A testing method and testing platform for equivalent edge voltage of soft package battery

Abstract

This invention discloses a method and testing platform for testing the equivalent side voltage of a pouch cell. The method includes: connecting a first test tab of the cell under test in series with a first equivalent resistance R. x The system includes a second equivalent resistance R and an electrolyte; a voltage measuring device is configured, one end of which is connected to the first equivalent resistance R. x Between the first and second equivalent resistance R, the other end can be selectively connected to the first or second test tab. The other end of the voltage measuring device is connected to the first test tab to measure the first equivalent side voltage V1, and the other end of the voltage measuring device is connected to the second test tab to measure the second equivalent side voltage V2. Based on V1 and V2, the insulation type can be determined. The type of aluminum-plastic film damage can also be estimated based on the relationship between V1 and V2, which can serve as a basis for improving battery packaging process parameters.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, and specifically to a method and application for testing the insulation properties of lithium batteries. In particular, it relates to the testing methods and applications of the side voltage of lithium batteries. Background Technology

[0002] In principle, the aluminum layer between the positive electrode and the aluminum-plastic film of a soft-pack lithium battery is insulating, and the voltage between them should be 0. However, in reality, the aluminum-plastic film undergoes mechanical punching during processing to form grooves of a specific depth to cover battery materials such as the battery cell and electrolyte. After mechanical processing, the inner structure of the aluminum-plastic film, such as the PP layer, inevitably suffers local damage, and the degree of damage increases with the processing intensity and punching depth. Local damage to the inner layer of the aluminum-plastic film leads to localized conductivity between the electrode tab and the aluminum-plastic film, forming a micro-battery and thus generating a potential difference.

[0003] In this way, the aforementioned potential difference will further cause the lithium ions in the electrolyte to react with the aluminum layer of the aluminum-plastic film to form an aluminum-lithium alloy, which will eventually make the aluminum-plastic film brittle and perforated. The electrolyte will flow out from the holes and react with the moisture inside the battery pack to produce gas, causing the lithium battery to expand and gradually fail. Based on the potential difference generated by localized conduction, the existing technology can use a voltmeter to test whether the aluminum-plastic film has been damaged during the processing.

[0004] In existing technologies, taking multimeters as an example, the side voltage test of soft-pack lithium batteries is based on the principle of voltage division. Specifically, an appropriate shunt resistor is connected in parallel with the meter to shunt the current, expanding the current range. The current measurement range can be changed by changing the resistance value of the shunt resistor. However, in actual resistance measurement, the meter resistance, shunt resistor, variable resistor, and the resistor under test must be considered simultaneously. The resistance value of the resistor under test is affected by the first three factors. In addition, the side voltage of the battery is subject to interference from external voltage and current. Even if a stable resistance value can be measured, it will not be the resistance under actual conditions, which will make the side voltage measurement less accurate.

[0005] In other words, in the current field of pouch lithium battery production, there is a lack of effective means to accurately detect the battery side voltage and resistance, making it difficult to determine whether the inner aluminum-plastic film (PP layer) of the pouch battery has been partially damaged, which endangers the overall quality control of mass-produced batteries and the safety of downstream users. Summary of the Invention

[0006] Based on the limitations of the aforementioned technical means, the main objective of this invention is to provide a test method for the equivalent side voltage of a soft-pack battery. This method simulates the relationship between various equivalent resistances and side voltages in mass-produced batteries, and is used to predict the internal resistance of the battery corresponding to a specific side voltage. Furthermore, the side voltage can be used to determine the differences in individual effects of electron channels and ion channels in the battery, thereby reflecting the damage type of the aluminum-plastic film. This allows personnel to determine the NG (non-performing) type of the battery, and also provides R&D personnel with a means to improve specific problems.

[0007] Accordingly, one aspect of the present invention is to provide a method for testing the equivalent side voltage of a pouch cell, characterized by comprising the following steps: Step S1: Prepare the battery to be tested, which includes a first test tab, a second test tab, an aluminum-plastic film, and an electrolyte; Step S2: Connect the first test tab and the first equivalent resistance R in series. x The first equivalent resistance R and the second equivalent resistance R are mentioned above. x Equal to or not equal to the second equivalent resistance R; and Step S3: Configure a voltage measuring device, one end of which is connected to the first equivalent resistance R. x Between the first terminal and the second equivalent resistor R, the other end can be selectively connected to the first or the second terminal to be tested, in order to measure the equivalent side voltage of the battery under test.

[0008] The method as described above is characterized in that the equivalent side voltage includes: The first equivalent edge voltage V1 is measured when the other end of the voltage measuring device is connected to the first electrode to be measured; and The second equivalent side voltage V2 is measured when the other end of the voltage measuring device is connected to the second electrode to be measured.

[0009] The method as described above is characterized in that the battery under test has an open-circuit voltage V. t The method further includes: Step S4a-1: Measure the open-circuit voltage V of the battery under test. t ;and Step S4a-2: Based on the open-circuit voltage V t The first equivalent side voltage V1 and the second The equivalent side voltage V2 is used to determine the insulation type of the battery under test, wherein: When V2 is less than 0.1V and |V1| is less than or equal to V t It is determined that an electronic channel exists between the second electrode and the aluminum-plastic film; When |V2| is greater than |V1| and |V1|+|V2|≈V tIt is determined that there are ion channels between the aluminum-plastic film and the electrolyte; When V2 is greater than 0.1V and |V1| / |V2|≈2, it is determined that the battery under test has both electron channels and ion channels.

[0010] The method as described above is characterized in that V t The voltage is 4.1V, V1 ranges from 0.1V to 4.1V, and V2 is greater than 0V. And less than 2.8V.

[0011] The method as described above is characterized in that V t The voltage is 3.6V, V1 is greater than 0 and less than 3.6V, and V2 is greater than 0 and less than 2.5V.

[0012] The method as described above is characterized in that, prior to step S1, the method further includes: Step S10: Prepare a reference battery, which includes a first reference tab, a second reference tab, a reference aluminum-plastic film, and a reference electrolyte; Step S20: Connect the first reference tab, the first reference equivalent resistance R1, the second reference equivalent resistance R2 and the reference electrolyte in series, wherein the first reference equivalent resistance R1 is equal to or not equal to the second reference equivalent resistance R2; Step S30: Configure a reference voltage measuring device, one end of which is connected between the first reference equivalent resistor R1 and the second reference equivalent resistor R2, and the other end can be selectively connected to the first reference tab or the second reference tab, to measure the first reference equivalent side voltage of the reference battery; and Step S40: Change the resistance values ​​of the first reference equivalent resistor R1 and the second reference equivalent resistor R2, and repeat steps S20 to S30 n times to record the resistance values ​​of the first reference equivalent resistor R1, the second reference equivalent resistor R2 and the reference equivalent side voltage in n+1 groups, and establish a side voltage-resistance dataset, where n is understood to be any positive integer greater than or equal to 1.

[0013] Another aspect of the present invention is to provide a test platform for the equivalent side voltage of a pouch cell, characterized in that it includes an equivalent side voltage analysis module configured to perform the method as described above. Attached Figure Description

[0014] Figure 1A The flowchart is used to illustrate the test method for the equivalent side voltage of the pouch cell in the first embodiment.

[0015] Figure 1B This is a block diagram illustrating the circuit of the equivalent side voltage test circuit in the first embodiment. Configuration method;

[0016] Figure 2 The flowchart is used to illustrate the test method for the equivalent side voltage of the soft-pack battery in the second embodiment.

[0017] Figure 3 The flowchart illustrates the testing of the equivalent side voltage of the pouch cell in the third and fourth embodiments. method;

[0018] Figure 4 The block diagram illustrates the component configuration of the test platform for the equivalent side voltage of the pouch battery in the fifth embodiment. Detailed Implementation

[0019] The following describes specific embodiments of the present invention with reference to accompanying drawings. Please refer to [link to relevant documentation]. Figures 1A to 1B The first embodiment of the present invention provides a method for testing the equivalent side voltage of a pouch cell. Its characteristic is that it includes the following steps: Step S1: Prepare a battery to be tested 100, which includes a first test tab 1, a second test tab 2, an aluminum-plastic film 3, and an electrolyte 4; Step S2: Connect the first test tab 1 and the first equivalent resistance R in series. x The first equivalent resistance R and the second equivalent resistance R and the electrolyte 4, wherein the first equivalent resistance R x Equal to or not equal to the second equivalent resistance R; and Step S3: Configure a voltage measuring device 5, one end of which is connected between the first equivalent resistance Rx and the second equivalent resistance R, and the other end can be selectively connected to the first test tab 1 or the second test tab 2 to measure the equivalent side voltage of the battery under test. The first test tab 1 and the second test tab 2 are either positive or negative tabs, which is not particularly limited. In a preferred embodiment, the first test tab 1 is a negative tab and the second test tab 2 is a positive tab.

[0020] In the first embodiment, the equivalent side voltage includes: The first equivalent edge voltage V1 is measured when the other end of the voltage measuring device 5 is connected to the first test tab 1; and The second equivalent side voltage V2 is measured when the other end of the voltage measuring device 5 is connected to the second electrode 2 under test. In a preferred embodiment, the first equivalent side voltage V1 and the second equivalent voltage V2 are measured as the basis for subsequent NG type determination of the battery under test.

[0021] In the first embodiment, the first equivalent resistance R xThe purpose of this configuration is to simulate the resistance between the first test tab 2 and the aluminum-plastic film 3. The resistance value is not particularly limited and can range from 0Ω to 10GΩ. Resistance values ​​ranging from any value between these ranges can be listed, such as 0Ω, 5MΩ, 10MΩ, 20MΩ, 30MΩ, etc. 50MΩ, 100MΩ, 200MΩ, 500MΩ, 1GΩ, 2GΩ, 5GΩ or 10GΩ, preferably 0Ω to 2GΩ; the purpose of configuring the second equivalent resistance R is to simulate the aluminum-plastic film 3 and the electrolyte 4. The resistance between these values ​​is also not particularly limited; it can be any value between 0Ω and 10GΩ, such as 0Ω, 5MΩ, 10MΩ, 20MΩ, 30MΩ, 50MΩ, and 100MΩ. MΩ, 200MΩ, 500MΩ, 1GΩ, 2GΩ, 5GΩ or 10GΩ, preferably 0Ω to 2GΩ.

[0022] Specifically, equivalent resistances of different values ​​are connected in series between the first test tab 2 and the aluminum-plastic film 3. Between them, the resistance R required to simulate the side voltage generated by the electronic channel can be calculated. x On the other hand, connecting the equivalent resistance in series between the aluminum-plastic film 3 and the electrolyte 4 can simulate the resistance R required for the side voltage generated by the ion channel between them; in the first embodiment, the first equivalent resistance R connected in series x The second equivalent resistance R can be regarded as the common resistance of the electronic channel and ion channel of the battery under test, so that the test circuit can be used to measure the side voltage of the aluminum-plastic film 3 after the battery is made into a dummy battery, or to be used as a basis for judging the defect type of NG battery in packaged soft-pack lithium batteries.

[0023] It is understandable that connecting the first test tab 2 and the aluminum-plastic film 3 in series is to measure the resistance value of the electron channel between them. The occurrence of the electron channel depends on the surface corrosion of the aluminum-plastic film 3. Therefore, the so-called connecting the first test tab 2 and the aluminum-plastic film 3 in series here is, in specific implementation, connected in series with the inner aluminum foil of the aluminum-plastic film 3.

[0024] The second embodiment of the present invention provides a method for testing the equivalent side voltage of a pouch cell. The specific implementation steps are largely the same as those provided in the first embodiment, except that... Figure 2 As shown, it also includes: Step S4a-1: Measure the open-circuit voltage V of the battery under test. t ;and Step S4a-2: Based on the open-circuit voltage V tThe first equivalent side voltage V1 and the second equivalent side voltage V2 are used to determine the insulation type of the battery under test. The "open circuit voltage" refers to the terminal voltage of the battery in the open circuit state, which is equal to the difference between the positive and negative potentials of the battery when the circuit is broken, that is, when no current flows through the two poles.

[0025] In the second embodiment, the insulation type of aluminum-plastic film can be divided into three categories: First, due to the corrosion of the PP layer of aluminum-plastic film, the tab and the aluminum layer of aluminum-plastic film are made conductive, that is, an electronic path is generated. Secondly, because lithium ions in the electrolyte enter the inner layer of the aluminum-plastic film and form an aluminum-lithium alloy, conductivity is created between the aluminum layer of the aluminum-plastic film and the electrolyte, i.e., an ion pathway is formed. Thirdly, under normal circumstances, corrosion of the aluminum-plastic film may occur individually or simultaneously, as described above. When synchronization occurs, it is necessary to consider the situation where electron channels and ion channels coexist.

[0026] In the second embodiment, when V2 is less than 0.1V and |V1| is less than or equal to V t It is determined that an electronic channel exists between the second electrode 2 and the aluminum-plastic film 3; when |V2| is greater than |V1| and |V1|+|V2|≈V t It is determined that there are ion channels between the aluminum-plastic film 3 and the electrolyte 4; when V2 is greater than 0.1V and |V1| / |V2|≈2, indicating that the battery under test 100 simultaneously possesses both electron and ion channels; in several embodiments, the first electrode tab 1 is a positive electrode tab, the second electrode tab 2 is a negative electrode tab, the first equivalent side voltage V1 is the positive side voltage of the battery under test 100, and the second equivalent side voltage V2 is the negative side voltage of the battery under test 100; in other embodiments, the first electrode tab 1 is a negative electrode tab, the second electrode tab 2 is a positive electrode tab, the first equivalent side voltage V1 is the negative side voltage of the battery under test 100, and the second equivalent side voltage V2 is the positive side voltage of the battery under test 100.

[0027] In some other embodiments, when V2 is less than 0.1V, and 0.1V is satisfied. t <|V1|≦V t It is determined that an electronic channel exists between the second electrode 2 and the aluminum-plastic film 3; when V2 is greater than 0.1V and |V2| is greater than |V1|, satisfies 0.2V t <|V1|+|V2|≦V t It is determined that there are ion channels between the aluminum-plastic film 3 and the electrolyte 4, preferably satisfying 0.2V. t <|V1|+|V2|≦0.97Vt When V2 is greater than 0.1V, the condition is met. If |V1| / |V2|>1, it is determined that the battery under test 100 has both electron channels and ion channels, preferably satisfying 1<|V1| / |V2|<16.

[0028] In the second embodiment, the magnitude of the side voltage used to determine whether electron channels, ion channels, or both coexist in the battery under test 100 varies with the open-circuit voltage. Therefore, the first equivalent side voltage V1 and the second equivalent side voltage V2 differ depending on the magnitude of the open-circuit voltage of the battery under test 100. For example, V t The voltage is 4.1V, V1 ranges from 0.1V to 4.1V, and V2... Greater than 0 and less than 2.8V; or V t The voltage is 3.6V, V1 is greater than 0 and less than 3.6V, and V2 is greater than 0 and less than 2.5V, but is not limited to these values.

[0029] In the second embodiment, when the battery under test 100 simultaneously possesses electron channels and ion channels, And the first equivalent resistance R x When the second equivalent resistance R is equal to the first equivalent side voltage V1 and the second equivalent side voltage V2 satisfy the following conditions: In one example, V t For example, with a voltage of 4.1V, V1 is -0.48V and V2 When the voltage is 0.23V, its first equivalent resistance R x This is equal to the second equivalent resistance R, meaning the electron channel size is the same as the ion channel size, for example, both are 100 MΩ; in another example, V t Taking V1 = 4.09V as an example, when V1 is -1.06V and V2 is 0.55V, its first equivalent resistance R x Equal to the second equivalent resistance R, both are 30MΩ; in another example, V t For example, with a voltage of 4.09V, V1 is -0.48V and V2 is... At 1.36V, its first equivalent resistance R x The resistance is greater than the second equivalent resistance R, for example, 1 GΩ and 10 MΩ respectively, indicating that its ion channel effect is much greater than the electron channel effect. Through the aforementioned judgment logic, the insulation type of the battery under test 100 can be directly determined according to the side voltage standard required by different needs, and further determined whether it is an NG product based on its insulation type. At the same time, the aluminum-plastic film 3 can be selectively adjusted according to the size of the electron channel and ion channel.

[0030] In another application, when using aluminum-plastic film to encapsulate dummy cells to simulate the battery under test 100, the size of the ion channel and electron channel can be used to simulate the side voltage of the equivalent battery. Furthermore, if the same process conditions are used, such as side sealing and top sealing, and aluminum-plastic film with the same material and layering design is used, the NG rate of the batch of aluminum-plastic film can be determined by side voltage testing under the same process conditions. Conversely, based on the same material and layering design of aluminum-plastic film, changing different process conditions can provide a deeper understanding of the NG rate caused by changes in process conditions. Specifically, the above scenarios can be widely used by different battery manufacturers to monitor whether process conditions are continuously improved during the production of the same batch of pouch batteries, or to monitor whether the manufacturing of their aluminum-plastic film needs improvement.

[0031] The third embodiment of the present invention provides a method for testing the equivalent side voltage of a pouch cell. The specific implementation steps are largely the same as those provided in the first embodiment, except that... Figure 2 As shown, the method further includes step S4b: based on a preset resistance value R s and preset side voltage value V s The insulation performance of the aluminum-plastic film 3 is determined by comparing the first equivalent side voltage V1 with the second equivalent side voltage V2.

[0032] In the third embodiment, the preset resistance value R s This refers to the resistance value of electron channels, ion channels, or a combination of both, and the preset side voltage value V. s It is the expected measured edge voltage value under the condition of satisfying battery insulation; the preset resistance value R s With the preset side voltage value V s With the size of the battery under test 100 and the open circuit voltage V t The properties of aluminum-plastic film vary depending on the conditions, so there are no particular restrictions.

[0033] Generally speaking, when a soft-pack lithium battery meets the insulation requirements, the resistance of the electron channel, ion channel, or their combination can be greater than or equal to 100MΩ. The expected side voltage value can be from 0.1V to 1.0V, preferably from 0.5V to 0.8V, depending on the needs of different battery production.

[0034] In the third embodiment, when R is satisfied s Less than or equal to R x and R and V s When it is greater than |V1| and |V2|, The insulation property of the aluminum-plastic film is determined to be good; or when R is satisfied... s Greater than R x and R and Vs Less than |V1| or |V2| When, or satisfying R s Less than R x And R s Greater than R and V s When less than |V1| or |V2|, or when R is satisfied s Greater than R x And R s Less than R and V s If the value is less than |V1| and greater than |V2|, the insulation performance of the aluminum-plastic film is judged to be poor.

[0035] Specifically, under the condition of good insulation, the equivalent resistance (R) of the battery under test 100 is... x , R) are all greater than the preset resistance value R. s Theoretically, the effects of electron and ion channels in the battery under test 100 are quite small, even negligible, and it is not easy to generate micro-cells inside the battery. Therefore, the measured side voltage is also less than the preset side voltage V. s Conversely, when the insulation performance is poor, the effects of the internal electron or ion channels of the battery under test 100 are quite significant. Whether due to conduction between the tab and the aluminum-plastic film or between the aluminum-plastic film and the electrolyte, the internal resistance of the battery under test 100 decreases, resulting in a decrease in the equivalent resistance R. x Or R is less than the preset resistance value R s Under the aforementioned conditions, the measured side voltage value |V1| or |V2| will be greater than the preset side voltage value V. s When the ion channel effect is large, |V1| is greater than V. s When the electron channel effect is large, then |V2| is greater than V. s .

[0036] The fourth embodiment of the present invention provides a method for testing the equivalent side voltage of a pouch cell. The specific implementation steps are largely the same as those provided in the first embodiment, except that... Figure 3 As shown, prior to step S1, the method further includes: Step S10: Prepare a reference battery, which includes a first reference tab, a second reference tab, a reference aluminum-plastic film, and a reference electrolyte; Step S20: Connect the first reference tab, the first reference equivalent resistance R1, the second reference equivalent resistance R2 and the reference electrolyte in series, wherein the first reference equivalent resistance R1 is equal to or not equal to the second reference equivalent resistance R2; Step S30: Configure a reference voltage measuring device, one end of which is connected between the first reference equivalent resistor R1 and the second reference equivalent resistor R2, and the other end can be selectively connected to the first reference tab or the second reference tab, so as to measure the reference equivalent side voltage of the reference battery. Step S40: Change the resistance values ​​of the first reference equivalent resistor R1 and the second reference equivalent resistor R2, and repeat steps S20 to S30 n times to record the resistance values ​​of the first reference equivalent resistor R1, the second reference equivalent resistor R2 and the reference equivalent side voltage in n+1 groups, and establish a side voltage-resistance dataset, where n is understood to be any positive integer greater than or equal to 1.

[0037] In the fourth embodiment, the reference equivalent side voltage includes: First reference equivalent side voltage V 1R It is measured when the other end of the reference voltage measuring device is connected to the first reference electrode; and Second reference equivalent side voltage V 2R It is measured when the other end of the reference voltage measuring device is connected to the second reference electrode 2; in a preferred embodiment, the first reference equivalent edge voltage V is measured sequentially. 1R Second reference equivalent voltage V 2R This will serve as the basis for subsequently establishing the aforementioned side voltage-resistance dataset.

[0038] In the fourth embodiment, during the repeated implementation of steps S20 to S30, in order to simulate different equivalent resistance states, the first reference equivalent resistance R1 can be sequentially or randomly changed to the third reference equivalent resistance R3, the fifth reference equivalent resistance R5, the seventh reference equivalent resistance R7, etc., and the second reference equivalent resistance R2 can be sequentially or randomly changed to the fourth reference equivalent resistance R4, the sixth reference equivalent resistance R6, the eighth reference equivalent resistance R8, etc. Specifically, R1, R3, R5, and R7 can be replaced by different resistive elements, or the resistance value of R1 can be directly adjusted by the first reference variable resistor. R3, R5, R7, or other resistors different from those mentioned above; similarly, R2, R4, R6, and R8 can also be obtained by replacing them with different resistive elements, or by adjusting the resistance value of the second reference variable resistor; it is understood that in order to obtain equivalent side voltage values ​​under different equivalent resistances, the aforementioned R1, R3, R5, R7 represents different resistance values, and R2, R4, R6, and R8 also represent different resistance values.

[0039] In the fourth embodiment, please continue to refer to... Figure 3 The method further includes: Step S50: Set a preset resistance value R based on the edge voltage-resistance dataset. s and preset side voltage value V s And based on the preset resistance value R s The preset side voltage value V s The insulation performance of the aluminum-plastic film 3 is determined by comparing the first equivalent side voltage V1 with the second equivalent side voltage V2. When R is satisfied s Less than or equal to R x and R and V s When the values ​​are greater than |V1| and |V2|, the insulation performance of the aluminum-plastic film is considered good; or When R is satisfied s Greater than R x and R and V s When it is less than |V1| or |V2|, or satisfies R s Less than R x And R s Greater than R and V s When less than |V1| or |V2|, or when R is satisfied s Greater than R x And R s Less than R and V s If the value is less than |V1| and greater than |V2|, the insulation performance of the aluminum-plastic film is judged to be poor.

[0040] The fifth embodiment of the present invention provides a test platform 200 for the equivalent side voltage of a pouch cell. like Figure 4 As shown, it includes an equivalent side voltage analysis module 201 configured to perform the method as described in any of the first to fourth embodiments.

[0041] For further details on various specific embodiments, please refer to the following: Figure 4 The test platform 200 for the equivalent side voltage of the pouch battery includes: A test battery stage 202 is configured to mount the test battery 100. The first variable resistor 203 is electrically connected to the battery platform 202 under test, and its connection end with the battery platform 202 under test is provided with a first terminal 202a to contact the first electrode tab 1 under test. Or the second electrode under test 2, wherein the first variable resistor 203 responds to the equivalent side voltage analysis module 201 to adjust the first equivalent resistance R. x The resistance value changes with the resistance value; The second variable resistor 204 is electrically connected to the first variable resistor 203 and the battery platform 202 under test, and its connection end with the battery platform 202 under test is provided with a second terminal 202b to contact the electrolyte 4. The second variable resistor 204 responds to the equivalent side voltage analysis module 201 by varying its resistance value according to the resistance value of the second equivalent resistance R. The voltage measuring device 205 has one end electrically connected between the first variable resistor 203 and the second variable resistor 204, and the other end electrically connected to the first test tab 1 or the second test tab 2 in response to the equivalent side voltage analysis module 201.

[0042] Understandably, in implementing the method described in the fourth embodiment, simply replacing the battery under test 100 with a reference battery of the same type allows for the measurement and recording of reference side voltages under different reference equivalent resistance values ​​through the test platform 200 for equivalent side voltage of the pouch battery. The equivalent side voltage analysis module 201 then reads the reference equivalent resistance value and the reference side voltage to establish a resistance-side voltage dataset, which serves as the basis for analyzing the side voltage and NG (non-compliant) product type of the battery under test 100.

[0043] Example 1

[0044] Equivalent Resistance-Side Voltage Test Circuit: Take a commercially available polymer lithium battery and connect a variable resistor in series with the negative electrode tab via a wire. Connect another variable resistor in series with a wire downstream of the variable resistor. Pierce the aluminum-plastic film of the polymer lithium battery to allow electrolyte to leak out, but be careful not to puncture the separator. Connect the other variable resistor in series with the electrolyte via a wire. Connect one end of the voltage measuring device between the two variable resistors, and selectively connect the other end to the positive or negative electrode tab depending on whether the positive or negative electrode side voltage is being measured.

[0045] Adjusting the resistance values ​​of these variable resistors simulates different equivalent resistances. The specific adjustment methods are as follows: The variable resistor connected in series with the negative electrode tab simulates the equivalent resistance between the negative electrode tab and the aluminum-plastic film, and is indicated by Tab / PP in Table 1 and Table 2; the other variable resistor connected in series with the electrolyte simulates the equivalent resistance between the aluminum-plastic film and the electrolyte, and is indicated by AL / PP in Table 1 and Table 2. It can also be any resistance value.

[0046] Measure the boundary voltage under different equivalent resistances: sequentially adjust the resistance values ​​of Tab / PP and AL / PP to 0Ω. 5MΩ, 10MΩ, 20MΩ, 30MΩ, 50MΩ, 100MΩ, 200MΩ, 500MΩ, 1GΩ, 2GΩ, 5GΩ, or 10GΩ, and sequentially measure the positive terminal voltage V. + Negative terminal voltage V- And its open-circuit voltage (approximately 4.09V), and record the relationship between the side voltage value and the resistance according to the tables shown in Tables 1 and 2. Table 1 Table 2

[0047] Test Example 1

[0048] Commercially available polymer lithium batteries (JT-2) of the same model but from different batches were taken. First, the positive terminal voltage was measured to be -0.34V and the negative terminal voltage was measured to be 0.25V using a general terminal voltage test circuit. The open circuit voltage was measured to be 3.98V. Based on the relationship between terminal voltage and equivalent resistance shown in Table 1, the Tab / PP of JT-2 was estimated to be approximately 200MΩ and the AL / PP to be approximately 50MΩ to 100MΩ.

[0049] Test Example 2

[0050] Commercially available polymer lithium batteries (JT-3) of the same model but different batches were taken. First, the positive terminal voltage was measured to be -0.681V and the negative terminal voltage was measured to be 0.727V using a general side voltage test circuit. The open circuit voltage was measured to be 3.98V. Based on the relationship between side voltage and equivalent resistance shown in Table 2, the Tab / PP of JT-3 was estimated to be approximately 500MΩ and the AL / PP to be approximately 20MΩ to 30MΩ.

[0051] Test Example 3

[0052] Commercially available polymer lithium batteries (JT-4) of the same model but from different batches were taken. First, the positive terminal voltage was measured to be -1.210V and the negative terminal voltage was measured to be 0.947V using a general terminal voltage test circuit. The open circuit voltage was measured to be 3.978V. Based on the relationship between terminal voltage and equivalent resistance shown in Table 1, the Tab / PP of JT-4 was estimated to be approximately 30MΩ and the AL / PP to be approximately 10MΩ to 20MΩ. Table 3

[0053] As can be seen from the above embodiment 1, the method for testing the equivalent side voltage of a pouch cell provided by the present invention... An equivalent resistance-side voltage test circuit is used to simulate different equivalent resistance conditions and establish a graph showing the correspondence between equivalent resistance and side voltage. Based on the graph, as shown in test examples 1 to 3, after measuring the positive and negative side voltages respectively, the resistance values ​​of the corresponding Tab / PP and AL / PP can be estimated. Then, based on the estimated resistance values, an equivalent resistance-side voltage measurement circuit is constructed to further measure the actual side voltage values.

[0054] Furthermore, as shown in Table 3, based on the estimated equivalent resistance value, the degree of ion channel effect and electron channel effect in the pouch battery can be preliminarily determined to determine its insulation type; for example, using When both Tab / PP and AL / PP are 100MΩ as the criterion for judging NG products of soft-pack batteries, JT-2 obviously meets this criterion and can be regarded as a non-NG product, as its ion channel and electron channel effects are not significant. The AL / PP ratio of JT-3 is significantly lower than that of Tab / PP and also lower than that of the standard AL / PP, indicating that there is contact between the electrolyte and the aluminum-plastic film, resulting in an ion channel effect. It is initially judged as an NG product. The Tab / PP and AL / PP ratios of JT-4 are both significantly lower than those of the standard Tab / PP and standard AL / PP, indicating that both the tab and the aluminum-plastic film are in contact with the electrolyte, and that it has both electron channel and ion channel effects. It can also be initially judged as an NG product.

[0055] In summary, the equivalent side voltage testing method provided by this invention allows personnel to establish the correspondence between equivalent resistance and side voltage for pouch lithium batteries produced using the same process on-site. This method can then be applied to the side voltage testing of different batches of pouch lithium batteries to determine the insulation performance of the aluminum-plastic film and identify corresponding electron or ion channel effects, enabling production personnel to understand... The type of damage to NG products serves as a reference for adjusting the battery packaging process.

[0056] The above embodiments are merely illustrative examples of the test method for the equivalent side voltage of the soft-pack battery provided by the present invention, and do not limit the present invention in any way. Any simple modifications or adjustments made to the present invention by any researcher in the field without departing from the spirit and framework of the present invention should be within the scope of protection of the invention rights of this application.

Claims

1. A method for testing the equivalent side voltage of a pouch cell, characterized in that, Includes the following steps: Reference battery, one end of variable resistor R is connected to the negative tab through a wire in series X The other end of variable resistor R is connected to the other end of variable resistor R through a wire in series X The aluminum film of the reference battery is punctured to leak electrolyte, the other end of variable resistor R is connected to the electrolyte through a wire in series; one end of the voltage measuring device is connected between the two variable resistors, the other end is selectively connected to the positive tab or the negative tab according to the measurement of the positive edge voltage or the negative edge voltage; Adjusting the variable resistor R X The resistance values ​​of R and R simulate different equivalent resistances, where the variable resistor R connected in series with the negative terminal tab is... X It is the equivalent resistance between the negative electrode tab and the aluminum-plastic film. The variable resistor R connected in series with the electrolyte is the equivalent resistance between the aluminum-plastic film and the electrolyte. Measure the boundary voltage under different equivalent resistances, and adjust the variable resistor R in sequence. X And the resistance value of the variable resistor R, and sequentially measure the positive terminal voltage V. + Negative terminal voltage V - And record the positive terminal voltage V. + Negative terminal voltage V - With variable resistor R X Establish a table showing the relationship between the variable resistor R and the equivalent resistance and the side voltage; A battery of the same model but different batch as the reference battery was selected as the test battery. The positive terminal voltage V1, negative terminal voltage V2, and open circuit voltage V of the test battery were measured respectively. t The equivalent resistance of the battery under test is estimated based on the equivalent resistance and side voltage correspondence table. Based on the estimated equivalent resistance of the battery under test, the degree of ion channel effect and electron channel effect in the pouch battery is judged to determine the insulation type of the battery under test.

2. The test method according to claim 1, characterized in that: When V2 is less than 0.1V and |V1| is less than or equal to V t It was determined that an electron channel existed between the negative electrode tab and the aluminum-plastic film; When |V2| is greater than |V1| and |V1|+|V2|≈V t This indicates the existence of ion channels between the aluminum-plastic film and the electrolyte; When V2 is greater than 0.1V and |V1| / |V2|≈2, it is determined that the battery under test has both electron channels and ion channels.

3. The test method according to claim 2, characterized in that: V t The voltage is 4.1V, V1 is 0.1 to 4.1V, and V2 is greater than 0 and less than 2.8V.

4. The test method according to claim 2, characterized in that: V t The voltage is 3.6V, V1 is greater than 0 and less than 3.6V, and V2 is greater than 0 and less than 2.5V.

5. A test platform for the equivalent side voltage of a pouch cell, characterized in that: Includes an equivalent side voltage analysis module configured to perform the test method as described in any one of claims 1 to 4.

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