Battery formation method, battery preparation method and battery

Abstract

The invention relates to the technical field of battery preparation, in particular to a battery formation method, a battery preparation method, a battery and electric equipment. The battery formation method provided by the invention comprises the following steps: a first stage: charging a battery cell infiltrated with an electrolyte at a constant current I1 until the negative electrode potential of the battery cell reaches VN, and VN is less than or equal to 0.5 V; and in the second stage, the battery cell is continuously charged with the current smaller than I1 until the battery cell reaches the charge state of 20-100%. According to the method, the formation time is shortened while the film forming quality of the SEI film is guaranteed, and the method has important significance on improving the production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of battery preparation, and particularly relates to a battery formation method, a battery preparation method, and a battery. Background Art

[0002] After a battery is manufactured, the process of activating the positive and negative electrode materials inside it through a certain charge-discharge method to improve the charge-discharge performance, self-discharge, storage, and other comprehensive performances of the battery is called formation. Formation is a very complex process and an important link in the battery design and production process. This process can activate the active substances in the battery and make the battery active. At the same time, side reactions occur in the electrolyte, and a solid electrolyte interface (SEI) film is formed on the negative electrode side of the battery. This layer of film can prevent further occurrence of side reactions, thereby reducing the loss of active substances in the battery. The quality of the SEI has a great impact on the cycle life, initial capacity loss, rate performance, etc. of the battery.

[0003] Currently, for the formation charging process of batteries, most of them first use small-current charging for "pre-formation" to activate the battery cells, and then perform secondary charging. This formation method takes a long time and cannot well adapt to the delivery cycle of the batteries. Summary of the Invention

[0004] The present invention provides a battery formation method, which is of great significance for improving production efficiency while ensuring the film-forming quality of the SEI film and shortening the formation time.

[0005] The present invention achieves the above technical objectives through the following technical solutions:

[0006] A battery formation method, comprising:

[0007] The first stage: charging the battery cell impregnated with the electrolyte at a constant current of I1 until the negative electrode potential of the battery cell reaches V N , V N ≤0.5V;

[0008] The second stage: continuing to charge the battery cell with a current smaller than I1 until the battery cell reaches a state of charge of 15-100%.

[0009] For the battery formation method described above, the current I1 satisfies 0.05C ≤ I1 ≤ 1C.

[0010] For the battery formation method described above, the second stage is: continuing to charge the battery cell with a current smaller than I1 until the battery cell reaches a state of charge of 15-40%.

[0011] For the battery formation method described above, the ambient temperature in the first stage and the second stage is 20-60°C, and the ambient dew point temperature ≤ -35°C.

[0012] The battery formation method described above further includes the step of applying a pressure F to the outer surface of the battery cell during the charging process.

[0013] The battery formation method described above includes the step of performing negative pressure regulation inside the battery cell during the charging process.

[0014] In the battery formation method described above, the pressure F is 0.1 to 2 Mpa.

[0015] In the battery formation method described above, the pressure during the negative pressure regulation is -15 Kpa to -90 Kpa.

[0016] In the battery formation method described above, the battery cell is a lithium-ion battery cell.

[0017] The present invention also provides a method for manufacturing a battery, including the process of forming a SEI film by using the above battery formation method.

[0018] The method for manufacturing a battery described above further includes the step of performing an aging treatment after forming the SEI film by formation; the aging treatment temperature is 20 to 60 °C, and the aging time is 5 to 36 h.

[0019] The present invention also provides a battery manufactured by the above manufacturing method.

[0020] The present invention regulates the negative electrode potential in the first stage of the formation process and performs recharging with a current smaller than that in the first stage. This method is beneficial for shortening the formation time, improving production efficiency, and the quality of the formed SEI film is stable. Detailed Embodiments

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0022] Based on the problem that the existing method for forming a SEI film takes a long time, the present invention provides a formation method for efficiently forming a stable SEI film. Under the condition of charging to the same state of charge, this method is beneficial for shortening the time of the entire formation process, and after testing, the battery processed by this formation method can still maintain good battery performance. The formation method for efficiently forming a stable SEI film provided by the present invention includes:

[0023] The first stage: The battery cell after being infiltrated with the electrolyte is charged at a constant current of I1 until the negative electrode potential of the battery cell reaches V N , V N ≤0.5V;

[0024] The second stage: The battery cell is continuously charged with a current smaller than I1 until the battery cell reaches a state of charge of 15% - 100%.

[0025] By regulating the negative electrode potential in the first stage of the formation process and recharging with a current smaller than that in the first stage, the method of the present invention is beneficial to shortening the formation time, improving the production efficiency, and forming a stable SEI film with good quality.

[0026] The negative electrode potential described in the present invention is the negative electrode potential commonly understood in the art, that is, the potential difference of the negative electrode in the circuit relative to the reference point. Taking a lithium-ion battery as an example, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, usually denoted as vs Li + / Li.

[0027] In the present invention, there is no special limitation on the current I1. The larger the current I1, the shorter the formation time. Therefore, the current I1 is usually controlled to be ≥0.05C. In practical applications, the formation current is usually not greater than 1C. Therefore, in this application, the current I1 usually adopts a range of 0.05C ≤ I1 ≤ 1C. For example, it can be 0.05C, 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, 1.0C and the range between any two of the above values.

[0028] In the present invention, in the second stage, the battery cell is charged until the battery cell reaches a state of charge of 15% - 100%, such as 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% and the range between any two of the above values. It can be understood that the higher the state of charge of the battery cell in the second stage of charging, the longer the time-consuming. In order to reduce the cost and better shorten the formation time, in the second stage, it is preferably charged until the battery cell reaches a state of charge of 15% - 40%.

[0029] The state of charge (abbreviated as SOC) is a parameter that describes the relationship between the remaining battery power and its fully charged state, and it reflects the proportion of the current stored battery power in its total capacity. When the battery cell reaches a state of charge of 15% - 40%, that is, the current stored battery power in the battery cell is between 15% and 40% of its total capacity.

[0030] The key of the present invention lies in controlling V during the first charging N≤0.5V, in the second stage, charging can be carried out with a current smaller than that in the first stage. There is no special limitation on the charging method in the second stage, and it can adopt a one-time charging method or a segmented charging method.

[0031] Exemplarily, the second stage can merely be: continuously charging the battery cell at a constant current I2 until the battery cell reaches a state of charge of 15-40%, where I1 > I2. It can also be: first continuously charging the battery cell at a constant current I2 until the battery cell reaches a state of charge of 10-23%, and then continuously charging the battery cell at a constant current I3 until the battery cell reaches a state of charge of 25-40%; where I1 > I2, I1 > I3 and I2 ≠ I ３ .

[0032] For the formation method of the present invention, there is no special limitation on the ambient temperature, and it can be carried out in a normal temperature and pressure environment or in a high-temperature environment. Preferably, the temperature is controlled to be 20-60°C, such as 20°C, 30°C, 40°C, 50°C, 60°C and the range between any two of the above values. When the formation is carried out at a high temperature, the specific operation can be: transferring the battery cell after being infiltrated with the electrolyte into the formation equipment, and then adjusting the temperature of the formation equipment to the set temperature.

[0033] In actual production, the water content in the battery needs to be strictly controlled because water will chemically react with the lithium salt in the electrolyte to generate hydrofluoric acid, corroding the metal parts inside the battery; water will also cause precipitation on the surface of the SEI film, destroying the compactness and uniformity of the film, thereby increasing the internal resistance of the battery, affecting the use efficiency of the battery, reducing the discharge capacity, and shortening the cycle life. Therefore, in order to avoid introducing water during the formation process, the water content in the environment is usually restricted. The present invention can control the moisture in the battery by controlling the ambient dew point temperature ≤ -35°C.

[0034] Generally, gas generation will also occur during the formation process. In order to facilitate the discharge of gas, in some specific embodiments of the present invention, it further includes the step of applying a pressure F to two opposite surfaces of the battery cell during the formation process. Exemplarily, the magnitude of the pressure F is 0.1-2 Mpa, such as it can be 0.1 Mpa, 0.5 Mpa, 1 Mpa, 1.5 Mpa, 2 Mpa and the range between any two of the above values.

[0035] In some other specific embodiments of the present invention, in order to more facilitate the discharge of gas, it further includes the step of regulating the negative pressure inside the battery cell during the formation process. Exemplarily, the negative pressure inside the battery cell is regulated through the liquid injection port, and the pressure is -15Kpa to -90Kpa, such as -15Kpa, -20Kpa, -30Kpa, -40Kpa, -50Kpa, -60Kpa, -70Kpa, -80Kpa, -90Kpa, and the ranges between any two of the above values.

[0036] In some specific embodiments of the present invention, the battery cell is a lithium-ion battery cell, and the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode.

[0037] There is no special limitation on the electrolyte used in the formation reaction of the present invention. In some specific embodiments of the present invention, the lithium salt in the electrolyte is one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(fluorosulfonyl)imide (LIFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the solvent is one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), vinylene carbonate (VC), ethylene glycol n-propyl ether (EP), vinylene sulfate (DTD), trimethylolpropane (TMP), triethyl phosphate (TEP), fluoroethylene carbonate (FEC), 1,3-dioxolane (DOL), dimethyl ether (DME), and hydrofluoroether (HFE). The electrolyte concentration (i.e., the lithium salt concentration) is 0.8 to 3mol / L, and the water content is ≤20ppm.

[0038] The present invention also provides a method for preparing a lithium-ion battery, including the process of forming an SEI film by using the above-mentioned formation method.

[0039] After the formation is completed, it usually further includes the step of aging the formed SEI film after the formation. In the present invention, there is no specific limitation on the method of forming the SEI film during the formation. Exemplarily, the following method can be used for aging treatment. The aging treatment temperature is 20 to 60°C, such as 20°C, 30°C, 40°C, 50°C, 60°C, and the ranges between any two of the above values. The aging time is 5 to 36h, such as 5h, 10h, 15h, 20h, 25h, 30h, 35h, 36h, and the ranges between any two of the above values.

[0040] In some specific embodiments, a lithium-ion battery can be prepared by the following method: The positive and negative electrode materials are homogenized, coated, baked, rolled, and then cut into positive and negative electrode sheets of the required specifications. The positive and negative electrode sheets and the separator are stacked or wound. The positive electrode sheet and the negative electrode sheet are separated by the separator, and the electrode tabs are welded to form an electrode core. The electrode core is enclosed in a housing, and after the cover plate is welded, it is baked, filled with electrolyte for the first time and soaked, and then formation treatment is carried out. After the formation, the electrode core is aged and then filled with electrolyte for the second time, and then the filling port is sealed. The baking temperature is 65~100 °C, such as 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, and the range between any two of the above values. The ambient temperature during soaking can be controlled at 20~60 °C, such as 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, and the range between any two of the above values.

[0041] The present invention also provides a lithium-ion battery prepared by the above method.

[0042] The present invention also provides an electronic device including the above lithium-ion battery. The electronic device can be a smart phone, a laptop computer, a tablet computer, a smart watch / bracelet, a digital camera, a floor sweeping robot, a power tool, a drone, a portable detection instrument, etc.

[0043] Example 1

[0044] This example provides a formation process and preparation of a lithium-ion battery. The rated capacity of the lithium-ion battery is 52 Ah, and the steps are as follows:

[0045] (1) Provide the battery to be formed

[0046] The positive and negative electrode materials are homogenized, coated, baked, rolled, and then cut into positive and negative electrode sheets of the required specifications. Among them, the positive electrode slurry is: active material lithium iron phosphate, binder polyvinylidene fluoride (PVDF), conductive agent acetylene black, and the mass ratio of the three is 95:2.5:2.5. The solvent is N-methylpyrrolidone, and the positive electrode current collector is aluminum foil. The negative electrode slurry is active material graphite, binder polyvinylidene fluoride, conductive agent acetylene black, and the mass ratio of the three is 95:2:3. The solvent is deionized water, and the negative electrode sheet is copper foil.

[0047] The prepared positive electrode sheet, negative electrode sheet and separator are stacked or wound. The positive electrode sheet and the negative electrode sheet are separated by the separator, and the electrode tabs are welded to form an electrode core. Among them, the separator is polypropylene (PP).

[0048] Wrap the battery cell in the outer shell, bake the battery with the cover at 95 °C for 14 h, then add the electrolyte and soak it at 25 °C for 40 h, and send it into the formation cabinet for formation. Among them, the electrolyte used during liquid injection includes the lithium salt LiPF6 and the solvent ethylene carbonate (EC). The concentration of the lithium salt is 1.2 mol / L, and the water content in the electrolyte is ≤20 ppm.

[0049] (2) Formation process

[0050] Control the ambient temperature at 25 °C and the dew point temperature at -35 °C. Apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell during the formation process. At the same time, conduct negative pressure regulation on the inside of the battery cell through the liquid injection port of the battery cell, and maintain the negative pressure at -20 Kpa.

[0051] First stage: Charge the lithium-ion battery at a constant current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.5 V. Among them, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode. This value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0052] Second stage: Continue to charge the lithium battery cell that has completed the first charging operation at a constant current I2 for the second time until the battery SOC reaches 20% (i.e., the battery cell reaches a 20% state of charge). Continue to charge the lithium battery cell that has completed the second charging operation at a constant current I3 for the third time until the battery SOC reaches 25% (i.e., the battery cell reaches a 25% state of charge).

[0053] Among them, I1 is the current at a rate of 0.5C, I2 is the current at a rate of 0.3C, and I3 is the current at a rate of 0.1C.

[0054] (3) Secondary liquid injection and sealing

[0055] After aging the formed battery cell at 40 °C for 20 h, conduct secondary liquid injection, and then seal the liquid injection port to obtain the lithium-ion battery.

[0056] Example 2

[0057] This example provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Example 1 lies in the different formation processes, and the specific formation process is as follows:

[0058] Control the ambient temperature at 25 °C and the dew point temperature at -35 °C. Apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell during the formation process. At the same time, conduct negative pressure regulation on the inside of the battery cell through the liquid injection port of the battery cell, and maintain the negative pressure at -20 Kpa.

[0059] The first stage: The lithium-ion battery is subjected to the first constant-current charging at a current of I1 until the negative electrode potential (vs Li + / Li) reaches 0.4V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0060] The second stage: The lithium-ion battery cell that has completed the first charging operation is continuously subjected to the second constant-current charging at a current of I2 until the battery SOC reaches 20%, and the lithium-ion battery cell that has completed the second charging operation is continuously subjected to the third constant-current charging at a current of I3 until the battery SOC reaches 25%.

[0061] Among them, I1 is the current at a rate of 0.5C, I2 is the current at a rate of 0.3C, and I3 is the current at a rate of 0.1C.

[0062] Example 3

[0063] This example provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52Ah. The difference from Example 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0064] Control the ambient temperature to 25°C and the dew point temperature to -35°C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, perform negative pressure regulation on the inside of the cell through the liquid injection port of the cell to maintain the negative pressure at -20 Kpa.

[0065] The first stage: The lithium-ion battery is subjected to the first constant-current charging at a current of I1 until the negative electrode potential (vs Li + / Li) reaches 0.3V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0066] The second stage: The lithium-ion battery cell that has completed the first charging operation is continuously subjected to the second constant-current charging at a current of I2 until the battery SOC reaches 20%, and the lithium-ion battery cell that has completed the second charging operation is continuously subjected to the third constant-current charging at a current of I3 until the battery SOC reaches 25%.

[0067] Among them, I1 is the current at a rate of 0.5C, I2 is the current at a rate of 0.3C, and I3 is the current at a rate of 0.1C.

[0068] Example 4

[0069] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Embodiment 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0070] Control the ambient temperature at 25 °C and the dew point temperature at -35 °C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, perform negative pressure regulation on the inside of the cell through the liquid injection port of the cell, maintaining the negative pressure at -20 Kpa.

[0071] First stage: Charge the lithium-ion battery at a constant current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.2 V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0072] Second stage: Continue to charge the lithium battery cell that has completed the first charging operation at a constant current I2 for the second time until the state of charge (SOC) of the battery reaches 20%. Then continue to charge the lithium battery cell that has completed the second charging operation at a constant current I3 for the third time until the SOC of the battery reaches 25%.

[0073] Among them, I1 is the current at a rate of 0.5C, I2 is the current at a rate of 0.3C, and I3 is the current at a rate of 0.1C.

[0074] Embodiment 5

[0075] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Embodiment 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0076] Control the ambient temperature at 25 °C and the dew point temperature at -35 °C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, perform negative pressure regulation on the inside of the cell through the liquid injection port of the cell, maintaining the negative pressure at -20 Kpa.

[0077] First stage: Charge the lithium-ion battery at a constant current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.4 V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0078] The second stage: continue to charge the lithium battery cell that has completed the first charging operation with a current I2 for the second constant current charging until the battery SOC reaches 20%, and continue to charge the lithium battery cell that has completed the second charging operation with a current I3 for the third constant current charging until the battery SOC reaches 25%.

[0079] Among them, I1 is a current at a rate of 0.4C, I2 is a current at a rate of 0.3C, and I3 is a current at a rate of 0.1C.

[0080] Example 6

[0081] This example provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52Ah. The difference from Example 1 lies in the different formation processes, and the specific formation process is as follows:

[0082] Control the ambient temperature to 25°C and the dew point temperature to -35°C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, perform negative pressure regulation on the inside of the cell through the cell liquid injection port to maintain the negative pressure at -20 Kpa.

[0083] The first stage: charge the lithium-ion battery with a current I1 for the first constant current charging until the negative electrode potential (vs Li + / Li) reaches 0.4V. Among them, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0084] The second stage: continue to charge the lithium battery cell that has completed the first charging operation with a current I2 for the second constant current charging until the battery SOC reaches 20%, and continue to charge the lithium battery cell that has completed the second charging operation with a current I3 for the third constant current charging until the battery SOC reaches 25%.

[0085] Among them, I1 is a current at a rate of 0.3C, I2 is a current at a rate of 0.25C, and I3 is a current at a rate of 0.1C.

[0086] Example 7

[0087] This example provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52Ah. The difference from Example 1 lies in the different formation processes, and the specific formation process is as follows:

[0088] Control the ambient temperature to 25°C and the dew point temperature to -35°C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, perform negative pressure regulation on the inside of the cell through the cell liquid injection port to maintain the negative pressure at -20 Kpa.

[0089] The first stage: The lithium-ion battery is subjected to the first constant-current charge at a current I1 until the negative electrode potential (vs Li + / Li) reaches 0.3 V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive-negative, positive-reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0090] The second stage: The lithium-ion battery cell that has completed the first charging operation is continued to be charged at a constant current I2 until the battery SOC reaches 20%, and the lithium-ion battery cell that has completed the second charging operation is continued to be charged at a constant current I3 until the battery SOC reaches 25%.

[0091] Among them, I1 is a current at a rate of 0.3C, I2 is a current at a rate of 0.25C, and I3 is a current at a rate of 0.1C.

[0092] Example 8

[0093] This example provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Example 1 lies in the different formation processes, and the specific formation process is as follows:

[0094] Control the ambient temperature to 25°C and the dew point temperature to -35°C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, conduct negative pressure regulation inside the cell through the liquid injection port of the cell to maintain the negative pressure at -20 Kpa.

[0095] The first stage: The lithium-ion battery is subjected to the first constant-current charge at a current I1 until the negative electrode potential (vs Li + / Li) reaches 0.3 V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive-negative, positive-reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0096] The second stage: The lithium-ion battery cell that has completed the first charging operation is continued to be charged at a constant current I2 until the battery SOC reaches 20%, and the lithium-ion battery cell that has completed the second charging operation is continued to be charged at a constant current I3 until the battery SOC reaches 25%.

[0097] Among them, I1 is a current at a rate of 0.4C, I2 is a current at a rate of 0.15C, and I3 is a current at a rate of 0.25C.

[0098] Example 9

[0099] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Embodiment 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0100] Control the ambient temperature at 40 °C and the dew point temperature at -40 °C. During the formation process, apply a pressure of 2 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, conduct negative pressure regulation inside the cell through the cell liquid injection port to maintain the negative pressure at -15 Kpa.

[0101] First stage: Charge the lithium-ion battery at a constant current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.4 V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0102] Second stage: Continue to charge the lithium battery cell that has completed the first charging operation at a constant current I2 until the SOC of the battery reaches 20%, and then continue to charge the lithium battery cell that has completed the second charging operation at a constant current I3 until the SOC of the battery reaches 40%.

[0103] Among them, I1 is a current at a rate of 0.5 C, I2 is a current at a rate of 0.3 C, and I3 is a current at a rate of 0.1 C.

[0104] Embodiment 10

[0105] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Embodiment 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0106] Control the ambient temperature at 25 °C and the dew point temperature at -35 °C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, conduct negative pressure regulation inside the cell through the cell liquid injection port to maintain the negative pressure at -20 Kpa.

[0107] First stage: Charge the lithium-ion battery at a constant current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.4 V. Here, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode, and this value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0108] Second stage: Continue to charge the lithium battery cell that has completed the first charging operation at a constant current I2 until the SOC of the battery reaches 25%.

[0109] Among them, I1 is the current at 0.5C rate, and I2 is the current at 0.3C rate.

[0110] Comparative Example 1

[0111] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Example 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0112] Control the ambient temperature at 25°C and the dew point temperature at -40°C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, conduct negative pressure regulation on the inside of the cell through the liquid injection port of the cell, maintaining the negative pressure at -20 Kpa.

[0113] First stage: Charge the lithium-ion battery at a constant current with current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.5 V. Among them, the negative electrode potential refers to the potential of the negative electrode relative to the Li + / Li reference electrode. This value can be obtained by recording the positive and negative, positive reference, and reference potentials during the charging process of the three-electrode battery with a multi-channel recorder.

[0114] Second stage: Continue to charge the lithium battery cell that has completed the first charging operation at a constant current with current I2 until the battery SOC reaches 20%. Continue to charge the lithium battery cell that has completed the second charging operation at a constant current with current I3 until the battery SOC reaches 25%.

[0115] Among them, I1 is the current at 0.02C rate, I2 is the current at 0.1C rate, and I3 is the current at 0.2C rate.

[0116] Comparative Example 2

[0117] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52 Ah. The difference from Example 1 lies in the different formation procedures, and the specific formation procedures are as follows:

[0118] Control the ambient temperature at 40°C and the dew point temperature at -40°C. During the formation process, apply a pressure of 1 Mpa to two opposite surfaces of the lithium-ion battery cell, and at the same time, conduct negative pressure regulation on the inside of the cell through the liquid injection port of the cell, maintaining the negative pressure at -20 Kpa.

[0119] First stage: Charge the lithium-ion battery at a constant current with current I1 for the first time until the negative electrode potential (vs Li + / Li) reaches 0.4 V. Among them, the negative electrode potential refers to the potential of the negative electrode relative to the Li +The potential of the / Li reference electrode, which can be obtained by a multi-channel recorder recording the positive-negative, positive-reference, and reference potentials during the charging process of the three-electrode battery.

[0120] The second stage: The lithium-ion battery cell that has completed the first charging operation is continued to be charged at a constant current I2 for the second time until the battery SOC reaches 20%, and the lithium-ion battery cell that has completed the second charging operation is continued to be charged at a constant current I3 for the third time until the battery SOC reaches 25%.

[0121] Among them, I1 is a current at a rate of 0.02C, I2 is a current at a rate of 0.1C, and I3 is a current at a rate of 0.2C.

[0122] Comparative Example 3

[0123] This embodiment provides a formation process and preparation of a lithium-ion battery. The rated capacity of this lithium-ion battery is 52Ah. The difference from Example 1 is that the formation process uses a conventional process of small current first and then large current. The specific formation process is as follows:

[0124] The first stage: The lithium-ion battery is charged at a constant current I1 for the first time until the battery SOC reaches 5%.

[0125] The second stage: The lithium-ion battery cell that has completed the first charging operation is continued to be charged at a constant current I2 for the second time until the battery SOC reaches 10%.

[0126] The third stage: The lithium-ion battery cell that has completed the second charging operation is continued to be charged at a constant current I3 for the third time until the battery SOC reaches 20%.

[0127] The fourth stage: The lithium-ion battery cell that has completed the third charging operation is continued to be charged at a constant current I4 for the fourth time until the battery SOC reaches 25%.

[0128] Among them, I1 is a current at a rate of 0.02C, I2 is a current at a rate of 0.05C, I3 is 0.1C, and I4 is a current at a rate of 0.2C.

[0129] Performance test:

[0130] The lithium-ion batteries prepared in the above examples and comparative examples were tested to obtain their average first Coulombic efficiency, average capacity retention rate, and average capacity recovery rate. The test methods are as follows, and the test results are shown in Table 1.

[0131] Average initial Coulombic efficiency: After standing for 4 h at 25°C for various batteries prepared by the methods in the above-mentioned examples and comparative examples respectively, the first charge-discharge capacity test was then carried out. The test conditions were: charging at 0.1C to 3.65V, standing for 3 min, and then discharging at 0.1C to 2.5V. The charge-discharge curves were obtained, and the first-week charging gram capacity C0 and the first-week discharging gram capacity D0 at 3.65V were respectively recorded. The first Coulombic efficiency was calculated according to D0 / C0, and the average value was calculated by taking 20 samples from each type of battery (i.e., the average initial Coulombic efficiency was obtained).

[0132] Average capacity retention rate: At 25°C, the battery was charged at a constant current of 0.1C to 3.65V, stood for 3 min, and then discharged at a constant current of 0.1C to 2.5V. The initial capacity was recorded as C0. Then, it was cycled 100 times, and its current capacity was measured. By calculating the ratio of the capacity after 100 cycles to the average capacity of the first 3 cycles, the capacity retention rate was obtained. The average value was calculated by taking 20 samples from each type of battery, that is, the average capacity retention rate was obtained.

[0133] Average capacity recovery rate: At 25°C, the battery was charged at a constant current of 0.1C to 3.65V, stood for 3 min, and then discharged at a constant current of 0.1C to 2.5V. The initial capacity was recorded as C1, and 3 cycles were carried out, and the average value was taken to eliminate the first-cycle error. Then, the battery was charged to 50% SOC, placed in a constant temperature condition of 55°C and stored for 7 days. After the storage was completed, it was immediately transferred to an environment of 25°C and stood for 12 hours, and then a complete charge-discharge cycle was performed. The maximum value was taken after repeating 3 times, that is, the recovered capacity C2 was obtained. The ratio of C2 to C1 was calculated, that is, the average capacity recovery rate was obtained.

[0134] Table 1

[0135]

[0136] As can be seen from Table 1, the first Coulombic efficiency, capacity retention rate, and capacity recovery rate after being placed at 55°C for 7 days of the batteries prepared by the formation process described in the examples of the present invention are all comparable to those of the batteries prepared by the existing conventional method in Comparative Example 3. However, under the condition of charging to the same battery SOC, the formation time in the examples of the present invention is significantly shorter than that in the prior art. Although the formation time in the comparative example is also shorter than that in the prior art, the comprehensive performance of the batteries prepared by it is generally inferior to those of the batteries prepared in the examples and Comparative Example 3, indicating that the method provided by the present invention can shorten the formation time while ensuring the film-forming quality of the SEI film.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery formation method, characterized in that, Comprising: The first stage: The battery cell after being infiltrated with the electrolyte is charged at a constant current I1 until the negative electrode potential of the battery cell reaches V N , V N ≤0.5V; The second stage: continuing to charge the battery cell with a current less than I1 until the battery cell reaches a state of charge of 15-100%.

2. The battery formation method according to claim 1, wherein The current I1 satisfies 0.05C ≤ I1 ≤ 1C.

3. The battery formation method according to claim 1 or 2, characterized in that, The second stage is: continuing to charge the battery cell with a current less than I1 until the battery cell reaches a state of charge of 15-40%.

4. The battery formation method according to any one of claims 1 to 3, characterized in that, The ambient temperature in the first stage and the second stage is 20-60°C, and the ambient dew point temperature ≤ -35°C.

5. The battery formation method according to any one of claims 1 to 4, characterized in that It also includes the step of applying a pressure F to the outer surface of the battery cell during charging; and / or The step of regulating the negative pressure inside the battery cell during charging.

6. The battery formation method according to claim 5, characterized in that, The pressure F is 0.1-2 Mpa; and / or The pressure during the negative pressure regulation is -15 Kpa to -90 Kpa.

7. The battery formation method according to any one of claims 1 to 6, characterized in that, The battery cell is a lithium-ion battery cell.

8. A method for preparing a battery, characterized in that, It includes the process of forming a SEI film by using the battery formation method according to any one of claims 1-7.

9. The method for preparing a battery according to claim 8, wherein It also includes the step of aging treatment after forming the SEI film by formation; the aging treatment temperature is 20-60°C, and the aging time is 5-36 h.

10. A battery, characterized in that, Prepared by the preparation method according to claim 8 or 9.

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