Control system and control method for battery formation test

Abstract

The invention relates to the technical field of lithium batteries, in particular to a control system and a control method for a battery formation test. The control method for the battery formation test comprises the following steps: sequentially assembling a lithium-rich manganese-based positive pole piece, a graphite negative pole piece, an electrolyte, a diaphragm and an aluminum shell into a battery according to a battery assembling process; carrying out high-temperature aging shelving on the assembled battery; carrying out formation charging and discharging on the battery subjected to high-temperature aging shelving; carrying out capacity grading on the formed and charged and discharged battery; the capacity grading step specifically comprises the following steps of: charging to voltage D1 at constant current at multiplying power X1; performing constant-voltage charging to a cut-off current E; carrying out constant-current discharge at a multiplying power X1 to a voltage G; and capacity grading tests of four circles of capacity grading capacities under different multiplying powers are carried out in sequence. According to the invention, a full battery formation process is optimized, and a relatively high capacity is exerted under a relatively low voltage, so that the capacity requirement is met, and meanwhile, the cycle performance of the battery is not reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a control system and a control method for battery formation testing. Background Art

[0002] With the rapid development of new energy vehicles, OEMs have higher and higher requirements for batteries. Whether it is to increase battery energy density or reduce costs, they have put forward requirements for leapfrogging the cost performance to meet the requirements of power vehicles for endurance and battery pack costs. As the most important part of the battery, the positive electrode material is particularly critical for the selection and use of the positive electrode. The positive electrode materials quantified in the market include ternary materials, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate and lithium manganese iron phosphate. Ternary materials and lithium cobalt oxide are relatively expensive, and the energy density of lithium manganese oxide and lithium iron phosphate cannot meet the growing demand. At this time, lithium-rich manganese-based positive electrode materials with both high energy density and low cost have entered the field of vision of R&D personnel. The chemical formula is xLi2MnO3·(1-x)LiMO2, M=Ni, Co, Mn, and the presence of Li2MnO3 phase provides special performance and usage methods for lithium-rich manganese-based materials. However, the existence of lithium-rich manganese-based problems is also the reason why it has not been applied in mass production. The capacity is higher under high voltage, but due to the instability of the Li2MnO3 phase at high voltage, the cycle performance is poor. The cycle is better under low voltage, and the capacity is difficult to exert. Therefore, the problem of capacity and cycle contradiction between lithium-rich manganese-based batteries needs to be effectively solved. Summary of the invention

[0003] Based on this, it is necessary to provide a control system and a control method for battery formation testing to solve at least one of the above technical problems.

[0004] A control method for battery formation testing comprises the following steps:

[0005] (1) Battery assembly: assembling a lithium-rich manganese-based positive electrode sheet, a graphite negative electrode sheet, an electrolyte, a separator and an aluminum casing into a battery in sequence according to a battery assembly process;

[0006] (2) placing the battery assembled in step (1) on high temperature aging standby;

[0007] (3) performing formation charging and discharging on the battery that has been shelved after high temperature aging in step (2);

[0008] (4) performing capacity division on the battery after charge and discharge in step (3); the capacity division steps are specifically as follows: charging at a constant current of X1 to a voltage of D1; charging at a constant voltage to a cut-off current of E; discharging at a constant current of X1 to a voltage of G; and sequentially performing four cycles of capacity division tests at different rates;

[0009] (5) Perform a cycle test on the battery after the capacity division test in step (4); according to the capacity division step, the rate is changed to X2 rate, and the other parameters are kept the same, and a charge and discharge cycle test is performed.

[0010] In one embodiment of the present invention, the chemical formula of the lithium-rich manganese-based positive electrode material on the lithium-rich manganese-based positive electrode plate is: xLi2MnO3·(1-x)LiMO2, wherein 0.1<x<0.5, M is Ni, Co or Mn, and the proportion of transition metal depends on the value of x.

[0011] In one embodiment of the present invention, the formation charge and discharge step in step (3) is specifically:

[0012] Step 1: Perform one cycle of conventional formation steps, the steps are: constant current charging at rate A to SOC state M; constant current charging at rate B to cut-off voltage D; constant voltage charging at voltage D to cut-off current ≤ E; constant current discharge at rate F for time T; cut off the airbag part of the battery and perform secondary sealing; discharge at rate F to voltage G;

[0013] The second step: perform n cycles of high discharge cut-off voltage formation, the steps are: constant current charging at rate a to SOC state m; constant current charging at rate b to cut-off voltage d; constant voltage charging at voltage d to cut-off current ≤ e; constant current discharge at rate f to voltage g, a total of n+1 cycles of formation steps.

[0014] In one embodiment of the present invention, the high temperature aging storage process in step (2) is: storage in a 40-60° C. constant temperature box for 24-72 hours.

[0015] In one embodiment of the present invention, the formation parameters in the formation charge and discharge step are as follows: 0.01C≤A≤0.1C, 20%≤M≤60%, 0.05C≤B≤0.33C, 4.2V≤D≤4.5V, 4.2V≤D1≤4.5V, 0.01C≤E≤0.05C, 0.05C≤F≤0.33C, 2.0V≤G≤2.8V, 0.5h≤T≤15h; 1≤n≤10, 0.01C≤a≤0.1C, 20%≤m≤60%, 0.05C≤b≤0.33C, 4.2V≤d≤4.5V, 0.01C≤e≤0.05C, 0.05C≤f≤0.33C, 3.0V≤g≤4.0V; wherein the unit C represents the rate unit.

[0016] In one embodiment of the present invention, if the constant current charging rates of the first step and the second step in step (3) are the same, the first step and the second step are combined into one step.

[0017] In one embodiment of the present invention, the capacity division step in step (4) is tested in sequence according to the capacity division parameter X1=0.1 / 0.2 / 0.5 / 1C.

[0018] In one embodiment of the present invention, the cycle parameter in step (5) is 0.33C≤X2≤1C.

[0019] The present invention also provides a control system for battery formation testing, which is applied to the control method for battery formation testing as described in any one of the above items.

[0020] The commonly used formation process for lithium-rich manganese-based batteries is usually obtained by fine-tuning the full battery formation process commonly used in ternary materials, lithium iron phosphate and other materials. This formation method is relatively simple and fails to fundamentally bring into play the characteristics that lithium-rich manganese-based batteries should have, so that lithium-rich manganese-based batteries cannot have both capacity and cycle advantages, which is one of the biggest problems in the commercialization of lithium-rich manganese-based batteries. The existing formation mainly has the following two problems:

[0021] (1) Most of the formations are formed with a higher charge cut-off voltage (≥4.5V) in the first cycle and used with a lower charge cut-off voltage (≤4.5V). This method is too activated in the first cycle, the structure is severely damaged, and the redox reversibility is poor, resulting in poor subsequent cycles.

[0022] (2) In order to improve the cycle retention rate, a lower charge cut-off voltage (≤4.5V) is used for formation and use. This method uses more stable materials and reduces electrolyte decomposition, ensuring material circulation, but its capacity is reduced, making it difficult to fully exert the performance of lithium-rich manganese-based batteries.

[0023] Lithium-rich manganese-based materials can be used as solid solutions to analyze material properties. They are mainly composed of two phases, with a chemical formula of xLi2MnO3·(1-x)LiMO2, where M=Ni, Co, Mn. Due to the existence of the Li2MnO3 phase, they have a theoretical capacity of ≥250mAh / g. The first cycle charging stage of lithium-rich manganese-based full batteries is divided into two platforms. The area below 4.5V is mainly due to the oxidation of the transition metal M in LiMO2 (M=Ni, Co, Mn) to provide material capacity, and the area above 4.5V is mainly due to the oxidation of anionic oxygen in Li2MnO3 to provide capacity. Both are present near the 4.5V limit. Due to its special charging platform, the use of its voltage is particularly critical. The anionic oxygen in Li2MnO3 is separated from the material in the form of oxygen free radicals, and gradually migrates to the surface of the material. When the charging cut-off voltage is high, the oxygen free radicals combine with themselves to generate oxygen, or react with electrolysis to generate CO and CO2, and volatilize, completely detaching from the material, resulting in a serious reduction in the reduction reversibility of the anionic type during discharge reduction, a serious phase change of the material, and a serious reduction in the cycle retention rate; but when the charging cut-off voltage is low, because it does not reach the reaction platform of Li2MnO3, the charging capacity fails to be brought into play, which seriously affects the battery discharge capacity. In view of the above situation, the present invention optimizes the full battery formation process, so that the process of its Li2MnO3 activation is not violently activated due to high voltage, resulting in a large structural change, but by increasing the discharge cut-off voltage at low voltage, so that it is not completely discharged, and charging is performed again, the material is continuously oxidized, and the Li2MnO3 activation process is slowly carried out. This method exerts a higher capacity at a relatively low voltage, allowing it to meet the capacity requirements and the cycle performance is not reduced at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a comparison diagram of the 25°C normal temperature cycle curves of the embodiment of the present invention and the comparative example;

[0025] Figure 2 This is a formation charge-discharge curve diagram of Example 1 of the present invention;

[0026] Figure 3 0.1C charge-discharge curves of Example 1 and Comparative Example 1 of the present invention;

[0027] Figure 4 0.2C charge-discharge curves of Example 1 and Comparative Example 1 of the present invention;

[0028] Figure 5 0.5C charge-discharge curves of Example 1 and Comparative Example 1 of the present invention;

[0029] Figure 6 1C charge-discharge curve diagram of Example 1 and Comparative Example 1 of the present invention.

[0030] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The technical method of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In addition, the accompanying drawings are only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. The functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor methods and / or microcontroller methods.

[0033] It should be understood that, although the terms "first", "second", etc. may be used herein to describe various units, these units should not be limited by these terms. These terms are used only to distinguish one unit from another unit. For example, without departing from the scope of the exemplary embodiments, the first unit may be referred to as the second unit, and similarly the second unit may be referred to as the first unit. The term "and / or" used herein includes any and all combinations of one or more of the listed associated items.

[0034] To achieve the above object, the present invention provides a control method for battery formation test, comprising the following steps:

[0035] (1) Battery assembly, specifically comprising the following steps: assembling a lithium-rich manganese-based positive electrode sheet, a graphite negative electrode sheet, an electrolyte, a separator and an aluminum casing into a battery in accordance with a battery assembly process;

[0036] (2) placing the battery assembled in step (1) on high temperature aging standby;

[0037] (3) performing formation charging and discharging on the battery that has been shelved after high temperature aging in step (2);

[0038] (4) performing capacity division on the battery after charge and discharge in step (3); the capacity division steps are specifically as follows: charging at a constant current of X1 to a voltage of D1; charging at a constant voltage to a cut-off current of E; discharging at a constant current of X1 to a voltage of G; and sequentially performing four cycles of capacity division tests at different rates;

[0039] (5) Perform a cycle test on the battery after the capacity division test in step (4); according to the capacity division step, the rate is changed to X2 rate, and the other parameters are consistent (same), and a charge and discharge cycle test is performed.

[0040] In one embodiment of the present invention, the chemical formula of the lithium-rich manganese-based positive electrode material on the lithium-rich manganese-based positive electrode plate is: xLi2MnO3·(1-x)LiMO2, wherein 0.1<x<0.5, M is Ni, Co or Mn, and the proportion of transition metal depends on the value of x.

[0041] In one embodiment of the present invention, the formation charge and discharge step in step (3) is specifically:

[0042] Step 1: Perform one cycle of conventional formation steps, the steps are: constant current charging at rate A to SOC state M; constant current charging at rate B to cut-off voltage D; constant voltage charging at voltage D to cut-off current ≤ E; constant current discharge at rate F for time T; cut off the airbag part of the battery and perform secondary sealing; discharge at rate F to voltage G;

[0043] The second step: perform n cycles of high discharge cut-off voltage formation, the steps are: constant current charging at rate a to SOC state m; constant current charging at rate b to cut-off voltage d; constant voltage charging at voltage d to cut-off current ≤ e; constant current discharge at rate f to voltage g, a total of n+1 cycles of formation steps.

[0044] In one embodiment of the present invention, the high temperature aging storage process in step (2) is: storage in a 40-60° C. constant temperature box for 24-72 hours.

[0045] In one embodiment of the present invention, the formation parameters in the formation charge and discharge step are as follows: 0.01C≤A≤0.1C, 20%≤M≤60%, 0.05C≤B≤0.33C, 4.2V≤D≤4.5V, 4.2V≤D1≤4.5V, 0.01C≤E≤0.05C, 0.05C≤F≤0.33C, 2.0V≤G≤2.8V, 0.5h≤T≤15h; 1≤n≤10, 0.01C≤a≤0.1C, 20%≤m≤60%, 0.05C≤b≤0.33C, 4.2V≤d≤4.5V, 0.01C≤e≤0.05C, 0.05C≤f≤0.33C, 3.0V≤g≤4.0V; wherein the unit C represents the rate unit.

[0046] In one embodiment of the present invention, if the constant current charging rates of the first step and the second step in step (3) are the same, the first step and the second step are combined into one step.

[0047] In one embodiment of the present invention, the capacity division step in step (4) is tested in sequence according to the capacity division parameter X1=0.1 / 0.2 / 0.5 / 1C.

[0048] In one embodiment of the present invention, the cycle parameter in step (5) is 0.33C≤X2≤1C.

[0049] The present invention also provides a control system for battery formation testing, which is applied to the control method for battery formation testing as described in any one of the above items.

[0050] The commonly used formation process for lithium-rich manganese-based batteries is usually obtained by fine-tuning the full battery formation process commonly used in ternary materials, lithium iron phosphate and other materials. This formation method is relatively simple and fails to fundamentally bring into play the characteristics that lithium-rich manganese-based batteries should have, so that lithium-rich manganese-based batteries cannot have both capacity and cycle advantages, which is one of the biggest problems in the commercialization of lithium-rich manganese-based batteries. The existing formation mainly has the following two problems:

[0051] (1) Most of the formations are formed with a higher charge cut-off voltage (≥4.5V) in the first cycle and used with a lower charge cut-off voltage (≤4.5V). This method is too activated in the first cycle, the structure is severely damaged, and the redox reversibility is poor, resulting in poor subsequent cycles.

[0052] (2) In order to improve the cycle retention rate, a lower charge cut-off voltage (≤4.5V) is used for formation and use. This method uses more stable materials and reduces electrolyte decomposition, ensuring material circulation, but its capacity is reduced, making it difficult to fully exert the performance of lithium-rich manganese-based batteries.

[0053] Lithium-rich manganese-based materials can be used as solid solutions to analyze material properties. They are mainly composed of two phases, with a chemical formula of xLi2MnO3·(1-x)LiMO2, where M=Ni, Co, Mn. Due to the existence of the Li2MnO3 phase, they have a theoretical capacity of ≥250mAh / g. The first cycle charging stage of lithium-rich manganese-based full batteries is divided into two platforms. The area below 4.5V is mainly due to the oxidation of the transition metal M in LiMO2 (M=Ni, Co, Mn) to provide material capacity, and the area above 4.5V is mainly due to the oxidation of anionic oxygen in Li2MnO3 to provide capacity. Both are present near the 4.5V limit. Due to its special charging platform, the use of its voltage is particularly critical. The anionic oxygen in Li2MnO3 is separated from the material in the form of oxygen free radicals, and gradually migrates to the surface of the material. When the charging cut-off voltage is high, the oxygen free radicals combine with themselves to generate oxygen, or react with electrolysis to generate CO and CO2, and volatilize, completely detaching from the material, resulting in a serious reduction in the reduction reversibility of the anionic type during discharge reduction, a serious phase change of the material, and a serious reduction in the cycle retention rate; but when the charging cut-off voltage is low, because it does not reach the reaction platform of Li2MnO3, the charging capacity fails to be brought into play, which seriously affects the battery discharge capacity. In view of the above situation, the present invention optimizes the full battery formation process, so that the process of its Li2MnO3 activation is not violently activated due to high voltage, resulting in a large structural change, but by increasing the discharge cut-off voltage at low voltage, so that it is not completely discharged, and charging is performed again, the material is continuously oxidized, and the Li2MnO3 activation process is slowly carried out. This method exerts a higher capacity at a relatively low voltage, allowing it to meet the capacity requirements and the cycle performance is not reduced at the same time. After the above high discharge cut-off voltage formation step, the capacity of the lithium-rich manganese-based battery is significantly improved after the capacity is divided, and the cycle is not reduced due to the slow activation of the Li2MnO3 phase. The defects of the lithium-rich manganese-based battery are solved from the battery formation level, which not only improves the capacity but also ensures that the cycle is not reduced, thereby promoting the development and application of lithium-rich manganese-based batteries. For example, the battery formation test control method described in the present invention can be a battery formation test control method.

[0054] See also Figures 1 to 6 , Embodiment 1: A control method for battery formation test, the specific steps are as follows:

[0055] (1) Battery assembly: The lithium-rich manganese-based positive electrode sheet, graphite negative electrode sheet, electrolyte, separator, and aluminum casing are assembled into a battery in sequence according to conventional battery assembly processes; the chemical formula of the lithium-rich manganese-based positive electrode material is 0.3Li2MnO3·0.7LiNi 0.5 Mn 0.5 O2;

[0056] (2) subjecting the battery assembled in step (1) to high temperature aging at 45° C. for 24 h;

[0057] (3) The battery placed at high temperature in step (2) is subjected to formation charge and discharge, firstly, a conventional formation step is performed for one cycle, the steps are as follows: constant current charging at a rate of 0.03C to a SOC state of 40% → constant current charging at a rate of 0.1C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → constant current discharge at a rate of 0.1C for 3h → the airbag part of the battery is cut off and a secondary seal is performed → constant current discharge at a rate of 0.1C to a voltage of 2.5V; secondly, a high discharge cut-off voltage formation is performed for one cycle, the steps are as follows: constant current charging at a rate of 0.02C to a SOC state of 40% → constant current charging at a rate of 0.1C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → discharge at a rate of 0.1C to a voltage of 3.0V, a total of 2 cycles of formation steps;

[0058] (4) The battery formed in step (3) is subjected to capacity division, wherein the capacity division steps are: constant current charging at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 4.47V → constant voltage charging to a cut-off current of 0.05C → constant current discharge at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 2.5V;

[0059] (5) subjecting the battery after capacity division in step (4) to a cycle test, charging and discharging according to the capacity division steps, with the rate changed to 0.5C rate, and other parameters kept the same, and performing a charge and discharge cycle test at room temperature of 25°C;

[0060] Embodiment 2: A control method for battery formation test, the specific steps are as follows:

[0061] (1) Battery assembly: The lithium-rich manganese-based positive electrode sheet, graphite negative electrode sheet, electrolyte, separator, and aluminum casing are assembled into a soft-pack battery in accordance with conventional battery assembly processes; the chemical formula of the lithium-rich manganese-based positive electrode material is 0.3Li2MnO3·0.7LiNi 0.5 Mn 0.5 O2;

[0062] (2) subjecting the battery assembled in step (1) to high temperature aging at 45° C. for 48 h;

[0063] (3) The battery placed at high temperature in step (2) is subjected to formation charge and discharge, firstly, a conventional formation step is performed for one cycle, the steps are as follows: constant current charging at a rate of 0.06C to a SOC state of 50% → constant current charging at a rate of 0.2C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → constant current discharge at a rate of 0.2C for 2.5h → the airbag part of the battery is cut off and a secondary seal is performed → constant current discharge at a rate of 0.2C to a voltage of 2.0V; secondly, a high discharge cut-off voltage formation is performed for three cycles, the steps are as follows: constant current charging at a rate of 0.05C to a SOC state of 50% → constant current charging at a rate of 0.2C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → discharge at a rate of 0.2C to a voltage of 3.3V, a total of four formation steps;

[0064] (4) The battery formed in step (3) is subjected to capacity division, wherein the capacity division steps are: constant current charging at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 4.47V → constant voltage charging to a cut-off current of 0.05C → constant current discharge at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 2.0V;

[0065] (5) subjecting the battery after capacity division in step (4) to a cycle test, charging and discharging according to the capacity division steps, with the rate changed to 0.5C rate, and other parameters kept the same, and performing a charge and discharge cycle test at room temperature of 25°C;

[0066] Embodiment 3: A control method for battery formation test, the specific steps are as follows:

[0067] (1) Battery assembly: The lithium-rich manganese-based positive electrode sheet, graphite negative electrode sheet, electrolyte, separator, and aluminum casing are assembled into a soft-pack battery in accordance with conventional battery assembly processes; the chemical formula of the lithium-rich manganese-based positive electrode material is 0.3Li2MnO3·0.7LiNi 0.5 Mn 0.5 O2;

[0068] (2) subjecting the battery assembled in step (1) to high temperature aging at 45° C. for 48 h;

[0069] (3) The battery placed at high temperature in step (2) is subjected to formation charge and discharge, firstly, a conventional formation step is performed for one cycle, the steps are as follows: constant current charging at a rate of 0.06C to a SOC state of 50% → constant current charging at a rate of 0.2C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → constant current discharge at a rate of 0.2C for 2.5h → the airbag part of the battery is cut off and a secondary seal is performed → constant current discharge at a rate of 0.2C to a voltage of 2.0V; secondly, a high discharge cut-off voltage formation is performed for three cycles, the steps are as follows: constant current charging at a rate of 0.05C to a SOC state of 50% → constant current charging at a rate of 0.2C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → discharge at a rate of 0.2C to a voltage of 3.8V, a total of four formation steps;

[0070] (4) The battery formed in step (3) is subjected to capacity division, wherein the capacity division steps are: constant current charging at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 4.47V → constant voltage charging to a cut-off current of 0.05C → constant current discharge at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 2.0V;

[0071] (5) subjecting the battery after capacity division in step (4) to a cycle test, charging and discharging according to the capacity division steps, with the rate changed to 0.5C rate, and other parameters kept the same, and performing a charge and discharge cycle test at room temperature of 25°C;

[0072] Comparative Example 1: Without the high discharge cut-off voltage formation step, the conventional formation was adopted and the capacity was directly divided. The specific steps are as follows:

[0073] (1) Battery assembly: The lithium-rich manganese-based positive electrode sheet, graphite negative electrode sheet, electrolyte, separator, and aluminum casing are assembled into a soft-pack battery in accordance with conventional battery assembly processes; the chemical formula of the lithium-rich manganese-based positive electrode material is 0.3Li2MnO3·0.7LiNi 0.5 Mn 0.5 O2;

[0074] (2) subjecting the battery assembled in step (1) to high temperature aging at 45° C. for 24 h;

[0075] (3) The battery placed at high temperature in step (2) is subjected to formation charge and discharge, firstly, a conventional formation step is performed for one cycle, wherein the steps are as follows: constant current charging at a rate of 0.06C to a SOC state of 50% → constant current charging at a rate of 0.2C to a cut-off voltage of 4.47V → constant voltage charging at a voltage of 4.47V to a cut-off current of ≤0.05C → constant current discharge at a rate of 0.2C for 2.5h → the airbag portion of the battery is cut off and secondary sealing is performed → constant current discharge at a rate of 0.2C to a voltage of 2.0V; a total of one formation step;

[0076] (4) The battery formed in step (3) is subjected to capacity division, wherein the capacity division steps are: constant current charging at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 4.47V → constant voltage charging to a cut-off current of 0.05C → constant current discharge at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 2.0V;

[0077] Comparative Example 2: Without the high discharge cut-off voltage formation step, a higher charge cut-off voltage formation step (4.5V) was adopted, and then a lower charge low voltage (4.47V) was adopted for direct capacity division. The specific steps are as follows;

[0078] (1) Battery assembly: The lithium-rich manganese-based positive electrode sheet, graphite negative electrode sheet, electrolyte, separator, and aluminum casing are assembled into a soft-pack battery in accordance with conventional battery assembly processes; the chemical formula of the lithium-rich manganese-based positive electrode material is 0.3Li2MnO3·0.7LiNi 0.5 Mn 0.5 O2;

[0079] (2) subjecting the battery assembled in step (1) to high temperature aging at 45° C. for 24 h;

[0080] (3) The battery placed at high temperature in step (2) is subjected to formation charge and discharge, firstly, a conventional formation step is performed for one cycle, wherein the steps are as follows: constant current charging at a rate of 0.06C until the SOC state is 50% → constant current charging at a rate of 0.2C until the cut-off voltage is 4.5V → constant voltage charging at a voltage of 4.5V until the cut-off current is ≤0.05C → constant current discharge at a rate of 0.2C for 2.5h → the airbag part of the battery is cut off and secondary sealing is performed → constant current discharge at a rate of 0.2C until the voltage is 2.0V; a total of one formation step;

[0081] (4) The battery formed in step (3) is subjected to capacity division, wherein the capacity division steps are: constant current charging at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 4.47V → constant voltage charging to a cut-off current of 0.05C → constant current discharge at a rate of 0.1C / 0.2C / 0.5C / 1C to a voltage of 2.0V;

[0082] Performance test comparison: By comparing the embodiments and comparative examples, the following conclusions were drawn: (1) Compared with the first cycle formed with a high charge cut-off voltage (4.5V), the cycle performance was significantly improved by using the battery at a lower voltage (4.47V); (2) Compared with the first cycle and the use of the battery with a lower charge cut-off voltage (≤4.47V), the battery capacity was significantly improved.

[0083] In summary, after the battery is formed by the method of the present invention, both the capacity and the cycle performance are taken into account, as shown in Table 1:

[0084] Table 1: Capacity test comparison table

[0085]

[0086] Therefore, the embodiments should be regarded as illustrative and non-restrictive from all points, and the scope of the present invention is limited by the appended claims rather than the above description, and it is therefore intended that all changes falling within the meaning and range of equivalent elements of the application documents are included in the present invention.

[0087] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features invented herein.

Claims

1. A control method for battery formation testing, characterized in that: The following steps are involved: (1) Battery assembly: (2) placing the battery assembled in step (1) on high temperature aging standby; (3) performing formation charging and discharging on the battery that has been shelved after high temperature aging in step (2); (4) performing capacity division on the battery after charge and discharge in step (3); the capacity division steps are specifically as follows: charging at a constant current of X1 to a voltage of D1; charging at a constant voltage to a cut-off current of E; discharging at a constant current of X1 to a voltage of G; and sequentially performing four cycles of capacity division tests at different rates; (5) Performing a cycle test on the battery after the capacity division test in step (4); performing a charge and discharge cycle test at a rate of X2 according to the capacity division step.

2. The battery formation test control method according to claim 1, characterized in that: The chemical formula of the lithium-rich manganese-based positive electrode material on the lithium-rich manganese-based positive electrode plate is: xLi2MnO3·(1-x)LiMO2, wherein 0.1<x<0.5, M is Ni, Co or Mn, and the proportion of transition metal depends on the value of x.

3. The battery formation test control method according to claim 1, characterized in that: The formation charge and discharge steps in step (3) are specifically as follows: Step 1: Perform one cycle of conventional formation steps, the steps are: constant current charging at rate A to SOC state M; constant current charging at rate B to cut-off voltage D; Charge at constant voltage D until cut-off current ≤ E; discharge at constant current rate F for time T; The battery is cut off from the airbag part and sealed for the second time; discharged at a rate of F to a voltage of G; Step 2: Perform high discharge cut-off voltage to form n cycles, the steps are: charge at a constant current rate a until the SOC state is m; Charge at a constant current rate b to a cut-off voltage d; Charge at a constant voltage of d until the cut-off current is ≤ e; discharge at a constant current of rate f to a voltage of g, for a total of n+1 formation steps.

4. The battery formation test control method according to claim 1, characterized in that: The high temperature aging process in step (2) is: placing in a constant temperature box at 40-60°C for 24-72 hours.

5. The battery formation test control method according to claim 1, characterized in that: The battery assembly in step (1) specifically includes: assembling a lithium-manganese-rich positive electrode plate, a graphite negative electrode plate, an electrolyte, a separator and an aluminum casing into a battery in sequence according to a battery assembly process.

6. The battery formation test control method according to claim 5, characterized in that: The formation parameters in the formation charge and discharge step are as follows: 0.01C≤A≤0.1C, 20%≤M≤60%, 0.05C≤B≤0.33C, 4.2V≤D≤4.5V, 4.2V≤D1≤4.5V, 0.01C≤E≤0.05C, 0.05C≤F≤0.33C, 2.0V≤G≤2.8V, 0.5h≤T≤15h; 1≤n≤10, 0.01C≤a≤0.1C, 20%≤m≤60%, 0.05C≤b≤0.33C, 4.2V≤d≤4.5V, 0.01C≤e≤0.05C, 0.05C≤f≤0.33C, 3.0V≤g≤4.0V; wherein the unit C represents the rate unit.

7. The battery formation test control method according to claim 6, characterized in that: In step (3), if the constant current charging rates of the first step and the second step are the same, the first step and the second step are combined into one step.

8. The battery formation test control method according to claim 1, characterized in that: The capacity division step in step (4) is tested in sequence according to the capacity division parameter X1=0.1 / 0.2 / 0.5 / 1C.

9. The battery formation test control method according to claim 1, characterized in that: The cycle parameter in step (5) is 0.33C≤X2≤1C.

10. A control system for battery formation testing, characterized in that: Applicable to the control method for battery formation test as described in any one of claims 1 to 9.

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