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

Abstract

The invention provides a battery formation method and device, a battery and a production method, system and device of the battery, and belongs to the technical field of batteries. A first target film forming voltage is determined by characterizing a differential voltage-voltage change curve of an organic phase film forming reaction of the solid electrolyte interfacial film. In the battery formation method, the first target film forming voltage determined by the differential voltage-voltage change curve is used for constant-voltage charging, so that the film forming quality of the solid electrolyte interfacial film can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery formation method and device, a battery and a production method, system and device thereof. Background Art

[0002] Energy conservation and emission reduction are the key to sustainable social development. Batteries are widely used in various electrical devices or energy storage systems because they can store or release energy as needed, becoming an important part of promoting energy transformation and sustainable development. For the new energy industry, battery technology is an important factor in its development.

[0003] During the first charging process of the battery, if the film quality of the solid electrolyte interface film formed in the battery is poor, during the recycling of the battery, the solid electrolyte interface film will undergo oxidative decomposition and re-repair process, causing irreversible consumption of active lithium ions and affecting the performance and life of the battery. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems in the background technology. To this end, one object of the present application is to provide a battery formation method and device, a battery and a production method, system and device thereof, so as to improve the film formation quality of the solid electrolyte interface film in the battery.

[0005] The embodiment of the first aspect of the present application provides a battery formation method, the battery formation method comprising: charging the battery until the voltage of the battery reaches a first target film-forming voltage; and charging the battery at a constant voltage 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 interface film in the battery, and 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 of the differential voltage value of the battery as the voltage of the battery changes.

[0006] In the technical solution of the embodiment of the present application, the first target film-forming voltage is determined by the differential voltage-voltage change curve that can characterize the organic phase film-forming reaction of the solid electrolyte interface film. The battery is charged during formation so that the battery voltage is charged to the first target film-forming voltage, and the battery is charged at a constant voltage at the first target film-forming voltage, so as to improve the organic phase film-forming quality of the solid electrolyte interface film by using the first target film-forming voltage determined by the differential voltage-voltage change curve that reflects the organic phase film-forming reaction of the solid electrolyte interface film, and then improve the film-forming quality of the solid electrolyte interface film.

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

[0008] In some embodiments, the charging of the battery until the voltage of the battery reaches the first target film-forming voltage includes: charging the battery until the voltage of the battery reaches the second target film-forming voltage; and constant-voltage charging the battery at the second target film-forming voltage. In this way, it is beneficial to improve the inorganic phase film-forming quality of the solid electrolyte interface film while improving the organic phase film-forming quality of the solid electrolyte interface film, which in turn helps to further make the formed solid electrolyte interface film more uniform and stable, thereby further improving the film-forming quality of the solid electrolyte interface film in the battery.

[0009] In some embodiments, charging the battery until the voltage of the battery reaches the first target film-forming voltage includes: charging the battery at a first sub-charging rate with a constant current until the voltage of the battery reaches the first target film-forming voltage. Charging the battery until the voltage of the battery reaches the second target film-forming voltage includes: charging the battery at a second sub-charging rate with a constant current until the voltage of the battery reaches the second target film-forming voltage. Wherein, both the first sub-charging rate and the second sub-charging rate are less than 0.1C. In this way, it is beneficial to further extend the film-forming time of forming the solid electrolyte interface film and further reduce the polarization of the battery.

[0010] In some embodiments, the first sub-charge rate and the second sub-charge rate are equal, which is beneficial for improving the film 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 the following method: obtaining a differential capacitance-voltage change curve that characterizes the change of the differential capacitance value of the battery with the voltage of the battery when the battery is charged for the first time; and 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. In this way, the second target film-forming voltage can be determined by the differential capacitance-voltage change curve that can characterize the inorganic phase film-forming reaction of the solid electrolyte interface 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 subsequently extending the inorganic phase film-forming reaction time of the solid electrolyte interface film in the battery.

[0013] In some embodiments, the differential capacitance-voltage change curve is determined by the following method: collecting the charging capacity and battery voltage at multiple sampling time nodes when the sample battery is charged for the first time; wherein the sample battery and the battery are the same battery; calculating the differential capacitance value 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 nodes to the difference between the battery voltages; determining the differential capacitance-voltage change curve based on the differential capacitance value and the battery voltage. By using the charging capacitance and battery voltage corresponding to multiple sampling time nodes when the sample battery is charged for the first time, the differential capacitance value is obtained, and then the differential capacitance-voltage change curve for determining the first voltage is obtained, so as to obtain a more accurate second target film forming voltage.

[0014] In some embodiments, the second target film-forming voltage is greater than or equal to 2 V and less than or equal to 2.8 V. In this way, the voltage corresponding to the inorganic phase film-forming reaction that characterizes the solid electrolyte interface film is covered, so that in the subsequent steps, the film-forming reaction time of the inorganic phase of the solid electrolyte interface film in the battery can be extended, thereby improving the film-forming quality of the inorganic phase of the solid electrolyte interface film.

[0015] In some embodiments, the battery formation method further comprises: obtaining a differential voltage-voltage change curve representing a differential voltage value of the battery as the voltage of the battery changes when the battery is charged for the first time; determining a voltage in the differential voltage-voltage change curve corresponding to the negative electrode of the battery entering the LiC 24 The second voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interface film is determined as the first target film-forming voltage. The second voltage in the differential voltage-voltage change curve that can characterize the organic phase film-forming reaction of the solid electrolyte interface film is determined as the first target film-forming voltage, so that the film-forming quality of the solid electrolyte interface film can be improved by subsequently extending the organic phase film-forming reaction time of the solid electrolyte interface film in the battery.

[0016] In some embodiments, the battery formation method further includes: obtaining a differential voltage-voltage change curve that characterizes the change of the differential voltage value of the battery with the voltage of the battery when the battery is charged for the first time; determining the voltage corresponding to the first trough in the differential voltage-voltage change curve as the third voltage; and determining the third voltage as the first target film-forming voltage. By determining the voltage corresponding to the first trough in the differential voltage-voltage change curve as the first target film-forming voltage, the first target film-forming voltage can be quickly determined based on the differential voltage-voltage change curve.

[0017] In some embodiments, the differential voltage-voltage change curve is determined by the following method: collecting the charging capacity and battery voltage at multiple sampling time nodes when the sample battery is charged for the first time; wherein the sample battery and the battery are the same 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 voltage obtained at two adjacent sampling time nodes to the difference between the charging capacity; determining the differential voltage-voltage change curve based on the differential voltage value and the battery voltage. By using the charging capacitance and battery voltage corresponding to multiple sampling time nodes when the sample battery is charged for the first time, the differential voltage value is obtained, and then the differential voltage-voltage change curve for determining the second voltage is obtained, so as to obtain a more accurate first target film forming voltage.

[0018] In some embodiments, the first target film-forming voltage is greater than or equal to 3 V and less than or equal to 3.3 V. In this way, the voltage corresponding to the organic phase film-forming reaction characterizing the solid electrolyte interface film is covered, so that the film-forming reaction time of the organic phase of the solid electrolyte interface film in the battery can be extended in the subsequent steps, thereby improving the organic phase film-forming quality of the solid electrolyte interface film.

[0019] In some embodiments, after the battery is charged at a constant voltage with a target film-forming voltage, the method further includes: continuing to charge the battery at a second charging rate at a constant current until the battery's state of charge reaches a film-forming reaction cutoff state of charge. In this case, the film-forming reaction of the solid electrolyte interface film inside the battery is completed under the film-forming reaction cutoff state of charge, and the second charging rate is greater than or equal to the first charging rate. In this way, the organic phase of the solid electrolyte interface film can be further grown, and the solid electrolyte interface film can be further grown, and the formation time can be shortened.

[0020] In some embodiments, after the battery is charged at a constant voltage with a first target film-forming voltage, the method further includes: continuing to charge the battery at a constant current with a second charging rate until the battery's state of charge reaches a film-forming reaction cutoff state of charge. Wherein, at the film-forming reaction cutoff state of charge, 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. In this way, the organic phase of the solid electrolyte interface film can be further grown, and the solid electrolyte interface film can be assisted to further grow, and the formation time can be shortened.

[0021] In some embodiments, the second charging rate is greater than or equal to 0.1 C and less than or equal to 0.3 C. In this way, the solid electrolyte interface film can be assisted to further grow and the film formation quality of the solid electrolyte interface film can be improved.

[0022] In some embodiments, the film forming reaction cut-off state of charge is greater than or equal to 15% and less than or equal to 35%. In this way, the battery formation method can be more suitable for actual application conditions and the application rate of the battery formation method can be improved.

[0023] In some embodiments, the battery is continuously charged at a second charging rate with a constant current until the state of charge of the battery reaches the film-forming reaction cut-off state of charge, and further includes: the battery is continuously charged at a third charging rate with a constant current until the state of charge of the battery reaches a preset state of charge for aging. The third charging rate is greater than the second charging rate. In this way, formation time can be saved while preparing for the subsequent aging process.

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

[0025] An embodiment of a second aspect of the present application provides a battery formation device, which is configured to perform any of the above-mentioned battery formation methods.

[0026] An embodiment of the third aspect of the present application provides a battery production method, which includes any of the above-mentioned battery formation methods.

[0027] An embodiment of a fourth aspect of the present application provides a battery production system, which includes any of the above-mentioned battery formation devices.

[0028] An embodiment of the fifth aspect of the present application provides a battery, which is manufactured using any of the above-mentioned battery production methods.

[0029] An embodiment of the sixth aspect of the present application provides an electrical device, which includes any of the above-mentioned batteries, and the battery is used to provide electrical energy.

[0030] An embodiment of the seventh aspect of the present application provides an energy storage device, which includes any of the above-mentioned batteries, and the battery is used to store electrical energy.

[0031] It should be noted that the above description is only an overview of the technical solution of the present application, and similar expressions such as "the first aspect" and "the second aspect" in the above description should be understood as descriptions for the convenience of description, and should not be understood as technical divisions. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0033] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application; Figure 2 This is a schematic diagram of the structure of the box and battery cells in some embodiments of the present application; Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application; Figure 4 A flow chart of a battery formation method according to some embodiments of the present application; Figure 5 A flowchart of another battery formation method according to some embodiments of the present application; Figure 6 A flowchart of another battery formation method according to some embodiments of the present application; Figure 7 Schematic diagram of differential voltage-voltage variation curves of some embodiments of the present application; Figure 8 A flowchart of another battery formation method according to some embodiments of the present application; Fig. 9 The current variation curve during the constant voltage charging process of some embodiments of the present application; Fig.10 Schematic diagram of differential capacitance-voltage variation curves of some embodiments of the present application; Fig.11 A flowchart of another battery formation method according to some embodiments of the present application; Fig.12 This is a graph showing comparative test results of some embodiments of the present application.

[0034] Description of reference numerals: Vehicles 1000; Battery 100, controller 200, motor 300; Box body 10, first part 11, second part 12; Battery cell 20, end cover 21, electrode terminal 21a, shell 22, electrode assembly 23, and electrode tab 23a. DETAILED DESCRIPTION

[0035] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0037] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0038] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0040] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0041] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0042] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0043] At present, judging from the development of the market situation, the application of batteries is becoming more and more extensive. Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in various electronic devices, such as electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, as well as military equipment and aerospace and other fields. With the continuous expansion of battery application areas, its market demand is also constantly expanding. The quality of batteries is a key factor affecting the market share of battery manufacturers.

[0044] In the battery manufacturing process, the assembled battery needs to go through three steps of injection, formation and aging to produce a finished battery. The solid electrolyte interphase (SEI) film formed in the formation stage is crucial to the battery's cycle life, safety and performance. The film quality of the solid electrolyte interphase film directly affects the quality of the battery.

[0045] For example, let's take lithium-ion batteries as an example. The negative electrode of the battery is made of graphite material. Since the working potential of graphite is incompatible with the electrochemical stability window of the electrolyte, a side reaction between graphite and the electrolyte will occur when the lithium-ion battery is charged for the first time, generating a solid-liquid intermediate phase (i.e., solid electrolyte interface membrane). The inner layer of the solid electrolyte interface membrane is mainly composed of inorganic phases such as LiF, and the outer layer of the solid electrolyte interface membrane is mainly composed of organic carbonates.

[0046] If the film quality of the solid electrolyte interface film is poor, the solid electrolyte interface film will undergo oxidation decomposition and repair again due to the expansion of graphite and other factors during the actual charge and discharge cycle of the lithium-ion battery. The quality of the repaired solid electrolyte interface film is low, which will lead to irreversible consumption of active lithium ions, which is directly manifested as a rapid decrease in the life of the lithium-ion battery.

[0047] Therefore, the film-forming quality of the solid electrolyte interface film will affect the performance and quality of the battery. The film-forming quality of the solid electrolyte interface film is related to the quality of the film-forming reaction of the inorganic phase and the organic phase at the solid electrolyte interface. Therefore, how to control the film-forming reaction of the solid electrolyte interface film is the key to improving the film-forming quality of the solid electrolyte interface film.

[0048] In order to determine the battery voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interface film and improve the film-forming quality of the solid electrolyte interface film, the present application provides a battery formation method, which includes: charging the battery until the battery voltage reaches a first target film-forming voltage; and charging the battery at a constant voltage 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 interface film in the battery, and 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 in which the differential voltage value of the battery changes with the voltage of the battery. The first target film-forming voltage can be determined by the differential voltage-voltage change curve that can characterize the organic phase film-forming reaction of the solid electrolyte interface film. By charging the battery during formation so that the battery voltage is charged to a first target film-forming voltage, and charging the battery at a constant voltage at the first target film-forming voltage, the first target film-forming voltage is determined by utilizing the differential voltage-voltage change curve reflecting the organic phase film-forming reaction of the solid electrolyte interface film, thereby improving the organic phase film-forming quality of the solid electrolyte interface film, and then improving the film-forming quality of the solid electrolyte interface film, thereby increasing the service life of the battery.

[0049] The battery formation method and battery formation device provided in the embodiments of the present application can be used in, but not limited to, battery cells and batteries. The battery production method and battery production system provided in the embodiments of the present application can be used in, but not limited to, producing battery cells and batteries.

[0050] The battery cells and batteries disclosed in the embodiments of the present application can be used, but not limited to, in electric devices or energy storage devices such as vehicles, ships or aircraft. A power supply system having the battery cells and batteries disclosed in the present application can be used to form the electric device or energy storage device, which is beneficial to improve the quality of the battery and provide reliability of the power supply system.

[0051] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, entertainment and communication (such as mobile phones, tablets, laptops, electric toys, etc.), production and after-sales (such as various electric tools, etc.), transportation (such as battery vehicles, electric vehicles, ships, etc.), scientific research (such as spacecraft), etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecrafts, etc.

[0052] An embodiment of the present application also provides an energy storage device that uses a battery as a power source. The energy storage device may 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.

[0053] For the convenience of description, the following embodiments are described by taking the device using a battery in one embodiment of the present application as an electrical device, and the electrical device is a vehicle as an example.

[0054] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application. Vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0055] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0056] Please refer to Figure 2 , Figure 2 The schematic diagram of the structure of the box and the battery cell provided in some embodiments of the present application. The battery 100 may include at least one battery cell 20, and the box 10 is used to provide a storage space for the battery cell 20.

[0057] The box 10 can adopt a variety of structures. For example, in some embodiments, the box 10 can include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can be a variety of shapes, such as a cylinder, a cuboid, etc.

[0058] The multiple battery cells 20 contained in the box 10 can be connected in series, parallel or mixed. Mixed means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, parallel or mixed, and then the whole body formed by the multiple battery cells 20 is contained in the box 10. Of course, it is also possible that the multiple battery cells 20 are first connected in series, parallel or mixed to form a battery module, and the multiple battery modules are then connected in series, parallel or mixed to form a whole body and contained in the box 10.

[0059] It should be noted that the battery cell 20 can be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto. The battery cell 20 can be cylindrical, flat, rectangular or in other shapes.

[0060] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the exploded structure of a battery cell provided in some embodiments of the present application. The battery cell 20 includes an end cover 21, a shell 22, an electrode assembly 23 and other functional components.

[0061] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0062] The shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte and other components. The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when it is necessary to encapsulate the interior of the shell 22, the end cap 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0063] The electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 23 may be included in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly 23, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.

[0064] Please continue reading Figure 4~Figure 6 , Figure 4 This is a flow chart of a battery formation method according to some embodiments of the present application. Figure 5 This is a flow chart of another battery formation method according to some embodiments of the present application. Figure 6 The present invention is a flowchart of another battery formation method according to some embodiments of the present application.

[0065] The present application embodiment provides a battery formation method, the battery formation method comprising: Step S1: charging the battery until the voltage of the battery reaches the target film forming voltage; Step S2: The battery is charged at a constant voltage at the target film formation voltage.

[0066] Among them, the target film forming voltage is 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.

[0067] The battery formation method provided in the present application is used in the battery to be formed. The battery to be formed is a battery that has completed the shell assembly and liquid injection, and the battery can be a battery cell of any model or specification. It is understandable that, unless otherwise specified, the embodiments of the present application are all described by taking lithium-ion batteries as an example. Lithium-ion batteries include a positive electrode, a negative electrode, and an electrolyte. The electrolyte transfers ions and ionic compounds between the positive and negative electrodes of the battery, and the main component of the electrolyte is an electrolyte. The electrolyte can be a liquid electrolyte, a solid electrolyte, or a solid-liquid composite electrolyte, etc.

[0068] Formation is a manufacturing process in the battery manufacturing process. Before the formation process, the battery manufacturing process also includes a liquid injection process. After the formation process, the battery manufacturing process also includes an aging process. The liquid injection process is the process of injecting electrolyte into the battery shell that has been deeply dehydrated by vacuum drying. The formation process is the process of charging the battery after liquid injection, and the aging process is the process of leaving the formed battery at a certain temperature for a period of time.

[0069] The injection process may be a process of vacuum baking, negative pressure injection and high temperature soaking of the battery cell after being put into the shell. The temperature corresponding to vacuum baking may be 110 degrees Celsius, and the corresponding duration may be 12 hours. The pressure corresponding to negative pressure injection may be minus 80 kPa. The temperature corresponding to high temperature soaking may be 45 degrees Celsius, and the corresponding duration may be 20 hours.

[0070] In the formation process, the battery is charged for the first time. During the charging process, the negative electrode potential of the battery gradually decreases and the battery voltage gradually increases. As the negative electrode potential of the battery gradually decreases, the negative electrode and the electrolyte in the battery will have a competitive and synergistic reaction between the organic phase and the inorganic phase at the solid-liquid interface, generating organic phase products (such as alkyl lithium carbonate (ROCO 2 Li), polycarbonate, etc.) and inorganic phase products (such as LiF, Li 2 CO 3 , Li 2 O), thereby forming a solid electrolyte interface film covering the surface of the electrode material. The solid electrolyte interface film can allow ions to pass through, but prevent electrons from passing through, thereby isolating the direct contact between the electrolyte and the electrode, so as to prevent the excessive chemical reaction inside the battery, prevent the dissolution of the electrode material and the decomposition of the electrolyte, thereby maintaining the stability of the battery.

[0071] The solid electrolyte interface film is composed of inorganic phase products and organic phase products, presenting a multilayer composite structure including an inorganic inner layer and an organic outer layer. The inorganic inner layer is in contact with the surface of the electrode facing the electrolyte, and is located between the organic inner layer and the electrode. The inorganic inner layer can provide a fast transmission channel for ions and block electron leakage. The organic outer layer can reduce the rate of diffusion of the electrolyte to the electrode surface. During formation, the inorganic phase film-forming reaction of the solid electrolyte interface film in the battery is used to form the inorganic inner layer, and the organic phase film-forming reaction of the solid electrolyte interface film in the battery is used to form the organic outer layer.

[0072] Because the solid electrolyte interface membrane can achieve the function of allowing ions to pass through and preventing electrons from passing through through the combined effect of the inorganic inner layer and the organic outer layer, and isolating the direct contact between the electrolyte and the electrode, it can prevent excessive chemical reactions inside the battery, dissolution of electrode materials, and decomposition of the electrolyte. Therefore, the film formation quality of the solid electrolyte interface membrane can be improved by improving the film formation quality of at least one of the inorganic phase film formation and the organic phase film formation of the solid electrolyte interface membrane.

[0073] Therefore, the target film-forming voltage may include the second target film-forming voltage or the first target film-forming voltage. That is, the target film-forming voltage may be the voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface film in the battery (i.e., the second target film-forming voltage), or the voltage corresponding to the organic phase film-forming reaction of the solid electrolyte interface film in the battery (i.e., the first target film-forming voltage).

[0074] Constant voltage charging means that during the process of charging the battery, a constant charging voltage is used to charge the battery. When the battery is charged at a constant voltage, the battery voltage gradually increases until it is equal to or approximately equal to the charging voltage; and the charging current gradually decreases until it is equal to or approximately equal to zero. The battery voltage can be the terminal voltage of the battery.

[0075] In some embodiments, the constant voltage charging of the battery at the target film-forming voltage in step S2 lasts for a preset time. The preset time is a pre-set time period. By charging the battery during formation so that the voltage of the battery is charged to the target film-forming voltage, and charging the battery at the target film-forming voltage for a preset time, the time of the inorganic phase film-forming reaction or the organic phase film-forming reaction of the solid electrolyte interface film in the battery is extended, which helps to form a more uniform and stable solid electrolyte interface film, improve the film-forming quality of the solid electrolyte interface film in the battery, and increase the service life of the battery.

[0076] The preset time length can be set differently according to the different performances of the inorganic phase film-forming reaction or the organic phase film-forming reaction actually occurring in the battery. Therefore, the preset time length can be determined according to the material system of the battery.

[0077] In some embodiments, the preset duration may be greater than or equal to 10 minutes, such as 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.

[0078] If the preset time is set too short (e.g., less than 300 seconds), the effect of improving the film quality of the solid electrolyte interface film is not obvious. Therefore, in some embodiments, the preset time may be greater than or equal to 10 minutes. For example, the preset time may 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.

[0079] The shorter the preset time is, the shorter the time available for the inorganic phase film-forming reaction or the organic phase film-forming reaction of the solid electrolyte interface film is, which is not conducive to improving the film-forming quality of the solid electrolyte interface film. However, the longer the preset time is, the higher the time cost required for the formation. Therefore, in order to improve the film-forming quality of the solid electrolyte interface film while reducing the formation time cost, the preset time is set to 30 minutes.

[0080] Please continue reading Figure 5 and Figure 7 , Figure 7 Schematic diagram of differential voltage-voltage change curves according to some embodiments of the present application.

[0081] When the target film formation voltage is the first target film formation voltage, the battery formation method may include: Step S111: charging the battery until the battery voltage reaches the first target film-forming voltage.

[0082] Step S222: performing constant voltage charging on the battery at the first target film forming voltage.

[0083] The first target film-forming voltage is determined according to the battery voltage corresponding to the organic phase film-forming reaction characterizing the solid electrolyte interface film in the differential voltage-voltage change curve in which the differential voltage value of the battery changes with the voltage of the battery.

[0084] The differential voltage value is a characterization of the sensitivity of the battery's voltage to changes in capacity during the charge and discharge process. The differential voltage-voltage change curve can reflect the chemical reactions and phase change processes in the electrode material. Taking a lithium-ion battery as an example, the negative electrode of the battery is a graphite electrode. When the battery is charging, lithium ions are embedded in the graphite. As lithium ions are continuously embedded in the graphite, the electrode material undergoes a phase change, affecting the composition of the organic phase of the solid electrolyte interface film. The differential voltage-voltage change curve can reflect the phase change process of the electrode material, and therefore, the differential voltage-voltage change curve can characterize the organic phase film-forming reaction of the solid electrolyte interface film. Therefore, the first target film-forming voltage can be determined based on the differential voltage-voltage change curve.

[0085] The first target film-forming voltage is determined by using a differential voltage-voltage variation curve that can characterize the organic phase film-forming reaction of the solid electrolyte interface film.

[0086] By charging the battery during formation so that the battery voltage is charged to a first target film-forming voltage, and charging the battery at a constant voltage at the first target film-forming voltage, the first target film-forming voltage is determined by utilizing the differential voltage-voltage change curve reflecting the organic phase film-forming reaction of the solid electrolyte interface film, thereby improving the organic phase film-forming quality of the solid electrolyte interface film, and then improving the film-forming quality of the solid electrolyte interface film, which is beneficial to improving the service life of the battery.

[0087] In some embodiments, the constant voltage charging of the battery at the first target film-forming voltage in step S222 lasts for a preset time. By charging the battery during formation, so that the voltage of the battery is charged to the first target film-forming voltage, and correspondingly charging the battery at the first target film-forming voltage for a preset time, the film-forming reaction time of the organic phase of the solid electrolyte interface film in the battery is prolonged, which helps to form a dense organic outer layer, so as to reduce the side reaction between the electrolyte and the electrode, thereby helping to make the formed solid electrolyte interface film more uniform and stable, and improving the film-forming quality of the solid electrolyte interface film in the battery.

[0088] Please continue reading Figure 6 , when the target film forming voltage is the second target film forming voltage, the battery formation method may include: Step S11: charging the battery until the battery voltage reaches the second target film-forming voltage.

[0089] Step S22: performing constant voltage charging on the battery at the second target film-forming voltage.

[0090] In some embodiments, the battery is charged at a constant voltage for a preset time at the second target film-forming voltage in step S22. By charging the battery during formation so that the battery voltage is charged to the second target film-forming voltage, and charging the battery at a constant voltage for a preset time at the second target film-forming voltage, the inorganic phase film-forming reaction time of the solid electrolyte interface film in the battery is prolonged, which helps to arrange the inorganic components more orderly, improve the ionic conductivity of the solid electrolyte interface film, and reduce the incidence of film-forming side reactions, thereby helping to make the formed solid electrolyte interface film more uniform and stable, and improving the film-forming quality of the solid electrolyte interface film in the battery.

[0091] In some embodiments, before step S1, step S11 or step S111, the battery formation method may further include: leaving the battery to stand for a first time period, wherein the first time period may be 30 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds.

[0092] 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 (such as 30 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds) to help the chemical reaction inside the battery reach equilibrium and promote uniform film formation of the solid electrolyte interface film.

[0093] According to some embodiments of the present application, charging the battery until the voltage of the battery reaches the target film forming voltage includes: The battery is charged at a first charging rate with a constant current until the voltage of the battery reaches a target film-forming voltage.

[0094] Among them, the first charging rate is less than 0.1C.

[0095] By adopting a first charging rate of less than 0.1C to charge the battery at a constant current until the voltage of the battery reaches the target film-forming voltage, it is beneficial to prolong the film-forming time of the solid electrolyte interface film and to reduce the polarization of the battery.

[0096] That is, when the target film forming voltage is the first target film forming voltage, charging the battery until the voltage of the battery reaches the first target film forming voltage includes: The battery is charged at a first charging rate with a constant current until the voltage of the battery reaches a first target film-forming voltage.

[0097] Among them, the first charging rate is less than 0.1C.

[0098] By adopting a first charging rate less than 0.1C to charge the battery at a constant current until the battery voltage reaches a first target film-forming voltage, it is beneficial to prolong the film-forming time of the organic film forming the solid electrolyte interface film and to reduce the polarization of the battery.

[0099] When the target film forming voltage is the second target film forming voltage, charging the battery until the voltage of the battery reaches the second target film forming voltage includes: The battery is charged at a first charging rate with a constant current until the voltage of the battery reaches a second target film-forming voltage.

[0100] Among them, the first charging rate is less than 0.1C.

[0101] By adopting a first charging rate less than 0.1C to charge the battery at a constant current until the battery voltage reaches a second target film-forming voltage, it is beneficial to prolong the film-forming time of the inorganic film forming the solid electrolyte interface film and to reduce the polarization of the battery.

[0102] The charge rate refers to the charging current required to charge the battery to its rated capacity within a specified time.

[0103] Constant current charging means that during the process of charging the battery, a constant charging current is used to charge the battery. When the battery is charged with constant current, the battery voltage and the charging voltage gradually rise. When the battery voltage rises to or approximately equals to the set upper limit voltage, the constant current charging is stopped. The battery voltage can be the terminal voltage of the battery.

[0104] The value of 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.

[0105] The smaller the first charge rate, the longer the time available for the inorganic phase film-forming reaction or organic phase film-forming reaction of the solid electrolyte interface film to occur in the battery, and the more conducive it is to generate a dense and stable solid electrolyte interface film. However, the smaller the first charge rate, the slower the battery charging speed, resulting in an increase in the time cost of battery formation. Therefore, in order to take into account both the time cost and the quality of the generated solid electrolyte interface film, the first charge rate can be set to 0.05C.

[0106] Please continue reading Figure 8 , Figure 8 The present invention is a flowchart of another battery formation method according to some embodiments of the present application.

[0107] According to some embodiments of the present application, a battery formation method includes: Step S10: charging the battery until the voltage of the battery reaches the second target film forming voltage; Step S20: charging the battery at a constant voltage with a second target film-forming voltage for a first preset time period; Step S30: charging the battery until the voltage of the battery reaches the first target film-forming voltage; Step S40: performing constant voltage charging on the battery at the first target film forming voltage.

[0108] The first target film-forming voltage here is the same as the aforementioned first target film-forming voltage, and the second target film-forming voltage here is the same as the aforementioned second target film-forming voltage.

[0109] The battery is charged so that the battery voltage is charged to a second target film-forming voltage, and the battery is charged at a first constant voltage at the second target film-forming voltage for a first preset time period to extend the inorganic phase film-forming reaction time of the solid electrolyte interface film in the battery, so as to further improve the film-forming quality of the solid electrolyte interface film.

[0110] Since the second target film-forming voltage is usually different from the first target film-forming voltage, if one wants to improve the film-forming quality of the solid electrolyte interface film by simultaneously improving the quality of the inorganic phase film-forming and the organic phase film-forming of the solid electrolyte interface film, one can use a method of step-by-step charging to the corresponding target film-forming voltages, and perform constant voltage charging at the respective corresponding target charging voltages to improve the quality of the inorganic phase film-forming and the organic phase film-forming of the solid electrolyte interface film, thereby improving the film-forming quality of the solid electrolyte interface film.

[0111] In some embodiments, the second target film-forming voltage is less than the first target film-forming voltage. As the battery is charged, the battery voltage gradually increases, so the battery voltage will first reach the second target film-forming voltage, and then reach the first target film-forming voltage as the charging continues. Therefore, in the battery formation method, the battery voltage can be first charged to the second target film-forming voltage, and the battery can be charged at a constant voltage for a preset time at the second target film-forming voltage, and then the battery voltage can be charged to the first target film-forming voltage, and the battery can be charged at a constant voltage at the first target film-forming voltage.

[0112] In some embodiments, the battery is charged at a constant voltage at the first target film-forming voltage for a second preset time in step S30. The film-forming reaction time of the organic phase of the solid electrolyte interface film in the battery is prolonged by charging the battery at a constant voltage at the first target film-forming voltage for the second preset time. In this way, it is beneficial to improve the film-forming quality of the inorganic phase of the solid electrolyte interface film while improving the film-forming quality of the organic phase of the solid electrolyte interface film, which in turn helps to further make the formed solid electrolyte interface film more uniform and stable, thereby further improving the film-forming quality of the solid electrolyte interface film in the battery.

[0113] The first preset time length and the second preset time length are both preset time periods. The first preset time length can be set to be different according to the performance of the inorganic phase film-forming reaction of the solid electrolyte interface film in the battery, and the second preset time length can be set to be different according to the performance of the organic phase film-forming reaction of the solid electrolyte interface film in the battery. Therefore, the first preset time length and the second preset time length can be set to be different according to the different batteries actually required or used.

[0114] 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.

[0115] If the first preset time is set too short (e.g., less than 300 seconds), the improvement effect on the inorganic phase film quality of the solid electrolyte interface film is not obvious. Therefore, the longer the first preset time is, the more conducive it is to form a solid electrolyte interface film with better quality. However, the longer the first preset time is, the greater the time cost of battery formation. In addition, please continue to refer to Fig. 9 , Fig. 9 This is a current change curve during the constant voltage charging process of some embodiments of the present application. The horizontal axis represents time, and the unit of the horizontal axis is seconds (s). The vertical axis is the charging current during the constant voltage charging process, and the unit of the vertical axis is milliamperes (mA). When the battery is charged with the second target film-forming voltage (denoted as X1) for the first time at a constant voltage, the corresponding charging current will show a downward trend and gradually stabilize over time. During the first constant voltage charging process, the amount of electricity charged into the battery after the corresponding charging current reaches the current inflection point is relatively small. At this time, if the cut-off time of the first constant voltage charging is located at the current inflection point of the corresponding current change curve and after the current inflection point, the quality improvement of the inorganic phase film formation of the solid electrolyte interface film will no longer be significantly increased. Therefore, in order to take into account the film formation quality and time cost of the solid electrolyte interface film, the first preset duration can be set to 30 minutes.

[0116] In some embodiments, the second preset duration may be greater than or equal to 10 minutes and less than or equal to 120 minutes. For example, the second 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.

[0117] If the second preset time is set too short (e.g., less than 300 seconds), the improvement effect on the quality of the organic phase film formation of the solid electrolyte interface membrane is not obvious. Therefore, the longer the second preset time is, the more conducive it is to forming a solid electrolyte interface membrane with better quality. However, the longer the second preset time is, the greater the time cost of battery formation. In addition, please continue to refer to Fig. 9, when the battery is charged with a second constant voltage at the first target film-forming voltage (denoted as X2), the corresponding charging current will show a downward trend and gradually stabilize over time. During the second constant voltage charging process, the amount of electricity charged into the battery after the corresponding charging current reaches the current inflection point is relatively small. At this time, if the cutoff time of the second constant voltage charging is located at the current inflection point of the corresponding current change curve and after the current inflection point, the quality improvement of the organic phase film formation of the solid electrolyte interface membrane will no longer be significantly increased. Therefore, in order to take into account the film formation quality and time cost of the solid electrolyte interface membrane, the second preset time length can be set to 30 minutes.

[0118] 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 make more accurate regulation of the film 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.

[0119] In some embodiments, after step S20, the battery may be left to stand for a second time to help the chemical reaction inside the battery reach equilibrium and promote uniform formation of the solid electrolyte interface film, wherein the second time may be 30 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds.

[0120] In some embodiments, after step S40, the battery may be left to stand for a third time to help the chemical reaction inside the battery reach equilibrium and promote uniform film formation of the solid electrolyte interface film. The third time may be greater than or equal to 10 seconds and less than or equal to 80 seconds. For example, the third time may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds.

[0121] According to some embodiments of the present application, continuing to charge the battery until the voltage of the battery reaches the first target film-forming voltage includes: Step S301: the battery is charged at a first sub-charging rate with a constant current until the voltage of the battery reaches a first target film-forming voltage, wherein the first sub-charging rate is less than 0.1C.

[0122] According to some embodiments of the present application, charging the battery until the voltage of the battery reaches the second target film-forming voltage includes: Step S101: the battery is charged at a second sub-charge rate with a constant current until the voltage of the battery reaches a second target film-forming voltage, wherein the second sub-charge rate is less than 0.1C.

[0123] In some embodiments, the first sub-charge rate may be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, or 0.09C. The second sub-charge rate may be 0.01C, 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, or 0.09C.

[0124] The smaller the first sub-charge rate, the longer the time available for the organic phase film-forming reaction of the solid electrolyte interface film to occur in the battery, and the more conducive it is to generate a solid electrolyte interface film of better quality. However, the smaller the first sub-charge rate, the slower the battery charging speed, resulting in an increase in the time cost of battery formation. Therefore, in order to take into account both the time cost and the quality of the generated solid electrolyte interface film, the first sub-charge rate can be set to 0.05C.

[0125] The smaller the second sub-charge rate, the longer the inorganic phase film-forming reaction of the solid electrolyte interface film can take place in the battery, and the more conducive it is to generate a solid electrolyte interface film of better quality. However, the smaller the second sub-charge rate, the slower the battery charging speed, resulting in an increase in the time cost of battery formation. Therefore, in order to take into account both the time cost and the quality of the solid electrolyte interface film formed, the second sub-charge rate can be set to 0.05C.

[0126] It should be noted that the battery formation method may simultaneously include the step of using a second sub-charging rate less than 0.1C to charge the battery at a constant current until the battery voltage reaches a second target film-forming voltage, and the step of using a first sub-charging rate less than 0.1C to charge the battery at a constant current until the battery voltage reaches a first target film-forming voltage.

[0127] By using a second sub-charge rate of less than 0.1C to charge the battery at a constant current 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 the polarization of the battery. By using a first sub-charge rate of less than 0.1C to charge the battery at a constant current 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 the polarization of the battery. By making both the first sub-charge rate and the second sub-charge rate less than 0.1C, it is beneficial to further extend the film-forming time of the solid electrolyte interface film and further reduce the polarization of the battery.

[0128] According to some embodiments of the present application, the first sub-charging rate and the second sub-charging rate are equal.

[0129] 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.

[0130] It should be noted that the first sub-charging rate and the second sub-charging rate may also be set differently according to different actual needs. For example, the first sub-charging rate may be set to one of 0.03C and 0.05C, and the second sub-charging rate may be set to the other of 0.03C and 0.05C.

[0131] By making the first sub-charge rate and the second sub-charge rate equal, it is beneficial to improve the film-forming quality of the solid electrolyte interface film while reducing the complexity of the battery formation method.

[0132] Please continue reading Fig.10 , Fig.10 Schematic diagram of differential capacitance-voltage variation curves according to some embodiments of the present application.

[0133] According to some embodiments of the present application, the second target film forming voltage is determined according to the following method: Obtaining a differential capacitance-voltage change curve representing a change in a differential capacitance value of the battery as a function of a voltage of the battery when the battery is charged for the first time; The battery voltage corresponding to the inorganic phase film-forming reaction characterizing the solid electrolyte interface film in the differential capacitance-voltage change curve is determined as the second target film-forming voltage.

[0134] The differential capacitance value is a measure of the charge change caused by a small change in voltage. The differential capacitance value can be used to describe the nonlinear relationship between the charge storage behavior at the interface between the electrode and the electrolyte. The differential capacitance value can also reflect the kinetics of the ion embedding reaction in the electrode material.

[0135] The differential capacitance-voltage change curve is a curve that reflects the electrochemical reaction and phase change process occurring in the electrode material, and can characterize the characteristics of the solid electrolyte interface film. When the battery is charging, an oxidation-reduction reaction occurs at the interface between the electrolyte and the electrode to generate an inorganic phase product of the solid electrolyte interface film. The portion of the differential capacitance-voltage change curve that corresponds to the oxidation-reduction reaction can characterize the inorganic phase film-forming reaction of the solid electrolyte interface film. Therefore, the second target film-forming voltage can be determined based on the differential capacitance-voltage change curve.

[0136] The second target film-forming voltage is determined by using a differential capacitance-voltage change curve that can characterize the inorganic phase film-forming reaction of the solid electrolyte interface film.

[0137] According to some embodiments of the present 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: Determine a first voltage corresponding to the peak value of the first peak in the differential capacitance-voltage variation curve; The first voltage is determined as the second target film formation voltage.

[0138] The peak value refers to the maximum value of the wave crest. The first voltage corresponding to the peak value is Fig.10 As shown by X1 in . When the solid electrolyte interface film is formed, changes in the interface structure (such as ion transmission path, surface roughness) will significantly affect the capacitance characteristics. For example, side reactions (such as solvent decomposition) during the film formation process may cause transient capacitance peaks. The reduction peak shown in the differential capacitance-voltage change curve can correspond to the inorganic phase film formation reaction of the solid electrolyte interface film.

[0139] Among them, when the battery is charged, the solvent or additive of the electrolyte may undergo an oxidation-reduction reaction on the electrode surface, and the solvent or additive is reduced to generate an inorganic component of the solid electrolyte interface film. When the solvent or additive is reduced, a corresponding reduction peak will appear in the differential capacitance-voltage curve.

[0140] The electrolyte may include a solvent and an additive. When the electrolyte includes an additive, the additive undergoes a redox reaction before the solvent during battery charging to generate an inorganic component of the solid electrolyte interface film to regulate the film-forming components of the solid electrolyte interface film. The additive may be at least one of vinylene carbonate, propane sultone, fluoroethylene carbonate, vinyl sulfate, bis(fluorosulfonyl)imide lithium salt, lithium difluorophosphate, triethyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, and the like.

[0141] Although the formation of the solid electrolyte interface film is affected by the electrolyte, it is understandable that for a specific electrolyte formulation and design, the second target film-forming voltage corresponding to the charging stage is a stable value. Therefore, the first voltage in the historical data can be statistically analyzed to obtain the second target film-forming voltage.

[0142] In some embodiments, the first voltage may be extracted from the differential capacitance-voltage change curve by a computer or other device, and the first voltage may be determined as the second target film-forming voltage.

[0143] Considering the influence of factors such as actual test methods and test environment, the first voltage measured multiple times may not be exactly the same. Therefore, in order to unify the first voltage measured multiple times, a target interval can be determined, and the second target film forming voltage can be equal to a value in the target interval. For example, the target interval can correspond to [Vs-V1, Vs+V2]; where Vs represents the first voltage, and V1 and V2 represent the voltage margin that can be changed relative to the first voltage.

[0144] In some embodiments, the first voltage Vs included in the target interval may be one of the first voltages measured multiple times, and V1 may be 0.5, 1, 1.5, or 2. V2 may be 0.5, 1, 1.5, or 2.

[0145] In some embodiments, the target interval may be a set of first voltages measured multiple times, such as the target interval may correspond to [VA, VB], and the smallest first voltage measured multiple times may be selected as VA, and the largest first voltage measured multiple times may be selected as VB.

[0146] 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 subsequently prolonging the inorganic phase film-forming reaction time of the solid electrolyte interface film in the battery.

[0147] According to some embodiments of the present application, the differential capacitance-voltage change curve is determined according to the following method: Collect the charging capacity and battery voltage at multiple sampling time nodes when the sample battery is charged for the first time; wherein the sample battery and the battery are the same battery; Calculate the differential capacitance value based on the collected charging capacity and battery voltage, where the differential capacitance value is determined based on the ratio of the difference between the charging capacity obtained at two adjacent sampling time nodes to the difference between the battery voltages; The differential capacitance-voltage variation curve is determined according to the differential capacitance value and the battery voltage.

[0148] The sample battery and the battery are the same battery means that the sample battery is the same battery to be formed as the battery to be formed, and the materials, specifications, preparation process 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 of the same batch produced by the same production line.

[0149] When charging the sample battery for the first time, it can be charged at a constant current at a test charge rate until the voltage of the sample battery reaches the upper limit of the charge voltage. The upper limit of the charge voltage refers to the highest voltage value reached by the battery voltage during the charging process. Exceeding this value may cause the battery to be overcharged, thereby damaging the performance and life of the battery. For lithium-ion batteries, this upper limit of the charge voltage is usually around 4.2 volts, but may vary depending on the type and design of the battery. During the charging process, the battery voltage will gradually increase as the charging progresses. When the battery voltage reaches the set upper limit of the charge voltage, the charger will switch from the constant current charging mode to the constant voltage charging mode, that is, the voltage remains constant, and the current decreases as the battery is gradually filled until the charging is completed. Among them, the test charge rate can be less than 0.1C.

[0150] The sampling time node refers to the time point at which the battery is sampled. A first preset time length may be spaced between two adjacent sampling time nodes. In some embodiments, the first preset time length may be 1 second, 5 seconds, or 10 seconds.

[0151] In order to make the obtained differential capacitance-voltage change curve result more accurately characterize the characteristics of the solid electrolyte interface film, the first preset time length is set to 1 second.

[0152] The differential capacitance value is determined based on the ratio of the difference between the charging capacity obtained at two adjacent sampling time nodes 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, Q t+1 and Q t Represents the charging capacity obtained at two adjacent sampling time nodes, V t+1 and V t Indicates the charging voltage obtained at two adjacent sampling time nodes. The sampling time node can start from 0 seconds.

[0153] After the differential capacitance value is calculated, the charging voltage can be used as the horizontal axis, and the unit of the horizontal axis is volts (i.e. Fig.10 The voltage / V in the vertical axis is the differential capacitance value (i.e. Fig.10 ), and obtain the differential capacitance-voltage change curve.

[0154] In some embodiments, after obtaining the differential capacitance value based on the ratio of the difference between the charging capacities obtained at two adjacent sampling time nodes to the difference between the battery voltages, a Gaussian filter, a Kalman filter or other filtering method may be used to perform noise reduction processing on multiple differential capacitance values, and a differential capacitance-voltage change curve may be obtained using the multiple differential capacitance values ​​after noise reduction. By performing noise reduction processing on the differential capacitance value, the oscillation amplitude appearing at the corresponding reduction peak of the differential capacitance-voltage curve may be reduced, so that the first voltage may be determined conveniently and quickly.

[0155] It can be understood that the differential capacitance value can be calculated using a computer or other equipment, and a differential capacitance-voltage change curve can be plotted.

[0156] By using the charging capacitance and battery voltage corresponding to multiple sampling time nodes when the sample battery is charged for the first time, a differential capacitance value is obtained, and then a differential capacitance-voltage change curve for determining the first voltage is obtained, so as to obtain a more accurate second target film forming voltage.

[0157] According to some embodiments of the present application, the second target film forming voltage is greater than or equal to 2V and less than or equal to 2.8V.

[0158] In some embodiments, the second target film forming voltage may be equal to 2V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.6V, 2.7V, or 2.8V.

[0159] In some embodiments, the second target film-forming voltage can also be determined based on the state of charge (SOC) of the battery. The state of charge is the ratio of the remaining capacity of the battery to the capacity of the fully charged state. For example, if the battery is a lithium-ion battery and the electrode is a graphite negative electrode, the state of charge range of the battery corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface membrane is mainly concentrated below 1%, and the battery voltage is mostly 2V~2.8V at this time. Therefore, the battery voltage corresponding to the state of charge below 1% can be selected as the second target film-forming voltage.

[0160] The second target film-forming voltage is directly related to the material system of the battery, that is, it can be determined according to the material type of the battery. It should be noted that the second target film-forming voltage may vary depending on the additives included in the electrolyte. However, when the electrolyte adopts a fixed formula and design, the second target film-forming voltage is a fixed point value.

[0161] By setting the second target film-forming voltage to be greater than or equal to 2V and less than or equal to 2.8V, so as to cover the voltage corresponding to the inorganic phase film-forming reaction characterizing 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 the subsequent steps, thereby improving the film-forming quality of the inorganic phase of the solid electrolyte interface film.

[0162] Please continue reading Figure 7 According to some embodiments of the present application, the battery formation method further includes: Obtaining a differential voltage-voltage change curve representing a differential voltage value of the battery as the voltage of the battery changes when the battery is charged for the first time; Determine the differential voltage-voltage curve with the negative electrode of the battery entering the LiC 24 A second voltage corresponding to the phase; The second voltage is determined as the first target film formation voltage.

[0163] Take the battery as a lithium-ion battery and the electrode as a graphite negative electrode as an example. When the battery is charged, lithium ions are embedded in the graphite. During the process of lithium ions being embedded in the graphite, the graphite negative electrode undergoes a phase change. During the phase change, there are quaternary compounds (such as LiC 36 ), second-order compounds, and finally first-order compounds (LiC 6 ). When graphite changes from pure carbon to LiC 24 Before the LiC phase, the organic phase film formation reaction dominates. 24 After the phase, it is difficult for lithium ions to continue to embed into the graphite electrode, thus weakening the influence on the composition of the organic phase of the solid electrolyte interface film. 24 The voltage corresponding to the phase is determined as the first target film forming voltage.

[0164] The differential voltage-voltage change curve can reflect the start and end of the phase change. Figure 7 The first peak from left to right corresponds to LiC where graphite begins to intercalate lithium. 24 Phase transition peak. Figure 7 The trough corresponding to the middle dotted line is when the negative electrode of the battery enters the LiC 24 At the beginning of the phase, the second voltage is Figure 7 As shown in X2.

[0165] According to some embodiments of the present application, the first trough in the differential voltage-capacitance curve corresponds to the negative electrode of the battery entering the LiC 24 Therefore, in order to quickly determine the first target film forming voltage, the battery formation method also includes: Obtaining a differential voltage-voltage change curve representing a differential voltage value of the battery as the voltage of the battery changes when the battery is charged for the first time; Determine the voltage corresponding to the first trough in the differential voltage-voltage variation curve as the third voltage; The third voltage is determined as the first target film formation voltage.

[0166] By determining the voltage corresponding to the first trough in the differential voltage-voltage variation curve as the first target film-forming voltage, the first target film-forming voltage can be quickly determined according to the differential voltage-voltage variation curve.

[0167] In some embodiments, the negative electrode of the battery may also be selected to enter the LiC 24 The voltage before the phase is taken as the first target film formation voltage. 24 The voltage before the phase and the second voltage are used as a selection interval, and the first target film forming voltage can be equal to a value in the selection interval.

[0168] In some embodiments, the voltage before the third voltage corresponding to the first trough in the differential voltage-voltage change curve can also be used as the first target film-forming voltage. That is, the voltage before the third voltage corresponding to the first trough in the differential voltage-voltage change curve and the third voltage can be used as a selection interval, and the first target film-forming voltage can be equal to a value in the selection interval.

[0169] In some embodiments, the peak value of the second peak in the differential capacitance-voltage change curve and the voltage corresponding thereto are determined as the first target film forming voltage. 12 phase, at which time graphite is embedded with lithium to form LiC 12The phase is dominant, so 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-forming voltage, which actually cannot improve the film-forming effect of the organic phase of the solid electrolyte interface film. 24 Before entering LiC 24 The voltage at the phase is used as the first target film-forming voltage, which 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.

[0170] The second voltage in the differential voltage-voltage change curve that can characterize the organic phase film-forming reaction of the solid electrolyte interface film is determined as the first target film-forming voltage, so that the film-forming quality of the solid electrolyte interface film can be improved by subsequently prolonging the organic phase film-forming reaction time of the solid electrolyte interface film in the battery.

[0171] According to some embodiments of the present application, the differential voltage-voltage change curve is determined according to the following method: Collect the charging capacity and battery voltage at multiple sampling time nodes when the sample battery is charged for the first time; wherein the sample battery and the battery are the same battery; Calculate a differential voltage value based on the collected charging capacity and battery voltage; wherein the differential voltage value is determined based on the ratio of the difference between the battery voltages obtained at two adjacent sampling time nodes to the difference between the charging capacities; According to the differential voltage value and the battery voltage, the differential voltage-voltage change curve is determined.

[0172] The battery that is the same as the sample battery mentioned above means that the sample battery is the same battery that needs to be formed as the battery to be formed, and the materials, specifications, preparation process and conditions of the components in the sample battery can be the same as those of the battery to be formed, for example, they can be products of the same batch produced by the same production line. When the sample battery is charged for the first time, it can be charged at a constant current at a test charging rate until the voltage of the sample battery reaches the upper limit voltage of charging.

[0173] The aforementioned sampling time node refers to the time point at which the battery is sampled. A second preset time length may be spaced between two adjacent sampling time nodes. In some embodiments, the second preset time length may be 1 second, 5 seconds, or 10 seconds.

[0174] In order to make the obtained differential voltage-voltage change curve result more accurately characterize the phase change process of the electrode material, the second preset time length is set to 1 second.

[0175] The differential voltage value is determined based on the ratio of the difference between the battery voltages obtained at two adjacent sampling time nodes 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, Q t+1 and Q t Represents the charging capacity obtained at two adjacent sampling time nodes, V t+1 and V t Indicates the charging voltage obtained at two adjacent sampling time nodes. The sampling time node can start from 0 seconds.

[0176] After the differential voltage value is calculated, the charging voltage can be used as the horizontal axis, and the unit of the horizontal axis is volt (i.e. Figure 7 The voltage in / V), the differential voltage value is the vertical axis (i.e. Figure 7 ), and obtain the differential voltage-voltage change curve.

[0177] In some embodiments, after calculating the differential voltage value, a plurality of differential voltage values ​​may be subjected to noise reduction processing by using a filtering method such as a Gaussian filter or a Kalman filter, and a differential voltage-voltage change curve may be obtained by using the plurality of differential voltage values ​​after noise reduction processing. By subjecting the differential voltage value to noise reduction processing, the second voltage may be determined conveniently and quickly.

[0178] It can be understood that the differential voltage value can be calculated using a computer or other equipment, and a differential voltage-voltage change curve can be drawn.

[0179] By using the charging capacitance and battery voltage corresponding to multiple sampling time nodes when the sample battery is charged for the first time, a differential voltage value is obtained, and then a differential voltage-voltage change curve for determining the second voltage is obtained, so as to obtain a more accurate first target film forming voltage.

[0180] According to some embodiments of the present application, the first target film forming voltage is greater than or equal to 3V and less than or equal to 3.3V.

[0181] In some embodiments, the first target film forming voltage may be equal to 3V, 3.1V, 3.2V, or 3.3V.

[0182] In some embodiments, the first target film-forming voltage can also be determined based on the state of charge of the battery. For example, when the battery is a lithium-ion battery and the electrode is a graphite negative electrode, the state of charge range of the battery corresponding to the organic phase film-forming reaction of the solid electrolyte interface film is mainly concentrated in 1%~8%. At this time, the battery voltage is mostly 3V~3.3V. Therefore, the battery voltage corresponding to the state of charge of 1%~8% can be selected as the first target film-forming voltage.

[0183] The first target film-forming voltage is directly related to the material system of the battery, that is, it can be determined according to the material type of the battery. It should be noted that when the battery adopts a fixed formula and design, the first target film-forming voltage is a fixed point value.

[0184] By setting the first target film-forming voltage to be greater than or equal to 3V and less than or equal to 3.3V, so as to cover the voltage corresponding to the organic phase film-forming reaction characterizing the solid electrolyte interface film, it is convenient to extend the film-forming reaction time of the organic phase of the solid electrolyte interface film in the battery in the subsequent steps, thereby improving the organic phase film-forming quality of the solid electrolyte interface film.

[0185] Please continue reading Figure 4 According to some embodiments of the present application, after the battery is charged at a constant voltage at a target film-forming voltage for a preset time, the method further includes: Step S3: continue to perform constant current charging on the battery at the second charging rate until the battery's state of charge reaches a film-forming reaction cutoff state of charge.

[0186] Wherein, in the film-forming reaction cut-off charge state, 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.

[0187] That is, when the target film forming voltage is the first target film forming voltage, please continue to refer to Figure 5 , after the battery is charged at a constant voltage at the first target film forming voltage, the method further includes: Step S3: continue to perform constant current charging on the battery at the second charging rate until the battery's state of charge reaches a film-forming reaction cutoff state of charge.

[0188] When the target film forming voltage is the second target film forming voltage, please continue to refer to Figure 6 After the battery is charged at a constant voltage at the second target film-forming voltage, the method further includes: Step S3: continue to perform constant current charging on the battery at the second charging rate until the battery's state of charge reaches a film-forming reaction cutoff state of charge.

[0189] The film-forming reaction cut-off state of charge refers to the state of charge when the battery is charged to a specific state of charge during the formation process of the lithium-ion battery, at which time the solid electrolyte interface film inside the battery is basically formed. This state of charge is part of the formation process in the battery manufacturing process. The battery is charged to the film-forming reaction cut-off state of charge, which means that the battery has basically formed a solid electrolyte interface film in this charging stage, and the gas production of the film-forming side reaction is also gradually approaching 0. In some examples, the film-forming reaction cut-off state of charge can be determined by detecting the change in the gas production of the battery in the formation stage. For example, the state of charge corresponding to the gas production rate or gas production flow rate inside the battery in the formation stage is reduced to a preset gas production threshold value when the gas production rate or gas production flow rate is reduced to a preset gas production threshold value. It is determined as the aforementioned film-forming reaction cut-off state of charge, or a state of charge margin can be added to the state of charge corresponding to the state of charge when the gas production rate or gas production flow rate is reduced to a preset gas production threshold value to determine the film-forming reaction cut-off state of charge, such as increasing the SOC by 5%.

[0190] Before the battery is charged to the film-forming reaction cut-off charge state, sufficient time is required for the film-forming reaction to occur inside the battery. Therefore, a smaller first charge rate is usually used for the charge. After the film-forming reaction cut-off charge state is reached, the film-forming reaction is basically completed, so a larger second charge rate can be used for charging to shorten the time spent in the formation stage.

[0191] The duration of the battery continuing to be charged with constant current at the second charging rate may be equal to a third preset duration. The third preset duration may be greater than the first preset duration or the second preset duration. For example, the third preset duration is 40 minutes, 60 minutes, or 80 minutes.

[0192] In step S3, the graphite negative electrode begins to embed lithium ions, accompanied by the further growth of the solid electrolyte interface film organic phase.

[0193] In some embodiments, the second charge rate may take different values ​​at different stages to improve the film quality of the solid electrolyte interface film while saving the formation time. Figure 6 Taking the battery formation method shown in the figure as an example, in step S3, when the battery corresponds to a first state of charge interval, the second charging rate is set to a first value. When the battery corresponds to a second state of charge interval, the second charging rate is set to a second value. Among them, the state of charge included in the first state of charge interval is less than the state of charge included in the second state of charge interval, and the first value is less than the second value. For example, the state of charge included in the first state of charge interval can be less than 8%, and the state of charge included in the first state of charge interval can be 8%~film formation reaction cut-off state of charge. The first value can be 0.05C; the second value can be 0.1C.

[0194] In some embodiments, after step S3, the process may further include: leaving the battery to stand for a certain period of time (eg, 10 seconds to 60 seconds) to help the chemical reaction inside the battery reach equilibrium and promote uniform formation of the solid electrolyte interface film.

[0195] The organic phase of the solid electrolyte interface film further grows while the battery is continuously charged at a second charging rate until the state of charge of the battery reaches the cut-off state of charge for the film-forming reaction. The second charging rate is greater than or equal to the first charging rate to assist the solid electrolyte interface film in further growth while shortening the formation time.

[0196] Please continue reading Figure 8 According to some embodiments of the present application, after the battery is charged at a constant voltage with the first target film-forming voltage, the method further includes: Step S50: continue to perform constant current charging on the battery at the second charging rate until the state of charge of the battery reaches a film-forming reaction cut-off state of charge.

[0197] Among them, in the film formation reaction cut-off charge state, the film formation 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.

[0198] As mentioned above, charging the battery to the film-forming reaction cut-off charge state means that the battery has basically formed a solid electrolyte interface film at this charging stage.

[0199] In some embodiments, after step S50, the method may further include: leaving the battery to stand for a fourth time period. The fourth time period may be greater than or equal to 10 seconds and less than or equal to 80 seconds. For example, the fourth time period may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds.

[0200] The organic phase of the solid electrolyte interface film further grows while the battery is continuously charged at a second charging rate until the state of charge of the battery reaches the cut-off state of charge for the film-forming reaction. 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 interface film to further grow while shortening the formation time.

[0201] According to some embodiments of the present application, the second charging rate is greater than or equal to 0.1C and less than or equal to 0.3C.

[0202] In some embodiments, the second charge rate is equal to 0.1C, 0.2C or 0.3C. Since the smaller the charge rate, the better the quality of the solid electrolyte interface film, the second charge rate can be further set to 0.1C.

[0203] By making the second charging rate greater than or equal to 0.1C and less than or equal to 0.3C, the solid electrolyte interface film can be assisted to further grow and the film formation quality of the solid electrolyte interface film can be improved.

[0204] According to some embodiments of the present application, the film-forming reaction cutoff state of charge is greater than or equal to 15% and less than or equal to 35%.

[0205] Since batteries of different materials or components have different film-forming reaction cut-off charge states, the specific film-forming reaction cut-off charge state can be selected based on the empirical value of batteries of the same material and specification type, or can be obtained through detection, for example, by detecting the gas production rate or gas production flow rate in the formation stage.

[0206] Taking graphite negative electrode as an example, the state of charge range of the battery corresponding to the formation of graphite solid electrolyte film is mainly concentrated below 15%. Therefore, in some embodiments, the cut-off state of charge of the film formation reaction can be set to be greater than or equal to 15% and less than or equal to 35%.

[0207] In some embodiments, after the battery is charged at a constant voltage at the first target film-forming voltage for a preset period of time, the state of charge of the battery corresponds to about 10%. The state of charge at the end of the film-forming reaction may be equal to 15%, 20%, 25%, 30% or 35%.

[0208] By setting the cut-off state of charge of the film-forming 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 actual application conditions and the application rate of the battery formation method can be improved.

[0209] Please continue reading Figure 4~Figure 6 and Figure 8 According to some embodiments of the present application, the battery is continuously charged at a second charging rate with a constant current until the state of charge of the battery reaches a film-forming reaction cut-off state of charge, further comprising: Step S4: continue to perform constant current charging on the battery at a third charging rate until the state of charge of the battery reaches a preset state of charge for aging, wherein the third charging rate is greater than the second charging rate.

[0210] The default state of charge is the initial state of charge that the battery has when it is aged. The battery will be aged after it is formed.

[0211] In some embodiments, the third charging rate is greater than 0.3C, such as the third charging rate is equal to 0.33C or 0.5C.

[0212] In some embodiments, after step S4, the battery may be left to stand for a fifth time to help the chemical reaction inside the battery reach equilibrium and promote uniform film formation of the solid electrolyte interface film. The fifth time may be greater than or equal to 10 seconds and less than or equal to 80 seconds. For example, the fifth time may be 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds or 80 seconds.

[0213] The battery is continuously charged at a third charging rate with a constant current until the state of charge of the battery reaches a preset state of charge for aging, so as to prepare for the subsequent aging process. The third charging rate is greater than the second charging rate, which can save formation time.

[0214] According to some embodiments of the present application, the preset state of charge is greater than or equal to 40% and less than or equal to 90%.

[0215] In some embodiments, the preset state of charge may be equal to 40%, 50%, 55%, 60%, 70%, 75%, 80%, or 90%.

[0216] Prepare for the aging process by setting the preset state of charge to greater than or equal to 40% and less than or equal to 90%.

[0217] It should be noted that the battery formation method provided in the present application can adopt a negative pressure formation process so that the gas generated during the formation can be discharged in time to improve the stability and consistency of the solid electrolyte interface film. For example, the battery cell injection port can be connected to a negative pressure machine to adjust the pressure value inside the battery cell to -80±5 kPa for formation.

[0218] The battery formation method provided in the present application can adopt a high temperature formation process to improve the consistency of the solid electrolyte interface film. For example, the temperature used during the formation can be 40 degrees Celsius to 60 degrees Celsius. In some embodiments, the temperature used during the formation is 45 degrees Celsius.

[0219] In some embodiments, the battery formation method provided in the present application may also adopt an open-mouth formation process or a closed-mouth formation process, and the battery formation method provided in the present application may also adopt a low-temperature formation process.

[0220] After the battery continues to be charged at a third charging rate with a constant current until the battery's state of charge reaches a preset state of charge for aging, the battery can be subjected to processes such as secondary liquid filling, welding of sealing nails, and high-temperature aging.

[0221] An embodiment of the present application provides a battery formation device, which is configured to execute any of the above-mentioned battery formation methods.

[0222] The battery formation device is used to perform formation treatment on the battery.

[0223] It can be understood that the battery formation device provided in the present application applies any of the above-mentioned battery formation methods, and therefore, the battery formation device has all the beneficial effects of the above-mentioned battery formation methods, which will not be described in detail here.

[0224] An embodiment of the present application provides a battery production method, which includes any of the above-mentioned battery formation methods.

[0225] The battery production method is used to manufacture batteries. In some embodiments, the battery production method also includes a method for injecting and aging the battery.

[0226] It can be understood that the battery production method provided in the present application applies any of the above-mentioned battery formation methods. Therefore, the battery production method has all the beneficial effects of the above-mentioned battery formation methods, which will not be described in detail here.

[0227] An embodiment of the present application provides a battery production system, which includes any of the above-mentioned battery formation devices.

[0228] The battery production system is used to produce batteries. In some embodiments, the battery production system also includes a device that can shell, weld, package, and age the batteries.

[0229] It can be understood that the battery production system provided in the present application uses any of the above-mentioned battery formation devices, and therefore, the battery production method has all the beneficial effects of the above-mentioned battery formation devices, which will not be described in detail here.

[0230] An embodiment of the present application provides a battery, which is manufactured using any of the above-mentioned battery production methods.

[0231] The battery may be a lithium sulfur battery, a sodium ion battery or a magnesium ion battery, but is not limited thereto. The battery may be a secondary battery or a primary battery.

[0232] It can be understood that the battery provided in the present application is manufactured by applying any of the above-mentioned battery production methods. Therefore, the battery has all the beneficial effects of the above-mentioned battery production methods, which will not be described in detail here.

[0233] An embodiment of the present application provides an electrical device, which includes any of the above-mentioned batteries, and the battery is used to provide electrical energy.

[0234] Electrical devices may include mobile phones, tablets, laptops, electric toys, electric tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0235] It can be understood that the electrical device provided in the present application uses any of the above-mentioned batteries, and therefore, the electrical device has all the beneficial effects of the above-mentioned batteries, which will not be described in detail here.

[0236] An embodiment of the present application provides an energy storage device, which includes any of the above-mentioned batteries, and the battery is used to store electrical energy.

[0237] Energy storage devices may include, but are not limited to, centralized energy storage devices (such as container energy storage devices), distributed energy storage devices, mobile energy storage devices, wearable energy storage devices, and the like.

[0238] It can be understood that the energy storage device provided in the present application uses any of the above-mentioned batteries, and therefore, the energy storage device has all the beneficial effects of the above-mentioned batteries, which will not be described in detail here.

[0239] The battery formation method of the present application is described below in conjunction with a specific embodiment. Fig.11 As shown, Fig.11 The present invention is a flowchart of another battery formation method according to some embodiments of the present application.

[0240] Battery formation methods include: Step SR1: leaving the battery to rest for a first time period, wherein the first time period is 60 seconds.

[0241] Step S101: the battery is charged at a constant current at a second sub-charge rate until the voltage of the battery reaches a second target film-forming voltage, wherein the second sub-charge rate is 0.05C.

[0242] Step S20: The battery is charged at a first constant voltage at the second target film-forming voltage for a first preset time period, wherein the first preset time period is 30 minutes.

[0243] Step SR2: leaving the battery to rest for a second time period, wherein the second time period is 60 seconds.

[0244] Step S301: the battery is charged at a first sub-charging rate with a constant current until the voltage of the battery reaches a first target film-forming voltage, wherein the first sub-charging rate is 0.05C.

[0245] Step S40: performing a second constant voltage charging on the battery at the first target film forming voltage and continuing for a second preset time, wherein the second preset time is 30 minutes.

[0246] Step SR3: leaving the battery to stand for a third time period, wherein the third time period is 10 seconds to 60 seconds.

[0247] Step S50: Continue to charge the battery at a second charging rate with a constant current until the battery's state of charge reaches a film-forming reaction cutoff state of charge. The second charging rate is 0.1 C. The third preset time for continuing to charge the battery at a second charging rate with a constant current can be set to 60 minutes.

[0248] Step SR4: leaving the battery to stand for a fourth time period, wherein the fourth time period is 10 seconds to 60 seconds.

[0249] Step S4: Continue to perform constant current charging on the battery at the third charging rate until the state of charge of the battery reaches a preset state of charge for aging. The third charging rate is 0.33C. The duration of continuing to perform constant current charging on the battery at the third charging rate can be set to 100 minutes.

[0250] Step SR5: leaving the battery to stand for a fifth time period, wherein the fifth time period is 10 seconds to 60 seconds.

[0251] After step SR5, the battery can be subjected to secondary liquid injection, welding of sealing nails, high-temperature aging and other processes.

[0252] Fig.12 This is a comparative test result diagram of some embodiments of the present application. Taking lithium-ion batteries as an example, different battery formation methods are used to form the same battery for comparative verification. The same battery means that the materials, specifications, preparation processes and conditions of each component in the battery are the same. For example, the batteries used in each solution (i.e., battery 1 to battery 4 described below) can be products of the same batch produced by the same production line.

[0253] In order to reflect the uniformity of the effect of the battery formation method, multiple batteries can be used in each scheme for experimental verification to form a parallel scheme under the corresponding scheme. The batteries used in the parallel schemes are also the same batteries, and the battery formation methods and cycle testing methods used in the parallel schemes are the same. Taking Scheme 1 as an example, Scheme 1 includes two parallel schemes. The batteries used in the two parallel schemes are products of the same batch produced by the same production line, and the battery formation methods and cycle testing methods used in the two parallel schemes are the same.

[0254] The battery formation method used by the battery 1 in any parallel scheme in scheme 1 is as follows Fig.11 shown.

[0255] The battery formation method used by the battery 2 applied in any parallel scheme in scheme 2 includes: Step SR1: The battery 2 is left to stand for a first time period, wherein the first time period is 60 seconds.

[0256] Step S11: the battery 2 is charged at a first charging rate with a constant current until the voltage of the battery 2 reaches the second target film-forming voltage. The first charging rate is 0.05C.

[0257] Step S22: the battery 2 is charged at a constant voltage at the second target film-forming voltage for a preset time period, wherein the preset time period is 30 minutes.

[0258] Step SR2: leaving the battery 2 to stand for a second time period, wherein the second time period is 60 seconds.

[0259] Step S3: Battery 2 is charged at a constant current at a second charging rate until the state of charge of battery 2 reaches a film-forming reaction cutoff state of charge. The second charging rate may be 0.05C to 0.1C. In this step, battery 2 may be charged at 0.05C first and then at 0.1C.

[0260] Step SR4: leaving the battery 2 to stand for a fourth time period, wherein the fourth time period is 10 seconds to 60 seconds.

[0261] Step S4: Battery 2 is continuously charged at a third charging rate until the state of charge of battery 2 reaches a preset state of charge for aging. The third charging rate is 0.33C. The duration of the constant current charging of battery 2 at the third charging rate can be set to 100 minutes.

[0262] Step SR5: leaving the battery 2 to stand for a fifth time period, wherein the fifth time period is 10 seconds to 60 seconds.

[0263] The battery formation method used by the battery 3 applied in any parallel scheme in scheme 3 includes: Step SR1: The battery 3 is left to stand for a first time period, wherein the first time period is 60 seconds.

[0264] Step S111: the battery 3 is charged at a first charging rate with a constant current until the voltage of the battery 3 reaches a first target film-forming voltage. The first charging rate is 0.05C.

[0265] Step S222: performing a second constant voltage charging on the battery 3 at the first target film forming voltage and continuing for a second preset time, wherein the second preset time is 30 minutes.

[0266] Step SR3: leaving the battery 3 at rest for a third time period, wherein the third time period is 10 seconds to 60 seconds.

[0267] Step S3: Continue to perform constant current charging on the battery 3 at the second charging rate until the charge state of the battery 3 reaches the film forming reaction cut-off charge state. The second charging rate is 0.1 C. The third preset time for continuing to perform constant current charging on the battery 3 at the second charging rate can be set to 60 minutes.

[0268] Step SR4: leaving the battery 3 at rest for a fourth time period, wherein the fourth time period is 10 seconds to 60 seconds.

[0269] Step S4: Continue to perform constant current charging on the battery 3 at the third charging rate until the state of charge of the battery reaches the preset state of charge for aging. The third charging rate is 0.33C. The duration of continuing to perform constant current charging on the battery at the third charging rate can be set to 100 minutes.

[0270] Step SR5: leaving the battery 3 at rest for a fifth time period, wherein the fifth time period is 10 seconds to 60 seconds.

[0271] The battery formation method used by the battery 4 applied in any parallel scheme in scheme 4 is: Step ST1: charging the battery 4 at a constant current with a charging rate of 0.05C until the state of charge of the battery 4 reaches 10%; Step ST2: The battery 4 is left to stand for 60 seconds.

[0272] Step ST3: charging the battery 4 at a constant current with a charging rate of 0.1C until the state of charge of the battery 4 reaches 20%; Step ST4: Let the battery 4 stand for 10 seconds to 60 seconds.

[0273] Step ST5: continue to perform constant current charging on the battery 4 at the third charging rate until the state of charge of the battery reaches a preset state of charge for aging.

[0274] Step ST6: Let the battery 4 stand for 10 seconds to 60 seconds.

[0275] After step SR5 and step ST6, the same processes of secondary liquid injection, welding of sealing nails, high temperature aging, etc. can be performed on battery 1 to battery 4.

[0276] During the experimental verification, the batteries in each parallel scheme of Scheme 1 to Scheme 4 were cycle tested using the following method: Step SA1: Let stand for 10 minutes.

[0277] Step SA2: Perform constant current charging at a charging rate of 1.0C until the battery voltage reaches the upper limit of the charging voltage, and 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 the battery state of charge of 100%.

[0278] Step SA3: Let stand for 10 minutes.

[0279] Step SA4: Perform constant current discharge at a discharge rate of 1.0C until the battery voltage reaches the lower discharge limit voltage.

[0280] Step SA5: performing constant current discharge at a discharge rate of 0.05C until the battery voltage reaches a voltage corresponding to a state of charge of 0%.

[0281] Step SA6: loop steps SA1 to SA5 400 times, and get the test results as follows Fig.12 shown.

[0282] according to Fig.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 a certain extent, thereby increasing the service life of the battery. Scheme 1 can significantly improve the film quality of the solid electrolyte interface film and significantly increase the service life of the battery.

[0283] Therefore, in the battery formation method, the application of the first target film-forming voltage determined by the differential voltage-voltage change curve can improve the organic phase film-forming quality of the solid electrolyte interface film, and then improve the film-forming quality of the solid electrolyte interface film.

[0284] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery formation method, characterized in that: The battery formation method comprises: Charging the battery until the voltage of the battery reaches a first target film-forming voltage; performing constant voltage charging on the battery at the first target film-forming voltage; Among them, 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 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 characterized in the differential voltage-voltage change curve in which the differential voltage value of the battery changes with the voltage of the battery.

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

3. The battery formation method according to claim 1, characterized in that: The charging of the battery until the voltage of the battery reaches the first target film-forming voltage includes: Charging the battery until the voltage of the battery reaches a second target film-forming voltage; performing constant voltage charging on the battery at the second target film-forming voltage; The second target film-forming voltage is a voltage corresponding to an inorganic phase film-forming reaction of a solid electrolyte interface film in the battery.

4. The battery formation method according to claim 3, characterized in that: The step of charging the battery until the voltage of the battery reaches the first target film forming voltage comprises: Performing constant current charging on the battery at a first sub-charging rate until the voltage of the battery reaches the first target film-forming voltage; The step of charging the battery until the voltage of the battery reaches the second target film forming voltage comprises: Performing constant current charging on the battery at a second sub-charging rate until the voltage of the battery reaches the second target film-forming voltage; Wherein, the first sub-charging rate and the second sub-charging rate are both less than 0.1C.

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

6. The battery formation method according to claim 3, characterized in that: The second target film forming voltage is determined according to the following method: Obtaining a differential capacitance-voltage variation curve representing a differential capacitance value of the battery as a function of a voltage of the battery when the battery is charged for the first time; The battery voltage corresponding to the inorganic phase film-forming reaction of the solid electrolyte interface film in the differential capacitance-voltage change curve is determined as the second target film-forming voltage.

7. The battery formation method according to claim 6, characterized in that: The step of 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 comprises: Determining a first voltage corresponding to a peak value of a first peak in the differential capacitance-voltage variation curve; The first voltage is determined as the second target film-forming voltage.

8. The battery formation method according to claim 6, characterized in that: The differential capacitance-voltage variation curve is determined according to the following method: Collecting the charging capacity and battery voltage of a sample battery at multiple sampling time nodes when the sample battery is charged for the first time; wherein the sample battery and the battery are the same battery; Calculating the differential capacitance value according to the collected charging capacity and the battery voltage, wherein the differential capacitance value is determined based on the ratio of the difference between the charging capacity obtained at two adjacent sampling time nodes to the difference between the battery voltages; The differential capacitance-voltage variation curve is determined according to the differential capacitance value and the battery voltage.

9. The battery formation method according to claim 3, characterized in that: The second target film forming voltage is greater than or equal to 2V and less than or equal to 2.8V.

10. The battery formation method according to any one of claims 1 to 9, characterized in that: The method further comprises: Acquire the differential voltage-voltage change curve representing the differential voltage value of the battery as the voltage of the battery changes when the battery is charged for the first time; Determine the differential voltage-voltage change curve and the negative electrode of the battery enters LiC 24 A second voltage corresponding to the phase; The second voltage is determined as the first target film-forming voltage.

11. The battery formation method according to any one of claims 1 to 9, characterized in that: The method further comprises: Acquire the differential voltage-voltage change curve representing the differential voltage value of the battery as the voltage of the battery changes when the battery is charged for the first time; Determine that the voltage corresponding to the first trough in the differential voltage-voltage variation curve is the third voltage; The third voltage is determined as the first target film formation voltage.

12. The battery formation method according to any one of claims 1 to 9, characterized in that: The differential voltage-voltage variation curve is determined according to the following method: Collecting the charging capacity and battery voltage of a sample battery at multiple sampling time nodes when the sample battery is charged for the first time; wherein the sample battery and the battery are the same battery; Calculating the differential voltage value according to the collected charging capacity and the 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 nodes to the difference between the charging capacities; The differential voltage-voltage variation curve is determined according to the differential voltage value and the battery voltage.

13. The battery formation method according to any one of claims 1 to 9, characterized in that: The first target film forming voltage is greater than or equal to 3V and less than or equal to 3.3V.

14. 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: Continue to perform constant current charging on the battery at a second charging rate until the state of charge of the battery reaches a film-forming reaction cutoff state of charge; Wherein, in the film-forming reaction cut-off charge state, 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.

15. The battery formation method according to claim 4, characterized in that: After the battery is charged at a constant voltage using the first target film-forming voltage, the method further includes: Continue to perform constant current charging on the battery at a second charging rate until the state of charge of the battery reaches a film-forming reaction cutoff state of charge; Wherein, in the film-forming reaction cutoff charge state, 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.

16. The battery formation method according to claim 14 or 15, characterized in that: The second charging rate is greater than or equal to 0.1C and less than or equal to 0.3C.

17. The battery formation method according to claim 14 or 15, characterized in that: The film-forming reaction cutoff state of charge is greater than or equal to 15% and less than or equal to 35%.

18. The battery formation method according to claim 14 or 15, characterized in that: The method of continuing to charge the battery at a second charging rate at a constant current until the state of charge of the battery reaches a film-forming reaction cut-off state of charge further includes: Continue to perform constant current charging on the battery at a third charging rate until the state of charge of the battery reaches a preset state of charge for aging; Wherein, the third charging rate is greater than the second charging rate.

19. The battery formation method according to claim 18, characterized in that: The preset state of charge is greater than or equal to 40% and less than or equal to 90%.

20. A battery formation device, characterized in that: The battery formation device is configured to execute the battery formation method according to any one of claims 1 to 19.

21. A battery production method, characterized in that: The method comprises a battery formation method as claimed in any one of claims 1 to 19.

22. A battery production system, characterized in that: Comprising the battery formation device as claimed in claim 20.

23. A battery, characterized in that: The battery is manufactured using the battery production method as claimed in claim 21.

24. An electrical device, characterized in that: Comprising a battery as claimed in claim 23, the battery is used to provide electrical energy.

25. An energy storage device, characterized in that: Comprising a battery as claimed in claim 23, the battery is used to store electrical energy.

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