Charge-discharge cycle test method of high-specific-energy metal lithium battery for solar unmanned aerial vehicle

Abstract

The invention discloses a charge-discharge cycle test method for a high-specific-energy metal lithium battery for a solar unmanned aerial vehicle, and the method comprises the steps: determining a charge-discharge test environment temperature, a charge rate and a discharge rate, and determining that a single battery is in a discharge state; starting a power supply of charging and discharging test equipment, and setting a single battery charging and discharging cycle test program; putting the monomers into a clamp tool; the single battery is charged according to the charging rate, the clamp tool continuously applies first pressure during charging, and the value of the first pressure is gradually increased from the initial pressure value along with the charging time; standing for a third time length; the single batteries are discharged according to the discharge rate, second pressure is continuously applied to the clamp tool in the discharge period, and the value of the second pressure is gradually reduced along with the increase of the discharge time; standing for a fourth time length; and the charging and discharging process is repeatedly executed to reach the cycle test times. The method can improve the cycle test efficiency of the metal lithium battery pack, reduce the test cost, and reduce the risk of fire and explosion of the battery pack in the test process.

Description

Technical Field

[0001] The present invention relates to the field of solar-powered unmanned aerial vehicle energy storage batteries, and more specifically, to a charge-discharge cycle testing method for a high-energy-density metal lithium battery for a solar-powered unmanned aerial vehicle. Background Art

[0002] With the development of science and technology, metal lithium batteries are increasingly used in the field of solar drones. Soft-pack metal lithium battery cells are a new type of structure that is being developed and matched for solar drones. The metal lithium battery cells in this structure have high power output characteristics and high specific energy. The measured cycle life of metal lithium battery cells can reach 80 cycles, or even more than 100 cycles. However, when metal lithium battery cells are combined into metal lithium battery packs, their cycle performance can only reach 30 cycles or less. The method of using ordinary metal clamps for charge and discharge testing cannot detect this defect in the early stage before the single cells are grouped or installed. After the single cells are grouped or installed, after multiple charge and discharge cycles, the metal lithium battery may have an expansion tension that exceeds the combined clamping force. In this case, the lithium dendrites in the expanded space inside the metal lithium battery may pierce the diaphragm, causing a short circuit in the battery and a battery fire. At present, the charge and discharge test method of metal lithium battery combination is mainly realized by actually making prototypes for cycle testing. For example, after being compressed with a preload force of 0N to 50000N, in the subsequent test process, the pressure value is passively affected by the installation state of the test battery and presents uncontrolled changes. The battery cycle life is predicted by passively detecting the relationship between cycle life and pressure. However, this method wastes resources, manpower and time for various types and forms of metal lithium battery cells and combinations, and also has the risk of expanding dangerous situations and impact range after grouping. Summary of the invention

[0003] The purpose of the present invention is to propose a charge and discharge cycle test method for a high specific energy metal lithium battery for a solar drone, so as to improve the cycle test efficiency of the metal lithium battery pack, reduce the test cost, and also reduce the risk of fire and explosion of the battery pack during the test.

[0004] To achieve the above object, the present invention proposes a charge and discharge cycle test method for a high specific energy metal lithium battery for a solar drone, comprising:

[0005] S1: Determine the charge and discharge test environment temperature, charge rate and discharge rate according to the type of the metal lithium battery cell to be tested, and confirm that the metal lithium battery cell to be tested is in a discharge state;

[0006] S2: Turn on the power of the charge and discharge test equipment, and set the metal lithium battery single charge and discharge cycle test program according to the charge rate and the discharge rate;

[0007] S3: placing the metal lithium battery cell to be tested into a fixture for charge and discharge cycle testing, and setting an initial pressure value and a fully charged pressure value applied by the fixture to the metal lithium battery cell;

[0008] S4: performing a charge-discharge cycle test procedure at the charge-discharge test environment temperature, charging the metal lithium battery cell at the charge rate for a first period of time, during which the fixture continuously applies a first pressure to the metal lithium battery cell, and the value of the first pressure gradually increases from the initial pressure value as the charging time increases;

[0009] S5: leaving the metal lithium battery cell to stand for a third period of time, waiting for the internal polarization of the cell cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature;

[0010] S6: discharging the metal lithium battery cell at the discharge rate for a second time period, during which the fixture continuously applies a second pressure to the metal lithium battery cell, and the value of the second pressure gradually decreases as the discharge time increases;

[0011] S7: leaving the metal lithium battery cell to stand for a fourth period of time, waiting for the internal polarization of the cell cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature;

[0012] S8: Repeat S4 to S7 until the set number of cycle tests is reached and the test is completed.

[0013] Optionally, in step S4, the relationship between the value P1 of the first pressure and the charging time is:

[0014] P1=(P max -P min )×t1×C1+P min ;

[0015] Among them, P min is the initial pressure value, P max is the fully charged pressure value of the monomer, t1 is the charging time, C1 is the charging rate, and 0<t1≤1 / C1.

[0016] Optionally, in step S6, the relationship between the value P2 of the second pressure and the charging time is:

[0017] P2=P max -(P max -P min )×t2×C2;

[0018] Wherein, t2 is the charging time, C2 is the discharge rate, and 0<t2≤1 / C2.

[0019] Optionally, in step S1, the discharge state is an empty state in which the SOC of the metal lithium battery cell is 0; and the range of the charge and discharge test environment temperature is 20°C to 30°C.

[0020] Optionally, in step S2, the charging rate ranges from 0.05 to 1, and the discharging rate ranges from 0.05 to 10.

[0021] Optionally, in step S3, the initial pressure value ranges from 0.2 MPa to 0.3 MPa.

[0022] Optionally, in step S3, the range of the fully charged pressure value of the single cell is 3 MPa to 6 MPa.

[0023] Optionally, the third duration and the fourth duration range from 20 minutes to 40 minutes.

[0024] Optionally, the setting items of the charge and discharge cycle test program include: charging rate, charging time, standing time, discharge rate, discharge time, number of cycles, and test protection upper limit voltage, lower limit voltage and protection temperature.

[0025] Optionally, during the repeated execution of the cycle test of S4-S7, the test data and appearance status of the single unit are observed in real time, and the test is stopped immediately if any abnormality is found.

[0026] The beneficial effects of the present invention are:

[0027] (1) The present invention adopts a method of continuous pressure application adapted to the corresponding battery type and working conditions combined with temperature control to perform charge and discharge tests, which can expose and eliminate potential internal short circuit hazards after grouping or installation in advance.

[0028] (2) The present invention adopts the expansion tension of the bonding charge and discharge process combined with the adaptive continuous pressure of the charge and discharge rate conditions, which can not only simulate the actual use of metal lithium battery cells after being grouped, examine the battery's charge and discharge cycle performance and expose defects, but also avoid the unnecessary resource, manpower and time consumption of the existing means that must be grouped for performance confirmation.

[0029] (3) Before charging, the present invention adjusts the initial pressure for pre-pressing, so that the metal lithium single battery reaches a stable state before performing the charge and discharge test. Compared with the existing testing methods, it is safer, more accurate and reliable.

[0030] (4) The present invention uses the charge and discharge rate as one of the variables for continuous pressure regulation, and can efficiently achieve the purpose of the most practical pressure regulation through a reasonable calculation method.

[0031] The system of the present invention has other characteristics and advantages, which will be apparent from the drawings incorporated herein and the following detailed description, or will be described in detail in the drawings incorporated herein and the following detailed description, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which like reference numerals generally represent like components.

[0033] Figure 1 A flow chart showing the steps of a charge and discharge cycle test method for a high specific energy metal lithium battery for a solar drone according to the present invention is shown. DETAILED DESCRIPTION

[0034] The present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0035] like Figure 1 As shown, a charge and discharge cycle test method of a high specific energy metal lithium battery for a solar drone according to the present invention comprises:

[0036] S1: Determine the charge and discharge test environment temperature, charge rate and discharge rate according to the type of the metal lithium battery cell to be tested, and confirm that the metal lithium battery cell to be tested is in a discharge state;

[0037] In this step, the discharge state is the empty state of the metal lithium battery cell SOC is 0; the optional range of the charge and discharge test environment temperature is 20°C to 30°C, preferably 25°C.

[0038] This step confirms that the metal lithium battery cell is in a discharged state before testing, and determines the charge and discharge environment temperature T and the charge rate (C1) and discharge rate (C2) according to the cell type.

[0039] S2: Turn on the power of the charge and discharge test equipment, and set the metal lithium battery single charge and discharge cycle test program according to the charge rate and discharge rate;

[0040] Depending on the type of battery cell, the range of charge rate is generally 0.05 to 1, and the range of discharge rate is generally 0.05 to 10. The settings of the charge and discharge cycle test program include: charge rate (C1), charge time, standstill time, discharge rate, discharge time (C2), number of cycles, and test protection upper and lower voltage limits and protection temperature.

[0041] This step sets the test conditions in the single cell charge and discharge program based on the determined charge rate (C1) and discharge rate (C2) determined in step S1, and sets the charge and discharge time, interval rest time, etc., and sets the corresponding test protection conditions according to the parameter type of the metal lithium battery single cell.

[0042] S3: placing the metal lithium battery cell to be tested into a fixture for charge and discharge cycle testing, and setting an initial pressure value and a fully charged pressure value applied by the fixture to the metal lithium battery cell;

[0043] In this step, the initial pressure value ranges from 0.2MPa to 0.3MPa, and the pressure value of the fully charged single cell ranges from 3MPa to 6MPa.

[0044] Place the metal lithium battery cell to be tested into the test fixture and set the fixture to apply the initial pressure (or the discharge pressure of the cell) P min and the single cell fully charged pressure (maximum pressure) P max , P min The value is between 0.2MPa and 0.3MPa, and the maximum pressure P max In the range of 3Mpa to 6Mpa, it can be determined according to the type of metal lithium battery monomer to be tested. After the setting is completed, adjust the fixture to apply the initial pressure P min , confirm that the fixture is clamped effectively and there is no possibility of loosening or sliding out, and the test preparation is complete.

[0045] S4: Under the charge and discharge test environment temperature, the charge and discharge cycle test program is executed, and the metal lithium battery cell is charged at a charge rate for a first time period, during which the fixture tooling continuously applies a first pressure to the metal lithium battery cell, and the value of the first pressure gradually increases from an initial pressure value as the charging time increases;

[0046] In this step, the relationship between the value of the first pressure P1 and the charging time is:

[0047] P1=(P max -P min )×t1×C1+P min ;

[0048] Among them, P min is the initial pressure value, P maxis the pressure value of the fully charged single cell, t1 is the charging time (in hours), C1 is the charging rate, 0<t1≤1 / C1.

[0049] Specifically, the charging process is prepared, and the clamp continuously applies pressure P1=(P max -P min )×t1×C1+P min , start the charge and discharge program, and first perform a charge test on the metal lithium battery cell at a charge rate of C1. The maximum value of the test time t1 must not be greater than 1 / C1.

[0050] S5: leaving the metal lithium battery cell to stand for a third period of time, waiting for the internal polarization of the cell cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature (i.e., the test environment temperature);

[0051] In this step, the third time length ranges from 20 min to 40 min, preferably 30 min.

[0052] Specifically, the test enters the rest time t3 according to the set program, and the setting value of t3 is determined by the type of metal lithium battery monomer tested to ensure that the polarization effect, charge state and temperature of the monomer battery do not affect the subsequent test state.

[0053] S6: discharging the metal lithium battery cell for a second time at a discharge rate, during which the fixture continuously applies a second pressure to the metal lithium battery cell, and the value of the second pressure gradually decreases as the discharge time increases;

[0054] In this step, the relationship between the value of the second pressure P2 and the charging time is:

[0055] P2=P max -(P max -P min )×t2×C2;

[0056] Wherein, t2 is the charging time (in hours), C2 is the discharge rate, and 0<t2≤1 / C2.

[0057] Specifically, the discharge process is prepared, and the clamp continuously applies pressure P=P during the discharge process. max -(P max -P min )×t2×C2, continue the charge and discharge procedure, and perform discharge test on the metal lithium battery cell at the discharge rate C2. The maximum value of the test time t2 must not be greater than 1 / C2.

[0058] S7: leaving the metal lithium battery cell to stand for a fourth period of time, waiting for the internal polarization of the cell cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature;

[0059] In this step, the fourth time length ranges from 20 min to 40 min, preferably 30 min.

[0060] Specifically, the test enters the rest time t4 according to the set program, and the setting value of t4 is determined by the type of metal lithium battery monomer tested to ensure that the polarization effect, charge state and temperature of the monomer battery do not affect the subsequent test state.

[0061] S8: Repeat S4 to S7 until the set number of cycle tests is reached and the test is completed.

[0062] Specifically, the charge and discharge cycles of steps S4 to S7 are performed according to the set charge and discharge cycle test program until the set number of cycle tests is reached and the test is completed. The number of cycles is determined by the type of metal lithium battery monomer tested and the project target used. During the cycle test, the monomer test data and appearance status are observed in real time. If there is any abnormality, the test is stopped immediately.

[0063] The advantages of the charge and discharge cycle test method of the metal lithium battery of the present invention are:

[0064] (1) A method of continuous clamping and pressing adapted to the corresponding battery type and working conditions combined with ambient temperature control is adopted to expose and eliminate in advance the potential internal short circuit and excessive expansion of the metal lithium battery cells during use after they are grouped, thereby solving the technical problem that the existing single-cell charge and discharge cycle test of high-energy lithium-ion batteries for solar drones cannot simulate the actual use conditions.

[0065] (2) A method of actively and dynamically applying controllable pressure to different charge states is used to test the cycle life, thereby achieving the technical effect of replacing the combined battery cycle life test.

[0066] (3) The expansion tension during the charge and discharge process is combined with the adaptive continuous pressure of the charge and discharge rate conditions. This can not only simulate the actual use of metal lithium battery cells after being grouped, examine the battery's charge and discharge cycle performance and expose defects, but also avoid the unnecessary resource, manpower and time consumption of the existing means that must be grouped for performance confirmation.

[0067] (4) The charge and discharge rate is used as one of the variables for continuous pressure regulation, and a reasonable calculation method can be used to efficiently achieve the purpose of pressure regulation that best fits the actual situation. Before charging, the present invention adjusts the initial pressure for pre-pressing, so that the state of the metal lithium single battery reaches a stable state before performing the charge and discharge test. Compared with the existing testing methods, the test is safer, more accurate and reliable.

[0068] (5) Through a reasonable calculation and testing method, the technical problem of low efficiency in verifying the optimal combination of high-energy-density lithium-ion batteries for solar drones was solved. The technical problem of the inability of the charge and discharge cycle test of high-energy-density metal lithium batteries for drones to simulate actual operating conditions was solved, and the efficiency of testing the optimal combination of high-energy-density metal lithium batteries for drones was improved.

[0069] The solution of the present invention is further explained below through a specific embodiment.

[0070] Example:

[0071] This embodiment provides a charge and discharge cycle test method for a high specific energy lithium metal battery for a solar drone, comprising the following steps:

[0072] Step 1: Select a high specific energy 13Ah lithium metal battery cell, set the charge rate to 0.2C, set the discharge rate to 0.2C, and control the charge and discharge environment temperature at 25°C;

[0073] Step 2, turn on the power of the charge and discharge test equipment, set the metal lithium battery single charge and discharge cycle test program: the battery single is first charged at 0.2C for 5 hours, let it stand for 0.5 hours, then discharged at 0.2C for 5 hours, let it stand for 0.5 hours, repeat the above process 60 times, and set the protection upper limit voltage to 4.5V, the lower limit voltage to 2.7V, and the protection temperature to 60℃;

[0074] Step 3: Place the lithium metal battery cell to be tested into the test fixture. The initial pressure of the fixture is set to 0.3Mpa, and the pressure of the cell in a fully charged state is 3Mpa. Adjust the initial pressure of the fixture to 0.3Mpa, and confirm that the fixture is clamped effectively without the possibility of loosening and slipping. The test preparation is complete.

[0075] Step 4, the metal lithium battery cell is charged at 0.2C for 5 hours, during which the pressure applied by the fixture changes continuously with the charging time, following the relationship of pressure P = (3Mpa-0.3Mpa) × t1 × 0.2 + 0.3Mpa, and the maximum value of the charging time t1 does not exceed 1 / C1 = 5h;

[0076] Step 5: The lithium metal battery cell is left to stand for 0.5 hours according to the set program, waiting for the internal polarization of the cell to disappear, the charge state to balance, and the temperature to return to normal temperature;

[0077] Step 6, the metal lithium battery cell is discharged at 0.2C for 5 hours, during which the pressure applied by the fixture changes continuously with the charging time, following the relationship of pressure P = 3Mpa-(3Mpa-0.3Mpa)×t2×0.2, and the maximum value of the discharge time t2 does not exceed 1 / C2=5h;

[0078] Step 7, the metal lithium battery cell is left to stand for 0.5h according to the set program, waiting for the internal polarization of the cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature;

[0079] Step 8. Repeat steps 4 to 7 and perform charge and discharge cycles for 60 times according to the specified cycle test number. During this period, observe the single cell test data and appearance status. If there is any abnormality, stop the test immediately.

[0080] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A charge and discharge cycle test method for a high specific energy metal lithium battery for a solar drone, characterized in that: include: S1: Determine the charge and discharge test environment temperature, charge rate and discharge rate according to the type of the metal lithium battery cell to be tested, and confirm that the metal lithium battery cell to be tested is in a discharge state; S2: Turn on the power of the charge and discharge test equipment, and set the metal lithium battery single charge and discharge cycle test program according to the charge rate and the discharge rate; S3: placing the metal lithium battery cell to be tested into a fixture for charge and discharge cycle testing, and setting an initial pressure value and a fully charged pressure value applied by the fixture to the metal lithium battery cell; S4: performing a charge-discharge cycle test procedure at the charge-discharge test environment temperature, charging the metal lithium battery cell at the charge rate for a first period of time, during which the fixture continuously applies a first pressure to the metal lithium battery cell, and the value of the first pressure gradually increases from the initial pressure value as the charging time increases; S5: leaving the metal lithium battery cell to stand for a third period of time, waiting for the internal polarization of the cell cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature; S6: discharging the metal lithium battery cell at the discharge rate for a second time period, during which the fixture continuously applies a second pressure to the metal lithium battery cell, and the value of the second pressure gradually decreases as the discharge time increases; S7: leaving the metal lithium battery cell to stand for a fourth period of time, waiting for the internal polarization of the cell cell to disappear, the charge state to be balanced, and the temperature to return to normal temperature; S8: Repeat S4 to S7 until the set number of cycle tests is reached and the test is completed.

2. The charge-discharge cycle test method according to claim 1, characterized in that: In step S4, the relationship between the value of the first pressure P1 and the charging time is: P1=(P max -P min )×t1×C1+P min ; Among them, P min is the initial pressure value, P max is the fully charged pressure value of the monomer, t1 is the charging time, C1 is the charging rate, and 0<t1≤1 / C1.

3. The charge-discharge cycle test method according to claim 2, characterized in that: In step S6, the relationship between the value of the second pressure P2 and the charging time is: P2=P max -(P max -P min )×t2×C2; Wherein, t2 is the charging time, C2 is the discharge rate, and 0<t2≤1 / C2.

4. The charge-discharge cycle test method according to claim 1, characterized in that: In step S1, the discharge state is an empty state in which the SOC of the metal lithium battery cell is 0; the range of the charge and discharge test environment temperature is 20°C to 30°C.

5. The charge-discharge cycle test method according to claim 1, characterized in that: In step S2, the charging rate ranges from 0.05 to 1, and the discharging rate ranges from 0.05 to 10.

6. The charge-discharge cycle test method according to claim 1, characterized in that: In step S3, the initial pressure value ranges from 0.2 MPa to 0.3 MPa.

7. The charge-discharge cycle test method according to claim 1, characterized in that: In step S3, the range of the fully charged pressure value of the single cell is 3 MPa to 6 MPa.

8. The charge-discharge cycle test method according to claim 1, characterized in that: The third duration and the fourth duration range from 20 minutes to 40 minutes.

9. The charge-discharge cycle test method according to claim 1, characterized in that: The setting items of the charge and discharge cycle test program include: charge rate, charge time, rest time, discharge rate, discharge time, number of cycles, and test protection upper limit voltage, lower limit voltage and protection temperature.

10. The charge-discharge cycle test method according to claim 1, characterized in that: During the repeated execution of the cycle test of S4-S7, the single unit test data and appearance status are observed in real time. If any abnormality is found, the test is stopped immediately.

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