Secondary battery detection method and secondary battery

Abstract

The invention relates to a detection method of a secondary battery and the secondary battery. The present invention addresses the problem of efficiently performing short-circuit detection in a secondary battery at a location where the probability of short-circuit is high. A short-circuit inspection method for a secondary battery includes: measuring a first surface temperature, which is the temperature of an end surface of an electrode laminate; applying a current by connecting a charging / discharging probe to the positive electrode terminal and the negative electrode terminal of the electrode laminate; measuring a second surface temperature, which is the temperature of the end surface of the electrode laminate when the current is applied; and determining the presence or absence of a short circuit on the basis of the difference between the first surface temperature and the second surface temperature.

Description

Technical Field

[0001] This invention relates to a method for detecting secondary batteries and a secondary battery. Background Technology

[0002] In a secondary battery, if an internal short circuit occurs, a large current will flow, generating gas or heat, resulting in a rapid temperature rise. Patent Document 1 discloses the following method: detecting changes in internal temperature and comparing the rate of change with a reference value to determine an internal short circuit.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2002-008631 Summary of the Invention

[0004] In existing technologies, it is necessary to detect temperature changes inside the electrode body, which takes time. Furthermore, it is impossible to determine whether the short circuit occurred inside or on the surface of the electrode body.

[0005] Therefore, the objective of this invention is to efficiently detect short circuits in secondary batteries at locations with a high probability of short circuits.

[0006] This application discloses a short-circuit detection method for a secondary battery, which includes the following steps: measuring a first surface temperature, which is the temperature of the end face of an electrode stack; connecting a charge / discharge probe to the positive and negative terminals of the electrode stack and applying current; measuring a second surface temperature, which is the temperature of the end face of the electrode stack, while applying current; and determining whether a short circuit exists based on the difference between the first surface temperature and the second surface temperature.

[0007] The temperature of the first surface and the temperature of the second surface can be measured using a thermal imaging device.

[0008] The electrode stack can have a positive current collector layer, a positive active material layer, a solid electrolyte layer, a negative active material layer, and a negative current collector layer.

[0009] Furthermore, this application discloses a secondary battery that is tested using the aforementioned method for detecting short circuits in a secondary battery, and probe marks for charging and discharging probes are formed on the positive terminal connected to the positive current collector layer and the negative terminal connected to the negative current collector layer.

[0010] Invention Effects

[0011] By detecting the surface temperature of the end face (cut surface) of the electrode stack that is prone to short circuits during the manufacturing process, short circuit detection can be performed efficiently at locations with a high probability of short circuits. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating the layer structure of the solid-state battery 10.

[0013] Figure 2 This is a diagram illustrating a scenario of the short-circuit detection method S10 for secondary batteries.

[0014] Figure 3 This is a diagram illustrating another scenario of the short-circuit detection method S10 for secondary batteries. Detailed Implementation

[0015] 1. Battery structure

[0016] First, the structure of a secondary battery, which is the object of testing, will be explained. Figure 1 The diagram illustrates one form of solid-state battery (all-solid-state battery). Here, as a typical example, an all-solid-state battery is used for illustration; however, the present invention is not necessarily an all-solid-state battery and can be applied to any battery having an electrode body and an outer casing sealing the electrode body (e.g., a solid-state battery containing both a solid electrolyte and a liquid electrolyte (semi-solid-state battery) or a battery based solely on a liquid electrolyte). Figure 1 The diagram illustrates the layer structure of the electrode stack 11 included in a solid-state battery. By sealing this electrode stack 11 within an outer casing, the solid-state battery becomes a solid-state battery. For example, the electrode stack 11, which is approximately rectangular in plan view, is contained within an outer casing that is also approximately rectangular in plan view. In this case, a positive terminal extends from the positive current collector of the electrode stack 11, and a negative terminal extends from the negative current collector, with their front ends configured to protrude from the outer casing.

[0017] The following provides a more detailed explanation of the various structures of the electrode stack 11 and their relationships.

[0018] The electrode stack 11 has a positive current collector 12, a positive electrode flux layer 13, an electrolyte layer 14, a negative electrode flux layer 15, and a negative current collector 16. In this embodiment, the positive current collector 12, the positive electrode flux layer 13, the electrolyte layer 14, the negative electrode flux layer 15, and the negative current collector 16 are stacked sequentially to form a unit element 11a, and multiple units of this unit element 11a are stacked to form an electrode body 11 (in...). Figure 1 In the diagram, only one unit element 11a is shown. Moreover, as described above, the positive current collector 12 is electrically connected to the positive terminal of the electrode body 11, and the negative current collector 16 is electrically connected to the negative terminal of the electrode body 11.

[0019] 1.1. Positive current collector

[0020] The positive current collector 12 is stacked on the positive electrode flux layer 13, and current is collected from the positive electrode flux layer 13. In this embodiment, the positive current collector 12 is a quadrilateral foil in plan view, and can be composed of a positive current collector foil as a metal foil and a conductive resin layer or carbon layer stacked on the positive current collector foil. The positive current collector 12 is stacked on the positive electrode flux layer 13 by stacking a carbon layer on the positive electrode flux layer 13.

[0021] Materials used to form the positive current collector include, for example, stainless steel, nickel, chromium, gold, platinum, aluminum, iron, titanium, and zinc. These metal foils can also be formed by plating or vapor-depositing nickel, chromium, carbon, etc. The conductive resin layer can be composed of a resin in which conductive materials are dispersed, and the carbon layer can be composed of a material containing carbon.

[0022] 1.2. Positive electrode mixture layer

[0023] The aforementioned positive current collector 12 is stacked on one surface of the positive electrode mixture layer 13, and an electrolyte layer 14 is stacked on the other surface. In this embodiment, the positive electrode mixture layer 13 is a quadrilateral sheet when viewed from above. The positive electrode mixture layer 13 is a layer containing at least a positive electrode active material. Furthermore, as needed, the positive electrode mixture layer may contain at least one of an electrolyte, a conductive additive, and a binder.

[0024] The thickness of the positive electrode mixture layer 13 is not particularly limited, and can be set to 1 μm or more and 100 μm or less, more preferably 30 μm or more and 100 μm or less.

[0025] [Positive electrode active material]

[0026] Examples of positive electrode active materials include oxide active materials. Examples of ternary (Li(Ni)) active materials include... x Co y Mn z O2), NCA series (Li(Ni) x Co y Al z )O2), LiCoO2, LiMnO2, LiNiO2, LiVO2, Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other layered active substances in rock salt, LiMn2O4, Li4Ti5O 12 Li(Ni) 0.5 Mn 1.5 Spinel-type active substances such as O4, olivine-type active substances such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, and active substances composed of Li 1+x Mn 2-x-y My O4 (where M is one or more elements selected from Al, Mg, Co, Fe, Ni, and Zn) represents the substitution of Li-Mn spinel active materials with other elements, Li x TiO y .

[0027] A coating containing Li-ion-conducting oxides can be formed on the surface of the active material. This is because it can inhibit the reaction between the active material and the solid electrolyte (especially sulfide solid electrolytes). Examples of Li-ion-conducting oxides include LiNbO3 and Li4Ti5O3. 12 Li3PO4, etc.

[0028] The coating thickness is, for example, greater than 1 nm and less than 30 nm.

[0029] The shape of the positive electrode active material can be, for example, particulate. The average particle size (D50) of the positive electrode active material is not particularly limited; for example, it can be 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D50) of the positive electrode active material can be, for example, 50 μm or less, or 20 μm or less. The average particle size (D50) can be calculated, for example, by laser diffraction particle size analyzer or scanning electron microscope (SEM).

[0030] [Electrolytes]

[0031] In all-solid-state or semi-solid-state batteries, the electrolyte contains at least a solid electrolyte, but in semi-solid-state batteries or batteries based solely on electrolyte, a liquid electrolyte (electrolyte) is included.

[0032] Examples of solid-state electrolytes include inorganic solid-state electrolytes such as sulfide solid-state electrolytes, oxide solid-state electrolytes, nitride solid-state electrolytes, and halide solid-state electrolytes, as well as organic polymer electrolytes such as polymer electrolytes. Examples of sulfide solid-state electrolytes include those containing Li, X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. Furthermore, sulfide solid-state electrolytes may further contain at least one of O and a halogen element. Examples of halogen elements include F, Cl, Br, and I. Sulfide solid-state electrolytes can be glass (amorphous) or glass-ceramic. Examples of sulfide solid electrolytes include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2, and Li2S-P2S5-GeS2.

[0033] The electrolyte preferably contains a supporting salt and a solvent. Examples of supporting salts (lithium salts) for electrolytes with lithium-ion conductivity include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of solvents used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC). The electrolyte preferably contains two or more solvents.

[0034] The mass ratio of positive electrode active material to electrolyte is preferably 85 / 15 to 30 / 70, more preferably 80 / 20 to 50 / 50.

[0035] [Conductive additives / adhesives]

[0036] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), as well as fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs).

[0037] Furthermore, examples of adhesives include rubber-based adhesives and fluorinated adhesives.

[0038] 1.3. Electrolyte layer

[0039] The electrolyte layer 14 is formed between the positive electrode mixture layer and the negative electrode mixture layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte or may include a liquid electrolyte (electrolyte). The specific solid electrolyte and electrolyte are the same as those described in the positive electrode mixture layer above.

[0040] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less. More preferably, it is 0.1 μm or more and 300 μm or less, and even more preferably, it is 1 μm or more and 100 μm or less.

[0041] 1.4. Negative electrode mixture layer

[0042] The negative electrode mixture layer 15 is a layer containing at least a negative electrode active material, and may contain at least one of an electrolyte, a conductive additive, and a binder. The electrolyte, conductive additive, and binder are the same as those in the positive electrode mixture layer described above.

[0043] The thickness of the negative electrode mixture layer 15 is not particularly limited, and can be set to 1 μm or more and 100 μm or less, more preferably 30 μm or more and 100 μm or less.

[0044] [Negative Electrode Active Material]

[0045] The negative electrode active material uses a material that expands during charging. Specifically, there are no particular limitations.

[0046] However, examples include graphite, silicon, metallic lithium, and lithium titanate niobate.

[0047] 1.5. Negative current collector

[0048] The negative electrode current collector 16 is stacked on the negative electrode flux layer 15, and current is collected from the negative electrode flux layer 15. In this embodiment, the negative electrode current collector 16 is a quadrilateral foil shape when viewed from above, and can be made of, for example, stainless steel, copper, nickel, carbon, aluminum, and these alloys. Alternatively, it can be formed by plating or vapor-depositing nickel, chromium, or carbon on these materials.

[0049] 1.6. Positive and Negative Extremes

[0050] The positive and negative terminals are conductive components, serving as terminals for electrically connecting each electrode to the outside.

[0051] One end of the positive terminal is electrically connected to the positive current collector 12, and the other end passes through the outer casing and is exposed to the outside.

[0052] One end of the negative terminal is electrically connected to the negative current collector 16, and the other end passes through the outer casing and is exposed to the outside.

[0053] Furthermore, in the short-circuit detection method for secondary batteries described later, charging and discharging probes are connected to the positive and negative terminals, thus forming probe marks on them. These probe marks deform the surfaces of the positive and negative terminals, increasing their surface area and thereby improving heat dissipation performance.

[0054] 1.7. Exterior body

[0055] The outer casing is composed of a rectangular sheet-like component when viewed from above, for example, having a first sheet and a second sheet. An electrode body 11 is contained between the first sheet and the second sheet, and the outer peripheral ends of the first sheet and the second sheet are joined and sealed. Therefore, the outer casing is bag-shaped, and contains and seals the electrode body 11 within it.

[0056] The first sheet and the second sheet can be composed of a laminated film. Here, a laminated film refers to a film having a metal layer and a sealing material layer. Examples of metals used for the laminated film include aluminum and stainless steel, and examples of materials used for the sealing material layer include thermoplastic resins such as polypropylene, polyethylene, polystyrene, or polyvinyl chloride.

[0057] 1.8. Other

[0058] Regarding the stacked electrode body 11, it is formed by fabricating a large stacked body and cutting it during manufacturing, thus in the case of... Figure 1 In the cuboid shown, the end faces of each layer are exposed on four sides, which become the cut surfaces formed by cutting. A set of cut surfaces arranged on opposite sides of each other among the four cut surfaces ( Figure 1 A positive terminal and a negative terminal are provided on the cut surface (represented by A). Furthermore, the cut surface without positive and negative terminals is designated as B. Therefore, in this embodiment, cut surface B is a set of cut surfaces located on opposite sides of each other.

[0059] 2. Short-circuit detection method for secondary batteries

[0060] Next, a short-circuit detection method S10 for a secondary battery according to one embodiment will be described (hereinafter, sometimes referred to as "short-circuit detection method S10"). The short-circuit detection method S10 of this embodiment includes each process: first surface temperature measurement S11, current application S12, second surface temperature measurement S13, difference calculation S14, and short-circuit determination S15.

[0061] The following is a description of each process.

[0062] 2.1. Measurement of the first surface temperature

[0063] In the first surface temperature measurement S11, the temperature of the secondary cell is measured before the next current application S12. Figure 2 A summary diagram is shown in [the diagram]. Figure 2 Viewed from above, the four sides of the rectangle form the cut surfaces of the secondary battery. Figure 2 In the image, for ease of understanding, electrode stack 11 is shown, but it is actually covered by an outer casing.

[0064] Furthermore, the surface temperature measured here is the surface of the outer casing that is in contact with the cut surface B. That is, the surface that serves as the cut surface and is not equipped with electrode terminals is measured.

[0065] In this method, a thermal imaging device is used for measurement. The thermal imaging device enables non-contact image detection and allows for the assessment of the overall temperature state of the object surface, thus enabling accurate and efficient detection. However, other temperature measuring devices, different from or equivalent to the thermal imaging device, can be used.

[0066] 2.2. Current application

[0067] In current application S12, the charge / discharge probes are connected to the positive and negative terminals and a current is applied. Figure 3 A summary diagram is shown in the figure.

[0068] There is no particular limitation on the magnitude of the applied current, but it is approximately 2A to 30A. Furthermore, there is no particular limitation on the application time, which can be approximately 1 to 2 seconds.

[0069] In addition, the contact marks left on the positive and negative terminals by the charge / discharge probe, as mentioned above, contribute to heat dissipation.

[0070] 2.3. Measurement of the second surface temperature

[0071] In the second surface temperature measurement S13, the temperature of the secondary battery is measured after the current is applied in S12. The measurement location and method are preferably the same as those in the first surface temperature measurement S11.

[0072] 2.4. Difference Calculation

[0073] In the difference calculation S14, the difference between the temperatures measured in the first surface temperature measurement S11 and the second surface temperature measurement S13 is taken. When using a thermal imaging device or measuring the temperature at multiple points, for example, the difference is taken from the temperature of the location that has the highest temperature in the measured area. Furthermore, it is possible to measure multiple finely divided detection surfaces and compare the highest temperatures among the same detection surfaces. Thus, differences at approximately the same location can be obtained.

[0074] That is, when the temperature based on the first surface temperature measurement S11 is set as T1, and the temperature based on the second surface temperature measurement S13 is set as T2, the difference is taken by ΔT = T2 - T1. Since current is applied in S12, ΔT is usually greater than 0 regardless of whether there is a short circuit.

[0075] 2.5. Short Circuit Determination

[0076] In the short circuit determination S15, the value of ΔT obtained in the difference operation S14 is used to determine whether a short circuit has occurred. This determination can be made by setting a threshold for the magnitude of ΔT. The magnitude of the threshold varies depending on the type of battery, etc., so it can be obtained in advance through experiments and the resulting graphs can be created, or the data can be digitized.

[0077] Generally, if ΔT exceeds the threshold, a short circuit can be identified. The threshold is not specifically limited; for example, it can be set to around 5°C.

[0078] 3. Effects, etc.

[0079] This short-circuit detection method for secondary batteries enables efficient short-circuit detection at locations with high short-circuit probability by detecting the surface temperature of the end face (cut surface) of the electrode stack, which is prone to short circuits during the manufacturing process. Furthermore, it can not only detect short circuits but also monitor temperature changes during the initial charging process.

[0080] Symbol Explanation

[0081] 11-Electrode stack, 12-Positive current collector, 13-Positive electrolyte layer, 14-Solid electrolyte layer, 15-Negative electrolyte layer, 16-Negative current collector.

Claims

1. A short-circuit detection method for a secondary battery, characterized by, comprises the following steps: measuring a first surface temperature of an end surface of an electrode stack as a temperature of the end surface of the electrode stack; connecting a charge-discharge probe to a positive terminal and a negative terminal of the electrode stack and applying a current; measuring a second surface temperature of the end surface of the electrode stack as a temperature of the end surface of the electrode stack while the current is being applied; and determining the presence or absence of a short circuit based on a difference between the first surface temperature and the second surface temperature.

2. The short circuit detection method for a secondary battery according to claim 1, characterized in that: the measurement of the first surface temperature and the measurement of the second surface temperature are performed using a thermal imaging device.

3. The short circuit detection method for a secondary battery according to claim 1 or 2, characterized in that: the electrode stack has a positive current collector layer, a positive active material layer, a solid-state electrolyte layer, a negative active material layer, and a negative current collector layer. The short circuit detection method for a secondary battery according to claim 3 is performed to form a probe mark of the charge-discharge probe on the positive terminal connected to the positive current collector layer and the negative terminal connected to the negative current collector layer.

4. A secondary battery characterized by ​

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