Battery formation method and battery manufacturing method

Abstract

The invention provides a battery formation method and a battery manufacturing method, and belongs to the technical field of batteries. The battery formation method comprises the following steps: charging a to-be-formed battery to a fully-charged state to obtain a fully-charged battery; a circulating charging and discharging stage: executing at least one charging and discharging step to obtain a circulating battery; the charging and discharging step comprises the following steps: discharging the fully-charged battery to a second charge state at a first discharging rate, and recharging to a fully-charged state; the first discharge rate is greater than 0 and less than or equal to 0.05 C; in the discharging stage, the circulating battery is discharged to a third charge state; the third state of charge is less than the second state of charge. Therefore, chemical self-discharge gas production can be accelerated in the formation stage, so that gas production of the battery in the aging stage is reduced, damage to an SEI film is reduced, and the cycle life of the battery is prolonged.

Description

[0001] This application is a divisional application of Chinese patent application No. 202411413803.X, with an application date of October 11, 2024, and the invention name is "Battery Formation Method, Battery Manufacturing Method, Battery Formation Equipment and Battery Manufacturing System". Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a battery formation method, a battery manufacturing method, a battery formation device and a battery manufacturing system. Background Art

[0003] Energy conservation and emission reduction are the key to the sustainable development of the automobile industry. Electric vehicles have become an important part of the sustainable development of the automobile industry due to their advantages of energy conservation and environmental protection. For electric vehicles, battery technology is an important factor related to their development.

[0004] Batteries go through a formation process during the manufacturing process. During the formation stage, when the battery is charged for the first time, the reaction that generates the solid electrolyte interface (SEI) film and the side reactions of the film formation will cause the generation of gas. If the generated gas cannot be removed in time, it will affect the quality of the solid electrolyte interface (SEI) film and affect the life of the battery. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems existing in the background technology. To this end, one purpose of the present application is to provide a battery formation method, a battery manufacturing method, a battery formation device and a battery manufacturing system to improve the SEI film formation quality and increase the battery life.

[0006] The embodiment of the first aspect of the present application provides a battery formation method, which includes a first charging stage, a second charging stage, a cyclic charge and discharge stage, and a discharge stage. The first charging stage includes: charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to the formation cut-off state of charge; the second charging stage includes: charging the first rechargeable battery to a fully charged state to obtain a fully charged battery; and the cyclic charge and discharge stage, performing at least one charge and discharge step to obtain a cyclic battery; the charge and discharge step includes: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging to a fully charged state; the first discharge rate is less than the minimum charge rate of the first charging stage; in the discharge stage, discharging the cyclic battery to a third state of charge; the third state of charge is greater than the first state of charge and less than the second state of charge.

[0007] In the technical solution of the embodiment of the present application, the lithium-ion battery will produce some gas side reactions during the aging stage after the formation, and the gas side reactions will affect the film quality of the SEI film. If the gas side reactants produced cannot be removed in time, the negative electrode area of ​​the battery corresponding to the bubbles will form interface black spots, thereby affecting the stability and safety of the battery. By setting the cyclic charge and discharge stage to simulate chemical self-discharge, the battery can accelerate gas production in the formation stage, which is conducive to moving the gas production in the aging stage to the formation stage and exhausting the gas, thereby reducing the gas production of the battery in the aging stage, which is conducive to reducing the damage to the SEI film and improving the battery cycle life.

[0008] In some embodiments, the first state of charge is greater than the formation cut-off state of charge, and the first charging stage includes: a first charging sub-stage, including: constant current charging of the battery to be formed until the state of charge of the battery to be formed is greater than or equal to the formation cut-off state of charge; a second charging sub-stage, including: constant current charging of the battery to be formed until the state of charge of the battery to be formed reaches the first state of charge, thereby obtaining a first rechargeable battery; wherein the maximum charging rate of the first charging sub-stage is less than the minimum charging rate of the second charging sub-stage. By setting the first charging sub-stage and the second charging sub-stage in the first charging stage, and the maximum charging rate of the first charging sub-stage is less than the minimum charging rate of the second charging sub-stage, it is beneficial to reduce the damage to the SEI film, reduce the time of the first charging stage, and improve the formation efficiency.

[0009] In some embodiments, the first charging sub-stage includes: constant current charging the battery to be formed at a second charging rate until the state of charge of the battery to be formed reaches a fourth state of charge; repeating the following steps until the state of charge of the battery to be formed is greater than or equal to the formation cut-off state of charge: constant current charging the battery to be formed at a third charging rate less than the second charging rate for a first preset time, so that the state of charge of the battery to be formed increases by a preset state of charge value; and standing for a second preset time. In this way, the generated gas can be discharged in time during the charging process, which is conducive to the formation of a high-quality SEI film and improves the cycle life and formation efficiency of the battery.

[0010] In some embodiments, the formation cut-off state of charge is determined according to the following steps: providing an experimental battery to be formed that is the same as the battery to be formed; charging the experimental battery at a constant current until the experimental battery is charged to the upper limit voltage of the charge, and detecting the gas flow rate of the experimental battery during the charging process; determining the formation cut-off state of charge according to the gas flow rate and the corresponding charging capacity of the experimental battery during the charging process. Determining the formation cut-off state of charge by the gas flow rate and the corresponding charging capacity of the experimental battery during the charging process is conducive to reasonably and accurately determining the formation cut-off state of charge, which is conducive to improving the formation efficiency and reducing the damage to the SEI film.

[0011] In some embodiments, the charging rate of the experimental battery at constant current charging is greater than 0 and less than or equal to 0.05 C. By charging the experimental current at a smaller rate, it is beneficial to fully react and produce gas inside the battery, reduce the error of the gas flow detection result caused by the hysteresis of gas production, more accurately obtain the gas production flow and charging capacity of the experimental battery during the charging process and explore the correlation between the two, so as to determine the formation cut-off charge state and improve data accuracy.

[0012] In some embodiments, determining the formation cut-off state of charge according to the gas production flow rate and the corresponding charging capacity of the experimental battery during the charging process includes: determining the gas production cut-off state of charge according to the corresponding charging capacity when the gas production flow rate of the experimental battery drops to a preset flow rate threshold and the design capacity of the experimental battery; determining the formation cut-off state of charge according to the gas production cut-off state of charge, wherein the formation cut-off state of charge is greater than the gas production cut-off state of charge. Determining the formation cut-off state of charge by the gas production cut-off state of charge of the experimental battery can reduce the detection accuracy requirements and the influence of gas production hysteresis, while taking into account the accuracy of the detection data.

[0013] In some embodiments, the second charging stage includes: charging the first rechargeable battery with a constant current until the voltage of the first rechargeable battery reaches the upper limit of the charging voltage; and charging the first rechargeable battery with a constant voltage to a fully charged state to obtain a fully charged battery. By charging the first rechargeable battery with a constant current and a constant voltage to fully charge it, the charging efficiency can be taken into account and time can be saved.

[0014] In some embodiments, constant current charging of the first rechargeable battery until the voltage of the first rechargeable battery reaches the upper limit of the charging voltage includes: constant current charging of the first rechargeable battery at a fourth charging rate until the voltage of the first rechargeable battery reaches the upper limit of the charging voltage; wherein the fourth charging rate is greater than the maximum charging rate of the first charging stage. Constant current charging of the first rechargeable battery using the fourth charging rate with a higher charging rate is conducive to the first rechargeable battery reaching the upper limit of the charging voltage in a shorter time, which is conducive to saving formation time, thereby improving formation efficiency.

[0015] In some embodiments, the charging and discharging steps include: standing for a third preset time; discharging the fully charged battery to a second state of charge at a first discharge rate; standing for a fourth preset time; and charging the fully charged battery to a full charge state at a fifth charge rate; wherein the first discharge rate is greater than 0 and less than or equal to 0.05C. By setting the first discharge rate to be greater than 0 and less than or equal to 0.05C, it is possible to discharge the fully charged battery with an extremely small current to simulate the formation self-discharge process, thereby accelerating gas production, thereby reducing gas production in the subsequent aging process, and reducing damage to the SEI film.

[0016] In some embodiments, the charge and discharge steps are performed 3-5 times, which is beneficial to balance the formation efficiency, reduce time cost and increase gas production, thereby reducing damage to the SEI film.

[0017] In some embodiments, the difference between the first state of charge and the formation cut-off state of charge is greater than or equal to 2% and less than or equal to 10%. In some embodiments, the difference between the first state of charge and the formation cut-off state of charge is greater than or equal to a preset state of charge value. This is conducive to timely discharge of gas produced in the formation stage, facilitating the formation of a high-quality SEI film, thereby improving battery stability.

[0018] In some embodiments, the value of the second state of charge is greater than or equal to 99% and less than or equal to 99.9%. Cyclic charging and discharging between the second state of charge and the fully charged state is beneficial to accelerate the gas production process of the cycle battery, thereby reducing the gas production of the battery during the subsequent aging process, thereby reducing damage to the SEI film and improving the cycle life of the battery.

[0019] In some embodiments, the difference between the first state of charge and the third state of charge is greater than 0 and less than or equal to 20%. The difference between the third state of charge and the first state of charge is set in a range of greater than 0 and less than or equal to 20%, which is conducive to the subsequent aging process, thereby improving the battery life.

[0020] In some embodiments, the battery is in a negative pressure exhaust state in the first charging stage, the second charging stage, and the cyclic charge and discharge stage. The internal pressure of the battery in the first charging stage, the second charging stage, and the cyclic charge and discharge stage is lower than the standard atmospheric pressure, which is conducive to timely exhausting the gas produced in the first charging stage, the second charging stage, and the cyclic charge and discharge stage, thereby reducing the risk of interface black spots and lithium precipitation.

[0021] The second aspect of the present application provides a battery manufacturing method, including performing the battery formation method in the above embodiment on a battery to be formed. The battery formation method in this embodiment is advantageous for manufacturing a battery with high SEI film quality and good stability.

[0022] The embodiment of the third aspect of the present application provides a battery formation device, the battery formation device includes a first charging component, a second charging component, a cyclic charge and discharge component and a discharge component. The first charging component is configured to perform a first charging stage on the battery to be formed, including charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to the formation cut-off state of charge; the second charging component is configured to charge the first rechargeable battery to a fully charged state to obtain a fully charged battery; the cyclic charge and discharge component is configured to perform at least one charge and discharge step on the fully charged battery to obtain a cycle battery; the charge and discharge step includes: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging to a fully charged state; the first discharge rate is less than the minimum charge rate of the first charging stage; the discharge component is configured to discharge the cycle battery to a third state of charge; the third state of charge is greater than the first state of charge and less than the second state of charge. By setting the second charging component and the cyclic charge and discharge component to form the battery, it is beneficial to form a high-quality SEI film in the battery, thereby improving the stability of the battery.

[0023] The fourth aspect of the present application provides a battery manufacturing system, including the battery formation equipment in the above-mentioned embodiment. The battery manufacturing system in the embodiment of the present application is used to manufacture batteries, which is conducive to improving the stability of the manufactured batteries.

[0024] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0026] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0027] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0028] Figure 3 This is one of the flow charts of the battery formation method according to some embodiments of the present application;

[0029] Figure 4 A flowchart of the first charging sub-stage of some embodiments of the present application;

[0030] Figure 5 This is a second flow chart of a battery formation method according to some embodiments of the present application;

[0031] Figure 6 A schematic diagram of confirming the cut-off state of charge of some embodiments of the present application;

[0032] Figure 7 This is a graph showing the change in gas production volume over time during the high-temperature aging process of Battery 1 and Battery 2.

[0033] Description of reference numerals:

[0034] Vehicles 1000;

[0035] Battery 100, controller 200, motor 300;

[0036] Box body 10, first part 11, second part 12;

[0037] Battery cell 20;

[0038] Experimental battery 30, gas conduit 31, gas test flow meter 32, flow meter outlet 33. DETAILED DESCRIPTION

[0039] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0041] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0042] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0043] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0044] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0045] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0046] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0047] At present, from the perspective of market development, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.

[0048] In the battery manufacturing process, the assembled battery needs to go through three processes of injection, formation and aging to produce a finished battery. Injection is the process of injecting electrolyte into the vacuum-dried deep dehydrated battery shell, formation is the process of charging the battery after injection, and aging is the process of leaving the formed battery at a certain temperature for a period of time.

[0049] In the formation stage, during the first charge and discharge process of the battery, when the electrode material and the electrolyte react at the solid-liquid interface, a passivation layer covering the surface of the electrode material is formed. This passivation layer is the solid electrolyte interface (SEI) film. The SEI film is a key component in the battery. It forms a thin film between the battery's electrode and the electrolyte, which prevents excessive chemical reactions inside the battery. It also prevents the dissolution of the electrode material and the decomposition of the electrolyte, thereby maintaining the stability of the battery.

[0050] During the first charge and discharge process of the battery and the subsequent aging process, some gas side reactions will also be generated, and the gas side reactions will affect the film quality of the SEI film. Taking lithium batteries as an example, during the formation and aging process, the formation of the SEI film and side reactions will produce gas, including hydrocarbon gases such as C2H4 and inorganic gases such as CO2 and H2. As the state of charge increases during the charging process, the negative electrode potential of the battery will gradually decrease while the positive electrode potential will gradually increase. In addition, since the battery is in the formation stage, it is inevitable that the film formation reaction of the negative electrode side SEI or the positive electrode side CEI (cathode electrolyte interphase, positive electrode electrolyte interface) will be imperfect. Therefore, in the subsequent aging stage, the battery will continue to have related side reactions, thereby affecting the film quality of the SEI film. If the gas side reactants generated during the formation and aging of the battery cannot be removed in time, it will not only affect the film quality of the SEI film, but may also lead to the risk of interface black spots and lithium precipitation, thereby affecting the cycle life and stability of the battery.

[0051] Based on the above considerations, by simulating chemical self-discharge in the battery formation stage, that is, by stimulating side reactions at a low rate in the high SOC interval to accelerate gas production and reduce the gas production of the battery during the aging process, the embodiment of the present application proposes a battery formation method, which includes a first charging stage, a second charging stage, a cyclic charge and discharge stage, and a discharge stage. The first charging stage includes: charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to the formation cut-off state of charge; the second charging stage includes: charging the first rechargeable battery to a fully charged state to obtain a fully charged battery; and the cyclic charge and discharge stage, performing at least one charge and discharge step to obtain a cycle battery; the charge and discharge step includes: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging it to a fully charged state; the first discharge rate is less than the minimum charge rate of the first charging stage; in the discharge stage, the cycle battery is discharged to a third state of charge; the third state of charge is greater than the first state of charge and less than the second state of charge. Therefore, by setting the second charging stage and the charge-discharge cycle stage, it is possible to accelerate chemical self-discharge gas production in the formation stage, reduce battery gas production during aging, and help reduce damage to the SEI film, thereby increasing the cycle life of the battery.

[0052] The battery cells disclosed in the embodiments of the present application can be used, but not limited to, in electrical devices such as vehicles, ships or aircraft. A power supply system comprising the battery cells and batteries disclosed in the present application can be used to form the electrical device.

[0053] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0054] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0055] Please refer to Figure 1 , Figure 1A schematic diagram of the structure of a vehicle provided for some embodiments of the present application. Vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0056] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0057] Please refer to Figure 2 , Figure 2 Schematic diagram of the exploded structure of the battery provided for some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, the first part 11 can be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0058] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0059] Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0060] The present application embodiment provides a battery formation method, such as Figure 3 As shown, the method includes:

[0061] S310, a first charging stage, comprising: charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to the formation cut-off state of charge;

[0062] S320, a second charging stage, comprising: charging the first rechargeable battery to a fully charged state to obtain a fully charged battery;

[0063] S330, in a cyclic charge and discharge stage, performing at least one charge and discharge step to obtain a cyclic battery; the charge and discharge step comprises: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging it to a fully charged state; the first discharge rate is less than the minimum charge rate of the first charging stage;

[0064] S340, discharging stage, discharging the circulating battery to a third state of charge; the third state of charge is greater than the first state of charge and less than the second state of charge.

[0065] The battery to be formed is a battery that has been assembled into a shell and filled with liquid, and the battery can be a battery cell of any model or specification. It is understandable that, unless otherwise specified, the embodiments of the present application are described by taking lithium batteries as an example.

[0066] The state of charge (SOC) is the ratio of the remaining capacity of the battery to the capacity of the completed charging state. The formation cutoff state of charge (CSOC) refers to the state of charge at which the battery is charged to a specific state of charge during the formation process of the lithium-ion battery, at which point the formation process of the battery ends. This state is part of the formation process in the battery manufacturing process. The purpose of the formation process is to fully activate the electrode materials of the battery and to form a stable solid electrolyte interface (SEI) film on the electrode surface. Batteries of different materials or components have different corresponding formation cutoff states of charge. The specific formation cutoff state of charge can be selected based on the empirical value of batteries of the same material and specification type, or it can be obtained by detection, for example, by detecting the gas production rate or gas production flow rate in the formation stage. The first state of charge can be selected based on experience as a state of charge value greater than or equal to the formation cutoff state of charge.

[0067] Taking the graphite negative electrode as an example, the SEI film formation potential of graphite is mainly between 0.3 volts (V) and 1.0 volts (V), and the corresponding SOC range is mainly concentrated between 1% and 15%. Therefore, in some embodiments, the formation cutoff state of charge can be set to 15%, and the first state of charge can be selected to be a value greater than or equal to 15%, such as a value in the range of 15% to 30%.

[0068] In the first charging stage in S310, the battery is charged to the first state of charge, which means that the SEI film of the battery to be formed has been basically formed in this charging stage. The charging in the initial formation stage can be completed by continuous charging once, or by charging multiple times. In some embodiments, it is possible to first charge to a certain SOC interval and let it stand, then continue to charge to another SOC interval and let it stand, and then continue the cycle of charging and standing until the SOC meets the first state of charge.

[0069] The fully charged state refers to the state when the battery capacity is fully charged, that is, the battery SOC is 100%. Different types of batteries have different methods for determining the fully charged state. In some embodiments, such as lithium batteries, the fully charged state can be determined by the negative slope of the voltage curve or the combination of voltage and current.

[0070] The charging in the second charging stage in S320 can be completed by continuous charging once or by multiple charging steps. In some embodiments, constant current charging is first used to make the SOC of the battery reach a certain range, and then constant voltage charging is performed until the battery reaches a full charge state.

[0071] In S330, the second state of charge is greater than the first state of charge. In some embodiments, the second state of charge has a value range of 99% to 99.9%. By cyclically charging and discharging between the second state of charge and the fully charged state to simulate the chemical self-discharge of the battery, gas generation is accelerated, which is conducive to forming a high-quality SEI film, thereby improving the cycle life of the battery.

[0072] In S340, the discharge mode of the cycle battery may be constant voltage discharge, constant current discharge or a combination of the two. In some embodiments, the difference between the third state of charge and the first state of charge ranges from 0-20%.

[0073] Lithium-ion batteries will be aged after formation. Some gas side reactions will be generated during the aging stage, which will affect the film quality of the SEI film. Since the aging stage is closed-mouth aging, that is, the lithium-ion battery will be welded with sealing nails after formation to isolate the battery from the external environment, if the gas side reactants generated cannot be removed in time, the negative electrode area of ​​the battery corresponding to the bubbles will form interface black spots, thereby affecting the stability and safety of the battery. By setting the cyclic charge and discharge stage to simulate chemical self-discharge, the battery can accelerate gas production in the formation stage, which is conducive to moving the gas production in the aging stage to the formation stage and exhausting the gas, thereby reducing the gas production of the battery in the aging stage, which is conducive to reducing damage to the SEI film and improving the battery cycle life.

[0074] According to some embodiments of the present application, the first state of charge is greater than the formation cut-off state of charge, and the first charging stage includes: a first charging sub-stage, including: constant current charging of the battery to be formed until the state of charge of the battery to be formed is greater than or equal to the formation cut-off state of charge; a second charging sub-stage, including: constant current charging of the battery to be formed until the state of charge of the battery to be formed reaches the first state of charge, to obtain a first charged battery; wherein the maximum charging rate of the first charging sub-stage is less than the minimum charging rate of the second charging sub-stage.

[0075] Constant current charging refers to charging the battery with a constant current input. The charging rate refers to the speed of the charging current relative to the rated capacity. The maximum charging rate of the first charging sub-stage is less than the minimum charging rate of the second charging sub-stage. In some embodiments, the minimum charging rate of the second charging sub-stage may be 2-5 times the maximum charging rate of the first charging sub-stage. In this embodiment, the first charging stage may include two charging stages, namely, first charging the battery to a formation cutoff state of charge at a smaller charging rate, and then charging to the first state of charge at a larger charging rate. Since the formation of the SEI film mainly occurs in the first charging sub-stage, using a smaller charging rate at this time can improve the film formation quality, and using a higher charging rate in the second charging sub-stage can save process time.

[0076] In some embodiments, the first charging sub-stage and the second charging sub-stage may each include one or more charging sub-stages. A certain period of time may be allowed between two adjacent charging stages or charging sub-stages to help the chemical reaction inside the battery reach equilibrium and promote uniform formation of the SEI film.

[0077] By setting the first charging sub-stage and the second charging sub-stage in the first charging stage, and the maximum charging rate of the first charging sub-stage is less than the minimum charging rate of the second charging sub-stage, it is beneficial to reduce damage to the SEI film, reduce the time of the first charging stage, and improve the formation efficiency.

[0078] According to some embodiments of the present application, Figure 4 As shown, the first charging sub-stage includes:

[0079] S410, constant current charging the battery to be formed at a second charging rate until the state of charge of the battery to be formed reaches a fourth state of charge;

[0080] S420, repeatedly performing the following steps until the state of charge of the battery to be formed is greater than or equal to the formation cut-off state of charge:

[0081] S421, charging the battery to be formed with a constant current for a first preset time period at a third charging rate that is less than the second charging rate, so that the state of charge of the battery to be formed increases by a preset state of charge value;

[0082] S422: Wait for a second preset time period.

[0083] The fourth charge state in S410 may be a charge state corresponding to the film formation potential of the SEI film. In some embodiments, the fourth charge state may range from 1% to 15%, for example, the fourth charge state may be 1%. The second charge rate is greater than the third charge rate, and the film formation potential of the SEI film may be reached more quickly.

[0084] In S421, it is actually the SEI film formation and side reaction gas production stage, the first preset time length can be 15 minutes (min)-30 minutes (min), the second preset time length can be 30 seconds (s), and the preset charge state value can be 2.5%.

[0085] In some embodiments, Figure 5As shown, the first charging stage can adopt a negative pressure formation process, connected to the negative pressure machine through the battery cell injection port, adjust the internal pressure value of the battery cell to -80±5 kilopascals (kPa), and let it stand for 10 seconds; adopt a second charging ratio of 0.2C constant current charging mode to charge the battery to 1% SOC to quickly reach the SEI film formation potential, the charging time is 3 minutes, and it is left to stand for 30 seconds; adopt a third charging ratio of 0.1C constant current charging mode to increase the battery's state of charge by 2.5% SOC, wherein the charging time is 15 minutes, and it is left to stand for 30 seconds to discharge the generated gas; repeat the above-mentioned third charging ratio to increase the battery's state of charge by 2.5% SOC and let it stand until the state of charge of the battery to be formed satisfies the expression: 1%+n×2.5%≥S, wherein S is the formation cut-off state of charge. Figure 5 The n in denoted by has been performed the number of times the aforementioned third charging rate is used to increase the battery state of charge by 2.5% SOC and then the battery is left to stand.

[0086] In some embodiments, S is 25%; then a constant current charging mode with a charging rate of 0.5C is used to make the battery's state of charge be a first state of charge of 30% and stand for 30 seconds, wherein the charging time is T1, and T1 satisfies the expression:

[0087]

[0088] The first charging sub-stage is the key stage of SEI film formation. The first charging sub-stage is divided into multiple charging stages, and appropriate charging rates and standing times after charging are set for different charging stages. The gas generated during the charging process can be discharged in time, which is conducive to the formation of high-quality SEI film and the improvement of battery cycle life and formation efficiency.

[0089] According to some embodiments of the present application, the formation cut-off state of charge is determined according to the following steps: providing an experimental battery to be formed that is the same as the battery to be formed; charging the experimental battery with a constant current until the experimental battery is charged to an upper charging limit voltage, and detecting the gas production flow rate of the experimental battery during the charging process; determining the formation cut-off state of charge based on the gas production flow rate of the experimental battery during the charging process and the corresponding charging capacity.

[0090] The experimental battery is a battery that needs to be formed, which is the same as the battery to be formed. The materials, specifications, preparation processes and conditions of each component in the experimental battery can be the same as those of the battery to be formed, for example, they can be products of the same batch produced by the same production line. The upper limit voltage of the battery charge refers to the highest voltage value reached by the battery voltage during the charging process. Exceeding this value may cause the battery to be overcharged, thereby damaging the performance and life of the battery. For lithium-ion batteries, this upper limit voltage is usually around 4.2 volts, but may vary depending on the battery type and design. During the charging process, the battery voltage will gradually increase as the charging progresses. When the battery terminal voltage reaches the set upper limit voltage, the charger will switch from constant current charging mode to constant voltage charging mode, that is, the voltage remains constant, and the current decreases as the battery is gradually filled until the charging is completed.

[0091] The formation cut-off state of charge is determined based on the gas production flow rate and the corresponding charging capacity of the experimental battery during the charging process, that is, the formation gas production flow rate in the battery is synchronously detected during the charging process of the experimental battery to obtain the corresponding relationship between the gas production flow rate and the charging capacity, and the formation cut-off state of charge is determined based on the corresponding relationship. For example, the charging capacity when the experimental battery no longer produces gas during the charging process is defined as the formation cut-off state of charge.

[0092] During the charging process, negative pressure can be used to discharge and detect the gas flow rate of the experimental battery during the charging process. Figure 6 In the example, the gas production flow rate of the experimental battery is detected by the gas test flowmeter 32. The gas conduit 31 connects the experimental battery 30 with the gas test flowmeter 32, and the battery filling port is welded to the gas production nail for fixation. The gas produced in the experimental battery 30 will flow to the gas test flowmeter 32 through the gas conduit 31 and then flow out through the flowmeter outlet 33, so that the gas production flow rate and the corresponding charging capacity of the experimental battery during the charging process can be obtained.

[0093] Determining the formation cut-off state of charge by testing the gas production flow rate and the corresponding charging capacity of the battery during the charging process is beneficial to reasonably and accurately determine the formation cut-off state of charge, which is beneficial to improving the formation efficiency and reducing the damage to the SEI film.

[0094] According to some embodiments of the present application, the charging rate of the constant current charging of the experimental battery is greater than 0 and less than or equal to 0.05C.

[0095] The constant current charging of the experimental battery can be performed at a set charging rate, and the charging rate has a value range of greater than 0 and less than or equal to 0.05C, for example, 0.01C, 0.02C, 0.03C, 0.04C or 0.05C.

[0096] In some embodiments, the constant current charging of the experimental battery may also include multiple charging sub-stages, such as a charging stage similar to the first charging sub-stage including stages S410-S420 in the above embodiments, that is, first charging to a set state of charge, which may be a state of charge corresponding to the SEI film formation potential; then charging in stages multiple times with a set capacity charged each time until the charging upper limit voltage is reached, and a set period of time may be allowed to rest between two adjacent charges.

[0097] In other embodiments, the constant current charging of the experimental battery can also be completed in one time. For example, the experimental battery is first placed at an ambient temperature of 45°C for 2 hours, and then charged at a lower charging rate with a constant current until the charging upper limit voltage is reached. It is understood that the charging rate here can be 0.01C, 0.02C, 0.03C, 0.04C or 0.05C.

[0098] Charging the experimental current at a smaller rate is beneficial to the full reaction and gas production inside the battery, reducing the error in the gas flow detection result caused by the hysteresis of gas production, and more accurately obtaining the gas production flow and charging capacity of the experimental battery during the charging process and exploring the correlation between the two, so as to determine the formation cut-off charge state and improve data accuracy.

[0099] According to some embodiments of the present application, determining the formation cut-off state of charge according to the gas production flow rate and the corresponding charging capacity of the experimental battery during the charging process includes: determining the gas production cut-off state of charge according to the charging capacity corresponding to when the gas production flow rate of the experimental battery drops to a preset flow rate threshold and the design capacity of the experimental battery; determining the formation cut-off state of charge according to the gas production cut-off state of charge, wherein the formation cut-off state of charge is greater than the gas production cut-off state of charge.

[0100] Considering the limitation of gas flow detection accuracy and the hysteresis of the gas production process in the formation stage, it is not easy to fully confirm the time point when the gas production flow is 0 and the corresponding state of charge, but it is easy to have large errors. Therefore, when determining the formation cut-off state of charge, a gas production cut-off state of charge can be determined based on the gas production flow. As the battery charging capacity increases, the formation reaction gradually weakens, and the gas flow generated inside the battery also gradually decreases. When the gas production flow in the battery is reduced to a preset flow threshold, the corresponding battery state of charge is the gas production cut-off state of charge. The gas production cut-off state of charge can be expressed by the ratio of the charging capacity Q that has been charged into the battery when the gas production flow in the battery is reduced to the preset flow threshold to the design capacity Qn of the battery, that is, Q / Qn.

[0101] Since it is easier to detect whether the gas production flow rate is lower than the preset flow rate threshold, and by reasonably selecting the preset flow rate threshold and based on the correlation between the gas production cut-off state of charge and the formation cut-off state of charge, the formation cut-off state of charge can be estimated based on the gas production cut-off state of charge corresponding to when the gas production flow rate is reduced to the preset flow rate threshold.

[0102] The formation cut-off state of charge is greater than the gas production cut-off state of charge, and the specific size can be determined according to the battery type and the size of the preset flow threshold. In some embodiments, the formation cut-off state of charge can be based on the gas production cut-off state of charge plus a preset margin, so that the hysteresis of gas production can be better taken into account. For example, the value range of the increased preset margin is 0%-5% SOC, and specifically 1%, 2%, 3%, 4% or 5% can be selected.

[0103] By determining the formation cut-off state through the gas production cut-off charge state of the experimental battery, the requirements for detection accuracy and the influence of gas production hysteresis can be reduced, while taking into account the accuracy of the detection data.

[0104] According to some embodiments of the present application, the second charging stage includes: charging the first rechargeable battery with a constant current until the voltage of the first rechargeable battery reaches an upper limit of the charging voltage; and charging the first rechargeable battery with a constant voltage to a fully charged state to obtain a fully charged battery.

[0105] In the second charging stage, the first rechargeable battery is charged with constant current. In some embodiments, the charging rate of the first rechargeable battery is in the range of 0.6C-1C, and specifically 0.6C, 0.7C, 0.8C, 0.9C or 1C can be selected. The first rechargeable battery is charged with constant voltage to a full charge state. In some embodiments, the charging rate of the first rechargeable battery is in the range of 0.01C-0.05C, and specifically 0.01C, 0.02C, 0.03C, 0.04C or 0.05C can be selected.

[0106] The first rechargeable battery is charged with a constant current and a constant voltage so as to be fully charged, thus taking into account both charging efficiency and time saving.

[0107] According to some embodiments of the present application, constant current charging of the first rechargeable battery until the voltage of the first rechargeable battery reaches the upper limit of the charging voltage includes: constant current charging of the first rechargeable battery at a fourth charging rate until the voltage of the first rechargeable battery reaches the upper limit of the charging voltage; wherein the fourth charging rate is greater than the maximum charging rate of the first charging stage.

[0108] The fourth charging rate is greater than the maximum charging rate of the first charging stage. In some embodiments, the fourth charging rate ranges from 0.6C to 1C, and specifically can be 0.6C, 0.7C, 0.8C, 0.9C or 1C.

[0109] By adopting the fourth charging rate with a higher charging rate to charge the first rechargeable battery with a constant current, the first rechargeable battery can reach the upper limit of the charging voltage in a shorter time, which is beneficial to saving formation time, thereby improving formation efficiency.

[0110] According to some embodiments of the present application, the charging and discharging steps include: standing for a third preset time; discharging the fully charged battery at a first discharge rate to a second state of charge; standing for a fourth preset time; charging the fully charged battery at a fifth charge rate to a fully charged state; wherein the first discharge rate is greater than 0 and less than or equal to 0.05C.

[0111] The third preset duration may be the same as the fourth preset duration. In some embodiments, the third preset duration and the fourth preset duration are both in the range of 30s-60s, and the specific values ​​may be 30s, 40s, 50s or 60s. The first discharge rate is greater than 0 and less than or equal to 0.05C. In some embodiments, the first discharge rate may be 0.01C, 0.02C, 0.03C, 0.04C or 0.05C. Among them, the fifth charge rate may be the same as the first discharge rate.

[0112] In some embodiments, the charging and discharging steps include: allowing the fully charged battery to stand for 30 seconds before cyclic charging and discharging; discharging the battery at a first discharge rate of 0.05C for 10 minutes and standing for 30 seconds; and charging the battery at a fifth charge rate of 0.05C until it reaches a fully charged state.

[0113] By setting the first discharge rate to be greater than 0 and less than or equal to 0.05C, it is possible to discharge the fully charged battery with an extremely small current to simulate the formation self-discharge process to accelerate gas production, thereby reducing gas production in subsequent aging processes and reducing damage to the SEI film.

[0114] According to some embodiments of the present application, the charge and discharge steps are performed 3-5 times.

[0115] The charging and discharging steps are to discharge the fully charged battery to the second state of charge at the first discharge rate, and then recharge it to the fully charged state, wherein the number of times of repeating this step can be 3, 4 or 5. If the charging and discharging steps are performed too many times, time is wasted, and if the charging and discharging steps are performed too few times, it is not conducive to accelerating the gas production of the battery.

[0116] The number of executions of the charge and discharge steps is set to 3-5 times, which is beneficial to taking into account the formation efficiency, reducing time cost and increasing gas production, and is beneficial to reducing damage to the SEI film.

[0117] According to some embodiments of the present application, the difference between the first state of charge and the formation cut-off state of charge is greater than or equal to 2% and less than or equal to 10%. In some embodiments, the difference between the first state of charge and the formation cut-off state of charge is greater than or equal to a preset state of charge value.

[0118] The first state of charge is greater than the formation cut-off state of charge, and the difference range is 2%-10%, specifically 2%, 5%, 7% or 10%.

[0119] The difference between the first state of charge and the formation cut-off state of charge is greater than or equal to 2% and less than or equal to 10%, which is conducive to timely discharge of gas produced in the formation stage and facilitates the formation of a high-quality SEI film, thereby improving battery stability.

[0120] According to some embodiments of the present application, a value of the second state of charge is greater than or equal to 99% and less than or equal to 99.9%.

[0121] The value of the second state of charge is greater than or equal to 99% and less than or equal to 99.9%, wherein the specific value range may be 99%, 99.3%, 99.5%, 99.7% or 99.9%.

[0122] By performing cyclic charging and discharging between the second state of charge and the fully charged state, it is beneficial to accelerate the gas production process of the circulating battery, thereby reducing the gas production of the battery during the subsequent aging process, thereby reducing damage to the SEI film and increasing the cycle life of the battery.

[0123] According to some embodiments of the present application, a difference between the first state of charge and the third state of charge is greater than 0 and less than or equal to 20%.

[0124] Both the first state of charge and the third state of charge can be selected according to empirical values. In some embodiments, the value of the first state of charge is 30%, wherein the third state of charge is greater than the first state of charge, that is, the value range of the third state of charge is 30%-50%, specifically 35%, 40%, 45% or 50% can be selected. The circulating battery discharged to the third state of charge will undergo aging treatment.

[0125] The difference between the third state of charge and the first state of charge is set in a range greater than 0 and less than or equal to 20%, which is conducive to the connection with the subsequent aging process, thereby improving the battery life.

[0126] According to some embodiments of the present application, the interior of the battery is in a negative pressure exhaust state during the first charging stage, the second charging stage, and the cyclic charge and discharge stage.

[0127] The first charging stage, the second charging stage and the cyclic charge and discharge stage are all carried out in a negative pressure environment. Specifically, the negative pressure environment can be configured through external vacuum equipment (such as a negative pressure machine). In the formation stage, the internal pressure value range of the battery can be adjusted to -80±5 kilopascals (kPa).

[0128] The internal pressure of the battery in the first charging stage, the second charging stage and the cyclic charging and discharging stage is lower than the standard atmospheric pressure, which is conducive to timely discharge of gas produced in the first charging stage, the second charging stage and the cyclic charging and discharging stage, thereby reducing the risk of interface black spots and lithium precipitation.

[0129] The present application provides a battery manufacturing method, comprising performing formation on a battery to be formed using the battery formation method in the aforementioned embodiment.

[0130] In some embodiments, the battery manufacturing method includes a first charging stage, a second charging stage, a cyclic charging and discharging stage, and a discharging stage. The first charging stage includes: charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to the formation cut-off state of charge; the second charging stage includes: charging the first rechargeable battery to a fully charged state to obtain a fully charged battery; and the cyclic charging and discharging stage, performing at least one charging and discharging step to obtain a cyclic battery; the charging and discharging step includes: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging to a fully charged state; the first discharge rate is less than the minimum charging rate of the first charging stage; in the discharging stage, discharging the cyclic battery to a third state of charge; the third state of charge is greater than the first state of charge and less than the second state of charge.

[0131] After the formation stage is completed, the obtained secondary formation battery is subjected to a subsequent aging stage, and the aging is divided into room temperature aging and normal temperature aging. In some embodiments, the secondary formation battery can be placed at room temperature for aging treatment, and in other embodiments, the secondary formation battery can be placed at a maximum temperature higher than room temperature for aging treatment, for example, the aging temperature range can be 45-50 degrees Celsius, and a higher temperature can accelerate the aging reaction, thereby helping to eliminate unqualified battery products.

[0132] By adopting the battery formation method in the embodiment of the present application to form the battery to be formed, it is beneficial to reduce the risk of battery black spots and lithium precipitation, reduce damage to the SEI film, and improve the stability of the battery.

[0133] The present application provides a battery formation device, which includes a first charging component, a second charging component, a cyclic charge-discharge component, and a discharge component. The first charging component is configured to perform a first charging stage on a battery to be formed, including charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to the formation cut-off state of charge; the second charging component is configured to charge the first rechargeable battery to a fully charged state to obtain a fully charged battery; the cyclic charge-discharge component is configured to perform at least one charge and discharge step on the fully charged battery to obtain a cyclic battery; the charge and discharge step includes: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging it to a fully charged state; the first discharge rate is less than the minimum charge rate of the first charging stage; the discharge component is configured to discharge the cyclic battery to a third state of charge; the third state of charge is greater than the first state of charge and less than the second state of charge.

[0134] The first charging component, the second charging component, the cyclic charge-discharge component, and the discharge component are devices that can charge and discharge the battery, wherein the first charging component, the second charging component, and the cyclic charge-discharge component can respectively include a charging circuit, and the charging circuit includes a power source that can charge the battery; the cyclic charge-discharge component and the discharge component include a discharge circuit, and the battery can be used as a power source for external discharge. The first charging component, the second charging component, the cyclic charge-discharge component, and the discharge component can also respectively include some necessary detection elements, which can be used to detect the battery's voltage, current and other parameters during the battery charging process.

[0135] Providing a second charging component and a cyclic charge and discharge component to perform formation treatment on the battery is beneficial to forming a high-quality SEI film in the battery, thereby improving the stability of the battery.

[0136] The present application provides a battery manufacturing system, including the battery formation equipment in the aforementioned embodiment.

[0137] The battery manufacturing system is used to manufacture batteries, and the battery formation equipment is used to perform formation treatment on the batteries. In some embodiments, the battery manufacturing system also includes pre-processing equipment that can shell, weld, and package the batteries, and post-processing equipment that can age the batteries.

[0138] Using the battery manufacturing system in the embodiment of the present application to manufacture batteries is beneficial to improving the stability of the manufactured batteries, enhancing the charging and discharging performance of the batteries, and reducing the risks of battery black spots and lithium plating.

[0139] The battery formation method of the present application is described below in conjunction with a specific embodiment. Figure 3-Figure 6 As shown, the method includes:

[0140] S310, first charging stage: adopt negative pressure formation process, connect with negative pressure machine through battery cell injection port, adjust internal pressure value of battery cell to be formed to -80±5kPa, let stand for 10s; adopt constant current charging mode with second charging ratio of 0.2C to charge battery to 1% SOC to quickly reach SEI film forming potential, charging time is 3min, let stand for 30s; adopt constant current charging mode with third charging ratio of 0.1C to increase state of charge of battery by 2.5% SOC, wherein charging time is 15min, let stand for 30s to discharge generated gas; repeat the steps of increasing state of charge of battery by 2.5% SOC and let stand for the third charging ratio, until state of charge of battery to be formed satisfies expression: 1%+n×2.5%≥S, wherein S is state of charge at formation cut-off, and in this embodiment, state of charge at formation cut-off S is 25%.

[0141] Then, a constant current charging mode with a charging rate of 0.5C is used to make the battery charge state reach the first charge state, and a first rechargeable battery is obtained. The first charge state is 30%, and it is left to stand for 30s, where the charging time is T1, and T1 satisfies the expression:

[0142] S320, the second charging stage, including:

[0143] The first rechargeable battery is constant-current charged at a fourth charging rate of 1C until the voltage of the first rechargeable battery reaches an upper limit of the charging voltage, and the first rechargeable battery is constant-voltage charged to a fully charged state at a charging rate of 0.05C to obtain a fully charged battery.

[0144] S330, in the cyclic charge and discharge stage, at least one charge and discharge step is performed to obtain a cyclic battery; the charge and discharge step includes:

[0145] Let the fully charged battery rest for 30 seconds before cyclic charging and discharging;

[0146] The battery was discharged at a constant current at a first discharge rate of 0.05C for 10 minutes and allowed to stand for 30 seconds.

[0147] The battery is charged at a constant current of the fifth charging rate of 0.05C until it reaches a full charge state.

[0148] S340, discharge phase: discharge the battery to 50% SOC at a discharge rate of 1C.

[0149] Through the above-mentioned formation process, the quality of SEI film formation in the battery cell can be improved, and the gas by-products can be more effectively discharged from the battery cell in combination with the negative pressure process.

[0150] For further explanation, the battery formed by the battery formation method described in the above embodiment can be used as Battery 1 for comparison with Battery 2 formed by a conventional formation method. Battery 1 and Battery 2 are battery cells of the same batch produced by the same production line, and both use graphite negative electrodes.

[0151] The formation method of the battery 2 is as follows: providing a battery to be formed that is the same as the battery 1, connecting the liquid injection port of the battery to a negative pressure machine, adjusting the internal pressure value of the battery to -80±5kPa, and standing for 10s; charging the battery to a formation cut-off state of charge S using a constant current charging mode with a charging rate of 0.2C, and then charging the battery to a first state of charge, i.e., 30%, at a charging rate of 0.5C, to obtain the formed battery 2.

[0152] Figure 7 The graph of the change of gas production volume over time during the high temperature aging process of Battery 1 and Battery 2 is shown. It can be seen that under the same time, the gas production volume of Battery 1 during the high temperature aging process is significantly smaller than that of Battery 2. Therefore, the battery formation method in the embodiment of the present application can effectively improve the quality of SEI film formation, reduce the risk of black spots and lithium precipitation on the battery interface, and improve the cycle life of the battery.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery formation method, characterized in that: include: The battery to be formed is charged to a fully charged state to obtain a fully charged battery; In the cyclic charge and discharge stage, at least one charge and discharge step is performed to obtain a cyclic battery; The charging and discharging step includes: discharging the fully charged battery to a second state of charge at a first discharge rate, and then recharging to a fully charged state; the first discharge rate is greater than 0 and less than or equal to 0.05C; In the discharge stage, the cycle battery is discharged to a third state of charge; the third state of charge is less than the second state of charge.

2. The battery formation method according to claim 1, characterized in that: The charging of the battery to be formed to a fully charged state to obtain a fully charged battery comprises: The first charging stage includes: charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; a SEI film has been formed in the first rechargeable battery; The second charging stage includes: charging the first rechargeable battery to a fully charged state to obtain the fully charged battery.

3. The battery formation method according to claim 1, characterized in that: The charging of the battery to be formed to a fully charged state to obtain a fully charged battery comprises: The first charging stage includes: charging the battery to be formed to obtain a first rechargeable battery with a first state of charge; the first state of charge is greater than or equal to 15% and less than 100%; The second charging stage includes: charging the first rechargeable battery to a fully charged state to obtain the fully charged battery.

4. The battery formation method according to claim 2 or 3, characterized in that: The first state of charge is greater than or equal to 15% and less than or equal to 30%.

5. The battery formation method according to claim 2 or 3, characterized in that: The first state of charge is greater than or equal to the formation cut-off state of charge, and the formation cut-off state of charge is determined according to the following steps: Providing an experimental battery to be formed that is the same as the battery to be formed; The experimental battery is charged at a constant current until the experimental battery is charged to an upper charging limit voltage, and the gas production flow rate of the experimental battery during the charging process is detected; The formation cut-off state of charge is determined according to the gas production flow rate and the corresponding charging capacity of the experimental battery during the charging process.

6. The battery formation method according to claim 5, characterized in that: The charging rate of the constant current charging of the experimental battery is greater than 0 and less than or equal to 0.05C.

7. The battery formation method according to claim 5, characterized in that: Determining the formation cut-off state of charge according to the gas production flow rate and the corresponding charging capacity of the experimental battery during the charging process includes: Determine the gas production cut-off charge state according to the charging capacity corresponding to when the gas production flow rate of the experimental battery drops to a preset flow rate threshold and the design capacity of the experimental battery; The formation cut-off state of charge is determined according to the gas production cut-off state of charge, wherein the formation cut-off state of charge is greater than the gas production cut-off state of charge.

8. The battery formation method according to claim 7, characterized in that: The difference between the formation cut-off state of charge and the gas generation cut-off state of charge is less than or equal to 5%.

9. The battery formation method according to claim 5, characterized in that: The difference between the first state of charge and the formation cut-off state of charge is greater than or equal to 2% and less than or equal to 10%.

10. The battery formation method according to claim 5, characterized in that: The first state of charge is greater than the formation cut-off state of charge, and the first charging stage includes: The first charging sub-stage includes: constant current charging the battery to be formed until the state of charge of the battery to be formed reaches the formation cut-off state of charge; The second charging sub-stage includes: constant current charging the battery to be formed that has completed the first charging sub-stage until the state of charge of the battery to be formed reaches the first state of charge, thereby obtaining the first rechargeable battery; The maximum charging rate of the first charging sub-stage is less than the minimum charging rate of the second charging sub-stage.

11. The battery formation method according to claim 10, characterized in that: The first charging sub-stage includes: Constant current charging the battery to be formed at a second charging rate until the state of charge of the battery to be formed reaches a fourth state of charge; and Repeat the following steps until the state of charge of the battery to be formed is greater than or equal to the formation cut-off state of charge: charging the battery to be formed with a constant current for a first preset time period at a third charging rate that is less than the second charging rate, so that the state of charge of the battery to be formed increases by a preset state of charge value; Wait for the second preset time.

12. The battery formation method according to claim 2 or 3, characterized in that: The second charging stage includes: charging the first rechargeable battery at a constant current until the voltage of the first rechargeable battery reaches an upper charging voltage limit; and The first rechargeable battery reaching the upper limit of the charging voltage is charged at a constant voltage to a fully charged state to obtain the fully charged battery.

13. The battery formation method according to claim 12, characterized in that: The step of charging the first rechargeable battery with a constant current until the voltage of the first rechargeable battery reaches an upper charging voltage limit includes: constant current charging the first rechargeable battery at a fourth charging rate until the voltage of the first rechargeable battery reaches an upper charging voltage limit; The fourth charging rate is greater than the maximum charging rate in the first charging stage.

14. The battery formation method according to any one of claims 1 to 3, characterized in that: The charging and discharging steps include: Let stand for a third preset time; Discharging the fully charged battery at a first discharge rate to the second state of charge; Let stand for a fourth preset time period; Constant current charging the fully charged battery at a fifth charging rate until it is fully charged; Wherein, the first discharge rate is greater than 0 and less than or equal to 0.05C.

15. The battery formation method according to any one of claims 1 to 3, characterized in that: The charging and discharging steps are performed 3-5 times.

16. The battery formation method according to any one of claims 1 to 3, characterized in that: The value of the second state of charge is greater than or equal to 99% and less than or equal to 99.9%.

17. The battery formation method according to claim 2 or 3, characterized in that: A difference between the first state of charge and the third state of charge is greater than 0 and less than or equal to 20%.

18. The battery formation method according to claim 2 or 3, characterized in that: The interior of the battery is in a negative pressure exhaust state during the first charging stage, the second charging stage and the cyclic charge and discharge stage.

19. A method for manufacturing a battery, characterized in that: include: The battery to be formed is formed according to the battery formation method according to any one of claims 1 to 18.

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