A lithium-ion battery consistency evaluation method

Abstract

The invention discloses a lithium ion battery consistency evaluation method, comprising the following processing steps: step 1, designing a series of consistency alignment SOC points according to the use requirements of a battery pack, wherein the consistency alignment SOC points of the battery pack are designed to be 5%, 20%, 30% and 95% respectively; step 2, charging and discharging once in an air-conditioned environment at a temperature of T1 according to the designed rated rate of the battery cell, short-circuiting t at each consistency alignment point, and testing the maximum short-circuit current, where t is the short-circuit time; the method of the invention uses the maximum discharge current of three temperatures as the chemical reaction rate of the lithium battery under the condition, so as to facilitate statistics of the capacity, coulomb efficiency, energy efficiency and consistency alignment point activation energy of the battery cell, and performs cycle tests according to different discrete degree grouping of parameters, so as to obtain the cycle life retention rate after different discrete degree grouping, thereby overcoming the problem that the parameters are only measured when the battery cell performance is measured, and the source of the battery attenuation difference when the batteries are coordinated and work in series is not considered.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery consistency evaluation, and in particular to a lithium-ion battery consistency evaluation method. Background Art

[0002] Lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the movement of lithium ions between the positive electrode and the negative electrode to work. During the charge and discharge process, Li+ is embedded and de-embedded between the two electrodes: when charging, Li+ is de-embedded from the positive electrode and embedded in the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; when discharging, the opposite is true. Lithium batteries are divided into lithium batteries and lithium-ion batteries. Mobile phones and laptops use lithium-ion batteries, which are commonly known as lithium batteries. Batteries generally use materials containing lithium elements as electrodes and are the representative of modern high-performance batteries. Since its invention in 1992, lithium-ion batteries have rapidly penetrated into consumer electronics, new energy vehicles, aerospace, energy storage and other fields due to their high energy density, long cycle life and high single-cell voltage. In many applications, the voltage and capacity required by the battery will be much greater than the single-cell voltage of lithium-ion batteries, and a combination of many cells is required to meet the use requirements. Since battery materials and processes will affect the consistency of batteries, and the inconsistency of single cells will cause the overall characteristics of the battery pack to decline sharply and some batteries to be damaged faster, a good matching scheme can ensure the consistency of the matched cells and the battery products meet the designed life and reliability. The static parameters commonly used to evaluate the consistency of cells are voltage, capacity, internal resistance, self-discharge rate, and the dynamic parameters are discharge curve similarity. Due to the limitations of the testing process, the industry reality is usually to use static parameters as the basis for matching, that is, open circuit voltage, discharge capacity, AC internal resistance, and self-discharge rate for screening. Batteries matched in this way usually cannot adapt to complex working conditions and long life requirements.

[0003] Patent application 201910953321.6 developed this method, pre-matching the above four parameters, and then charging and discharging to obtain two DC internal resistances, which are sorted again using the two internal resistance differences, and then sorted three times using the relaxation voltage to include dynamic consistency.

[0004] The method disclosed in patent application 201910820621.7 uses several parameters including first formation efficiency, coulombic efficiency, energy efficiency, capacity, charge retention rate and AC internal resistance. The first formation efficiency, coulombic efficiency and energy efficiency are used to replace the open circuit voltage parameter to improve the consistency of the matching.

[0005] Patent application 201910237806.5 uses five parameters, namely discharge capacity, ohmic impedance, SEI film impedance, charge exchange impedance, and solid phase diffusion impedance, as evaluation criteria. It also uses other parameters to replace the open circuit voltage. Due to the maturity of the balancing technology, the difference in self-discharge rate is abandoned.

[0006] Patent application 201811075331.6 focuses on the role of the voltage-time curve in the formation process, and patent application 201910994554.0 focuses on the voltage difference between the 5% and 95% SOC points, which is used to improve the voltage difference at the end of charging and discharging.

[0007] Existing technologies for consistency assessment all measure parameters when single battery cells are performing, without considering the source of differences in battery attenuation when batteries are connected in series and working in coordination, which will affect the overall data of lithium-ion batteries and affect the assessment of lithium-ion batteries. Summary of the invention

[0008] The present invention provides a lithium-ion battery consistency evaluation method to solve the technical problem that the above-mentioned background technology only measures the parameters of battery single body performance, but does not consider the source of battery attenuation differences when the batteries are connected in series and work in coordination.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: a lithium-ion battery consistency evaluation method, comprising the following processing steps:

[0010] Step 1: Design a series of consistent SOC points according to the battery pack usage requirements, such as 5%, 20%, 50%, 80%, and 95%.

[0011] Step 2: Charge and discharge the battery cells once at the designed rated rate in an air-conditioned environment with a temperature of T1, such as 20°C. Short-circuit each consistency alignment point for t, such as 3 seconds, and test the maximum short-circuit current.

[0012] Step 3: Repeat the test in step 2 at room temperature T2, such as 25°C.

[0013] Step 4: Repeat the test in step 2 in a high temperature room at a temperature T3 such as 40°C.

[0014] Step 5: Use the maximum discharge current at the three temperatures as the chemical reaction rate of the lithium battery under the conditions, and use the graphical method to calculate the activation energy of each consistency calibration point.

[0015] Step 6: Count the capacity, coulombic efficiency, energy efficiency, and consistency-to-point activation energy of the battery cells.

[0016] Step 7: Perform cycle tests on the parameters with different discreteness combinations to obtain cycle life retention rates after different discreteness combinations.

[0017] Step 8: Use the relationship between the above parameter dispersion and cycle life retention rate as a lithium-ion battery consistency evaluation method.

[0018] Preferably, the lithium-ion battery for use in the extended-range vehicle is provided with three charging modes, namely, slow charging, fast charging and range extender charging.

[0019] Preferably, the battery pack adopts a single-string 400V 150Ah design, each group requires 111 cells, plus 5 maintenance cells, and the number of cells in each group is 116.

[0020] Preferably, the battery pack design consistency alignment points are four SOC points of 5%, 20%, 30% and 95%.

[0021] Preferably, each battery cell has a rated energy storage of 614Wh.

[0022] Preferably, the temperature set in step 2, step 3 and step 4 is 15°C-40°C.

[0023] Preferably, the battery pack adopts a 60kWh150Ah ternary battery pack.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the method of the present invention uses the maximum discharge current of three temperatures as the chemical reaction rate of the lithium battery under the conditions, and uses a graphical method to calculate the activation energy of each consistency calibration point, so as to facilitate the statistics of the capacity, coulomb efficiency, energy efficiency, and consistency calibration point activation energy of the battery cell, and performs cycle tests according to groups with different discreteness of parameters to obtain the cycle life retention rate after grouping with different discreteness, and uses the relationship between the above parameter discreteness and the cycle life retention rate as a lithium-ion battery consistency evaluation method, which includes evaluation parameters of energy management, power management, thermal management, and maintenance management, and can obtain the management parameters of the battery pack throughout its life cycle. The difference in activation energy can evaluate the kinetic difference in battery attenuation, which overcomes the problem that the parameters are all measured when the battery cell performance is measured, and the source of the battery attenuation difference when the batteries work in coordination when connected in series is not considered. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention measures activation energy by testing the reaction rate constant at different temperatures. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand and comprehend, the present invention is further described below in conjunction with specific implementation methods.

[0027] Embodiment 1, a lithium ion battery consistency evaluation method, comprising the following processing steps:

[0028] Step 1: Design a series of consistent SOC points according to the battery pack usage requirements, such as 5%, 20%, 50%, 80%, and 95%.

[0029] Step 2: Perform the first charge and discharge cycle in an air-conditioned 15°C room, short-circuit the SOC for 2 seconds at each consistency, and record the short-circuit current.

[0030] Step 3: Using the heat generated by the first discharge, perform a second charge and discharge cycle at an elevated temperature, short-circuit for 2 seconds at each consistency alignment SOC, and record the short-circuit current.

[0031] Step 4: Using the heat generated by the second discharge, perform a third charge and discharge cycle in an elevated temperature environment, short-circuit for 2 seconds at each consistency alignment SOC, and record the short-circuit current.

[0032] Step 5: Use the maximum discharge current at the three temperatures as the chemical reaction rate of the lithium battery under the conditions, and use the graphical method to calculate the activation energy of each consistency calibration point.

[0033] Step 6: Count the capacity, coulombic efficiency, energy efficiency, and consistency-to-point activation energy of the battery cells.

[0034] Step 7: Perform cycle tests on the parameters with different discreteness combinations to obtain cycle life retention rates after different discreteness combinations.

[0035] Step 8: Use the relationship between the above parameter dispersion and cycle life retention rate as a lithium-ion battery consistency evaluation method.

[0036] Preferably, the lithium-ion battery used for the extended-range vehicle is provided with three charging modes, namely, slow charging, fast charging and range extender charging.

[0037] Preferably, the battery pack adopts a single-string 400V 150Ah design, each group requires 111 cells, plus 5 maintenance cells, and the number of cells in each group is 116.

[0038] Preferably, the battery pack design consistency alignment points are four SOC points of 5%, 20%, 30% and 95%.

[0039] Preferably, each battery cell has a rated energy storage of 614Wh.

[0040] Preferably, the temperature set in step (2), step (3) and step (4) is 15°C.

[0041] Preferably, the battery pack adopts a 60kWh150Ah ternary battery pack.

[0042] Embodiment 2, a lithium ion battery consistency evaluation method, comprising the following processing steps:

[0043] Step 1: Design a series of consistent SOC points according to the battery pack usage requirements, such as 5%, 20%, 50%, 80%, and 95%.

[0044] Step 2: Perform the first charge and discharge cycle at room temperature (20°C), short-circuit the SOC for 2.5 seconds at each consistency, and record the short-circuit current.

[0045] Step 3: Using the heat generated by the first discharge, perform a second charge and discharge cycle at an elevated temperature, short-circuit for 2.5 seconds at each consistency alignment SOC, and record the short-circuit current.

[0046] Step 4: Using the heat generated by the second discharge, perform a third charge and discharge cycle in an elevated temperature environment, short-circuit for 2.5 seconds at each consistency alignment SOC, and record the short-circuit current.

[0047] Step 5: Use the maximum discharge current at the three temperatures as the chemical reaction rate of the lithium battery under the conditions, and use the graphical method to calculate the activation energy of each consistency calibration point.

[0048] Step 6: Count the capacity, coulombic efficiency, energy efficiency, and consistency-to-point activation energy of the battery cells.

[0049] Step 7: Perform cycle tests on the parameters with different discreteness combinations to obtain cycle life retention rates after different discreteness combinations.

[0050] Step 8: Use the relationship between the above parameter dispersion and cycle life retention rate as a lithium-ion battery consistency evaluation method.

[0051] Preferably, the lithium-ion battery used for the extended-range vehicle is provided with three charging modes, namely, slow charging, fast charging and range extender charging.

[0052] Preferably, the battery pack adopts a single-string 400V 150Ah design, each group requires 111 cells, plus 5 maintenance cells, and the number of cells in each group is 116.

[0053] Preferably, the battery pack design consistency alignment points are four SOC points of 5%, 20%, 30% and 95%.

[0054] Preferably, each battery cell has a rated energy storage of 614Wh.

[0055] Preferably, the temperature set in step (2), step (3) and step (4) is 15°C.

[0056] Preferably, the battery pack adopts a 60kWh150Ah ternary battery pack.

[0057] Embodiment 3, a lithium ion battery consistency evaluation method, comprising the following processing steps:

[0058] Step 1: Design a series of consistent SOC points according to the battery pack usage requirements, such as 5%, 20%, 50%, 80%, and 95%.

[0059] Step 2: Perform the first charge and discharge cycle in a room at 30°C, short-circuit the SOC for 3 seconds at each consistency, and record the short-circuit current.

[0060] Step 3: Using the heat generated by the first discharge, perform a second charge and discharge cycle at an elevated temperature, short-circuit for 3 seconds at each consistency alignment SOC, and record the short-circuit current.

[0061] Step 4: Using the heat generated by the second discharge, perform a third charge and discharge cycle in an elevated temperature environment, short-circuit for 3 seconds at each consistency alignment SOC, and record the short-circuit current.

[0062] Step 5: Use the maximum discharge current at the three temperatures as the chemical reaction rate of the lithium battery under the conditions, and use the graphical method to calculate the activation energy of each consistency calibration point.

[0063] Step 6: Count the capacity, coulombic efficiency, energy efficiency, and consistency-to-point activation energy of the battery cells.

[0064] Step 7: Perform cycle tests on the parameters with different discreteness combinations to obtain cycle life retention rates after different discreteness combinations.

[0065] Step 8: Use the relationship between the above parameter dispersion and cycle life retention rate as a lithium-ion battery consistency evaluation method.

[0066] Preferably, the lithium-ion battery used for the extended-range vehicle is provided with three charging modes, namely, slow charging, fast charging and range extender charging.

[0067] Preferably, the battery pack adopts a single-string 400V 150Ah design, each group requires 111 cells, plus 5 maintenance cells, and the number of cells in each group is 116.

[0068] Preferably, the battery pack design consistency alignment points are four SOC points of 5%, 20%, 30% and 95%.

[0069] Preferably, each battery cell has a rated energy storage of 614Wh.

[0070] Preferably, the temperature set in step (2), step (3) and step (4) is 15°C.

[0071] Preferably, the battery pack adopts a 60kWh150Ah ternary battery pack.

[0072] Embodiment 4, a lithium ion battery consistency evaluation method, comprising the following processing steps:

[0073] Step 1: Design a series of consistent SOC points according to the battery pack usage requirements, such as 5%, 20%, 50%, 80%, and 95%.

[0074] Step 2: Perform the first charge and discharge cycle in a room at 40°C, short-circuit the SOC for 3 seconds at each consistency, and record the short-circuit current.

[0075] Step 3: Using the heat generated by the first discharge, perform a second charge and discharge cycle at an elevated temperature, short-circuit for 3.5 seconds at each consistency alignment SOC, and record the short-circuit current.

[0076] Step 4: Using the heat generated by the second discharge, perform a third charge and discharge cycle in an elevated temperature environment, short-circuit for 3.5 seconds at each consistency alignment SOC, and record the short-circuit current.

[0077] Step 5: Use the maximum discharge current at the three temperatures as the chemical reaction rate of the lithium battery under the conditions, and use the graphical method to calculate the activation energy of each consistency calibration point.

[0078] Step 6: Count the capacity, coulombic efficiency, energy efficiency, and consistency-to-point activation energy of the battery cells.

[0079] Step 7: Perform cycle tests on the parameters with different discreteness combinations to obtain cycle life retention rates after different discreteness combinations.

[0080] Step 8: Use the relationship between the above parameter dispersion and cycle life retention rate as a lithium-ion battery consistency evaluation method.

[0081] Preferably, the lithium-ion battery used for the extended-range vehicle is provided with three charging modes, namely, slow charging, fast charging and range extender charging.

[0082] Preferably, the battery pack adopts a single-string 400V 150Ah design, each group requires 111 cells, plus 5 maintenance cells, and the number of cells in each group is 116.

[0083] Preferably, the battery pack design consistency alignment points are four SOC points of 5%, 20%, 30% and 95%.

[0084] Preferably, each battery cell has a rated energy storage of 614Wh.

[0085] Preferably, the temperature set in step (2), step (3) and step (4) is 15°C.

[0086] Preferably, the battery pack adopts a 60kWh150Ah ternary battery pack.

Claims

1. A lithium-ion battery consistency assessment method, comprising the following processing steps: Step (1), design a series of consistent SOC points according to the battery pack usage requirements, and the battery pack design consistent SOC points are 5%, 20%, 30% and 95% respectively; Step (2), charge and discharge the battery cell once at the designed rated rate in an air-conditioned environment at a temperature of T1, short-circuit at each consistency alignment point for t, and test the maximum short-circuit current, where t is the short-circuit time; Step (3), repeat the test of step (2) in the room temperature T2 environment; Step (4), repeat the test of step (2) in a high temperature room at a temperature of T3; Step (5), using the maximum discharge current at the three temperatures as the chemical reaction rate of the lithium battery under the conditions, and using a graphical method to calculate the activation energy of each consistency calibration point; Step (6), calculating the capacity, coulombic efficiency, energy efficiency, consistency and activation energy of the battery cells; Step (7), performing cycle tests according to the above parameters with different discreteness groups, and obtaining the cycle life retention rate after the different discreteness groups; Step (8), using the relationship between the above parameter dispersion and the cycle life retention rate as a lithium-ion battery consistency evaluation method.

2. A lithium-ion battery consistency assessment method according to claim 1, characterized in that: The lithium-ion battery used for the extended-range vehicle is provided with three charging modes, which are respectively set to slow charging, fast charging and range extender charging.

3. A lithium-ion battery consistency assessment method according to claim 1, characterized in that: The battery pack adopts a single-string 400V 150Ah design. Each group requires 111 battery cells, plus 5 maintenance battery cells, and the number of battery cells in each group is 116.

4. A lithium-ion battery consistency assessment method according to claim 1, characterized in that: Each battery cell has a rated energy storage of 614Wh.

5. A lithium-ion battery consistency assessment method according to claim 1, characterized in that: The temperature T1 in step (2) is 15°C, the temperature T2 in step (3) is 25°C, and the temperature T3 in step (4) is 40°C.

6. A lithium-ion battery consistency assessment method according to claim 1, characterized in that: The battery pack adopts a 60kWh, 150Ah ternary battery pack.

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