A high-rate cycling test method and system for lithium-ion batteries

Abstract

The present invention discloses a high-rate cycling test method and system for lithium-ion batteries, including performing 0%-100% SOC charge and discharge cycles on the lithium-ion battery for N weeks at a set cycling rate C and a set temperature T, obtaining dynamic charge and discharge curves and charge and discharge data, where the charge cut-off voltage is Vmax and the discharge cut-off voltage is Vmin; according to the dynamic charge and discharge curves, obtaining the voltage V1 corresponding to discharging to A% SOC and the voltage V2 corresponding to charging to B% SOC during cycling in the A%-B% SOC interval, and obtaining the charging cut-off current A1 according to the charge and discharge data; if V2 < Vmax, perform a cycling test between V1 and V2 at the set cycling rate C; if V2 = Vmax, discharge to the lower limit voltage V1 and charge to the upper limit voltage V2 at the set cycling rate C, and charge at a constant voltage until the cut-off current A1; this high-rate cycling test method uses a constant voltage or constant voltage and constant current method as the cut-off condition for charging to stop, meeting the possibility of voltage cut-off at different rates and improving the accuracy of the lithium-ion battery cycling test.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery preparation, and particularly relates to a high-rate cycle test method and system for lithium-ion batteries. Background Art

[0002] Lithium-ion batteries have been widely used due to their high energy density, long cycle life, high reversibility, and environmental friendliness. The performance of the battery largely determines the comprehensive performance of new energy vehicles. At the same time, the cycle life, as an important item for evaluating the performance of lithium-ion batteries, is related to the service life and matching of the battery.

[0003] At present, there are many types of lithium-ion battery cycle tests, which can be carried out according to different rates, different temperatures, and different SOC intervals and other test methods. In the different SOC interval tests, the test is generally terminated by capacity. However, when cycling in the interval, terminating the test by capacity requires re-determining the capacity every certain number of cycle weeks, and re-calibrating the capacity of the SOC interval according to the determined capacity, which makes the test operation complex and increases the test cycle. Summary of the Invention

[0004] Based on the technical problems existing in the background art, the present invention proposes a high-rate cycle test method and system for lithium-ion batteries, which improves the accuracy and test efficiency of the lithium-ion battery cycle test.

[0005] A high-rate cycle test method for lithium-ion batteries proposed by the present invention includes:

[0006] Under a set cycle rate C and a set temperature T, perform 0%-100% SOC charge and discharge cycles on the lithium-ion battery for N weeks to obtain dynamic charge and discharge curves and charge and discharge data, where the charge cut-off voltage is Vmax and the discharge cut-off voltage is Vmin;

[0007] According to the dynamic charge and discharge curves and charge and discharge data, obtain the voltage V1 corresponding to discharging to A% SOC and the voltage V2 corresponding to charging to B% SOC during cycling in the A%-B% SOC interval, and obtain the charge cut-off current A1 according to the charge and discharge data;

[0008] If V2 < Vmax, perform a cycle test between V1 and V2 at the set cycle rate C;

[0009] If V2 = Vmax, at the set cycle rate C, discharge to the lower limit voltage V1, charge to the upper limit voltage V2, and charge at a constant voltage until the cut-off current A1.

[0010] Further, performing a cycle test between V1 and V2 at the set cycle rate C specifically includes:

[0011] Constant voltage charge to voltage V2 at a set temperature T and a set cycle multiple C, and then rest for a set time t1;

[0012] Discharge to voltage V1 at the set cycle multiple C, and cycle the charge and discharge.

[0013] Further, at the set cycle multiple C, discharge to the lower limit voltage V1, charge to the upper limit voltage V2, and charge at a constant voltage until the cut-off current A1, specifically including:

[0014] According to the dynamic charge and discharge curve, obtain the corresponding cut-off current A1 when charging to B% SOC in the A%-B% SOC interval cycle;

[0015] Constant voltage charge to voltage V2 at a set temperature T and a set cycle multiple C, then constant current charge to the charge cut-off current A1, and rest for a set time t2;

[0016] Discharge to voltage V1 at the set cycle multiple C, and cycle the charge and discharge.

[0017] Further, the dynamic charge and discharge curve is obtained by a charge and discharge device.

[0018] Further, in the 0%-100% SOC charge and discharge cycle N weeks of the lithium-ion battery, specifically including:

[0019] Charge the lithium-ion battery at a set cycle multiple C and a set temperature T until the state of charge of the battery reaches 100% SOC and then stop charging;

[0020] Discharge the lithium-ion battery at a set cycle multiple C and a set temperature T until the state of charge of the battery reaches 0% SOC;

[0021] Cycle the charge and discharge more than N weeks to obtain the dynamic charge and discharge curve and charge data.

[0022] A high-rate cycle test system for lithium-ion batteries, including a curve acquisition module, an interval cycle charge and discharge module, a constant voltage charge and discharge module, and a constant voltage and constant current charge and discharge module;

[0023] The curve acquisition module is used to perform 0%-100% SOC charge and discharge cycle N weeks on the lithium-ion battery at a set cycle multiple C and a set temperature T, and obtain the dynamic charge and discharge curve and charge and discharge data, where the charge cut-off voltage is Vmax and the discharge cut-off voltage is Vmin;

[0024] The interval cyclic charge and discharge module is used to obtain the corresponding voltage V1 when discharging to A% SOC and the corresponding voltage V2 when charging to B% SOC under the cyclic charge and discharge in the A%-B% SOC interval according to the dynamic charge and discharge curve and charge and discharge data, obtain the charging cut-off current A1 according to the charge and discharge data. If V2 < Vmax, it enters the constant voltage charge and discharge module; if V2 = Vmax, it enters the constant voltage and constant current charge and discharge module;

[0025] The constant voltage charge and discharge module is used to perform cyclic tests between V1 and V2 at the set cycle ratio C;

[0026] The constant voltage and constant current charge and discharge module is used to discharge to the lower limit voltage V1 and charge to the upper limit voltage V2 at the set cycle ratio C, and charge at a constant voltage until the cut-off current A1.

[0027] Further, the constant voltage charge and discharge module includes a constant voltage charging unit and a first constant voltage discharging unit;

[0028] The constant voltage charging unit is used to charge at a constant voltage to the voltage V2 at the set temperature T and the set cycle ratio C, and hold for the set time t1;

[0029] The first constant voltage discharging unit is used to discharge to the voltage V1 at the set cycle ratio C and perform cyclic charge and discharge.

[0030] Further, the constant voltage and constant current charge and discharge module includes a cut-off current acquisition unit, a constant voltage and constant current charging unit, and a second constant voltage discharging unit;

[0031] The cut-off current acquisition unit is used to obtain the corresponding charging cut-off current A1 when charging to B% SOC under the cyclic charge and discharge in the A%-B% SOC interval according to the dynamic charge and discharge curve;

[0032] The constant voltage and constant current charging unit is used to charge at a constant voltage to the voltage V2 at the set temperature T and the set cycle ratio C, then charge at a constant current until the charging cut-off current A1, and hold for the set time t2;

[0033] The second constant voltage discharging unit is used to discharge to the voltage V1 at the set cycle ratio C and perform cyclic charge and discharge.

[0034] The advantages of a high-rate cycling test method and system for lithium-ion batteries provided by the present invention are as follows: In the structure of the present invention, a high-rate cycling test method and system for lithium-ion batteries are provided. The charge and discharge are based on the available capacity of the lithium-ion battery at a specific rate, avoiding the polarization problem caused by high rates when determining charge and discharge parameters based on the rated capacity of the lithium-ion battery, meeting the charge and discharge performance of the lithium-ion battery, and improving the accuracy of the cycle test of the lithium-ion battery; According to the cut-off voltage corresponding to different set cycle rates C, a constant voltage or constant voltage and constant current method is used as the cut-off condition for charging to stop, meeting the possibility of voltage cut-off at different rates and improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic structural diagram of the present invention;

[0036] Figure 2 is the dynamic charge and discharge curve of 3C / 3C;

[0037] Figure 3 is the dynamic charge and discharge curve of 20C / 20C at room temperature. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Next, the technical solutions of the present invention will be described in detail through specific embodiments. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0039] As Figure 1 shown, a high-rate cycling test method for lithium-ion batteries proposed by the present invention includes the following steps S1 to S4:

[0040] S1: At a set cycle rate C and a set temperature T, perform 0%-100% SOC charge and discharge cycles on the lithium-ion battery for N weeks to obtain a dynamic charge and discharge curve, where the charge cut-off voltage is Vmax and the discharge cut-off voltage is Vmin; Step S1 specifically includes steps S11 to S13:

[0041] S11: At a set cycle rate C and a set temperature T, charge the lithium-ion battery until the state of charge of the battery reaches 100% SOC and then stop charging;

[0042] The cycle rate C and the set temperature T can be set according to actual requirements.

[0043] S12: At a set cycle rate C and a set temperature T, discharge the lithium-ion battery until the state of charge of the battery reaches 0% SOC;

[0044] S13: Perform charge and discharge cycling for more than N weeks, and obtain the dynamic charge and discharge curve and charge and discharge data through the charge and discharge equipment.

[0045] Among them, N can be selected according to the actual situation. After the equipment collects the data, the dynamic charge and discharge curve can be fitted through the data. The abscissa of the curve is the capacity (unit: Ah), and the ordinate is the voltage (unit: V). Vmin and Vmax can be directly obtained from the dynamic charge and discharge curve and charge and discharge data.

[0046] Perform full-SOC charge and discharge cycling on the lithium-ion battery through steps S11 to S13 to obtain the dynamic charge and discharge curve, providing the curve data basis for subsequent interval charge and discharge cycling.

[0047] S2: According to the dynamic charge and discharge curve, obtain the corresponding voltage V1 when discharging to A% SOC and the corresponding voltage V2 when charging to B% SOC under the A%-B% SOC interval cycling, and obtain the charging cut-off current A1 according to the charge and discharge data;

[0048] The values of A and B can be set from 1 to 100 according to actual needs.

[0049] S3: Compare V2 with Vmax. If V2 < Vmax, enter step S4; if V2 = Vmax, enter step S5;

[0050] A%-B% is the numerical space set according to the desired SOC interval.

[0051] S4: Set the cycle ratio C and perform cycle testing between V1 and V2;

[0052] Step S3 is specifically S41 to S42:

[0053] S41: Constant voltage and constant current charge to voltage V2 at the set temperature T and set cycle ratio C, and set aside for the set time t1;

[0054] S42: Constant current discharge to voltage V1 at the set cycle ratio C, and perform charge and discharge cycling.

[0055] Through steps S41 to S42, the lithium-ion battery is charged and discharged under constant voltage, meeting the possibility of voltage cut-off at different ratios, and improving the test efficiency.

[0056] S5: Set the cycle ratio C, discharge to the lower limit voltage V1, charge to the upper limit voltage V2, and charge at a constant voltage until the cut-off current A1.

[0057] Step S5 is specifically S51 to S53:

[0058] S51: Obtain the corresponding charging cut-off current A1 when charging to B% SOC under cycling in the A%-B% SOC interval according to the dynamic charge-discharge curve;

[0059] S52: Constant voltage charge to voltage V2 and then constant current charge to charging cut-off current A1 at a set temperature T and a set cycle rate C, and set aside for a set time t2;

[0060] Perform constant voltage charging on the lithium-ion battery and then constant current charging.

[0061] S53: Constant current discharge to voltage V1 at a set cycle rate C, and cycle the charge and discharge.

[0062] By steps S51 to S53, the lithium-ion battery is charged and discharged under constant voltage and constant current, meeting the possibility of voltage cut-off at different rates, and improving the test efficiency.

[0063] The charge and discharge in the present invention are based on the available capacity of the lithium-ion battery at a specific rate, avoiding the polarization problem caused by high rates when determining charge-discharge parameters based on the rated capacity of the lithium-ion battery, meeting the charge-discharge performance of the lithium-ion battery, and improving the accuracy of the cycle test of the lithium-ion battery.

[0064] According to the voltage cut-off of the set cycle rate C, the capacity test every once in a while at capacity cut-off is avoided, the test is simple and feasible, and the test cycle is shortened; according to the cut-off voltage corresponding to different set cycle rates C, the constant voltage or constant voltage and constant current method is used as the cut-off condition for charging stop, meeting the possibility of voltage cut-off at different rates, and improving the test efficiency.

[0065] Example 1:

[0066] S100: Cycle the battery at normal temperature 3C / 3C (30%-80% SOC), the charging cut-off voltage is 4.2, the cut-off current is 0.05C, the discharge cut-off voltage is 3.0V, the charge-discharge interval is 30 min, and cycle 5 weeks;

[0067] S200: According to the dynamic charge-discharge curve of 3C / 3C, as Figure 2 shown, find that the voltage corresponding to discharging 30% SOC is 3.55V, and the cut-off voltage corresponding to 80% SOC is 3.99V;

[0068] S300: Judge 3.99V < 4.2V according to the cut-off voltage 3.99V corresponding to 80% SOC, and perform cycle tests between 3.55V - 3.99V at normal temperature, that is, charge 3C / 3C to 3.99v, set aside for 30 min, and then discharge 3C / 3C to 3.55v; cycle the above steps.

[0069] Example 2

[0070] S001: Perform cycling on the battery at room temperature of 20°C / 20°C (30% - 90% SOC), with a charging cut-off voltage of 4.2V, a cut-off current of 0.05C, a discharging cut-off voltage of 3.0V, a 30-minute interval between charge and discharge, and cycle for 5 weeks.

[0071] S002: According to the dynamic charge-discharge curve at room temperature of 20°C / 20°C, as Figure 3 shown, find that the voltage corresponding to 30% SOC during discharge is 3.43V, and the cut-off voltage corresponding to 90% SOC is 4.2V.

[0072] S003: Based on the cut-off voltage of 4.2V corresponding to 90% SOC, when reaching the upper limit cut-off voltage, find that the cut-off current corresponding to 90% SOC is 40A, and conduct a cycling test at room temperature between 3.43V - 4.2V, that is, charge at 20°C / 20°C to 4.2V, with a cut-off current of 40A, hold for 30 minutes, and then discharge at 20°C / 20°C to 3.43V; cycle the above steps.

[0073] Through the above two embodiments, it can be obtained that the charge and discharge of the present invention are based on the available capacity of the lithium-ion battery at a specific rate, improving the accuracy of the cycling test of the lithium-ion battery.

[0074] A high-rate cycling test system for lithium-ion batteries, characterized in that it includes a curve acquisition module, an interval cycling charge-discharge module, a constant voltage charge-discharge module, and a constant voltage and constant current charge-discharge module;

[0075] The curve acquisition module is used to perform 0% - 100% SOC charge-discharge cycling on the lithium-ion battery for N weeks at a set cycling rate C and a set temperature T, and obtain the dynamic charge-discharge curve and charge-discharge data, where the charging cut-off voltage is Vmin and the discharging cut-off voltage is Vmax;

[0076] The interval cycling charge-discharge module is used to obtain the voltage V1 corresponding to discharging to A% SOC and the voltage V2 corresponding to charging to B% SOC during cycling in the A% - B% SOC interval according to the dynamic charge-discharge curve, obtain the charging cut-off current A1 according to the charge-discharge data, if V2 < Vmax, then enter the constant voltage charge-discharge module, if V2 = Vmax, then enter the constant voltage and constant current charge-discharge module;

[0077] The constant voltage charge-discharge module is used to perform a cycling test between V1 - V2 at a set cycling rate C;

[0078] The constant voltage and constant current charge-discharge module is used to perform a cycling test between V1 - V2 at a set cycling rate C and a charging cut-off current A1.

[0079] In this embodiment, the constant-voltage charge and discharge module includes a constant-voltage charging unit and a first constant-voltage discharging unit;

[0080] The constant-voltage charging unit is used to charge at a constant voltage to voltage V2 at a set temperature T and a set cycle rate C, and then hold for a set time t1;

[0081] The first constant-voltage discharging unit is used to discharge to voltage V1 at a set cycle rate C to perform charge and discharge cycling.

[0082] In this embodiment, the constant-voltage and constant-current charge and discharge module includes a cut-off current acquisition unit, a constant-voltage and constant-current charging unit, and a second constant-voltage discharging unit;

[0083] The cut-off current acquisition unit is used to obtain the corresponding cut-off current A1 when charging to B% SOC under cycling in the A%-B% SOC interval according to the dynamic charge and discharge curve;

[0084] The constant-voltage and constant-current charging unit is used to charge at a constant voltage to voltage V2 at a set temperature T and a set cycle rate C, and then charge at a constant current to the charging cut-off current A1, and then hold for a set time t2;

[0085] The second constant-voltage discharging unit is used to discharge to voltage V1 at a set cycle rate C to perform charge and discharge cycling.

[0086] As mentioned above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A high-rate cycling test method for lithium-ion batteries, comprising: Under a set cycling rate C and a set temperature T, performing 0%-100% SOC charge and discharge cycling on the lithium-ion battery for N weeks to obtain dynamic charge and discharge curves and charge and discharge data, where the charge cut-off voltage is Vmax and the discharge cut-off voltage is Vmin; According to the dynamic charge and discharge curves and charge and discharge data, obtain the voltage V1 corresponding to discharging to A% SOC and the voltage V2 corresponding to charging to B% SOC during cycling in the A%-B% SOC interval, and obtain the charge cut-off current A1 according to the charge and discharge data; If V2 < Vmax, perform cycling tests between V1 and V2 at the set cycling rate C; If V2 = Vmax, according to the dynamic charge and discharge curve, obtain the cut-off current A1 corresponding to charging to B% SOC during cycling in the A%-B% SOC interval; at the set temperature T and the set cycling rate C, perform constant voltage charging to voltage V2 and then constant current charging to the charge cut-off current A1, and set aside for a set time t2; discharge to voltage V1 at the set cycling rate C, and cycle the charge and discharge.

2. The high-rate cycling test method for lithium-ion batteries according to claim 1, characterized in that, Performing cycling tests between V1 and V2 at the set cycling rate C specifically includes: At the set temperature T and the set cycling rate C, perform constant voltage charging to voltage V2 and set aside for a set time t1; Discharge to voltage V1 at the set cycling rate C, and cycle the charge and discharge.

3. The high-rate cycle test method for lithium-ion batteries according to claim 1, wherein The dynamic charge and discharge curve is obtained by a charge and discharge device.

4. The high-rate cycle test method for lithium-ion batteries according to claim 1, characterized in that During the 0%-100% SOC charge and discharge cycling of the lithium-ion battery for N weeks, specifically includes: At the set cycling rate C and the set temperature T, charge the lithium-ion battery until the state of charge of the battery reaches 100% SOC and then stop charging; At the set cycling rate C and the set temperature T, discharge the lithium-ion battery until the state of charge of the battery reaches 0% SOC; Perform charge and discharge cycling for more than N weeks to obtain a dynamic charge and discharge curve.

5. A high-rate cycling test system for lithium-ion batteries, characterized in that, It includes a curve acquisition module, an interval cycling charge and discharge module, a constant voltage charge and discharge module, and a constant voltage and constant current charge and discharge module; The curve acquisition module is used to perform 0%-100% SOC charge and discharge cycling on the lithium-ion battery for N weeks at the set cycling rate C and the set temperature T to obtain dynamic charge and discharge curves and charge and discharge data, where the charge cut-off voltage is Vmax and the discharge cut-off voltage is Vmin; The interval cycling charge and discharge module is used to obtain the voltage V1 corresponding to discharging to A% SOC and the voltage V2 corresponding to charging to B% SOC during cycling in the A%-B% SOC interval according to the dynamic charge and discharge curves and charge and discharge data, obtain the charge cut-off current A1 according to the charge and discharge data, if V2 < Vmax, then enter the constant voltage charge and discharge module, if V2 = Vmax, then enter the constant voltage and constant current charge and discharge module; The constant voltage charge and discharge module is used to perform cycling tests between V1 and V2 at the set cycling rate C; The constant voltage and constant current charge and discharge module is used to discharge to the lower limit voltage V1 and charge to the upper limit voltage V2 at the set cycling rate C, and charge at a constant voltage to the cut-off current A1; The constant voltage and constant current charge and discharge module includes a cut-off current acquisition unit, a constant voltage and constant current charging unit, and a second constant voltage discharge unit; The cut-off current acquisition unit is used to obtain the corresponding charging cut-off current A1 when charging to B% SOC under the cycle in the A%-B% SOC interval according to the dynamic charge and discharge curve; The constant voltage and constant current charging unit is used to perform constant voltage charging to voltage V2 and then constant current charging to the charging cut-off current A1 at the set temperature T and the set cycle rate C, and then hold for the set time t2; The second constant voltage discharge unit is used to discharge to voltage V1 at the set cycle rate C to perform charge and discharge cycling.

6. The high-rate cycle test system for lithium-ion batteries according to claim 5, characterized in that The constant voltage charge and discharge module includes a constant voltage charging unit and a first constant voltage discharge unit; The constant voltage charging unit is used to perform constant voltage charging to voltage V2 at the set temperature T and the set cycle rate C, and then hold for the set time t1; The first constant voltage discharge unit is used to discharge to voltage V1 at the set cycle rate C to perform charge and discharge cycling.

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