Lithium battery naked cell internal temperature detection method and hot pressing effect detection equipment

Abstract

According to the lithium battery bare cell internal temperature detection method and the hot-pressing effect detection equipment provided by the invention, the relationship between the capacitance value and the overall temperature can be determined by constructing the temperature model, and when the capacitance value of the to-be-detected bare cell is input into the temperature model, the overall temperature of the corresponding to-be-detected bare cell can be obtained, so that the detection accuracy is improved. And then the internal temperature of the to-be-detected naked battery cell is calculated through the external temperature of the to-be-detected naked battery cell and the overall temperature of the to-be-detected naked battery cell, so that the method can be applied in the hot pressing process, the internal temperature of the naked battery cell can be known in real time, and the hot pressing temperature can be conveniently and timely adjusted; the method can be applied after hot pressing is finished, so that the internal temperature of the hot-pressed naked battery cell can be measured on the premise that the naked battery cell is not disassembled, and the hot pressing effect can be judged conveniently.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a method for detecting the internal temperature of a bare lithium battery cell and a device for detecting the effects of thermal compression. Background Art

[0002] At present, after lithium-ion batteries are wound or stacked, it is usually necessary to perform hot pressing and shaping on the bare cells, which is referred to as the hot pressing process. The required equipment is a hot press. The hot press performs hot pressing on the bare cells by controlling the pressure and temperature. However, due to differences in the thickness of the bare cells, uneven moisture content, insufficient temperature of the hot pressing plate, and insufficient heating time, the internal temperature of the bare cells often fails to meet the process requirements, thereby affecting the hot pressing and bonding effect between the diaphragm and the pole piece. If the hot pressing effect is not good, the cell may wrinkle after charging, thereby affecting its cycle life. The currently commonly used method for detecting the hot pressing effect can only be performed by manual disassembly and visual observation, but the prior art of manually disassembling and detecting the internal temperature of the bare cells will cause damage to the bare cells, and this disassembly method is not only inefficient, but also has high material and labor costs. Summary of the invention

[0003] In order to solve the above technical problems, this application is proposed. The embodiments of this application provide a method for detecting the internal temperature of a bare lithium battery cell and a device for detecting the thermal pressure effect, which solves the problem in the prior art that detecting the internal temperature of a bare cell by manual disassembly will damage the bare cell and the disassembly method is inefficient.

[0004] According to one aspect of the present application, a method for detecting the internal temperature of a bare lithium battery cell is provided, comprising:

[0005] Constructing a temperature model, wherein the temperature model is a corresponding relationship between the test capacitance value and the test overall temperature;

[0006] Get the capacitance value of the bare cell to be tested;

[0007] Calculating the overall temperature of the bare cell to be detected according to the capacitance value of the bare cell to be detected and the temperature model;

[0008] The external temperature of the bare cell to be detected is obtained, and the internal temperature of the bare cell to be detected is calculated according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected.

[0009] In one embodiment, constructing the temperature model includes:

[0010] Obtain multiple test capacitance values ​​of multiple test bare cells;

[0011] Determine the overall test temperature corresponding to the test capacitance value of the test bare cell, and fit the relationship between the overall test temperature and the test capacitance value according to the test capacitance values ​​of multiple test bare cells and the corresponding overall test temperatures: y=ax+b, y represents the test capacitance value, x represents the overall test temperature, and a and b are constants;

[0012] Based on the relationship formula, the temperature model is constructed.

[0013] In one embodiment, determining the test overall temperature corresponding to the test capacitance value of the test bare cell includes:

[0014] Get the test external temperature T of the test bare cell 表 And test the internal temperature T of the bare battery 内 ;

[0015] According to the test external temperature T of the bare battery 表 , Test the internal temperature T of the bare battery 内 And the formula: T 整 =(T 表 +T 内 ) / 2, and obtain the overall test temperature of the bare cell.

[0016] In one embodiment, a relationship between the overall test temperature and the test capacitance value is fitted, wherein the relationship formula is:

[0017] y=-0.0096x+5.9163, y represents the test capacitance value, and x represents the overall test temperature.

[0018] In one embodiment, calculating the internal temperature of the bare cell to be detected according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected includes:

[0019] Based on Formula 1, the internal temperature of the bare cell to be detected is calculated according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected;

[0020] T0=(T1+T2) / 2Formula 1,

[0021] Wherein, in formula 1, T0 is the overall temperature of the bare cell to be detected, T1 is the external temperature of the bare cell to be detected, and T2 is the internal temperature of the bare cell to be detected.

[0022] In one embodiment, after calculating the internal temperature of the bare cell to be detected according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected, the temperature detection method further includes:

[0023] If the internal temperature of the bare cell to be detected is greater than a preset temperature value, it is determined that the bare cell to be detected is an abnormal cell.

[0024] According to another aspect of the present application, a heat pressure effect detection device is provided, comprising:

[0025] Capacitance test module, used to obtain the capacitance value of the bare battery cell to be tested;

[0026] A temperature testing module, used to obtain the external temperature of the bare battery cell to be tested;

[0027] A data storage and processing module, wherein the data storage and processing module is respectively communicatively connected with the capacitance testing module and the temperature testing module, wherein the data storage and processing module stores the capacitance value of the bare cell to be tested, the external temperature of the bare cell to be tested, a temperature model and Formula 1, and wherein the data storage and processing module is used to calculate the internal temperature of the bare cell to be tested based on the capacitance value of the bare cell to be tested, the temperature model, the external temperature of the bare cell to be tested and Formula 1.

[0028] In one embodiment, the data storage and processing module further stores a preset temperature value, and the data storage and processing module is used to conclude that the bare cell to be detected is an abnormal cell based on the internal temperature of the bare cell to be detected being greater than the preset temperature value.

[0029] In one embodiment, the capacitance test module includes a capacitance tester, a positive electrode of the capacitance tester is electrically connected to a positive electrode tab of the bare battery cell, and a negative electrode of the capacitance tester is electrically connected to a negative electrode tab of the bare battery cell.

[0030] In one embodiment, the temperature testing module includes a thermocouple.

[0031] The present application provides a method for detecting the internal temperature of a bare lithium battery cell and a device for detecting the effects of thermal compression, comprising: constructing a temperature model, wherein the temperature model is a correspondence between a test capacitance value of the bare battery cell and a test overall temperature, obtaining the capacitance value of the bare battery cell to be detected, calculating the overall temperature of the bare battery cell to be detected based on the capacitance value of the bare battery cell to be detected and the temperature model, obtaining the external temperature of the bare battery cell to be detected, and calculating the internal temperature of the bare battery cell to be detected based on the external temperature of the bare battery cell to be detected and the overall temperature of the bare battery cell to be detected.

[0032] By constructing a temperature model, the relationship between the capacitance value and the overall temperature can be determined. When the capacitance value of the bare cell to be tested is input into the temperature model, the corresponding overall temperature can be obtained. Then, the internal temperature of the bare cell to be tested is calculated by the external temperature and the overall temperature. In this way, not only can the above method be applied during the hot pressing process, so that the internal temperature of the bare cell can be understood in real time, and the hot pressing temperature can be adjusted in time to ensure the quality of the bare cell after hot pressing, but also the above method can be applied after the hot pressing is completed, so that the internal temperature of the bare cell after hot pressing can be measured without disassembling the bare cell, so as to facilitate the judgment of the hot pressing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] By describing the embodiments of the present application in more detail in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present application will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

[0034] Figure 1 It is a flow chart of a method for detecting the internal temperature of a bare lithium battery cell provided by an exemplary embodiment of the present application.

[0035] Figure 2 It is a flowchart of a method for constructing a temperature model provided by an exemplary embodiment of the present application.

[0036] Figure 3 It is a curve diagram of the relationship between the overall test temperature and the test capacitance value of a bare cell provided by an exemplary embodiment of the present application.

[0037] Figure 4 It is a structural schematic diagram of a hot pressing effect detection device provided by an exemplary embodiment of the present application.

[0038] Figure 5 It is a structural schematic diagram of a hot pressing effect detection device provided by another exemplary embodiment of the present application.

[0039] Figure 6 It is a structural diagram of an electronic device provided by an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0040] Below, the exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the exemplary embodiments described here.

[0041] The inventors have discovered that during the hot pressing process, the internal temperature of the bare battery cell directly affects the quality of the bare battery cell after hot pressing. Currently, in order to understand the internal temperature of the bare battery cell, it can only be measured after the bare battery cell is disassembled. In this way, the internal temperature of the bare battery cell cannot be understood in real time during the hot pressing process, and the hot pressing temperature cannot be adjusted in real time to ensure the quality of the bare battery cell after hot pressing; and after the hot pressing is completed, the bare battery cell can only be destroyed to understand the hot pressing effect.

[0042] The inventors also discovered that the structure of a bare cell is similar to that of a capacitor, that is, the positive and negative electrodes in the bare cell are equivalent to the two electrodes in a capacitor, the facing area of ​​the positive electrode and the negative electrode in the bare cell is equivalent to the facing area of ​​the two electrodes in a capacitor, and the diaphragm and air located between the positive electrode and the negative electrode in the bare cell are equivalent to the dielectric located between the two electrodes in a capacitor.

[0043] The inventors also found that by heating multiple diaphragms of the same size to different temperatures, and measuring multiple diaphragms with different temperatures using the method described in JIS C2565 (resonant cavity method, etc.), specifically, inserting the diaphragm into a cavity resonator and measuring the change in the resonant frequency before and after the insertion of the diaphragm, the dielectric constant is calculated. Thus, through the study of the data of temperature and dielectric constant, it is found that the higher the temperature to which the diaphragm is heated, the smaller the corresponding dielectric constant. Therefore, according to It can be seen that the higher the temperature to which the bare cell is heated, the smaller the capacitance value of the bare cell.

[0044] Based on the above findings, Figure 1 As shown, the present application proposes a method for detecting the internal temperature of a bare lithium battery cell, including:

[0045] Step 110: construct a temperature model, where the temperature model is the corresponding relationship between the test capacitance value and the test overall temperature.

[0046] In an embodiment of the present application, the core purpose of constructing a temperature model is to establish a corresponding relationship between the test capacitance value of the test bare cell and its overall test temperature, so as to infer the temperature state inside the cell by the change of the test capacitance value. In this process, it is first necessary to experimentally measure the test capacitance value of the test bare cell under different temperature conditions, and collect a large amount of data to reflect the trend of the test capacitance value changing with the overall test temperature. These data will be used to establish a temperature model, and linear regression or nonlinear regression analysis can be used to reveal the functional relationship between the test capacitance value and the overall test temperature. After the temperature model is established, it needs to be verified by independent experimental data to ensure its accuracy and reliability. Through the temperature model, the temperature monitoring of the test bare cell during the hot pressing process can be achieved, the hot pressing process parameters can be optimized, and the bonding effect and cycle life of the test bare cell can be improved. In addition, the temperature model can also provide a theoretical basis for temperature control management in future battery design and production processes.

[0047] Step 120: Obtain the capacitance value of the bare cell to be tested.

[0048] In the embodiment of the present application, the capacitance value between the positive electrode sheet and the negative electrode sheet in the bare battery cell to be tested can be detected by a capacitance testing instrument.

[0049] Step 130: Calculate the overall temperature of the bare cell to be tested according to the capacitance value and temperature model of the bare cell to be tested.

[0050] By obtaining the capacitance value of the bare cell to be detected, the overall temperature of the bare cell to be detected can be calculated according to the capacitance value of the bare cell to be detected and a temperature model.

[0051] In an embodiment of the present application, since the temperature model includes the correspondence between the test capacitance value of the bare battery cell and the test overall temperature, the present application inputs the capacitance value of the bare battery cell to be tested into the temperature model, and can quickly obtain the overall temperature of the bare battery cell to be tested, thereby improving the efficiency of obtaining the internal temperature of the bare battery cell to be tested.

[0052] Step 140: Obtain the external temperature of the bare cell to be detected, and calculate the internal temperature of the bare cell to be detected based on the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected.

[0053] The internal temperature of the bare cell to be tested can be calculated based on the overall temperature of the bare cell to be tested and the external temperature of the bare cell to be tested, so that the internal temperature of the bare cell to be tested can be determined without manual disassembly.

[0054] In an embodiment of the present application, obtaining the external temperature of the bare cell to be tested is achieved through a temperature testing module, which can be in contact with the outer surface of the bare cell to monitor its external temperature in real time. Then, the internal temperature of the bare cell to be tested is calculated in combination with the external temperature of the bare cell to be tested and the overall temperature of the bare cell to be tested. There is a heat conduction relationship between the internal temperature of the bare cell to be tested and the external temperature of the bare cell to be tested. The external temperature affects the internal temperature, and the internal temperature is the temperature actually reached by the bare cell to be tested during hot pressing and working. By measuring the external temperature, an important boundary condition can be provided for the calculation of the internal temperature. In addition, the performance and safety of the bare cell to be tested are closely related to the internal temperature. The measurement of the external temperature of the bare cell to be tested can not only help calculate the internal temperature of the bare cell to be tested, but also provide a basis for the temperature control management of the cell, ensuring operation within a safe range to prevent overheating or performance degradation.

[0055] The present application provides a method for determining the relationship between the capacitance value and the overall temperature by constructing a temperature model. When the capacitance value of the bare cell to be tested is input into the temperature model, the corresponding overall temperature can be obtained, and then the internal temperature of the bare cell to be tested is calculated by the external temperature of the bare cell to be tested and the overall temperature of the bare cell to be tested. In this way, not only can the above method be applied during the hot pressing process, so that the internal temperature of the bare cell can be understood in real time, and the hot pressing temperature can be adjusted in time to ensure the quality of the bare cell after hot pressing, but also the above method can be applied after the hot pressing is completed, so that the internal temperature of the bare cell after hot pressing can be measured without disassembling the bare cell, so as to facilitate the judgment of the hot pressing effect.

[0056] Figure 2 FIG. 1 is a flow chart of a method for constructing a temperature model provided by an exemplary embodiment of the present application. Figure 2 As shown, step 110 (building a temperature model) may include:

[0057] Step 111: Obtain multiple test capacitance values ​​of multiple test bare cells.

[0058] In an embodiment of the present application, the present application can test multiple test capacitance values ​​of multiple test bare cells through a capacitance test module. The capacitance test module is respectively connected to the positive and negative ears of the test bare cells, so that the test capacitance value of the test bare cells can be obtained. Among them, the capacitance test module has a built-in capacitance test instrument, and the capacitance test instrument can quickly measure the test capacitance value of the test bare cell.

[0059] Step 112: Determine the overall test temperature corresponding to the test capacitance value of the test bare cell, and fit the relationship between the overall test temperature and the test capacitance value based on the test capacitance values ​​of multiple test bare cells and the corresponding overall test temperatures: y=ax+b, y represents the test capacitance value, x represents the overall test temperature, and a and b are constants.

[0060] In an embodiment of the present application, when the relationship curve between the test overall temperature and the test capacitance value is determined, a relationship formula can be constructed based on the relationship curve, and the overall test temperature corresponding to different test capacitance values ​​can be calculated through the relationship formula. Then, by inputting the capacitance value of the bare battery cell to be tested in the present application into the relationship formula, the corresponding overall temperature can be calculated.

[0061] Thus, according to the inventor's discovery: the higher the temperature to which the bare cell is heated, the smaller the capacitance value of the bare cell, and a suitable mathematical model (such as linear regression) is used to describe the relationship between the overall test temperature and the test capacitance value. By fitting the corresponding relationship between the overall test temperature and the test capacitance value, a linear relationship formula can be generated. The linear relationship formula can show the trend of the test capacitance value changing with the overall test temperature. The establishment of this linear relationship can help understand the electrical performance of the bare cell test, thereby improving the safety and performance of the battery.

[0062] Specifically, according to the relationship curve between the overall test temperature and the test capacitance value, a linear relationship formula y=ax+b can be constructed, where y represents the test capacitance value, x represents the overall test temperature, and a and b are constants. The slope a of the formula determines the trend of the test capacitance value changing with the overall test temperature, reflecting the sensitivity of the capacitor to temperature changes. The intercept b represents the starting value of the capacitance value under the reference temperature. The specific values ​​of a and b can be obtained by regression analysis of the experimental data. This formula can not only determine the predicted capacitance value under different temperature conditions, but also help understand the thermal properties of the material. Specifically in this embodiment, if a is a negative value, it means that the capacitance value decreases with the increase of temperature.

[0063] Step 113: Construct a temperature model based on the relationship formula.

[0064] In one embodiment, step 112 can be specifically implemented as follows: obtaining the test external temperature T of the test bare cell 表 And test the internal temperature T of the bare battery 内 ; According to the test external temperature T of the bare battery 表 , Test the internal temperature T of the bare battery 内 And the formula: T 整 =(T 表 +T 内) / 2, and obtain the overall test temperature of the bare cell.

[0065] Specifically, a temperature tester is first used to test the exterior of the test bare cell to obtain the test exterior temperature T of the test bare cell. 表 Then the test bare cell is cut and disassembled, and then the internal of the test bare cell is tested using a temperature tester to obtain the test internal temperature T of the test bare cell. 内 , finally according to the formula: T 整 =(T 表 +T 内 ) / 2, and calculate the overall test temperature of the bare cell.

[0066] In one embodiment, step 140 can be specifically implemented as follows: based on formula 1, the internal temperature of the bare cell to be detected is calculated according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected; T0 = (T1 + T2) / 2 Formula 1, wherein in formula 1, T0 is the overall temperature of the bare cell to be detected, T1 is the external temperature of the bare cell to be detected, and T2 is the internal temperature of the bare cell to be detected.

[0067] In the embodiment of the present application, since the heat is transferred from the outside to the inside of the bare cell, and each circle of the bare cell is composed of a positive electrode sheet, a negative electrode sheet and a diaphragm, the thickness uniformity of each circle of the bare cell is good, and therefore the heat transfer is uniform. A reasonable overall temperature estimate can be obtained by calculating the average value of the external temperature and the internal temperature. That is to say, the present application can calculate the internal temperature of the bare cell based on the understanding of the overall temperature and the external temperature according to Formula 1, thereby obtaining the internal temperature of the bare cell without disassembling the bare cell.

[0068] In one embodiment, after step 140, the method for detecting the internal temperature of a bare lithium battery cell may be specifically implemented as follows: if the internal temperature of the bare cell to be detected is greater than a preset temperature value, the bare cell to be detected is determined to be an abnormal cell.

[0069] In the embodiment of the present application, in order to determine whether the bare cell to be detected is an abnormal cell, a preset temperature value is set, and the preset temperature value is used to judge whether the internal temperature of the bare cell to be detected meets the requirements. Specifically, if the internal temperature of the bare cell to be detected is greater than the preset temperature value, the bare cell to be detected is determined to be an abnormal cell, and its performance and abnormality reasons need to be analyzed later. If the internal temperature of the bare cell to be detected is less than or equal to the preset temperature value, the bare cell to be detected is determined to be a normal cell.

[0070] Figure 4 Schematic diagram of the structure of a hot pressing effect detection device provided by an exemplary embodiment of the present application. Figure 4As shown, the thermal pressure effect detection equipment includes: a capacitance testing module, used to obtain the capacitance value of the bare battery cell to be detected; a temperature testing module, used to obtain the external temperature of the bare battery cell to be detected; a data storage and processing module, the data storage and processing module is communicated with the capacitance testing module and the temperature testing module respectively, the data storage and processing module stores the capacitance value of the bare battery cell to be detected, the external temperature of the bare battery cell to be detected, the temperature model and Formula 1, the data storage and processing module is used to calculate the internal temperature of the bare battery cell to be detected according to the capacitance value of the bare battery cell to be detected, the temperature model, the external temperature of the bare battery cell to be detected and Formula 1.

[0071] In an embodiment of the present application, the thermal pressure effect detection device of the present application includes a capacitance test module, a temperature test module, and a data storage and processing model. The built-in capacitance tester in the capacitance test module can detect the capacitance value of the bare cell to be tested. The temperature test module can obtain the external temperature of the bare cell to be tested. The data storage and processing module has the function of storing data and processing data. Therefore, the data storage and processing module is respectively communicated with the capacitance test module and the temperature test module. In this way, the capacitance value detected by the capacitance test module and the external temperature detected by the temperature test module are stored in the data storage and processing module and wait for processing, and the temperature model and formula 1 are stored in the data storage and processing module, so that the above-mentioned stored capacitance value and external temperature can be processed, and finally the internal temperature of the bare cell to be tested is obtained.

[0072] Specifically, the method for the capacitance test module to obtain the capacitance value of the bare battery cell is: electrically connect the positive electrode of the capacitance tester to the positive electrode ear of the bare battery cell, and electrically connect the negative electrode of the capacitance tester to the negative electrode ear of the bare battery cell to perform the test.

[0073] Specifically, the method for the temperature test module to obtain the external temperature of the bare cell is to place the test end of the thermocouple against the outer surface of the bare cell for testing. Among them, the thermocouple is a sensor for measuring temperature, based on the thermoelectric effect (especially the Seebeck effect). It is made of two different metals or alloy materials welded at a junction. When the temperature at the junction changes, a voltage (thermoelectric potential) is generated between the junctions, and there is a certain relationship between this voltage and temperature.

[0074] The data storage and processing module provided in the present application also stores a preset temperature value, and the data storage and processing module is used to deduce that the bare cell to be detected is an abnormal cell according to the fact that the internal temperature is greater than the preset temperature value. In the present application, by storing the preset temperature value in the data storage and processing module, and storing the preset temperature value and the internal temperature comparison instruction, when the internal temperature is greater than the preset temperature value, the result that the bare cell to be detected is an abnormal cell is output, and when the internal temperature is less than the preset temperature value, the result that the bare cell to be detected is a qualified cell is output.

[0075] Figure 6 A block diagram of an electronic device according to an embodiment of the present application is illustrated.

[0076] like Figure 6 As shown, the electronic device 10 includes one or more processors 11 and a memory 12 .

[0077] The processor 11 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device 10 to perform desired functions.

[0078] The memory 12 may include one or more computer program products, and the computer program product may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory (cache), etc. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 11 may run the program instructions to implement the lithium battery bare cell internal temperature detection method of each embodiment of the present application described above and / or other desired functions. Various contents such as input signals, signal components, noise components, etc. may also be stored in the computer-readable storage medium.

[0079] In one example, the electronic device 10 may further include: an input device 13 and an output device 14, and these components are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0080] When the electronic device 10 is a stand-alone device, the input device 13 may be a communication network connector for receiving collected input signals from the first device and the second device.

[0081] In addition, the input device 13 may also include, for example, a keyboard, a mouse, and the like.

[0082] The output device 14 can output various information to the outside, including the determined distance information, direction information, etc. The output device 14 can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto, and the like.

[0083] Of course, to simplify, Figure 6 Only some of the components related to the present application in the electronic device 10 are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, according to specific application situations, the electronic device 10 may also include any other appropriate components.

[0084] The computer program product may be written in any combination of one or more programming languages ​​to write program codes for performing the operations of the embodiments of the present application, including object-oriented programming languages, such as Java, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as an independent software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0085] The computer readable storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, a system, device or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0086] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

[0087] The method for obtaining the relationship between the overall test temperature and the test capacitance value of the present invention will be more specifically implemented below by illustrating an embodiment.

[0088] Step a, preparing 10 test bare cells of the same batch, specifically: winding or stacking the negative electrode sheet, the separator, the positive electrode sheet, the separator, and the negative electrode sheet in order to obtain the test bare cells;

[0089] The diaphragm may be a ceramic diaphragm. As the temperature increases, the dielectric constant of the ceramic diaphragm decreases. Specifically, the ceramic diaphragm may be a diaphragm material prepared by a ceramic particle coating technology, and the ceramic particles may be aluminum oxide (Al 2 O 3 ), silicon dioxide (SiO 2 ), the matrix material can be polypropylene (PP), polyethylene (PE) or a multi-layer composite membrane.

[0090] The positive electrode material of the positive electrode sheet can be lithium iron phosphate (LiFePO4 ), lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium nickel cobalt manganese oxide (Li(Ni,Co,Mn)O 2 ), lithium manganese oxide (LiMnO 2 ) Any one or more combinations thereof. The positive electrode material, conductive agent and adhesive are coated on aluminum foil to prepare a positive electrode sheet.

[0091] The negative electrode material of the negative electrode sheet can be lithium titanate (LTO), graphite, etc. The negative electrode material is coated on a copper foil substrate with a conductive agent and an adhesive to prepare the negative electrode sheet. Step b, 10 test bare cells are heated to different temperatures under the same environmental conditions;

[0092] Step c, using a thermocouple to test the test external temperature of the 10 test bare cells in step b, and using a capacitance tester to test the test capacitance values ​​of the 10 test bare cells in step b;

[0093] Step d, cutting 10 test bare cells, and using thermocouples to test the test internal temperatures of the 10 cut test bare cells respectively;

[0094] Step e: According to the formula: T 整 =(T 表 +T 内 ) / 2, and the overall test temperature of 10 test bare cells is calculated;

[0095] Step f, fitting the overall test temperature and the test capacitance value of the 10 test bare cells, and then obtaining the relationship: y = -0.0096x + 5.9163, y represents the test capacitance value, x represents the overall test temperature (such as Figure 3 ). Specifically, based on the relationship curve between the overall test temperature and the test capacitance value, a linear relationship formula y=-0.0096x+5.9163 was constructed, where y represents the test capacitance value in Farad (F), and x represents the overall test temperature in Celsius (℃). In this formula, the slope -0.0096 indicates that the test capacitance value decreases by about 0.0096 Farad for every 1℃ increase in the overall test temperature, showing the sensitivity of the capacitor to temperature changes. The intercept 5.9163 indicates that the starting value of the capacitor at the reference temperature (theoretically close to 0℃) is 5.9163 Farad.

[0096] Table 1

[0097]

[0098]

Claims

1. A method for detecting the internal temperature of a bare lithium battery cell, characterized in that: include: Constructing a temperature model, wherein the temperature model is a corresponding relationship between the test capacitance value and the test overall temperature; Get the capacitance value of the bare cell to be tested; Calculating the overall temperature of the bare cell to be detected according to the capacitance value of the bare cell to be detected and the temperature model; The external temperature of the bare cell to be detected is obtained, and the internal temperature of the bare cell to be detected is calculated according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected.

2. The method for detecting the internal temperature of a bare lithium battery cell according to claim 1, characterized in that: The temperature model building comprises: Obtain multiple test capacitance values ​​of multiple test bare cells; Determine the overall test temperature corresponding to the test capacitance value of the test bare cell, and fit the relationship between the overall test temperature and the test capacitance value according to the test capacitance values ​​of multiple test bare cells and the corresponding overall test temperatures: y=ax+b, y represents the test capacitance value, x represents the overall test temperature, and a and b are constants; Based on the relationship formula, the temperature model is constructed.

3. The method for detecting the internal temperature of a bare lithium battery cell according to claim 2, characterized in that: Determining the overall test temperature corresponding to the test capacitance value of the test bare cell includes: Get the test external temperature T of the test bare cell 表 And test the internal temperature T of the bare battery 内 ; According to the test external temperature T of the bare battery 表 , Test the internal temperature T of the bare battery 内 And the formula: T 整 =(T 表 +T 内 ) / 2, and obtain the overall test temperature of the bare cell.

4. The method for detecting the internal temperature of a bare lithium battery cell according to claim 2, characterized in that: The relationship between the overall test temperature and the test capacitance value is fitted, and the relationship formula is: y=-0.0096x+5.9163, y represents the test capacitance value, and x represents the overall test temperature.

5. The method for detecting the internal temperature of a bare lithium battery cell according to claim 1, characterized in that: The calculating the internal temperature of the bare cell to be detected according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected comprises: Based on Formula 1, the internal temperature of the bare cell to be detected is calculated according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected; T0=(T1+T2) / 2Formula 1, Wherein, in formula 1, T0 is the overall temperature of the bare cell to be detected, T1 is the external temperature of the bare cell to be detected, and T2 is the internal temperature of the bare cell to be detected.

6. The method for detecting the internal temperature of a bare lithium battery cell according to claim 1, characterized in that: After calculating the internal temperature of the bare cell to be detected according to the external temperature of the bare cell to be detected and the overall temperature of the bare cell to be detected, the temperature detection method further includes: If the internal temperature of the bare cell to be detected is greater than a preset temperature value, it is determined that the bare cell to be detected is an abnormal cell.

7. A hot pressing effect detection device, characterized in that: include: Capacitance test module, used to obtain the capacitance value of the bare battery cell to be tested; A temperature testing module, used to obtain the external temperature of the bare battery cell to be tested; A data storage and processing module, wherein the data storage and processing module is respectively communicatively connected with the capacitance testing module and the temperature testing module, wherein the data storage and processing module stores the capacitance value of the bare cell to be tested, the external temperature of the bare cell to be tested, a temperature model and Formula 1, and wherein the data storage and processing module is used to calculate the internal temperature of the bare cell to be tested based on the capacitance value of the bare cell to be tested, the temperature model, the external temperature of the bare cell to be tested and Formula 1.

8. The hot pressing effect detection device according to claim 7, characterized in that: The data storage and processing module also stores a preset temperature value, and the data storage and processing module is used to conclude that the bare cell to be detected is an abnormal cell based on the internal temperature of the bare cell to be detected being greater than the preset temperature value.

9. The hot pressing effect detection device according to claim 7, characterized in that: The capacitance test module includes a capacitance tester, a positive electrode of the capacitance tester is electrically connected to a positive electrode ear of the bare battery cell, and a negative electrode of the capacitance tester is electrically connected to a negative electrode ear of the bare battery cell.

10. The hot pressing effect detection device according to claim 7, characterized in that: The temperature testing module includes a thermocouple.

Images