Battery formation method, battery manufacturing method, battery formation equipment and battery manufacturing system

Abstract

The invention provides a battery formation method, a battery manufacturing method, battery formation equipment and a battery manufacturing system, and belongs to the technical field of batteries. The battery formation method comprises the following steps: carrying out primary formation charging on a to-be-formed battery until a primary formation battery with a first charge state is obtained; discharging the primarily formed battery to a discharge lower limit voltage at a first discharge rate to obtain a discharge battery; the first discharge rate is greater than the maximum charge rate of the initial formation stage; performing secondary formation charging on the discharge battery until a secondary formation battery with a second charge state is obtained; sealing an exhaust port of the secondary formation battery; in the primary formation stage, the discharge stage and the secondary formation stage, the interior of the battery can be exhausted through the exhaust port. Therefore, by setting the discharge stage and the secondary formation stage, the SEI film forming quality is improved, and the service life of the battery is prolonged.

Description

[0001] This application is a divisional application of Chinese patent application No. 202411413834.5, with the 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 in energy conservation and environmental protection. For electric vehicles, battery technology is an important factor in 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] An embodiment of the first aspect of the present application provides a battery formation method, the battery formation method comprising: a primary formation stage, comprising: performing primary formation on a battery to be formed to obtain a primary formed battery with a first state of charge; the first state of charge is greater than or equal to a formation cut-off state of charge; a discharge stage, comprising: discharging the primary formed battery at a first discharge rate constant current until the voltage of the primary formed battery reaches a discharge lower limit voltage to obtain a discharge battery; the first discharge rate is greater than the maximum charge rate in the primary formation stage; a secondary formation stage, comprising: performing secondary formation on the discharge battery to obtain a secondary formed battery with a second state of charge, the second state of charge is greater than or equal to the formation cut-off state of charge; and sealing an exhaust port of the secondary formed battery; wherein the interior of the battery can be exhausted through the exhaust port in the primary formation stage, the discharge stage, and the secondary formation stage.

[0007] In the technical scheme of the embodiment of the present application, some gas side reactions will be generated during the first charge and discharge process of the lithium-ion battery. The gas side reactions will affect the film-forming quality of the SEI film. If the gas side reaction products 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 arranging the discharge and second formation stages after the initial formation stage, not only can the gas be discharged as much as possible, reducing the risk of interface black spots and lithium precipitation, but it is also conducive to forming a high-quality SEI film, thereby improving the cycle life of the battery. In addition, by discharging the initial formation battery with a first discharge rate greater than the maximum charge rate of the initial formation stage, more heat can be generated in a short time to increase the temperature inside the battery, thereby reducing the surface tension of the electrolyte, making it easier for the internal bubbles to detach from the electrode sheet interface, which is conducive to the discharge of bubbles inside the electrode assembly, especially in the middle position of the electrode assembly, such as the center of the electrode assembly winding.

[0008] In some embodiments, the first discharge rate is greater than or equal to 1 C and less than or equal to 3 C. Thus, the exhaust effect can be improved and the formation time can be reduced, thereby saving costs, accelerating the formation process speed, and improving the formation efficiency.

[0009] In some embodiments, the discharge stage further includes leaving the discharged battery to exhaust gas after the discharge is completed. All residual gas in the battery can be fully discharged by leaving the battery to exhaust gas, thereby improving the quality of SEI film formation.

[0010] In some embodiments, the time for the discharged battery to be left to exhaust is greater than or equal to 30 minutes and less than or equal to 4 hours. Thus, by setting the third preset time to be greater than or equal to 30 minutes and less than or equal to 4 hours, it is beneficial for the gas in the battery to be fully discharged, and the formation efficiency is improved, and the cost is reduced.

[0011] In some embodiments, the first state of charge is greater than the formation cut-off state of charge, and the initial formation stage includes a first charging stage and a second charging stage. The first charging stage includes: 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; the second charging stage includes: 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 an initial formation battery; wherein the charging rate of the first charging stage is less than the charging rate of the second charging stage. By setting the first charging stage and the second charging stage in the initial formation stage, and the charging rate of the first charging stage is less than the charging rate of the second charging stage, it is beneficial to improve the SEI film formation quality, reduce the time of the initial formation stage, and improve the formation efficiency.

[0012] In some embodiments, the first charging stage includes: constant current charging of the battery to be formed at a first charging rate until the state of charge of the battery to be formed reaches a third 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 of the battery to be formed at a 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 forming a high-quality SEI film and improving the cycle life and formation efficiency of the battery.

[0013] In some embodiments, the formation cut-off state of charge is determined according to the following stages: 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 an upper charging limit voltage; and determining the formation cut-off state of charge according to the correlation between the gas production flow rate and the charging capacity of the experimental battery during the charging process. Determining the formation cut-off state of charge by the correlation between the gas production flow rate and the 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 improving the SEI film formation quality.

[0014] In some embodiments, the constant current charging rate of the experimental battery 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.

[0015] In some embodiments, according to the correlation between the gas production flow rate and the charging capacity of the experimental battery during the charging process, determining the formation cut-off state of charge includes: determining the gas production cut-off state of charge according to the charging capacity corresponding to the gas production flow rate of the experimental battery when it 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 or equal to 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.

[0016] In some embodiments, the charging method in the secondary formation stage is the same as the charging method in the primary formation stage. The charging method in the secondary formation stage is the same as the charging method in the primary formation stage, which is beneficial to improving the formation quality, improving the SEI film formation quality, and thus improving the battery stability.

[0017] In some embodiments, the second state of charge is greater than the formation cut-off state of charge, and the secondary formation stage includes: the third charging stage: constant current charging of the discharge battery until the state of charge of the discharge battery is greater than or equal to the formation cut-off state of charge; the fourth charging stage: constant current charging of the discharge battery until the state of charge of the discharge battery reaches the second state of charge, thereby obtaining a secondary formation battery; wherein the charging rate of the third charging stage is less than the charging rate of the fourth charging stage. By setting the third charging stage and the fourth charging stage in the secondary formation stage, and the charging rate of the third charging stage is less than the charging rate of the fourth charging stage, it is beneficial to improve the SEI film formation quality, reduce the time of the secondary formation stage, and improve the formation efficiency.

[0018] In some embodiments, the first state of charge is equal to the second state of charge, and 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%. 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.

[0019] In some embodiments, the internal pressure of the battery in the primary formation stage, the discharge stage, and the secondary formation stage is less than the standard atmospheric pressure. This is conducive to timely discharge of the gas produced in the primary formation stage, the discharge stage, and the secondary formation stage, thereby reducing the risk of interface black spots and lithium precipitation.

[0020] 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.

[0021] The embodiment of the third aspect of the present application provides a battery formation device, the battery formation device includes a primary formation component, a discharge component and a secondary formation component. The primary formation component is configured to perform a primary formation stage, including: performing a primary formation on the battery to be formed, to obtain a primary formation 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 discharge component is configured to perform a discharge stage, including: discharging the primary formation battery at a first discharge rate constant current until the voltage of the primary formation battery reaches the discharge lower limit voltage, to obtain a discharge battery; the first discharge rate is greater than the maximum charge rate of the primary formation stage; the secondary formation component is configured to perform a secondary formation stage, including: performing a secondary formation on the discharge battery, to obtain a secondary formation battery with a second state of charge, the second state of charge is greater than or equal to the formation cut-off state of charge; the sealing component is configured to seal the exhaust port of the secondary formation battery; wherein, the battery can be exhausted through the exhaust port in the primary formation stage, the discharge stage and the secondary formation stage. Providing a discharge component and a secondary formation 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.

[0022] In some embodiments, the secondary formation components are obtained by reusing the primary formation components. Therefore, in the battery formation process, only one set of primary formation components is needed to complete the production of the primary formation battery and the secondary formation battery, saving costs.

[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 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 an interface diagram of the anode electrode of a battery 1 obtained by using the battery formation method of some embodiments of the present application;

[0033] Figure 8 This is the interface diagram of the anode electrode of the second battery obtained by conventional formation method;

[0034] Fig. 9 The graphs are the change in cycle number and battery health status of battery one and battery two.

[0035] Description of reference numerals:

[0036] Vehicles 1000;

[0037] Battery 100, controller 200, motor 300;

[0038] Box body 10, first part 11, second part 12;

[0039] Battery cell 20;

[0040] Experimental battery 30 , gas conduit 31 , gas test flow meter 32 , flow meter outlet 33 . DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] During the first charge and discharge process of the battery, some gas side reactions will also be produced, which will affect the quality of the SEI film. Taking lithium batteries as an example, during the formation process, the formation of the SEI film and side reactions will produce gases, including C 2 H 4 Hydrocarbon gases and CO 2 , H 2 And other inorganic gases. If the generated gaseous side reactants cannot be removed in time, it will not only affect the film quality of the SEI film, but also may cause the risk of interface black spots and lithium precipitation, thereby affecting the cycle life and stability of the battery. In order to discharge the gas generated during formation, in some embodiments, pre-formation can be carried out with the battery open, the generated gas is discharged, and then the battery is sealed before continuing the formation. However, it is impossible to completely discharge the bubbles simply by relying on negative pressure suction, because the battery pole piece will expand after charging, which will cause the gap between the graphite particles in the negative pole piece to become smaller, and the interface gap between the positive and negative electrodes to become smaller, which causes some gas to remain at the interface and cannot be discharged, and new gas will still be generated during the charging process after sealing, and there is still a risk of interface black spots and lithium precipitation.

[0053] Based on the above considerations, the embodiment of the present application proposes a battery formation method, which includes a primary formation stage: the battery to be formed is initially formed to obtain a primary formation 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 discharge stage: the primary formation battery is discharged to the discharge lower limit voltage to obtain a discharge battery; the secondary formation stage: the discharge battery is secondary formed to obtain a secondary formation battery with a second state of charge, and the second state of charge is greater than or equal to the formation cut-off state of charge. Therefore, by setting the discharge stage and the secondary formation stage, it is possible to achieve a more thorough removal of the gas generated in the formation stage, improve the SEI film formation quality, and thus improve the cycle life of the battery.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Please refer to Figure 1 , Figure 1 A 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] See also Figure 3-Figure 9 , Figure 3 This is one of the flow charts of the battery formation method according to some embodiments of the present application; Figure 4 A flowchart of the first charging stage of some embodiments of the present application; Figure 5 This is a second flow chart of a battery formation method according to some embodiments of the present application; Figure 6 A schematic diagram of confirming the cut-off state of charge of some embodiments of the present application; Figure 7 This is an interface diagram of the anode electrode of a battery 1 obtained by using the battery formation method of some embodiments of the present application; Figure 8This is the interface diagram of the anode electrode of the second battery obtained by conventional formation method; Fig. 9 The graphs are the change in cycle number and battery health status of battery one and battery two.

[0063] The present application embodiment provides a battery formation method, such as Figure 3 As shown, the method includes:

[0064] S310, initial formation stage, including: performing initial formation on the battery to be formed to obtain an initial formed 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;

[0065] S320, a discharge phase, comprising: discharging the initially formed battery at a first discharge rate at a constant current until the voltage of the initially formed battery reaches a lower discharge limit voltage, thereby obtaining a discharged battery; the first discharge rate being greater than the maximum charge rate in the initial formation phase;

[0066] S330, a secondary formation stage, comprising: performing secondary formation on the discharged battery to obtain a secondary formed battery with a second state of charge, wherein the second state of charge is greater than or equal to the formation cut-off state of charge;

[0067] S340, closing the exhaust port of the secondary formation battery; wherein, the battery interior can be vented through the exhaust port during the primary formation stage, the discharge stage and the secondary formation stage.

[0068] 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.

[0069] 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 and the second state of charge can be selected based on experience. The state of charge value greater than or equal to the formation cutoff state of charge.

[0070] 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%.

[0071] In the initial formation 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 at 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.

[0072] The lower discharge voltage limit is usually defined as the value at which the battery must stop discharging when the voltage drops to this value to avoid irreversible damage to the battery. The lower discharge voltage limit is also called the cut-off discharge voltage. When the battery voltage is less than or equal to this voltage value, the battery can be considered to be fully discharged. This voltage value is not fixed, but will change with factors such as load, temperature, and battery aging. For example, in some lithium batteries, the lower discharge voltage limit can be set at 2.75V.

[0073] In S320, the discharge mode of the initial formation battery can be constant voltage discharge, constant current discharge or a combination of the two. During the discharge process, the battery pole piece will shrink, which will cause the gap between the graphite particles in the negative pole piece to become larger, and the interface gap between the positive and negative poles to become larger, so that the gas previously remaining in the interface can escape and be discharged. In addition, the use of a larger first discharge rate for discharge can generate heat more quickly during the discharge process, thereby increasing the internal temperature of the battery. The increase in temperature can reduce the surface tension of the electrolyte in the pole piece, which is further conducive to the internal bubbles from the pole piece interface. The gas generated inside the electrode assembly is easier to discharge. In some embodiments, the first discharge rate is at least 0.1C-0.5C greater than the maximum charge rate in the initial formation stage. For example, if the maximum charge rate in the initial formation stage is 0.5C, the first discharge rate can be 0.6C-1C or even greater.

[0074] In S330, the secondary formation stage may be the same as or different from the primary formation stage. The values ​​of the second state of charge and the first state of charge may be the same or different. In some embodiments, the second state of charge may be the same as the first state of charge and both are in the range of 15%-30%. In the secondary formation stage, the SEI film that has been basically formed in the primary formation will undergo another film forming process, so that the previously formed SEI film can be repaired, the quality of the SEI film can be improved, and the risk of interface black spots and lithium precipitation can be reduced.

[0075] In S340, the exhaust port can be a through hole opened in the battery housing or shell for exhaust. In some implementations, the injection port can be reused as an exhaust port, and the negative pressure machine and the injection port are connected by a pipeline to achieve the discharge of gas inside the battery. Among them, the gas generated by the battery in the primary formation stage, the discharge stage and the secondary formation stage can be discharged in time through the exhaust port. It is understandable that when the injection port is reused as an exhaust port, the electrolyte can be added to the inside of the battery housing through the injection port before the injection port is closed.

[0076] During the first charge and discharge process of lithium-ion batteries, some gas side reactions will occur, which will affect the film quality of the SEI film. If the generated gas side reactions 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 discharge and second formation stages after the initial formation stage, not only can the gas be discharged as much as possible, reducing the risk of interface black spots and lithium precipitation, but it is also conducive to the formation of a high-quality SEI film, thereby improving the cycle life of the battery. In addition, by discharging the initial formation battery with a first discharge rate that is greater than the maximum charge rate of the initial formation stage, more heat can be generated in a short time to increase the temperature inside the battery, and the surface tension of the electrolyte in the pole piece can be reduced, making it easier for the internal bubbles to detach from the pole piece interface, which is conducive to the discharge of bubbles inside the electrode assembly, especially in the middle of the electrode assembly, such as the center of the winding of the electrode assembly.

[0077] 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 initial formation stage includes a first charging stage and a second charging stage. The first charging stage includes: 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; the second charging stage includes: 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 an initial formation battery; wherein the charging rate of the first charging stage is less than the charging rate of the second charging stage.

[0078] 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 charging rate of the first charging stage is less than the charging rate of the second charging stage. In some embodiments, the charging rate of the second charging stage may be 2-5 times the charging rate of the first charging stage. In this embodiment, the initial formation 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 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 stage can save process time.

[0079] In some embodiments, the first charging stage and the second charging stage may each include one or more charging sub-stages. Two adjacent charging stages or charging sub-stages may be left to stand for a certain period of time to help the chemical reaction inside the battery reach equilibrium and promote uniform formation of the SEI film.

[0080] By setting the first charging stage and the second charging stage in the initial formation stage, and the charging rate of the first charging stage is smaller than the charging rate of the second charging stage, it is beneficial to improve the SEI film formation quality, reduce the time of the initial formation stage, and improve the formation efficiency.

[0081] According to some embodiments of the present application, Figure 4 As shown, the first charging stage includes:

[0082] S410, constant current charging the battery to be formed at a first charging rate until the state of charge of the battery to be formed reaches a third state of charge;

[0083] 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:

[0084] S421, constant current charging the battery to be formed at a second charging rate for a first preset time period, so that the state of charge of the battery to be formed increases by a preset state of charge value;

[0085] S422: Wait for a second preset time period.

[0086] The third charge state in S410 may be a charge state corresponding to the film formation potential of the SEI film. In some embodiments, the third charge state may range from 1% to 15%, for example, the third charge state may be 1%. The first charge rate may be greater than the second charge rate, so that the film formation potential of the SEI film can be reached more quickly.

[0087] 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%.

[0088] In some embodiments, Figure 5 As shown, a negative pressure formation process can be used in the initial formation stage, and the battery cell injection port is connected to a negative pressure machine, and the internal pressure value of the battery cell is adjusted to -80±5 kilopascals (kPa), and it is left to stand for 10 seconds; a constant current charging mode with a first charging ratio of 0.2C is used 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; a constant current charging mode with a second charging ratio of 0.1C is used 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; the aforementioned second charging ratio is repeated to increase the battery's state of charge by 2.5% SOC and the step of standing, 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 second charging rate is used to increase the battery state of charge by 2.5% SOC and then the battery is left to stand.

[0089] 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:

[0090]

[0091] The first charging stage is the key stage of SEI film formation. The first charging stage is divided into multiple charging sub-stages, and appropriate charging rates and standing times after charging are set for different charging sub-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.

[0092] According to some embodiments of the present application, the formation cut-off state of charge is determined according to the following stages: 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 an upper charging limit voltage; determining the formation cut-off state of charge based on the correlation between the gas production flow rate and the charging capacity of the experimental battery during the charging process.

[0093] 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.

[0094] The formation cut-off state of charge is determined based on the correlation between the gas production flow rate and the 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 correlation between the gas production flow rate and the charging capacity, and the formation cut-off state of charge is determined based on the correlation. 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.

[0095] During the charging process, negative pressure can be used to discharge and detect the gas generated inside the experimental battery. Figure 6 In the example, the gas test flowmeter 32 detects the gas flow rate of the experimental battery. The gas conduit 31 connects the experimental battery 30 with the gas test flowmeter 32, and the battery injection port is welded to the gas production nail to fix it. 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 correlation between the gas production flow rate and the charging capacity of the experimental battery can be obtained.

[0096] By testing the correlation between the gas production flow rate and the charging capacity of the battery during the charging process to determine the formation cut-off state of charge, it is beneficial to reasonably and accurately determine the formation cut-off state of charge, which is beneficial to improve the formation efficiency and improve the quality of SEI film formation.

[0097] 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.

[0098] 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.

[0099] 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 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.

[0100] 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.

[0101] 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.

[0102] According to some embodiments of the present application, determining the formation cut-off state of charge according to the correlation between the gas production flow rate and the 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 the gas production flow rate of the experimental battery when it 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 or equal to the gas production cut-off state of charge.

[0103] 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.

[0104] 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.

[0105] The formation cut-off state of charge is greater than or equal to 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 added preset margin is 0%-5% SOC, and specifically 1%, 2%, 3%, 4% or 5% can be selected.

[0106] 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.

[0107] According to some embodiments of the present application, the first discharge rate is greater than or equal to 1C and less than or equal to 3C.

[0108] In the discharge stage, the first discharge rate is used to perform constant current discharge on the primary formation battery. In some embodiments, the first discharge rate can be 1C, 1.5C, 2C, 2.5C or 3C. By setting the first discharge rate to be greater than or equal to 1C and less than or equal to 3C, the exhaust effect can be improved and the formation time can be reduced, thereby saving costs, accelerating the formation process speed, and improving the formation efficiency.

[0109] According to some embodiments of the present application, the discharge stage further includes leaving the discharged battery to stand and exhaust gas after the discharge is completed.

[0110] During the discharge process, the change in the internal gap of the battery causes the residual gas in the initial formation stage to escape. The gas can be discharged as much as possible by standing still. The static exhaust can be achieved by negative pressure suction.

[0111] By letting the exhaust stand still, all the residual gas in the battery can be fully discharged, thereby improving the quality of SEI film formation.

[0112] According to some embodiments of the present application, the static exhaust time of the discharge battery is greater than or equal to 30 minutes and less than or equal to 4 hours.

[0113] After the initial formation stage, the battery to be formed will enter the discharge stage. During the discharge process, it will be left to exhaust gas. The duration of the static exhaust gas needs to be set in a certain interval. If the duration is too short, it is not conducive to the battery to fully exhaust the internal gas. If the duration is too long, it will consume too much time and increase the formation cost. Therefore, by setting the static exhaust gas duration of the discharged battery to be greater than or equal to 30 minutes and less than or equal to 4 hours, it is conducive to the full exhaust of gas in the battery, and the formation efficiency is improved and the cost is reduced.

[0114] According to some embodiments of the present application, the charging method in the secondary formation stage is the same as the charging method in the primary formation stage.

[0115] The secondary formation stage may include multiple charging stages, and the charging stages may be performed discontinuously. In some embodiments, the secondary formation stage is divided into two charging stages: stage one, the discharge battery after discharge is charged at a constant current until the charge state of the discharge battery is greater than or equal to the charge state at the end of formation; stage two, the discharge battery is charged at a constant current until the charge state of the discharge battery reaches the same first charge state as in the primary formation stage to obtain a secondary formation battery; wherein the charging rate of the charging stage of stage one is less than the charging rate of the charging stage of stage two.

[0116] In some embodiments, stage one in the secondary formation stage also includes: constant current charging the discharge battery using the same first charging rate as the primary formation stage until the charge state of the discharge battery reaches the same third charge state as the primary formation stage, and constant current charging the discharge battery using the same second charging rate as the primary formation stage, wherein the constant current charging duration is a first preset duration so that the charge state of the discharge battery increases to the same preset charge state value as the primary formation stage, and then standing for the same second preset time as in the primary formation stage, and cyclically executing the process of constant current charging at the second charging rate and the process of standing for the second preset time until the charge state of the discharge battery is greater than or equal to the formation cut-off charge state.

[0117] The charging method in the secondary formation stage is the same as that in the primary formation stage, which is beneficial to improving the formation quality and the SEI film formation quality, thereby improving the battery stability.

[0118] According to some embodiments of the present application, the second state of charge is greater than the formation cut-off state of charge, and the secondary formation stage includes: a third charging stage: constant current charging of the discharge battery until the state of charge of the discharge battery is greater than or equal to the formation cut-off state of charge; a fourth charging stage: constant current charging of the discharge battery until the state of charge of the discharge battery reaches the second state of charge, thereby obtaining a secondary formation battery; wherein the charging rate of the third charging stage is less than the charging rate of the fourth charging stage.

[0119] The charging rate of the third charging stage ranges from 0.1C to 0.3C, and can be specifically 0.1C, 0.2C or 0.3C. In some embodiments, the charging rate of the fourth charging stage can be 0.1C-0.5C greater than the charging rate of the third charging stage. For example, when the charging rate of the third charging stage is 0.2C, the charging rate of the fourth charging stage ranges from 0.3C to 0.7C, and can be specifically 0.3C, 0.4C, 0.5C, 0.6C or 0.7C.

[0120] The formation stage of the SEI film is mainly concentrated in the primary formation stage, and the secondary formation stage is conducive to stabilizing the SEI film. In some embodiments, the charging rate of the third charging stage is greater than or equal to the charging rate of the first charging stage, and the charging rate of the fourth charging stage is greater than or equal to the charging rate of the second charging stage. In some embodiments, if the charging rate of the first charging stage is 0.1C, the charging rate of the third charging stage is in the range of 0.1C-0.3C, specifically 0.1C, 0.2C or 0.3C; if the charging rate of the second charging stage is 0.3C, the charging rate of the fourth charging stage is in the range of 0.3C-0.6C, specifically 0.3C, 0.4C, 0.5C, or 0.6C.

[0121] In some embodiments, the charging stages in the third charging stage and the fourth charging stage may be discontinuous charging, for example, there may be a certain period of rest between the third charging stage and the fourth charging stage.

[0122] In some embodiments, after the discharge stage, the discharged battery is left to stand for 10 seconds before entering the secondary formation stage, specifically, the battery is charged at a constant current at a charging rate of 0.2C, and the charging time is T2 to satisfy: Then let it stand for 30 seconds, and then charge the battery to 30% SOC at a charging rate of 0.5C, where the charging time T3 meets the following requirements:

[0123] By setting the third charging stage and the fourth charging stage in the secondary formation stage, and the charging rate of the third charging stage is smaller than the charging rate of the fourth charging stage, it is beneficial to improve the SEI film formation quality, reduce the time of the secondary formation stage, and improve the formation efficiency.

[0124] According to some embodiments of the present application, the first state of charge is equal to the second state of charge, and the difference between the first state of charge and the formation-cutoff state of charge is greater than or equal to 2% and less than or equal to 10%.

[0125] 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%. In some embodiments, if the formation cut-off state of charge is 25%, the first state of charge and the second state of charge can be the same and the value range is 27%-35%, specifically 27%, 30%, 32% or 35%. 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 the preset state of charge value.

[0126] 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.

[0127] According to some embodiments of the present application, the internal pressure of the battery in the primary formation stage, the discharge stage, and the secondary formation stage is less than the standard atmospheric pressure.

[0128] The primary formation stage, the discharge stage and the secondary formation 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).

[0129] The internal pressure of the battery in the primary formation stage, the discharge stage and the secondary formation stage is lower than the standard atmospheric pressure, which is conducive to timely discharge of the gas produced in the primary formation stage, the discharge stage and the secondary formation stage, thereby reducing the risk of interface black spots and lithium precipitation.

[0130] 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.

[0131] In some embodiments, the formation stages included in the battery manufacturing method include a primary formation stage, a discharge stage, and a secondary formation stage. The primary formation stage: the battery to be formed is subjected to primary formation to obtain a primary formed 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 discharge stage: the primary formed battery is discharged to a discharge lower limit voltage to obtain a discharge battery; the secondary formation stage: the discharge battery is subjected to secondary formation to obtain a secondary formed battery with a second state of charge, the second state of charge is greater than or equal to the formation cut-off state of charge.

[0132] 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.

[0133] 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, improve the quality of SEI film formation, and enhance the stability of the battery.

[0134] The present application provides a battery formation device, which includes a primary formation component, a discharge component and a secondary formation component. The primary formation component is configured to perform primary formation on a battery to be formed, and obtain a primary formation 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 discharge component is configured to discharge the primary formation battery at a first discharge rate constant current until the voltage of the primary formation battery reaches the discharge lower limit voltage, and obtain a discharge battery; the first discharge rate is greater than the maximum charge rate in the primary formation stage; the secondary formation component is configured to perform secondary formation on the discharge battery, and obtain a secondary formation battery with a second state of charge, and the second state of charge is greater than or equal to the formation cut-off state of charge; the sealing component is configured to seal the exhaust port of the secondary formation battery; wherein, the battery can be exhausted through the exhaust port in the primary formation stage, the discharge stage and the secondary formation stage.

[0135] The primary formation component, the discharge component and the secondary formation component are devices that can charge and discharge the battery, wherein the primary formation component and the secondary formation component can respectively include a charging circuit, and the charging circuit includes a power source that can charge the battery; the discharge component includes a discharge circuit, and the battery can be used as a power source for external discharge. The primary formation component, the discharge component and the secondary formation component can also respectively include some necessary detection elements, which can be used to detect the voltage, current and other parameters of the battery during the battery charging process. In some embodiments, the closure component can close the exhaust port reused by the injection port.

[0136] Providing a discharge component and a secondary formation 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.

[0137] According to some embodiments of the present application, the secondary formation component is obtained by reusing the primary formation component.

[0138] The secondary formation component is reused as the primary formation component, that is, the two are the same set of formation components, and the battery can be charged in the primary formation stage and the secondary formation stage respectively. In some embodiments, the first state of charge and the second state of charge are equal, and the charging method in the secondary formation stage is exactly the same as the charging method in the primary formation stage.

[0139] During the battery formation process, only one set of primary formation components is needed to complete the production of primary formation batteries and secondary formation batteries, which can save costs.

[0140] The present application provides a battery manufacturing system, including the battery formation equipment in the aforementioned embodiment.

[0141] 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.

[0142] 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.

[0143] 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:

[0144] S310, initial formation stage: adopt negative pressure formation process, connect to 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 first 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 second 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 aforementioned second 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%.

[0145] Then, a constant current charging mode with a charging rate of 0.5C is used to make the battery's state of charge reach the first state of charge, and the first formation battery is obtained. The first state of charge is 30%, and it is left to stand for 30s, where the charging time is T1, and T1 satisfies the expression:

[0146] S320, discharge stage: discharging the initially formed battery to a discharge lower limit voltage to obtain a discharge battery; including:

[0147] Discharge to the lower limit voltage of discharge in a constant current mode with a first discharge rate of 1C. During the discharge stage, the negative pressure state in the initial formation stage is maintained. Then, the battery is allowed to stand to ensure that all residual gas can be effectively discharged. The standing time can be greater than or equal to 30 minutes.

[0148] S330, secondary formation stage: secondary formation of the discharged battery to obtain a secondary formation battery with a second state of charge, the second state of charge being greater than or equal to the formation cut-off state of charge; comprising:

[0149] Let the discharged battery rest for 10 seconds before charging;

[0150] The third charging stage: the battery is charged at a constant current at a charging rate of 0.2C for a charging time of T2, until the state of charge of the discharged battery is greater than or equal to the formation cut-off state of charge S; that is, the charging time T2 satisfies:

[0151]

[0152] Let the battery sit for 30 seconds.

[0153] The fourth charging stage: the battery is charged at a constant current of 0.5C to the second state of charge, wherein the second state of charge is 30%, the charging time is T3, and the battery meets the following conditions:

[0154] S340, closing the exhaust port of the secondary formation battery; wherein, the battery interior can be vented through the exhaust port during the primary formation stage, the discharge stage and the secondary formation stage.

[0155] Through the above-mentioned formation process, the SEI molding quality 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.

[0156] 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.

[0157] 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.

[0158] like Figure 7 and Figure 8 As shown, Figure 7 The figure shows the anode electrode interface of battery 1. Figure 8 The figure shows the anode electrode interface of battery 2. It can be seen that there are obvious black spots on the anode electrode interface of battery 2, while there are no black spots on the anode electrode interface of battery 1.

[0159] The formed batteries 1 and 2 were further subjected to cycle experiments. The cycle experiment temperature was set at 45°C. The specific cycle experiment process was as follows: charging at a constant current charge rate of 1C to the upper limit of the charge voltage, then charging at a constant voltage until the current dropped to 0.05C, standing for 10 minutes, then discharging the battery at a constant current discharge rate of 1C to the lower limit of the discharge voltage and then standing for another 10 minutes, and then cycling the aforementioned charge and discharge process.

[0160] Fig. 9 The curves of the cycle times and the battery health status (SOH) of battery 1 and battery 2 are shown. Fig. 9 As shown, when the SOH is 85%, the number of cycles of battery 2 is 1396, and the number of cycles of battery 1 after the initial formation stage, which successively passes through the discharge stage and the secondary formation stage, is 1500. It can be seen that the battery passes through the discharge stage and the secondary formation stage during the formation process, which effectively increases the service life by ≥100 cycles. It can be seen from the above that 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.

[0161] 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 initial formation stage includes: performing initial formation charging on the battery to be formed until an initial formation battery with a first state of charge is obtained; The discharge stage includes: discharging the primary formation battery at a first discharge rate at a constant current until the voltage of the primary formation battery reaches a lower discharge limit voltage, thereby obtaining a discharge battery; the first discharge rate is greater than the maximum charge rate of the primary formation stage; The secondary formation stage includes: charging the discharged battery through secondary formation until a secondary formation battery with a second state of charge is obtained; The exhaust port of the secondary formation battery is sealed; The inside of the battery can be exhausted through the exhaust port during the primary formation stage, the discharge stage and the secondary formation stage.

2. The battery formation method according to claim 1, characterized in that: The first discharge rate is greater than or equal to 1C and less than or equal to 3C.

3. The battery formation method according to claim 2, characterized in that: The discharge stage also includes: After the discharge is completed, the discharged battery is left to stand for exhaust.

4. The battery formation method according to claim 3, characterized in that: The discharge battery is allowed to stand for venting for a period of time greater than or equal to 30 minutes and less than or equal to 4 hours.

5. The battery formation method according to claim 1, characterized in that: The initial formation stage includes: The first charging stage includes: constant current charging of the battery to be formed until the charge state of the battery to be formed reaches the formation cut-off charge state; The second charging stage includes: constant current charging the battery to be formed that has reached the formation cut-off state of charge, until the state of charge of the battery to be formed reaches the first state of charge, thereby obtaining the initial formation battery; The charging rate in the first charging stage is smaller than the charging rate in the second charging stage.

6. The battery formation method according to claim 5, characterized in that: The first charging stage includes: constant current charging the battery to be formed at a first charging rate until the state of charge of the battery to be formed reaches a third 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: The battery to be formed is charged at a second charging rate for a first preset time period at a constant current, 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.

7. The battery formation method according to claim 1, characterized in that: The secondary formation stage includes: The third charging stage: charging the discharge battery with a constant current until the charge state of the discharge battery reaches a formation cut-off charge state; The fourth charging stage: constant current charging the discharge battery that has reached the formation cut-off state of charge, until the state of charge of the discharge battery reaches the second state of charge, thereby obtaining the secondary formation battery; Wherein, the charging rate of the third charging stage is smaller than the charging rate of the fourth charging stage.

8. The battery formation method according to any one of claims 5 to 7, characterized in that: The formation cut-off state of charge is determined according to the following stages: 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; The formation cut-off state of charge is determined according to the correlation between the gas production flow rate and the charging capacity of the experimental battery during the charging process.

9. The battery formation method according to claim 8, characterized in that: The charging rate of the experimental battery constant current charging is greater than 0 and less than or equal to 0.05C.

10. The battery formation method according to claim 8, characterized in that: Determining the formation cut-off state of charge according to the correlation between the gas production flow rate and the 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 or equal to the gas production cut-off state of charge.

11. The battery formation method according to any one of claims 5 to 7, characterized in that: The formation cut-off state of charge is greater than or equal to the state of charge corresponding to the maximum film-forming potential of the SEI film of the battery.

12. The battery formation method according to any one of claims 5 to 7, characterized in that: The formation cut-off state of charge is greater than or equal to 15%.

13. The battery formation method according to any one of claims 5 to 7, characterized in that: The first state of charge is equal to the second state of charge, and a difference between the first state of charge and the formation-cutoff state of charge is greater than or equal to 2% and less than or equal to 10%.

14. The battery formation method according to any one of claims 1 to 7, characterized in that: The primary formation cell has formed a SEI film in the first state of charge, and the secondary formation cell has formed a SEI film in the second state of charge.

15. The battery formation method according to any one of claims 1 to 7, characterized in that: The value range of the first state of charge is greater than or equal to 15% and less than or equal to 30%; and / or The value range of the second state of charge is greater than or equal to 15% and less than or equal to 30%.

16. The battery formation method according to any one of claims 1 to 7, characterized in that: The internal pressure of the battery in the primary formation stage, the discharge stage and the secondary formation stage is less than the standard atmospheric pressure.

17. 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 16.

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