Battery system and battery cooling method

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

[Technical Field]

[0001] The present invention relates to a battery system for a secondary battery and a method for cooling a secondary battery. [Background technology]

[0002] Conventionally, solid-state batteries that prevent the generation of hydrogen sulfide gas in emergencies where the battery case is severely damaged have been known (for example, Patent Document 1). The solid-state battery described in Patent Document 1 includes a power generating element in which a positive electrode layer, a sulfide-based solid electrolyte membrane, and a negative electrode layer are laminated in this order, a sealed battery case that houses the power generating element, and a flowable sealant that is immersed in the sealed battery case and does not react with the sulfide-based solid electrolyte membrane. The battery also includes a solidification means that solidifies the flowable sealant when the sealed battery case is damaged. When the sealed battery case is damaged, the flowable sealant, liquid paraffin, solidifies, preventing the sulfide-based solid electrolyte membrane from coming into contact with moisture in the atmosphere, thereby preventing the generation of hydrogen sulfide gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-193729 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional solid-state batteries have a problem in that they cannot prevent the generation of hydrogen sulfide gas unless an emergency occurs in which the battery case is severely damaged.

[0005] The problem to be solved by the present invention is to provide a battery system and a battery cooling method that can suppress the generation of hydrogen sulfide not only in emergency situations where the battery case is severely damaged, but also in other situations. [Means for solving the problem]

[0006] The present invention relates to a method for producing hydrogen sulfide in a secondary battery using a sulfur-based material in the positive electrode and / or solid electrolyte. Check Know the generation of hydrogen sulfide is examined When this is detected, the problem is solved by cooling the secondary battery with a cooler. [Effects of the Invention]

[0007] According to the present invention, the generation of hydrogen sulfide can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a battery system of a secondary battery according to this embodiment. [Figure 2] FIG. 2 is a plan view of the secondary battery according to this embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the secondary battery taken along line III-III in FIG. [Figure 4] FIG. 4 is a conceptual diagram for explaining the transition from when the hydrogen sulfide reaction occurs in a sulfur-based material to when the generation of hydrogen sulfide stops. [Figure 5] FIG. 5 is a flowchart showing the procedure of the method for cooling a secondary battery. [Figure 6] FIG. 6 is a flowchart showing the procedure of a method for cooling a secondary battery according to a modified example of this embodiment. [Figure 7] FIG. 7 is a flowchart showing the procedure of a method for cooling a secondary battery according to a modified example of this embodiment. [Figure 8] 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). [Figure 9] 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). [Figure 10] 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). [Figure 11] 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). [Figure 12] 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. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 is a diagram showing a battery system according to the present embodiment for cooling a secondary battery using a sulfur-based material. 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, cools the secondary battery to suppress the generation of hydrogen sulfide. 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, piping 6, and a heat transfer plate 7.

[0010] The battery case 1 is a metal case that houses the secondary battery 2, the sensor 3, part of the piping 6, and the heat transfer plate .

[0011] As an example of the secondary battery 2 in this embodiment, an all-solid-state lithium-ion secondary battery will be described. The secondary battery 2 includes a power generating element having a positive electrode including a positive electrode active material layer containing a positive electrode active material capable of absorbing and releasing lithium ions, a negative electrode including a negative electrode active material layer containing a negative electrode active material capable of absorbing and releasing lithium ions, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer. In addition to the power generating element, the secondary battery 2 also has an electrode tab and an exterior member that houses the electrode tab and the power generating element. The secondary battery 2 is a battery that uses at least a sulfur-based material, and contains a sulfur component as a material for the positive electrode and / or a material for the solid electrolyte. The detailed structure and materials of the secondary battery will be described later.

[0012] 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 inside the battery case 1 and / or the concentration of gas generated inside the battery case 1, and the sensor 3 may be, for example, a hydrogen sulfide concentration meter, an acceleration sensor, or a pressure sensor. When a sulfur-based material is used in the secondary battery 2, hydrogen sulfide is generated when sulfur reacts with moisture. If hydrogen sulfide is generated inside the battery case 1 for some reason, the concentration of hydrogen sulfide inside the battery case 1 and the pressure inside the battery case 1 will change. Therefore, in this embodiment, the sensor 3 is used to detect the sulfur concentration and internal pressure inside the battery case 1, thereby detecting the state of the secondary battery 2.

[0013] The controller 4 has a CPU, a memory, etc. The controller 4 is a control device that predicts or detects the generation of hydrogen sulfide in the secondary battery 2 based on the detection value of the sensor 3. The controller 4 also 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. In other words, the controller 4 controls a cooler that is composed of the on-off valve 5, the pipe 6, the heat transfer plate 7, etc.

[0014] The on-off valve 5 is provided in the piping 6 and adjusts the flow rate of the refrigerant flowing through the piping 6. The piping 6 is a flow path for circulating the refrigerant and is configured so that the refrigerant flows in and out of the case 1. The refrigerant may be cooling water, air, or a cooling gas. The heat transfer plate 7 is a member for transferring heat from the secondary batteries 2 to the refrigerant flowing through the piping 6. As shown in FIG. 1 , the heat transfer plate 7 is made up of multiple plates arranged with their main surfaces parallel to each other, with one end of each plate connected to another plate serving as the bottom surface. The secondary batteries 2 are arranged between the parallel plates; that is, the multiple plates constituting the heat transfer plate 7 and the multiple secondary batteries 2 are stacked. The on-off valve 5, the piping 6, and the heat transfer plate 7 are part of a cooler, but the battery system according to this embodiment also includes a refrigerant pump, a heat exchanger, and other components of the cooler.

[0015] Next, the structure of the secondary battery (all-solid-state lithium ion secondary battery) 2 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a plan view of the secondary battery 2 according to this embodiment, and Fig. 3 is a cross-sectional view of the secondary battery 2 taken along line III-III in Fig. 2. Note that the structure of the secondary battery 2 is not limited to the structure shown in Figs. 2 and 3, and other structures may also be used.

[0016] As shown in FIGS. 2 and 3 , the secondary battery 2 is composed of a power generating element 101 having three positive electrode layers 102, seven electrolyte layers 103, and three negative electrode layers 104, positive electrode tabs 105 connected to the three positive electrode layers 102, respectively, negative electrode tabs 106 connected to the three negative electrode layers 104, and an upper exterior member 107 and a lower exterior member 108 that accommodate and seal the power generating element 101, positive electrode tabs 105, and negative electrode tabs 106.

[0017] The numbers of the positive electrode layers 102, the electrolyte layers 103, and the negative electrode layers 104 are not particularly limited, and the power generating element 101 may be configured with one positive electrode layer 102, three electrolyte layers 103, and one negative electrode layer 104, or the numbers of the positive electrode layers 102, the electrolyte layers 103, and the negative electrode layers 104 may be appropriately selected as needed.

[0018] The positive electrode layer 102 constituting the power generating element 101 includes a positive electrode current collector 102a extending to the positive electrode tab 105, and positive electrode active material layers formed on both main surfaces of a portion of the positive electrode current collector 102a. The positive electrode current collector 102a constituting the positive electrode layer 102 can be made of an electrochemically stable metal foil such as aluminum foil, aluminum alloy foil, copper-titanium foil, or stainless steel foil. Metals such as nickel, iron, and copper may also be used for the positive electrode current collector 102a. Other materials that may be used include a clad material of nickel and aluminum, a clad material of copper and aluminum, and the like.

[0019] Instead of metal, a conductive resin may be used for the positive electrode current collector 102a. The conductive resin may be a resin obtained by adding a conductive filler to a non-conductive polymeric material as needed. Examples of non-conductive polymeric materials include polyethylene (PE; high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polypropylene (PP), and polyethylene terephthalate (PET), which have excellent potential resistance. The conductive filler can be any conductive material. Examples of materials with excellent conductivity, potential resistance, or lithium ion blocking properties include metals and conductive carbon. Examples of metals include, but are not limited to, at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or alloys or metal oxides containing these metals.

[0020] The positive electrode active material layer constituting the positive electrode layer 102 is not particularly limited, but may be a layered rock salt active material such as LiCoO2, LiMnO2, LiNiO2, LiVO2, or Li(Ni-Mn-Co)O2; LiMn2O4, LiNi 0.5 Mn 1.5 Examples of oxide active materials include spinel-type active materials such as LiFePO4 and LiMnPO4, olivine-type active materials such as LiFeSiO4 and LiMnSiO4, and Si-containing active materials such as LiFeSiO4 and LiMnSiO4. 12 Examples of such composite oxides include those containing lithium and nickel. Composite oxides containing lithium and nickel are preferably used, and more preferably Li(Ni-Mn-Co)O2 and those in which part of the transition metals in these oxides are substituted with other elements (hereinafter simply referred to as "NMC composite oxides"). As mentioned above, NMC composite oxides also include composite oxides in which part of the transition metal elements are substituted with other metal elements. In such cases, examples of such other elements include Ti, Zr, Nb, W, and P.

[0021] The cathode active material layer may contain a sulfur-based cathode active material. Examples of sulfur-based cathode active materials include particles or thin films of organic sulfur compounds or inorganic sulfur compounds, and any material can be used as long as it utilizes the oxidation-reduction reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharging. Examples of organic sulfur compounds include disulfide compounds and sulfur-modified polyacrylonitrile. Examples of inorganic sulfur compounds include sulfur (S), S-carbon composite, TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, Li2S, MoS2, and MoS3.

[0022] Note that positive electrode active materials other than those mentioned above may also be used. The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. The amount of the positive electrode active material contained 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 additive, and a binder, as needed. The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. The amount of the positive electrode active material contained 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 additive, and a binder, as needed. 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 described below can be used.

[0023] The conductive additive is not particularly limited, but is preferably in the form of particles or fibers. When the conductive additive 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, column, irregular shape, scale, or spindle shape.

[0024] When the conductive assistant is in particulate form, the average particle size (primary particle size) is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of the electrical properties of the battery.

[0025] Examples of binders include thermoplastic polymers such as polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyethernitrile, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and its hydrogenated products, styrene-isoprene-styrene block copolymer and its hydrogenated products; tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTF), etc. Fluororesins such as vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluororubber (VDF-PFP-TFE fluororubber), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene fluororubber (VDF-PFMVE-TFE fluororubber), vinylidene fluoride-chlorotrifluoroethylene fluororubber (VDF-CTFE fluororubber), and other vinylidene fluoride fluororubber; epoxy resins; and the like. Among these, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

[0026] Each of the positive electrode current collectors 102a constituting the three positive electrode layers 102 is joined to a positive electrode tab 105. The positive electrode tab 105 may be made of aluminum foil, aluminum alloy foil, copper foil, nickel foil, or the like.

[0027] The negative electrode layer 104 constituting the power generating element 101 has a negative electrode side current collector 104a extending to the negative electrode tab 106 and a negative electrode active material layer formed on each of the two main surfaces of a portion of the negative electrode side current collector 104a.

[0028] The negative electrode side current collector 104a of the negative electrode layer 104 is made of an electrochemically stable metal foil such as nickel foil, copper foil, stainless steel foil, or iron foil.

[0029] The negative electrode layer 104 is formed of a layer containing a negative electrode active material. The type of negative electrode active material is not particularly limited, but examples thereof include carbon materials, metal oxides, and metal active materials. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of metal oxides include Nb2O5, Li4Ti5O 12 , SiO, etc. Furthermore, examples of the metal active material include simple metals such as In, Al, Si, and Sn, and alloys such as TiSi and La3Ni2Sn7.

[0030] The negative electrode active material may be a metal containing Li. Such a negative electrode active material is not particularly limited as long as it is an active material containing Li. It may be Li metal or a lithium alloy containing Li. Examples of lithium alloys include alloys of lithium and at least one metal selected from gold (Au), magnesium (Mg), aluminum (Al), calcium (Ca), zinc (Zn), tin (Sn), and bismuth (Bi). The lithium alloy may also be an alloy of lithium and two or more of the above-mentioned metals. Specific examples of lithium alloys include lithium-gold alloy (Li-Au), lithium-magnesium alloy (Li-Mg), lithium-aluminum alloy (Li-Al), lithium-calcium alloy (Li-Ca), lithium-zinc alloy (Li-Zn), lithium-tin alloy (Li-Sn), and lithium-bismuth alloy (Li-Bi).

[0031] The negative electrode active material layer may contain any lithium alloy, and its configuration is not particularly limited. For example, when the metal other than lithium constituting the lithium alloy is "Me", the negative electrode active material layer may have any of the following embodiments (1) to (3). (1) A single layer consisting of only a lithium alloy (i.e., a Li-Me layer) (2) A layer made of lithium metal and a layer made of a lithium alloy (i.e., a Li layer / Li-Me layer) (3) A layer made of lithium metal, a layer made of a lithium alloy, and a layer made of a metal other than lithium (i.e., Li layer / Li-Me layer / Me layer) In the above embodiment (2), it is desirable that a layer made of a lithium alloy (Li-Me layer) be the layer on the electrolyte layer 103 side (the layer that forms the interface with the electrolyte layer 103), and in the above embodiment (3), it is desirable that a layer made of a metal other than lithium (Me layer) be the layer on the electrolyte layer 103 side (the layer that forms the interface with the electrolyte layer 103). When using a lithium metal layer containing lithium metal and a layer (intermediate layer) containing a metal different from lithium metal, the intermediate layer is a layer between the lithium metal layer and the solid electrolyte, and it is desirable that at least a portion of the lithium metal and at least a portion of the metal that forms the intermediate layer are alloyed.

[0032] For example, when the negative electrode has the above-mentioned configuration (3), i.e., a configuration including a layer of lithium metal, a layer of a lithium alloy, and a layer of a metal other than lithium (i.e., Li layer / Li-Me layer / Me layer), stacking the lithium metal and the metal other than lithium alloys the interface between them, thereby forming a layer of lithium alloy at the interface. The method for stacking the lithium metal and the metal other than lithium is not particularly limited, but examples include a method in which the metal other than lithium is deposited on the layer of lithium metal by vacuum deposition or the like, thereby forming a layer of the metal other than lithium on the layer of lithium metal and alloying the interface between them. Alternatively, examples include a method in which lithium metal is deposited on the layer of the metal other than lithium by vacuum deposition or the like, and forming a layer of lithium metal on the layer of the metal other than lithium and alloying the interface between them.

[0033] In the secondary battery 2 of this 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 joined to a single negative electrode tab 106. That is, in the secondary battery 2 of this embodiment, each negative electrode layer 104 is joined to a single common negative electrode tab 106.

[0034] The electrolyte layer 103 of the power generating element 101 prevents a short circuit between the above-mentioned positive electrode layer 102 and negative electrode layer 104, contains a solid electrolyte as a main component, and is a layer interposed between the above-mentioned positive electrode active material layer and negative electrode active material layer. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes, but a sulfide solid electrolyte is preferred.

[0035] Examples of sulfide solid electrolytes include LiI-Li2S-SiS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, LiI-Li3PS4, LiI-LiBr-Li3PS4, Li3PS4, Li6PS5Cl, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2OLiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Examples include Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are positive numbers and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-LixMOy (where x and y are positive numbers and M is P, Si, Ge, B, Al, Ga, or In). Note that the term "Li2S-P2S5" refers to a sulfide solid electrolyte obtained using a raw material composition containing Li2S and P2S5, and the same applies to other terms.

[0036] The sulfide solid electrolyte may have, for example, a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of sulfide solid electrolytes having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Examples of sulfide solid electrolytes having a Li4P2S7 skeleton include Li-PS-based solid electrolytes known as LPS (for example, Li7P3S 11 ) can be mentioned. In addition, examples of sulfide solid electrolytes include Li (4-x) Ge(1-x) P x x LGPS or the like represented by S4 (where 0 < x < 1) may be used. Among them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing P element, and more preferably a material mainly composed of Li2S-P2S5. Further, the sulfide solid electrolyte may contain halogen (F, Cl, Br, I).

[0037] When the sulfide solid electrolyte is of the Li2S-P2S5 system, the ratio of Li2S and P2S5 is preferably within the range of molar ratio Li2S:P2S5 = 50:50 to 100:0, and more preferably Li2S:P2S5 = 70:30 to 80:20. Also, the sulfide solid electrolyte may be a sulfide glass, a 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 (such as a ball mill) on the raw material composition. Also, the crystallized sulfide glass can be obtained, for example, by performing heat treatment on the sulfide glass at a temperature above the crystallization temperature. The ionic conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25 °C) is, for example, 1×10 -5 S / cm or more, and more preferably 1×10 -4 S / cm or more. The value of the ionic conductivity of the solid electrolyte can be measured by the alternating current impedance method.

[0038] Examples of the oxide solid electrolyte include compounds having a NASICON-type structure. As an example of a compound having a NASICON-type structure, a compound represented by the general formula Li 1+x Al x Ge 2-x (PO4)3 (0 ≤ x ≤ 2) (LAGP), a compound represented by the general formula Li 1+x Al x Ti 2-x [[ID=二十七]](PO4)3 (0 ≤ x ≤ 2) (LATP), etc. are mentioned. Also, as another example of the oxide solid electrolyte, LiLaTiO (for example, Li 0.34 La0.5 1TiO3), LiPON (e.g., Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g., Li7La3Zr2O 12 ) etc.

[0039] 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 the binders mentioned above can be used, for example.

[0040] The content of the solid electrolyte is, for example, preferably in the range of 10 to 100 mass %, more preferably in the range of 50 to 100 mass %, and further preferably in the range of 90 to 100 mass %.

[0041] As described above, the cathode layer 102 used in this embodiment contains a sulfur compound as a cathode active material, and thus uses a sulfur-based material, while the electrolyte layer 103 contains a sulfide solid electrolyte as a main component, and thus uses a sulfur material. Note that the transition material may be used in either the cathode layer 102 or the electrolyte layer 103.

[0042] As shown in FIG. 3, the positive electrode layers 102 and the negative electrode layers 104 are alternately stacked with the electrolyte layers 103 interposed therebetween, and the electrolyte layers 103 are stacked on the top and bottom layers, respectively, thereby forming the power generating element 101.

[0043] The power generating element 101 configured as described above is housed in and sealed in an upper exterior member 107 and a lower exterior member 108. The upper exterior member 107 and the lower exterior member 108 for sealing the power generating element 101 are formed of a flexible material, such as a resin film such as polyethylene or polypropylene, or a resin-metal thin film laminate material in which both sides of a metal foil such as aluminum are laminated with a resin such as polyethylene or polypropylene, and by heat-sealing the upper exterior member 107 and the lower exterior member 108, the power generating element 101 is sealed with the positive electrode tab 105 and the negative electrode tab 106 protruding to the outside.

[0044] Note that, in the portions of the positive electrode tab 105 and the negative electrode tab 106 that come into contact with the upper exterior member 107 and the lower exterior member 108, sealing films 109 are provided to ensure adhesion with the upper exterior member 107 and the lower exterior member 108. The sealing film 109 is not particularly limited, but can be made of, for example, a synthetic resin material that has excellent electrolyte resistance and heat-sealing properties, such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer.

[0045] As described above, the secondary battery used in this embodiment contains a sulfur-based material. If sulfur reacts with water for some reason, hydrogen sulfide is generated. If hydrogen sulfide leaks out of the secondary battery 2 (cell battery), it may corrode metal components inside the battery case 1. Therefore, if the generation of hydrogen sulfide is predicted or detected, it is necessary to suppress the generation of hydrogen sulfide.

[0046] According to the inventor's findings, the lower the cell temperature of the secondary battery 2, the more the amount of hydrogen sulfide generated can be reduced. The reason for this will be explained below with reference to FIG. 4. FIG. 4 is a conceptual diagram for explaining the transition from when a hydrogen sulfide reaction occurs in a sulfur-based material to when the generation of hydrogen sulfide stops. In FIG. 4, (a) shows the transition of the reaction in the sulfur-based material at low temperatures, and (b) shows the transition of the reaction in the sulfur-based material at high temperatures.

[0047] When a sulfur-based material comes into contact with moisture, hydrogen sulfide is generated. Simultaneously with this hydrogen sulfide generation reaction, lithium metal reacts with oxygen to form lithium compounds. The manner in which the lithium compounds are formed varies depending on the cell temperature. As shown in FIG. 4(a), when the cell temperature is low, the hydrogen sulfide generation reaction occurs in the surface layer of the sulfur-based material 41, and lithium compounds 42 are formed in the surface layer of the sulfur-based material 41. When the sulfur-based material 41 is covered with lithium compounds 42, the generation of hydrogen sulfide stops. At low temperatures, the hydrogen sulfide generation reaction does not progress deep into the sulfur-based material 41, and lithium compounds 42 are formed mainly in the surface layer. Therefore, the formation of lithium compounds 42 proceeds uniformly in the surface layer, effectively suppressing the generation of hydrogen sulfide and the amount of hydrogen sulfide generated.

[0048] On the other hand, as shown in FIG. 4(b), when the cell temperature is high, the hydrogen sulfide generation reaction progresses deep into the sulfur-based material 41. Therefore, lithium compounds 43 are formed not only on the surface of the sulfur-based material 41 but also in the deep layers. When the sulfur-based material 41 is covered with lithium compounds 42, the generation of hydrogen sulfide stops. Because the hydrogen sulfide generation reaction progresses deep into the sulfur-based material 41 at high temperatures, the formation of lithium compounds 43 does not proceed uniformly compared to low temperatures. It takes time for lithium compounds 42 to cover the surface of the sulfur-based material 41, and the amount of hydrogen sulfide generated increases. In other words, when hydrogen sulfide generation in the secondary battery 2 is predicted or detected, the generation of hydrogen sulfide can be suppressed by forcibly cooling the secondary battery 2.

[0049] Next, a description will be given of a method in this embodiment for detecting generation of hydrogen sulfide and cooling the secondary battery 2. Fig. 5 is a flowchart showing the control procedure of the controller 4. The controller 4 executes the control flow of Fig. 5 when charging / discharging current of the secondary battery 2.

[0050] In step S1, the controller 4 detects the state of the secondary battery 2 by acquiring the detection 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 a preset judgment threshold. The judgment threshold is a threshold for determining that hydrogen sulfide is being generated in the secondary battery 2. For example, if a hydrogen sulfide concentration meter is used as the sensor 3, the judgment threshold is defined as the concentration of hydrogen sulfide. If the detection value of the sensor 3 is less than the judgment threshold, the controller 4 determines that hydrogen sulfide is not being generated in the secondary battery 2. Then, the control flow returns to step S1. The controller 4 detects the presence or absence of hydrogen sulfide generation during use of the secondary battery 2 by repeatedly executing the control processes of steps S1 and S2.

[0051] If the detection value of the sensor 3 is equal to or greater than the determination threshold, the controller 4 determines that hydrogen sulfide is being 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 has stopped the circulation of the refrigerant, and operates the refrigerant pump (not shown) to circulate the refrigerant and start cooling the secondary battery 2. Note that the sooner the cooling of the secondary battery 2 is started relative to the point in time when the generation of hydrogen sulfide is detected, the better, but it is preferable that the controller 4 operate the refrigerant pump and start cooling the secondary battery 2 within one second from the point in time when the generation of hydrogen sulfide is detected in step S2.

[0052] In step S4, the controller 4 determines whether to terminate the cooling of the secondary battery 22. For example, the amount of hydrogen sulfide generated is detected from the detection value of the sensor, and when the increase in the amount of hydrogen sulfide per predetermined time is less than a predetermined value, the controller 4 terminates the cooling of the secondary battery 22. Alternatively, if the cooling time is set in advance, the controller 4 terminates the cooling of the secondary battery 22 when the predetermined time has elapsed since the start of cooling. If the cooling of the secondary battery 22 is not to be terminated, the controller 4 continues the cooling of the secondary battery 2. In this way, cooling of the secondary battery 2 is initiated immediately after the generation of hydrogen sulfide is detected, which allows the formation of lithium compounds to proceed uniformly in the surface layer of the transition material and suppresses the generation of hydrogen sulfide.

[0053] As described above, in this embodiment, generation of hydrogen sulfide is detected in a secondary battery 2 that uses a sulfur-based material for the positive electrode and / or solid electrolyte, and if generation of hydrogen sulfide is detected, the secondary battery is cooled by a cooler. This reduces the cell temperature of the secondary battery 2 and suppresses generation of hydrogen sulfide, thereby reducing the amount of hydrogen sulfide generated.

[0054] In this embodiment, cooling of the secondary battery 2 is started within one second from the time when the generation of hydrogen sulfide is detected. Because hydrogen sulfide is generated in large amounts in the early stages after 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.

[0055] Furthermore, in this embodiment, if the generation of hydrogen sulfide is not detected, the cooler is not used to control cooling of the secondary battery 2. Since the cell temperature of the secondary battery 2 tends to rise during charging, if the generation of hydrogen sulfide is detected, the cooler is used to control cooling of the secondary battery 2. This effectively suppresses the generation of hydrogen sulfide.

[0056] As a modification of this embodiment, the controller 4 may execute control to cool the secondary battery 2 in accordance with the cell temperature of the secondary battery 2. FIG. 6 is a flowchart showing the control procedure of the controller 4. In step S11, the controller 4 acquires a detection value of the sensor 3. In step S12, the controller 4 detects whether or not hydrogen sulfide is being generated in the secondary battery 2. The control processes of steps S11 and S12 are the same as the control processes of steps S1 and S2 described above, respectively.

[0057] In step S13, the controller 4 acquires the cell temperature of the secondary battery 2. The battery system in this modified example is equipped with 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 lowest value of the temperature of the secondary battery 2 that can be reduced by cooling with the cooler. The lower limit temperature is a value determined by the cooling performance of the cooler, environmental factors such as the outside temperature, and is set in advance. In other words, the cell temperature of the secondary battery can be reduced to the lower limit temperature by cooling with the cooler. The controller 4 may change the lower limit temperature as appropriate depending on the outside temperature.

[0058] If the cell temperature is higher than the lower limit temperature, the cell temperature of the secondary battery 2 can be lowered below the current temperature, and therefore, in step S15, the controller 4 starts cooling the secondary battery 2. The control process of step S15 is the same as the control process of step S4 described above. In step S16, the controller 4 determines whether or not to end cooling of the secondary battery 22. For example, if the cell temperature of the secondary battery 2 reaches the lower limit temperature, the controller 4 ends cooling of the secondary battery 2.

[0059] If the cell temperature is below the lower limit temperature, the cooler cannot cool the secondary battery 2 to a temperature lower than the current temperature, so the controller 4 does not use the cooler to cool it, and ends the control flow. That is, in this modification, the controller 4 determines whether the current secondary battery 2 can be cooled by the cooler based on the temperature of the secondary battery 2 and the cooling capacity of the cooler, and does not use the cooler to cool it if the current cell temperature of the secondary battery is at a temperature that cannot be cooled by the cooler.

[0060] In a modification of this embodiment, the cell temperature of the secondary battery 2 is acquired, and if the cell temperature is higher than the lowest temperature of the secondary battery 2 that can be lowered by cooling with the cooler, the cooler cools the secondary battery 2. As a result, if the cooler cannot lower the temperature of the secondary battery 2, the cooler does not operate, thereby reducing unnecessary power consumption.

[0061] In another variation of this embodiment, the battery system can select either a normal charge mode or a rapid charge mode and charge the secondary battery 2 in the selected mode, and the controller 4 may control the system so that charging in the rapid charge mode is not performed if generation of hydrogen sulfide is detected. FIG. 7 is a flowchart showing the control procedure of the controller 4. The battery system has a charging circuit for the normal charge mode and a charging circuit for the rapid charge mode, and switches between the charging circuits depending on the selected charging mode. The rapid charge mode is a mode in which charging is performed at a C rate higher than that in the normal charge mode. The charging mode is selected based on a user's operation command. The controller 4 selects either the normal charge mode or the rapid charge mode and controls 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 the control flow when charging the secondary battery 2 in the rapid charge mode.

[0062] In step S21, the controller 4 selects the rapid charge mode based on an operation command from the user. In step S22, the controller 4 acquires a detection value from the sensor 3. In step S23, the controller 4 detects whether or not hydrogen sulfide is being generated in the secondary battery 2. The control processes in steps S22 and S23 are similar to the control processes in steps S1 and S2 above, respectively.

[0063] If generation of hydrogen sulfide is not detected, in step S24, the controller 4 starts charging the secondary battery 2 in rapid charge mode. In step S25, while the secondary battery 2 is being charged, the controller 4 calculates the current state of charge (SOC) of the secondary battery 2 by current integration or the like, and determines whether or not to terminate charging of the secondary battery 2 based on the calculated SOC. If the current SOC reaches an upper limit SOC indicating full charge, the controller 4 terminates charging of the secondary battery 2. In other words, even if rapid charge mode is selected, if generation of hydrogen sulfide is detected, the secondary battery 2 is not charged in rapid charge mode, and the secondary battery 2 is cooled to suppress generation of hydrogen sulfide.

[0064] If generation of hydrogen sulfide is detected, in step S26, the controller 4 starts cooling the secondary battery 22. In step S27, the controller 4 determines whether or not to end cooling of the secondary battery 22. The control processes in steps S26 and S27 are similar to the control processes in steps S3 and S4 above, respectively.

[0065] If generation of hydrogen sulfide is not detected, in step S26 the controller 4 starts charging the secondary battery 2 in rapid charge mode. In step S27, while the secondary battery 2 is being charged, the controller 4 calculates the current state of charge (SOC) of the secondary battery 2 by current integration or the like, and determines whether or not to terminate charging of the secondary battery 2 based on the calculated SOC. If the current SOC reaches an upper limit SOC that indicates full charge, the controller 4 terminates charging of the secondary battery 2.

[0066] That is, in this modification, the secondary battery 2 is charged in either the charge mode or the rapid charge mode, and if generation of hydrogen sulfide is detected in the secondary battery 2, the secondary battery 2 is not charged in the rapid charge mode. This prevents a temperature rise in the secondary battery 2 due to rapid charge, and suppresses the amount of hydrogen sulfide generated.

[0067] In this embodiment, the controller 4 does not necessarily need to detect the generation of hydrogen sulfide, but may instead predict the generation of hydrogen sulfide. For example, the controller 4 predicts the generation of hydrogen sulfide when a short circuit is detected in the secondary battery 2. A short circuit in the secondary battery 2 may be detected from a change in current during charging and discharging of the secondary battery 2 or from the internal resistance of the secondary battery 2. If the generation of hydrogen sulfide is predicted, the controller 4 cools the secondary battery 2. In the control process of steps S1 and S2 of the control flow shown in FIG. 5, the controller 4 acquires detection values ​​indicating the state of the secondary battery 2 from a current sensor that detects the current of the secondary battery 2, an impedance meter, or the like, and predicts the generation of hydrogen sulfide by determining whether a short circuit has occurred based on the acquired values. If it is determined that a short circuit has occurred, the controller 4 predicts the generation of hydrogen sulfide in the secondary battery.

[0068] As described above, in this embodiment, generation of hydrogen sulfide in the secondary battery 2 is predicted, and if generation of hydrogen sulfide is predicted, the secondary battery is cooled by a cooler. This reduces the cell temperature of the secondary battery 2 and suppresses generation of hydrogen sulfide, thereby suppressing the amount of hydrogen sulfide generated.

[0069] When the battery system according to this embodiment is mounted on a vehicle, the cooler for cooling the secondary battery 2 is not limited to a cooler dedicated to the battery, but a vehicle cooler included in the vehicle may be used to cool the battery. [Example]

[0070] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[0071] <Evaluation Method 1> Commercially available samples containing Li2S were evaluated according to the following method. (1) Helium gas was used as the inert gas. The helium gas was passed through a humidifying tank controlled at a dew point of 13°C, and the helium gas coming out of the humidifying tank was used as humidified gas (dew point 13°C). (2) Li2S samples 1 and 2 were placed in reaction vessels placed in thermostatic chambers controlled at 25°C and 50°C, respectively, and humidified gas was passed through the reaction vessels, and the gas emerging from the reaction vessels was collected in a gas bag. Li2S samples 3 and 4 were placed in reaction vessels placed in thermostatic chambers controlled at 25°C and 50°C, respectively, and dry gas was passed through the reaction vessels instead of humidified gas, and the gas emerging from the reaction vessels was collected in a gas bag. (3) Gas packs containing the gas released from the reaction vessel were collected every 10 minutes, and the hydrogen sulfide contained in each gas pack was quantitatively analyzed by gas chromatography. (4) Furthermore, surface analysis by X-ray photoelectron spectroscopy (XPS) was performed on Samples 1 to 4 after gas recovery. In addition to Samples 1 to 4, surface analysis by XPS was also performed on Sample 5, an initial product that had not been subjected to the evaluation methods (1) to (3) above. <Evaluation of Examples> Figure 8 is a graph showing the results of quantitative analysis by gas chromatography [evaluation results of (3)]. Graphs a to d show the change in the concentration of generated hydrogen sulfide over time. The temperature inside the thermostatic chamber, the dew point of the humidified gas, and the amount of hydrogen sulfide generated per initial weight are shown in Table 1. Graph a in Figure 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. [Table 1]

[0072] 9 to 11 are graphs showing the results of surface analysis by X-ray photoelectron spectroscopy (XPS). Fig. 9 is a graph showing peak division of the spectrum of the Li 1s orbital, Fig. 10 is a graph showing peak division of the spectrum of the O 1s orbital, and Fig. 11 is a graph showing peak division of the spectrum of the S 2p orbital. In Figs. 9 to 11, graph a shows 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.

[0073] As shown in Figure 8, when Sample 1 (graph a) when the thermostatic bath was set at 25°C is compared with Sample 2 (graph b) when the thermostatic bath was set at 50°C, Sample 1 had a lower peak hydrogen sulfide concentration and also generated less hydrogen sulfide than Table 1. In other words, it was confirmed that lowering the temperature of the sample reduced the amount of hydrogen sulfide generated.

[0074] Furthermore, as shown in Figure 10, the O 1s energy peak was highest for Sample 2 (graph b), followed by Sample 1 (graph b). Compared to Sample 1, Sample 2 had a higher temperature in the thermostatic chamber, which caused the hydrogen sulfide generation reaction to proceed not only in the surface layer but also to the deeper layers of the material, resulting in the formation of lithium oxide in the deeper layers, which is thought to have resulted in the higher Li 1s energy peak. On the other hand, Sample 1 had a lower temperature in the thermostatic chamber compared to Sample 2, which caused the hydrogen sulfide generation reaction to occur in the surface layer of the material, with the formation of lithium oxide remaining in the surface layer, resulting in the Li 1s energy peak being lower than that of Sample 2.

[0075] As shown in FIG. 11, it was confirmed that the energy peak of 2p of S in Samples 1 and 2 was lower than that of Samples 3 to 5 due to the generation of hydrogen sulfide.

[0076] <Evaluation Method 2> Commercially available samples and prototypes containing Li6PS5Cl were evaluated using the same methods as (1) to (3) of Evaluation Method 1. Samples 6 to 9 were prepared. For Sample 6, the temperature in the thermostatic chamber was 25°C and the dew point of the humidified gas was 13°C. For Sample 7, the temperature in the thermostatic chamber was 50°C and the dew point of the humidified gas was 13°C. For Sample 8, the temperature in the thermostatic chamber was 25°C and dry gas was used. For Sample 9, the temperature in the thermostatic chamber was 50°C and dry gas was used. Graph a in Figure 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.

[0077] As shown in Figure 12, when Sample 6 (graph a) when the thermostatic bath was set at 25°C is compared with Sample 7 (graph b) when the thermostatic bath was set at 50°C, the peak hydrogen sulfide concentration was lower and the amount of hydrogen sulfide generated was less for Sample 6. In other words, it was confirmed that the amount of hydrogen sulfide generated was reduced by lowering the temperature of the sample.

[0078] Although the embodiments of the present invention have been described above, these embodiments are described to facilitate understanding of the present invention and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Explanation of symbols]

[0079] 1. Battery case 2…Secondary battery 3...Sensor 4...Controller 5...Shut-off valve 6...Plumbing 7...Heat transfer plate

Claims

1. 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, wherein a sulfur-based material is used for the positive electrode and / or the solid electrolyte; a detection means for detecting hydrogen sulfide, the detection means being provided outside the secondary battery and within the battery case; a controller for controlling the cooler, The controller detecting generation of hydrogen sulfide in the secondary battery based on the detection value of the detection means; When generation of hydrogen sulfide in the secondary battery is detected, the secondary battery is cooled by the cooler.

2. 2. The battery system according to claim 1, The controller The battery system starts cooling the secondary battery within one second from the time when generation of hydrogen sulfide in the secondary battery is detected.

3. 3. The battery system according to claim 1, The controller acquiring a cell temperature of the secondary battery; A battery system in which the cooler cools the secondary battery when the cell temperature is higher than a lower limit temperature of the secondary battery that can be lowered by cooling with the cooler.

4. The battery system according to any one of claims 1 to 3, The controller selecting either a normal charging mode or a rapid charging mode to charge the secondary battery; A battery system that does not charge the secondary battery in the rapid charge mode when generation of hydrogen sulfide in the secondary battery is predicted or detected.

5. 2. The battery system according to claim 1, The cooler is disposed outside the secondary battery and within the battery case, and directly cools the secondary battery from the outside.

6. 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, wherein a sulfur-based material is used for the positive electrode and / or the solid electrolyte, detecting a state of the secondary battery using a sensor that is provided outside the secondary battery and inside a battery case and detects hydrogen sulfide; detecting generation of hydrogen sulfide in the secondary battery from the detection value of the sensor; When generation of hydrogen sulfide in the secondary battery is detected, the secondary battery is cooled by a cooler.

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