JP2022046077A - Battery system and battery cooling method - Google Patents

Abstract

To provide a battery system and a battery cooling method, capable of suppressing generation of hydrogen sulfide.SOLUTION: A battery system comprises: a secondary battery 2 including a cathode containing cathode active material, a solid electrolyte, and an anode containing anode active material, the cathode and/or the solid electrolyte made from sulfur-based material; and a controller 4 for controlling a cooler including a heat release plate 7. The controller 4 predicts or detects generation of hydrogen sulfide at the secondary battery 2 and, when generation of hydrogen sulfide at the secondary battery 2 is predicted or detected, cools the secondary battery 2 using the cooler.SELECTED DRAWING: Figure 1

Description

The present invention relates to a battery system for a secondary battery and a method for cooling the secondary battery.

Conventionally, a solid-state battery that prevents hydrogen sulfide gas from being generated in an emergency when the battery case is significantly damaged has been known (for example, Patent Document 1). The solid-state battery described in Patent Document 1 includes a power generation element in which a positive electrode layer, a sulfide-based solid electrolyte film, and a negative electrode layer are laminated in this order, a closed-type battery case for accommodating the power-generating element, and the closed-type battery case. It has a fluidity encapsulant which is immersed in the power generation element and has a property of not reacting with the sulfide-based solid electrolyte membrane, and when the hermetically sealed battery case is damaged, the fluidity encapsulant is used. It has a solidifying means for solidifying. When the sealed battery case is damaged, the liquid paraffin, which is a fluid sealant, solidifies, so that the sulfide-based solid electrolyte membrane does not come into contact with the moisture in the atmosphere, and the generation of hydrogen sulfide gas is prevented. do.

Japanese Unexamined Patent Publication No. 2009-193729

However, the above-mentioned conventional solid-state battery has a problem that the generation of hydrogen sulfide gas cannot be prevented unless the battery case is significantly damaged in an emergency.

An object to be solved by the present invention is to provide a battery system and a battery cooling method capable of suppressing the generation of hydrogen sulfide, not only in an emergency when the battery case is significantly damaged.

The present invention predicts or detects the generation of hydrogen sulfide in a secondary battery using a sulfur-based material for the positive electrode and / or the solid electrolyte, and when the generation of hydrogen sulfide is predicted or detected, the cooler is used. The above problem is solved by cooling the next battery.

According to the present invention, the generation of hydrogen sulfide can be suppressed.

FIG. 1 is a block diagram showing a battery system of a secondary battery according to the present embodiment. FIG. 2 is a plan view of the secondary battery according to the present embodiment. FIG. 3 is a cross-sectional view of the secondary battery along the line III-III of FIG. FIG. 4 is a conceptual diagram for explaining the transition from the time when the hydrogen sulfide reaction occurs in the sulfur-based material to the time when the generation of hydrogen sulfide stops. FIG. 5 is a flowchart showing the procedure of the cooling method of the secondary battery. FIG. 6 is a flowchart showing a procedure of a method for cooling a secondary battery according to a modified example of the present embodiment. FIG. 7 is a flowchart showing a procedure of a method for cooling a secondary battery according to a modified example of the present embodiment. FIG. 8 is a diagram for explaining the evaluation results of the examples, and is a graph showing the results of surface analysis by X-ray photoelectron spectroscopy (XPS). FIG. 9 is a diagram for explaining the evaluation results of the examples, and is a graph showing the results of surface analysis by X-ray photoelectron spectroscopy (XPS). FIG. 10 is a diagram for explaining the evaluation results of the examples, and is a graph showing the results of surface analysis by X-ray photoelectron spectroscopy (XPS). FIG. 11 is a diagram for explaining the evaluation results of the examples, and is a graph showing the results of surface analysis by X-ray photoelectron spectroscopy (XPS). FIG. 12 is a diagram for explaining the evaluation results of the examples, and is a graph showing the results of quantitative analysis by gas chromatography.

FIG. 1 is a diagram showing a battery system for cooling a secondary battery using a sulfur-based material according to the present embodiment. The battery system according to the present embodiment predicts or detects the generation of hydrogen sulfide in the secondary battery, and when the generation of hydrogen sulfide is predicted or detected, the secondary battery is cooled to suppress the generation of hydrogen sulfide. do. As shown in FIG. 1, the battery system includes a battery case 1, a secondary battery 2, a sensor 3, a controller 4, an on-off valve 5, a pipe 6, and a heat transfer plate 7.

The battery case 1 is a metal case and houses a secondary battery 2, a sensor 3, a part of a pipe 6, and a heat transfer plate 7.

An all-solid-state lithium-ion secondary battery will be described as an example of the secondary battery 2 in the present embodiment. The secondary battery 2 includes a positive electrode including a positive electrode active material layer containing a positive electrode active material capable of storing and releasing lithium ions, and a negative electrode including a negative electrode active material layer containing a negative electrode active material capable of storing and releasing lithium ions. It comprises a power generation element having a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer. In addition to the power generation element, the secondary battery 2 has an electrode tab, an electrode tab, and an exterior member accommodating the power generation element. Further, the secondary battery 2 is a battery using at least a sulfur-based material, and contains a sulfur component as a material for a positive electrode and / or a material for a solid electrolyte. The detailed structure and material of the secondary battery will be described later.

The sensor 3 is provided in the battery case 1 and is a sensor for detecting the state of the secondary battery 2. The sensor 3 detects the pressure in the battery case 1 and / or the gas concentration generated in the battery case 1, and the sensor 3 includes, for example, a hydrogen sulfide concentration meter, an acceleration sensor, and a pressure sensor. used. When a sulfur-based material is used for the secondary battery 2, hydrogen sulfide is generated when sulfur reacts with water. When hydrogen sulfide is generated in the battery case 1 for some reason, the concentration of hydrogen sulfide in the battery case 1 and the pressure in the battery case 1 change. Therefore, in the present embodiment, the state of the secondary battery 2 is detected by detecting the sulfur concentration and the internal pressure in the battery case 1 by using the sensor 3.

The controller 4 has a CPU, a memory, and the like. The controller 4 is a control device that predicts or detects the generation of hydrogen sulfide in the secondary battery 2 based on the detected value of the sensor 3. Further, the controller 4 controls the on-off valve 5 to adjust the flow rate of the refrigerant flowing through the pipe 6, thereby cooling the secondary battery 2 via the heat transfer plate 7. That is, the controller 4 controls the cooler composed of the on-off valve 5, the pipe 6, the heat transfer plate 7, and the like.

The on-off valve 5 is provided in the pipe 6 and adjusts the flow rate of the refrigerant flowing in the pipe 6. The pipe 6 is a flow path for circulating the refrigerant, and is configured so that the refrigerant enters and exits inside and outside the case 1. Cooling water, air, cooling gas and the like are used as the refrigerant. The heat transfer plate 7 is a member for transferring the heat of the secondary battery 2 to the refrigerant flowing through the pipe 6. As shown in FIG. 1, in the heat transfer plate 7, a plurality of plates are arranged so as to be parallel to each other on the main surfaces, and one end of each of the plurality of plates is connected to another plate serving as a bottom surface. .. The secondary batteries 2 are arranged between the plates arranged in parallel, that is, a plurality of plates constituting the heat transfer plate 7 and a plurality of secondary batteries 2 are laminated. The on-off valve 5, the pipe 6, and the heat transfer plate 7 are a part of the cooler, but the battery system according to the present embodiment includes a refrigerant pump, a heat exchanger, and the like as other configurations of the cooler. I have.

Next, the structure of the secondary battery (all-solid-state lithium ion secondary battery) 2 will be described with reference to FIGS. 2 and 3. FIG. 2 shows a plan view of the secondary battery 2 according to the present embodiment, and FIG. 3 shows a cross-sectional view of the secondary battery 2 along the line III-III of FIG. The structure of the secondary battery 2 is not limited to the structure shown in FIGS. 2 and 3, and may be another structure.

As shown in FIGS. 2 and 3, the secondary battery 2 is connected to a power generation element 101 having three positive electrode layers 102, seven electrolyte layers 103, and three negative electrode layers 104, and three positive electrode layers 102, respectively. A positive electrode tab 105, a negative electrode tab 106 connected to each of the three negative electrode layers 104, and an upper exterior member 107 and a lower exterior member 108 containing and sealing the power generation element 101, the positive electrode tab 105, and the negative electrode tab 106, respectively. It is composed of and.

The number of the positive electrode layer 102, the electrolyte layer 103, and the negative electrode layer 104 is not particularly limited, and one positive electrode layer 102, three electrolyte layers 103, and one negative electrode layer 104 may form the power generation element 101. Further, the number of the positive electrode layer 102, the electrolyte layer 103, and the negative electrode layer 104 may be appropriately selected, if necessary.

The positive electrode layer 102 constituting the power generation element 101 has a positive electrode side current collector 102a extending to the positive electrode tab 105 and a positive electrode active material layer formed on both main surfaces of a part of the positive electrode side current collector 102a. is doing. The positive electrode side current collector 102a constituting the positive electrode layer 102 may be made of, for example, an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper titanium foil, or a stainless steel foil. As the metal, nickel, iron, copper or the like may be used for the positive electrode side current collector 102a. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, and the like may be used.

A conductive resin may be used for the positive electrode side current collector 102a instead of the metal. The conductive resin can be composed of a non-conductive polymer material to which a conductive filler is added, if necessary. Examples of the non-conductive polymer material include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), etc., which have excellent potential resistance. Material is used. The conductive filler can be used without particular limitation as long as it is a conductive substance. For example, materials having excellent conductivity, potential resistance, or lithium ion blocking property include metals and conductive carbon. The metal is not particularly limited, and includes at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or at least one of these metals. Examples include alloys or metal oxides.

The positive electrode active material layer constituting the positive electrode layer 102 is not particularly limited, but is a layered rock salt type active material such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , Li (Ni—Mn—Co) O ₂ , LiMn ₂ . Examples include spinel-type active materials such as O ₄ , LiNi _0.5 Mn _1.5 O ₄ , olivine-type 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 . Be done. Examples of the oxide active material other than the above include Li ₄ Ti ₅ O ₁₂ . A composite oxide containing lithium and nickel is preferably used, and more preferably Li (Ni-Mn-Co) O ₂ and a part of these transition metals are substituted with other elements (hereinafter, simply ". Also referred to as "NMC composite oxide") is used. As described above, the NMC composite oxide also includes a composite oxide in which a part of the transition metal element is replaced with another metal element. Examples of other elements in that case include Ti, Zr, Nb, W, P and the like.

A sulfur-based positive electrode active material may be used for the positive electrode active material layer. Examples of the sulfur-based positive electrode active material include particles or thin films of an organic sulfur compound or an inorganic sulfur compound, and the oxidation-reduction reaction of sulfur can be used to release lithium ions during charging and occlude lithium ions during discharging. Any substance that can be produced will do. Examples of the organic sulfur compound include a disulfide compound and a sulfur-modified polyacrylonitrile. Examples of the inorganic sulfur compound include sulfur (S), S-carbon composite, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , Li ₂ S, MoS ₂ , MoS ₃ and the like.

A positive electrode active material other than the above may be used. Examples of the shape of the positive electrode active material include particulate (spherical and fibrous) and thin film. The content of the positive electrode active material in the positive electrode active material layer is not particularly limited. The positive electrode active material layer may further contain at least one of a solid electrolyte, a conductive auxiliary agent, and a binder, if necessary. Examples of the shape of the positive electrode active material include particulate (spherical and fibrous) and thin film. The content of the positive electrode active material in the positive electrode active material layer is not particularly limited. The positive electrode active material layer may further contain at least one of a solid electrolyte, a conductive auxiliary agent, and a binder, if necessary. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, and those exemplified as solid electrolytes that can form the electrolyte layer 103, which will be described later, can be used.

The conductive auxiliary agent is not particularly limited, but is preferably in the form of particles or fibers. When the conductive auxiliary agent is in the form of particles, the shape of the particles is not particularly limited, and may be any shape such as powder, sphere, rod, needle, plate, columnar, indefinite, fluffy, and spindle-shaped. It doesn't matter.

The average particle size (primary particle size) when the conductive auxiliary agent is in the form of particles is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of the electrical characteristics of the battery.

Binders include polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are replaced with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyethernitrile, and poly. Tetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene / butadiene rubber (SBR), ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and Thermoplastic polymers such as the hydrogenated product, styrene / isoprene / styrene block copolymer and the hydrogenated product; tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether co-weight. Fluororesin such as coalescence (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF); Vinylidene Fluoride-Hexafluoropropylene Fluororesin (VDF-HFP Fluororesin), Vinylidene Fluoride-Hexafluoropropylene-Tetrafluoroethylene Fluororesin (VDF-HFP-TFE Fluororesin), Vinylidene Fluoride-Pentafluoro Propylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene Examples thereof include vinylidene fluoride-based fluororubbers such as vinylidene fluoride-chlorotrifluoroethylene-based fluororubbers (VDF-CTFE-based fluororubbers); epoxy resins; and the like. Of these, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

Each of the positive electrode side current collectors 102a constituting these three positive electrode layers 102 is joined to the positive electrode tab 105. As the positive electrode tab 105, an aluminum foil, an aluminum alloy foil, a copper foil, a nickel foil, or the like can be used.

The negative electrode layer 104 constituting the power generation element 101 includes a negative electrode side current collector 104a extending to the negative electrode tab 106 and a negative electrode active material layer formed on both main surfaces of a part of the negative electrode side current collector 104a. have.

The negative electrode side current collector 104a of the negative electrode layer 104 is an electrochemically stable metal foil such as a nickel foil, a copper foil, a stainless steel foil, or an iron foil.

The negative electrode layer 104 is formed of a layer containing a negative electrode active material. The type of the negative electrode active material is not particularly limited, and examples thereof include a carbon material, a metal oxide, and a metal active material. Examples of the carbon material include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, soft carbon and the like. Examples of the metal oxide include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , SiO and the like. Further, examples of the metal active material include elemental metals such as In, Al, Si and Sn, and alloys such as TiSi and La ₃ Ni ₂ Sn ₇ .

Further, the negative electrode active material may be a metal containing Li, and such a negative electrode active material is not particularly limited as long as it is an active material containing Li, and may be a Li metal or a lithium alloy containing Li. .. The lithium alloy may be selected from, for example, lithium and at least gold (Au), magnesium (Mg), aluminum (Al), calcium (Ca), zinc (Zn), tin (Sn), and bismuth (Bi). Alloys with one type of metal can be mentioned. Further, the lithium alloy may be an alloy of lithium and two or more kinds of metals among the above-mentioned metals. Specific examples of the lithium alloy include, for example, a lithium-gold alloy (Li-Au), a lithium-magnesium alloy (Li-Mg), a lithium-aluminum alloy (Li-Al), a lithium-calcium alloy (Li-Ca), and the like. Examples thereof include a lithium-zinc alloy (Li-Zn), a lithium-tin alloy (Li-Sn), and a lithium-bismas alloy (Li-Bi).

The negative electrode active material layer may be any one containing a lithium alloy, and its composition is not particularly limited. For example, when a metal other than lithium constituting the lithium alloy is "Me", the following It can be any aspect of (1) to (3).
(1) A single layer made of only a lithium alloy (that is, a Li-Me layer)
(2) A layer provided with a layer made of lithium metal and a layer made of a lithium alloy (that is, a Li layer / Li-Me layer).
(3) A layer including a layer made of lithium metal, a layer made of a lithium alloy, and a layer made of a metal other than lithium (that is, Li layer / Li-Me layer / Me layer).
In the aspect of (2) above, it is desirable that the layer made of a lithium alloy (Li—Me layer) is a layer on the side of the electrolyte layer 103 (a layer forming an interface with the electrolyte layer 103), and the above (3). ), It is desirable that the layer made of a metal other than lithium (Me layer) is the layer on the side of the electrolyte layer 103 (the layer forming the interface with the electrolyte layer 103). In the case of a lithium metal layer containing a lithium metal and a layer containing a metal different from the lithium metal (intermediate layer), the intermediate layer is a layer between the lithium metal layer and the solid electrolyte, and is at least one of the lithium metals. It is desirable that a part and at least a part of the metal forming the intermediate layer are alloyed.

For example, the negative electrode includes the aspect (3) above, that is, a layer made of a lithium metal, a layer made of a lithium alloy, and a layer made of a metal other than lithium (that is, a Li layer / Li-Me layer /). In the case of forming a Me layer), a lithium metal and a metal other than lithium are laminated to alloy these interface portions, whereby a layer made of a lithium alloy can be formed at these interfaces. .. The method of laminating the lithium metal and the metal other than lithium is not particularly limited, but is made of a lithium metal by depositing a metal other than lithium on a layer made of the lithium metal by vacuum vapor deposition or the like. A method of alloying these interfaces while forming a layer made of a metal other than lithium on the layer can be mentioned. Alternatively, a lithium metal is vapor-deposited on a layer made of a metal other than lithium by vacuum deposition or the like, and these interfaces are alloyed while forming a layer made of a lithium metal on a layer made of a metal other than lithium. The method etc. can be mentioned.

In the secondary battery 2 of the present embodiment, the three negative electrode layers 104 are configured such that each negative electrode side current collector 104a constituting the negative electrode layer 104 is bonded to a single negative electrode tab 106. ing. That is, in the secondary battery 2 of the present embodiment, each negative electrode layer 104 is bonded to a single common negative electrode tab 106.

The electrolyte layer 103 of the power generation element 101 prevents a short circuit between the positive electrode layer 102 and the negative electrode layer 104 described above, contains a solid electrolyte as a main component, and comprises the positive electrode active material layer and the negative electrode active material layer described above. It is a layer that intervenes between them. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, and sulfide solid electrolytes are preferable.

Examples of the sulfide solid electrolyte include LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP 2 S 5, and Li 2 SP ₂ S ₅ . LiI-Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS ₄ , Li ₃ PS ₄ , Li ₆ PS ₅ Cl, Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -Li I, Li ₂ S -P ₂ S ₅ -Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ OLiI, 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 SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -ZmSn (where m and n are positive numbers and Z is one of Ge, Zn or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -LixMOy (where x and y are positive numbers and M is any of P, Si, Ge, B, Al, Ga and In) and the like. The description of "Li ₂ SP _{2 S 5" means a sulfide solid electrolyte using a raw material composition containing Li 2 S and P 2 S 5 , and} the same applies to other descriptions.

The sulfide solid electrolyte may have, for example, a Li ₃ PS ₄ skeleton, a Li ₄ P ₂ S ₇ skeleton, or a Li ₄ P ₂ S ₆ skeleton. .. Examples of the sulfide solid electrolyte having a Li ₃ PS ₄ skeleton include LiI-Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS ₄ , and Li ₃ PS ₄ . Examples of the sulfide solid electrolyte having a Li ₄ P ₂ S ₇ skeleton include a Li-PS-based solid electrolyte called LPS (for example, Li ₇ P ₃ S ₁₁ ). Further, as the sulfide solid electrolyte, for example, LGPS represented by Li _(4-x) Ge _(1-x) P _x S ₄ (x satisfies 0 <x <1) may be used. Among them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing a P element, and the sulfide solid electrolyte is more preferably a material containing Li ₂ SP ₂ S ₅ as a main component. Further, the sulfide solid electrolyte may contain halogen (F, Cl, Br, I).

When the sulfide solid electrolyte is a Li ₂ SP ₂ S ₅ system, the ratio of Li ₂ S and P ₂ S ₅ is Li ₂ S: P ₂ S ₅ = 50: 50 to 100 in terms of molar ratio. : 0 is preferable, and Li ₂ S: P ₂ S ₅ = 70: 30 to 80:20 is preferable. Further, the sulfide solid electrolyte 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. Further, the crystallized sulfide glass can be obtained, for example, by heat-treating the sulfide glass at a temperature equal to or higher than the crystallization temperature. The ionic conductivity (for example, Li ionic conductivity) of the sulfide solid electrolyte at room temperature (25 ° C.) is preferably 1 × 10 ^-5 S / cm or more, for example, 1 × 10 ^-4 S / cm. It is more preferably cm or more. The value of the ionic conductivity of the solid electrolyte can be measured by the AC impedance method.

Examples of the oxide solid electrolyte include compounds having a NASICON type structure and the like. As an example of a compound having a NASION type structure, a compound (LAGP) represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), a general formula Li _{1 + x} Al _x Ti ₂ Examples thereof include a compound (LATP) represented by _−x (PO ₄ ) ₃ (0 ≦ x ≦ 2). Further, as another example of the oxide solid electrolyte, LiLaTIO (for example, Li _0.34 La _0.5 1TiO ₃ ), LiPON (for example, Li _2.9 PO _3.3 N _0.46 ), LiLaZrO (for example, LiLaZrO). , Li ₇ La ₃ Zr ₂ O ₁₂ ) and the like.

The solid electrolyte layer 103 may further contain a binder in addition to the above-mentioned solid electrolyte. The binder is not particularly limited, but for example, the above-mentioned one can be used.

The content of the solid electrolyte is, for example, preferably in the range of 10 to 100% by mass, more preferably in the range of 50 to 100% by mass, and preferably in the range of 90 to 100% by mass. More preferred.

As described above, the positive electrode layer 102 used in the present embodiment uses a sulfur-based material by containing a sulfur compound as the positive electrode active material, and the electrolyte layer 103 contains a sulfide solid electrolyte as a main component. , Use sulfur material. The transitional material may be used for either one of the positive electrode layer 102 and the electrolyte layer 103.

Then, as shown in FIG. 3, the positive electrode layer 102 and the negative electrode layer 104 are alternately laminated via the electrolyte layer 103, and the electrolyte layer 103 is further laminated on the uppermost layer and the lowermost layer, respectively. As a result, the power generation element 101 is formed.

The power generation element 101 configured as described above is housed and sealed in the upper exterior member 107 and the lower exterior member 108. The upper exterior member 107 and the lower exterior member 108 for sealing the power generation element 101 are, for example, a resin obtained by laminating both sides of a resin film such as polyethylene or polypropylene or a metal foil such as aluminum with a resin such as polyethylene or polypropylene. -A state in which the positive electrode tab 105 and the negative electrode tab 106 are led out to the outside by heat-sealing the upper exterior member 107 and the lower exterior member 108, which are made of a flexible material such as a metal thin film laminate material. Then, the power generation element 101 is sealed.

The positive electrode tab 105 and the negative electrode tab 106 have a sealing film 109 at a portion in contact with the upper exterior member 107 and the lower exterior member 108 in order to ensure adhesion to the upper exterior member 107 and the lower exterior member 108. It is provided. The seal film 109 is not particularly limited, but can be made of, for example, polyethylene, modified polyethylene, polypropylene, modified polypropylene, or a synthetic resin material having excellent electrolytic solution resistance and heat fusion resistance such as ionomer.

As described above, the secondary battery used in this embodiment contains a sulfur-based material. Hydrogen sulfide is generated when sulfur and water react for some reason. Then, when hydrogen sulfide flows out of the secondary battery 2 (cell battery), there is a possibility of corroding the metal parts in the battery case 1. Therefore, when the generation of hydrogen sulfide is predicted or detected, it is required to suppress the generation of hydrogen sulfide.

According to the inventor's knowledge, the lower the cell temperature of the secondary battery 2, the smaller the amount of hydrogen sulfide generated. Hereinafter, the reason will be described with reference to FIG. FIG. 4 is a conceptual diagram for explaining the transition from the time when the hydrogen sulfide reaction occurs in the sulfur-based material to the time when the generation of hydrogen sulfide stops. In FIG. 4, (а) represents the transition of the reaction in the sulfur-based material at low temperature, and (b) represents the transition of the reaction in the sulfur-based material at high temperature.

When sulfur-based materials come into contact with moisture, hydrogen sulfide is generated. At the same time as such a hydrogen sulfide generation reaction, the lithium metal reacts with oxygen to form a lithium compound. The mode in which the lithium compound is formed depends on the cell temperature. As shown in FIG. 4 (а), when the cell temperature is low, the hydrogen sulfide generation reaction occurs in the surface layer portion of the sulfur-based material 41, so that the lithium compound 42 is formed in the surface layer portion of the sulfur-based material 41. Sulfur. Then, when the sulfur-based material 41 is covered with the lithium compound 42, the generation of hydrogen sulfide stops. At low temperatures, the hydrogen sulfide generation reaction does not proceed to the deep layer of the sulfur-based material 41 and is mainly formed on the surface layer, so that the formation of the lithium compound 42 proceeds uniformly on the surface layer, effectively producing hydrogen sulfide. The generation can be suppressed, and the amount of hydrogen sulfide generated can also be suppressed.

On the other hand, as shown in FIG. 4B, when the cell temperature is high, the hydrogen sulfide generation reaction proceeds to the deep part of the sulfur-based material 41. Therefore, the lithium compound 43 is formed not only in the surface layer portion of the sulfur-based material 41 but also in the deep layer portion. Then, when the sulfur-based material 41 is covered with the lithium compound 42, hydrogen sulfide generation stops. Since the hydrogen sulfide generation reaction proceeds to the deep layer at high temperature, the formation of the lithium compound 43 does not proceed uniformly as compared with the low temperature, and it takes time for the lithium compound 42 to cover the surface layer of the sulfur-based material 41. Therefore, the amount of hydrogen sulfide generated also increases. That is, when the generation of hydrogen sulfide in the secondary battery 2 is expected or detected, the generation of hydrogen sulfide can be suppressed by forcibly cooling the secondary battery 2.

Next, a method of detecting the generation of hydrogen sulfide in the present embodiment and cooling the secondary battery 2 will be described. FIG. 5 is a flowchart showing a control procedure of the controller 4. The controller 4 executes the control flow of FIG. 5 at the time of charging / discharging current of the secondary battery 2.

In step S1, the controller 4 detects the state of the secondary battery 2 by acquiring the detected value of the sensor 3. In step S2, the controller 4 detects the generation of hydrogen sulfide in the secondary battery 2 by comparing the detection value of the sensor 3 with the preset determination threshold value. The determination threshold value is a threshold value for determining that hydrogen sulfide is generated in the secondary battery 2. For example, when a hydrogen sulfide densitometer is used for the sensor 3, the determination threshold value is defined by the concentration of hydrogen sulfide. Then, when the detected value of the sensor 3 is less than the determination threshold value, the controller 4 determines that hydrogen sulfide is not generated in the secondary battery 2. Then, the control flow returns to step S1. The controller 4 repeatedly executes the control processes of steps S1 and S2 to detect the presence or absence of hydrogen sulfide generation during the use of the secondary battery 2.

When the detection value of the sensor 3 is equal to or higher than the determination threshold value, the controller 4 determines that hydrogen sulfide is generated in the secondary battery 2, and executes the control process of step S3. In step S3, the controller 4 opens the on-off valve 5 that stops the refrigerant circulation, operates the refrigerant pump (not shown), circulates the refrigerant, and starts cooling the secondary battery 2. The timing of starting cooling of the secondary battery 2 should be earlier than the time when the generation of hydrogen sulfide is detected, but the controller 4 starts from the time when the generation of hydrogen sulfide is detected in step S2. It is preferable to operate the refrigerant pump to start cooling the secondary battery 2 by 1 second.

In step S4, the controller 4 determines whether or not to finish cooling the secondary battery 22. For example, when the amount of hydrogen sulfide generated is detected from the detected value of the sensor and the amount of increase in hydrogen sulfide per predetermined time becomes less than the predetermined value, the controller 4 ends the cooling of the secondary battery 22. Alternatively, if the cooling time is preset, the controller 4 ends the cooling of the secondary battery 2 when the elapsed time from the start of cooling has elapsed. If the cooling of the secondary battery 22 is not completed, the controller 4 continues the cooling of the secondary battery 2. As described above, since the cooling of the secondary battery 2 is started immediately after the generation of hydrogen sulfide is detected, the formation of the lithium compound can be uniformly promoted on the surface layer portion of the transitional material, and the generation of hydrogen sulfide can be suppressed. ..

As described above, in the present embodiment, the generation of hydrogen sulfide is detected in the secondary battery 2 using the sulfur-based material for the positive electrode and / or the solid electrolyte, and when the generation of hydrogen sulfide is detected, the cooler is used. Cools the secondary battery. As a result, the cell temperature of the secondary battery 2 is lowered and the generation of hydrogen sulfide is suppressed, so that the amount of hydrogen sulfide generated can be suppressed.

Further, in the present embodiment, cooling of the secondary battery 2 is started by 1 second from the time when the generation of hydrogen sulfide is detected. Since a large amount of hydrogen sulfide is generated in the initial stage from the time of generation, the amount of hydrogen sulfide generated can be effectively reduced by starting cooling of the secondary battery 2 immediately after the generation of hydrogen sulfide is detected. ..

Further, in the present embodiment, when the generation of hydrogen sulfide is not detected, the cooling control of the secondary battery 2 by the cooler is not executed. Since the cell temperature of the secondary battery 2 tends to rise during charging, when the generation of hydrogen sulfide is detected, the cooling control of the secondary battery 2 is executed. As a result, the generation of hydrogen sulfide can be effectively suppressed.

As a modification of the present embodiment, the controller 4 may execute control for cooling the secondary battery 2 according to the cell temperature of the secondary battery 2. FIG. 6 is a flowchart showing a control procedure of the controller 4. In step S11, the controller 4 acquires the detected value of the sensor 3. In step S12, the controller 4 detects the presence or absence of hydrogen sulfide generation in the secondary battery 2. The control process of step S11 and step S12 is the same as the control process of step S1 and step S2, respectively.

In step S13, the controller 4 acquires the cell temperature of the secondary battery 2. The battery system in the modified example includes a temperature sensor that detects the cell temperature of the secondary battery 2, and the controller 4 acquires the cell temperature from the temperature sensor. In step S14, the controller 4 compares the cell temperature with the lower limit temperature. The lower limit temperature indicates the lower limit of the temperature of the secondary battery 2 that can be lowered by cooling the cooler. The lower limit temperature is a value determined by the cooling performance of the cooler, the environment such as the outside air temperature, etc., and is set in advance. That is, the cell temperature of the secondary battery can be lowered to the lower limit temperature by cooling with a cooler. The controller 4 may appropriately change the lower limit temperature according to the outside air temperature.

When the cell temperature is higher than the lower limit temperature, the cell temperature of the secondary battery 2 can be made lower than the current temperature. Therefore, in step S15, the controller 4 starts cooling the secondary battery 2. The control process in step S15 is the same as the control process in step S4 described above. In step S16, the controller 4 determines whether or not to finish cooling the secondary battery 22. For example, when the cell temperature of the secondary battery 2 reaches the lower limit temperature, the controller 4 finishes cooling the secondary battery 2.

When the cell temperature is below the lower limit temperature, the cooler cannot cool the secondary battery 2 so that it is lower than the current temperature, so the controller 4 controls without cooling by the cooler. End the flow. That is, in the modified example, the controller 4 determines whether or not the current secondary battery 2 is in a state where it can be cooled by the cooler based on the temperature of the secondary battery 2 and the cooling capacity of the cooler, and secondary. If the current cell temperature of the battery is at a temperature that cannot be cooled by the cooler, do not cool it.

In the modification of the present embodiment, the cell temperature of the secondary battery 2 is acquired, and when the cell temperature is higher than the lower limit temperature of the secondary battery 2 that can be lowered by cooling the cooler, the secondary battery 2 is used by the cooler. To cool. As a result, when the temperature of the secondary battery 2 cannot be lowered by the cooler, the cooler does not operate, so that wasteful power consumption can be suppressed.

Further, as another modification of the present embodiment, the battery system is a system in which one of the normal charge mode and the quick charge mode can be selected and the secondary battery 2 can be charged in the selected mode, and the controller 4 May be controlled so as not to charge in the quick charge mode when the generation of hydrogen sulfide is detected. FIG. 7 is a flowchart showing a control procedure of the controller 4. The battery system has a charging circuit for a normal charging mode and a charging circuit for a quick charging mode, and switches the charging circuit according to the selected charging mode. The quick charge mode is a mode for charging at a higher C rate than the normal charge mode. The charging mode is selected based on the user's operation command. The controller 4 selects one of the charging mode and the quick charging mode, and controls the charging of the secondary battery 2 so that the secondary battery 2 can be charged in the selected mode. The control flow shown in FIG. 7 is a control flow when charging the secondary battery 2 in the quick charge mode.

In step S21, the controller 4 selects the quick charge mode based on the user's operation command. In step S22, the controller 4 acquires the detected value of the sensor 3. In step S23, the controller 4 detects the presence or absence of hydrogen sulfide generation in the secondary battery 2. The control process of step S22 and step S23 is the same as the control process of step S1 and step S2, respectively.

If the generation of hydrogen sulfide is not detected, the controller 4 starts charging the secondary battery 2 in the quick charge mode in step S24. In step S25, the controller 4 calculates the current charge state (SOC) of the secondary battery 2 by current integration or the like while the secondary battery 2 is being charged, and charges the secondary battery 2 based on the calculated SOC. Judge whether to end. When the current SOC reaches the upper limit SOC indicating full charge, the controller 4 ends the charging of the secondary battery 2. That is, even when the quick charge mode is selected, if the generation of hydrogen sulfide is detected, the secondary battery 2 is not charged in the quick charge mode, and the secondary battery 2 is suppressed in order to suppress the generation of hydrogen sulfide. To cool.

When the generation of hydrogen sulfide is detected, the controller 4 starts cooling the secondary battery 2 in step S26. In step 27, the controller 4 determines whether or not to finish cooling the secondary battery 22. The control process of step 26 and step S27 is the same as the control process of step S3 and step S4, respectively.

If the generation of hydrogen sulfide is not detected, the controller 4 starts charging the secondary battery 2 in the quick charge mode in step S26. In step S27, the controller 4 calculates the current charge state (SOC) of the secondary battery 2 by current integration or the like while the secondary battery 2 is being charged, and charges the secondary battery 2 based on the calculated SOC. Judge whether to end. When the current SOC reaches the upper limit SOC indicating full charge, the controller 4 ends the charging of the secondary battery 2.

That is, in the modified example, the secondary battery 2 is charged in either the charging mode or the quick charging mode, and when the generation of hydrogen sulfide in the secondary battery 2 is detected, the secondary battery 2 is used in the quick charging mode. Do not charge battery 2. As a result, it is possible to prevent the temperature of the secondary battery 2 from rising due to rapid charging and suppress the amount of hydrogen sulfide generated.

In this embodiment, the controller 4 does not necessarily have to detect the generation of hydrogen sulfide, and may predict the generation of hydrogen sulfide. For example, the controller 4 predicts that hydrogen sulfide will be generated when a short circuit of the secondary battery 2 is detected. The short circuit of the secondary battery 2 may be detected from the current change during charging / discharging of the secondary battery 2 or the internal resistance of the secondary battery 2. Then, the controller 4 cools the secondary battery 2 when the generation of hydrogen sulfide is predicted. In the control process of step S1 and step S2 in the control flow shown in FIG. 5, the controller 4 detects the state of the secondary battery 2 from a current sensor, an impedance measuring device, or the like that detects the current of the secondary battery 2. By acquiring a value and determining whether or not a short circuit has occurred based on the acquired value, the presence or absence of hydrogen sulfide generation is predicted. Then, when it is determined that a short circuit has occurred, the controller 4 predicts that hydrogen sulfide will be generated in the secondary battery.

As described above, in the present embodiment, the generation of hydrogen sulfide in the secondary battery 2 is predicted, and when the generation of hydrogen sulfide is predicted, the secondary battery is cooled by the cooler. As a result, the cell temperature of the secondary battery 2 is lowered and the generation of hydrogen sulfide is suppressed, so that the amount of hydrogen sulfide generated can be suppressed.

When the battery system according to the present embodiment is mounted on a vehicle, the cooler for cooling the secondary battery 2 is not limited to the battery-dedicated cooler, but the vehicle cooler included in the vehicle is a battery. May be used for cooling.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

<Evaluation method 1>
A sample containing Li _2S , which is also available as a commercial product, was evaluated according to the following method.
(1) Helium gas was used as the inert gas, and the helium gas was passed through a humidifying tank controlled to have a dew point of 13 ° C., and the helium gas discharged from the humidifying tank was used as a humidifying gas (dew point of 13 ° C.).
( ₂ ) Li 2S samples 1 and 2 are placed in the reaction vessels arranged in the constant temperature baths controlled at 25 ° C. and 50 ° C., respectively, and the humidifying gas is passed through the reaction vessel to enter the reaction vessel. The gas that came out of was collected in a gas bag. In addition, Li 2S samples ₃ and 4 are placed in reaction vessels arranged in constant temperature baths controlled at 25 ° C and 50 ° C, respectively, and dry gas is passed through the reaction vessel instead of humidifying gas. , The gas coming out of the reaction vessel was collected in a gas bag.
(3) The gas pack containing the gas discharged from the reaction vessel was recovered every 10 minutes, and the hydrogen sulfide contained in each gas pack was quantitatively analyzed by gas chromatography.
(4) Further, surface analysis of samples 1 to 4 after gas recovery was performed by X-ray electron spectroscopy (XPS). In addition to the samples 1 to 4, the surface analysis of the initial sample 5 which did not perform the evaluation methods (1) to (3) above was also performed by XPS.
<Evaluation of Examples>
FIG. 8 is a graph showing the result of quantitative analysis by gas chromatography [evaluation result of (3)]. Graphs а to d show changes over time in the concentration of hydrogen sulfide generated. Table 1 shows the temperature in the constant temperature bath, the dew point of the humidifying gas, and the amount of hydrogen sulfide generated per initial weight. FIG. 8 shows the characteristics of sample 1, graph b shows the characteristics of sample b, and graph c shows the characteristics of samples 3 and 4.

9 to 11 are graphs showing the results of surface analysis by X-ray photoelectron spectroscopy (XPS). FIG. 9 is a graph in which the spectrum of Li's 1s orbital is peak-divided, FIG. 10 is a graph in which the spectrum of O's 1s orbital is peak-divided, and FIG. 11 is a graph in which the spectrum of S's 2p orbital is peak-divided. It is a graph. Graphs а in FIGS. 9 to 11 show the characteristics of sample 1, graph b shows the characteristics of sample b, graph c shows the characteristics of sample 3, graph d shows the characteristics of sample 4, and graph e shows the characteristics of sample 5. Shows the characteristics of.

As shown in FIG. 8, when the sample 1 (graph а) when the constant temperature bath is set to 25 ° C. and the sample 2 (graph b) when the constant temperature bath is set to 50 ° C. are compared, the sample 1 is more hydrogen sulfide. The peak concentration was low, and the amount of hydrogen sulfide generated was smaller than in Table 1. In other words, it was confirmed that the amount of hydrogen sulfide generated was reduced by lowering the temperature of the sample.

Further, as shown in FIG. 10, the energy peak of 1s of O was highest in sample 2 (graph b), followed by sample 1 (graph b). In sample 2, the temperature in the constant temperature bath is higher than that in sample 1, and the hydrogen sulfide generation reaction proceeds not only to the surface layer of the material but also to the deep layer, so that the lithium oxide is formed to the deep layer. It is considered that the energy peak of 1s of Li became high. On the other hand, in sample 1, the temperature in the constant temperature bath is lower than that in sample 2, hydrogen sulfide generation reaction occurs in the surface layer portion of the material, and the formation of lithium oxide remains in the surface layer portion. It is considered that the energy peak was lower than that of sample 2.

As shown in FIG. 11, regarding the 2p energy peak of S, it was confirmed that in Sample 1 and Sample 2, the energy peak was lower than that of the other Samples 3 to 5 due to the generation of hydrogen sulfide.

<Evaluation method 2>
Samples and (prototypes) containing Li ₆ PS ₅ Cl, which are also available as commercial products, were evaluated by the same methods as in evaluation methods 1 (1) to (3). Samples 6 to 9 were prepared, and in sample 6, the temperature in the constant temperature bath was 25 ° C and the dew point of the humidifying gas was 13 ° C. In sample 7, the temperature in the constant temperature bath was 50 ° C and the dew point of the humidifying gas was 13 ° C. In the sample 9, the temperature in the constant temperature bath was 25 degrees and the dry gas was used, and in the sample 9, the temperature in the constant temperature bath was 50 degrees and the dry gas was used. Graph а in FIG. 12 shows the characteristics of sample 6, graph b shows the characteristics of sample 7, and graph c shows the characteristics of samples 8 and 9.

As shown in FIG. 12, when comparing sample 6 (graph а) when the temperature of the constant temperature bath is 25 ° C. and sample 7 (graph b) when the temperature of the constant temperature bath is 50 ° C., sample 6 is more hydrogen sulfide. The peak concentration was low, resulting in a small amount of hydrogen sulfide generated. In other words, it was confirmed that the amount of hydrogen sulfide generated was reduced by lowering the temperature of the sample.

Although the embodiments of the present invention have been described above, these embodiments have been described for facilitating the understanding of the present invention, and have not been described for the purpose of limiting the present invention. Therefore, each element disclosed in the above-described embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

1 ... Battery case 2 ... Secondary battery 3 ... Sensor 4 ... Controller 5 ... Open / close valve 6 ... Piping 7 ... Heat transfer plate

Claims (5)

A secondary battery having a positive electrode containing a positive electrode active material, a solid electrolyte, and a negative electrode containing a negative electrode active material, and using a sulfur-based material for the positive electrode and / or the solid electrolyte.
Equipped with a controller to control the cooler
The controller
Predicting or detecting the generation of hydrogen sulfide in the secondary battery,
A battery system that cools the secondary battery by the cooler when the generation of hydrogen sulfide in the secondary battery is predicted or detected. In the battery system according to claim 1,
The controller
A battery system that starts cooling the secondary battery within 1 second from the time when the generation of hydrogen sulfide is detected in the secondary battery. In the battery system according to claim 1 or 2.
The controller
Obtain the cell temperature of the secondary battery and
A battery system that cools the secondary battery by the cooler when the cell temperature is higher than the lower limit temperature of the secondary battery that can be lowered by cooling the cooler. In the battery system according to any one of claims 1 to 3.
The controller
Select either the normal charge mode or the quick charge mode to charge the secondary battery, and then charge the secondary battery.
A battery system that does not charge the secondary battery in the quick charge mode when the generation of hydrogen sulfide in the secondary battery is predicted or detected. In a battery cooling method for cooling a secondary battery having a positive electrode containing a positive electrode active material, a solid electrolyte, and a negative electrode containing a negative electrode active material, and using a sulfur-based material for the positive electrode and / or the solid electrolyte.
Using a sensor, the state of the secondary battery is detected,
The generation of hydrogen sulfide in the secondary battery is predicted or detected from the detected value of the sensor.
A method for cooling a battery in which the secondary battery is cooled by a cooler when the generation of hydrogen sulfide is predicted or detected in the secondary battery.

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