Formation method of lithium-rich manganese battery

Abstract

The formation method comprises the following steps: charging the lithium-rich manganese battery to be formed to a first capacity at a first rate in a constant-current manner, then charging the lithium-rich manganese battery to a second capacity at a second rate in a constant-current manner, then charging the lithium-rich manganese battery to a first voltage at a third rate in a constant-current and constant-voltage manner, and taking a first current as a cut-off current, discharging to a second voltage at a fourth multiplying power constant current; wherein the first multiplying power and the second multiplying power are smaller than the third multiplying power, the first capacity is smaller than the second capacity, and the second capacity is smaller than 100% SOC. According to the method, the lithium-manganese-rich battery to be formed is subjected to constant-current charging with low current, so that a stable and uniform catholyte interface film is formed on the surface of the lithium-manganese-rich positive electrode material, the structural stability of the lithium-manganese-rich positive electrode material is protected, gas production is reduced, and then the lithium-manganese-rich battery is subjected to constant-current and constant-voltage charging with higher current to reach the first voltage; therefore, the reaction time of lattice oxygen of the lithium-manganese-rich positive electrode material and electrolyte is shortened, and gas generation is reduced.

Description

Technical Field

[0001] This application relates to the field of battery formation technology, specifically to a formation method for a lithium-rich manganese battery. Background Technology

[0002] Lithium-rich manganese cathode material is a high-energy-density cathode material. However, lithium-rich manganese cathode material has poor stability and suffers from problems such as oxygen evolution, low initial coulombic efficiency, transition metal dissolution, and voltage decay. In addition, the high upper limit cutoff voltage of lithium-rich manganese cathode material can easily lead to electrolyte decomposition. All of these factors hinder the industrialization of lithium-rich manganese cathode material. Therefore, it is necessary to suppress gas generation of lithium-rich manganese cathode material under high pressure.

[0003] The high specific capacity of lithium-rich manganese materials mainly comes from lattice oxygen oxidation under high voltage. Its structural characteristics result in poor electronic conductivity. In order to realize its high capacity, it needs to be activated under high voltage. The battery gas generation in the related formation methods is high. Summary of the Invention

[0004] This application provides a formation method for lithium-rich manganese batteries, aiming to solve the problem of excessive gas production during the formation of lithium-rich manganese batteries.

[0005] This application provides a method for forming a lithium-rich manganese battery, comprising: The lithium-rich manganese battery to be formed is charged to the first capacity at a constant current rate of the first rate, then charged to the second capacity at a constant current rate of the second rate, then charged to the first voltage at a constant current and constant voltage rate of the third rate, and then discharged to the second voltage at a constant current rate of the fourth rate. Wherein, the first multiplier and the second multiplier are less than the third multiplier, the first capacity is less than the second capacity, and the second capacity is less than 100% SOC.

[0006] Optionally, in some embodiments of this application, the first multiplier is less than the second multiplier.

[0007] Optionally, in some embodiments of this application, the first expansion rate is 0.01C-0.05C; and / or The second multiplier is 0.02C-0.08C; and / or The third multiplier is 0.05C-0.1C; and / or The fourth multiple is 0.05C-0.1C.

[0008] Optionally, in some embodiments of this application, the first capacity is 5% SOC-20% SOC; and / or The second capacity is 20%SOC-40%SOC.

[0009] Optionally, in some embodiments of this application, the first voltage is 4.4V-4.7V; and / or The first current is 0.02C-0.05C; and / or The second voltage is 2.0V-2.5V.

[0010] Optionally, in some embodiments of this application, the method further includes: charging the lithium-rich manganese battery, which has been discharged to the second voltage, to the third voltage at a constant current and constant voltage rate of the fifth, and then discharging it to the fourth voltage at a constant current rate of the sixth, using the second current as the cutoff current. The third voltage is higher than the second voltage.

[0011] Optionally, in some embodiments of this application, the fifth multiplier is 0.1C-0.2C; and / or The sixth multiplier is 0.1C-0.2C.

[0012] Optionally, in some embodiments of this application, the third voltage is 4.4V-4.7V; and / or The second current is 0.02C-0.05C; and / or The fourth voltage is 2.0V-2.5V.

[0013] Optionally, in some embodiments of this application, before charging to the first capacity at a first rate constant current, the method further includes: subjecting the lithium-rich manganese battery to be formed to a first settling treatment; and / or Before discharging to the second voltage at a constant current rate of the fourth multiple, the method further includes: subjecting the lithium-rich manganese battery, charged to the second capacity, to a second settling treatment; and / or Before discharging to the fourth voltage at a constant current rate of the sixth multiple, the process further includes: subjecting the lithium-rich manganese battery, which has been charged to the third voltage, to a third settling treatment.

[0014] Optionally, in some embodiments of this application, the first settling time is 12h-48h; and / or The second settling time is 5 min-30 min; and / or The third settling time is 5-30 minutes.

[0015] This application first uses a small current (first rate and second rate) to charge the lithium-rich manganese battery to be formed under constant current. Under the small current, the oxidation decomposition products of the electrolyte have sufficient time to diffuse through the electrolyte to the surface of the lithium-rich manganese cathode and gradually deposit on the surface of the lithium-rich manganese cathode material, thereby forming a stable and uniform cathode electrolyte interface film (CEI film) on the surface of the lithium-rich manganese cathode material to protect the structural stability of the lithium-rich manganese cathode material and reduce gas production. Then, a larger current (third rate) is used to charge the battery to the first voltage under constant current and constant voltage. The larger current can shorten the high voltage charging time, thereby shortening the reaction time between the lattice oxygen of the lithium-rich manganese cathode material and the electrolyte and reducing gas production. Detailed Implementation

[0016] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the examples. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] This application provides a method for forming a lithium-rich manganese battery. Detailed descriptions follow. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation of the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0018] This application provides a method for forming a lithium-rich manganese battery, including: The lithium-rich manganese battery to be formed is charged to the first capacity at a constant current rate of the first rate, then charged to the second capacity at a constant current rate of the second rate, then charged to the first voltage at a constant current and constant voltage rate of the third rate, and then discharged to the second voltage at a constant current rate of the fourth rate. Wherein, the first multiplier and the second multiplier are less than the third multiplier, the first capacity is less than the second capacity, and the second capacity is less than 100% SOC.

[0019] In this application, the lithium-rich manganese battery to be formed is first charged with a constant current using a small current (first rate and second rate). Under the small current, the oxidation decomposition products of the electrolyte have sufficient time to diffuse through the electrolyte to the surface of the lithium-rich manganese cathode and gradually deposit on the surface of the lithium-rich manganese cathode material, thereby forming a stable and uniform cathode electrolyte interface film (CEI film) on the surface of the lithium-rich manganese cathode material to protect the structural stability of the lithium-rich manganese cathode material and reduce gas production. Then, a larger current (third rate) is used to charge the battery to the first voltage using a constant current and constant voltage, which can effectively activate the lithium-rich phase (Li2MnO3) of the lithium-rich manganese cathode material, improve the integrity of the phase transformation of the lithium-rich manganese cathode material, and fully activate the reversible capacity of the lithium-rich manganese cathode material. At the same time, the larger current can shorten the high-voltage charging time, thereby shortening the reaction time between the lattice oxygen of the lithium-rich manganese cathode material and the electrolyte, reducing gas production, and thus improving the battery's first efficiency and cycle stability.

[0020] Understandably, prolonged high-voltage charging can intensify the reaction between the electrolyte and lattice oxygen, leading to increased gas production and consequently greater irreversible capacity loss and reduced initial battery efficiency.

[0021] It is understood that the formation of the lithium-rich manganese battery in this application is carried out at room temperature, typically 25±3℃. Formation at room temperature reduces the gas production of the lithium-rich manganese battery. At high temperatures, lattice oxygen in the lithium-rich manganese cathode material is more easily released, and the oxidative decomposition of the electrolyte is more severe, thus exacerbating gas generation.

[0022] It is understandable that the lithium-rich manganese battery to be formed is a lithium-rich manganese battery that has completed liquid filling. SOC (State of Charge) is a percentage indicator that measures the remaining capacity of a battery.

[0023] Optionally, in some embodiments of this application, the first magnification ratio is less than the second magnification ratio. This allows for a more stable and uniform CEI film to be formed.

[0024] Optionally, in some embodiments of this application, the first multiplier is 0.01C-0.05C, for example, 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, etc. In this way, at low current, a uniform cathode electrolyte interface (CEI) film can be slowly constructed on the surface of the lithium-rich manganese cathode material, laying the foundation for the formation of a stable CEI film in the subsequent high-voltage stage.

[0025] Optionally, in some embodiments of this application, the first multiplier is 0.02C.

[0026] Optionally, in some embodiments of this application, the second ratio is 0.02C-0.08C, for example, it can be 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, etc. This can promote the decomposition of the electrolyte and improve the mechanical strength of the CEI membrane.

[0027] Optionally, in some embodiments of this application, the second multiplier is 0.05C.

[0028] Optionally, in some embodiments of this application, the third charging rate is 0.05C-0.1C, for example, it can be 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.1C, etc. In this way, the current corresponding to this charging rate is moderate, which can quickly activate the lithium-rich phase of the lithium-rich manganese cathode material, while shortening the high-voltage charging time, reducing the cell gas generation time, and improving the formation efficiency.

[0029] Optionally, in some embodiments of this application, the third multiplier is 0.1C.

[0030] Optionally, in some embodiments of this application, the fourth multiplier is 0.05C-0.1C, for example, it can be 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.1C, etc.

[0031] Optionally, in some embodiments of this application, the fourth multiplier is 0.1C.

[0032] Optionally, in some embodiments of this application, the first capacity is 5%SOC-20%SOC, for example, it can be 5%SOC, 8%SOC, 10%SOC, 12%SOC, 15%SOC, 17%SOC, 20%SOC, etc. In this way, under low current and low SOC conditions, a uniform cathode electrolyte interface (CEI) film can be slowly constructed on the surface of the lithium-rich manganese cathode material, avoiding the loosening and cracking of the CEI film caused by high current charging, and gently activating the ternary phase (LiMO2) in the lithium-rich manganese cathode material, reducing the initial polarization of the battery.

[0033] Optionally, in some embodiments of this application, the second capacity is 20%SOC-40%SOC, for example, it can be 20%SOC, 22%SOC, 25%SOC, 30%SOC, 32%SOC, 35%SOC, 37%SOC, 40%SOC, etc. Thus, at the second rate and medium SOC, the CEI film formed at the first rate and low SOC can be strengthened, enhancing the uniformity and mechanical strength of the CEI film, while simultaneously activating the capacity of the ternary phase (LiMO2) in the lithium-rich manganese cathode material.

[0034] Optionally, in some embodiments of this application, the first voltage is 4.4V-4.7V, for example, it can be 4.4V, 4.5V, 4.6V, 4.7V, etc. Thus, the voltage window of the lithium-rich manganese cathode material is 2.0V-4.8V (vs Li). + / Li), 4.4V-4.7V can balance the relationship between "capacity activation" and "stability of lithium-rich manganese cathode material / electrolyte".

[0035] It is understandable that the high capacity of lithium-rich manganese cathode materials originates from the oxygen lattice oxidation of Li2MnO3 (lithium-rich phase), and the formation at the first voltage can ensure the effective activation of the lithium-rich phase.

[0036] Optionally, in some embodiments of this application, the first voltage is 4.5V.

[0037] Optionally, in some embodiments of this application, the first current is 0.02C-0.05C, for example, it can be 0.02C, 0.03C, 0.04C, 0.05C, etc. In this way, the high-voltage charging time can be controlled, thereby shortening the reaction time between the lattice oxygen of the lithium-rich manganese cathode material and the electrolyte, reducing gas generation, and thus improving the battery's initial efficiency and cycle stability.

[0038] Optionally, in some embodiments of this application, the first current is 0.05C.

[0039] Optionally, in some embodiments of this application, the second voltage is 2.0V-2.5V, for example, it can be 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, etc.

[0040] It is understandable that discharging to 2.0V can maximize the capacity of lithium-rich manganese cathode materials, while discharging to 2.5V can protect the structure of lithium-rich manganese cathode materials, but will result in the loss of some reversible capacity.

[0041] Optionally, in some embodiments of this application, the second voltage is 2.0V. This allows for the maximization of the capacity of the lithium-rich manganese battery, while also ensuring a more stable structure for the lithium-rich manganese cathode material.

[0042] Optionally, in some embodiments of this application, before charging to the first capacity at a first rate of constant current, the process further includes: subjecting the lithium-rich manganese battery to be formed to a first settling treatment. This allows the electrolyte to fully wet the lithium-rich manganese cathode material, laying the foundation for the subsequent formation of a uniform and stable CEI film.

[0043] Optionally, in some embodiments of this application, the first settling time is 12h-48h, for example, it can be 12h, 18h, 20h, 25h, 30h, 35h, 40h, 45h, 48h, etc.

[0044] Optionally, in some embodiments of this application, before the constant current discharge at the fourth rate to the second voltage, the process further includes: subjecting the lithium-rich manganese battery charged to the second capacity to a second settling treatment. This can alleviate battery polarization, further promote the formation of a stable CEI film and solid electrolyte interphase (SEI) film, and promote the formation of Li... + Evenly distributed.

[0045] Optionally, in some embodiments of this application, the second settling time is 5 min to 30 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0046] Optionally, in some embodiments of this application, the method further includes: charging the lithium-rich manganese battery, which has been discharged to the second voltage, to the third voltage at a constant current and constant voltage rate of the fifth, and then discharging it to the fourth voltage at a constant current rate of the sixth, using the second current as the cutoff current. The third voltage is higher than the second voltage.

[0047] It is understandable that the third voltage is higher than the second voltage, which can further activate the capacity of the lithium-rich manganese material, while the already formed CEI film can protect the structural stability of the lithium-rich manganese cathode material.

[0048] Optionally, in some embodiments of this application, the fifth charging rate is 0.1C-0.2C, for example, it can be 0.1C, 0.12C, 0.15C, 0.17C, 0.2C, etc. In this way, the current corresponding to this charging rate is moderate, which can quickly activate the lithium-rich phase of the lithium-rich manganese cathode material, while shortening the high-voltage charging time, reducing the cell gas generation time, and improving the formation efficiency.

[0049] Optionally, in some embodiments of this application, the fifth multiplier is 0.1C.

[0050] Optionally, in some embodiments of this application, the third voltage is 4.4V-4.7V, for example, it can be 4.4V, 4.5V, 4.6V, 4.7V, etc. Thus, the voltage window of the lithium-rich manganese cathode material is 2.0V-4.8V (vs Li). + / Li), 4.4V-4.7V can balance the relationship between "capacity activation" and "stability of lithium-rich manganese cathode material / electrolyte".

[0051] Optionally, in some embodiments of this application, the third voltage is 4.6V.

[0052] Optionally, in some embodiments of this application, the second current is 0.02C-0.05C. For example, it can be 0.02C, 0.03C, 0.04C, 0.05C, etc. In this way, the high-voltage charging time can be controlled, thereby shortening the reaction time between the lattice oxygen of the lithium-rich manganese cathode material and the electrolyte, reducing gas generation, and thus improving the battery's initial efficiency and cycle stability.

[0053] Optionally, in some embodiments of this application, the second current is 0.05C.

[0054] Optionally, in some embodiments of this application, the sixth multiplier is 0.1C-0.2C, for example, it can be 0.1C, 0.12C, 0.15C, 0.17C, 0.2C, etc.

[0055] Optionally, in some embodiments of this application, the sixth multiplier is 0.1C.

[0056] Optionally, in some embodiments of this application, the fourth voltage is 2.0V-2.5V. For example, it can be 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, etc.

[0057] Optionally, in some embodiments of this application, the fourth voltage is 2.0V.

[0058] Optionally, in some embodiments of this application, before the constant current discharge at the sixth rate to the fourth voltage, the process further includes: subjecting the lithium-rich manganese battery charged to the third voltage to a third settling treatment. This can alleviate battery polarization, further promote the formation of a stable CEI film and solid electrolyte interphase (SEI) film, and promote the formation of Li... + Evenly distributed.

[0059] Optionally, in some embodiments of this application, the third settling time is 5 min to 30 min.

[0060] As an example, the manufacturing process of the lithium-rich manganese battery used in this application includes: A positive electrode active material, an electronic conductive agent, and a binder are mixed with a solvent in a mass percentage ratio of (90wt.%-96.5wt.%):(1.5wt.%-4wt.%):(1wt.%-3wt.%) to obtain a positive electrode slurry. The positive electrode active material is a coated lithium-rich manganese positive electrode material (LMR material). The electronic conductive agent includes one or more of conductive carbon black (SP), vapor-grown carbon fiber (VGCF), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), graphene, and conductive graphite. The binder includes at least one of polyvinylidene fluoride and its derivatives. The solvent is N-methylpyrrolidone. The positive electrode slurry is coated onto the surface of the positive electrode current collector (aluminum foil), and then subjected to drying, rolling, and slitting steps to obtain the positive electrode sheet, wherein the areal density of the positive electrode sheet is 180 g / m³. 2 ; A negative electrode active material, an electronic conductive agent, and a binder are mixed with a solvent in a mass percentage ratio of (90wt.%-97wt.%):(0.5wt.%-3wt.%):(1.5wt.%-4wt.%) to obtain a negative electrode slurry. The negative electrode active material includes at least one of graphite, silicon oxide, silicon carbon, and their derivatives. The electronic conductive agent includes one or more of conductive carbon black, conductive graphite, carbon fiber, and carbon nanotubes. The binder includes at least one of polyvinyl alcohol, polyacrylic acid, styrene-butadiene rubber, and sodium carboxymethyl cellulose. The negative electrode slurry is coated onto the surface of the negative electrode current collector (copper foil), and then subjected to drying, rolling, and other steps to obtain the negative electrode sheet, wherein the areal density of the negative electrode sheet is 200 g / m³. 2 ; In an environment with a dew point of less than -40°C, the cells are stacked in the order of negative electrode - positive electrode - negative electrode and then injected with electrolyte.

[0061] Example 1 A method for forming a lithium-rich manganese battery, carried out at room temperature, includes: (1) First charge and discharge cycle: After the lithium-rich manganese battery is filled with liquid, it is left to stand for 24 hours, then charged at a constant current of 0.02C to 10% SOC (rated capacity), then charged at a constant current of 0.05C to 20% SOC, then charged at a constant current and constant voltage of 0.1C to 4.5V, cut off at 0.05C, then left to stand for 30 minutes, and then discharged at a constant current of 0.1C to 2.0V; (2) Second charge and discharge cycle: Charge to 4.6V with constant current and constant voltage at 0.1C, cut off at 0.05C, then let stand for 30 minutes, and then discharge to 2.0V with constant current at 0.1C.

[0062] Example 2 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the constant current charging to 10% SOC in the first charge-discharge cycle is replaced with constant current charging to 30% SOC at 0.02C, and the constant current charging to 20% SOC at 0.05C is replaced with constant current charging to 40% SOC of the rated capacity at 0.05C.

[0063] Example 3 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the constant current and constant voltage charging to 4.5V in the first cycle of charging and discharging is replaced with constant current and constant voltage charging to 4.6V in the second cycle of charging and discharging is replaced with constant current and constant voltage charging to 4.7V in the second cycle of charging and discharging.

[0064] Example 4 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the constant current charging to 10% SOC and then constant current charging to 20% SOC in the first charge-discharge cycle is replaced with constant current charging to 20% SOC at 0.02C.

[0065] Example 5 This embodiment is basically the same as embodiment 1, except that in this embodiment, the constant current charging to 10% SOC and then constant current charging to 20% SOC in the first charge-discharge cycle is replaced with constant current charging to 20% SOC at 0.05C.

[0066] Example 6 This embodiment is basically the same as Embodiment 1, except that in this embodiment, the charging process in the first charge-discharge cycle, which involves charging to 20% SOC at a constant current of 0.05C and then charging to 4.5V at a constant current and constant voltage of 0.1C and cutting off at 0.05C, is replaced with charging to 4.5V at a constant current and constant voltage of 0.1C and cutting off at 0.05C.

[0067] Comparative Example 1 A method for forming a lithium-rich manganese battery, carried out at room temperature, includes: (1) First charge and discharge cycle: After the lithium-rich manganese battery is filled with liquid, it is left to stand for 24 hours, then charged to 4.6V with constant current and constant voltage at 0.1C, with a cutoff rate of 0.05C. Then it is left to stand for 30 minutes, and then discharged to 2.0V with constant current at 0.1C. (2) Second charge and discharge cycle: Charge to 4.7V with constant current and constant voltage at 0.1C, cut-off rate 0.05C, then let stand for 30 minutes, and then discharge to 2.0V with constant current at 0.1C.

[0068] Comparative Example 2 This embodiment is basically the same as Embodiment 1, except that the formation in this embodiment is carried out at 45°C.

[0069] The lithium-rich manganese batteries used in the examples and comparative examples were prepared by the following method: 1. The coated lithium-rich manganese cathode material (LMR material), electronic conductive agent SP, and binder PVDF are mixed with NMP solvent at a mass ratio of 95wt.%:3wt.%:2wt.% to obtain a cathode slurry. The cathode slurry is then uniformly coated on the surface of aluminum foil and subjected to drying, rolling, and slitting steps to obtain a cathode sheet. 2. Graphite, electronic conductive agent SP and binder PVDF are mixed with NMP solvent at a mass ratio of 95wt.%:3wt.%:2wt.% to obtain a negative electrode slurry. The negative electrode slurry is then uniformly coated on the surface of copper foil and subjected to drying, rolling and other steps to obtain a negative electrode sheet. 3. Assemble the pouch cells in an environment with a dew point of less than -40°C, stacking them in the order of negative electrode-positive electrode-negative electrode, and injecting electrolyte.

[0070] Test example: The performance of the lithium-rich manganese soft-pack batteries obtained in the examples and comparative examples was tested, and the test results are shown in Table 1.

[0071] Gas production test method: The gas production of lithium-rich manganese batteries is tested using the water displacement method. The positive and negative tabs of the lithium-rich manganese batteries before and after formation are sealed with tape and placed in deionized water with a density of ρ. The mass of the displaced water is measured using the water displacement method. The battery volume V1 is calculated using the formula. The battery volume V2 after formation is measured. The gas production (V2-V1) is calculated by the volume difference before and after formation. The density of deionized water at 25℃ is approximately 1 g / cm³. 3 .

[0072] Initial coulombic efficiency and capacity testing method: The test was conducted using the Xinwei Battery Testing System. In a constant temperature test chamber at 25±3℃, the lithium-rich manganese battery was aged at 45℃ for 12 hours, and then tested according to the formation process. The percentage of the discharge capacity to the charge capacity in the first cycle is the initial coulombic efficiency.

[0073] Table 1 Test Results

[0074] As can be seen from Table 1: Compared with Examples 1, 2, and 3, the lithium-rich manganese battery of Example 1 has a higher initial coulombic efficiency, lower gas production, and larger discharge capacity. This is because, during the first charge cycle of Example 2, it is charged to a higher SOC (corresponding to a higher voltage) with a small current. The low rate of charge at high voltage results in a thicker CEI film, which leads to higher internal resistance and a longer formation time, resulting in more lattice oxygen removal. Consequently, the battery has a lower initial coulombic efficiency, smaller discharge capacity, and higher gas production. The lithium-rich manganese battery of Example 3 has a higher charging cutoff voltage, higher activation of the Li2MnO3 phase, and more lattice oxygen removal, which in turn leads to higher formation gas production, lower discharge capacity, and lower initial coulombic efficiency.

[0075] Compared with Examples 1, 4, and 5, the lithium-rich manganese battery of Example 1 has a higher initial coulombic efficiency, lower gas production, and larger discharge capacity. This is because, in Example 4, during the first charge cycle, a small current was used to charge to a higher SOC without gradient charging with a small current, resulting in a thicker and less stable CEI film, higher internal resistance, and a longer formation time, leading to more lattice oxygen removal and thus a lower initial coulombic efficiency, smaller discharge capacity, and higher gas production. In Example 5, during the first charge cycle, a larger current was used for the small current charging, resulting in poorer stability and uniformity of the formed CEI film, leading to more lattice oxygen removal from the lithium-rich manganese cathode material, which in turn resulted in higher formation gas production, lower discharge capacity, and lower initial coulombic efficiency.

[0076] Compared with Example 6, the lithium-rich manganese battery of Example 1 has a higher initial coulombic efficiency, lower gas production, and larger discharge capacity. This is because the low-current charging time of Example 6 is short, which results in lower stability of the formed CEI film and more lattice oxygen being removed, leading to lower initial coulombic efficiency and discharge capacity. In addition, the high-voltage charging time is long, which allows for a longer reaction time between lattice oxygen and electrolyte, thus resulting in higher gas production.

[0077] Compared to Comparative Example 1, the lithium-rich manganese battery in Comparative Example 1 exhibits lower initial coulombic efficiency, higher gas production, and smaller discharge capacity. This is because the lithium-rich manganese cathode material has poor electronic conductivity and a slow lithium-ion transport rate. Directly charging the lithium-rich manganese cathode material at 0.1C constant current and constant voltage in Comparative Example 1 cannot fully activate its capacity under high voltage. Furthermore, the resulting CEI film has lower stability, leading to even lower initial coulombic efficiency, higher gas production, and smaller discharge capacity. Therefore, this application's method of first charging with a small current and then charging with a slightly larger current can form a stable and uniform CEI film on the surface of the lithium-rich manganese cathode material. This effectively activates the lithium-rich phase and shortens the reaction time between lattice oxygen and the electrolyte, thereby reducing gas production and improving the battery's initial coulombic efficiency and discharge capacity.

[0078] Compared with Comparative Example 2, the lithium-rich manganese battery in Comparative Example 2 produced more gas. This is because the lattice oxygen in the lithium-rich manganese battery is more easily released at a high temperature of 45°C, and the electrolyte oxidation and decomposition are severe, which exacerbates gas generation.

[0079] The formation method of a lithium-rich manganese battery provided in the embodiments of this application has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this application. At the same time, those skilled in the art will make changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as limiting this application.

Claims

1. A formation method for a lithium-rich manganese battery, characterized in that, include: The lithium-rich manganese battery to be formed is charged to the first capacity at a constant current rate of the first rate, then charged to the second capacity at a constant current rate of the second rate, then charged to the first voltage at a constant current and constant voltage rate of the third rate, and then discharged to the second voltage at a constant current rate of the fourth rate. Wherein, the first multiplier and the second multiplier are less than the third multiplier, the first capacity is less than the second capacity, and the second capacity is less than 100% SOC.

2. The formation method of the lithium-rich manganese battery according to claim 1, characterized in that, The first multiplier is less than the second multiplier.

3. The formation method of the lithium-rich manganese battery according to claim 1, characterized in that, The first expansion rate is 0.01C-0.05C; and / or The second multiplier is 0.02C-0.08C; and / or The third multiplier is 0.05C-0.1C; and / or The fourth multiple is 0.05C-0.1C.

4. The formation method of the lithium-rich manganese battery according to claim 1, characterized in that, The first capacity is 5% SOC-20% SOC; and / or The second capacity is 20%SOC-40%SOC.

5. The formation method of the lithium-rich manganese battery according to claim 1, characterized in that, The first voltage is 4.4V-4.7V; and / or The first current is 0.02C-0.05C; and / or The second voltage is 2.0V-2.5V.

6. The formation method of the lithium-rich manganese battery according to claim 1, characterized in that, Also includes: The lithium-rich manganese battery, which has been discharged to the second voltage, is charged to the third voltage at a constant current and constant voltage rate of the fifth rate, and then discharged to the fourth voltage at a constant current rate of the sixth rate, with the second current as the cutoff current. The third voltage is higher than the second voltage.

7. The formation method of the lithium-rich manganese battery according to claim 6, characterized in that, The fifth multiplier is 0.1C-0.2C; and / or The sixth multiplier is 0.1C-0.2C.

8. The formation method of the lithium-rich manganese battery according to claim 6, characterized in that, The third voltage is 4.4V-4.7V; and / or The second current is 0.02C-0.05C; and / or The fourth voltage is 2.0V-2.5V.

9. The formation method of the lithium-rich manganese battery according to claim 6, characterized in that, Before charging to the first capacity at a first rate constant current, the process further includes: subjecting the lithium-rich manganese battery to be formed to a first settling treatment; and / or Before discharging to the second voltage at a constant current rate of the fourth multiple, the method further includes: subjecting the lithium-rich manganese battery, charged to the second capacity, to a second settling treatment; and / or Before discharging to the fourth voltage at a constant current rate of the sixth multiple, the process further includes: subjecting the lithium-rich manganese battery, which has been charged to the third voltage, to a third settling treatment.

10. The formation method of the lithium-rich manganese battery according to claim 9, characterized in that, The first settling time is 12h-48h; and / or The second settling time is 5 min-30 min; and / or The third settling time is 5-30 minutes.

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