm, and more preferably in the range of 10 nm to 30 μm. If the average particle size of the positive electrode active material is too small, the handleability may be deteriorated. On the other hand, if the average particle size is too large, it may be difficult to obtain a flat positive electrode layer. It is.

  Although content of the positive electrode active material in a positive electrode layer is not specifically limited, For example, it is preferable to exist in the range of 40 weight%-99 weight%.

  The positive electrode layer preferably contains a second sulfide solid electrolyte material in addition to the positive electrode active material. The sulfide solid electrolyte material contained in the electrode layer is referred to as a second sulfide solid electrolyte material for convenience. Since the specific example of the second sulfide solid electrolyte material is the same as that of the first sulfide solid electrolyte material described above, description thereof is omitted here. In the present invention, the first sulfide solid electrolyte material and the second sulfide solid electrolyte material may be the same material or different materials.

  Here, the “different material” means at least one of the case where the chemical characteristics are different, the physical characteristics are different, and the physical properties are different. Examples of different chemical characteristics include a case where the composition is different and a case where the crystallinity (amorphous) is different. Examples of the case where the physical characteristics are different include a case where the particle diameter is different and a case where the shape is different. Examples of cases where the physical properties are different include cases where the ionic conductivity is different. The physical property difference is usually a difference caused by a difference in at least one of chemical characteristics and physical characteristics.

  The ionic conductivity of the second sulfide solid electrolyte material is preferably larger than the ionic conductivity of the first sulfide solid electrolyte material. Specifically, the ratio between the two (the ionic conductivity of the second sulfide solid electrolyte material / the ionic conductivity of the first sulfide solid electrolyte material) is preferably greater than 1, and is 1.1 or more. May be 1.5 or more, and may be 2 or more. Furthermore, based on the result of the Example mentioned later, ratio of both may be 3.4 or more, and may be 14 or more.

  The content of the second sulfide solid electrolyte material in the positive electrode layer used in the present invention is, for example, preferably in the range of 1 wt% to 90 wt%, and in the range of 10 wt% to 80 wt%. It is more preferable.

  The positive electrode layer in the present invention may further contain at least one of a conductive material and a binder in addition to the positive electrode active material and the second solid electrolyte material described above. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber (VGCF). Examples of the binder include fluorine-containing binders such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE). The thickness of the positive electrode layer varies depending on the intended configuration of the all-solid-state battery, but is preferably in the range of 0.1 μm to 1000 μm, for example.

4). Negative electrode layer The negative electrode layer in the present invention is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte material, a conductive material, and a binder as necessary.

  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 negative electrode layer preferably contains a second sulfide solid electrolyte material in addition to the negative electrode active material. The second sulfide solid electrolyte material is the same as described above. The second sulfide solid electrolyte material contained in the negative electrode layer and the second sulfide solid electrolyte material contained in the positive electrode layer may be the same material or different materials.

  The conductive material and the binder used for the negative electrode layer are the same as in the positive electrode layer described above. Moreover, it is preferable that the thickness of a negative electrode layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

5. Other Configurations The all solid state battery obtained by the present invention has at least a positive electrode layer, a negative electrode layer, and a solid electrolyte layer. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material and a negative electrode current collector for collecting current of the negative electrode active material. 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. In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the all solid state battery. Moreover, the battery case used in this invention can use the battery case used for a general all-solid-state battery, for example, the battery case made from SUS, etc. Further, the all solid state battery obtained by the present invention may be one in which the power generation element is formed inside the insulating ring, or may be one sealed with an exterior body. As an exterior body, what is used for a general battery can be used, For example, an aluminum laminate film etc. can be mentioned. Moreover, as an all-solid-state battery, a single layer battery may be sufficient and the laminated battery which laminated | stacked the single layer battery may be sufficient.

6). All-solid-state battery The all-solid-state battery (all-solid-state lithium battery) obtained by the present invention 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. When the all-solid-state battery obtained by the present invention is used as an in-vehicle battery, examples of the target vehicle include an electric vehicle with a battery and no engine, and a hybrid vehicle with both a battery and an engine. Examples of the shape of the all solid state battery obtained by the present invention include a coin type, a laminate type, a cylindrical type, and a square type.

  The safety of the all solid state battery of the present invention can be evaluated by, for example, a nail penetration test. The nail penetration test is usually performed according to the UL standard (UL1642) or JIS B8714. Specifically, it can be performed using a commercially available nail penetration tester.

  Although the environmental temperature of the nail penetration test is 25 ° C. as a legal requirement, it can be in the range of 25 ° C. to 80 ° C., for example. The material of the nail used in the nail penetration test is not particularly limited, and for example, SK material (carbon tool steel material), SUS (stainless steel), other metal materials, and the like can be used.

  The temperature increase amount (K) by the nail penetration test is, for example, preferably 100K or less, and more preferably 60K or less. This is because smoke generation or the like due to Joule heat generation can be suitably suppressed. The temperature rise (K) is a value obtained by subtracting the environmental temperature (° C.) from the measured maximum temperature (° C.).

  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.

[Production Example 1: Production of solid electrolytes 1 to 4]
(Synthesis of sulfide solid electrolyte materials)
As starting materials, lithium sulfide (Li ₂ S), diphosphorus pentasulfide (P ₂ S ₅ ) and lithium iodide (LiI) were used. Next, in a glove box under an Ar atmosphere (dew point −70 ° C.), Li ₂ S and P ₂ S ₅ have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Weighed as follows. Next, LiI was weighed so that LiI was 10 mol%. 2 g of this mixture is put into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is added, and ZrO 2 balls (φ = 5 mm, 53 g) are further charged. 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. Thereafter, the obtained sample was dried on a hot plate so as to remove heptane to obtain a sulfide solid electrolyte material. The composition of the obtained sulfide solid electrolyte material was 10LiI · 90 (0.75Li ₂ S · 0.25P ₂ S ₅ ).

(Particulate and crystallize sulfide solid electrolyte material)
The synthesized sulfide solid electrolyte material is microparticulated and crystallized by the following method to obtain the sulfide solid electrolyte materials (solid electrolytes 1 to 4) shown in Table 1 below having different Li ion conductivity and particle size. Obtained.

The total weight of the sulfide solid electrolyte material obtained by the synthesis step, dehydrated heptane (manufactured by Kanto Chemical) and dibutyl ether is 10 g, and the ratio of the weight of the sulfide solid electrolyte material in the total weight is predetermined. It adjusted so that it might become a ratio. Sulfide solid electrolyte material, dehydrated heptane, and dibutyl ether and 40 g of ZrO ₂ balls (φ0.3 mm, φ0.6 mm, or φ1 mm) were put into a 45 ml ZrO ₂ pot, and the pot was completely sealed (Ar atmosphere). By attaching this pot to a planetary ball mill (P7 made by Fritsch) and performing wet mechanical milling for 10 to 20 hours at a revolution speed of 100 to 200 rpm, the sulfide solid electrolyte material is pulverized and made into fine particles. It was.

  By placing 1 g of a sulfide solid electrolyte material finely divided into fine particles on an aluminum petri dish and holding it on a hot plate heated to 180 ° C. for 2 hours, the fine particle sulfide The solid electrolyte material was crystallized.

[Evaluation]
(Measurement of lithium ion conductivity)
Li ion conductivity of the obtained solid electrolytes 1 to 4 was measured. Specifically, a 1 cm ² , 0.5 mm thick pellet was prepared using the sulfide solid electrolyte material recovered after crystallization, and was molded at 4.3 ton. The lithium ion conductivity (25 ° C.) was measured by the method. In addition, the solartron 1260 was used for the measurement, the measurement conditions were an applied voltage of 5 mV, a measurement frequency range of 0.01 MHz to 1 MHz, a resistance value of 100 kHz was read, corrected by thickness, and converted into lithium ion conductivity. The results are shown in Table 1.
Show.

(Measurement of average particle size)
The average particle diameters of the obtained solid electrolytes 1 to 4 were measured. Specifically, a small amount of crystallized particulate solid electrolytes 1 to 4 are sampled, and the particle size distribution is measured with a laser scattering / diffraction particle size distribution analyzer (Nikkiso Microtrac MT 3300EXII). D ₅₀ ) was determined. The results are shown in Table 1.

[Production Example 2: Production of laminated battery]
(Preparation of positive electrode mixture slurry)
A composition prepared by dissolving equimolar LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₅ in an ethanol solvent was prepared as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (Nichia Corporation) The surface of the company was spray-coated using a tumbling fluidized coating apparatus (SFP-01, manufactured by POWREC Co., Ltd.). Thereafter, the coated LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is heat-treated at 350 ° C. under atmospheric pressure for 1 hour, thereby producing LiNi _1/3 Co _1/3 Mn _1/3. A layer of LiNbO ₃ (coating layer) was formed on the surface of O ₂ (active material) to produce a positive electrode active material. The average particle diameter (D ₅₀ ) of the positive electrode active material was 5 μm. 52 g of the obtained positive electrode active material, 17 g of the sulfide solid electrolyte material, 1 g of vapor grown carbon fiber (VGCF (registered trademark)) as a conductive material and 15 g of dehydrated heptane (Kanto Chemical Co., Ltd.) were weighed and mixed thoroughly. Thus, a positive electrode mixture slurry was obtained.

(Preparation of negative electrode mixture slurry)
As a negative electrode active material, 36 g of graphite (Mitsubishi Chemical Corporation) and 25 g of a sulfide solid electrolyte material were weighed and mixed thoroughly to obtain a negative electrode mixture slurry.

(Production of all-solid battery)
The positive electrode mixture slurry was applied to an Al foil (positive electrode current collector), and the negative electrode mixture slurry was applied to a Cu foil (negative electrode current collector) at an arbitrary thickness and dried to obtain a positive electrode layer and a negative electrode layer. Further, the obtained laminate was cut to obtain a positive electrode and a negative electrode.
The sulfide solid electrolyte material and the binder (ABR) were mixed at a sulfide solid electrolyte material: ABR = 98: 2 (volume ratio). The mixture was pressed at 4.3 ton / cm ² to obtain a sheet-like solid electrolyte layer. The solid electrolyte layer was transferred between the positive electrode and the negative electrode, and pressed at 4.3 ton / cm ² to produce a single-layer battery. In general, the press pressure is preferably 2 tons or more. The single-layer battery was laminated in eight layers, and the current collecting tab was ultrasonically welded to the cell terminal of the single-layer battery. A 0.5 Ah-class laminated battery was obtained by vacuum-sealing the outside of the laminate with an aluminum laminate material.

[Examples 1-3, Comparative Examples 1-3]
A laminated battery was produced by the combinations shown in Table 2 and Table 3 below.

[Evaluation]
(Battery capacity evaluation)
About the laminated battery of Examples 1-3 and Comparative Examples 1-3, battery capacity was evaluated on condition of the following. Constant current charge-constant current discharge was performed. Moreover, it was set as 10 hour rate charging / discharging, and it was set as charging / discharging electric current: 0.3046mA. The charge stop voltage was 4.55V, and the discharge stop voltage was 3.0V.

(Battery resistance evaluation)
About the laminated batteries of Examples 1 to 3 and Comparative Examples 1 to 3, constant current-constant voltage charging was performed at a charging voltage of 3.6V. The end current was 0.015 mA. Immediately thereafter, DC resistance and reaction resistance were measured by the AC impedance method, and the DC resistance was defined as the ionic resistance of the solid electrolyte layer. Moreover, the ionic resistance of the whole all-solid-state battery was measured by DC-IR measurement. The results are shown in Table 4 and FIG.

(Nail penetration test)
The laminated batteries of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared by being fully charged. The laminated battery was installed in a nail penetration tester having an environmental temperature of 60 ° C. Using a nail penetration tester, a nail was inserted into the center of the battery at a speed of 10 mm / sec, and the discharge behavior, the heat generation temperature, and the presence or absence of smoke were observed. In the nail penetration test, current flow tends to occur when the nail is inserted at a low speed.
The temperature was measured at a position 7 mm above the nail penetration. Further, the temperature rise (K) was calculated by subtracting the environmental temperature (° C.) from the measured maximum temperature (° C.).
As Comparative Example 4, the same laminated battery as in Comparative Example 1 was fully charged and prepared, and a nail penetration test was similarly performed at an environmental temperature of 25 ° C. The results are shown in Table 4, FIG. 3 and FIG.

As shown in Table 4 and FIG. 2, the overall resistance in Examples 1 to 3 (the ionic resistance of the whole all solid state battery) was almost the same as in Comparative Examples 1 to 3. Therefore, it was suggested that the laminated batteries obtained in Examples 1 to 3 show the identified battery performance with the laminated batteries obtained in Comparative Examples 1 to 3. On the other hand, the ratio of the direct current resistance (ionic resistance of the solid electrolyte layer) in Examples 1 to 3 was larger than that in Comparative Examples 1 to 3.
Moreover, as shown in Table 4, FIG. 3, and FIG. 4, the laminated battery of Examples 1-3 has a small temperature rise amount compared with the laminated battery of Comparative Examples 1-3, and smoke is not produced. It was confirmed that the safety against Joule heat generation was high.
Further, as shown in Comparative Example 4, the battery having the configuration of Comparative Example 1 has a temperature increase amount as compared with Examples 1 to 3 even when a nail penetration test is performed at an environmental temperature of 25 ° C., which is a legal requirement. It was expensive and smoke was generated. Therefore, it was confirmed that the laminated batteries of Examples 1 to 3 can ensure the safety against Joule heat generation even at a severe environmental temperature.
Thus, in Examples 1-3, compared with Comparative Examples 1-3, the safety performance could be improved while maintaining the battery performance (both battery performance and safety were compatible).

DESCRIPTION OF SYMBOLS 1 ... Positive electrode layer 2 ... Negative electrode layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 10 ... All-solid-state battery 11 ... Positive electrode active material 12 ... Negative electrode active material 13 ... Sulfide solid electrolyte material

Claims (4)

A positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer and containing a first sulfide solid electrolyte material A solid state battery,
The ratio of the ionic resistance of the whole solid-state battery to the ionic resistance of the solid electrolyte layer is 3.8 or less, and the ionic resistance of the solid electrolyte layer is 7.6 Ω · cm ² or more and 16 Ω · cm ² or less. All-solid battery characterized by.   The all-solid-state battery according to claim 1, wherein at least one of the positive electrode layer and the negative electrode layer further contains a second sulfide solid electrolyte material.   The all-solid-state battery according to claim 2, wherein the first sulfide solid electrolyte material and the second sulfide solid electrolyte material are different materials.   4. The all-solid-state battery according to claim 2, wherein an ionic conductivity of the second sulfide solid electrolyte material is larger than an ionic conductivity of the first sulfide solid electrolyte material. 5.