Abnormality detection system and power storage module

Abstract

An abnormality detection system according to an embodiment of the present disclosure detects an abnormality in a secondary battery having: an electrode group formed by winding a positive electrode and a negative electrode with a separator disposed therebetween; and an outer package that accommodates the electrode group. The abnormality detection system comprises: a sensor element that is disposed on an outer peripheral surface of the outer package and is capable of detecting a strain value of the outer package; and a data processing unit that determines the secondary battery to be abnormal if the strain value detected by the sensor element changes discontinuously during charging of the secondary battery.

Description

Anomaly detection system and energy storage module

[0001] This invention relates to an anomaly detection system and an energy storage module.

[0002] Secondary batteries, such as lithium-ion batteries, are used in a variety of applications due to their characteristics, including high capacity. A secondary battery comprises, for example, an electrode group consisting of a positive electrode, a negative electrode, and a separator wound between the positive and negative electrodes, a non-aqueous electrolyte (e.g., electrolyte solution), and an outer casing that houses the electrode group and the electrolyte solution.

[0003] During use of such rechargeable batteries, the casing may bulge outward due to factors such as an expanded electrode (e.g., the negative electrode) pressing against the casing outward or an increase in internal pressure. If the bulging becomes significant, a portion of the casing may be damaged, and the electrolyte contained within the casing may leak out through the damaged area. Therefore, it is important to detect the degree of casing expansion in rechargeable batteries.

[0004] Patent Document 1 discloses a battery unit having a plurality of battery cells and strain gauges attached to the outer surface of each of the battery cells, wherein each strain gauge has a pair of electrodes electrically connected to a sensing part, and one electrode of each strain gauge attached to an adjacent battery cell is joined to the other via a conductive joint, and all of the strain gauges are connected in series.

[0005] Patent Document 1 discloses that by configuring the battery unit as described above, information on the expansion or contraction of one or more of the battery cells can be obtained based on the output of strain gauges connected in series.

[0006] Japanese Patent Publication No. 2024-115364

[0007] Incidentally, during the use of a secondary battery, repeated expansion and contraction of the electrodes (e.g., the negative electrode) can cause irregularities in the electrode group, leading to buckling of the electrode group. When such buckling occurs, variations in the distance between the positive and negative electrodes occur within the electrode group. In this case, charging becomes easier in areas where the distance between the positive and negative electrodes is small, and more difficult in areas where the distance is large. As a result, the battery capacity decreases with each charge-discharge cycle. Furthermore, in the case of a lithium-ion secondary battery, lithium metal may be deposited locally on the surface of the negative electrode located in areas of the electrode group that are easily charged (areas with locally high amounts of charged electricity). The deposited lithium metal may react with the electrolyte contained in the electrolyte solution as the battery temperature rises. This can cause a decrease in the thermal stability of the battery after charge-discharge cycles. Therefore, it is preferable to be able to detect electrode group buckling as an abnormality in the secondary battery.

[0008] However, during the use of a secondary battery, the buckled portion of the electrode group is less likely to bulge outward towards the casing, making it difficult to press the casing outward. Therefore, it is difficult to detect the buckling of the electrode group using a sensor element capable of detecting the strain value of the casing (for example, a strain gauge). Furthermore, no known documents, including Patent Document 1, have considered detecting the buckling of the electrode group using strain gauges or the like.

[0009] Therefore, the object of this disclosure is to provide an abnormality detection system and an energy storage module that can detect buckling of an electrode group as an abnormality in a secondary battery.

[0010] One aspect of the present invention relates to an abnormality detection system for detecting an abnormality in a secondary battery having an electrode group around which a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode are wound, and an outer casing housing the electrode group, the abnormality detection system comprising: a sensor element arranged on the outer circumferential surface of the outer casing and capable of detecting the strain value of the outer casing; and a data processing unit that determines the secondary battery is abnormal when the strain value detected by the sensor element decreases discontinuously during charging of the secondary battery.

[0011] Another aspect of the present invention relates to a power storage module comprising: a plurality of secondary batteries each having an electrode group around which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are wound, and an outer casing housing the electrode group; a sensor element disposed on the outer circumferential surface of the outer casing of at least one of the secondary batteries and capable of detecting the strain value of at least one of the outer casings; a data processing unit that determines the secondary battery to be abnormal when the strain value detected by the sensor element decreases discontinuously during charging of the at least one secondary battery; and a shut-off mechanism that shuts off the secondary battery determined to be abnormal by the data processing unit from the other secondary batteries.

[0012] According to this disclosure, it is possible to provide an abnormality detection system and an energy storage module that can detect buckling of an electrode group as an abnormality in a secondary battery.

[0013] This figure illustrates an example of a data processing unit. This is an example of a hardware block diagram of the control unit. This is a schematic cross-sectional view showing a part of the battery module according to this disclosure. This is a cross-sectional view taken along line IV-IV of the battery module shown in Figure 3, and is a transverse cross-section perpendicular to the axial direction of the battery. This is a schematic front view of a cross-section of a part of an example of a secondary battery provided in the battery module. This is a transverse cross-sectional view perpendicular to the axial direction of the battery of a part of another battery module according to this disclosure.

[0014] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are obtained. Notwithstanding, known components may be applied to components of parts that are characteristic of this disclosure. In this specification, when "the range of numerical values ​​A to numerical values ​​B" is used, that range includes numerical values ​​A and B.

[0015] In the following explanation, when examples are given for the lower and upper limits of numerical values ​​related to specific physical properties or conditions, any combination of either of the given lower limits and any of the given upper limits is permitted, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, unless otherwise specified, one type may be selected and used alone, or two or more types may be used in combination.

[0016] This disclosure includes any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims. In other words, any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims is possible, as long as it does not result in a technical inconsistency.

[0017] [Anomaly Detection System] An anomaly detection system according to the embodiment of this disclosure is an anomaly detection system for detecting an anomaly in a secondary battery. The secondary battery has an electrode group in which a positive electrode, a negative electrode, and a separator wound between the positive electrode and the negative electrode are arranged, and an outer casing that houses the electrode group. The anomaly detection system according to the embodiment of this disclosure comprises a sensor element arranged on the outer circumferential surface of the outer casing and capable of detecting the strain value of the outer casing, and a data processing unit that determines the secondary battery is abnormal when the strain value detected by the sensor element decreases discontinuously during charging of the secondary battery.

[0018] (Secondary Batteries) The following describes the structure of a secondary battery, using a lithium secondary battery as an example. A lithium secondary battery comprises an electrode group and an outer casing that houses the electrode group and a non-aqueous electrolyte. Lithium secondary batteries include lithium metal secondary batteries and lithium-ion secondary batteries. In a lithium metal secondary battery, lithium metal is deposited at the negative electrode during charging and dissolved during discharging. In a lithium-ion secondary battery, lithium ions move toward the negative electrode during charging and toward the positive electrode during discharging. That is, in a lithium metal secondary battery, charging and discharging are performed by the deposition and dissolution of lithium metal at the negative electrode, whereas in a lithium-ion secondary battery, charging and discharging are performed by the movement of lithium ions between the positive and negative electrodes. In the following, the outer casing will also be referred to as a battery case. The electrode group is formed by winding a positive electrode, a negative electrode, and a separator placed between the positive and negative electrodes.

[0019] The battery case may, for example, have a bottomed cylindrical portion having an opening on one end and a bottom on the second end opposite the first end, and a sealing body that seals the opening of the bottomed cylindrical portion. At least one of the sealing body and the bottom is usually provided with a safety mechanism to release gas or the like from inside the battery when the internal pressure of the battery rises. The structure of this safety mechanism is not particularly limited. Conventional known mechanisms may be used as the safety mechanism. Furthermore, providing the above safety mechanism in both the sealing body and the battery case (more specifically, the bottom of the battery case) can further enhance the safety of the lithium secondary battery.

[0020] In a lithium secondary battery, a ring-shaped groove may be formed on the first end side. A sealing body is usually placed in the groove, and the closed-bottom cylindrical portion is sealed by the placement of the sealing body in the groove. In such a lithium secondary battery, for example, the sealing body is electrically connected to one electrode (e.g., the positive electrode) that constitutes the electrode group and functions as a terminal (e.g., the positive electrode terminal), and the closed-bottom cylindrical portion is electrically connected to the other electrode (e.g., the negative electrode) that constitutes the electrode group and functions as a terminal (e.g., the negative electrode terminal).

[0021] The negative electrode of a lithium secondary battery has at least a negative electrode current collector. When the lithium secondary battery is a lithium metal secondary battery, during charging, lithium metal is deposited on the negative electrode current collector.

[0022] In a lithium metal secondary battery, 70% or more of the rated capacity is exhibited by the deposition and dissolution of lithium metal. During charging and discharging, the electron transfer at the negative electrode is mainly caused by the deposition and dissolution of lithium metal at the negative electrode. Specifically, during charging and discharging, 70 to 100% (for example, 80 to 100%, or 90 to 100%) of the electron transfer (current from other viewpoints) at the negative electrode is caused by the deposition and dissolution of lithium metal. That is, the negative electrode of a lithium metal secondary battery is different from the negative electrode of a lithium-ion secondary battery in that during charging and discharging, the electron transfer at the negative electrode is mainly caused by the insertion and extraction of lithium ions by a negative electrode active material (for example, graphite).

[0023] In a secondary battery in which lithium metal is deposited on the negative electrode during charging, the open circuit potential (OCV: Open Circuit Voltage) of the negative electrode at full charge is, for example, 70 mV or less with respect to lithium metal (lithium dissolution and deposition potential). Full charge means a state in which the battery is charged until, for example, the state of charge (SOC: State of Charge) reaches 0.98×C or more when the rated capacity of the battery is C. The OCV of the negative electrode at full charge can be measured by assembling a battery cell using this negative electrode and lithium metal as the counter electrode after disassembling the fully charged battery to take out the negative electrode in an inert gas atmosphere (for example, an argon gas atmosphere). The non-aqueous electrolyte contained in the battery cell may have the same composition as the non-aqueous electrolyte contained in the disassembled secondary battery.

[0024] Although the lithium metal secondary battery as described above has a high energy density, in the negative electrode, lithium metal is deposited during charging and dissolved during discharging. Therefore, the negative electrode repeatedly undergoes large expansion and contraction during charge and discharge. In other words, during the use of the lithium metal secondary battery, the negative electrode repeatedly undergoes large expansion and contraction. And when the negative electrode repeatedly undergoes large expansion and contraction, the electrode group also repeatedly undergoes large expansion and contraction in the direction outward from the winding axis. Thus, when the electrode group repeatedly undergoes large expansion and contraction, unevenness occurs in the electrode group, and the electrode group may buckle. Also, in the case where the secondary battery is a lithium-ion secondary battery, as the negative electrode active material repeatedly expands and contracts during charge and discharge, the negative electrode mixture layer containing the negative electrode active material also repeatedly expands and contracts. And this may cause the electrode group to buckle. In addition, when the negative electrode active material is an alloy-based material such as a silicon (Si)-containing material and a tin (Sn)-containing material, the degree of expansion and contraction of the negative electrode active material during charge and discharge becomes even larger, so the electrode group is more likely to buckle.

[0025] When the above-mentioned buckling occurs in the electrode group, variations occur in the distance between the positive electrode and the negative electrode in the electrode group. In this case, charging is likely to occur in the portion where the distance between the positive electrode and the negative electrode is short, and charging is difficult to occur in the portion where the distance between the positive electrode and the negative electrode is long. As a result, the battery capacity decreases each time the charge-discharge cycle is repeated. Also, in the case where the secondary battery is a lithium-ion secondary battery, lithium metal may be locally deposited on the surface of the negative electrode disposed in the portion of the electrode group where charging is likely to occur (the portion where the amount of charging electricity is locally large). The deposited lithium metal may react with the electrolyte contained in the electrolytic solution as the battery temperature rises. And this may cause the thermal stability of the battery after the charge-discharge cycle to decrease. Therefore, it is preferable that buckling of the electrode group can be detected as an abnormality of the secondary battery.

[0026] In this case, when charging a secondary battery, if buckling does not occur in the electrode group, the electrode group tends to continuously expand toward the outer casing (outward) due to the deposition of lithium metal or the expansion of the negative electrode active material. Therefore, the strain value of the outer casing tends to increase continuously. On the other hand, if buckling occurs in the electrode group, the buckled portion of the electrode group is less likely to expand toward the outer casing. Therefore, when buckling occurs in the electrode group, the strain value of the outer casing exhibits a discontinuous decrease.

[0027] As described above, the anomaly detection system of this disclosure comprises a sensor element disposed on the outer surface of the secondary battery casing and capable of detecting the strain value of the casing, and a data processing unit that determines the secondary battery is abnormal when the strain value detected by the sensor element decreases discontinuously during charging. Therefore, it is possible to detect buckling in the electrode group of the secondary battery during charging. Whether the secondary battery is charging or discharging can be confirmed by referring to the charge / discharge data. For this reason, the charge / discharge data of the secondary battery may be associated with the strain value detected by the sensor element. The configuration of the sensor element and the data processing unit will be described later.

[0028] The following provides a more detailed explanation of each component of a lithium-ion secondary battery.

[0029] <Negative Electrode> The negative electrode is equipped with a negative electrode current collector. The negative electrode current collector is preferably in the shape of a strip. In the case of a lithium secondary battery, lithium metal is deposited on the surface of the negative electrode current collector. Specifically, lithium ions contained in the non-aqueous electrolyte receive electrons on the surface of the negative electrode current collector during charging, becoming lithium metal, and are deposited on the surface of the negative electrode current collector. The lithium metal deposited on the surface of the negative electrode current collector dissolves into the non-aqueous electrolyte as lithium ions during discharge. The lithium ions contained in the non-aqueous electrolyte may originate from lithium salts added to the non-aqueous electrolyte, or they may be supplied from the positive electrode active material during charging, or both.

[0030] In the case of a lithium secondary battery, if the lithium secondary battery is a lithium metal secondary battery, the negative electrode current collector may be provided with a pre-existing underlayer containing lithium metal (a layer of lithium metal or lithium alloy (hereinafter also referred to as the lithium underlayer)). The lithium alloy may contain elements other than lithium, such as aluminum, magnesium, indium, and zinc. Thus, the proportion of lithium metal in the total lithium (at least one of the lithium metal and lithium alloy that functions as the negative electrode active material), including the lithium underlayer placed in the negative electrode current collector, may be 92% by mass or more. The above proportion of lithium metal can be determined, for example, by analyzing the negative electrode taken from the wound electrode using NMR (nuclear magnetic resonance) and based on the analysis results. Specifically, after determining the area P1 of the ionized lithium peak and the area P2 of the unionized lithium peak from the analysis results obtained by NMR analysis, the above proportion of lithium metal can be calculated using the formula: P2 / (P1+P2). By providing a lithium underlayer, lithium metal can be deposited on the surface of the lithium underlayer during charging. This makes it possible to suppress the deposition of lithium metal in a dendrite-like manner in the negative electrode current collector.

[0031] In the case of a lithium-ion secondary battery, the negative electrode includes a lithium-ion storage layer supported on the negative electrode current collector. The lithium-ion storage layer contains a negative electrode active material such as graphite, and this negative electrode active material absorbs and releases lithium ions, thereby generating capacity. Even in this case, if the open-circuit potential of the negative electrode at full charge is 70 mV or less relative to the lithium metal (lithium dissolution and release potential), lithium metal is present on the surface of the lithium-ion storage layer at full charge. In other words, the negative electrode generates capacity through the deposition and dissolution of lithium metal.

[0032] A lithium-ion storage layer is formed by creating a layer of negative electrode mixture containing a negative electrode active material. Therefore, the lithium-ion storage layer is also called a negative electrode mixture layer. In addition to the negative electrode active material, the negative electrode mixture may also contain binders, thickeners, and conductive agents.

[0033] Examples of negative electrode active materials include carbonaceous materials, silicon (Si)-containing materials, and tin (Sn)-containing materials. The lithium-ion storage layer may contain one type of negative electrode active material alone, or it may contain two or more types in combination. Examples of carbonaceous materials include graphite, easily graphitizable carbon (soft carbon), and poorly graphitizable carbon (hard carbon).

[0034] Examples of conductive materials include carbon materials. Examples of carbon materials include carbon black, carbon nanotubes, and graphite. Examples of carbon black include acetylene black and Ketjenblack.

[0035] Examples of binders include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubbery polymers. Examples of fluororesins include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF).

[0036] The negative electrode current collector can be made of a conductive sheet. Examples of conductive sheets include foil and film.

[0037] The negative electrode current collector may be made of a conductive material other than lithium metal or a lithium alloy. The conductive material may be a metallic material other than lithium metal or a lithium alloy. Preferably, the conductive material is a material that does not react with lithium. Specifically, it is preferable that the material does not form alloys with lithium or intermetallic compounds with lithium. Examples of such conductive materials include copper (Cu), nickel (Ni), iron (Fe), and alloys containing these metallic elements. The conductive material may also be graphite with a preferentially exposed basal surface. Examples of alloys include copper alloys and stainless steel (SUS). From the viewpoint of exhibiting high conductivity, it is preferable to use at least one of copper and copper alloys as the conductive material.

[0038] The thickness of the negative electrode current collector is not particularly limited. For example, the thickness of the negative electrode current collector is 5 μm or more and 300 μm or less.

[0039] <Positive Electrode> The positive electrode comprises, for example, a positive electrode current collector and a positive electrode mixture layer supported by the positive electrode current collector. The positive electrode current collector is preferably in the shape of a strip. The positive electrode mixture layer includes, for example, a positive electrode active material, a conductive agent, and a binder. The positive electrode mixture layer may be formed on only one side of the positive electrode current collector, or on both sides of the positive electrode current collector. The positive electrode can be formed, for example, by preparing a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder, applying this positive electrode mixture slurry to at least one surface of the positive electrode current collector to obtain a coating, drying this coating, and then rolling the dried coating.

[0040] The positive electrode active material is a material capable of intercalating and releasing lithium ions. Examples of positive electrode active materials include lithium transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides. From the viewpoint of low manufacturing costs and high average discharge voltage, it is preferable to use lithium transition metal oxides as the positive electrode active material.

[0041] During charging, lithium contained in lithium transition metal oxides is released from the positive electrode as lithium ions and deposited as lithium metal on the negative electrode or negative electrode current collector. Conversely, during discharge, lithium ions are released from the negative electrode as lithium metal dissolves and are absorbed into the lithium transition metal oxide of the positive electrode. Therefore, the lithium ions involved in charging and discharging generally originate from the solute contained in the non-aqueous electrolyte and the positive electrode active material.

[0042] Examples of transition metal elements included in lithium transition metal oxides include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, and W. Lithium transition metal oxides may contain one of the above transition metals alone or in combination of two or more. The transition metal element may be at least one selected from the group consisting of Co, Ni, and Mn. Lithium transition metal oxides may optionally contain one or more typical elements. Examples of typical elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, and Bi. Lithium transition metal oxides may contain Al as a typical metal element.

[0043] From the viewpoint of obtaining high capacity, among lithium transition metal oxides, a composite oxide is preferred that contains at least one transition metal element selected from the group consisting of Co, Ni, and Mn, and has a rock salt-type crystalline structure with a layered structure. This composite oxide may also contain Al, a typical metal element, as an optional component. In this case, in a lithium secondary battery, the ratio of the total molar amount of lithium (mLi / mM) contained in the positive and negative electrodes to the molar amount of metal M other than lithium contained in the positive electrode (mM) is set to, for example, 1.1 or less.

[0044] For example, those exemplified for the negative electrode can be used as the binder and conductive agent.

[0045] The positive electrode current collector may also be constructed as a conductive sheet. Examples of conductive sheets include foil and film. Examples of conductive materials for forming the positive electrode current collector include metallic materials containing aluminum (Al), titanium (Ti), and iron (Fe). The metallic material may be Al, Al alloy, Ti, Ti alloy, and Fe alloy. The Fe alloy may be stainless steel (SUS).

[0046] The thickness of the positive electrode current collector is not particularly limited. For example, the thickness of the positive electrode current collector is 5 μm or more and 300 μm or less.

[0047] <Separator> As the separator, a porous sheet having ion permeability and insulating properties can be used. Examples of porous sheets include thin films, woven fabrics, and nonwoven fabrics having microporous properties. The materials constituting the separator are not particularly limited. For example, polymer materials can be used as materials constituting the separator. Examples of polymer materials include polyolefin resins, polyamide resins, and cellulose. Examples of polyolefin resins include polyethylene, polypropylene, and copolymers of ethylene and propylene. The separator may contain additives as needed. Examples of additives include inorganic fillers.

[0048] The thickness of the separator is not limited. The thickness of the separator is, for example, 5 μm or more and 20 μm or less, and preferably 10 μm or more and 20 μm or less.

[0049] <Non-aqueous electrolytes> Non-aqueous electrolytes are lithium ion conductive. Non-aqueous electrolytes include, for example, a non-aqueous solvent, lithium ions, and anions. In non-aqueous electrolytes, the lithium ions and anions are dissolved in the non-aqueous solvent. Non-aqueous electrolytes may be liquid or gel-like.

[0050] Liquid non-aqueous electrolytes can be prepared by dissolving a lithium salt in a non-aqueous solvent. When a lithium salt dissolves in a non-aqueous solvent, lithium ions and anions are generated. Liquid non-aqueous electrolytes are also referred to as non-aqueous electrolyte solutions.

[0051] The gel-like non-aqueous electrolyte comprises a lithium salt and a matrix polymer, or a lithium salt, a non-aqueous solvent, and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs the non-aqueous solvent and gels can be used. Examples of such polymer materials include fluororesins, acrylic resins, and polyether resins.

[0052] As the anion, various known anions used in non-aqueous electrolytes of lithium secondary batteries can be used. Specifically, as the anion, BF ４－ , ClO ４ － , PF ６ － , CF ３ SO ３ － , CF ３ CO ２ － , anions of imides, anions of oxalate complexes, and the like. These anions may form salts with lithium ions as cations. That is, the above anions may be used in a state contained in a lithium salt. Examples of the anion of imides include, for example, N(SO ２ CF ３ ), and N(C ２ － , and the like. However, m and n are each independently an integer of 0 or 1 or more, x and y are each independently 0, 1, or 2, and x + y = 2. The anion of the oxalate complex may contain at least one of boron and phosphorus. Examples of the anion of the oxalate complex include, for example, bisoxalate borate anion, BF ｍ F ２ｍ＋１ SO ２ ), and the like. The non-aqueous electrolyte may contain one of these anions alone or a combination of two or more. ｘ (C ｎ F ２ｎ＋１ SO ２ ), and the like. However, m and n are each independently an integer of 0 or 1 or more, x and y are each independently 0, 1, or 2, and x + y = 2. The anion of the oxalate complex may contain at least one of boron and phosphorus. Examples of the anion of the oxalate complex include, for example, bisoxalate borate anion, BF ｙ － Such as. However, m and n are each independently an integer of 0 or 1 or more, x and y are each independently 0, 1, or 2, and x + y = 2. The anion of the oxalate complex may contain at least one of boron and phosphorus. Examples of the anion of the oxalate complex include, for example, bisoxalate borate anion, BF ２ (C<​​​​​​​​​​​​​​​​​​​​​​​​The non-aqueous electrolyte preferably contains an oxalate complex anion as the anion. This makes it easier for lithium metal to precipitate in the form of fine parts, thus suppressing the dendritic deposition of lithium metal. Among the oxalate complex anions, the non-aqueous electrolyte more preferably contains an oxalate complex anion that contains fluorine in its structure. This makes it even easier for lithium metal to precipitate in the form of fine parts.

[0054] Examples of non-aqueous solvents include esters, ethers, nitriles, amides, or halogen-substituted versions thereof. The non-aqueous electrolyte may contain one of the above non-aqueous solvents alone or a combination of two or more. Examples of halogen-substituted versions include fluorides.

[0055] Examples of esters include carbonate esters and carboxylic acid esters. Examples of carbonate esters include cyclic carbonate esters and linear carbonate esters, and examples of carboxylic acid esters include cyclic carboxylic acid esters and linear carboxylic acid esters. Examples of cyclic carbonate esters include ethylene carbonate, propylene carbonate, and fluoroethylene carbonate (FEC). Examples of linear carbonate esters include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate. Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone. Examples of linear carboxylic acid esters include ethyl acetate, methyl propionate, and methyl fluoropropionate.

[0056] Examples of ethers include cyclic ethers and linear ethers. Examples of cyclic ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of linear ethers include 1,2-dimethoxyethane, diethyl ether, ethyl vinyl ether, methylphenyl ether, benzyl ethyl ether, diphenyl ether, dibenzyl ether, 1,2-diethoxyethane, and diethylene glycol dimethyl ether.

[0057] The concentration of lithium salt in a non-aqueous electrolyte is, for example, between 0.5 mol / L and 3.5 mol / L.

[0058] The non-aqueous electrolyte may contain additives. The additives may form a film on the surface of the negative electrode. The formation of a film derived from the additive on the surface of the negative electrode makes it easier to suppress the dendritic deposition of lithium metal at the negative electrode. Examples of such additives include vinylene carbonate, FEC, and vinyl ethyl carbonate (VEC).

[0059] (Sensor element) The sensor element is placed on the outer surface of the secondary battery's casing. The sensor element is capable of detecting the strain value of the casing.

[0060] Examples of sensor elements include strain gauges. A strain gauge is a sensor that detects whether or not the casing of a secondary battery expands and contracts, or the degree of expansion and contraction of the casing of a secondary battery. A strain gauge comprises, for example, a substrate, a resistor disposed on one surface of the substrate, a pair of electrodes disposed on one side of the substrate, and a pair of wires disposed on one side of the substrate and electrically connecting the pair of electrodes and the resistor.

[0061] The substrate is a component that serves as a base layer for forming resistors and the like. The substrate is flexible. The thickness of the substrate is not particularly limited. For example, the thickness of the substrate is 5 μm to 500 μm. Because the substrate is flexible, it can be attached to the outer surface of the outer casing with the strain gauge wrapped around it so as to conform to the outer surface of the outer casing.

[0062] As a base material, for example, an insulating resin film can be used. Examples of resins for forming the insulating resin film include polyimide (PI) resin, epoxy resin, polyetheretherketone (PEEK) resin, polyethylene naphthalate (PEN) resin, polyethylene terephthalate (PET) resin, polyphenylene sulfite (PPS) resin, liquid crystal polymer (LCP) resin, and polyolefin resin.

[0063] If the substrate is an insulating resin film, this insulating resin film may contain an inorganic filler such as silica or alumina. Also, the substrate may contain SiO ２ , ZrO ２ (Including YSZ), Si, SI ２ N ３ Al ２ O ３ (Including sapphire), ZnO, and perovskite ceramics (CaTiO) ３ , BaTiO ３ They may also be formed using crystalline materials such as ).

[0064] A resistor is a thin film formed in a predetermined pattern on one surface of a substrate. If the substrate has a strip shape, the predetermined pattern may be a meandering pattern extending from one end to the other in the short direction of the substrate. In this case, one end of the resistor may be positioned on one end of the substrate in the long direction, and the other end of the resistor may be positioned on the other end of the substrate in the long direction. One electrode is positioned on one end of the resistor, and the other electrode is positioned on the other end of the resistor. One electrode is electrically connected to one end of the resistor by one wire, and the other electrode is electrically connected to the other end of the resistor by the other wire.

[0065] In a strain gauge, the resistor is a sensitive element that undergoes a change in resistance when subjected to strain. The resistor may be formed directly on one surface of the substrate, or it may be formed via another layer.

[0066] The resistor can be formed using, for example, a material containing chromium (Cr), a material containing nickel (Ni), or a material containing both Cr and Ni. That is, the resistor can be formed using a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr multiphase film. An example of a material containing Ni is Cu-Ni (copper-nickel), and an example of a material containing both Cr and Ni is Ni-Cr (nickel-chromium). Note that a Cr multiphase film is made of Cr, CrN, and Cr ２ This refers to a film in which N and other elements are mixed in phase.

[0067] The thickness of the resistor is not particularly limited. For example, the thickness of the resistor is 0.05 μm to 2 μm.

[0068] A pair of wires are arranged on one surface of the substrate. The wires electrically connect the resistor and the electrode. Specifically, as described above, one wire electrically connects one end of the resistor to one electrode, and the other wire electrically connects the other end of the resistor to the other electrode. The shape of the wires is not particularly limited. The wires may be formed in a straight line or to have any pattern. The wires may be formed to have any width and length.

[0069] A pair of electrodes are placed on one surface of the substrate. One electrode is positioned at one end of the resistor, and the other electrode is positioned at the other end of the resistor. As described above, the electrodes are electrically connected to the resistor via wiring. The electrodes are formed in a rectangular shape, for example, with a width wider than the wiring in a plan view. The electrodes output the change in the resistance value of the resistor caused by strain.

[0070] (Data Processing Unit) The data processing unit determines that a secondary battery is abnormal when the strain value detected by the sensor element during charging of the secondary battery decreases discontinuously. A discontinuous decrease means that the strain value, which had been continuously rising during the charging of the secondary battery, suddenly decreases at a certain point. Note that the concept of a continuously rising strain value also includes cases where, during charging, the strain value at a certain point in time is lower than the strain value at the previous point in time, but the overall strain value tends to increase. An example of the data processing unit will be explained below with reference to Figure 1.

[0071] As shown in Figure 1, the data processing unit 300 includes an analog front-end (AFE) unit 310 and a control unit 320. As shown in Figure 1, the AFE unit 310 is an analog circuit that connects a signal detection device (for example, a sensor element 200) to the control unit 320. Although only one sensor element 200 is shown in Figure 1, there may be multiple sensor elements 200 (two or more). That is, multiple sensor elements 200 may be connected to the AFE unit 310.

[0072] The AFE unit 310 includes, for example, a bridge circuit, an amplification circuit, and an analog-to-digital (A / D) conversion circuit, and generates a distortion waveform based on, for example, the output of the sensor element 200 (the output corresponding to the distortion value of the exterior body detected by the sensor element 200). The AFE unit 310 may be an integrated circuit (IC) or it may be configured as individual components. When multiple sensor elements 200 are each connected to the AFE unit 310, the bridge circuit may be provided in a number corresponding to the multiple sensor elements 200, or only one bridge circuit may be provided that is shared by the multiple sensor elements 200.

[0073] In the AFE unit 310, a strain waveform corresponding to the output of a sensor element 200 (for example, a strain gauge) arranged on the outer surface of the secondary battery casing is output as an analog signal from the bridge circuit. This analog signal is amplified by an amplification circuit, and then the amplified analog signal is converted into a digital signal by an A / D conversion circuit and output to the control unit 320.

[0074] The control unit 320 monitors the expansion and contraction of the secondary battery casing based on the digitized strain waveform sent from the AFE unit 310. The control unit 320 determines the secondary battery to be abnormal when the strain value decreases discontinuously in the portion of the strain waveform corresponding to the charging period. Preferably, the control unit 320 determines the secondary battery to be abnormal when the strain value becomes 0 during charging, or when the strain value at a certain point in time decreases by 60% or more compared to the strain value at the point immediately preceding that point. This allows for accurate determination of secondary battery abnormalities. Furthermore, it is preferable that the maximum value of the strain value detected during charging is 20 με or more. A maximum value of 20 με or more makes it easier to detect discontinuous decreases in strain value. The upper limit of the maximum value of the strain value is, for example, 60 με. Furthermore, the minimum value of the strain value detected during charging may be 1 με or more. The difference between the maximum value and the minimum value of the strain value may be 10 με or more and 55 με or less. The upper limit of the minimum strain value is, for example, 10 με.

[0075] As shown in Figure 1, the control unit 320 may be connected to, for example, a circuit breaker 400. The circuit breaker 400 is normally in a conductive state and can be switched to a circuit breaker state based on an external control signal. Therefore, the circuit breaker 400 can switch between a conductive state and a circuit breaker state of the secondary battery. Figure 1 shows an example in which one circuit breaker 400 is connected to the control unit 320, but multiple circuit breaker 400s may be connected to the control unit 320. The circuit breaker 400 will be described later.

[0076] Figure 2 is an example of a hardware block diagram of the control unit. As shown in Figure 2, the control unit 320 has as its main components a CPU 321, a ROM 322, a RAM 323, an interface (I / F) 324, and a bus line 325. The CPU 321, ROM 322, RAM 323, and I / F 324 are connected to each other via the bus line 325.

[0077] The CPU 321 controls the various functions of the control unit. The ROM 322 and RAM 323 are storage means. The ROM 322 stores programs executed by the CPU to control the various functions of the control unit, as well as various other information. The RAM 323 is used as a work area for the CPU 321 and also temporarily stores predetermined information. The I / F 324 is an interface for connecting the control unit 320 to other devices, such as the AFE unit 310 or an external network.

[0078] The control unit 320 may be a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, or it may be various integrated circuits designed to perform predetermined functions. Examples of various integrated circuits include ASIC (Application Specific Integrated Circuit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), SOC (System On a Chip), and GPU (Graphics Processing Unit). The control unit 320 may also be a circuit module or the like.

[0079] In the above explanation, the sensor element was described using a strain gauge having a resistor as the sensing element, i.e., an electrical resistance type metal strain gauge, as an example. However, the sensor element is not limited to a metal strain gauge. The strain gauge may be a strain gauge that senses magnetic changes caused by the strain of the casing of a secondary battery, a semiconductor type strain gauge that detects strain using the pressure resistance effect of a semiconductor, or an optical fiber type strain gauge that detects strain using an optical fiber.

[0080] Furthermore, the sensor element may be any known pressure sensor. Examples of pressure sensors include capacitive pressure sensors, mechanical pressure sensors, vibratory pressure sensors, and piezoelectric pressure sensors.

[0081] Capacitive pressure sensors measure the pressure applied to a diaphragm as a change in the capacitance of a pair of electrodes. Mechanical pressure sensors determine the pressure applied to a mechanical structure by measuring its displacement. Vibration pressure sensors detect pressure by utilizing the phenomenon that the natural frequency of an elastic beam changes due to the pressure (i.e., axial force) generated along the axis of the elastic beam. Piezoelectric pressure sensors contain a piezoelectric element (also called a piezo-piezoelectric element) and detect pressure using the properties of this piezoelectric element. A piezoelectric element has the property of generating an electromotive force corresponding to the force applied when it deforms (strains), and also has the property of expanding and contracting by generating a force corresponding to the voltage applied.

[0082] [Energy Storage Module] An energy storage module according to the embodiment of the present disclosure comprises a plurality of secondary batteries, each having an electrode group around which a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode are wound, and an outer casing housing the electrode group; a sensor element disposed on the outer circumferential surface of the outer casing of at least one secondary battery and capable of detecting at least one strain value; a data processing unit that determines a secondary battery to be abnormal when the strain value detected by the sensor element decreases discontinuously during charging of at least one secondary battery; and a shut-off mechanism that shuts off the secondary battery determined to be abnormal by the data processing unit from the other secondary batteries.

[0083] In the following, with reference to the drawings, a battery module comprising a plurality of lithium secondary batteries will be specifically described as an energy storage module according to the embodiment of this disclosure. The components described above can be applied to the components of the battery module. Furthermore, the components of the battery module described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Note that, in the drawings, reference numerals may be omitted as appropriate from the viewpoint of readability.

[0084] (Embodiment 1) Figure 3 is a schematic cross-sectional view showing a part of the battery module 100 according to Embodiment 1. Figure 4 is a cross-sectional view taken along line IV-IV of a part of the battery module 100 shown in Figure 3. Figure 4 is also a transverse cross-sectional view taken in a direction perpendicular to the axial direction of the battery (lithium secondary battery). Figure 5 is a schematic front view showing a cross-sectional view of a part of an example of the lithium secondary battery 10 provided in the battery module 100.

[0085] The battery module 100 includes a battery group 10G containing a plurality of lithium secondary batteries 10, and a holder 110 that houses the plurality of lithium secondary batteries 10. Each of the plurality of lithium secondary batteries 10 has an electrode group. The plurality of lithium secondary batteries 10 are arranged so that the winding axes of each electrode group are oriented in one direction. In other words, the plurality of lithium secondary batteries 10 are arranged so that the axes of the batteries are oriented in one direction. The holder 110 includes a first holder 111 and a second holder 112. The battery module 100 also includes an outer case that houses the holder 110 and conductive members connected to the positive and negative terminals of the lithium secondary batteries 10, but these are not shown in the illustration.

[0086] Referring to Figures 3 and 4, the multiple lithium secondary batteries 10 are arranged in a matrix within the holder 110. The multiple lithium secondary batteries 10 are usually arranged within the holder 110 so that they do not come into contact with each other. In other words, the multiple lithium secondary batteries 10 are arranged so that adjacent lithium secondary batteries 10 are spaced apart by a predetermined distance.

[0087] As shown in Figure 5, the lithium secondary battery 10 has a cylindrical shape. The lithium secondary battery 10 includes a first end 10a located on one end of the cylindrical body and a second end 10b located on the other end of the cylindrical body. The other end of the cylindrical body is located on the opposite side of the one end of the cylindrical body. The first end 10a and the second end 10b are two ends of the lithium secondary battery 10 along the longitudinal direction LD. The orientation of the batteries at the ends of the multiple lithium secondary batteries 10 (for example, which direction the sealing body is facing) may be the same or different between the batteries. The longitudinal direction LD is also the height direction of the cylindrical lithium secondary battery 10. In the battery module 100, the longitudinal direction LD is perpendicular to the direction in which the multiple lithium secondary batteries 10 are arranged.

[0088] The lithium secondary battery 10 includes an electrode group 20 and a non-aqueous electrolyte (not shown). The electrode group 20 includes a strip-shaped positive electrode 21, a strip-shaped negative electrode 22, and a separator 23. The separator 23 is positioned between the positive electrode 21 and the negative electrode 22. A positive electrode lead 21a is connected to the positive electrode 21, and a negative electrode lead 22a is connected to the negative electrode 22. The positive electrode 21 includes a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector. The negative electrode 22 includes a negative electrode current collector. If the lithium secondary battery 10 is a lithium-ion secondary battery, a negative electrode mixture layer is disposed on the negative electrode current collector. If the lithium secondary battery 10 is a lithium metal secondary battery, a lithium underlayer may be disposed on the negative electrode current collector.

[0089] One end of the positive lead 21a is connected to the positive electrode 21, and the other end of the positive lead 21a is connected to the sealing body 50. The sealing body 50 includes the positive terminal 50a. The sealing body 50 typically includes a mechanism that functions as a safety valve when the internal pressure of the battery rises.

[0090] One end of the negative electrode lead 22a is connected to the negative electrode 22 (specifically, the negative electrode current collector), and the other end of the negative electrode lead 22a is connected to the bottom of the cylindrical portion 60. The cylindrical portion 60 functions as a negative electrode terminal. The cylindrical portion 60 is a bottomed cylindrical can. The cylindrical portion 60 has a ring-shaped groove 60c formed on the first end 10a side.

[0091] An upper insulating ring 81 made of resin is positioned above the electrode group 20, and a lower insulating ring 82 made of resin is positioned below the electrode group 20. The cylindrical portion 60 is sealed by a sealing body 50 and a gasket 70. The cylindrical portion 60, sealing body 50, and gasket 70 constitute a battery case. The electrode group 20 and a non-aqueous electrolyte are housed in this battery case.

[0092] The first holder 111 has a plate-like portion (flat plate portion) 111p and an outer wall 111w extending from the peripheral edge of the plate-like portion 111p. The outer wall 111w is arranged to surround most of the outer surfaces of the multiple lithium secondary batteries 10. The second holder 112 has a plate-like portion (flat plate portion) 112p. The second holder 112 also functions as a lid member that covers the upper opening of the first holder 111 which houses each of the multiple lithium secondary batteries 10. The first holder 111 and the second holder 112 may be fixed to each other by bolts or the like.

[0093] The first holder 111 and the second holder 112 each have a first opening 111a and a second opening 112a that connect the inside and outside of the holder 110, respectively, at positions facing the first end 10a and the second end 10b of the lithium secondary battery 10. The first end 10a side of the lithium secondary battery 10 is exposed through the first opening 111a, and the second end 10b side of the lithium secondary battery 10 is exposed through the second opening 112a.

[0094] Ribs are provided on the plate-shaped portion 111p of the first holder 111 so as to surround the first opening 111a, and these ribs form the first housing portion 111c. The first end portion 10a of the lithium secondary battery 10 is housed in the first housing portion 111c, and the first end portion 10a is held by the first holder 111.

[0095] Similarly, the plate-shaped portion 112p of the second holder 112 is provided with ribs surrounding the second opening 112a, and these ribs form a second housing portion 112c. The second end portion 10b of the lithium secondary battery 10 is housed in the second housing portion 112c, and the second end portion 10b is held by the second holder 112.

[0096] The battery module 100 includes a sensor element 200 that is positioned on the outer circumferential surface of the outer casing (cylindrical portion 60) of at least one lithium secondary battery 10. In the example shown in Figures 3 and 4, the sensor element 200 is positioned on the outer circumferential surface of each of the outer casings (cylindrical portions 60) of multiple lithium secondary batteries 10. The sensor element 200 is a sensor element capable of detecting the strain value of the outer casing. In Figures 3 and 4, an example is shown in which a strain sensor having a flexible substrate is used as the sensor element 200. Therefore, the sensor element 200 is positioned on the outer circumferential surface of the cylindrical portion 60 in a state where it is wrapped along the outer circumferential surface of the cylindrical portion 60. On the other hand, the sensor element 200 does not have to be positioned on all of the outer circumferential surfaces of the outer casings of multiple lithium secondary batteries 10. For example, the sensor element 200 may be positioned on the outer circumferential surface of the outer casing of a lithium secondary battery 10 located in a location where heat generation is likely to occur, and on the outer circumferential surface of the outer casing of a lithium secondary battery 10 located in a location where current concentration is likely to occur.

[0097] The sensor element 200 detects the strain value on the outer surface of the casing of the lithium secondary battery 10 in which it is placed. That is, the sensor element 200 is capable of detecting at least one strain value. The battery module 100 includes a data processing unit (not shown) that determines that the lithium secondary battery 10 is abnormal based on the strain value detected by the sensor element 200. Specifically, the data processing unit determines that the lithium secondary battery 10 is abnormal when the strain value detected by the sensor element 200 decreases discontinuously. Preferably, the data processing unit determines that a lithium secondary battery 10 is abnormal if, during the charging of at least one lithium secondary battery 10, the strain value of that lithium secondary battery 10 has become 0, or if the strain value at a certain point in time has decreased by 60% or more compared to the strain value at the point immediately preceding that point. This allows for accurate determination of abnormalities in the lithium secondary battery 10. The configuration of the sensor element 200 and the data processing unit has been described above, so that description will not be repeated here.

[0098] The battery module 100 includes a shut-off mechanism (not shown) that isolates a lithium secondary battery 10 that has been determined to be abnormal by the data processing unit from other lithium secondary batteries 10. In the battery module 100, the output of a sensor element 200 arranged on the outer surface of the casing of the lithium secondary battery 10 is input to the data processing unit. The shut-off mechanism is connected to a control unit provided in the data processing unit, for example, as described above. Therefore, the shut-off mechanism functions to isolate a lithium secondary battery 10 that has been determined to be abnormal by the data processing unit. This isolates a lithium secondary battery 10 in which buckling has occurred in the electrode group, thereby reducing the risk of continuing to use a lithium secondary battery 10 whose battery capacity decreases with each charge-discharge cycle, or a lithium secondary battery 10 with reduced thermal stability.

[0099] The interruption mechanism is located, for example, in a conductive member (e.g., wiring) connecting the electrode terminals of the lithium secondary battery 10 of the battery module 100 to external terminals. The interruption mechanism is normally in a conductive state and can be switched to an interrupted state based on an external control signal. The interruption mechanism is, for example, an externally controllable switch. Specifically, the interruption mechanism may be a mechanical switch such as a relay, or an electronic switch equipped with a transistor or the like.

[0100] (Embodiment 2) Figure 6 is a cross-sectional view of a portion of the batteries in the battery module 100 according to Embodiment 2, perpendicular to the axial direction of the batteries. The battery module 100 according to Embodiment 2 has the same configuration as the battery module 100 according to Embodiment 1, except that the lithium secondary batteries 10 are arranged in a staggered pattern in the holder 110. By arranging the lithium secondary batteries 10 in a staggered pattern, the energy density per unit volume of the battery module 100 can be increased compared to when the lithium secondary batteries 10 are arranged in a matrix.

[0101] Specifically, in the battery module 100 according to Embodiment 2, each of the multiple rows containing multiple lithium secondary batteries 10 is arranged so as to be aligned along a direction perpendicular to the row. In each row, the multiple lithium secondary batteries 10 are arranged at approximately equal intervals along the row direction. In two adjacent rows, the positions of the lithium secondary batteries 10 are offset along the row direction. In two adjacent rows separated by one row, the positions of the lithium secondary batteries 10 are the same in the row direction. In one example, a staggered arrangement is an arrangement in which hexagons of the same shape are arranged to fill a plane without gaps, and lithium secondary batteries 10 are placed at the vertices and centers of the hexagons. The multiple lithium secondary batteries 10 are arranged so as not to touch each other.

[0102] [Method for Manufacturing Battery Modules] The method for manufacturing the battery modules of this disclosure is not particularly limited. An example of a method for manufacturing the battery module 100 is described below.

[0103] In one example of a method for manufacturing the battery module 100, first, the components necessary for manufacturing the battery module 100 are prepared. The first holder 111 and the second holder 112 can be formed, for example, by injection molding of the resin material.

[0104] Next, the first holder 111 is placed so that the plate-shaped portion 111p of the first holder 111 is facing downwards. Next, the first end portion 10a of the lithium secondary battery 10 is inserted into the first housing portion 111c of the first holder 111. At this time, the first holder 111 and the first end portion 10a may be fixed together with an adhesive or the like. Next, a sensor element 200 capable of detecting the strain value of the housing is attached to the outer circumferential surface of the housing for each of the multiple lithium secondary batteries 10. If the sensor element 200 has a flexible base material like a strain gauge, the sensor element 200 can be attached to the outer circumferential surface of the housing by wrapping it along the outer circumferential surface of the housing.

[0105] After attaching the sensor element, the first holder 111 and the second holder 112 are combined and fixed to obtain the holder 110. At this time, the second end 10b of the lithium secondary battery 10 is inserted into the second housing portion 112c of the second holder 112. At this time, the second holder 112 and the second end 10b may be fixed with adhesive or the like. Next, conductive members for charging and discharging are connected to the electrode terminals, and the sensor element 200 and the data processing unit are connected. Furthermore, after performing all of the above connections, the holder 110 is fixed to the outer case, and wiring and the like are performed as necessary. The data processing unit is located outside the outer case. In this way, the battery module 100 can be obtained.

[0106] (Note) The following technologies are disclosed in accordance with the above description. (Technology 1) An abnormality detection system for detecting an abnormality in a secondary battery having an electrode group around which a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode are wound, and an outer casing housing the electrode group, comprising: a sensor element arranged on the outer circumferential surface of the outer casing and capable of detecting the strain value of the outer casing; and a data processing unit that determines the secondary battery is abnormal when the strain value detected by the sensor element during charging of the secondary battery decreases discontinuously. (Technology 2) The abnormality detection system according to Technology 1, wherein the data processing unit determines the secondary battery is abnormal if the strain value becomes 0 during charging, or if the strain value at a certain point in time has decreased by 60% or more compared to the strain value at the point immediately preceding that point in time. (Technology 3) The abnormality detection system according to Technology 1 or 2, wherein the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal dissolves during discharge. (Technical 4) A power storage module comprising: a plurality of secondary batteries, each having a positive electrode, a negative electrode, and an electrode group around which a separator disposed between the positive electrode and the negative electrode is wound, and an outer casing housing the electrode group; a sensor element disposed on the outer circumferential surface of the outer casing of at least one of the secondary batteries and capable of detecting the strain value of at least one of the outer casings; a data processing unit that determines the secondary battery to be abnormal when the strain value detected by the sensor element decreases discontinuously during charging of the at least one secondary battery; and a shut-off mechanism that shuts off the secondary battery determined to be abnormal by the data processing unit from the other secondary batteries. (Technical 5) The power storage module according to Technical 4, wherein the data processing unit determines the secondary battery to be abnormal when the strain value becomes 0 during charging of the at least one secondary battery, or when the strain value at a certain point in time has decreased by 60% or more compared to the strain value at the point immediately preceding that point in time. (Technical 6) The energy storage module according to Technical 4 or 5, wherein the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal dissolves during discharge.

[0107] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0108] The anomaly detection system described in this disclosure can be used in applications where buckling of electrode groups is required to be detected as an anomaly in a secondary battery. The energy storage module described in this disclosure can also be used in the same applications as described above.

[0109] 10: Lithium secondary battery, 10a: First end, 10b: Second end, 10G: Battery group, 20: Electrode group, 60: Cylindrical part, 60c: Groove part, 100: Battery module, 110: Holder, 111: First holder, 111c: First housing part, 111a: First opening, 111w: Outer wall, 112: Second holder, 112c: Second housing part, 200: Sensor element, 300: Data processing unit, 400: Shut-off mechanism

Claims

1. An abnormality detection system for detecting an abnormality in a secondary battery having an electrode group around which a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode are wound, and an outer casing housing the electrode group, comprising: a sensor element arranged on the outer circumferential surface of the outer casing and capable of detecting the strain value of the outer casing; and a data processing unit that determines the secondary battery is abnormal when the strain value detected by the sensor element decreases discontinuously during charging of the secondary battery.

2. The abnormality detection system according to claim 1, wherein the data processing unit determines that a secondary battery is abnormal if the strain value becomes zero during charging, or if the strain value at a certain point in time is 60% or more lower than the strain value at the point immediately preceding that point in time.

3. The anomaly detection system according to claim 1 or 2, wherein the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal is dissolved during discharge.

4. A power storage module comprising: a plurality of secondary batteries, each having a positive electrode, a negative electrode, and an electrode group around which a separator disposed between the positive electrode and the negative electrode is wound, and an outer casing housing the electrode group; a sensor element disposed on the outer circumferential surface of the outer casing of at least one of the secondary batteries and capable of detecting the strain value of at least one of the outer casings; a data processing unit that determines the secondary battery to be abnormal when the strain value detected by the sensor element decreases discontinuously during charging of the at least one secondary battery; and a shut-off mechanism that shuts off the secondary battery determined to be abnormal by the data processing unit from the other secondary batteries.

5. The energy storage module according to claim 4, wherein the data processing unit determines that a secondary battery is abnormal if, during charging of at least one secondary battery, the strain value of that secondary battery becomes zero, or if the strain value of that secondary battery at a certain point in time is 60% or more lower than the strain value at the point immediately preceding that point in time.

6. The energy storage module according to claim 4 or 5, wherein the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal dissolves during discharge.

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