JP5696353B2 - All solid state battery system - Google Patents

Description

  The present invention relates to an all-solid-state battery system that can suppress an increase in internal resistance during high temperature use and has excellent output characteristics.

  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 (eg, lithium 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 batteries and the like used for electric cars and hybrid cars is being promoted.

  Here, since a commercially available lithium battery uses an organic electrolyte solution that uses a flammable organic solvent, a structure for preventing the installation of a safety device and preventing a short circuit that suppresses the temperature rise at the time of a short circuit. Improvements in materials are necessary. In contrast, an all-solid-state battery in which the liquid electrolyte is changed to a solid electrolyte does not use a flammable organic solvent in the battery, so the safety device can be simplified, and the manufacturing cost and productivity are considered excellent. Yes.

Conventionally, sulfide solid electrolyte materials are known in the field of such all-solid batteries. Patent Document 1 discloses an all-solid battery using lithium cobaltate as a positive electrode active material and Li ₂ S—P ₂ S ₅ crystallized glass as a sulfide solid electrolyte material. This all-solid-state battery has the advantage that Li ion conductivity is high and the output can be increased because the sulfide solid electrolyte material has cross-linked sulfur. However, the sulfide solid electrolyte material having bridging sulfur has a problem in that the chemical resistance of the sulfide solid electrolyte material is likely to occur during high temperature use, and the internal resistance increases. Therefore, there is a problem that it is not possible to achieve high output due to high temperature use. Non-Patent Document 1 also discloses various sulfide solid electrolyte materials. Non-Patent Document 2 discloses a crystal structure of Li ₇ S ₃ P ₁₁ which is a Li ion conductor.

JP 2002-109955 A

Akitoshi Hayashi et al., “Characterization of Li2S-SiS2-Li3MO3 (M = B, Al, Ga and In) oxysulfide glasses and their application to solid state lithium secondary batteries”, Solid State Ionics, 152-153 (2002) 285- 290 Hisanori Yamane et al., “Crystal structure of a superionic conductor, Li7P3S11”, Solid State Ionics, 178 (2007) 1163-1167

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide an all-solid-state battery system that can suppress an increase in internal resistance during high temperature use and has excellent output characteristics.

  In order to solve the above problems, in the present invention, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a gap between the positive electrode active material layer and the negative electrode active material layer. An all-solid battery having the formed solid electrolyte layer, and a heating means for heating the all-solid battery to 40 ° C. or higher, and the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer Provided is an all-solid battery system characterized in that at least one contains a sulfide solid electrolyte material substantially free of bridging sulfur.

  According to the present invention, an increase in internal resistance during high temperature use can be suppressed by using a sulfide solid electrolyte material that has substantially no cross-linking sulfur. Thereby, it can be set as the all-solid-state battery system excellent in the output characteristic.

In the above invention, the sulfide solid electrolyte material is a Li ₂ S—P ₂ S ₅ material, a Li ₂ S—SiS ₂ material, a Li ₂ S—GeS ₂ material, or a Li ₂ S—Al ₂ S ₃ material. it is _preferred, more preferably Li 2 _S-P 2 _{S 5} material. This is because the Li ion conductivity is excellent.

  In the said invention, it is preferable that the said sulfide solid electrolyte material is sulfide glass or crystallized sulfide glass. Since sulfide glass is softer than crystallized sulfide glass, it has the advantage that it can absorb the expansion and contraction of the active material when an all-solid battery is produced and has excellent cycle characteristics. On the other hand, crystallized sulfide glass has an advantage that Li ion conductivity may be higher than sulfide glass.

  In the said invention, it is preferable that the said positive electrode active material is an oxide positive electrode active material. This is because by using the oxide positive electrode active material, an all-solid battery having a high energy density can be obtained.

  In the all-solid-state battery system of this invention, there exists an effect that the increase in internal resistance at the time of high temperature use can be suppressed.

It is a schematic sectional drawing which shows an example of the all-solid-state battery system of this invention. It is a schematic sectional drawing explaining the heat generating body in this invention. It is a schematic sectional drawing which shows the electric power generation element of an all-solid-state battery. It is a graph which shows the relationship between charging / discharging cycle number and internal resistance increase rate. 4 is a graph showing the relationship between the operating temperature and internal resistance of the all solid lithium secondary battery obtained in Example 1. FIG. It is the result of the Raman spectroscopic measurement with respect to the positive electrode compound material etc. in Example 1. FIG. It is the result of the Raman spectroscopic measurement with respect to the positive electrode compound material etc. in the comparative example 1. It is the result of the Raman spectroscopic measurement with respect to the positive electrode compound material etc. in Example 2. FIG. It is a result of the Raman spectroscopic measurement with respect to the positive electrode compound material etc. in Example 3. FIG. It is a result of the Raman spectroscopic measurement of the sulfide solid electrolyte material obtained in Reference Examples 1-1 to 1-5. It is a result of the X-ray-diffraction measurement of the sulfide solid electrolyte material obtained by the reference examples 1-1, 1-3, 1-4, and 1-6.

  Hereinafter, the all solid state battery system of the present invention will be described in detail.

  The all-solid-state battery system of the present invention is formed between a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and the positive electrode active material layer and the negative electrode active material layer. An all-solid battery having a solid electrolyte layer and a heating means for heating the all-solid battery to 40 ° C. or higher, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is And a sulfide solid electrolyte material substantially free from bridging sulfur.

  According to the present invention, an increase in internal resistance during high temperature use can be suppressed by using a sulfide solid electrolyte material that has substantially no cross-linking sulfur. Thereby, it can be set as the all-solid-state battery system excellent in the output characteristic. In general, the temperature dependence of the ionic conductivity of the solid electrolyte material follows the Arrhenius plot. Therefore, the Li ion conductivity of the solid electrolyte material increases and the internal resistance of the battery decreases as the temperature rises. However, if a battery using a sulfide solid electrolyte material having bridging sulfur is operated at a high temperature, a reaction occurs at the site of the bridging sulfur due to heat, the sulfide solid electrolyte material chemically deteriorates, and the internal resistance of the battery increases. There is a problem of doing. On the other hand, in the present invention, by using a sulfide solid electrolyte material substantially free of cross-linked sulfur, chemical deterioration of the sulfide solid electrolyte material due to heat can be suppressed, and the internal resistance can be increased. Can be suppressed. As a result, an all-solid battery system with excellent output characteristics can be obtained. That is, in the present invention, focusing on the fact that the bridging sulfur of the sulfide solid electrolyte material is thermally unstable, by using the sulfide solid electrolyte material that does not have the bridging sulfur, It has been found that the increase in resistance can be suppressed.

Note that Non-Patent Document 1 described above discloses an experimental result of charging and discharging an all-solid battery using a sulfide solid electrolyte material containing bridging sulfur at 70 ° C. (FIG. 1 of Non-Patent Document 1). 6). However, 95 (0.6Li ₂ S · 0.4SiS ₂ ) · 5Li ₃ BO ₃ used in the experiment is considered to have bridging sulfur in view of the production method, and sulfides are used during high temperature use. It is considered that the solid electrolyte material is chemically deteriorated and the internal resistance is increased. Moreover, the all-solid-state battery in this invention uses a solid electrolyte layer. If a liquid electrolyte (electrolytic solution) is used, the decomposition of the electrolytic solution becomes significant at a high temperature range of 40 ° C. or higher, and thus it is usually difficult to use at such a high temperature range. Therefore, the feature of using a heating means of 40 ° C. or higher is considered to be a feature unique to an all-solid battery having a solid electrolyte layer.

  FIG. 1 is a schematic sectional view showing an example of the all solid state battery system of the present invention. An all solid state battery system 20 shown in FIG. 1 includes an all solid state battery 10, a heating element 11, a temperature detection unit 12 that detects the temperature of the heating element 11, and a control unit 13 that controls the temperature of the heating element 11. It is comprised from a heating means. Further, the all solid state battery 10 includes a positive electrode active material layer 1, a negative electrode active material layer 2, a solid electrolyte layer 3, and a battery case 4. In the present invention, the heating means heats the all-solid battery 10 to 40 ° C. or higher, and at least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the solid electrolyte layer 3 is substantially crosslinked sulfur. The main feature is that it contains a sulfide solid electrolyte material that does not contain any of the above.

Next, chemical degradation of the sulfide solid electrolyte material due to heat will be described using a case where the sulfide solid electrolyte material is a Li ₂ S—P ₂ S ₅ material. When the sulfide solid electrolyte material is a Li ₂ S—P ₂ S ₅ material, depending on the ratio of Li ₂ S and P ₂ S ₅ during synthesis, heat treatment conditions, and the like, the following PS ₄ units and P ₂ S _{7 are used.} A unit is formed.

The PS ₄ unit has no cross-linking sulfur, and the P ₂ S ₇ unit has cross-linking sulfur. As described in the examples described later, the PS ₄ unit has high thermal stability, and can maintain its structure even when the battery is operated at a high temperature of 40 ° C. or higher, for example. On the other hand, since the P ₂ S ₇ unit has low thermal stability (high reactivity of crosslinking sulfur), when the battery is operated at a high temperature, the structure cannot be maintained. To P ₂ S ₆ units.

Li ₄ P ₂ S ₆ , which is a crystal of this P ₂ S ₆ unit, is known to have low Li ion conductivity, and as a result, the internal resistance of the battery is considered to increase. Thus, when a sulfide solid electrolyte material having crosslinked sulfur is used, a reaction occurs at the site of the crosslinked sulfur due to heat, the sulfide solid electrolyte material is chemically deteriorated, and the internal resistance of the battery increases. is there. On the other hand, in the present invention, by using a sulfide solid electrolyte material substantially free of cross-linked sulfur, chemical deterioration of the sulfide solid electrolyte material is suppressed, and the internal resistance of the battery at the time of high temperature use is increased. Can be suppressed.
Hereinafter, the all-solid-state battery system of this invention is demonstrated for every structure.

1. All-solid battery The all-solid battery in the present invention is formed between a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and the positive electrode active material layer and the negative electrode active material layer. A solid electrolyte layer.

(1) Solid electrolyte layer First, the solid electrolyte layer in this invention is demonstrated. The solid electrolyte layer in the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer. The solid electrolyte material used for the solid electrolyte layer is not particularly limited as long as it has ion conductivity, but among them, a sulfide solid electrolyte material is preferable. This is because ionic conductivity is high. In particular, in the present invention, it is preferable that the sulfide solid electrolyte material used for the solid electrolyte layer is a sulfide solid electrolyte material substantially free of cross-linked sulfur. This is because a battery having a low internal resistance when used at a high temperature can be obtained.

  In the all solid state battery of the present invention, at least one of the solid electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer may contain a sulfide solid electrolyte material that does not substantially contain cross-linked sulfur. Among them, in the present invention, it is preferable that at least the solid electrolyte layer contains the sulfide solid electrolyte material. This is because the solid electrolyte layer has a great influence on the internal resistance of the battery. Furthermore, in the present invention, it is more preferable that at least the solid electrolyte layer and the positive electrode active material layer contain the sulfide solid electrolyte material. This is because an increase in internal resistance can be further suppressed by suppressing the reaction between the positive electrode active material and the sulfide solid electrolyte material. In particular, in the present invention, it is preferable that all of the solid electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer contain the sulfide solid electrolyte material.

(I) Sulfide solid electrolyte material substantially free of cross-linked sulfur Next, a sulfide solid electrolyte material substantially free of cross-linked sulfur will be described. Here, “bridged sulfur” refers to a sulfur element having an —S— bond generated during the synthesis of the sulfide solid electrolyte material. For example, when the sulfide solid electrolyte material is a Li ₂ S—P ₂ S ₅ material, a sulfur element of S ₃ P—S—PS ₃ (P ₂ S ₇ unit described above) or the like is applicable. Such bridging sulfur is susceptible to heat and causes an increase in internal resistance when used at high temperatures.

“Substantially no cross-linking sulfur” can be confirmed by measurement of Raman spectroscopy. For example, when the sulfide solid electrolyte material is Li ₂ S—P ₂ S ₅ material, the peak of P ₂ S ₇ unit usually appears at 402 cm ⁻¹ . Therefore, in the present invention, it is preferable that this peak is not detected. Moreover, the peak of PS ₄ units usually appears at 417 cm ⁻¹ . In the present invention, the intensity _{I 402} at 402 cm ^-1 is preferably smaller than the intensity _{I 417} at 417 cm ^-1. More specifically, the strength I ₄₀₂ is preferably 70% or less, more preferably 50% or less, and even more preferably 35% or less with respect to the strength I ₄₁₇ . Note that “substantially no cross-linked sulfur” can be confirmed by using the raw material composition ratio when synthesizing the sulfide solid electrolyte material and the NMR measurement result in addition to the measurement result of the Raman spectrum. Can do.

Specifically, as the sulfide solid electrolyte material having substantially no crosslinking sulfur, a material composition containing Li ₂ S and a sulfide of an element belonging to Group 13 to Group 15 is used. Can be mentioned. Examples of a method for synthesizing the sulfide solid electrolyte material using such a raw material composition include an amorphization method. Examples of the amorphization method include a mechanical milling method and a melt quenching method, and among them, the mechanical milling method is preferable. This is because processing at room temperature is possible, and the manufacturing process can be simplified.

Examples of the Group 13 to Group 15 elements include Al, Si, Ge, P, As, and Sb. Moreover, as a sulfide of an element of Group 13 to Group 15, specifically, Al ₂ S ₃ , SiS ₂ , GeS ₂ , P ₂ S ₃ , P ₂ S ₅ , As ₂ S ₃ , Sb ₂ S ₃ etc. can be mentioned. Among these, in the present invention, it is preferable to use a Group 14 or Group 15 sulfide. In particular, in the present invention, the sulfide solid electrolyte material using a raw material composition containing Li ₂ S and a sulfide of an element belonging to Group 13 to Group 15 is Li ₂ S—P ₂ S. ₅ materials, Li ₂ S—SiS ₂ material, Li ₂ S—GeS ₂ material or Li ₂ S—Al ₂ S ₃ material are preferable, and Li ₂ S—P ₂ S ₅ material is more preferable. This is because the Li ion conductivity is excellent.

Also, the sulfide solid electrolyte material, if it is made by using the raw material composition containing Li 2 _S, the sulfide solid electrolyte material preferably has substantially no Li 2 _S. By "substantially free of Li 2 _S" it means that it does not contain Li 2 _S derived from starting materials substantially. Li ₂ S is susceptible to heat and can cause an increase in internal resistance when used at high temperatures. “Substantially no Li ₂ S” can be confirmed by X-ray diffraction. Specifically, when it does not have a Li ₂ S peak (2θ = 27.0 °, 31.2 °, 44.8 °, 53.1 °), it is determined that it does not substantially contain Li ₂ S. can do. If the ratio of Li ₂ S in the raw material composition is too large, the sulfide solid electrolyte material tends to contain Li ₂ S. Conversely, if the ratio of Li ₂ S in the raw material composition is too small, The sulfide solid electrolyte material tends to contain the above-mentioned crosslinked sulfur.

When the sulfide solid electrolyte material does not substantially contain bridging sulfur and Li ₂ S, the sulfide solid electrolyte material usually has an ortho composition or a composition in the vicinity thereof. Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li ₂ S is added most in the sulfide is called the ortho composition. For example, in the Li ₂ S—P ₂ S ₅ system, Li ₃ PS ₄ corresponds to the ortho composition, in the Li ₂ S—Al ₂ S ₃ system, Li ₃ AlS ₃ corresponds to the ortho composition, and Li ₂ S—SiS _2. In the system, Li ₄ SiS ₄ corresponds to the ortho composition, and in the Li ₂ S—GeS ₂ system, Li ₄ GeS ₄ corresponds to the ortho composition. For example, in the case of a Li ₂ S—P ₂ S ₅ based sulfide solid electrolyte material, the ratio of Li ₂ S and P ₂ S ₅ to obtain the ortho composition is Li ₂ S: P ₂ S ₅ = 75 in terms of mole. : 25. Similarly, in the case of a Li ₂ S—Al ₂ S ₃ -based sulfide solid electrolyte material, the ratio of Li ₂ S and Al ₂ S ₃ to obtain the ortho composition is Li ₂ S: Al ₂ S ₃ = 75:25. On the other hand, in the case of a Li ₂ S—SiS ₂ -based sulfide solid electrolyte material, the ratio of Li ₂ S and SiS ₂ to obtain the ortho composition is Li ₂ S: SiS ₂ = 66.7: 33. 3. Similarly, in the case of a Li ₂ S—GeS ₂ -based sulfide solid electrolyte material, the ratio of Li ₂ S and GeS ₂ to obtain the ortho composition is Li ₂ S: GeS ₂ = 66.7: 33. 3.

The raw material composition is, when containing Li ₂ S and _P 2 _{S 5,} the material composition may be one containing only Li ₂ S and _P 2 _{S 5,} those with other compounds There may be. The ratio of Li ₂ S and P ₂ S ₅ is preferably in the range of Li ₂ S: P ₂ S ₅ = 70 to 85:15 to 30 in terms of mole, and Li ₂ S: P ₂ S ₅ = More preferably, it is in the range of 70-80: 20-30, and more preferably in the range of Li ₂ S: P ₂ S ₅ = 72-78: 22-28. It is because the increase in internal resistance at the time of high temperature use can be further suppressed by setting the ratio of both to a range including the ratio (Li ₂ S: P ₂ S ₅ = 75: 25) for obtaining the ortho composition and the vicinity thereof. . Incidentally, the raw material composition is, when containing Li ₂ S and _Al 2 _{S 3,} the ratio or the like of Li ₂ S and _Al 2 _{S 3} is the same as the ratio or the like of Li ₂ S and _P 2 _{S 5} mentioned above Preferably there is.

On the other hand, when the raw material composition contains Li ₂ S and SiS ₂ , the raw material composition may contain only Li ₂ S and SiS ₂ , and has other compounds. Also good. The ratio of Li ₂ S and SiS ₂ is preferably in the range of Li ₂ S: SiS ₂ = 50 to 80:20 to 50 in terms of mole, and Li ₂ S: SiS ₂ = 55 to 75:25. more preferably in the range of _{45, Li 2 S: SiS 2} = 60~70: and even more preferably within the range of 30 to 40. By setting the ratio of both to a ratio including the ratio of obtaining the ortho composition (Li ₂ S: SiS ₂ = 66.7: 33.3) and the vicinity thereof, an increase in internal resistance during high temperature use can be further suppressed. It is. Incidentally, the raw material composition is, when containing Li ₂ S and GeS _2, proportion and the like of Li ₂ S and GeS ₂ are preferably the same as the ratio or the like of Li ₂ S and SiS ₂ described above.

Further, Li 2 _S used in the raw material composition is preferably less impurities. This is because side reactions can be suppressed. Examples of the method for synthesizing Li ₂ S include the method described in JP-A-7-330312. Furthermore, Li ₂ S is preferably purified using the method described in WO2005 / 040039. In addition to Li ₂ S and Group 13 to Group 15 element sulfides, the raw material composition includes Li ₃ PO ₄ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , Li ₃ BO _3, and Li ₃ BO _3. It may contain at least one kind of lithium orthooxo acid selected from the group consisting of ₃ AlO ₃ . By adding such a lithium orthooxo acid, a more stable sulfide solid electrolyte material can be obtained.

In addition, the sulfide solid electrolyte material having substantially no crosslinking sulfur may be sulfide glass or crystallized sulfide glass. Since sulfide glass is softer than crystallized sulfide glass, it can be considered that the expansion and contraction of the active material can be absorbed when an all-solid battery is produced, and the cycle characteristics are excellent. On the other hand, crystallized sulfide glass may have higher Li ion conductivity than sulfide glass. The sulfide glass can be obtained, for example, by performing the above-described amorphization treatment on the raw material composition. On the other hand, crystallized sulfide glass can be obtained, for example, by heat-treating sulfide glass. That is, crystallized sulfide glass can be obtained by sequentially performing an amorphization process and a heat treatment on the raw material composition. Depending on the heat treatment conditions, bridging sulfur and Li ₂ S may be generated or a stable phase may be generated. Therefore, in the present invention, the heat treatment temperature and the heat treatment time are adjusted so that they are not formed. It is preferable to do. In particular, the crystallized sulfide glass in the present invention preferably has no stable phase.

  The temperature of the heat treatment is, for example, preferably 270 ° C. or higher, more preferably 280 ° C. or higher, and further preferably 285 ° C. or higher. On the other hand, the temperature of the heat treatment is preferably, for example, 310 ° C. or less, more preferably 300 ° C. or less, and further preferably 295 ° C. or less. The heat treatment time is, for example, in the range of 1 minute to 2 hours, and more preferably in the range of 30 minutes to 1 hour. In the present invention, first, the temperature is raised from room temperature, then, heat treatment is performed within the above-described temperature and time range, and finally, the temperature is lowered to room temperature. That is, the heat treatment time in the present invention is usually a holding time that does not include the temperature raising time and the temperature lowering time. Examples of the method for performing heat treatment include a method using a baking furnace, a method using a drying furnace during film formation, and a method using a hot roll press.

Moreover, it is preferable that the sulfide solid electrolyte material which does not have bridge | crosslinking sulfur substantially has a high value of Li ion conductivity. The Li ion conductivity at room temperature is, for example, preferably 10 ⁻⁵ S / cm or more, and more preferably 10 ⁻⁴ S / cm or more. Further, examples of the shape of the sulfide solid electrolyte material include particles, and among them, a spherical shape or an oval shape is preferable. Moreover, when the said sulfide solid electrolyte material is a particulate form, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example.

(Ii) Solid Electrolyte Layer As described above, the solid electrolyte layer in the present invention preferably contains a sulfide solid electrolyte material substantially free of cross-linked sulfur, and the content thereof is preferably large. This is because a battery having a smaller internal resistance when used at high temperatures can be obtained. The ratio of the sulfide solid electrolyte material contained in the solid electrolyte layer is, for example, preferably in the range of 10% to 100% by volume, and more preferably in the range of 50% to 100% by volume. In particular, in the present invention, it is preferable that the solid electrolyte layer is composed only of the sulfide solid electrolyte material. In addition, the solid electrolyte layer in the present invention may contain a solid electrolyte material other than a sulfide solid electrolyte material that substantially does not have cross-linked sulfur, and contains a binder that imparts flexibility. Also good. The thickness of the solid electrolyte layer is preferably in the range of, for example, 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm. Examples of the method for forming the solid electrolyte layer include a method for compression molding a solid electrolyte material.

(2) Positive electrode active material layer Next, the positive electrode active material layer in this invention is demonstrated. The positive electrode active material 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. In particular, in the present invention, it is preferable that the solid electrolyte material contained in the positive electrode active material layer is a sulfide solid electrolyte material substantially free from cross-linked sulfur. This is because a battery having a low internal resistance when used at a high temperature can be obtained. The ratio of the sulfide solid electrolyte material contained in the positive electrode active material layer varies depending on the type of the all-solid-state battery. For example, it is in the range of 0.1% by volume to 80% by volume, particularly 1% by volume to 60% by volume. It is preferable that it exists in the range of 10 volume%-50 volume% especially.

In addition, the positive electrode active material in the present invention is not particularly limited, and examples thereof include an oxide positive electrode active material. By using an oxide positive electrode active material, an all-solid battery with high energy density can be obtained. For example, as an oxide positive electrode active material used for an all solid lithium battery, a general formula Li _x M _y O _z (M is a transition metal element, x = 0.02 to 2.2, y = 1 to 2, The positive electrode active material represented by z = 1.4-4) can be mentioned. In the above general formula, M is preferably at least one selected from the group consisting of Co, Mn, Ni, V, Fe and Si, and is at least one selected from the group consisting of Co, Ni and Mn. It is more preferable. As such an oxide positive electrode active material, specifically, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li ( _{Ni 0.5 Mn 1.5) O 4,} Li 2 FeSiO 4, Li 2 MnSiO 4 , and the like. In addition, examples of the oxide positive electrode active material other than the above general formula Li _x M _y O _z include olivine-type positive electrode active materials such as LiFePO ₄ and LiMnPO ₄ .

  Examples of the shape of the positive electrode active material include particles, and among them, a spherical shape or an elliptical shape is preferable. Moreover, when a positive electrode active material is a particulate form, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example. In addition, the content of the positive electrode active material in the positive electrode active material layer is preferably in the range of 10% by volume to 90% by volume, for example, and more preferably in the range of 30% by volume to 70% by volume.

  The positive electrode active material layer in the present invention may further contain a conductive material. By adding a conductive material, the conductivity of the positive electrode active material layer can be improved. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Moreover, the positive electrode active material layer in the present invention may further contain a binder. By adding a binder, flexibility can be imparted to the positive electrode active material layer. Examples of the binder include fluorine-containing resins. Moreover, although the thickness of a positive electrode active material layer changes with kinds of the target all-solid-state battery, it exists in the range of 1 micrometer-200 micrometers, for example.

(3) Negative electrode active material layer Next, the negative electrode active material layer in this invention is demonstrated. The negative electrode active material 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. In particular, in the present invention, it is preferable that the solid electrolyte material contained in the negative electrode active material layer is a sulfide solid electrolyte material substantially free from cross-linked sulfur. This is because a battery having a low internal resistance when used at a high temperature can be obtained. The ratio of the sulfide solid electrolyte material contained in the negative electrode active material layer varies depending on the type of the all-solid-state battery. For example, it is in the range of 0.1% by volume to 80% by volume, and in particular, 1% by volume to 60% by volume. It is preferable that it exists in the range of 10 volume%-50 volume% especially.

  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 shape of the negative electrode active material may be a foil shape or a particulate shape. When the shape of the negative electrode active material is particulate, the average particle size is preferably in the range of 0.1 μm to 50 μm, for example. Further, the content of the negative electrode active material in the negative electrode active material layer is, for example, preferably in the range of 10% by volume to 90% by volume, and more preferably in the range of 30% by volume to 70% by volume. Note that the solid electrolyte material, the conductive material, and the binder used for the negative electrode active material layer are the same as those in the positive electrode active material layer described above. Moreover, although the thickness of a negative electrode active material layer changes with kinds of the target all-solid-state battery, it exists in the range of 1 micrometer-200 micrometers, for example.

(4) Other configurations The all-solid battery in the present invention has at least the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer 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. Among them, SUS is preferable. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Of these, SUS is preferable. 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 of a general all-solid-state battery can be used for the battery case used for this invention. Examples of the battery case include a SUS battery case. Further, the all solid state battery of the present invention may be one in which the power generating element is formed inside the insulating ring.

(5) All-solid battery Examples of the all-solid battery in the present invention include an all-solid lithium battery, an all-solid sodium battery, an all-solid magnesium battery, and an all-solid calcium battery. An all solid sodium battery is preferred, and an all solid lithium battery is particularly preferred. Further, the all solid state battery in the present invention may be a primary battery or a secondary battery, and 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. Examples of the shape of the all solid state battery in the present invention include a coin type, a laminate type, a cylindrical type, and a square type. Among them, a square type and a laminate type are preferable, and a laminate type is particularly preferable.

  The method for producing an all-solid battery in the present invention is not particularly limited as long as it is a method capable of obtaining the above-described all-solid battery, and a method similar to a method for producing a general all-solid battery may be used. it can. As an example of a method for producing an all-solid-state battery, a power generation element is manufactured by sequentially pressing a material constituting the positive electrode active material layer, a material constituting the solid electrolyte layer, and a material constituting the negative electrode active material layer, A method of storing the power generation element in the battery case and caulking the battery case can be exemplified.

  Moreover, in this invention, the usage method of the all-solid-state battery mentioned above can be provided. Specifically, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer 40. A method for using an all solid state battery, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains a sulfide solid electrolyte material substantially free of cross-linked sulfur, It is possible to provide a method for using an all-solid battery, which is characterized by operating at a temperature of 0 ° C. or higher.

2. Next, the heating means in the present invention will be described. The heating means in the present invention is means for heating the all solid state battery to 40 ° C. or higher. In the present invention, it is preferable that the all solid state battery is heated to 60 ° C. or higher. This is because if the temperature is too low, the internal resistance may not be sufficiently suppressed. On the other hand, in the present invention, the all solid state battery is preferably heated to 500 ° C. or lower, more preferably 360 ° C. or lower. When the temperature is too high, it is preferable from the viewpoint of Li ion conductivity, but the deterioration of the solid electrolyte material becomes remarkable.

  The heating means in the present invention is not particularly limited as long as it can heat the all solid state battery. As an example of the heating means, a method using a heating element can be mentioned. The installation position of the heating element may be outside or inside the battery case of the all solid state battery. When the heating element is installed outside the battery case, it is possible to prevent the heating element from being deteriorated by the electrode reaction and to obtain an all-solid battery system with excellent durability, compared to the case where the heating element is installed inside. It has the advantage of being able to. On the other hand, when the heating element is installed inside the battery case, there is an advantage that the all solid state battery can be efficiently heated.

  When the heating element is installed outside the battery case, the heating element 11 may be disposed so as to contact the outer surface of the battery case 4 as shown in FIG. As shown in FIG. 2, the heating element 11 may be arranged with a predetermined interval between the outer surface of the battery case 4. The former has the advantage that the battery case can be efficiently heated, and the latter has the advantage that the design of the heating element is reduced and the design is easy. Furthermore, when the heating element is disposed so as to contact the outer surface of the battery case, the heating element may cover the entire surface of the battery case or may cover a part of the battery case. On the other hand, when the heating element is arranged with a predetermined gap between the outer surface of the battery case, the heating element may be arranged so as to surround the entire surface of the battery case. You may arrange | position so that it can heat.

  When the heating element is installed inside the battery case, the installation position of the heating element is not particularly limited. For example, as shown in FIG. Can be mentioned. Further, in this case, a protective layer (not shown) for preventing the heating element 11 from being deteriorated is formed on the surface where the heating element 11 is in contact with the positive electrode active material layer 1, the negative electrode active material layer 2 and the solid electrolyte layer 3. May be.

  As an example of the heating element in the present invention, one that generates heat by electric resistance can be cited. Specific examples include metal heating elements such as iron-chromium-aluminum heating elements and nickel-chromium heating elements. As another example of the heating element in the present invention, one that generates heat by flowing a heated gas or liquid into the inside of the cylindrical member can be exemplified. In particular, when the all-solid battery system of the present invention is used for in-vehicle use, examples of methods for heating the all-solid battery include a method using a heating element such as an internal combustion engine, a method of flowing exhaust gas inside a cylindrical member, and the like. be able to.

  On the other hand, other examples of the heating means in the present invention include means for irradiating microwaves.

  Moreover, the heating means in this invention may have a temperature detection part which detects the temperature of an all-solid-state battery, and a control part which controls the temperature of a heat generating body as needed.

3. All-solid-state battery system The all-solid-state battery system of this invention will not be specifically limited if it has the all-solid-state battery and heating means which were mentioned above. Among these, the all solid state battery system of the present invention is preferably operated at a high current density. Current density during operation, for example in the range of ^{0.1mA / cm 2 ~1000mA / cm 2} , preferably in the range Of these the ^{1mA / cm 2 ~100mA / cm 2} . Moreover, in the usage method of the all-solid-state battery mentioned above, it is preferable to operate | move with the current density of the said range.

  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]
(Synthesis of sulfide solid electrolyte material without bridging sulfur)
As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were used. These powders were weighed in a glove box under an argon atmosphere so that Li ₂ S: P ₂ S ₅ = 75: 25 (molar ratio) and mixed in an agate mortar to obtain a raw material composition. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill and mechanical milling was performed at a rotation speed of 370 rpm for 40 hours. This gave sulfide solid electrolyte material _{(75Li 2 S · 25P 2 S} 5 glass).

When the obtained sulfide solid electrolyte material was measured by Raman spectroscopy, a peak of PS ₄ unit (417 cm ⁻¹ peak) having no bridging sulfur was observed, and a peak of P ₂ S ₇ unit having bridging sulfur (402 cm). ^-1 peak) was not confirmed. Therefore, it was confirmed that a sulfide solid electrolyte material having no crosslinking sulfur was obtained.

(Preparation of all-solid lithium secondary battery)
Using the obtained sulfide solid electrolyte material (75Li ₂ S · 25P ₂ S ₅ glass), an all-solid lithium secondary battery was produced under an inert atmosphere. First, a power generation element A as shown in FIG. 3 was produced using a press. Here, as a material constituting the positive electrode active material layer 1, a positive electrode mixture having LiCoO ₂ (8.9 mg) and 75Li ₂ S · 25P ₂ S ₅ glass (3.8 mg) was used. Further, as a material constituting the negative electrode active material layer 2, a negative electrode mixture having graphite (4.71 mg) and 75Li ₂ S.25P ₂ S ₅ glass (4.71 mg) was used. Further, 75Li ₂ S · 25P ₂ S ₅ glass (51 mg) was used as a material constituting the solid electrolyte layer 3.

Using these materials, first, the solid electrolyte layer 3 is formed by pressing at a pressure of 1 ton / cm ² , and then a positive electrode mixture is added to one surface of the obtained solid electrolyte layer 3. The positive electrode active material layer 1 is formed by pressing at a pressure of 1 ton / cm ^2. Finally, the negative electrode mixture is added to the other surface of the solid electrolyte layer 3, and the pressure is 4.3 ton / cm ² . The negative electrode active material layer 2 was formed by pressing. Thereby, the electric power generation element A was obtained. Then, using this power generation element A, an all-solid lithium secondary battery was obtained.

[Comparative Example 1]
As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were used. These powders were weighed in a glove box under an argon atmosphere so that Li ₂ S: P ₂ S ₅ = 70: 30 (molar ratio) and mixed in an agate mortar to obtain a raw material composition. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill and mechanical milling was performed at a rotation speed of 370 rpm for 40 hours. Thereafter, heat treatment is performed at 290 ° C. for 1 hour in an argon atmosphere to obtain a sulfide solid electrolyte material (70Li ₂ S.30P ₂ S ₅ crystallized glass (also referred to as Li ₇ P ₃ S ₁₁ crystallized glass)). It was.

When the obtained sulfide solid electrolyte material was measured by Raman spectroscopy, a peak of P ₂ S ₇ unit having bridging sulfur (peak of 402 cm ⁻¹ ) was confirmed. Therefore, it was confirmed that a sulfide solid electrolyte material having bridging sulfur was obtained. Further, an all solid lithium secondary battery was obtained in the same manner as in Example 1 except that the obtained sulfide solid electrolyte material was used.

[Evaluation 1]
(Charge / discharge evaluation)
Using the all-solid lithium secondary battery obtained in Example 1 and Comparative Example 1, charge / discharge evaluation was performed. In the charge / discharge evaluation, first, CV charge was performed at 0.1 C to 3.96 V, and then the internal resistance (initial internal resistance) of the battery was determined by impedance measurement using a solartron at a voltage of 5 mV. Thereafter, charging / discharging was repeated at 0.1 C between 4.1 V and 3 V, and every 10 cycles, the battery was charged to 3.96 V and the internal resistance of the battery was determined by impedance measurement. Moreover, the operating temperature at the time of charging / discharging was 60 degreeC, and the restraint pressure at the time of charging / discharging was 1 ton / cm < ² >. The result is shown in FIG.

  FIG. 4 shows the rate of increase in internal resistance at the 10th, 20th, and 30th cycles. The internal resistance increase rate in each cycle is an increase rate with respect to the initial internal resistance. As shown in FIG. 4, it was confirmed that, in charging / discharging at 60 ° C., the all solid lithium secondary battery of Example 1 can suppress the increase in internal resistance more than the all solid lithium secondary battery of Comparative Example 1. It was.

  FIG. 5 shows the relationship between the operating temperature and the internal resistance of the all solid lithium secondary battery obtained in Example 1. The value of the internal resistance is a comparison of the initial internal resistance at 60 ° C. and 25 ° C. As a result, the value of the internal resistance was 132Ω at an operating temperature of 25 ° C., and 30Ω at an operating temperature of 60 ° C. Thus, it was confirmed that the internal resistance of the battery can be suppressed by increasing the operating temperature.

(Raman spectroscopy measurement)
After charging and discharging for 30 cycles as described above, the positive electrode mixture of the all-solid lithium secondary battery obtained in Example 1 and Comparative Example 1 was taken out, and microscopic Raman measurement was performed. An Ar laser (488 nm) was used for the measurement, and the output was 6.0 mW. For reference, micro Raman measurement was also performed on the positive electrode mixture before charging and discharging. The results are shown in FIGS. As shown in FIG. 6, the positive electrode mixture before charging / discharging of Example 1 has a PS ₄ unit peak (417 cm ⁻¹ peak), and the positive electrode mixture after charging / discharging of Example 1 is the same. It had a peak. From this, even after charge and discharge, it was confirmed that the PS ₄ unit of the sulfide solid electrolyte material was not changed and the sulfide solid electrolyte material was not chemically deteriorated.

On the other hand, as shown in FIG. 7, the positive electrode mixture before charging / discharging of Comparative Example 1 had a peak of P ₂ S ₇ unit (peak of 402 cm ⁻¹ ) having crosslinked sulfur. On the other hand, in the positive electrode mixture after charging and discharging in Comparative Example 1, the peak of P ₂ S ₇ unit disappeared and the peak of P ₂ S ₆ unit (peak of 380 cm ⁻¹ ) was generated. From this, when the sulfide solid electrolyte material having bridging sulfur is used as in Comparative Example 1, the P ₂ S ₇ unit becomes a low Li ion conductive P ₂ S ₆ unit in charge / discharge at 60 ° C. As a result, the rate of increase in internal resistance is thought to have increased as shown in FIG. On the other hand, when a sulfide solid electrolyte material having no bridging sulfur is used as in the present invention, the P ₂ S ₇ unit is not decomposed, so that the internal resistance increase rate can be reduced. .

[Example 2]
As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were used. These powders were weighed in a glove box under an argon atmosphere so that Li ₂ S: P ₂ S ₅ = 75: 25 (molar ratio) and mixed in an agate mortar to obtain a raw material composition. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill and mechanical milling was performed at a rotation speed of 370 rpm for 40 hours. Then, in an argon atmosphere for 1 hour by a heat treatment at 290 ° C., to obtain a sulfide solid electrolyte material _{(75Li 2 S · 25P 2 S} 5 crystallized glass).

Then, LiCoO ₂ (8.9 mg) and 75Li ₂ S · 25P ₂ S ₅ crystallized glass (3.8 mg) were mixed to obtain a positive electrode mixture. The positive electrode mixture was subjected to a storage test for 30 days at 60 ° C. The storage test was performed in an argon atmosphere.

[Example 3]
As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were used. These powders were weighed in a glove box under an argon atmosphere so that Li ₂ S: P ₂ S ₅ = 80: 20 (molar ratio) and mixed in an agate mortar to obtain a raw material composition. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill and mechanical milling was performed at a rotation speed of 370 rpm for 40 hours. This gave sulfide solid electrolyte material _{(80Li 2 S · 20P 2 S} 5 glass).

Thereafter, LiCoO ₂ (8.9 mg) and 80Li ₂ S.20P ₂ S ₅ glass (3.8 mg) were mixed to obtain a positive electrode mixture. The positive electrode mixture was subjected to a storage test for 30 days at 60 ° C. The storage test was performed in an argon atmosphere.

[Evaluation 2]
(Raman spectroscopy measurement)
Positive electrode mixture after storage test obtained in Example 2, 75Li ₂ S · 25P ₂ S ₅ crystallized glass before preparation of composite material in Example 2, positive electrode mixture after storage test obtained in Example 3 For the 80Li ₂ S · 20P ₂ S ₅ glass before preparation of the composite material in Example 3, a Raman spectrum was measured under the same conditions as in Evaluation 1 described above. The results are shown in FIGS. As shown in FIG. 8, the 75Li ₂ S · 25P ₂ S ₅ crystallized glass before preparation of the composite material in Example 2 has a peak of PS ₄ units (peak of 417 cm ⁻¹ ) and is obtained in Example 2. The obtained positive electrode mixture after the storage test had the same peak. From this, it was confirmed that even when a storage test at 60 ° C. for 30 days was performed, the PS ₄ unit of the sulfide solid electrolyte material did not change and the sulfide solid electrolyte material did not chemically deteriorate. Further, as shown in FIG. 9, the 80Li ₂ S · 20P ₂ S ₅ glass before preparation of the composite material in Example 2 has a peak of PS ₄ units (417 cm ⁻¹ peak), and is obtained in Example 3. The obtained positive electrode mixture after the storage test had the same peak. From this, it was confirmed that even when a storage test at 60 ° C. for 30 days was performed, the PS ₄ unit of the sulfide solid electrolyte material did not change and the sulfide solid electrolyte material did not chemically deteriorate.

[Reference Examples 1-1 to 1-6]
As starting materials, lithium sulfide (Li ₂ S) and phosphorus pentasulfide (P ₂ S ₅ ) were used. In a glove box under an argon atmosphere, these powders were weighed so as to have a molar ratio of x = 50 in the composition of xLi ₂ S · (100-x) P ₂ S ₅ and mixed in an agate mortar. A composition was obtained. Next, 1 g of the obtained raw material composition was put into a 45 ml zirconia pot, and zirconia balls (Φ10 mm, 10 pieces) were put into it, and the pot was completely sealed. This pot was attached to a planetary ball mill, and mechanical milling was performed at a rotational speed of 370 rpm for 40 hours to obtain a sulfide solid electrolyte material (Reference Example 1-1). Further, in the composition of xLi ₂ S · (100−x) P ₂ S ₅ , except that the value of x was changed to x = 66.7, 70, 75, 80, 100, Reference Example 1- In the same manner as in Example 1, sulfide solid electrolyte materials were obtained (Reference Examples 1-2 to 1-6).

Raman spectroscopic measurement was performed using the sulfide solid electrolyte material obtained in Reference Examples 1-1 to 1-5. The result is shown in FIG. As shown in FIG. 10, in Reference Example 1-1 (x = 50) and Reference Example 1-2 (x = 66.7), a peak of P ₂ S ₇ unit (peak near 402 cm ⁻¹ ) was confirmed. It was done. On the other hand, in Reference Examples 1-3 to 1-5 (x = 70, 75, 80, respectively), the peak of P ₂ S ₇ unit was not confirmed, but the peak of PS ₄ unit (peak around 417 cm ^−1). ) Was confirmed. Thereby, it was confirmed that the sulfide solid electrolyte material obtained in Reference Examples 1-3 to 1-5 has substantially no cross-linking sulfur.

Moreover, X-ray diffraction measurement was performed using the sulfide solid electrolyte material obtained in Reference Examples 1-1, 1-3, 1-4, and 1-6. The result is shown in FIG. As shown in FIG. 11, the peak of Li ₂ S was confirmed in Reference Example 1-6 (x = 100), but in Reference Examples 1-1 and 1-3 and Reference Example 1-4, Li ₂ No S peak was observed. This confirmed that the sulfide solid electrolyte materials obtained in Reference Examples 1-1 and 1-3 and Comparative Example 1-4 did not substantially contain Li ₂ S.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Solid electrolyte layer 10 ... All-solid-state battery 11 ... Heating body 12 ... Temperature detection part 13 ... Control part 20 ... All-solid-state battery system

Claims (6)

An all-solid battery having a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer; And a heating means for heating the all solid state battery to 40 ° C. or higher,
At least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains a particulate sulfide solid electrolyte material substantially free of cross-linked sulfur and Li ₂ S. Solid battery system.   2. The all solid state battery system according to claim 1, wherein the heating means is means for heating the all solid state battery to 60 [deg.] C. or more. The sulfide solid electrolyte material is a Li ₂ S—P ₂ S ₅ material, a Li ₂ S—SiS ₂ material, a Li ₂ S—GeS ₂ material, or a Li ₂ S—Al ₂ S ₃ material. The all-solid-state battery system of Claim 1 or Claim 2. The sulfide solid electrolyte material, all-solid-state cell system according to any one of claims of claims 1 to 3, characterized in that the Li 2 _{S-P 2} S ₅ material.   The all-solid-state battery stem according to any one of claims 1 to 4, wherein the sulfide solid electrolyte material is sulfide glass or crystallized sulfide glass.   The all-solid-state battery system according to any one of claims 1 to 5, wherein the positive electrode active material is an oxide positive electrode active material.

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