Battery formation method and device thereof, battery and production method, system and device thereof

Abstract

The application provides a battery formation method and device thereof, a battery and a production method, system and device thereof, and belongs to the technical field of batteries. A differential voltage-voltage change curve of an organic phase film forming reaction of a solid electrolyte interface film is characterized to determine a first target film forming voltage. In the battery formation method, constant voltage charging is performed by using the first target film forming voltage determined by the differential voltage-voltage change curve, so that the film forming quality of the solid electrolyte interface film can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery formation method and apparatus, a battery and its manufacturing method, system and apparatus. Background Technology

[0002] Energy conservation and emission reduction are crucial for sustainable social development. Batteries, with their ability to store and release energy as needed, are widely used in various electrical devices and energy storage systems, becoming an important component in promoting energy transition and sustainable development. For the new energy industry, battery technology is a critical factor in its development.

[0003] If the solid electrolyte interface film formed inside the battery is of poor quality during the first charge, it will cause oxidation and decomposition and repair process during the battery's cycle use, resulting in irreversible consumption of active lithium ions and affecting the battery's performance and lifespan. Summary of the Invention

[0004] This application aims to at least address one of the technical problems existing in the background art. Therefore, one object of this application is to provide a battery formation method and apparatus, a battery and its manufacturing method, system, and apparatus to improve the film formation quality of the solid electrolyte interface film within the battery.

[0005] An embodiment of the first aspect of this application provides a battery formation method, the battery formation method comprising: charging a battery until the voltage of the battery reaches a first target film formation voltage; and performing constant voltage charging on the battery at the first target film formation voltage. Wherein, the first target film formation voltage is the voltage corresponding to the organic phase film formation reaction of the solid electrolyte interface film within the battery, and the first target film formation voltage is determined according to the battery voltage corresponding to the organic phase film formation reaction of the solid electrolyte interface film in the differential voltage-voltage change curve representing the change of the battery's differential voltage value with the battery's voltage.

[0006] In the technical solution of this application embodiment, the first target film formation voltage is determined by using the differential voltage-voltage change curve, which characterizes the organic phase film formation reaction of the solid electrolyte interface film. By charging the battery during formation to bring its voltage to the first target film formation voltage, and then performing constant voltage charging on the battery at the first target film formation voltage, the quality of the organic phase film formation of the solid electrolyte interface film is improved using the first target film formation voltage determined by the differential voltage-voltage change curve reflecting the organic phase film formation reaction of the solid electrolyte interface film, thereby improving the overall film formation quality of the solid electrolyte interface film.

[0007] In some embodiments, charging the battery until the battery voltage reaches a first target film-forming voltage includes: charging the battery at a first charging rate with a constant current until the battery voltage reaches the first target film-forming voltage; wherein the first charging rate is less than 0.1C. This is beneficial for extending the time of the organic film-forming reaction to form a solid electrolyte interface film and for reducing battery polarization.

[0008] In some embodiments, charging the battery until the battery voltage reaches a first target film-forming voltage includes: charging the battery until the battery voltage reaches a second target film-forming voltage; and performing constant-voltage charging on the battery at the second target film-forming voltage. This improves both the inorganic phase film-forming quality and the organic phase film-forming quality of the solid electrolyte interface film, thereby contributing to a more uniform and stable solid electrolyte interface film and further enhancing the film-forming quality of the solid electrolyte interface film within the battery.

[0009] In some embodiments, charging the battery until its voltage reaches a first target film-forming voltage includes: charging the battery at a first sub-charge rate using a constant current until the battery voltage reaches the first target film-forming voltage. Charging the battery until its voltage reaches a second target film-forming voltage includes: charging the battery at a second sub-charge rate using a constant current until the battery voltage reaches the second target film-forming voltage. Wherein, both the first and second sub-charge rates are less than 0.1C. This is beneficial for further extending the film-forming time of the solid electrolyte interface film and further reducing battery polarization.

[0010] In some embodiments, the first sub-charge rate and the second sub-charge rate are equal, which is beneficial to improve the film formation quality of the solid electrolyte interface film while reducing the complexity of the battery formation method.

[0011] In some embodiments, the second target film-forming voltage is determined by: obtaining a differential capacitance-voltage curve characterizing the change in differential capacitance of the battery as a function of the battery voltage during the first charge of the battery; and determining the battery voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interfacial film in the differential capacitance-voltage curve as the second target film-forming voltage. Thus, the second target film-forming voltage is determined using the differential capacitance-voltage curve characterizing the inorganic phase film-forming reaction of the solid electrolyte interfacial film.

[0012] In some embodiments, determining the battery voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface film in the differential capacitance-voltage change curve as the second target film-forming voltage includes: determining the first voltage corresponding to the peak value of the first peak in the differential capacitance-voltage change curve; and determining the first voltage as the second target film-forming voltage. By determining the first voltage in the differential capacitance-voltage change curve that can characterize the inorganic phase film-forming reaction of the solid electrolyte interface film as the second target film-forming voltage, the film-forming quality of the solid electrolyte interface film can be improved by extending the inorganic phase film-forming reaction time of the solid electrolyte interface film within the battery.

[0013] In some embodiments, the differential capacitance-voltage variation curve is determined by the following method: charging capacity and battery voltage are collected at multiple sampling time points during the first charging of the sample battery; wherein the sample battery and the battery are the same type of battery; based on the collected charging capacity and battery voltage, a differential capacitance value is calculated, which is determined based on the ratio of the difference between the charging capacity obtained at two adjacent sampling time points to the difference between the battery voltage; based on the differential capacitance value and the battery voltage, the differential capacitance-voltage variation curve is determined. By utilizing the charging capacitance and battery voltage at multiple sampling time points during the first charging of the sample battery, a differential capacitance value is obtained, thereby obtaining the differential capacitance-voltage variation curve used to determine the first voltage, in order to obtain a more accurate second target film formation voltage.

[0014] In some embodiments, the second target film-forming voltage is greater than or equal to 2V and less than or equal to 2.8V. This covers the voltage corresponding to the film-forming reaction of the inorganic phase characterizing the solid electrolyte interface film, thereby facilitating the extension of the film-forming reaction time of the inorganic phase in the solid electrolyte interface film within the battery in subsequent steps, thus improving the quality of the inorganic phase film formation in the solid electrolyte interface film.

[0015] In some embodiments, the battery formation method further includes: acquiring a differential voltage-voltage change curve characterizing the differential voltage value of the battery as a function of the battery voltage during the first charge of the battery; and determining the point in the differential voltage-voltage change curve that corresponds to the negative electrode of the battery entering LiC. 24 The second voltage corresponding to the phase time is determined as the first target film formation voltage. By determining the second voltage, which can characterize the organic phase film formation reaction of the solid electrolyte interface film in the differential voltage-voltage change curve, as the first target film formation voltage, the film quality of the solid electrolyte interface film can be improved by extending the organic phase film formation reaction time of the solid electrolyte interface film in the battery.

[0016] In some embodiments, the battery formation method further includes: acquiring a differential voltage-voltage change curve characterizing the differential voltage value of the battery as a function of the battery voltage during the first charge; determining the voltage corresponding to the first trough in the differential voltage-voltage change curve as a third voltage; and determining the third voltage as a first target film formation voltage. By determining the voltage corresponding to the first trough in the differential voltage-voltage change curve as the first target film formation voltage, the first target film formation voltage can be quickly determined based on the differential voltage-voltage change curve.

[0017] In some embodiments, the differential voltage-voltage variation curve is determined by the following method: collecting charging capacity and battery voltage at multiple sampling time points during the first charging of the sample battery; wherein the sample battery and the battery are the same type of battery; calculating the differential voltage value based on the collected charging capacity and battery voltage; the differential voltage value is determined based on the ratio of the difference between the battery voltages obtained at two adjacent sampling time points to the difference between the charging capacities; and determining the differential voltage-voltage variation curve based on the differential voltage value and the battery voltage. By utilizing the charging capacitance and battery voltage at multiple sampling time points during the first charging of the sample battery to obtain the differential voltage value, a differential voltage-voltage variation curve for determining the second voltage is obtained, thereby obtaining a more accurate first target film formation voltage.

[0018] In some embodiments, the first target film-forming voltage is greater than or equal to 3V and less than or equal to 3.3V. This covers the voltage corresponding to the film-forming reaction of the organic phase characterizing the solid electrolyte interface film, thereby facilitating the extension of the film-forming reaction time of the organic phase in the solid electrolyte interface film within the battery in subsequent steps, thereby improving the quality of the organic phase film formation in the solid electrolyte interface film.

[0019] In some embodiments, after constant-voltage charging of the battery at the target film-forming voltage, the method further includes: continuing constant-current charging of the battery at a second charging rate until the battery's state of charge reaches the film-forming reaction cutoff state of charge. In this state of charge, the film-forming reaction of the solid electrolyte interface film inside the battery is complete, and the second charging rate is greater than or equal to the first charging rate. This allows for further growth of the organic phase of the solid electrolyte interface film and assists in further growth of the solid electrolyte interface film, while also shortening the formation time.

[0020] In some embodiments, after constant-voltage charging of the battery at a first target film-forming voltage, the method further includes: continuing constant-current charging of the battery at a second charging rate until the battery's state of charge reaches the film-forming reaction cutoff state of charge. In this state of charge, the film-forming reaction of the solid electrolyte interface film inside the battery is complete, the second charging rate is greater than the first sub-charging rate, and the second charging rate is greater than the second sub-charging rate. This allows for further growth of the organic phase of the solid electrolyte interface film and assists in further growth of the solid electrolyte interface film, while also shortening the formation time.

[0021] In some embodiments, the second charging rate is greater than or equal to 0.1C and less than or equal to 0.3C. This can assist in the further growth of the solid electrolyte interface film and improve the film formation quality.

[0022] In some embodiments, the cutoff state of charge for the film formation reaction is greater than or equal to 15% and less than or equal to 35%. This allows the battery formation method to better suit practical applications and increases its applicability.

[0023] In some embodiments, the battery is further charged at a constant current rate at a second charging rate until the battery's state of charge reaches the cutoff state of charge for the film formation reaction. Then, the battery is charged at a constant current rate at a third charging rate until the battery's state of charge reaches a preset state of charge for aging. The third charging rate is greater than the second charging rate. This saves formation time while preparing for the subsequent aging process.

[0024] In some embodiments, a preset state of charge is greater than or equal to 40% and less than or equal to 90% in order to prepare for the aging process.

[0025] An embodiment of the second aspect of this application provides a battery formation apparatus configured to perform any of the above-described battery formation methods.

[0026] An embodiment of the third aspect of this application provides a battery manufacturing method, which includes any of the above-described battery formation methods.

[0027] An embodiment of the fourth aspect of this application provides a battery production system that includes any of the above-described battery formation apparatuses.

[0028] An embodiment of the fifth aspect of this application provides a battery, which is manufactured using any of the battery manufacturing methods described above.

[0029] An embodiment of the sixth aspect of this application provides an electrical device comprising any of the aforementioned batteries, the batteries being used to provide electrical energy.

[0030] An embodiment of the seventh aspect of this application provides an energy storage device comprising any of the aforementioned batteries, the batteries being used to store electrical energy.

[0031] It should be noted that the above description is merely an overview of the technical solution of this application. Terms such as "first aspect," "second aspect," etc., in the above description should be understood as explanations for ease of description and not as a division of technology. To better understand the technical means of this application, it can be implemented according to the contents of the specification. Furthermore, to make the above and other objects, features, and advantages of this application more apparent and understandable, specific embodiments of this application are described below. Attached Figure Description

[0032] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0033] Figure 1 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0034] Figure 2 This is a schematic diagram of the structure of the housing and battery cell in some embodiments of this application;

[0035] Figure 3 This is an exploded structural diagram of a battery cell according to some embodiments of this application;

[0036] Figure 4 This is a flowchart of a battery formation method according to some embodiments of this application;

[0037] Figure 5 This is a flowchart of another battery formation method according to some embodiments of this application;

[0038] Figure 6 This is a flowchart of yet another battery formation method according to some embodiments of this application;

[0039] Figure 7 This is a schematic diagram of the differential voltage-voltage change curves of some embodiments of this application;

[0040] Figure 8 This is a flowchart of yet another battery formation method according to some embodiments of this application;

[0041] Figure 9 The following are current variation curves during the constant voltage charging process in some embodiments of this application;

[0042] Figure 10 This is a schematic diagram of the differential capacitance-voltage variation curves of some embodiments of this application;

[0043] Figure 11 This is a flowchart of yet another battery formation method according to some embodiments of this application;

[0044] Figure 12 The figures show comparative test results for some embodiments of this application.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1000 vehicles;

[0047] Battery 100, controller 200, motor 300;

[0048] Box 10, Part 11, Part 2 12;

[0049] Battery cell 20, end cap 21, electrode terminal 21a, housing 22, electrode assembly 23, tab 23a. Detailed Implementation

[0050] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0052] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0053] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0055] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0056] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0057] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0058] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in various electronic devices, such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing. Battery quality is a key factor influencing the market share of battery manufacturers.

[0059] In battery manufacturing, assembled batteries undergo three processes: electrolyte injection, formation, and aging, to produce a finished battery. The solid electrolyte interphase (SEI) film formed during the formation stage is crucial to the battery's cycle life, safety, and performance. The quality of the SEI film directly affects the battery's quality.

[0060] Let's take a lithium-ion battery as an example. The negative electrode of the battery is made of graphite. However, because the working potential of graphite is incompatible with the electrochemical stability window of the electrolyte, a side reaction occurs between graphite and the electrolyte during the first charge of the lithium-ion battery, generating a solid-liquid interphase (i.e., a solid electrolyte interphase film). The inner layer of the solid electrolyte interphase film is mainly composed of inorganic phases such as LiF, while the outer layer is mainly composed of organic carbonates.

[0061] If the solid electrolyte interface film is of poor quality, during the actual charge-discharge cycles of a lithium-ion battery, the lithium intercalation expansion of graphite and other factors will cause the solid electrolyte interface film to undergo oxidative decomposition and a subsequent repair process. Furthermore, the quality of the repaired solid electrolyte interface film is low, leading to irreversible consumption of active lithium ions, directly resulting in a rapid decline in the lifespan of the lithium-ion battery.

[0062] Therefore, the film-forming quality of the solid electrolyte interfacial membrane affects battery performance and overall battery quality. This quality is related to the quality of the film-forming reactions between the inorganic and organic phases at the solid electrolyte interface. Thus, controlling the film-forming reaction at the solid electrolyte interfacial membrane is crucial for improving its quality.

[0063] To determine the battery voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interfacial membrane and improve the film-forming quality of the solid electrolyte interfacial membrane, this application provides a battery formation method. The battery formation method includes: charging the battery until the battery voltage reaches a first target film-forming voltage; and performing constant-voltage charging on the battery at the first target film-forming voltage. The first target film-forming voltage is the voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interfacial membrane within the battery. The first target film-forming voltage is determined by using the differential voltage-voltage change curve, which characterizes the battery voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interfacial membrane. By charging the battery during formation to bring its voltage to a first target film-forming voltage, and then charging the battery at a constant voltage using the first target film-forming voltage, the quality of the organic phase film forming of the solid electrolyte interface membrane is improved by utilizing the differential voltage-voltage change curve reflecting the film-forming reaction of the organic phase in the solid electrolyte interface membrane. This improves the overall quality of the solid electrolyte interface membrane and extends the battery's lifespan.

[0064] The battery formation method and apparatus provided in this application can be used, but are not limited to, in battery cells or batteries. The battery production method and battery production system provided in this application can be used, but are not limited to, in the production of battery cells or batteries.

[0065] The battery cells and batteries disclosed in this application can be used, but are not limited to, in electrical devices or energy storage devices such as vehicles, ships, or aircraft. A power system comprising the electrical device or energy storage device can be constructed using the battery cells and batteries disclosed in this application, which helps improve battery quality and enhances the reliability of the power system.

[0066] This application provides an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, devices related to entertainment and communication (such as mobile phones, tablets, laptops, electric toys, etc.), production and after-sales service (such as various power tools), transportation (such as electric vehicles, electric cars, ships, etc.), and scientific research (such as spacecraft). Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0067] This application also provides an energy storage device that uses a battery as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0068] For ease of explanation, the following embodiments use a battery-powered device as an example, specifically a vehicle.

[0069] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0070] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0071] Please refer to Figure 2 , Figure 2 The diagram below illustrates the structure of the housing and battery cell according to some embodiments of this application. The battery 100 may include at least one battery cell 20, and the housing 10 provides a space for housing the battery cell 20.

[0072] The housing 10 can adopt various structures. In some embodiments, the housing 10 may include a first part 11 and a second part 12, which overlap each other, together defining a receiving space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one open end, and the first part 11 can be a plate-like structure, covering the open side of the second part 12 so that the first part 11 and the second part 12 together define the receiving space; alternatively, the first part 11 and the second part 12 can both be hollow structures with one open side, with the open side of the first part 11 covering the open side of the second part 12. Of course, the housing 10 formed by the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0073] Multiple battery cells 20 housed within the housing 10 can be connected in series, parallel, or a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections among the multiple battery cells 20. These multiple battery cells 20 can be directly connected in series, parallel, or a hybrid configuration, and then the entire assembly of these battery cells 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can first be connected in series, parallel, or a hybrid configuration to form battery modules, and then these battery modules can be connected in series, parallel, or a hybrid configuration to form a single unit, which is then housed within the housing 10.

[0074] It should be noted that the battery cell 20 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0075] Please refer to Figure 3 , Figure 3 This is an exploded structural diagram of a battery cell provided in some embodiments of this application. The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0076] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy into battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0077] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The housing 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0078] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the electrode assembly 23, while the portions of the positive and negative electrode sheets without active material each constitute a tab 23a. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals to form a current loop.

[0079] Please continue reading. Figures 4-6 , Figure 4 This is a flowchart of a battery formation method according to some embodiments of this application. Figure 5 This is a flowchart of another battery formation method according to some embodiments of this application. Figure 6 This is a flowchart of another battery formation method according to some embodiments of this application.

[0080] This application provides a battery formation method, which includes:

[0081] Step S1: Charge the battery until the battery voltage reaches the target film formation voltage;

[0082] Step S2: Charge the battery at a constant voltage using the target film formation voltage.

[0083] The target film-forming voltage is either the first target film-forming voltage or the first target film-forming voltage. The first target film-forming voltage is the voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interface film in the battery, and the second target film-forming voltage is the voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface film in the battery.

[0084] The battery formation method provided in this application is used in a battery to be formed. The battery to be formed is a battery that has already been assembled into a casing and filled with electrolyte; the battery can be any type or specification of battery cell. It is understood that, unless otherwise specified, the embodiments in this application are all illustrated using a lithium-ion battery as an example. A lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte. The electrolyte facilitates the transport of ions and ionic compounds between the positive and negative electrodes of the battery; the main component of the electrolyte is the electrolyte solution. The electrolyte can be a liquid electrolyte, a solid electrolyte, or a solid-liquid composite electrolyte, etc.

[0085] Formation is a manufacturing process within battery manufacturing. Before formation, battery manufacturing includes electrolyte injection. After formation, battery manufacturing includes aging. Electrolyte injection involves injecting electrolyte into the vacuum-dried, deeply dehydrated battery casing. Formation involves charging the battery after electrolyte injection, while aging involves placing the formed battery at a specific temperature for a period of time.

[0086] The electrolyte injection process can involve sequentially performing vacuum baking, negative pressure electrolyte injection, and high-temperature immersion on the battery cell after it has been encased. Vacuum baking can be performed at a temperature of 110 degrees Celsius for 12 hours. Negative pressure electrolyte injection can be performed at a pressure of -80 kPa. High-temperature immersion can be performed at a temperature of 45 degrees Celsius for 20 hours.

[0087] During the formation process, the battery undergoes its first charge. During charging, the negative electrode potential gradually decreases, while the battery voltage gradually increases. As the negative electrode potential gradually decreases, a competitive and synergistic reaction between the organic and inorganic phases occurs at the solid-liquid interface between the negative electrode and the electrolyte. This generates organic phase products (such as alkyl lithium carbonate (ROCO2Li), polycarbonate, etc.) and inorganic phase products (such as LiF, Li2CO3, Li2O), forming a solid electrolyte interface film covering the electrode material surface. This solid electrolyte interface film allows ions to pass through while blocking electrons, thus isolating the electrolyte from direct contact with the electrode. This prevents excessive internal chemical reactions while also preventing the dissolution of the electrode material and the decomposition of the electrolyte, thereby maintaining the battery's stability.

[0088] The solid electrolyte interfacial membrane (SEI) consists of inorganic and organic phase products, exhibiting a multi-layered composite structure including an inorganic inner layer and an organic outer layer. The inorganic inner layer contacts the electrolyte-facing surface of the electrode and is located between the organic inner layer and the electrode. The inorganic inner layer provides a rapid ion transport channel and blocks electron leakage. The organic outer layer reduces the rate of electrolyte diffusion to the electrode surface. During formation, the inorganic phase film-forming reaction of the SII within the battery is used to form the inorganic inner layer, while the organic phase film-forming reaction is used to form the organic outer layer.

[0089] Solid electrolyte interfacial membranes can achieve the combined effect of an inorganic inner layer and an organic outer layer, allowing ions to pass through while blocking electrons, and isolating the electrolyte from direct contact with the electrodes. This prevents excessive chemical reactions inside the battery, as well as the dissolution of electrode materials and the decomposition of the electrolyte. Therefore, the film quality of solid electrolyte interfacial membranes can be improved by enhancing the film quality of at least one of the inorganic and organic phases involved in their formation.

[0090] Therefore, the target film-forming voltage can include either a second target film-forming voltage or a first target film-forming voltage. That is, the target film-forming voltage can be the voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface film within the battery (i.e., the second target film-forming voltage), or it can be the voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interface film within the battery (i.e., the first target film-forming voltage).

[0091] Constant voltage charging refers to charging a battery using a constant charging voltage. During constant voltage charging, the battery voltage gradually increases until it equals or approximately equals the charging voltage; while the charging current gradually decreases until it equals or approximately equals zero. Here, battery voltage can refer to the battery's terminal voltage.

[0092] In some embodiments, step S2 involves constant-voltage charging of the battery at the target film-forming voltage for a preset duration. The preset duration is a pre-defined time period. By charging the battery during formation to bring its voltage to the target film-forming voltage, and then performing constant-voltage charging at the target film-forming voltage for the preset duration, the time for the inorganic or organic phase film-forming reaction of the solid electrolyte interface film within the battery is extended. This helps to form a more uniform and stable solid electrolyte interface film, improves the film-forming quality of the solid electrolyte interface film within the battery, and increases the battery's lifespan.

[0093] The preset duration can be set differently depending on the actual behavior of the inorganic or organic phase film formation reaction in the battery. Therefore, the preset duration can be determined based on the battery's material system.

[0094] In some embodiments, the preset duration can be greater than or equal to 10 minutes. For example, the preset duration can be equal to 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, or 80 minutes.

[0095] If the preset duration is set too short (e.g., less than 300 seconds), the improvement effect on the film formation quality of the solid electrolyte interface membrane will be insignificant. Therefore, in some embodiments, the preset duration can be greater than or equal to 10 minutes. For example, the preset duration can be equal to 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, or 80 minutes.

[0096] A shorter preset time allows less time for either the inorganic or organic phases to form the solid electrolyte interfacial film, which is detrimental to improving the film quality. However, a longer preset time increases the time cost required for formation. Therefore, to improve the film quality of the solid electrolyte interfacial film while reducing formation time costs, a preset time of 30 minutes is chosen.

[0097] Please continue reading. Figure 5 and Figure 7 , Figure 7 This is a schematic diagram of the differential voltage-voltage change curves of some embodiments of this application.

[0098] When the target film formation voltage is the first target film formation voltage, the battery formation method may include:

[0099] Step S111: Charge the battery until the battery voltage reaches the first target film formation voltage.

[0100] Step S222: Charge the battery at a constant voltage using the first target film formation voltage.

[0101] The first target film-forming voltage is determined according to the battery voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interface film in the differential voltage-voltage change curve, which characterizes the differential voltage value of the battery as a function of the battery voltage.

[0102] The differential voltage value characterizes the sensitivity of a battery's voltage to capacity changes during charging and discharging. The differential voltage-voltage change curve can reflect the chemical reactions and phase transition processes in the electrode materials. Taking a lithium-ion battery as an example, the negative electrode is a graphite electrode. During charging, lithium ions are embedded in the graphite. As lithium ions continuously embed into the graphite, the electrode material undergoes a phase transition, affecting the composition of the organic phase in the solid electrolyte interfacial film. The differential voltage-voltage change curve reflects this phase transition process, thus characterizing the organic phase film-forming reaction in the solid electrolyte interfacial film. Therefore, the first target film-forming voltage can be determined based on the differential voltage-voltage change curve.

[0103] The first target film formation voltage can be determined by using the differential voltage-voltage change curve, which can characterize the organic phase film formation reaction of the solid electrolyte interface film.

[0104] By charging the battery during formation to bring its voltage to a first target film-forming voltage, and then charging the battery at a constant voltage using the first target film-forming voltage, the quality of the organic phase film forming in the solid electrolyte interface membrane is improved by utilizing the differential voltage-voltage change curve reflecting the film-forming reaction of the organic phase in the solid electrolyte interface membrane. This improves the overall quality of the solid electrolyte interface membrane and helps to extend the battery's lifespan.

[0105] In some embodiments, step S222 involves constant-voltage charging of the battery at the first target film-forming voltage for a preset duration. By charging the battery during formation to bring its voltage to the first target film-forming voltage, and then performing constant-voltage charging at the first target film-forming voltage for a preset duration, the film-forming reaction time of the organic phase of the solid electrolyte interface film within the battery is extended. This helps to form a dense organic outer layer, reducing side reactions between the electrolyte and the electrode, thereby contributing to a more uniform and stable solid electrolyte interface film and improving the film-forming quality of the solid electrolyte interface film within the battery.

[0106] Please continue reading. Figure 6 When the target film formation voltage is the second target film formation voltage, the battery formation method may include:

[0107] Step S11: Charge the battery until the battery voltage reaches the second target film formation voltage.

[0108] Step S22: Charge the battery at a constant voltage using the second target film formation voltage.

[0109] In some embodiments, step S22 involves constant-voltage charging of the battery at the second target film-forming voltage for a preset duration. By charging the battery during formation to bring its voltage to the second target film-forming voltage, and then performing constant-voltage charging at the second target film-forming voltage for a preset duration, the inorganic phase film-forming reaction time of the solid electrolyte interface film within the battery is extended. This helps to achieve a more ordered arrangement of inorganic components, improves the ionic conductivity of the solid electrolyte interface film, and reduces the incidence of film-forming side reactions. Consequently, it helps to make the formed solid electrolyte interface film more uniform and stable, thereby improving the film-forming quality of the solid electrolyte interface film within the battery.

[0110] In some embodiments, before step S1, step S11, or step S111, the battery formation method may further include: allowing the battery to stand for a first duration. The first duration may be 30 seconds, 50 seconds, 60 seconds, 70 seconds, or 80 seconds.

[0111] In some embodiments, after step S2, step S22 or step S222, the battery formation method may further include: allowing the battery to stand for a certain period of time (e.g., 30 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds) to help the chemical reaction inside the battery reach equilibrium and promote the uniform formation of the solid electrolyte interface film.

[0112] According to some embodiments of this application, charging the battery until the battery voltage reaches the target film-forming voltage includes:

[0113] The battery is charged at a constant current rate at the first charging rate until the battery voltage reaches the target film formation voltage.

[0114] The first charging rate is less than 0.1C.

[0115] By using a first charging rate of less than 0.1C to charge the battery at a constant current until the battery voltage reaches the target film formation voltage, it is beneficial to extend the film formation time of the solid electrolyte interface film and reduce battery polarization.

[0116] In other words, when the target film-forming voltage is the first target film-forming voltage, charging the battery until the battery voltage reaches the first target film-forming voltage includes:

[0117] The battery is charged at a constant current rate at the first charging rate until the battery voltage reaches the first target film formation voltage.

[0118] The first charging rate is less than 0.1C.

[0119] By using a first charging rate of less than 0.1C to charge the battery at a constant current until the battery voltage reaches the first target film formation voltage, it is beneficial to extend the film formation time of the organic film forming the solid electrolyte interface film and to reduce battery polarization.

[0120] When the target film-forming voltage is the second target film-forming voltage, charging the battery until the battery voltage reaches the second target film-forming voltage includes:

[0121] The battery is charged at a constant current rate at the first charging rate until the battery voltage reaches the second target film formation voltage.

[0122] The first charging rate is less than 0.1C.

[0123] By using a first charging rate of less than 0.1C to charge the battery at a constant current until the battery voltage reaches the second target film formation voltage, it is beneficial to extend the film formation time of the inorganic film forming the solid electrolyte interface film and to reduce battery polarization.

[0124] The charging rate refers to the charging current required to charge a battery to its rated capacity within a specified time.

[0125] Constant current charging refers to charging a battery using a constant charging current. During constant current charging, both the battery voltage and the charging voltage gradually increase. Constant current charging stops when the battery voltage reaches or is approximately equal to a set upper limit voltage. The battery voltage can be the battery's terminal voltage.

[0126] The first charging rate can be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, or 0.09C.

[0127] A lower initial charge rate allows for more time for the inorganic or organic phases to form a solid electrolyte interphase (SEI) film within the battery, which is more conducive to the formation of a dense and stable SEI film. However, a lower initial charge rate also results in a slower charging speed, increasing the time cost of battery formation. Therefore, to balance time cost and the quality of the formed SEI film, the initial charge rate can be set to 0.05C.

[0128] Please continue reading. Figure 8 , Figure 8 This is a flowchart of another battery formation method according to some embodiments of this application.

[0129] According to some embodiments of this application, the battery formation method includes:

[0130] Step S10: Charge the battery until the battery voltage reaches the second target film formation voltage;

[0131] Step S20: Charge the battery at a constant voltage using the second target film formation voltage for a first preset duration;

[0132] Step S30: Charge the battery until the battery voltage reaches the first target film formation voltage;

[0133] Step S40: Charge the battery at a constant voltage using the first target film formation voltage.

[0134] Here, the first target film formation voltage is the same as the first target film formation voltage mentioned above, and the second target film formation voltage is the same as the second target film formation voltage mentioned above.

[0135] By charging the battery to bring its voltage to the second target film-forming voltage, and then performing a first constant-voltage charge on the battery at the second target film-forming voltage for a first preset time, the inorganic phase film-forming reaction time of the solid electrolyte interface film inside the battery is extended, thereby further improving the film-forming quality of the solid electrolyte interface film.

[0136] Since the second target film-forming voltage is usually different from the first target film-forming voltage, if the goal is to improve the film-forming quality of the solid electrolyte interface film by simultaneously improving the quality of both the inorganic and organic phases, a step-by-step charging method can be used to charge to the corresponding target film-forming voltage and then perform constant-voltage charging at their respective target charging voltages. This approach improves the quality of both the inorganic and organic phases of the solid electrolyte interface film, thereby enhancing the overall film-forming quality.

[0137] In some embodiments, the second target film-forming voltage is lower than the first target film-forming voltage. Because the battery voltage gradually increases during charging, it will first reach the second target film-forming voltage, and then, with continued charging, reach the first target film-forming voltage. Therefore, in the battery formation method, the battery voltage can be first charged to the second target film-forming voltage, and then the battery can be charged at a constant voltage for a preset time using the second target film-forming voltage. Then, the battery voltage can be charged to the first target film-forming voltage, and the battery can be charged at a constant voltage using the first target film-forming voltage.

[0138] In some embodiments, step S30 involves constant-voltage charging of the battery at a first target film-forming voltage for a second preset duration. By charging the battery at the first target film-forming voltage for the second preset duration, the film-forming reaction time of the organic phase in the solid electrolyte interface film within the battery is extended. This improves both the inorganic and organic phase film-forming quality of the solid electrolyte interface film, thereby contributing to a more uniform and stable solid electrolyte interface film and further enhancing the overall film-forming quality of the solid electrolyte interface film within the battery.

[0139] Both the first and second preset durations are pre-set time periods. The first preset duration can be set differently depending on the performance of the inorganic phase film-forming reaction of the solid electrolyte interface film within the battery, and the second preset duration can be set differently depending on the performance of the organic phase film-forming reaction of the solid electrolyte interface film within the battery. Therefore, the first and second preset durations can be set differently according to actual needs or the different batteries used.

[0140] In some embodiments, the first preset duration may be greater than or equal to 10 minutes and less than or equal to 120 minutes. For example, the first preset duration may be set to 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 90 minutes or 120 minutes.

[0141] Setting the first preset time too short (e.g., less than 300 seconds) will not significantly improve the quality of the inorganic phase film formation at the solid electrolyte interface. Therefore, a longer first preset time is more conducive to forming a higher quality solid electrolyte interface film. However, a longer first preset time also increases the time cost of battery formation. Furthermore, please refer to [further details omitted]. Figure 9 , Figure 9 The graphs show the current variation curves during constant-voltage charging in some embodiments of this application. The horizontal axis represents time in seconds (s), and the vertical axis represents the charging current in milliamperes (mA). During the first constant-voltage charging of the battery at the second target film-forming voltage (denoted as X1), the corresponding charging current shows a decreasing trend and gradually stabilizes over time. During the first constant-voltage charging process, the amount of charge added after the corresponding charging current reaches the current inflection point is relatively small. If the cutoff time of the first constant-voltage charging is located at or after the current inflection point of the corresponding current variation curve, the improvement in the inorganic phase film formation quality of the solid electrolyte interface film will no longer be significantly increased. Therefore, to balance the film formation quality and time cost of the solid electrolyte interface film, the first preset time can be set to 30 minutes.

[0142] In some embodiments, the second preset duration can be greater than or equal to 10 minutes and less than or equal to 120 minutes. For example, the second preset duration can be set to 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 90 minutes or 120 minutes.

[0143] If the second preset time is set too short (e.g., less than 300 seconds), the improvement effect on the organic phase film formation quality of the solid electrolyte interface membrane will be insignificant. Therefore, a longer second preset time is more conducive to forming a higher quality solid electrolyte interface membrane. However, a longer second preset time also increases the time cost of battery formation. Furthermore, please refer to [further details omitted]. Figure 9 When the battery is charged at the first target film-forming voltage (denoted as X2) for the second time under constant voltage, the corresponding charging current shows a decreasing trend and gradually stabilizes over time. During the second constant voltage charging process, the amount of charge added after the corresponding charging current reaches the current inflection point is relatively small. If the cutoff time of the second constant voltage charging falls at or after the current inflection point of the corresponding current change curve, the improvement in the quality of the organic phase film formation at the solid electrolyte interface membrane will no longer be significant. Therefore, to balance the film formation quality and time cost of the solid electrolyte interface membrane, the second preset duration can be set to 30 minutes.

[0144] The first preset duration and the second preset duration can be set to be the same or different. In some embodiments, the first preset duration and the second preset duration are set to be the same to reduce the complexity of the battery formation method. In some embodiments, the first preset duration and the second preset duration are set to be different so that the battery can more precisely control the film formation quality of the solid electrolyte interface film based on the actual time required for the inorganic phase film formation reaction and the organic phase film formation reaction.

[0145] In some embodiments, after step S20, the battery may be left to stand for a second period of time to help the chemical reactions inside the battery reach equilibrium and promote the uniform formation of the solid electrolyte interface film. The second period of time may be 30 seconds, 50 seconds, 60 seconds, 70 seconds, or 80 seconds.

[0146] In some embodiments, after step S40, the battery may be left to stand for a third period of time to help the chemical reactions inside the battery reach equilibrium and promote the uniform formation of the solid electrolyte interface film. The third period of time may be greater than or equal to 10 seconds and less than or equal to 80 seconds. For example, the third period of time may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, or 80 seconds.

[0147] According to some embodiments of this application, continuing to charge the battery until the battery voltage reaches the first target film formation voltage includes:

[0148] Step S301: Charge the battery at a constant current rate using a first sub-charge rate until the battery voltage reaches the first target film formation voltage. The first sub-charge rate is less than 0.1C.

[0149] According to some embodiments of this application, charging the battery until the battery voltage reaches the second target film formation voltage includes:

[0150] Step S101: Charge the battery at a constant current rate using a second sub-charge rate until the battery voltage reaches the second target film formation voltage. The second sub-charge rate is less than 0.1C.

[0151] In some embodiments, the first sub-charging rate can be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, or 0.09C. The second sub-charging rate can be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, or 0.09C.

[0152] A lower first-charge rate allows for a longer time for the organic phase to form a solid electrolyte interphase (SEI) film within the battery, which is more conducive to producing a higher-quality SEI film. However, a lower first-charge rate also results in a slower charging speed, increasing the time cost of battery formation. Therefore, to balance time cost and the quality of the resulting SEI film, the first-charge rate can be set to 0.05C.

[0153] A lower second charge rate allows for a longer time for the inorganic phase film formation reaction of the solid electrolyte interface film within the battery, which is more conducive to generating a higher quality solid electrolyte interface film. However, a lower second charge rate also results in a slower charging speed, increasing the time cost of battery formation. Therefore, to balance time cost and the quality of the formed solid electrolyte interface film, the second charge rate can be set to 0.05C.

[0154] It should be noted that the battery formation method may simultaneously include the steps of constant current charging of the battery at a second sub-charge rate of less than 0.1C until the battery voltage reaches the second target film formation voltage, and constant current charging of the battery at a first sub-charge rate of less than 0.1C until the battery voltage reaches the first target film formation voltage.

[0155] By using a second sub-charge rate less than 0.1C to perform constant current charging on the battery until the battery voltage reaches the second target film-forming voltage, it is beneficial to extend the inorganic phase film-forming reaction time of the solid electrolyte interface film and reduce battery polarization. Similarly, by using a first sub-charge rate less than 0.1C to perform constant current charging on the battery until the battery voltage reaches the first target film-forming voltage, it is beneficial to extend the organic phase film-forming reaction time of the solid electrolyte interface film and reduce battery polarization. Furthermore, by ensuring that both the first and second sub-charge rates are less than 0.1C, it is beneficial to further extend the film-forming time of the solid electrolyte interface film and further reduce battery polarization.

[0156] According to some embodiments of this application, the first sub-charge rate and the second sub-charge rate are equal.

[0157] In some embodiments, the first sub-charge rate and the second sub-charge rate are both equal to 0.03C, 0.05C, or 0.07C.

[0158] It should be noted that the first and second sub-charging rates can be set differently depending on the actual needs. For example, the first sub-charging rate can be set to one of 0.03C and 0.05C, and the second sub-charging rate can be set to the other of 0.03C and 0.05C.

[0159] By making the first sub-charge rate and the second sub-charge rate equal, it is beneficial to improve the film formation quality of the solid electrolyte interface film while reducing the complexity of the battery formation method.

[0160] Please continue reading. Figure 10 , Figure 10 This is a schematic diagram of the differential capacitance-voltage change curves of some embodiments of this application.

[0161] According to some embodiments of this application, the second target film-forming voltage is determined according to the following method:

[0162] Obtain the differential capacitance-voltage curve, which characterizes the differential capacitance value of the battery as a function of the battery voltage, during the first charge of the battery.

[0163] The battery voltage corresponding to the inorganic phase film-forming reaction that characterizes the solid electrolyte interface film in the differential capacitance-voltage change curve is determined as the second target film-forming voltage.

[0164] Differential capacitance characterizes the change in charge caused by a small change in voltage. It can be used to describe the nonlinear relationship between charge storage behavior at the electrode-electrolyte interface. The differential capacitance value can also reflect the kinetics of ion intercalation reactions in the electrode material.

[0165] The differential capacitance-voltage curve reflects the electrochemical reactions and phase transitions occurring in the electrode material and can characterize the properties of the solid electrolyte interfacial film. During battery charging, a redox reaction occurs at the interface between the electrolyte and the electrode, generating the inorganic phase products of the solid electrolyte interfacial film. The portion of the differential capacitance-voltage curve that corresponds to the redox reaction can characterize the inorganic phase film-forming reaction of the solid electrolyte interfacial film. Therefore, the second target film-forming voltage can be determined based on the differential capacitance-voltage curve.

[0166] The second target film formation voltage can be determined by using the differential capacitance-voltage change curve, which can characterize the inorganic phase film formation reaction of the solid electrolyte interface film.

[0167] According to some embodiments of this application, determining the battery voltage corresponding to the inorganic phase film-forming reaction characterizing the solid electrolyte interface film in the differential capacitance-voltage change curve as the second target film-forming voltage includes:

[0168] Determine the first voltage corresponding to the peak value of the first peak in the differential capacitance-voltage change curve;

[0169] The first voltage is determined as the second target film formation voltage.

[0170] Peak value refers to the maximum value of a wave peak, and the first voltage corresponding to the peak value is as follows: Figure 10 As shown in X1, changes in the interface structure (such as ion transport paths and surface roughness) during the formation of a solid electrolyte interfacial film significantly affect capacitance characteristics. For example, side reactions during film formation (such as solvent decomposition) may trigger transient capacitance peaks. The reduction peaks exhibited in the differential capacitance-voltage curves correspond to the inorganic phase film formation reactions of the solid electrolyte interfacial film.

[0171] During battery charging, the solvent or additives of the electrolyte may undergo a redox reaction on the electrode surface. The solvent or additives are reduced to generate inorganic components of the solid electrolyte interface film. When the solvent or additives are reduced, a reduction peak will be shown in the differential capacitance-voltage curve.

[0172] Electrolytes may include solvents and additives. When additives are included in the electrolyte, the additives undergo a redox reaction before the solvent during battery charging, generating inorganic components of the solid electrolyte interface film to regulate the film-forming composition of the solid electrolyte interface film. Additives may be at least one of the following: vinylene carbonate, propane sulfonate lactone, fluoroethylene carbonate, vinyl sulfate, lithium difluorosulfonylimide, lithium difluorophosphate, triethyl phosphate, and tri(2,2,2-trifluoroethyl) phosphate.

[0173] Although the formation of the solid electrolyte interfacial film is affected by the electrolyte, it is understandable that for a specific electrolyte formulation and design, the second target film formation voltage corresponding to the charging stage is a stable value. Therefore, the second target film formation voltage can be obtained by statistically analyzing the first voltage in historical data.

[0174] In some embodiments, a first voltage can be extracted from the differential capacitance-voltage change curve using a computer or other device, and the first voltage can be determined as the second target film formation voltage.

[0175] Considering the influence of actual testing methods and testing environment, the first voltage measured multiple times may not be exactly the same. Therefore, to unify the first voltage measured multiple times, a target range can be determined, and the second target film formation voltage can be equal to a value within the target range. For example, the target range could correspond to [Vs-V1, Vs+V2]; where Vs represents the first voltage, and V1 and V2 represent voltage margins that can vary relative to the first voltage.

[0176] In some embodiments, the first voltage Vs included in the target range can be one of multiple measured first voltages, where V1 can be 0.5, 1, 1.5, or 2. V2 can be 0.5, 1, 1.5, or 2.

[0177] In some embodiments, the target interval can be a set of first voltages measured multiple times, such as the target interval being [VA, VB], and the smallest first voltage measured multiple times can be selected as VA, and the largest first voltage measured multiple times can be selected as VB.

[0178] By determining the first voltage in the differential capacitance-voltage change curve, which can characterize the inorganic phase film formation reaction of the solid electrolyte interface film, as the second target film formation voltage, the film quality of the solid electrolyte interface film can be improved by extending the inorganic phase film formation reaction time of the solid electrolyte interface film in the battery.

[0179] According to some embodiments of this application, the differential capacitance-voltage change curve is determined by the following method:

[0180] The charging capacity and battery voltage of the sample battery were collected at multiple sampling time points during the first charging of the sample battery; the sample battery and the battery were the same type of battery.

[0181] Based on the collected charging capacity and battery voltage, the differential capacitance value is calculated. The differential capacitance value is determined by the ratio of the difference between the charging capacity obtained at two adjacent sampling time points to the difference between the battery voltage.

[0182] Based on the differential capacitance value and the battery voltage, determine the differential capacitance-voltage change curve.

[0183] The sample battery being the same as the battery to be formed means that the sample battery is the same battery that needs to be formed. The materials, specifications, manufacturing processes and conditions of each component in the sample battery can be the same as those of the battery to be formed. For example, they can be products from the same batch produced on the same production line.

[0184] During the initial charge of the sample battery, it can be charged at a constant current rate using the test charging rate until the battery voltage reaches the upper charging limit voltage. The upper charging limit voltage refers to the highest voltage the battery can reach during charging; exceeding this value may lead to overcharging, thereby damaging the battery's performance and lifespan. For lithium-ion batteries, this upper charging limit voltage is typically around 4.2 volts, but may vary depending on the battery type and design. During charging, the battery voltage gradually increases. When the battery voltage reaches the set upper charging limit voltage, the charger switches from constant current charging mode to constant voltage charging mode, meaning the voltage remains constant while the current decreases as the battery gradually fills until charging is complete. The test charging rate can be less than 0.1C.

[0185] A sampling time point refers to the point in time when the battery is sampled. A first preset time length can be spaced between two adjacent sampling time points. In some embodiments, the first preset time length can be 1 second, 5 seconds, or 10 seconds.

[0186] To make the obtained differential capacitance-voltage change curve more accurately characterize the properties of the solid electrolyte interface film, the first preset time length is set to 1 second.

[0187] The differential capacitance value is determined based on the ratio of the difference between the charging capacity obtained at two adjacent sampling time points to the difference between the battery voltages, which corresponds to dQ / dV=(Q t+1 -Q t ) / (V t+1 -V t Where dQ / dV represents the differential capacitance value, Q t+1 and Q t V represents the charging capacity obtained at two adjacent sampling time points. t+1 and V t This represents the charging voltage obtained between two adjacent sampling time points. The sampling time point can start from 0 seconds.

[0188] After calculating the differential capacitance value, the charging voltage can be used as the horizontal axis, with the unit of the horizontal axis being volts (i.e., ...). Figure 10 The voltage (V) in the figure), the differential capacitance value is the ordinate (i.e., Figure 10 The differential capacitance-voltage change curve is obtained by using the Value in the equation.

[0189] In some embodiments, after obtaining the differential capacitance value based on the ratio of the difference between the charging capacity obtained from two adjacent sampling time points to the difference between the battery voltage, multiple differential capacitance values ​​can be denoised using filtering methods such as Gaussian filtering and Kalman filtering. The denoised differential capacitance values ​​are then used to obtain the differential capacitance-voltage change curve. By denoising the differential capacitance values, the oscillation amplitude at the corresponding restoration peak of the differential capacitance-voltage curve can be reduced, thereby allowing the first voltage to be determined conveniently and quickly.

[0190] Understandably, the differential capacitance value can be calculated using computer equipment and a differential capacitance-voltage change curve can be plotted.

[0191] By utilizing the charging capacitance and battery voltage at multiple sampling time points during the initial charging of the sample battery, the differential capacitance value is obtained, and then the differential capacitance-voltage change curve used to determine the first voltage is obtained, so as to obtain a more accurate second target film formation voltage.

[0192] According to some embodiments of this application, the second target film formation voltage is greater than or equal to 2V and less than or equal to 2.8V.

[0193] In some embodiments, the second target film formation voltage may be equal to 2V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, or 2.8V.

[0194] In some embodiments, the second target film-forming voltage can also be determined based on the battery's state of charge (SOC). The state of charge is the ratio of the battery's remaining capacity to its capacity at the point of full charge. For example, taking a lithium-ion battery with a graphite anode as an example, the state of charge range corresponding to the inorganic phase film-forming reaction at the solid electrolyte interface is mainly concentrated below 1%, at which point the battery voltage is mostly between 2V and 2.8V. Therefore, the battery voltage corresponding to a state of charge below 1% can be selected as the second target film-forming voltage.

[0195] The second target film-forming voltage is directly related to the battery's material system, meaning it can be determined based on the battery's material type. It should be noted that the second target film-forming voltage can vary depending on the additives included in the electrolyte. However, when the electrolyte uses a fixed formulation and design, the second target film-forming voltage is a specific point value.

[0196] By setting the second target film-forming voltage to be greater than or equal to 2V and less than or equal to 2.8V, which covers the voltage corresponding to the film-forming reaction of the inorganic phase of the solid electrolyte interface film, it is possible to extend the film-forming reaction time of the inorganic phase of the solid electrolyte interface film in the battery in subsequent steps, thereby improving the film-forming quality of the inorganic phase of the solid electrolyte interface film.

[0197] Please continue reading. Figure 7 According to some embodiments of this application, the battery formation method further includes:

[0198] Obtain the differential voltage-voltage change curve, which characterizes the differential voltage value of the battery as a function of the battery voltage during the first charge;

[0199] Determine the differential voltage-voltage change curve and the point where the negative electrode of the battery enters LiC. 24 The second voltage corresponding to the phase;

[0200] The second voltage is determined as the first target film formation voltage.

[0201] Taking a lithium-ion battery as an example, with a graphite anode as the electrode, during charging, lithium ions intercalate into the graphite. During this intercalation, a phase transition occurs at the graphite anode. During this phase transition, fourth-order compounds (such as LiC) are present. 36 The process involves the transformation of graphite from pure carbon to LiC, resulting in second-order compounds and ultimately a first-order compound (LiC6). 24 Before the transition to LiC, the organic phase film-forming reaction dominates, while the organic phase film-forming reaction dominates. 24 After this phase transition, lithium ions can no longer be inserted into the graphite electrode, thus weakening their influence on the composition of the organic phase of the solid electrolyte interface film. Therefore, the negative electrode in the differential voltage-voltage change curve can be incorporated into LiC. 24 The voltage corresponding to the phase is determined as the first target film formation voltage.

[0202] The differential voltage-voltage change curve can reflect the beginning and end of a phase transition. For example... Figure 7 The first peak shown from left to right corresponds to LiC where lithium intercalation begins in graphite. 24 Phase transition peak. Figure 7 The trough corresponding to the dashed line in the middle represents the negative electrode of the battery entering the LiC phase. 24 At the beginning of the phase, the second voltage is as follows Figure 7 As shown in X2.

[0203] According to some embodiments of this application, the first trough in the differential voltage-capacitance change curve corresponds to the negative electrode of the battery entering LiC. 24 The start time of the phase. Therefore, to quickly determine the first target film formation voltage, the battery formation method also includes:

[0204] Obtain the differential voltage-voltage change curve, which characterizes the differential voltage value of the battery as a function of the battery voltage during the first charge;

[0205] The voltage corresponding to the first trough in the differential voltage-voltage change curve is determined to be the third voltage;

[0206] The third voltage is determined as the first target film formation voltage.

[0207] By defining the voltage corresponding to the first trough in the differential voltage-voltage change curve as the first target film formation voltage, the first target film formation voltage can be quickly determined based on the differential voltage-voltage change curve.

[0208] In some embodiments, the negative electrode of the battery may also be selected to enter LiC. 24 The voltage before the phase transition is used as the first target film formation voltage. This allows the differential voltage-voltage change curve to be aligned with the negative electrode of the battery before entering the LiC phase. 24 The voltage before and the second voltage are used as a selection range, and the first target film formation voltage can be equal to one of the values ​​in this selection range.

[0209] In some embodiments, the voltage preceding the third voltage corresponding to the first trough in the differential voltage-voltage variation curve can also be used as the first target film formation voltage. That is, the voltage preceding the third voltage corresponding to the first trough in the differential voltage-voltage variation curve and the third voltage can be used as a selection interval, and the first target film formation voltage can be equal to a value within this selection interval.

[0210] In some embodiments, the peak value of the second peak in the differential capacitance-voltage curve and the corresponding voltage thereafter are determined as the first target film formation voltage. However, since the second peak in the differential capacitance-voltage curve corresponds to LiC 12 In this phase, lithium intercalation in graphite forms LiC. 12 Since the organic phase dominates, determining the peak value of the second peak in the differential capacitance-voltage curve and the corresponding voltage thereafter as the first target film formation voltage does not actually improve the film formation effect of the organic phase at the solid electrolyte interface. Furthermore, the differential voltage-voltage curve, which represents the negative electrode of the battery entering LiC, is used instead. 24 Before or entering LiC 24 Using the phase voltage as the first target film-forming voltage can more accurately reflect the time period corresponding to the organic phase film-forming reaction of the solid electrolyte interface film, thereby improving the organic phase film-forming effect of the solid electrolyte interface film.

[0211] By determining the second voltage in the differential voltage-voltage change curve, which can characterize the organic phase film-forming reaction of the solid electrolyte interface membrane, as the first target film-forming voltage, the film-forming quality of the solid electrolyte interface membrane can be improved by extending the organic phase film-forming reaction time of the solid electrolyte interface membrane in the battery.

[0212] According to some embodiments of this application, the differential voltage-voltage change curve is determined by the following method:

[0213] The charging capacity and battery voltage of the sample battery were collected at multiple sampling time points during the first charging of the sample battery; the sample battery and the battery were the same type of battery.

[0214] The differential voltage value is calculated based on the collected charging capacity and battery voltage; the differential voltage value is determined by the ratio of the difference between the battery voltages obtained at two adjacent sampling time points to the difference between the charging capacities.

[0215] Based on the differential voltage value and the battery voltage, determine the differential voltage-voltage change curve.

[0216] As mentioned above, the sample battery being the same as the battery to be formed means that the sample battery is the same battery that needs to be formed. The materials, specifications, manufacturing processes, and conditions of each component in the sample battery can be the same as those of the battery to be formed. For example, they can be products from the same batch produced on the same production line. When the sample battery is first charged, it can be charged at a constant current at the test charging rate until the voltage of the sample battery reaches the upper limit of the charging voltage.

[0217] The aforementioned sampling time point refers to the time point at which the battery is sampled. A second preset time length may be spaced between two adjacent sampling time points. In some embodiments, the second preset time length may be 1 second, 5 seconds, or 10 seconds.

[0218] To make the obtained differential voltage-voltage change curve more accurately characterize the phase transition process of the electrode material, the second preset time length is set to 1 second.

[0219] The differential voltage value is determined based on the ratio of the difference between the battery voltages obtained at two adjacent sampling time points to the difference between the charging capacities, which corresponds to dV / dQ=(V t+1 -V t ) / (Q t+1 -Q t Where dV / dQ represents the differential voltage value, and Q... t+1 and Q t V represents the charging capacity obtained at two adjacent sampling time points. t+1 and V t This represents the charging voltage obtained between two adjacent sampling time points. The sampling time point can start from 0 seconds.

[0220] After calculating the differential voltage value, the charging voltage can be used as the horizontal axis, with the unit of the horizontal axis being volts (i.e., ...). Figure 7 The voltage in (V), the differential voltage value is the ordinate (i.e., Figure 7 The differential voltage-voltage change curve is obtained by using the Value in the equation.

[0221] In some embodiments, after calculating the differential voltage value, Gaussian filtering, Kalman filtering, or other filtering methods can be used to reduce the noise of multiple differential voltage values, and the differential voltage-voltage change curve can be obtained using the denoised multiple differential voltage values. By reducing the noise of the differential voltage value, the second voltage can be determined conveniently and quickly.

[0222] Understandably, the differential voltage value can be calculated using computer equipment and the differential voltage-voltage change curve can be plotted.

[0223] By utilizing the charging capacitance and battery voltage at multiple sampling time points during the initial charging of the sample battery, a differential voltage value is obtained, which in turn yields a differential voltage-voltage change curve for determining the second voltage, thus enabling a more accurate first target film formation voltage.

[0224] According to some embodiments of this application, the first target film formation voltage is greater than or equal to 3V and less than or equal to 3.3V.

[0225] In some embodiments, the first target film formation voltage may be equal to 3V, 3.1V, 3.2V or 3.3V.

[0226] In some embodiments, the first target film-forming voltage can also be determined based on the battery's state of charge (SOC). For example, taking a lithium-ion battery with a graphite anode as an example, the SOC range corresponding to the organic phase film-forming reaction at the solid electrolyte interface is mainly concentrated between 1% and 8%, at which point the battery voltage is mostly between 3V and 3.3V. Therefore, the battery voltage corresponding to an SOC of 1% to 8% can be selected as the first target film-forming voltage.

[0227] The first target film-forming voltage is directly related to the battery's material system, meaning it can be determined based on the battery's material type. It should be noted that when a battery uses a fixed formulation and design, the first target film-forming voltage is a specific point value.

[0228] By setting the first target film-forming voltage to be greater than or equal to 3V and less than or equal to 3.3V, which covers the voltage corresponding to the film-forming reaction of the organic phase in the solid electrolyte interface film, it is possible to extend the film-forming reaction time of the organic phase in the solid electrolyte interface film in the battery in subsequent steps, thereby improving the film-forming quality of the organic phase in the solid electrolyte interface film.

[0229] Please continue reading. Figure 4 According to some embodiments of this application, after the battery is charged at a constant voltage with a target film-forming voltage for a preset duration, the method further includes:

[0230] Step S3: Continue to charge the battery at a constant current rate of the second charging rate until the battery's state of charge reaches the state of charge at which the film formation reaction is cut off.

[0231] In this case, the film-forming reaction of the solid electrolyte interface film inside the battery has been completed under the charged state where the film-forming reaction is cut off, and the second charging rate is greater than or equal to the first charging rate.

[0232] In other words, when the target film formation voltage is the first target film formation voltage, please continue reading. Figure 5 After the battery is charged at a constant voltage using the first target film-forming voltage, the method further includes:

[0233] Step S3: Continue to charge the battery at a constant current rate of the second charging rate until the battery's state of charge reaches the state of charge at which the film formation reaction is cut off.

[0234] When the target film formation voltage is the second target film formation voltage, please continue to refer to [the relevant documentation]. Figure 6 After the battery is charged at a constant voltage using the second target film-forming voltage, the method further includes:

[0235] Step S3: Continue to charge the battery at a constant current rate of the second charging rate until the battery's state of charge reaches the state of charge at which the film formation reaction is cut off.

[0236] The state of charge (SOC) at the cutoff point for film formation refers to the specific state of charge a lithium-ion battery reaches during its formation process, at which point the solid electrolyte interfacial film inside the battery is essentially formed. This SOC is part of the formation process in battery manufacturing. Reaching the SOC at this point means that the battery has essentially formed a solid electrolyte interfacial film, and the amount of gas generated by the film formation side reactions gradually approaches zero. In some examples, the SOC at the cutoff point can be determined by detecting changes in the amount of gas generated during the formation stage. For example, the SOC at which the gas generation rate or flow rate inside the battery during the formation stage is reduced to a preset gas generation threshold can be defined as the aforementioned SOC at the cutoff point for film formation. Alternatively, a SOC margin can be added to the SOC at which the gas generation rate or flow rate is reduced to a preset gas generation threshold to determine the SOC at the cutoff point for film formation. For example, adding 5% SOC can be used.

[0237] Before the battery is charged to the state of charge cutoff for film formation reaction, the battery needs enough time to carry out the film formation reaction. Therefore, a smaller first charging rate is usually selected. After the state of charge cutoff for film formation reaction is reached, since the film formation reaction is basically completed, a larger second charging rate can be used to charge the battery to shorten the time consumed in the formation stage.

[0238] The duration for which the battery continues to be charged at a constant current rate at the second charging rate can be equal to the third preset duration. The third preset duration can be greater than the first or second preset duration. For example, the third preset duration is 40 minutes, 60 minutes, or 80 minutes.

[0239] In step S3, lithium ions begin to be inserted into the graphite anode, accompanied by the further growth of the organic phase of the solid electrolyte interface film.

[0240] In some embodiments, the second charging rate can take different values ​​at different stages to improve the film formation quality of the solid electrolyte interface film while saving formation time. For example... Figure 6 Taking the battery formation method shown as an example, in step S3, when the battery corresponds to a first state of charge (SOC) range, the second charging rate is set to a first value. When the battery corresponds to a second SOC range, the second charging rate is set to a second value. The first SOC range includes a smaller SOC range than the second SOC range, and the first value is less than the second value. For example, the first SOC range may include a SOC of less than 8%, or a SOC range of 8% to the film formation reaction cutoff SOC. The first value can be 0.05C; the second value can be 0.1C.

[0241] In some embodiments, after step S3, the method may further include: allowing the battery to stand for a certain period of time (e.g., 10 to 60 seconds) to help the chemical reaction inside the battery reach equilibrium and promote the uniform formation of the solid electrolyte interface film.

[0242] During the process of continuously charging the battery at a second charging rate until the battery's state of charge reaches the cutoff state of charge for film formation, the organic phase of the solid electrolyte interfacial film further grows. The second charging rate is greater than or equal to the first charging rate to assist in the further growth of the solid electrolyte interfacial film while shortening the formation time.

[0243] Please continue reading. Figure 8 According to some embodiments of this application, after the battery is charged at a constant voltage using a first target film-forming voltage, the method further includes:

[0244] Step S50: Continue to charge the battery at a constant current rate at the second charging rate until the battery reaches the state of charge at which the film formation reaction is cut off.

[0245] In this case, the film-forming reaction of the solid electrolyte interface film inside the battery has been completed under the charged state where the film-forming reaction is cut off, the second charging rate is greater than the first sub-charging rate, and the second charging rate is greater than the second sub-charging rate.

[0246] As mentioned above, the battery is charged to the state of charge where the film-forming reaction is cut off, which means that the battery has basically formed a solid electrolyte interface film during this charging stage.

[0247] In some embodiments, after step S50, the process may further include: allowing the battery to rest for a fourth duration. The fourth duration may be greater than or equal to 10 seconds and less than or equal to 80 seconds. For example, the fourth duration may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, or 80 seconds.

[0248] During the process of continuing to charge the battery at a constant current rate at the second charging rate until the battery's state of charge reaches the cutoff state of charge for film formation, the organic phase of the solid electrolyte interfacial film further grows. The second charging rate is greater than or equal to the first sub-charging rate, and greater than the second sub-charging rate, which can assist the solid electrolyte interfacial film to grow further while shortening the formation time.

[0249] According to some embodiments of this application, the second charging rate is greater than or equal to 0.1C and less than or equal to 0.3C.

[0250] In some embodiments, the second charging rate is equal to 0.1C, 0.2C, or 0.3C. Since a smaller charging rate results in a better quality solid electrolyte interface film, the second charging rate can be further set to 0.1C.

[0251] By setting the second charging rate to be greater than or equal to 0.1C and less than or equal to 0.3C, the solid electrolyte interface film can be further grown, thereby improving the film quality of the solid electrolyte interface film.

[0252] According to some embodiments of this application, the cutoff state of charge of the film-forming reaction is greater than or equal to 15% and less than or equal to 35%.

[0253] Because batteries made of different materials or with different compositions have different cutoff states of charge for the film-forming reaction, the specific cutoff state of charge for the film-forming reaction can be selected based on empirical values ​​for batteries of the same material and specification type, or it can be obtained through detection methods, such as detecting the gas generation rate or gas generation flow rate during the formation stage.

[0254] Taking graphite anode as an example, the state of charge (SOC) range of the battery corresponding to the solid electrolyte membrane formation of graphite is mainly concentrated below 15%. Therefore, in some embodiments, the cutoff SOC of the film formation reaction can be set to be greater than or equal to 15% and less than or equal to 35%.

[0255] In some embodiments, after the battery is charged at a first target film-forming voltage for a preset duration under constant voltage, the battery's state of charge is approximately 10%. The state of charge at the cutoff point of the film-forming reaction can be 15%, 20%, 25%, 30%, or 35%.

[0256] By setting the cutoff state of charge of the film formation reaction to be greater than or equal to 15% and less than or equal to 35%, the battery formation method can be made more suitable for practical applications, thereby increasing the application rate of the battery formation method.

[0257] Please continue reading. Figures 4-6 and Figure 8 According to some embodiments of this application, the battery is further charged at a constant current rate at a second charging rate until the battery reaches the state of charge at which the film formation reaction is cut off, and then the process includes:

[0258] Step S4: Continue charging the battery at a constant current rate of the third charging rate until the battery's state of charge reaches the preset state of charge for aging. The third charging rate is greater than the second charging rate.

[0259] The preset state of charge (SOC) is the initial state of charge a battery possesses during aging. Batteries undergo aging treatment after formation.

[0260] In some embodiments, the third charging rate is greater than 0.3C. For example, the third charging rate is equal to 0.33C or 0.5C.

[0261] In some embodiments, after step S4, the battery may be left to stand for a fifth period of time to help the chemical reactions inside the battery reach equilibrium and promote the uniform formation of the solid electrolyte interface film. The fifth period of time may be greater than or equal to 10 seconds and less than or equal to 80 seconds. For example, the fifth period of time may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, or 80 seconds.

[0262] The battery is continuously charged at a constant current rate at a third charging rate until its state of charge reaches the preset state of charge for aging, thus preparing it for subsequent aging processes. The third charging rate is greater than the second charging rate, which can save formation time.

[0263] According to some embodiments of this application, the preset state of charge is greater than or equal to 40% and less than or equal to 90%.

[0264] In some embodiments, the preset state of charge can be equal to 40%, 50%, 55%, 60%, 70%, 75%, 80%, or 90%.

[0265] The preset state of charge is set to be greater than or equal to 40% and less than or equal to 90% in order to prepare for the aging process.

[0266] It should be noted that the battery formation method provided in this application can employ a negative pressure formation process, so that the gas generated during formation can be discharged in a timely manner, thereby improving the stability and consistency of the solid electrolyte interface film. For example, the pressure inside the battery cell can be adjusted to -80±5 kPa through a negative pressure machine connected to the battery cell's electrolyte injection port for formation.

[0267] The battery formation method provided in this application can employ a high-temperature formation process to improve the consistency of the solid electrolyte interface film. For example, the temperature used during formation can be 40 degrees Celsius to 60 degrees Celsius. In some embodiments, the temperature used during formation is 45 degrees Celsius.

[0268] In some embodiments, the battery formation method provided in this application may also employ open-ended formation or closed-ended formation processes, and the battery formation method provided in this application may also employ a low-temperature formation process.

[0269] After the battery continues to be charged at a constant current rate at the third charging rate until the battery's state of charge reaches the preset state of charge for aging, the battery can be subjected to processes such as secondary electrolyte injection, welding of sealing nails, and high-temperature aging.

[0270] This application provides a battery formation apparatus configured to perform any of the above-described battery formation methods.

[0271] A battery formation device is used to perform formation processing on batteries.

[0272] It is understood that the battery formation apparatus provided in this application, by applying any of the above-mentioned battery formation methods, has all the beneficial effects of the above-mentioned battery formation methods, which will not be elaborated here.

[0273] This application provides a battery manufacturing method, which includes any of the above-described battery formation methods.

[0274] A battery manufacturing method is used to manufacture batteries. In some embodiments, the battery manufacturing method further includes methods for injecting electrolyte and aging the battery.

[0275] It is understood that the battery production method provided in this application, by applying any of the above-mentioned battery formation methods, has all the beneficial effects of the above-mentioned battery formation methods, which will not be elaborated here.

[0276] This application provides a battery production system that includes any of the above-described battery formation apparatuses.

[0277] A battery production system is used to produce batteries. In some embodiments, the battery production system further includes means for casing, welding, encapsulating, and aging batteries.

[0278] It is understood that the battery production system provided in this application, by applying any of the above-mentioned battery formation apparatuses, has all the beneficial effects of the battery formation apparatuses, which will not be elaborated further here.

[0279] This application provides a battery, which is manufactured using any of the battery manufacturing methods described above.

[0280] The battery can be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery can be a secondary battery or a primary battery.

[0281] It is understood that the battery provided in this application is produced by applying any of the above-mentioned battery production methods, and therefore has all the beneficial effects of the above-mentioned battery production methods, which will not be repeated here.

[0282] This application provides an electrical device that includes any of the batteries described above, the batteries being used to provide electrical energy.

[0283] Electrical devices can include mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, and so on.

[0284] It is understood that the electrical device provided in this application, by using any of the aforementioned batteries, has all the beneficial effects of the aforementioned batteries, which will not be elaborated further here.

[0285] This application provides an energy storage device, which includes any of the above-described batteries, the batteries being used to store electrical energy.

[0286] Energy storage devices can include, but are not limited to, centralized energy storage devices (such as containerized energy storage devices), distributed energy storage devices, mobile energy storage devices, wearable energy storage devices, and so on.

[0287] It is understood that the energy storage device provided in this application, by using any of the aforementioned batteries, possesses all the beneficial effects of the aforementioned batteries, which will not be elaborated further here.

[0288] The battery formation method of this application is described below with reference to a specific embodiment. Figure 11 As shown, Figure 11 This is a flowchart of another battery formation method according to some embodiments of this application.

[0289] Battery formation methods include:

[0290] Step SR1: Let the battery rest for a first duration. The first duration is 60 seconds.

[0291] Step S101: Charge the battery at a constant current rate using a second sub-charge rate until the battery voltage reaches the second target film formation voltage. The second sub-charge rate is 0.05C.

[0292] Step S20: Perform a first constant-voltage charge on the battery using the second target film formation voltage and continue for a first preset duration. The first preset duration is 30 minutes.

[0293] Step SR2: Allow the battery to rest for a second duration, which is 60 seconds.

[0294] Step S301: Charge the battery at a constant current rate using a first sub-charge rate until the battery voltage reaches the first target film formation voltage. The first sub-charge rate is 0.05C.

[0295] Step S40: Perform a second constant-voltage charge on the battery at the first target film-forming voltage and continue for a second preset duration. The second preset duration is 30 minutes.

[0296] Step SR3: Let the battery rest for a third period of time. The third period of time is 10 seconds to 60 seconds.

[0297] Step S50: Continue charging the battery at a constant current rate using the second charging rate until the battery's state of charge reaches the cutoff state of the film formation reaction. The second charging rate is 0.1C. The third preset duration for continuing constant current charging at the second charging rate can be set to 60 minutes.

[0298] Step SR4: Allow the battery to rest for a fourth duration. This fourth duration is 10 to 60 seconds.

[0299] Step S4: Continue charging the battery at a constant current rate using the third charging rate until the battery's state of charge reaches the preset state of charge for aging. The third charging rate is 0.33C. The duration of this constant current charging at the third charging rate can be set to 100 minutes.

[0300] Step SR5: Allow the battery to rest for a fifth period of time. This fifth period is 10 to 60 seconds.

[0301] After step SR5, the battery can undergo secondary electrolyte injection, welding of sealing nails, high-temperature aging, and other processes.

[0302] Figure 12The figures shown are comparative test results for some embodiments of this application. Taking lithium-ion batteries as an example, different battery formation methods are used to form the same battery for comparative verification. Here, "the same battery" means that the materials, specifications, manufacturing processes, and conditions of each component in the battery are identical. For example, the batteries used in each scheme (i.e., batteries 1 to 4 below) can be products from the same batch produced on the same production line.

[0303] To ensure the uniformity of the battery formation method's effectiveness, multiple batteries can be used for experimental verification within each scheme, forming parallel schemes for that scheme. The parallel schemes use the same batteries, and the battery formation and cycle testing methods are identical. For example, Scheme 1 includes two parallel schemes. The batteries used in both parallel schemes are from the same batch produced on the same production line, and the battery formation and cycle testing methods applied in both parallel schemes are identical.

[0304] The battery formation method used in any parallel scheme of Scheme 1 is as follows: Figure 11 As shown.

[0305] The battery formation methods used in battery 2 in any parallel scheme of Scheme 2 include:

[0306] Step SR1: Let battery 2 stand still for a first duration. The first duration is 60 seconds.

[0307] Step S11: Charge battery 2 at a constant current rate using a first charging rate until the voltage of battery 2 reaches the second target film formation voltage. The first charging rate is 0.05C.

[0308] Step S22: Charge battery 2 at a constant voltage using the second target film formation voltage for a preset duration. The preset duration is 30 minutes.

[0309] Step SR2: Let battery 2 stand for a second duration. The second duration is 60 seconds.

[0310] Step S3: Charge battery 2 at a constant current rate using a second charging rate until the state of charge of battery 2 reaches the cutoff state of film formation reaction. The second charging rate can be 0.05C to 0.1C. In this step, battery 2 can be charged first at 0.05C and then at 0.1C.

[0311] Step SR4: Let battery 2 stand for a fourth duration. The fourth duration is 10 to 60 seconds.

[0312] Step S4: Continue charging battery 2 at a constant current rate using the third charging rate until the state of charge of battery 2 reaches the preset state of charge for aging. The third charging rate is 0.33C. The duration of this constant current charging at the third charging rate can be set to 100 minutes.

[0313] Step SR5: Let battery 2 stand for a fifth period of time. The fifth period of time is 10 seconds to 60 seconds.

[0314] The battery formation methods used in battery 3 in any parallel scheme of Scheme 3 include:

[0315] Step SR1: Let battery 3 stand still for a first duration. The first duration is 60 seconds.

[0316] Step S111: Charge battery 3 at a constant current rate until the voltage of battery 3 reaches the first target film formation voltage. The first charging rate is 0.05C.

[0317] Step S222: Perform a second constant-voltage charge on battery 3 at the first target film formation voltage and continue for a second preset duration. The second preset duration is 30 minutes.

[0318] Step SR3: Let battery 3 stand for a third duration. The third duration is 10 to 60 seconds.

[0319] Step S3: Continue charging battery 3 at a constant current rate using the second charging rate until the state of charge of battery 3 reaches the cutoff state of film formation reaction. The second charging rate is 0.1C. The third preset duration for continuing constant current charging of battery 3 at the second charging rate can be set to 60 minutes.

[0320] Step SR4: Let battery 3 stand for a fourth duration. The fourth duration is 10 to 60 seconds.

[0321] Step S4: Continue charging battery 3 at a constant current rate using the third charging rate until the battery's state of charge reaches the preset state of charge for aging. The third charging rate is 0.33C. The duration of this constant current charging at the third charging rate can be set to 100 minutes.

[0322] Step SR5: Let battery 3 stand for a fifth period of time. The fifth period of time is 10 seconds to 60 seconds.

[0323] The battery formation method used for battery 4 in any parallel scheme of Scheme 4 is as follows:

[0324] Step ST1: Charge battery 4 at a constant current rate of 0.05C until the state of charge of battery 4 reaches 10%.

[0325] Step ST2: Let battery 4 stand for 60 seconds.

[0326] Step ST3: Charge battery 4 at a constant current rate of 0.1C until the state of charge of battery 4 reaches 20%.

[0327] Step ST4: Let battery 4 stand for 10 to 60 seconds.

[0328] Step ST5: Continue to charge battery 4 at a constant current rate of the third charging rate until the battery's state of charge reaches the preset state of charge for aging.

[0329] Step ST6: Let battery 4 stand for 10 to 60 seconds.

[0330] After steps SR5 and ST6, the same secondary liquid injection, welding of sealing nails, and high-temperature aging processes can be performed on batteries 1 to 4.

[0331] During experimental verification, the batteries in each parallel scheme from Scheme 1 to Scheme 4 were subjected to cyclic testing using the following method:

[0332] Step SA1: Let stand for 10 minutes.

[0333] Step SA2: Perform constant current charging at a charging rate of 1.0C until the battery voltage reaches the upper charging limit voltage. Then, perform constant voltage charging at a charging rate of 0.05C until the battery voltage reaches the full charge voltage. The full charge voltage refers to the voltage corresponding to a battery state of charge of 100%.

[0334] Step SA3: Let stand for 10 minutes.

[0335] Step SA4: Perform constant current discharge at a discharge rate of 1.0C until the battery voltage reaches the lower discharge limit voltage.

[0336] Step SA5: Perform constant current discharge at a discharge rate of 0.05C until the battery voltage reaches the voltage corresponding to the battery's state of charge of 0%.

[0337] Step SA6: Repeat steps SA1~SA5 a total of 400 times to obtain the test results as follows. Figure 12 As shown.

[0338] according to Figure 12 It can be seen that, compared with Scheme 4, Schemes 3 and 2 can improve the film quality of the solid electrolyte interface film to some extent, thereby increasing the battery life. Scheme 1 can significantly improve the film quality of the solid electrolyte interface film and significantly increase the battery life.

[0339] Therefore, in the battery formation method, the first target film formation voltage determined by the differential voltage-voltage change curve can improve the film formation quality of the organic phase of the solid electrolyte interface film, thereby improving the film formation quality of the solid electrolyte interface film.

[0340] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery formation method, characterized in that, The battery formation method includes: The battery is charged until its voltage reaches the second target film-forming voltage; the second target film-forming voltage is the voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface film inside the battery. The battery is charged under constant voltage at the second target film formation voltage; Continue charging the battery until the battery voltage reaches the first target film formation voltage; The battery is charged under constant voltage at the first target film formation voltage; Wherein, the first target film-forming voltage is the negative electrode of the battery entering LiC during the organic phase film-forming reaction of the solid electrolyte interface film within the battery. 24 The corresponding voltage, the first target film formation voltage is determined according to the voltage corresponding to the first trough in the differential voltage-voltage change curve of the differential voltage value of the battery as a function of the battery voltage.

2. The battery formation method according to claim 1, characterized in that, Charging the battery until its voltage reaches the first target film-forming voltage includes: The battery is charged at a constant current rate at a first charging rate until the voltage of the battery reaches the first target film formation voltage. Wherein, the first charging rate is less than 0.1C.

3. The battery formation method according to claim 1, characterized in that, Charging the battery until its voltage reaches the first target film-forming voltage includes: The battery is charged at a constant current rate at a first sub-charge rate until the voltage of the battery reaches the first target film formation voltage. Charging the battery until its voltage reaches the second target film-forming voltage includes: The battery is charged at a constant current rate at a second sub-charge rate until the voltage of the battery reaches the second target film formation voltage; Wherein, both the first sub-charging rate and the second sub-charging rate are less than 0.1C.

4. The battery formation method according to claim 3, characterized in that, The first sub-charge rate and the second sub-charge rate are equal.

5. The battery formation method according to any one of claims 1 to 4, characterized in that, The second target film formation voltage is determined according to the following method: Obtain the differential capacitance-voltage change curve, which characterizes the differential capacitance value of the battery as a function of the battery voltage, during the first charge of the battery; The battery voltage corresponding to the inorganic phase film-forming reaction that characterizes the solid electrolyte interface film in the differential capacitance-voltage change curve is determined as the second target film-forming voltage.

6. The battery formation method according to claim 5, characterized in that, The method of determining the battery voltage corresponding to the inorganic phase film-forming reaction characterizing the solid electrolyte interface film in the differential capacitance-voltage change curve as the second target film-forming voltage includes: Determine the first voltage corresponding to the peak value of the first peak in the differential capacitance-voltage change curve; The first voltage is determined as the second target film formation voltage.

7. The battery formation method according to claim 5, characterized in that, The differential capacitance-voltage change curve is determined according to the following method: The charging capacity and battery voltage of the sample battery at multiple sampling time points during the first charging of the sample battery are collected; wherein, the sample battery and the battery are the same type of battery; The differential capacitance value is calculated based on the collected charging capacity and battery voltage. The differential capacitance value is determined based on the ratio of the difference between the charging capacity obtained at two adjacent sampling time points to the difference between the battery voltage. The differential capacitance-voltage variation curve is determined based on the differential capacitance value and the battery voltage.

8. The battery formation method according to any one of claims 1 to 4, characterized in that, The second target film formation voltage is greater than or equal to 2V and less than or equal to 2.8V.

9. The battery formation method according to any one of claims 1 to 4, characterized in that, The method further includes: Obtain the differential voltage-voltage change curve, which characterizes the change of the differential voltage value of the battery as a function of the battery voltage during the first charge of the battery; The voltage corresponding to the first trough in the differential voltage-voltage change curve is determined to be the third voltage; The third voltage is determined as the first target film-forming voltage.

10. The battery formation method according to any one of claims 1 to 4, characterized in that, The differential voltage-voltage change curve is determined according to the following method: The charging capacity and battery voltage of the sample battery at multiple sampling time points during the first charging of the sample battery are collected; wherein, the sample battery and the battery are the same type of battery; The differential voltage value is calculated based on the collected charging capacity and battery voltage; the differential voltage value is determined based on the ratio of the difference between the battery voltages obtained at two adjacent sampling time points to the difference between the charging capacities. The differential voltage-voltage change curve is determined based on the differential voltage value and the battery voltage.

11. The battery formation method according to any one of claims 1 to 4, characterized in that, The first target film formation voltage is greater than or equal to 3V and less than or equal to 3.3V.

12. The battery formation method according to claim 2, characterized in that, After the battery is charged at a constant voltage using the first target film-forming voltage, the method further includes: The battery is continuously charged at a second charging rate until the battery reaches the state of charge at which the film formation reaction is cut off. Wherein, in the charged state where the film-forming reaction is cut off, the film-forming reaction of the solid electrolyte interface film inside the battery has been completed, and the second charging rate is greater than or equal to the first charging rate.

13. The battery formation method according to claim 3, characterized in that, After the battery is charged at a constant voltage using the first target film-forming voltage, the method further includes: The battery is continuously charged at a second charging rate until the battery reaches the state of charge at which the film formation reaction is cut off. Wherein, in the charged state where the film-forming reaction is cut off, the film-forming reaction of the solid electrolyte interface film inside the battery has been completed, the second charging rate is greater than the first sub-charging rate, and the second charging rate is greater than the second sub-charging rate.

14. The battery formation method according to claim 12 or 13, characterized in that, The second charging rate is greater than or equal to 0.1C and less than or equal to 0.3C.

15. The battery formation method according to claim 12 or 13, characterized in that, The cutoff state of charge for the film-forming reaction is greater than or equal to 15% and less than or equal to 35%.

16. The battery formation method according to claim 12 or 13, characterized in that, The method of continuing to charge the battery at a constant current rate at a second charging rate until the battery reaches the state of charge at which the film-forming reaction is cut off also includes: The battery is continuously charged at a constant current rate at the third charging rate until the battery reaches the preset state of charge for aging. The third charging rate is greater than the second charging rate.

17. The battery formation method according to claim 16, characterized in that, The preset state of charge is greater than or equal to 40% and less than or equal to 90%.

18. A battery manufacturing method, characterized in that, Includes the battery formation method as described in any one of claims 1 to 17.

19. A battery, characterized in that, The battery is manufactured using the battery production method as described in claim 18.

20. An electrical appliance, characterized in that, Includes the battery as described in claim 19, the battery being used to provide electrical energy.

21. An energy storage device, characterized in that, Includes the battery as described in claim 19, wherein the battery is used to store electrical energy.

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