Battery formation method, battery and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a battery formation method, a battery and a power utilization device. The battery formation method comprises the following steps: a first charging stage: controlling to apply a first surface pressure to a battery, and charging the battery to a first charging state with a constant current, the first charging state being less than 5% SOC; in the second charging stage, a second surface pressure is controlled to be applied to the battery, the battery is charged to a second charging state in a constant current mode, the second charging state is 5%-80% SOC, the second surface pressure is larger than the first surface pressure, and the second surface pressure is smaller than or equal to 0.2 MPa; and in the third charging stage, a third surface voltage is controlled to be applied to the battery, the battery is charged to a third charging state in a constant current mode, the third charging state is larger than 80% SOC, and the third surface voltage is smaller than the second surface voltage. And the surface pressure in the first charging stage, the second charging stage and the third charging stage exerts a cooperative regulation effect, so that the interface performance and the cycle performance of the battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery formation method, a battery, and an electrical device. Background Technology

[0002] After the battery is manufactured, a solid electrolyte interface (SEI) film needs to be formed through a chemical process.

[0003] In traditional technology, external surface pressure is applied to the battery during formation to improve the wettability of the electrolyte and suppress electrode expansion, thereby enhancing the stability and density of the SEI film.

[0004] However, in order to suppress expansion to the greatest extent, traditional formation processes often tend to apply high surface pressure (≥0.4 MPa). Excessive pressure can prevent gas from being discharged from the cell in time, leading to gas accumulation. This may exacerbate bulging and gas expansion, reduce the utilization rate of active materials, disrupt the formation kinetics of the SEI film, resulting in uneven composition and loose structure, which in turn increases interfacial impedance and affects battery performance. Summary of the Invention

[0005] Based on this, this application provides a battery formation method, a battery, and an electrical device. By controlling the surface pressure during the battery formation process, the wettability of the electrolyte can be improved, and the expansion of the electrode sheet can be suppressed. This improves the quality of the SEI film while reducing damage to the electrode structure, thereby improving the interface performance and cycle performance of the battery.

[0006] A first aspect of this application provides a battery formation method, comprising the following steps: a first charging stage: controlling the application of a first surface pressure to the battery and charging the battery with a constant current to a first charging state, wherein the first charging state is less than 5% SOC, and wherein the first surface pressure is greater than or equal to 0.01 MPa; a second charging stage: controlling the application of a second surface pressure to the battery and charging the battery with a constant current to a second charging state, wherein the second charging state is 5% to 80% SOC, wherein the second surface pressure is greater than the first surface pressure and less than or equal to 0.2 MPa; and a third charging stage: controlling the application of a third surface pressure to the battery and charging the battery with a constant current to a third charging state, wherein the third charging state is greater than 80% SOC, wherein the third surface pressure is less than the second surface pressure.

[0007] In some embodiments, the battery formation method satisfies at least one of the following conditions: (1) a first surface pressure of 0.01 MPa to 0.1 MPa; (2) a second surface pressure of 0.1 MPa to 0.2 MPa; (3) a third surface pressure of 0.05 MPa to 0.15 MPa.

[0008] In some embodiments, the first charging stage satisfies at least one of the following conditions: (1) the temperature of the first charging stage is 25°C to 30°C; (2) the constant current charging current in the first charging stage is 0.05C to 0.1C; (3) the first charging stage is charged to a first voltage, which is 0.1V to 3V.

[0009] In some embodiments, the second charging stage satisfies at least one of the following conditions: (1) the temperature of the second charging stage is 55°C to 65°C; (2) the constant current charging current in the second charging stage is 0.1C to 0.2C; (3) the second charging stage charges to a second voltage, which is 3.1V to 3.4V.

[0010] In some embodiments, the third charging stage satisfies at least one of the following conditions: (1) the temperature of the third charging stage is 40°C to 50°C; (2) the constant current charging current in the third charging stage is 0.2C to 0.33C; (3) the third charging stage is charged to a third voltage, which is 3.5V to 4.3V.

[0011] In some implementations, when the third charging stage reaches 100% SOC, the third voltage is the cutoff voltage. The third charging stage specifically includes the following steps: charging the battery with a constant current to the cutoff voltage, and then charging with a constant voltage to the cutoff current; wherein the cutoff voltage is 4V~4.3V, and the cutoff current is less than or equal to 0.05C.

[0012] In some embodiments, the battery formation method further includes the following steps: discharge stage: controlling the application of a third surface pressure to the battery, and discharging the battery at a constant current to a fourth voltage before releasing the pressure.

[0013] In some embodiments, the discharge phase satisfies at least one of the following conditions: (1) the current of the constant current discharge in the discharge phase is 0.2C to 0.5C; (2) the fourth voltage in the discharge phase is 2V to 3V.

[0014] A second aspect of this application provides a battery obtained by forming the battery using the battery formation method described in the first aspect.

[0015] A third aspect of this application provides an electrical device that includes the battery provided in the second aspect above.

[0016] Compared with traditional technologies, this application has at least the following beneficial effects:

[0017] The battery formation method provided in some embodiments of this application, through coordinated control of the surface pressure in the first, second, and third charging stages, achieves initial uniform wetting of the electrolyte in the first charging stage, during which the battery is in a pre-charged state, by applying a relatively low first surface pressure. In the second charging stage, the battery is in the main formation state, and a second surface pressure greater than the first surface pressure is applied to the battery. This promotes close contact between the electrodes, inhibits electrode expansion, and also promotes more thorough wetting of the electrolyte, thereby providing favorable conditions for the formation of an inorganic dense inner SEI film mainly composed of Li2CO3 and LiF. Ultimately, this inhibits the intercalation of solvent molecules and reduces the consumption of active lithium. Furthermore, the second surface pressure is controlled at 0.2. Below MPa, it can prevent damage to the electrode structure from high surface pressure, improve the utilization rate of active materials, and thus improve the interface stability and cycle performance of the battery. In the third charging stage after formation, the battery is in a stress release state. Applying a third surface pressure to the battery, which is less than the second surface pressure, releases the internal stress accumulated in the main formation stage. On the one hand, it can reduce the impact on the electrode structure during pressure relief and improve the interface performance of the battery. On the other hand, it can reduce the rebound amplitude during pressure relief, reduce the expansion rate of the battery, reduce the electrode spacing, improve the lithium-ion transport rate, and promote a more uniform distribution of the SEI film. This results in minimal lithium consumption during high-temperature storage, improving residual capacity and recovery capacity, and thus improving the cycle performance of the battery.

[0018] In summary, the battery formation method provided in some embodiments of this application has a synergistic regulatory effect on the surface pressure in the first charging stage, the second charging stage, and the third charging stage, which improves the wettability of the electrolyte and inhibits electrode expansion. This improves the quality of the SEI film while reducing damage to the electrode structure, thereby improving the interface performance and cycle performance of the battery. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a battery formation method according to one embodiment of this application. Detailed Implementation

[0020] Reference will now be made to detailed embodiments of this application, one or more of which are described below. Each example is provided for explanation and not for limitation of this application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0021] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0022] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0023] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0024] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0025] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0026] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0027] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0028] In this article, the terms "state of charge" and "SOC" refer to the state of charge of a battery, which is the ratio of the battery's current remaining charge to its rated charge.

[0029] In this article, the term "surface pressure" refers to the pressure applied per unit area of ​​the battery surface.

[0030] The first aspect of this application, as Figure 1 As shown, a battery formation method is provided, which includes the following steps:

[0031] S1, First charging stage: Control the application of a first surface pressure to the battery and charge the battery with a constant current to the first charging state, where the first charging state is less than 5% SOC, and the first surface pressure is greater than or equal to 0.01MPa.

[0032] S2, Second charging stage: Control the application of a second surface pressure to the battery and charge the battery with a constant current to the second charging state, where the second charging state is 5%~80% SOC, wherein the second surface pressure is greater than the first surface pressure and the second surface pressure is less than or equal to 0.2 MPa.

[0033] S3, Third charging stage: Control the application of a third surface pressure to the battery and charge the battery with a constant current to the third charging state, wherein the third charging state is greater than 80% SOC, and the third surface pressure is less than the second surface pressure.

[0034] The battery formation method provided in some embodiments of this application, through coordinated control of the surface pressure in the first, second, and third charging stages, achieves initial uniform wetting of the electrolyte in the first charging stage, during which the battery is in a pre-charged state, by applying a relatively low first surface pressure. In the second charging stage, the battery is in the main formation state, and a second surface pressure greater than the first surface pressure is applied to the battery. This promotes close contact between the electrodes, inhibits electrode expansion, and also promotes more thorough wetting of the electrolyte, thereby providing favorable conditions for the formation of an inorganic dense inner SEI film mainly composed of Li2CO3 and LiF. Ultimately, this inhibits the intercalation of solvent molecules and reduces the consumption of active lithium. Furthermore, the second surface pressure is controlled at 0.2. Below MPa, it can prevent damage to the electrode structure from high surface pressure, improve the utilization rate of active materials, and thus improve the interface stability and cycle performance of the battery. In the third charging stage after formation, the battery is in a stress release state. Applying a third surface pressure to the battery, which is less than the second surface pressure, releases the internal stress accumulated in the main formation stage. On the one hand, it can reduce the impact on the electrode structure during pressure relief and improve the interface performance of the battery. On the other hand, it can reduce the rebound amplitude during pressure relief, reduce the expansion rate of the battery, reduce the electrode spacing, improve the lithium-ion transport rate, and promote a more uniform distribution of the SEI film. This results in minimal lithium consumption during high-temperature storage, improving residual capacity and recovery capacity, and thus improving the cycle performance of the battery.

[0035] In summary, the battery formation method provided in some embodiments of this application has a synergistic regulatory effect on the surface pressure in the first charging stage, the second charging stage, and the third charging stage, which improves the wettability of the electrolyte and inhibits electrode expansion. This improves the quality of the SEI film while reducing damage to the electrode structure, thereby improving the interface performance and cycle performance of the battery.

[0036] In some of these embodiments, the battery is a lithium manganese iron phosphate battery.

[0037] Understandably, if a lithium manganese iron phosphate (LMFP) battery system is used, the high-voltage formation process exacerbates lattice distortion due to the olivine lattice of LMFP, which can be either monocrystalline or polycrystalline. This leads to the delamination of the cathode electrolyte interface (CEI) film from the active material, resulting in decreased conductivity and a significant increase in interfacial impedance. Therefore, the battery formation method of this application is particularly suitable for LMFP batteries. By using a lower surface pressure to construct a dense CEI film during the main formation stage to reduce lattice distortion, and then further reducing the surface pressure in the third stage to release internal stress, the CEI film can stably bond with the LMFP, preventing interfacial delamination, reducing interfacial impedance, and fully leveraging the advantages of LMFP materials.

[0038] In some embodiments, the first surface pressure is 0.01 MPa to 0.1 MPa. Exemplarily, the first surface pressure can be, but is not limited to, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, or 0.1 MPa. Within the aforementioned first surface pressure range, sufficient pressure can be provided to promote initial uniform wetting of the electrolyte while preventing damage to the electrode structure from higher surface pressures.

[0039] In some embodiments, the second surface pressure is 0.1 MPa to 0.2 MPa. Exemplarily, the second surface pressure can be, but is not limited to, 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, 0.15 MPa, 0.16 MPa, 0.17 MPa, 0.18 MPa, 0.19 MPa, or 0.2 MPa. Within the aforementioned range of second surface pressure, sufficient pressure can be provided to effectively suppress electrode expansion while preventing damage to the electrode structure from higher surface pressures, thereby improving the utilization rate of active materials and ultimately enhancing the interface stability and cycle performance of the battery.

[0040] In some embodiments, the third surface pressure is 0.05 MPa to 0.15 MPa. Exemplarily, the third surface pressure can be, but is not limited to, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, and 0.15 MPa. Within the aforementioned third surface pressure range, elastic rebound is allowed, balancing the release of internal stress accumulated in the electrode contact and during the main formation stage.

[0041] In some embodiments, the temperature of the first charging stage is 25°C to 30°C. Exemplarily, the temperature of the first charging stage can be, but is not limited to, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C. Pre-charging within the above temperature range can effectively slow down the reduction reaction rate of the electrolyte, guiding it to form a denser and more stable initial SEI film, thereby effectively suppressing side reactions caused by excessively rapid reactions and excessive heat generation.

[0042] In some embodiments, the constant current charging current in the first charging stage is 0.05C to 0.1C. Exemplarily, the constant current charging current in the first charging stage can be, but is not limited to, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, or 0.1C. Within the above current range, using a low-rate constant current charging provides more sufficient time for the electrolyte to uniformly wet the surface, thereby facilitating the formation of a more uniform SEI film.

[0043] In some embodiments, the first charging stage charges to a first voltage, which is 0.1V to 3V. Exemplarily, the first voltage can be, but is not limited to, 0.1V, 0.5V, 1V, 1.5V, 2V, 2.5V, or 3V.

[0044] In some embodiments, the temperature of the second charging stage is 55°C to 65°C. Exemplarily, the temperature of the second charging stage can be, but is not limited to, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, and 65°C. Within the above temperature range, the accelerated lithium-ion migration kinetics and increased interfacial reaction rate are beneficial for guiding the preferential reduction of specific film-forming components (such as FEC) in the electrolyte, generating a denser inner SEI film mainly composed of inorganic substances such as Li₂CO₃ and LiF. Simultaneously, strictly controlling the upper temperature limit to no more than 65°C can effectively avoid side reactions such as violent and uncontrollable decomposition of the electrolyte solvent due to excessively high temperatures.

[0045] In some embodiments, the constant current charging current in the second charging stage is 0.1C to 0.2C. Exemplarily, the constant current charging current in the second charging stage can be, but is not limited to, 0.1C, 0.11C, 0.12C, 0.13C, 0.14C, 0.15C, 0.16C, 0.17C, 0.18C, 0.19C, or 0.2C. Within the above current range, using a small current in the second charging stage helps to slow down the interfacial chemical reaction rate, providing sufficient time for the uniform growth of a dense and stable SEI film. This facilitates the formation of an inorganic dense inner SEI film mainly composed of Li₂CO₃ and LiF. This dense SEI film can effectively suppress the intercalation of solvent molecules and reduce the consumption of active lithium.

[0046] In some embodiments, the second charging stage charges to a second voltage, which is 3.1V to 3.4V. Exemplarily, the second voltage can be, but is not limited to, 3.1V, 3.2V, 3.3V, or 3.4V.

[0047] In some embodiments, the temperature of the third charging stage is 40°C to 50°C. Exemplarily, the temperature of the third charging stage can be, but is not limited to, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, or 50°C. Within the above temperature range, appropriately lowering the temperature reduces side reactions of the electrolyte.

[0048] In some embodiments, the constant current charging current in the third charging stage is 0.2C to 0.33C. Exemplarily, the constant current charging current in the third charging stage can be, but is not limited to, 0.2C, 0.21C, 0.22C, 0.23C, 0.24C, 0.25C, 0.26C, 0.27C, 0.28C, 0.29C, 0.3C, 0.31C, 0.32C, and 0.33C. Within the above current range, it is beneficial to improve the lithium-ion transport rate, promote a more uniform distribution of the SEI film, minimize the lithium consumed by decomposition and recombination during high-temperature storage, and improve residual capacity and recovery capacity.

[0049] In some embodiments, the third charging stage charges to a third voltage, which is 3.5V to 4.3V. Exemplarily, the third voltage can be, but is not limited to, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V, 4V, 4.1V, 4.2V, or 4.3V.

[0050] In some embodiments, when the battery is charged to 100% SOC during the third charging stage, the third voltage is the cutoff voltage. The third charging stage specifically includes the following steps: charging the battery with a constant current to the cutoff voltage, and then charging it with a constant voltage to the cutoff current. The cutoff voltage is 4V~4.3V, and the cutoff current is less than or equal to 0.05C. For example, the cutoff voltage can be, but is not limited to, 4V, 4.1V, 4.2V, or 4.3V; the cutoff current can be, but is not limited to, 0.01C, 0.02C, 0.03C, 0.04C, or 0.05C.

[0051] In some embodiments, the battery formation method further includes the following steps:

[0052] S4, Discharge stage: Control the application of the third surface pressure to the battery, and discharge the battery at a constant current to the fourth voltage before releasing the pressure.

[0053] In some embodiments, the constant current discharge during the discharge phase is 0.2C to 0.5C. Exemplarily, the constant current discharge during the discharge phase can be, but is not limited to, 0.2C, 0.3C, 0.4C, or 0.5C.

[0054] In some embodiments, the fourth voltage during the discharge phase is 2V to 3V. Exemplarily, the fourth voltage during the discharge phase can be, but is not limited to, 2V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, 2.8V, 2.9V, or 3V.

[0055] This application provides a battery formation apparatus configured to perform any of the above-described battery formation methods.

[0056] A battery formation device is used to perform formation processing on batteries.

[0057] It is understood that the battery formation apparatus provided in this application, by applying any of the above-mentioned battery formation methods, has all the beneficial effects of the above-mentioned battery formation methods, which will not be elaborated here.

[0058] This application provides a battery manufacturing method, which includes any of the above-described battery formation methods.

[0059] A battery manufacturing method is used to manufacture batteries. In some embodiments, the battery manufacturing method further includes methods for injecting electrolyte and aging the battery.

[0060] It is understood that the battery production method provided in this application, by applying any of the above-mentioned battery formation methods, has all the beneficial effects of the above-mentioned battery formation methods, which will not be elaborated here.

[0061] This application provides a battery production system that includes any of the above-described battery formation apparatuses.

[0062] A battery production system is used to produce batteries. In some embodiments, the battery production system further includes means for casing, welding, encapsulating, and aging the batteries.

[0063] It is understood that the battery production system provided in this application, by applying any of the above-mentioned battery formation apparatuses, has all the beneficial effects of the battery formation apparatuses, which will not be elaborated further here.

[0064] A second aspect of this application provides a battery obtained by forming the battery using the battery formation method described in the first aspect.

[0065] In some embodiments, the battery is a secondary battery. A secondary battery includes a positive electrode, a negative electrode, and an electrolyte.

[0066] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0067] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a binder, and a conductive agent.

[0068] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0069] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0070] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0071] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0072] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0073] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0074] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0075] In the battery of this application, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0076] In the battery of this application, the negative electrode active material layer typically comprises a negative electrode active material and optional binders and conductive agents, and is usually formed by coating and drying a negative electrode slurry. The negative electrode slurry coating is typically formed by dispersing the negative electrode active material, optional conductive agents, and binders in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0077] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black (ACET), conductive carbon black (SP), Ketjen black (KB), carbon dots (CDs), carbon nanotubes (CNT), graphene, and carbon nanofibers (CNF).

[0078] As an example, the adhesive may be selected from one or more of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0079] Other commonly used negative electrode active materials include artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

[0080] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0081] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0082] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0083] In some embodiments, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).

[0084] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0085] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0086] The secondary battery using an electrolyte also includes a separator. The separator is positioned between the positive and negative electrodes, serving as a barrier. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material can be selected from one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF). The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0087] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0088] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0089] In some implementations, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0090] A third aspect of this application provides an electrical device that includes the battery provided in the second aspect above, the battery providing power to the electrical device.

[0091] The electrical device used in this application is not particularly limited and can be any electrical device known in the prior art. For example, the electrical device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors.

[0092] The present application will be further described below with reference to specific embodiments and comparative examples.

[0093] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0094] Example 1

[0095] Battery:

[0096] The positive electrode, PP separator, and negative electrode are stacked in a cyclic manner, with 29 positive electrode sheets. The stacked sheets are then encapsulated in an aluminum-plastic film, and finally, electrolyte is added to form a pouch battery. Specifically:

[0097] The positive electrode sheet is prepared by mixing lithium manganese iron phosphate, conductive agent SP, and binder PVDF in a ratio of 97:2:1 to form a slurry, which is then wet-coated. The slurry viscosity is 6500 mPa·s, the coating thickness is 150 μm, and the coating is compacted to 2.3 g / cm³ by roller pressing. 3 .

[0098] The negative electrode sheet is prepared by mixing graphite, binder (CMC:SBR=2:1), and conductive agent SP in a ratio of 96:3:1 to form a slurry, which is then wet-coated. The slurry viscosity is 4000 mPa·s, the coating thickness is 93 μm, and it is compacted to 1.6 g / cm³ by roller pressing. 3 .

[0099] The electrolyte is composed of 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved in a mixed solvent of ethylene carbonate (EC) and fluoroethylene carbonate (FEC), wherein the mass ratio of EC:FEC is 90.9:9.1, and LiPF6 accounts for 12 wt% of the total mass of the electrolyte.

[0100] Battery formation method:

[0101] The above-mentioned battery is then formed. The specific steps are as follows:

[0102] (1) First charging stage: Control the application of a first surface pressure to the battery, the first surface pressure is 0.05 MPa, and charge the battery at a constant current of 0.05C at 30°C to the first voltage, the first voltage is 3V. At this time, the state of charge of the battery is 5% SOC.

[0103] (2) Second charging stage: After the first charging stage, the second surface pressure is applied to the battery. The second surface pressure is 0.15MPa. At 65°C, the battery is charged at a constant current of 0.1C to the second voltage, which is 3.85V. At this time, the battery's state of charge is 80% SOC.

[0104] (3) Third charging stage: After the second charging stage, the third surface pressure is applied to the battery, which is 0.1MPa. At 45°C, the battery is charged at a constant current of 0.2C until the battery voltage reaches the cutoff voltage, which is 4.3V. Then, the battery is charged at a constant voltage of 4.3V until the cutoff current is 0.05C. At this time, the battery's state of charge is 100% SOC.

[0105] (4) Discharge stage: After the third charging stage, the control continues to apply the third surface pressure to the battery and discharges the battery at a constant current of 0.33C to the fourth voltage and then depressurizes it. The fourth voltage is 2.5V.

[0106] Example 2

[0107] The battery and battery formation method in this embodiment are basically the same as in Embodiment 1, except that:

[0108] In step (1), the first surface pressure is 0.01 MPa.

[0109] Example 3

[0110] The battery and battery formation method in this embodiment are basically the same as in Embodiment 1, except that:

[0111] In step (1), the first surface pressure is 0.1 MPa.

[0112] Example 4

[0113] The battery and battery formation method in this embodiment are basically the same as in Embodiment 1, except that:

[0114] In step (2), the second surface pressure is 0.1 MPa.

[0115] Example 5

[0116] The battery and battery formation method in this embodiment are basically the same as in Embodiment 1, except that:

[0117] In step (2), the second surface pressure is 0.2 MPa.

[0118] Example 6

[0119] The battery and battery formation method in this embodiment are basically the same as in Embodiment 1, except that:

[0120] In steps (3) and (4), the pressure on the third surface is 0.05 MPa.

[0121] Example 7

[0122] The battery and battery formation method in this embodiment are basically the same as in Embodiment 1, except that:

[0123] In steps (3) and (4), the pressure on the third surface is 0.15 MPa.

[0124] Comparative Example 1

[0125] The battery and battery formation method in this comparative example are basically the same as those in Example 1, except that:

[0126] In steps (1) to (4), the first surface pressure, the second surface pressure and the third surface pressure are all 0.1 MPa.

[0127] Comparative Example 2

[0128] The battery and battery formation method in this comparative example are basically the same as those in Example 1, except that:

[0129] In step (1), the first surface pressure is 0.005 MPa.

[0130] Comparative Example 3

[0131] The battery and battery formation method in this comparative example are basically the same as those in Example 1, except that:

[0132] In step (2), the second surface pressure is 0.25 MPa.

[0133] Comparative Example 4

[0134] The battery and battery formation method in this comparative example are basically the same as those in Example 1, except that:

[0135] In steps (1) to (4), the first surface pressure, the second surface pressure and the third surface pressure are all 0.4 MPa.

[0136] Comparative Example 5

[0137] The battery and battery formation method in this comparative example are basically the same as those in Example 1, except that:

[0138] In steps (3) and (4), the pressure on the third surface is 0.25 MPa.

[0139] Performance testing

[0140] (1) Interface stability test: Observe the interface of the battery after disassembly and formation.

[0141] (2) Cyclic performance test: At an ambient temperature of 25±2℃, charge at a constant current and constant voltage of 0.33C to the upper limit voltage of 4.4V, cut off current to 0.05C; let stand for 30 min; discharge at a constant current of 1C to 2.5V; let stand for 30 min; cycle the charge and discharge process for 500 times and record the data.

[0142] (3) Cyclic expansion rate test: Measure the thickness of the battery after 500 cycles and compare it with the thickness of the battery before cycling to calculate the cyclic expansion rate of the battery.

[0143] The test results are shown in Table 1.

[0144] Table 1

[0145]

[0146] As shown in Table 1, comparing Examples 1-7 and Comparative Examples 1-5, it can be seen that the battery formation methods provided in some embodiments of this application reduce the battery expansion rate while improving the battery's interface performance and cycle performance.

[0147] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A battery formation method, characterized in that, Includes the following steps: First charging stage: Control the application of a first surface pressure to the battery and charge the battery at a constant current to a first charging state, wherein the first charging state is less than 5% SOC, and the first surface pressure is greater than or equal to 0.01 MPa; Second charging stage: Control the application of a second surface pressure to the battery and charge the battery at a constant current to a second charging state, the second charging state being 5%~80% SOC, wherein the second surface pressure is greater than the first surface pressure and the second surface pressure is less than or equal to 0.2 MPa; Third charging stage: Control the application of a third surface pressure to the battery and charge the battery with a constant current to a third charging state, wherein the third charging state is greater than 80% SOC, and the third surface pressure is less than the second surface pressure.

2. The battery formation method according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The first surface pressure is 0.01 MPa to 0.1 MPa; (2) The second surface pressure is 0.1 MPa~0.2 MPa; (3) The third surface pressure is 0.05 MPa~0.15 MPa.

3. The battery formation method according to claim 1 or 2, characterized in that, The first charging phase satisfies at least one of the following conditions: (1) The temperature of the first charging stage is 25℃~30℃; (2) The constant current charging current in the first charging stage is 0.05C~0.1C; (3) The first charging stage is charged to a first voltage, which is 0.1V~3V.

4. The battery formation method according to claim 1 or 2, characterized in that, The second charging phase satisfies at least one of the following conditions: (1) The temperature of the second charging stage is 55℃~65℃; (2) The constant current charging current in the second charging stage is 0.1C~0.2C; (3) The second charging stage is charged to the second voltage, which is 3.1V~3.4V.

5. The battery formation method according to claim 1 or 2, characterized in that, The third charging stage satisfies at least one of the following conditions: (1) The temperature of the third charging stage is 40℃~50℃; (2) The constant current charging current in the third charging stage is 0.2C~0.33C; (3) The third charging stage is charged to a third voltage, which is 3.5V~4.3V.

6. The battery formation method according to claim 5, characterized in that, When the third charging stage reaches 100% SOC, the third voltage is the cutoff voltage. The third charging stage specifically includes the following steps: Charge the battery with a constant current to the cutoff voltage, and then charge it with a constant voltage to the cutoff current. The cutoff voltage is 4V~4.3V, and the cutoff current is less than or equal to 0.05C.

7. The battery formation method according to claim 1 or 2, characterized in that, It also includes the following steps: Discharge phase: The third surface pressure is applied to the battery and the battery is discharged at a constant current to the fourth voltage before the pressure is released.

8. The battery formation method according to claim 7, characterized in that, The discharge phase satisfies at least one of the following conditions: (1) The constant current discharge current in the discharge stage is 0.2C~0.5C; (2) The fourth voltage in the discharge stage is 2V~3V.

9. A battery, characterized in that, The battery is obtained by forming it using the battery formation method described in any one of claims 1 to 8.

10. An electrical device, characterized in that, Includes the battery as described in claim 9.

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