A method for testing the electrical performance of lithium-ion batteries for manned submersibles

Abstract

The present invention discloses a method for testing the electrical properties of lithium-ion batteries under pressure in the full sea depth range suitable for use in manned submersibles. The method uses a pressure simulation device for simulation testing and a normal pressure electrical property test, and the discharge capacity and AC ohmic internal resistance of the battery as the main basis for judgment to predict the electrical properties of the lithium-ion battery under pressure. Through the testing method of the present invention, it is possible to quickly and simply evaluate whether the lithium-ion battery cells are capable of effectively discharging within the full sea depth pressure range, thereby providing safe and reliable energy and power guarantee for the safe operation of a deep-sea manned submersible under pressure of 10,000 meters in the pressure range of 0 to 11,000 meters under sea water.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for detecting the electrical properties of a self-pressurized lithium ion battery for a manned submersible suitable for full-sea-depth operation. Background Art

[0002] Lithium-ion batteries have become the most promising batteries for deep-sea equipment due to their high specific energy and high specific power characteristics. Replacing traditional silver-zinc batteries in deep-sea submersibles with lithium-ion batteries can greatly improve the endurance and electrical load capacity of deep-sea equipment. However, whether lithium-ion batteries can withstand the huge seawater pressure in the deep sea is the primary problem that restricts their application in deep-sea equipment.

[0003] At present, lithium-ion batteries used in deep-sea equipment mainly adopt two pressure-bearing methods: 1. Relying on pressure-bearing shells to bear pressure; 2. Lithium-ion batteries bear pressure directly. The heavy shell required by the former greatly reduces the mass-to-energy ratio of the entire battery system, making it difficult to meet the needs of deep-sea equipment development. The latter has high requirements on the battery technology level because lithium-ion batteries bear pressure directly, and its ability to withstand deep-sea pressure is still unclear.

[0004] How to examine whether lithium-ion batteries designed to withstand pressure can truly withstand the complex pressure environment of the deep sea and ensure the safe operation of deep-sea submersibles at all sea depths has become one of the bottleneck technologies in deep-sea battery technology.

[0005] Manned submersibles are deep-sea equipment that have the highest requirements for the reliability of lithium-ion battery electrical performance. When used as the main power source, the stability of its electrical performance directly determines whether the divers can return home smoothly. Based on the current demand for the use of manned submersibles around the world, the electrical performance requirements of lithium-ion batteries must meet the following points: (1) they can be discharged normally for a long time in a hydrostatic pressure environment of 0 to 115 MPa; (2) the discharge temperature matches the low temperature environment of the deep sea; and (3) they must be able to withstand the voltage change rate that is suitable for the working conditions of manned submersibles.

[0006] In order to ensure the reliability of the power supply of the submersible, the electrical performance of the pressure-bearing lithium-ion battery needs to be strictly tested after the preparation is completed. Only the lithium-ion batteries that have been screened can be used in groups. However, the number of pressure-bearing electrical performance tests commonly used in the industry is more than 30 times, and the single pressure-bearing test time is long, which makes the entire electrical performance test cycle long and consumes a lot of human and material resources during the test process. This is one of the important reasons why the manufacturing cost of lithium-ion batteries for manned submersibles is much higher than that of conventional lithium-ion batteries.

[0007] However, speeding up the electrical performance testing and screening cycle and reducing the number of withstand voltage tests will reduce the reliability of lithium-ion battery withstand voltage electrical performance testing. Therefore, in order to reduce the manufacturing cost of deep-sea pressure-bearing lithium-ion batteries while ensuring the reliability and non-destructiveness of electrical performance testing, it is urgent to solve the above technical contradictions. Summary of the invention

[0008] In view of the deficiencies of the prior art, the present invention provides a method for testing the electrical performance of a lithium-ion battery that is pressurized within the full ocean depth range and is suitable for use in a manned submersible.

[0009] The technical solution adopted by the present invention to solve the technical problem is: a method for testing the electrical performance of lithium-ion batteries for manned submersibles, and the ohmic internal resistance R 常压 The lithium-ion battery cells with a resistance of 1mΩ to 2mΩ have the ability to withstand pressure in a water pressure environment of 0 to 11,000 meters or seawater pressure, and can meet the maximum voltage transformation rate of 2MPa / min. The specific pressure resistance electrical performance test process includes the following steps:

[0010] The first step is to visually inspect the appearance of the lithium-ion battery. The battery surface must be free of particles, electrolyte traces, wrinkles, damage, and deformation.

[0011] The second step is to conduct an AC impedance spectrum test on the battery cell in a fully charged state to obtain the ohmic impedance R related to the transport of lithium ions and electrons through the electrolyte, porous diaphragm, and active material particles in the lithium-ion battery. 常压 , R 常压 Should be between 1mΩ and 2mΩ;

[0012] The third step is to conduct a low-temperature electrical performance test of the fully charged lithium-ion battery at about 0°C: a normal pressure low-temperature test and a 127MPa withstand pressure low-temperature electrical performance test, a≥5, and the battery capacity before and after the test must meet Q 耐压a / Q 常压 ≥99%, and the AC ohmic impedance R satisfies 0.5≤R 耐压a / R常压 ≤0.9.

[0013] Furthermore, the low-temperature electrical performance test at about 0°C should be carried out at a temperature of -4 to 5°C, the electrical performance test at normal pressure should be carried out in an environment with a relative humidity of 25 to 85% and an air pressure of 90 to 108 kPa, and the 127 MPa pressure-resistant low-temperature test should be carried out in a simulated pressure cylinder, specifically including the following steps:

[0014] Step 1: Charge the battery at a constant current of 0.2C rate according to the rated capacity of the lithium-ion battery, stop charging after charging to the rated cut-off voltage, and let the battery stand for ≥30 minutes before connecting the battery to an AC impedance tester to perform an AC impedance spectrum scan under open circuit voltage conditions. The AC frequency scanning range should be no less than 0.01Hz to 0.1MHz. The ohmic internal resistance R is obtained after fitting the AC impedance spectrum obtained by the test, and the spectrum fitting accuracy should be above 90%;

[0015] Step 2: Discharge the lithium-ion battery at a constant current rate of 0.2C at the rated capacity until the rated discharge cut-off voltage is reached, and then the normal pressure discharge capacity Q is obtained. 常压 ;

[0016] Step 3: Follow the same constant current charging method as step 1 to fully charge the lithium-ion battery and then let it stand for ≥ 30 minutes;

[0017] Step 4, placing the lithium-ion battery in a pressure simulation device, and connecting the positive and negative electrodes to an external circuit;

[0018] Step 5: Start the pressure simulation device, pressurize to 127MPa at a pressurization rate of S1 = 0-2MPa / min, and maintain the pressure for T1 ≥ 310 minutes;

[0019] Step 6: When the pressure simulation device reaches 127 MPa, the lithium-ion battery is subjected to an AC impedance spectrum scan under open circuit voltage conditions, and the ohmic internal resistance R 耐压a , where the AC frequency scanning range and spectrum fitting accuracy are the same as in step 1;

[0020] Step 7: In the 127MPa environment, the lithium-ion battery cell is discharged at a constant current rate of 0.2C at the rated capacity, and the discharge is stopped after the rated discharge cut-off voltage is reached. The obtained a-th withstand voltage discharge capacity is recorded as Q 耐压a ;

[0021] Step 8: The pressure simulation device releases pressure to normal pressure at a pressure release rate of S2 ≥ 1 MPa / min;

[0022] Step 9, remove the battery from the pressure simulation device and let it rest for 30 minutes;

[0023] Step 10: Repeat steps 3 to 9 a times, where a ≥ 5 times.

[0024] Furthermore, the lithium-ion battery is a ternary nickel-cobalt-manganese battery, a ternary nickel-cobalt-aluminum battery, a lithium iron phosphate battery, a lithium titanate battery or a lithium-rich battery.

[0025] The beneficial effects of the present invention are:

[0026] The testing method of the present invention can be used to quickly and simply predict and evaluate the ability of lithium-ion batteries equipped with manned submersibles to complete effective power supply. The lithium-ion batteries tested by this method can safely discharge under cyclic load in a water pressure or seawater pressure environment of 0 to 11,000 meters with a pressure resistance of 114 MPa and a maximum limit pressure resistance of 127 MPa.

[0027] This method can provide safe and reliable energy and power guarantee for the safe operation of manned submersibles in the pressure range of 0 to 11,000 meters under sea water. It can be used as a power battery in deep-sea manned submersibles, and can also be applied to other deep-sea unmanned submersibles, deep-sea pre-placed platforms, as well as deep-sea underwater robots, deep-sea power stations, deep-sea communication base stations and other fields, but is not limited to these. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The comparison between the normal-pressure impedance of the fully-charged battery cell before voltage application and the fitting result in Example 1 of the present invention;

[0029] Figure 2 This is a voltage increase curve of the pressure device during the battery cell pressure resistance performance test in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention summarizes the preparation of tens of thousands of lithium-ion batteries for manned submersibles, the assessment of their piezoelectric performance, and the feedback of the actual avionics performance of the batteries in the "Struggler" submersible and finds the following conditions:

[0031] (1) After coupling the continuous low temperature environment of a manned submersible with the thermal field generated by the different operating conditions of its supporting power battery pack, the actual operating environment temperature of the lithium-ion battery is between 0 and 5°C. Combined with the low-temperature transport characteristics of lithium ions exhibited by the linear small molecule electrolyte formula in the flexible pressure-bearing structure of the 127MPa lithium-ion battery, it is determined that the ambient temperature range for predicting the discharge performance of batteries for manned submersibles can be set between -4°C and 5°C.

[0032] (2) In-depth analysis of the actual voltage change rate during the diving and surfacing of manned submersibles in various countries around the world and the ultimate tolerance of the pressure-bearing materials inside lithium-ion batteries, and found that the ohmic internal resistance R of lithium-ion batteries accurately fitted by AC impedance spectroscopy 耐压 The change law under 127MPa pressure environment, the flexible pressure-bearing structure design of the battery and the battery capacity are closely related, and the flexible pressure-bearing structure design of the battery is closely related to the ohmic internal resistance R under normal pressure. 常压 Therefore, the boundary conditions of the above parameters can be accurately summarized through the measured data as a basis for shortening the test cycle and ensuring the reliability of the test.

[0033] The present invention is further described in detail below in conjunction with the embodiments, but it is not intended to limit the protection scope of the present invention.

[0034] The boundary conditions and quantitative correlation of the parameters in the electrical performance test of the lithium-ion battery for manned submersibles described in the present invention are achieved through the following technical solutions.

[0035] First, the ohmic internal resistance R after testing by this method 常压The lithium-ion battery cells of 1mΩ to 2mΩ have the ability to directly withstand pressure in a water pressure environment of 0 to 11,000 meters or seawater pressure, and can meet the maximum limit voltage transformation rate of 2MPa / min. The specific pressure resistance electrical performance test process includes the following steps.

[0036] The first step is to visually inspect the appearance of the lithium-ion battery, which must meet the following requirements: no particles on the surface of the battery (including particles in the inner layer of the aluminum-plastic film), no traces of electrolyte, wrinkles, damage, or deformation.

[0037] In the second step, the AC impedance spectrum of the battery cell is tested in the fully charged state to obtain the ohmic impedance R related to the transport of lithium ions and electrons through the electrolyte, porous diaphragm, and active material particles in the lithium-ion battery. 常压 , R 常压 It should be between 1mΩ and 2mΩ.

[0038] The principle is that the present invention has found that R 常压 In this range, lithium-ion batteries have a high grouping rate in the process of matching the total energy required by manned submersibles. In addition, the 127MPa withstand voltage variation range associated with the selection of raw materials and battery structure design in the pressure-bearing design can be accurately predicted, and the lossless withstand voltage relaxation stability period can be accurately shortened to 5 weeks. 常压 Within this range, lithium-ion battery cells can also be widely used in various types of manned submersibles.

[0039] The third step is to conduct low-temperature electrical performance tests on fully charged lithium-ion batteries in the range of -4°C to 5°C, including normal pressure low-temperature tests and a 127MPa withstand pressure low-temperature electrical performance test. The battery capacity before and after the test must meet Q 耐压a / Q 常压 ≥99%, and the AC ohmic impedance R satisfies: 0.5≤ R 耐压a / R常压 ≤0.9, where a≥5.

[0040] The principle of this step is R 常压 The lithium-ion battery cell should be between 1mΩ and 2mΩ. 耐压a / R常压 When <0.5, the microstructure dissection and theoretical calculation of the internal resistance of the battery monomer show that the probability of irreversible damage increases, and R 耐压a / R常压 When it is greater than 0.9, the pressure resistance flexibility of lithium-ion batteries is poor, and the battery cycle performance will decay rapidly.

[0041] Lithium-ion batteries undergoing pressure resistance electrical performance tests must undergo the above three steps in sequence and must meet the test requirements at the same time. Only then can the lithium-ion battery pass the electrical performance test for lithium-ion batteries for manned submersibles.

[0042] In the second aspect, the present invention provides a low-temperature electrical performance test of about 0°C as described in the first aspect above, which should be carried out at a temperature of -4 to 5°C. The electrical performance test under normal pressure should be carried out in an environment of relative humidity of 25 to 85% and air pressure of 90 to 108 kPa. The 127 MPa pressure-resistant low-temperature test should be carried out in a pressure simulation device (simulated pressure cylinder), including the following specific steps.

[0043] The first step is to charge the battery at a constant current of 0.2C according to the rated capacity of the lithium-ion battery, stop charging after charging to the rated cut-off voltage, and let the battery stand for ≥30 minutes before connecting the battery to the AC impedance test device to perform an AC impedance spectrum scan under open circuit voltage conditions. The AC frequency scanning range should be no less than 0.01Hz~0.1MHz, and the ohmic internal resistance R obtained after fitting the AC impedance spectrum obtained by the test 常压 , where the spectrum fitting accuracy should be above 90%.

[0044] In the second step, the lithium-ion battery is discharged at a constant current rate of 0.2C at the rated capacity, and the discharge is stopped after the rated discharge cut-off voltage is reached to obtain the normal pressure discharge capacity Q 常压 .

[0045] The third step is to fully charge the lithium-ion battery using the same constant current charging method as the first step and then let it stand for ≥ 30 minutes.

[0046] The fourth step is to place the lithium-ion battery in a pressure simulation device and connect the positive and negative electrodes to an external circuit.

[0047] Step 5: Start the pressurization system. Pressurize to 127MPa at a rate of about S1, S1 = (0MPa / min ~ 2MPa / min), and maintain pressure for T1 minute, T1 ≥ 310 minutes.

[0048] Step 6: When the pressure simulation device reaches 127 MPa, the lithium-ion battery is subjected to an AC impedance spectrum scan under open circuit voltage conditions, and the ohmic internal resistance R 耐压a , where the AC frequency scanning range and spectrum fitting accuracy are the same as the first step.

[0049] Step 7: In the environment of 127MPa, the lithium-ion battery cell is discharged at a constant current rate of 0.2C at the rated capacity, and the discharge is stopped after the rated discharge cut-off voltage is reached. The obtained a-th withstand voltage discharge capacity is recorded as Q 耐压a .

[0050] Step 8. The pressure simulation device is depressurized to normal pressure, with a depressurization rate of S2, S2 ≥ 1 MPa / min.

[0051] Step 9. Remove the battery from the pressure simulation device and let it rest for 30 minutes.

[0052] Step 10: Repeat steps 3 to 9 a times, where a ≥ 5 times.

[0053] In a third aspect, the five cycles described in the first aspect provided by the present invention are the minimum number of piezoelectric performance tests, and also include more than five test cycles with the same steps.

[0054] In the fourth aspect, the voltage increase rate and voltage reduction rate described in the first aspect provided by the present invention, 2MPa / minute is the minimum rate for the piezoelectric performance test, and also includes rapid voltage increase and rapid voltage reduction rates greater than 2MPa / minute.

[0055] In a fifth aspect, the present invention provides the constant current discharge at a rated capacity rate of 0.2C as described in the second aspect, where 0.2C is the minimum discharge rate for the piezoelectric performance test, and also includes a discharge rate greater than 0.2C.

[0056] In a sixth aspect, the present invention provides a method for testing the electrical properties of lithium-ion batteries for manned submersibles as described in the first aspect, wherein the lithium-ion battery is a ternary nickel-cobalt-manganese battery or a ternary nickel-cobalt-aluminum battery or a lithium iron phosphate or lithium titanate battery or a lithium-rich battery.

[0057] Example 1

[0058] 100 full-sea-depth lithium iron phosphate battery cells with a specification of 48Ah (China Shipbuilding Industry Corporation 712 Research Institute) were selected for the pressure resistance and electrical performance test. The specific operation steps are as follows:

[0059] ① Use a charging and discharging cabinet (accuracy 0.01A, China Shipbuilding Industry Corporation 712 Research Institute) to charge the battery cells to be tested according to the charging procedure: 1 atmosphere, 25°C, constant current charging at 0.2C, stop charging when the battery cell voltage reaches 3.60V. After charging, let it stand for 30 minutes.

[0060] ② Connect the charged battery cell to an AC impedance tester (frequency accuracy 0.0001Hz, maximum frequency range 2MHz) and perform an AC impedance spectrum scan under open circuit voltage conditions. The AC frequency scan range is set to 0.01Hz to 0.1MHz, and scan from high frequency to low frequency. After the test, simulate the spectrum. The simulation results are as follows: Figure 1 As shown in the figure, when the fitting accuracy reaches 95%, record the R 常压 .

[0061] ③Discharge the lithium-ion battery at a constant current rate of 0.2C at the rated capacity, and stop discharging after the rated discharge cut-off voltage, and obtain the normal pressure discharge capacity Q 常压 .

[0062] ④ Use the same constant current charging method as in ① to fully charge the lithium-ion battery and let it stand for ≥30 minutes.

[0063] ⑤ Place the charged battery cell into the pressure tank of the deep-sea pressure simulation device (accuracy 115MPa / 2MPa), lead the positive and negative electrode measurement lines to the charge and discharge cabinet (accuracy 0.01A, China Shipbuilding Industry Corporation 712 Research Institute), turn on the deep-sea pressure simulation device, pressurize to 127MPa at a rate of 2MPa / min, and maintain the pressure for 320 minutes. See the attached pressure rise curve Figure 2 .

[0064] ⑥ When the pressure simulation device reaches 127MPa, the lithium-ion battery is subjected to an AC impedance spectrum scan under open circuit voltage conditions, and the ohmic internal resistance R 耐压1 , where the AC frequency scanning range and spectrum fitting accuracy are the same as the first step.

[0065] ⑦ Under 127MPa environment, the lithium-ion battery monomer is discharged at a constant current rate of 0.2C at the rated capacity, and the discharge is stopped after the rated discharge cut-off voltage is reached. The first withstand voltage discharge capacity obtained is recorded as Q 耐压1 .

[0066] ⑧The pressure simulation device is depressurized to normal pressure at a rate of 2 MPa / min.

[0067] ⑨ Remove the battery from the pressure simulation device and let it rest for 30 minutes.

[0068] Repeat ④ to ⑨ 5 times to get the 5th Q 耐压5 and R 耐压5 .

[0069] The above 100 full-sea-depth lithium iron phosphate batteries 耐压5 / Q 常压 The values ​​of <99% are recorded as A1 battery cells, and the rest are recorded as B1. The number of each type of battery cells is shown in the following table (Appendix 1: The number of battery cells that passed the test after each type of pressure resistance test).

[0070] .

[0071] A battery charging and discharging cabinet (accuracy 0.01A, 712 Institute of China Shipbuilding Industry Corporation) was used to charge Class B1 battery cells at a normal pressure battery capacity of 0.2C, and then discharged at a normal pressure battery capacity of 0.5C under the pressure environments of 115MPa and 127MPa required for a 10,000-meter manned deep-sea submersible for 500 weeks. During the 500-week test, the number of Class B1 battery cells whose discharge capacity dropped to 32.8Ah or less was divided by the total number of Class B1 battery cells, which was recorded as C1, as shown in the following table (Appendix 2: The probability that the capacity of the battery that has passed the test does not meet the requirements after 500 weeks of pressure resistance cycling).

[0072] .

[0073] Comparative Example 1

[0074] 100 full-sea-depth lithium iron phosphate battery cells with a specification of 48Ah (from the 712th Institute of China Shipbuilding Industry Corporation) were selected for the pressure resistance and electrical performance test. The specific operation steps are as follows.

[0075] ① Use a charging and discharging cabinet (accuracy 0.01A, China Shipbuilding Industry Corporation 712 Research Institute) to charge the battery cells to be tested according to the charging procedure: 1 atmosphere, 25°C, constant current charging at 0.2C, stop charging when the battery cell voltage reaches 3.60V. After charging, let it stand for 30 minutes.

[0076] ② Place the charged battery cell into the pressure tank of the deep-sea pressure simulation device (accuracy: 115MPa / 0.1MPa), connect the positive and negative electrode measurement lines to the charge and discharge cabinet (accuracy: 0.01A, 712th Institute of China Shipbuilding Industry Corporation), turn on the deep-sea pressure simulation device, and perform the pressure resistance electrical performance test according to the table below (pressure resistance performance test boost procedure).

[0077] .

[0078] After the voltage of the lithium-ion battery cell was increased for 30 minutes, the battery cell was discharged at a constant current of 0.2C until the voltage of the battery cell reached 2.65V and the discharge was stopped. The battery cell was left standing for 30 minutes.

[0079] ③ Repeat steps ① to ② for 50 cycles, and record the 50th discharge capacity Q50 and the first discharge capacity Q0.

[0080] Among the above 100 full-sea-depth lithium iron phosphate batteries, those with Q50 / Q0 values ​​less than 98% are recorded as A2 battery cells, and the remaining battery cells are recorded as B2. The number distribution of each type of battery cells is shown in Appendix 1.

[0081] A battery charging and discharging cabinet (accuracy 0.01A, 712 Institute of China Shipbuilding Industry Corporation) was used to charge Class B1 battery cells at a normal pressure battery capacity of 0.2C, and a discharge cycle test of 500 weeks was carried out at a normal pressure battery capacity of 0.5C under a pressure environment of 115MPa and 127MPa required by a 10,000-meter manned deep-sea submersible. During the 500-week test, the number of Class B2 battery cells whose discharge capacity dropped to 32.8Ah or less was divided by the total number of Class B2 battery cells, which was recorded as C2, as shown in Appendix 2.

[0082] The lithium-ion battery cells of the same specifications and the same manufacturer used in Example 1 and Comparative Example 1 can be shown in Appendix 1 that both methods can detect the pressure-resistant electrical performance of the battery. The pressure-resistant electrical performance test methods provided in Example 1 of the present invention and Comparative Example 1 of the present invention have simpler detection steps and shorter test cycles. Appendix 2 can show that compared with Example 1 and Comparative Example 1 provided by the present invention, they have the same detection and evaluation effect. The battery cells tested for the electrical performance of lithium-ion batteries for manned submersibles provided by the first aspect of the present invention all achieved a battery capacity retention rate of ≥80% during the actual test of 500-week pressure-resistant cycles, and the probability of batteries not meeting the electrical performance requirements is 0%.

[0083] It can be seen from Appendix 2 that compared with Comparative Example 1, the battery tested through the piezoelectric performance test provided by the present invention has the same prediction effect as Comparative Example 1, but the detection cycle is significantly shortened, which can greatly reduce the preparation cycle and assessment time of lithium-ion batteries for manned submersibles, and is of great significance for the long-cycle operation of lithium-ion battery packs in the deep sea.

[0084] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for testing the electrical performance of lithium-ion batteries for manned submersibles, characterized in that: The following steps are included The first step is to visually inspect the appearance of the lithium-ion battery. The battery surface must be free of particles, electrolyte traces, wrinkles, damage, and deformation. The second step is to conduct an AC impedance spectrum test on the battery cell in a fully charged state to obtain the ohmic impedance R of the lithium-ion battery. 常压 , R 常压 Should be between 1mΩ and 2mΩ; The third step is to conduct a low-temperature electrical performance test of the fully charged lithium-ion battery at a temperature of -4 to 5°C, a relative humidity of 25 to 85%, and an air pressure of 90 to 108 kPa in a 127 MPa withstand-pressure low-temperature test in a pressure simulation device: a normal pressure low-temperature test and a 127 MPa withstand-pressure low-temperature electrical performance test, a ≥ 5, and the battery capacity before and after the test must meet Q 耐压a / Q 常压 ≥99%, and the AC ohmic impedance R satisfies 0.5≤R 耐压a / R 常压 ≤0.9; specifically including the following steps: Step 1: Charge the battery at a constant current of 0.2C rate according to the rated capacity of the lithium-ion battery, stop charging after charging to the rated cut-off voltage, and let the battery stand for ≥30 minutes before connecting the battery to an AC impedance tester to perform an AC impedance spectrum scan under open circuit voltage conditions. The AC frequency scanning range is 0.01Hz to 0.1MHz. The ohmic internal resistance R obtained after fitting the AC impedance spectrum obtained by the test has a spectrum fitting accuracy of more than 90%; Step 2: Discharge the lithium-ion battery at a constant current rate of 0.2C at the rated capacity until the rated discharge cut-off voltage is reached, and then the normal pressure discharge capacity Q is obtained. 常压 ; Step 3. Follow step 1 to fully charge the lithium-ion battery and let it sit for ≥ 30 minutes. Step 4, placing the lithium-ion battery in a pressure simulation device, and connecting the positive and negative electrodes to an external circuit; Step 5: Start the pressure simulation device, pressurize to 127MPa at a pressurization rate of S1 = 0-2MPa / min, and maintain the pressure for T1 ≥ 310 minutes; Step 6: When the pressure simulation device reaches 127 MPa, the lithium-ion battery is subjected to an AC impedance spectrum scan under open circuit voltage conditions, and the ohmic internal resistance R 耐压a ; Step 7: At 127 MPa, the lithium-ion battery cell is discharged at a constant current rate of 0.2C at the rated capacity, and the discharge is stopped after the rated discharge cut-off voltage is reached. The obtained a-th withstand voltage discharge capacity is recorded as Q 耐压a ; Step 8: The pressure simulation device releases pressure to normal pressure at a pressure release rate of S2 ≥ 1 MPa / min; Step 9, remove the battery from the pressure simulation device and let it rest for 30 minutes; Step 10: Repeat steps 3 to 9 a times, where a ≥ 5 times.

2. The method for testing the electrical performance of a lithium-ion battery for a manned submersible according to claim 1, characterized in that: The lithium-ion battery is a ternary nickel-cobalt-manganese battery, a ternary nickel-cobalt-aluminum battery, a lithium iron phosphate battery, a lithium titanate battery or a lithium-rich battery.

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