Charging and discharging method of lithium ion battery
By employing a stepped charge-discharge rate method in lithium-ion batteries, combined with material ratio and cycle rate calculations for pure materials, the problem of poor cycle performance in the lithium iron phosphate and ternary cathode material blending system was solved, thereby improving the cycle performance and lifespan of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NIO TECH ANHUI CO LTD
- Filing Date
- 2024-10-31
- Publication Date
- 2026-05-01
AI Technical Summary
The existing lithium-ion battery system that blends lithium iron phosphate with ternary cathode materials has poor cycle performance.
By adopting a stepped charge-discharge rate method, the charge-discharge process of lithium-ion batteries is controlled in different voltage ranges to avoid high-rate charge-discharge of ternary cathode materials in the high SOC range. The charge-discharge rate is calculated by combining the design capacity contribution ratio of lithium iron phosphate and ternary cathode materials and the cycle rate of pure materials to ensure that the ternary cathode materials do not suffer structural loss due to high-rate charge-discharge.
It improves the cycle performance of lithium-ion batteries, extends battery life, and protects the structure and polarization capacity of ternary cathode materials.
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Abstract
Description
Lithium-ion battery charging and discharging methods Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and specifically provides a method for charging and discharging a lithium-ion battery. Background Technology
[0002] Lithium-ion batteries are characterized by their light weight, low self-discharge rate, high energy density, and high safety. They are widely used in consumer electronics and mobile digital fields, and with the booming development of new energy vehicles, their application in electric vehicles is becoming increasingly widespread.
[0003] Among the cathode materials for lithium-ion batteries, nickel-cobalt-manganese / nickel-cobalt-aluminum ternary cathode materials and lithium iron phosphate (LFP) are two mainstream technologies. LFP cathode materials have good cycle stability and high thermal stability, but low specific capacity. Ternary cathode materials have higher specific capacity, but their cycle stability and thermal stability are worse than LFP. As the nickel content of ternary cathode materials increases, their safety performance deteriorates further. Blending LFP with ternary cathode materials balances energy density, cycle performance, and thermal safety, leading to the increasingly widespread application of LFP-blended ternary cathode composites. However, due to the inconsistency in the voltage platform and operating voltage range of the two materials, the cycle performance of the blended lithium-ion battery is poor, necessitating improvements in the cycle performance of the blended system.
[0004] Accordingly, a new technical solution is needed in this field to solve the above-mentioned technical problems. Summary of the Invention
[0005] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problem of poor cycle performance of existing lithium-ion batteries with lithium iron phosphate and ternary cathode material blending systems.
[0006] This invention provides a charging and discharging method for a lithium-ion battery. The positive electrode of the lithium-ion battery includes lithium iron phosphate and a ternary cathode material. The charging and discharging method includes: charging the lithium-ion battery according to a first constant current charging mode until the voltage reaches V1, then switching to a first constant voltage charging mode, wherein the charging rate in the first constant current charging mode is a first charging rate C1; continuing to charge according to the first constant voltage charging mode until the charging rate decreases to a second charging rate C2, then switching to a second constant current charging mode; and continuing to charge according to the second constant current charging mode until the voltage reaches V1. max Then it switches to the second constant voltage charging mode, where the charging rate is the second charging rate C2; charging continues in the second constant voltage charging mode until the charging rate decreases to the cutoff charging rate C. min Charging stopped; wherein the first charging rate C1 is greater than the second charging rate C2, and V1 is less than V max; and / or, the lithium-ion battery discharges according to a first constant current discharge mode until the voltage drops to V2, then switches to a second constant current discharge mode, wherein the discharge rate in the first constant current discharge mode is a first discharge rate D1, the discharge rate in the second constant current discharge mode is a second discharge rate D2, and the first discharge rate D1 is less than the second discharge rate D2.
[0007] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, the design capacity contribution ratio of lithium iron phosphate to ternary cathode material in the lithium-ion battery is lithium iron phosphate: ternary cathode material = N:1, and the first charging rate C1 is calculated by the following formula: C1 = N / N 标1 ÷(N+1)+C 标2 ÷(N+1), where C 标1 C represents the cycle charge rate of a pure lithium iron phosphate lithium-ion battery. 标2 This refers to the cycle charge rate of a lithium-ion battery using pure ternary cathode material.
[0008] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, the design capacity contribution ratio of lithium iron phosphate to ternary cathode material in the lithium-ion battery is lithium iron phosphate: ternary cathode material = N:1, and the second charging rate C2 is calculated by the following formula: C2 = C 标2 ÷(N+1), where C 标2 This refers to the cycle charge rate of a lithium-ion battery using pure ternary cathode material.
[0009] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, the design capacity contribution ratio of lithium iron phosphate to ternary cathode material in the lithium-ion battery is lithium iron phosphate: ternary cathode material = N:1, and the first discharge rate D1 is calculated by the following formula: D1 = D 标2 ÷(N+1), where D 标2 This refers to the cycle discharge rate of a lithium-ion battery using pure ternary cathode material.
[0010] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, the design capacity contribution ratio of lithium iron phosphate to ternary cathode material in the lithium-ion battery is lithium iron phosphate: ternary cathode material = N:1, and the second discharge rate D2 is calculated by the following formula: D2 = D 标1 ÷(N+1)+D 标2 ÷(N+1), where D 标1 D represents the cycle discharge rate of a pure lithium iron phosphate lithium-ion battery. 标2 This refers to the cycle discharge rate of a lithium-ion battery using pure ternary cathode material.
[0011] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, N∈(0,15).
[0012] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, the voltage in the first constant-voltage charging mode is V1; and / or, the voltage in the second constant-voltage charging mode is V. max .
[0013] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, V1∈[3.4V, 3.6V].
[0014] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, V2∈[3.4V, 3.6V].
[0015] In the preferred embodiment of the above-mentioned charging and discharging method for lithium-ion batteries, the cutoff charging rate C min It is 0.05C.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0017] (1) During the charging process, constant current charging is performed at a larger first charging rate C1 in the voltage range below V1. After the voltage reaches V1, the charging mode is switched to constant voltage charging. The actual charging rate is gradually reduced and transitioned to the second charging rate C2. Then, constant current charging is performed at a smaller second charging rate C2. max Then, the charging mode was switched back to constant voltage charging mode, and the actual charging rate was gradually reduced. When the actual charging rate was reduced to the cutoff charging rate, the charging was completed. During the discharge process, the voltage range above V2 was constant current discharge using a smaller first discharge rate D1. After the voltage dropped to V2, a larger second discharge rate D2 was used for constant current discharge until the discharge was completed. This charge-discharge cycle method, by charging and discharging with a stepped charge-discharge rate, avoids the high-rate charge-discharge of ternary cathode materials in the high SOC range. This ensures that the range in which the ternary cathode material exerts its capacity alone will not suffer irreversible structural loss and polarization capacity loss due to high-rate charge-discharge, thereby improving the cycle performance of the mixed lithium-ion battery.
[0018] (2) Based on the design capacity contribution ratio of lithium iron phosphate and ternary cathode materials and the cycle charging rate C of pure lithium iron phosphate lithium-ion batteries 标1 The cycle charge rate C of lithium-ion batteries with pure ternary cathode materials 标2The specific values of the first charging rate C1 and the second charging rate C2 are calculated, so that the first charging rate C1 and the second charging rate C2 are more in line with the current lithium-ion battery materials and composition ratios, which can better protect the ternary cathode material and thus better improve the cycle performance of the lithium-ion battery.
[0019] (3) Based on the design capacity contribution ratio of lithium iron phosphate and ternary cathode materials and the cycle discharge rate D of pure lithium iron phosphate lithium-ion batteries 标1 The cycle discharge rate D of lithium-ion batteries with pure ternary cathode materials 标2 The specific values of the first discharge rate D1 and the second discharge rate D2 are calculated, so that the first discharge rate D1 and the second discharge rate D2 are more in line with the current lithium-ion battery materials and composition ratios, which can better protect the ternary cathode material and thus better improve the cycle performance of lithium-ion batteries. Detailed Implementation
[0020] Preferred embodiments of the present invention will now be described. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.
[0021] It should be noted that in the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0022] The existing lithium-ion batteries with lithium iron phosphate and ternary cathode material blending systems have poor cycle performance, as pointed out in the background section.
[0023] This application provides a charging and discharging method for lithium-ion batteries. By controlling the charging and discharging rate during different voltage periods, it effectively avoids high-rate charging and discharging of ternary cathode materials in the high SOC range, thereby ensuring that the ternary cathode materials will not suffer irreversible structural loss and polarization capacity loss due to high-rate charging and discharging, thus effectively improving the cycle performance of the mixed system lithium-ion battery.
[0024] Specifically, the lithium-ion battery of this application is a lithium-ion battery in which the positive electrode simultaneously includes lithium iron phosphate and ternary positive electrode materials.
[0025] Specifically, the charging and discharging method for the lithium-ion battery in this application includes a charging method and a discharging method.
[0026] Its charging method includes steps S1 to S4:
[0027] S1: The lithium-ion battery is charged in the first constant current charging mode until the voltage reaches V1, then it switches to the first constant voltage charging mode. The charging rate in the first constant current charging mode is the first charging rate C1.
[0028] S2: Continue charging in the first constant voltage charging mode until the charging rate decreases to the second charging rate C2, then switch to the second constant current charging mode.
[0029] S3: Continue charging according to the second constant current charging mode until the voltage reaches V. max It then switches to the second constant voltage charging mode, and the charging rate in the second constant current charging mode is the second charging rate C2.
[0030] S4: Continue charging according to the second constant voltage charging mode until the charging rate decreases to the cutoff charging rate C. min Stop charging.
[0031] Wherein, the first charging rate C1 is greater than the second charging rate C2, and V1 is less than V max .
[0032] By employing the above charging method, during the charging process, a larger first charging rate C1 is used for constant current charging in the voltage range below V1. Then, after the voltage reaches V1, the charging mode is switched to constant voltage charging, gradually reducing the actual charging rate and transitioning to a second charging rate C2. Finally, a smaller second charging rate C2 is used for constant current charging, and the charging continues until the voltage reaches V1. max Then, the charging mode is switched back to constant voltage charging mode, and the actual charging rate is gradually reduced. When the actual charging rate is reduced to the cutoff charging rate, the charging is completed. Charging in this step-by-step charging rate method can avoid high-rate charging of ternary cathode materials in the high SOC range, thereby ensuring that the ternary cathode materials will not suffer irreversible structural loss and polarization capacity loss due to high-rate charging and discharging. This improves the cycle performance of the mixed system lithium-ion battery and extends the service life of the lithium-ion battery.
[0033] It should be noted that this application does not impose any restrictions on the specific values of the first charging rate C1 and the second charging rate C2. In practical applications, those skilled in the art can set the specific values of the first charging rate C1 and the second charging rate C2 according to actual needs. Adjustments and changes to the specific values of the first charging rate C1 and the second charging rate C2 do not deviate from the basic principles of this application and should be limited to the protection scope of this application.
[0034] In some embodiments, in a lithium-ion battery, the design capacity contribution ratio of lithium iron phosphate to ternary cathode material is lithium iron phosphate : ternary cathode material = N : 1.
[0035] In step S1, the first charging rate C1 is calculated using the following formula: C1 = NC 标1 ÷(N+1)+C 标2÷(N+1), in steps S2 and S3, the second charging rate C2 is calculated using the following formula: C2=C 标2 ÷(N+1), where C 标1 C represents the cycle charge rate of a pure lithium iron phosphate lithium-ion battery. 标2 This refers to the cycle charge rate of a lithium-ion battery using pure ternary cathode material.
[0036] In this application, based on the design capacity contribution ratio of lithium iron phosphate and ternary cathode materials and the cycle charge rate C of pure lithium iron phosphate lithium-ion batteries... 标1 The cycle charge rate C of lithium-ion batteries with pure ternary cathode materials 标2 The specific values of the first charging rate C1 and the second charging rate C2 are calculated, so that the first charging rate C1 and the second charging rate C2 are more in line with the current use of lithium-ion batteries. In the voltage range where the ternary cathode material exerts its capacity alone, the charging rate of the ternary cathode material is proportionally converted into the mixed system, which ensures that the ternary material will not suffer irreversible structural loss and polarization capacity loss due to high charging rate. This can better protect the ternary cathode material and thus better improve the cycle performance of lithium-ion batteries.
[0037] In some embodiments, N∈(0, 15).
[0038] In some embodiments, the voltage in the first constant voltage charging mode is V1.
[0039] In some embodiments, V1∈[3.4V, 3.6V].
[0040] In some embodiments, the voltage in the second constant voltage charging mode is V. max Among them, V max This is the upper limit of the design voltage for lithium-ion batteries; this value is a known value for lithium-ion batteries.
[0041] In some embodiments, the cutoff charging rate C min It is 0.05C.
[0042] Specifically, the discharge method of the lithium-ion battery in this application includes:
[0043] The lithium-ion battery discharges according to the first constant current discharge mode until the voltage drops to V2, then switches to the second constant current discharge mode.
[0044] In the first constant current discharge mode, the discharge rate is the first discharge rate D1, and in the second constant current discharge mode, the discharge rate is the second discharge rate D2. The first discharge rate D1 is less than the second discharge rate D2.
[0045] The lithium-ion battery discharge method of this application uses a smaller first discharge rate D1 for constant current discharge in the voltage range above V2, and then a larger second discharge rate D2 for constant current discharge after the voltage drops to V2, until the discharge ends. This discharge method, through a stepped discharge rate, avoids high-rate discharge of ternary cathode materials in the high SOC range, thereby ensuring that the ternary cathode materials will not suffer irreversible structural loss and polarization capacity loss due to high-rate discharge, thus improving the cycle performance of the mixed system lithium-ion battery and extending the service life of the lithium-ion battery.
[0046] It should be noted that this application does not impose any restrictions on the specific values of the first discharge rate D1 and the second discharge rate D2. In practical applications, those skilled in the art can set the specific values of the first discharge rate D1 and the second discharge rate D2 according to actual needs. Adjustments and changes to the specific values of the first discharge rate D1 and the second discharge rate D2 do not deviate from the basic principles of this application and should be limited to the protection scope of this application.
[0047] In some embodiments, in a lithium-ion battery, the design capacity contribution ratio of lithium iron phosphate to ternary cathode material is lithium iron phosphate : ternary cathode material = N : 1.
[0048] The first discharge rate D1 is calculated using the following formula: D1 = D 标2 The second discharge rate D2 is calculated using the following formula: D2 = D (N+1) / (N+1). 标1 ÷(N+1)+D 标2 ÷(N+1), D 标1 D represents the cycle discharge rate of a pure lithium iron phosphate lithium-ion battery. 标2 This refers to the cycle discharge rate of a lithium-ion battery using pure ternary cathode material.
[0049] In this application, based on the design capacity contribution ratio of lithium iron phosphate and ternary cathode materials and the cycle discharge rate D of pure lithium iron phosphate lithium-ion batteries... 标1 The cycle discharge rate D of lithium-ion batteries with pure ternary cathode materials 标2 The specific values of the first discharge rate D1 and the second discharge rate D2 are calculated, so that the first discharge rate D1 and the second discharge rate D2 are more in line with the current use of lithium-ion batteries. In the voltage range where the ternary cathode material exerts its capacity alone, the discharge rate of the ternary cathode material is proportionally converted into the blended system, which ensures that the ternary material will not suffer irreversible structural loss and polarization capacity loss due to high discharge rate, thus better protecting the ternary cathode material and improving the cycle performance of lithium-ion batteries.
[0050] In some embodiments, N∈(0, 15).
[0051] In some embodiments, V2∈[3.4V, 3.6V].
[0052] The charging and discharging method of the lithium-ion battery of this application will be described in detail below through a specific embodiment of the lithium-ion battery.
[0053] Example
[0054] The cell design information of the lithium-ion battery in this embodiment is shown in Table 1.
[0055] Table 1 Cell parameters of the embodiment
[0056] Specifically, the positive electrode active material, conductive agent acetylene black, multi-walled carbon nanotubes, and binder are dissolved in N-methylpyrrolidone (NMP) at a weight ratio of 95:2:1:2, and thoroughly homogenized to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto an aluminum (Al) foil positive electrode current collector, followed by baking, cold pressing, and slitting to obtain the positive electrode sheet. The positive electrode active materials are LiFePO4 and LiNi. 0.8 Co 0.1 Mn 0.1 O2, including LiFePO4 and LiNi 0.8 Co 0.1 Mn 0.1 The designed capacity contribution ratio for O2 is lithium iron phosphate: ternary cathode material = 4:1, with polyvinylidene fluoride (PVDF) as the binder. It should be noted that the designed capacity contribution ratio can be achieved through the mixing of LiFePO4 and LiNi. 0.8 Co 0.1 Mn 0.1 The mass percentage of O2 in the positive electrode active material and their respective specific capacities were calculated. After the formulation of the positive electrode slurry was determined, the LiFePO4 and LiNi... 0.8 Co 0.1 Mn 0.1 The design capacity contribution ratio of O2 has also been determined.
[0057] The negative electrode active material, artificial graphite, conductive agent, acetylene black, polyacrylic acid (PAA), binder, styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are dissolved in deionized water at a weight ratio of 95:0.5:1.5:2:1 and thoroughly mixed to obtain a negative electrode slurry. The negative electrode slurry is then uniformly coated onto a copper (Cu) foil negative electrode current collector. After baking, cold pressing, and die cutting, a negative electrode sheet is obtained.
[0058] The positive and negative electrode sheets and the separator are stacked to form a bare cell. The bare cell is then packaged, baked, injected with electrolyte, left to stand, formed, aged, and capacity tested to obtain the finished cell. The injected electrolyte has a mass percentage of EC:PC:EMC = 4:2:1, a lithium salt content of 12.5%, and a lithium salt concentration of 1.2 mol / L.
[0059] The cell formation process is shown in Table 2, and the cell capacity testing process is shown in Table 3.
[0060] Table 2. Cell Formation Process Data Table
[0061] Table 3. Battery Cell Capacity Testing Process Data Table
[0062] The batteries that have been tested and rated are first calibrated at a 1 / 3C rate within the 0-100% SOC range, i.e., charged at a 1 / 3C constant current to 4.25V, constant voltage to 0.05C, left to stand for 10 minutes, and then discharged at a 1 / 3C constant current to 2.5V.
[0063] The battery cells were divided into two groups, A and B, and then 25°C cycle tests were conducted according to the cycle method of groups A and B respectively. The charging and discharging methods during the cycle are shown in Table 4. Group A is the experimental group and group B is the control group.
[0064] Table 4. Parameters for Groups A and B of Cyclic Charge-Discharge Methods
[0065] Specifically, the cyclic charging rate C when the cathode is pure LiFePO4 标1 The cycle discharge rate D when the cathode is pure LiFePO4 at 1C (charging) 标1 1C (discharge), positive electrode pure LiNi 0.8 Co 0.1 Mn 0.1 O2 cycling rate C 标2 For 1C (charging), the positive electrode is pure LiNi. 0.8 Co 0.1 Mn 0.1 O2 cyclic discharge rate D 标2 The discharge rate is set to 1C, and both V1 and V2 are chosen to be 3.6V. Therefore, the first charge rate C1 is calculated to be 1C, the second charge rate C2 to be 0.2C, the first discharge rate D1 to be 0.2C, and the second discharge rate D2 to be 1C. In group B, both the charge rate and the discharge rate are 1C.
[0066] During each charge-discharge cycle, the resting time between charge and discharge was 30 minutes. The cycle was performed at 25°C for 800 cycles. The capacity retention rate at 800 cycles for each group was calculated using the following formula: Capacity retention rate at 800 cycles = Discharge capacity at 800 cycles ÷ Discharge capacity at 1st cycle × 100%. The test results are shown in Table 5.
[0067] Table 5. Capacity retention rate of Groups A and B after 800 laps
[0068] As shown in Table 5, the cycle performance of Group A at 25℃ is significantly better than that of Group B. Therefore, the charge-discharge method of this application can effectively improve the cycle performance of lithium-ion batteries in the mixed system of lithium iron phosphate and ternary cathode materials, thereby maximizing the lifespan of lithium-ion batteries.
[0069] In the cathode blending system, lithium iron phosphate and ternary NCM811 have different capacity utilization ranges. When the voltage reaches above 3.6V, lithium iron phosphate contributes almost no capacity. At this point, in the battery design of this embodiment, the capacity of ternary NCM811 accounts for 20% of the cathode capacity. If a 1C charging rate is used, it is equivalent to a 1C / 20% = 5C rate applied to the ternary NCM811. Under high rate conditions, irreversible structural damage and polarization capacity loss of the cathode NCM material will occur, and the same will happen during discharge, ultimately leading to a sharp deterioration in cycle performance. Therefore, by using the charge and discharge method of this application for cyclic charging and discharging, the cycle stability of the cathode lithium iron phosphate blended with ternary cathode material can be significantly improved without sacrificing the charging speed, thereby extending the battery life.
[0070] The technical solution of the present invention has been described in conjunction with preferred embodiments. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions resulting from these changes or substitutions will all fall within the scope of protection of the present invention.
Claims
1. A method for charging and discharging a lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery includes lithium iron phosphate and ternary cathode materials. The charging and discharging method includes: charging the lithium-ion battery according to a first constant current charging mode until the voltage reaches V1, then switching to a first constant voltage charging mode, wherein the charging rate in the first constant current charging mode is a first charging rate C1; continuing to charge according to the first constant voltage charging mode until the charging rate decreases to a second charging rate C2, then switching to a second constant current charging mode; continuing to charge according to the second constant current charging mode until the voltage reaches V1. max Then it switches to the second constant voltage charging mode, where the charging rate is the second charging rate C2; charging continues in the second constant voltage charging mode until the charging rate decreases to the cutoff charging rate C. min Charging stopped; wherein the first charging rate C1 is greater than the second charging rate C2, and V1 is less than V max ; and / or, the lithium-ion battery discharges according to a first constant current discharge mode until the voltage drops to V2, then switches to a second constant current discharge mode, wherein the discharge rate in the first constant current discharge mode is a first discharge rate D1, the discharge rate in the second constant current discharge mode is a second discharge rate D2, and the first discharge rate D1 is less than the second discharge rate D2.
2. The charging and discharging method for a lithium-ion battery according to claim 1, characterized in that, In the lithium-ion battery, the design capacity contribution ratio of the lithium iron phosphate and the ternary cathode material is lithium iron phosphate: ternary cathode material = N:1, and the first charging rate C1 is calculated by the following formula: C1 = N / N 标1 ÷(N+1)+C 标2 ÷(N+1), where C 标1 C represents the cycle charge rate of a pure lithium iron phosphate lithium-ion battery. 标2 This refers to the cycle charge rate of a lithium-ion battery using pure ternary cathode material.
3. The charging and discharging method for a lithium-ion battery according to claim 1, characterized in that, In the lithium-ion battery, the design capacity contribution ratio of the lithium iron phosphate and the ternary cathode material is lithium iron phosphate: ternary cathode material = N:1, and the second charging rate C2 is calculated by the following formula: C2 = C 标2 ÷(N+1), where C 标2 This refers to the cycle charge rate of a lithium-ion battery using pure ternary cathode material.
4. The charging and discharging method for a lithium-ion battery according to claim 1, characterized in that, In the lithium-ion battery, the design capacity contribution ratio of the lithium iron phosphate and the ternary cathode material is lithium iron phosphate: ternary cathode material = N:1, and the first discharge rate D1 is calculated by the following formula: D1 = D 标2 ÷(N+1), where D 标2 This refers to the cycle discharge rate of a lithium-ion battery using pure ternary cathode material.
5. The charging and discharging method for a lithium-ion battery according to claim 1, characterized in that, In the lithium-ion battery, the design capacity contribution ratio of the lithium iron phosphate and the ternary cathode material is lithium iron phosphate: ternary cathode material = N:1, and the second discharge rate D2 is calculated by the following formula: D2 = D 标1 ÷(N+1)+D 标2 ÷(N+1), where D 标1 D represents the cycle discharge rate of a pure lithium iron phosphate lithium-ion battery. 标2 This refers to the cycle discharge rate of a lithium-ion battery using pure ternary cathode material.
6. The charging and discharging method for a lithium-ion battery according to any one of claims 2 to 5, characterized in that, N∈(0，15]。 7. The charging and discharging method for a lithium-ion battery according to claim 1, characterized in that, The voltage in the first constant voltage charging mode is V1; and / or, the voltage in the second constant voltage charging mode is V. max .
8. The charging and discharging method for a lithium-ion battery according to claim 1 or 7, characterized in that, V1∈[3.4V, 3.6V].
9. The charging and discharging method for a lithium-ion battery according to claim 1 or 7, characterized in that, V2∈[3.4V, 3.6V].
10. The charging and discharging method for a lithium-ion battery according to claim 1, characterized in that, The cutoff charging rate C min It is 0.05C.