Battery cell, battery apparatus, and electric device

Abstract

The present application discloses a battery cell, a battery apparatus, and an electric device. The battery cell comprises a negative electrode film layer, the negative electrode film layer comprises a binder, and the binder comprises a lithium-containing high molecular polymer; an electrolyte comprises a lithium salt; and the lithium salt comprises a lithium fluorosulfonimide salt. In the embodiments of the present application, the charging performance of the battery cell can be improved by means of a binder comprising a lithium-containing high molecular polymer; and the high-temperature charging performance of the battery cell can be improved by introducing a lithium fluorosulfonimide salt into the electrolyte. Thus, in battery cells having high energy density, the effects of wide temperature range, long service life, and fast charging can be achieved.

Description

Battery cells, battery devices and electrical equipment

[0001] This disclosure claims priority to Chinese Patent Application No. 2025100585776, filed on January 14, 2025, entitled “Battery Cell, Battery Device and Electrical Equipment”, which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to the field of new energy technology, and in particular to a battery cell, battery device, and electrical equipment. Background Technology

[0003] This section provides only background information relevant to this application and is not necessarily prior art.

[0004] Currently, the rapid development of new energy batteries is driving explosive growth in industries such as electric vehicles. However, the operating range of new energy batteries is typically around room temperature (close to 25°C). Battery-powered vehicles and other products require a wider operating temperature range (-20°C to 60°C) to adapt to regional and seasonal differences. Furthermore, in extreme applications such as aerospace, the lower limit of the operating temperature range for new energy batteries even needs to be extended to -50°C or lower. Therefore, developing wide-temperature-range new energy batteries is of great significance for both the electric vehicle sector and extreme applications such as aerospace.

[0005] Therefore, this invention is proposed. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a battery cell, a battery device and an electrical device, which aims to improve the battery performance of the battery cell in a wide temperature range.

[0007] To achieve the above objectives, the first aspect of this application provides a battery cell, which includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0008] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material and a binder; the binder includes a lithium-containing polymer.

[0009] The electrolyte includes lithium salts; lithium salts include lithium salts containing fluorosulfonylimide.

[0010] The embodiments of this application utilize a binder comprising a lithium-containing polymer to establish highly conductive lithium-ion channels in the solid phase, reducing solid-phase mass transfer impedance and thereby improving the charging performance of individual battery cells. Furthermore, by introducing lithium fluorosulfonylimide salt into the electrolyte, the electrolyte exhibits excellent thermal stability, reducing high-temperature gas generation and side reactions, thus enhancing the high-temperature charging performance of individual battery cells. Therefore, a wide temperature range, long lifespan, and fast charging capabilities can be achieved in high-energy-density battery cells.

[0011] In some embodiments, the chemical formula of the lithium-containing polymer includes [C6H7O2(OH)]. x (OCH2COOLi) y ] n And / or [CH2CH(COOLi)] n , where x+y=3, and the value of n ranges from 200 to 3500.

[0012] The embodiments of this application utilize lithium-containing polymers with the above-described chemical formulas to establish highly conductive lithium-ion channels in the solid phase, reduce solid-phase mass transfer impedance, and thereby improve the charging performance of individual battery cells.

[0013] In some embodiments, the mass percentage of the binder is in the range of 1% to 6% based on the total mass of the negative electrode film.

[0014] The embodiments of this application, through the binder within the above-mentioned mass percentage range, can establish a high solid-phase lithium-ion channel, reduce solid-phase mass transfer impedance, and thereby improve the charging performance of the battery cell.

[0015] In some embodiments, the lithium fluorosulfonylimide salt includes the lithium difluorosulfonylimide salt.

[0016] The embodiments of this application utilize the aforementioned fluorosulfonylimide lithium salt to achieve good thermal stability in the electrolyte, thereby reducing high-temperature gas generation and side reactions, and thus improving the high-temperature charging performance of the battery cells.

[0017] In some embodiments, the negative electrode active material includes artificial graphite; based on the total mass of the negative electrode film, the mass percentage of the negative electrode active material is in the range of 90% to 99%.

[0018] The embodiments of this application improve the cycle life of a single battery cell by using the above-mentioned negative electrode active material and its mass percentage range in the negative electrode film layer.

[0019] In some embodiments, the negative electrode active material also includes amorphous carbon.

[0020] The embodiments of this application improve the charging performance of a single battery cell by introducing amorphous carbon into the negative electrode active material.

[0021] In some embodiments, at least a portion of the surface of the artificial graphite is covered with amorphous carbon.

[0022] The embodiments of this application improve the charging performance of a single battery cell by using artificial graphite with at least a portion of its surface covered with amorphous carbon.

[0023] In some embodiments, the mass percentage of amorphous carbon is in the range of 1% to 5% based on the total mass of the negative electrode film.

[0024] The embodiments of this application improve the charging performance of battery cells by using amorphous carbon within the above-mentioned mass percentage range.

[0025] In some embodiments, the specific capacity of the negative electrode active material is in the range of 330 mAh / g to 360 mAh / g.

[0026] The embodiments of this application improve the energy density of a single battery cell by using negative electrode active materials within the aforementioned specific capacity range.

[0027] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the second negative electrode film layer being disposed between the first negative electrode film layer and the negative electrode current collector; the first negative electrode film layer includes a first negative electrode active material and a first binder, the first binder including a first lithium-containing polymer; the second negative electrode film layer includes a second negative electrode active material and a second binder; the second binder includes a second lithium-containing polymer; based on the total mass of the first negative electrode film layer, the mass percentage of the first binder is in the range of 1% to 5%; based on the total mass of the second negative electrode film layer, the mass percentage of the second binder is in the range of 2% to 6%.

[0028] The embodiments of this application establish a high solid-phase lithium-ion channel by adjusting the mass ratio of the binder in each layer of the negative electrode film, thereby reducing the solid-phase mass transfer impedance and improving the low-temperature charging performance and high-temperature charging performance of the battery cell.

[0029] In some embodiments, the compaction density of the negative electrode sheet is in the range of 1.5 g / cc to 1.7 g / cc.

[0030] The embodiments of this application improve the energy density of a single battery cell by using a negative electrode film layer within the aforementioned compaction density range.

[0031] In some embodiments, the coating weight of the negative electrode film is 140 mg / 1540.25 mm. 2 ~170mg / 1540.25mm 2 Within the range.

[0032] The embodiments of this application improve the energy density of a single battery cell by employing a negative electrode film layer within the aforementioned coating weight range.

[0033] In some embodiments, the mass percentage of fluorosulfonylimide lithium salt is in the range of 1% to 5% based on the total mass of the electrolyte.

[0034] The embodiments of this application improve the high-temperature stability of the electrolyte, reduce high-temperature gas generation and side reactions, improve the film formation stability of the SEI film of the negative electrode layer, and enhance the high-temperature charging performance of the battery cell by introducing fluorinated sulfonamide lithium salts within the above-mentioned mass percentage range into the electrolyte.

[0035] In some embodiments, the lithium salt further includes lithium hexafluorophosphate; the mass percentage of lithium hexafluorophosphate is in the range of 5% to 12% based on the total mass of the electrolyte.

[0036] The embodiments of this application introduce lithium hexafluorophosphate within the above-mentioned mass percentage range into the electrolyte, thereby giving the electrolyte higher solubility, better antioxidant capacity and stronger electrochemical stability, and improving the cycle life of the battery cells.

[0037] In some embodiments, the conductivity of the electrolyte is in the range of 6 mS / m to 10 mS / m.

[0038] The embodiments of this application improve the transport capability of lithium ions in the electrolyte and enhance the charging performance of the battery cell by using an electrolyte within the above-mentioned conductivity range.

[0039] In some embodiments, the viscosity of the electrolyte is in the range of 25 mPa·s to 35 mPa·s.

[0040] The embodiments of this application improve the wetting effect of the positive electrode film and the negative electrode film in the electrolyte by using electrolytes within the above viscosity range, thereby improving the liquid phase transport conditions of lithium ions and providing more active sites in the negative electrode film for lithium ion insertion, thereby improving the charging performance of the battery cell.

[0041] In some embodiments, the electrolyte injection coefficient is in the range of 2.8 g / Ah to 3.4 g / Ah.

[0042] The embodiments of this application improve the uniformity of electrolyte distribution, enhance the film-forming stability of electrolyte on the negative electrode sheet, and improve the cycle life of the battery cell by using electrolytes within the above-mentioned electrolyte injection coefficient range.

[0043] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector; the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes a lithium phosphate with an olivine structure.

[0044] The embodiments of this application employ a positive electrode sheet comprising the above-mentioned positive active material to improve the cycle life of the battery cell.

[0045] In some embodiments, the weight percentage of lithium phosphate with an olivine structure is in the range of 95% to 97% based on the total mass of the positive electrode film.

[0046] The embodiments of this application improve the energy density of a single battery cell by adjusting the mass ratio of lithium phosphate with an olivine structure based on the total mass of the positive electrode film.

[0047] In some embodiments, the specific capacity of the positive electrode active material is in the range of 140 mAh / g to 150 mAh / g.

[0048] The embodiments of this application improve the energy density of a single battery cell by using positive electrode active materials within the above-mentioned specific capacity range.

[0049] In some embodiments, the compaction density of the positive electrode sheet is in the range of 2.55 g / cc to 2.75 g / cc.

[0050] The embodiments of this application improve the energy density of a single battery cell by using a positive electrode sheet within the aforementioned compaction density range.

[0051] In some embodiments, the coating weight of the positive electrode film is 225 mg / 1540.25 mm. 2 ~320mg / 1540.25mm 2 Within the range.

[0052] The embodiments of this application improve the energy density of a single battery cell by employing a positive electrode film layer within the above-described coating weight range.

[0053] Secondly, embodiments of this application provide a battery device, comprising:

[0054] At least one battery cell provided by the first party;

[0055] Heating film, which is connected to the battery cell;

[0056] The control module communicates with the individual battery cells;

[0057] The control module is configured as follows:

[0058] The heating film is controlled to heat or stop heating the battery cells based on the temperature status information of the individual cells.

[0059] The embodiments of this application introduce a heating film into the battery cell, which can control the heating film to heat or stop heating the battery cell according to the temperature state information of the battery cell, so that the battery cell is in an appropriate temperature state, which can improve the low-temperature charging performance of the battery cell while increasing the energy density of the battery cell.

[0060] In some embodiments, the temperature state information includes a first temperature state and a second temperature state. Controlling the heating film to heat or stop heating the battery cell based on the temperature state information of the battery cell includes:

[0061] In response to the battery cell being in a first temperature state, the heating film is controlled to heat the battery cell.

[0062] In response to the battery cell being in the second temperature state, the heating film is controlled to stop heating the battery cell.

[0063] The first temperature state is defined as a temperature state that is less than or equal to a first preset temperature, and the second temperature state is defined as a temperature state that is greater than the first preset temperature, wherein the first preset temperature is 17℃~20℃.

[0064] The embodiments of this application control the heating film to heat or stop heating the battery cells by setting a first preset temperature, thereby regulating the temperature state of the battery cells and improving the low-temperature charging performance of the battery cells.

[0065] In some embodiments, the control module is further configured to: control the charging of the battery cell at a rate of 2C to 2.7C when the battery cell is at a temperature state of less than or equal to a second preset temperature; and / or control the charging of the battery cell at a rate of 0.3C to 1C when the battery cell is at a temperature state of greater than 30% SOC and less than or equal to 80% SOC; and / or control the charging of the battery cell at a rate of 0.1C to 0.3C when the battery cell is at a temperature state of greater than 80% SOC and less than or equal to 100% SOC.

[0066] And / or, the control module is further configured to: control the charging of the battery cell at a rate of 1.3C to 1.8C when the battery cell is at a temperature greater than a second preset temperature, such that the battery cell is at a state of less than or equal to 30% SOC; and / or control the charging of the battery cell at a rate of 0.3C to 1C when the battery cell is at a state of greater than 30% SOC and less than or equal to 80% SOC; and / or control the charging of the battery cell at a rate of 0.1C to 0.3C when the battery cell is at a state of greater than 80% SOC and less than or equal to 100% SOC.

[0067] The second preset temperature is 35℃~45℃.

[0068] The embodiments of this application reduce the heat generation of battery cells during charging by using different charging rate modes according to the temperature state of the battery cells, thereby reducing the temperature rise of battery cells during charging and improving the high-temperature charging performance of battery cells.

[0069] Thirdly, embodiments of this application provide an electrical device, including any of the battery cells provided in the first aspect or any of the battery devices provided in the second aspect.

[0070] The electrical devices provided in the embodiments of this application have at least the same advantages as individual battery cells, which can improve the battery life of the electrical devices. Attached Figure Description

[0071] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. Other drawings can be obtained based on these drawings without creative effort.

[0072] Figure 1 is a schematic diagram of the vehicle structure provided in an embodiment of this application;

[0073] Figure 2 is an exploded structural diagram of the battery device provided in an embodiment of this application;

[0074] Figure 3 is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0075] Explanation of icon numbers:

[0076] 1000-Vehicle, 100-Battery unit, 200-Controller, 300-Motor, 10-Housing, 20-Battery cell, 30-Heating film, 11-First part, 12-Second part, 21-End cap, 22-Housing shell, 23-Electrode assembly, 21a-Electrode terminal.

[0077] Embodiments of the present invention

[0078] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0079] For the sake of brevity, this article only discloses some specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0080] In this description, unless otherwise stated, the term "or" is inclusive. That is, the phrase "A or (or) B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0081] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0082] Unless otherwise stated, the terms used in this application have their common meanings in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0083] In low-temperature environments, battery cells require excessively long charging times, impacting the use of electric vehicles and other products, as well as their promotion in cold regions. Conversely, in high-temperature environments (~50°C), battery cells are prone to triggering high-temperature current limiting, which also affects charging time, consequently hindering the use and promotion of electric vehicles and other products in high-temperature regions.

[0084] Some existing solutions adjust the electrolyte composition of individual battery cells to improve their high-temperature charging performance. However, these solutions often negatively impact low-temperature charging performance while improving high-temperature charging performance, making it difficult to meet the wide temperature range requirements of battery cells. In recent years, numerous studies have focused on the high-temperature or low-temperature charging performance of individual battery cells, but few solutions have achieved a balance between both.

[0085] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecraft.

[0086] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0087] Please refer to Figure 1, which is a structural schematic diagram of a vehicle provided in an embodiment of this application.

[0088] Referring to Figure 1, vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. The battery device 100 can be used to power vehicle 1000; for example, it can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the battery device 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during starting, navigation, and driving.

[0089] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0090] Please refer to Figure 2, which is an exploded structural diagram of the battery device provided in an embodiment of this application.

[0091] Referring to Figure 2, the battery device 100 includes a housing 10 and a plurality of battery cells 20, which are housed within the housing 10. The housing 10 provides a space for the battery cells 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, collectively defining a space for accommodating the battery cells 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 together define the space. Alternatively, both the first portion 11 and the second portion 12 may be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0092] In the battery device 100, multiple battery cells 20 can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, the battery device 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed configuration to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed configuration to form a whole, which is also housed within the housing 10. The battery device 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0093] Among them, the battery cell 20 can be in the form of a cylinder, a flat surface, a cuboid or other shapes.

[0094] Please refer to Figure 3, which is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0095] Referring to Figure 3, the battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0096] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure or impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy into battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components inside the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating element may be plastic, rubber, etc.

[0097] The outer casing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The outer casing 22 and the end cap 21 can be independent components. An opening can be provided on the outer casing 22, and the end cap 21 closes the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the outer casing 22 can be integrated. Specifically, the end cap 21 and the outer casing 22 can form a common connecting surface before other components are inserted into the casing. When it is necessary to encapsulate the interior of the outer casing 22, the end cap 21 closes the outer casing 22. The outer casing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the outer casing 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the outer casing 22 can be various, including but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0098] Electrode assembly 23 is the component in the battery cell 20 where the electrochemical reaction occurs. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery cell 20, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0099] To achieve the above objectives, a first aspect of this application provides a battery cell 20. The battery cell 20 includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material and a binder; the binder includes a lithium-containing polymer. The electrolyte includes a lithium salt; the lithium salt includes a fluorosulfonylimide lithium salt.

[0100] In some embodiments, a negative electrode film layer is disposed on one surface of the negative electrode current collector. In some embodiments, a negative electrode film layer is disposed on both opposite surfaces of the negative electrode current collector. In some embodiments, the negative electrode film layer is a single-layer film layer. In some embodiments, the negative electrode film layer includes two or more single-layer film layers.

[0101] Binders are used to create tight interfacial contact and electron migration channels between the negative electrode active material and other components and the negative electrode current collector.

[0102] Lithium-containing polymers may include aggregates of chemically homogeneous lithium-containing macromolecules, but differing in polymer, molar mass, and chain length, prepared by polymerization reactions. In some embodiments, the lithium-containing polymers may also include derivatives of the aforementioned aggregates of lithium-containing macromolecules formed by polymerization reactions, i.e., lithium-containing compounds obtained through reactions of the functional groups in the aforementioned lithium-containing macromolecules (e.g., addition or substitution reactions). In some embodiments, the lithium-containing polymer is a linear lithium-containing polymer, i.e., an unbranched lithium-containing polymer.

[0103] The embodiments of this application provide a binder comprising a lithium-containing polymer, which can establish a high solid-phase lithium-ion channel, reduce solid-phase mass transfer impedance, and thereby improve the charging performance of the battery cell 20.

[0104] In some embodiments, the negative electrode film may further include one or more of a negative electrode conductive agent and other optional additives. In some embodiments, the negative electrode conductive agent may be one or more of superconducting carbon, carbon black (for example, it may include one or more of acetylene black, Ketjen black, and Super P), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, other optional additives may be thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0105] The embodiments of this application introduce a binder including a lithium-containing polymer into the battery cell 20 to establish a high solid-phase lithium-ion channel, reduce solid-phase mass transfer impedance, and improve the low-temperature charging performance and high-temperature charging performance of the battery cell 20.

[0106] The embodiments of this application introduce fluorosulfonylimide lithium salt into the electrolyte, which makes the electrolyte have good thermal stability, reduces high-temperature gas generation and side reactions, thereby improving the high-temperature charging performance of the battery cell 20.

[0107] The types and contents of lithium salts in electrolytes can be quantitatively analyzed by ion chromatography. The retention time and peak area of ​​the chromatographic peaks in the reference solution and the actual electrolyte sample are determined by ion chromatography, and the lithium salt content is calculated. The specific steps include: taking 1.00 g (or 1 mL) of the electrolyte sample, dissolving it in pure water, methanol, or acetonitrile, transferring it to a 100 mL volumetric flask, and diluting it to the mark with solvent. After mixing, the sample is analyzed by ion chromatography.

[0108] The embodiments of this application utilize a binder comprising a lithium-containing polymer to establish a high solid-phase lithium-ion conduction channel, reducing solid-phase mass transfer impedance and thereby improving the charging performance of the battery cell 20. By introducing a fluorosulfonylimide lithium salt into the electrolyte, the electrolyte exhibits good thermal stability, reducing high-temperature gas generation and side reactions, thus improving the high-temperature charging performance of the battery cell 20. Therefore, a wide temperature range, long lifespan, and fast charging effect can be achieved in the high-energy-density battery cell 20.

[0109] In some embodiments, the chemical formula of the lithium-containing polymer includes [C6H7O2(OH)]. x (OCH2COOLi) y ] n And / or [CH2CH(COOLi)] n , where x+y=3, and the value of n ranges from 200 to 3500.

[0110] Lithium-containing polymers can be detected through chemical analysis. For example, infrared spectroscopy (IR) can be used to analyze negative electrode samples to detect the presence of characteristic absorption peaks of lithium-containing polymers. Studies have shown that specific infrared absorption peaks are generated during the synthesis of lithium-containing polymers, which can serve as direct evidence of their presence. Alternatively, electrochemical testing can be used. For example, cyclic voltammetry can be used to test the redox peaks of the negative electrode and compare their peak potentials. Lithium-containing polymers exhibit oxidation and reduction potentials that differ from other binders, which can be used to distinguish whether they contain lithium-containing polymers, such as [CH₂CH(COOLi)]. n Its oxidation potential is 2.15V and its reduction potential is 2.55V, which are different from the electrochemical properties of other adhesives.

[0111] The embodiments of this application utilize lithium-containing polymers with the above-described chemical formulas to establish high solid-phase lithium-ion channels, reduce solid-phase mass transfer impedance, and thereby improve the charging performance of the battery cell 20.

[0112] In some embodiments, the mass percentage of the binder is in the range of 1% to 6% based on the total mass of the negative electrode film. The mass percentage of the binder, based on the total mass of the negative electrode film, can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%, or a range of any two of the above values, for example, 1% to 3%, 2% to 4%, 3% to 5%, or 4% to 6%.

[0113] The embodiments of this application, through the binder within the above-mentioned mass percentage range, can establish a high solid-phase lithium-ion channel, reduce solid-phase mass transfer impedance, and thereby improve the charging performance of the battery cell 20.

[0114] In some embodiments, the lithium fluorosulfonylimide salt includes the lithium difluorosulfonylimide salt.

[0115] The embodiments of this application utilize the aforementioned fluorosulfonylimide lithium salt to achieve good thermal stability in the electrolyte, thereby reducing high-temperature gas generation and side reactions, and thus improving the high-temperature charging performance of the battery cell 20.

[0116] In some embodiments, the negative electrode active material includes artificial graphite; based on the total mass of the negative electrode film, the mass percentage of the negative electrode active material is in the range of 90% to 99%. Based on the total mass of the negative electrode film, the mass percentage of the negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, etc., or a range consisting of any two of the above values, for example, 90% to 94%, 92% to 96%, 94% to 98%, or 96% to 99%, etc.

[0117] Among them, artificial graphite refers to graphite materials obtained through organic carbonization followed by high-temperature graphitization. Due to its fewer defects, the application of artificial graphite as a negative electrode active material in negative electrode sheets is beneficial to improving the cycle life of battery cells 20.

[0118] The embodiments of this application improve the cycle life of the battery cell 20 by using the above-mentioned negative electrode active material and its mass percentage range in the negative electrode film layer.

[0119] In some embodiments, the negative electrode active material also includes amorphous carbon.

[0120] Amorphous carbon refers to a transitional state of carbon, generally referring to carbon elements other than graphite and diamond. In some embodiments, amorphous carbon includes one or both of hard carbon and soft carbon. Amorphous carbon has a large number of surface defects. Introducing amorphous carbon into the negative electrode active material is beneficial to increasing the number of sites for the insertion and extraction of active ions in the negative electrode active material, enabling active ions to diffuse more quickly in the particles of the negative electrode active material, thereby improving the charging performance of the battery cell 20.

[0121] The embodiments of this application improve the charging performance of the battery cell 20 by introducing amorphous carbon into the negative electrode active material.

[0122] In some embodiments, at least a portion of the surface of the artificial graphite is covered with amorphous carbon.

[0123] The presence of at least a portion of the surface of the artificial graphite in this application covered with amorphous carbon can be tested using equipment and methods known in the art. As an example, the specific morphology of the negative electrode active material can be observed using a transmission electron microscope.

[0124] The embodiments of this application improve the charging performance of the battery cell 20 by using artificial graphite with at least a portion of its surface covered with amorphous carbon.

[0125] In some embodiments, the mass percentage of amorphous carbon is in the range of 1% to 5% based on the total mass of the negative electrode film. The mass percentage of amorphous carbon, based on the total mass of the negative electrode film, can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any range of two of the above values, for example, 1% to 3%, 2% to 4%, or 3% to 5%.

[0126] The embodiments of this application improve the charging performance of the battery cell 20 by using amorphous carbon within the above-mentioned mass percentage range.

[0127] In some embodiments, the specific capacity of the negative electrode active material is in the range of 330 mAh / g to 360 mAh / g. The specific capacity of the negative electrode active material can be 330 mAh / g, 335 mAh / g, 340 mAh / g, 345 mAh / g, 350 mAh / g, 355 mAh / g, 360 mAh / g, etc., or a range of any two of the above values, for example, 330 mAh / g to 350 mAh / g or 340 mAh / g to 360 mAh / g, etc.

[0128] The specific capacity of the negative electrode active material refers to the ratio of the electrical capacity that the negative electrode active material inside the battery cell 20 can release to the mass of the negative electrode active material. It is an important indicator for measuring the energy storage capacity of the negative electrode active material in the battery cell 20, and is usually expressed in milliampere-hours per gram (mAh / g).

[0129] The specific capacity of the negative electrode active material can be tested using any known method. As an example, a method for testing the specific capacity of the negative electrode active material may include: assembling a CR2430 coin cell using the negative electrode sheet of this invention as the positive electrode, a lithium metal sheet as the negative electrode, a separator, and an electrolyte in an argon-protected glove box. The resulting coin cell is left to stand for 12 hours, then discharged at a constant current of 0.05C to 0.005V, left to stand for 10 minutes, then discharged at a constant current of 50μA to 0.005V, left to stand for 10 minutes, and then discharged at a constant current of 10μA to 0.005V. Finally, it is charged at a constant current of 0.1C to 2V, and the charging capacity is recorded. The ratio of the charging capacity to the mass of the negative electrode active material is the specific capacity of the negative electrode active material.

[0130] The embodiments of this application improve the energy density of the battery cell 20 by using negative electrode active materials within the above-mentioned specific capacity range.

[0131] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the second negative electrode film layer being disposed between the first negative electrode film layer and the negative electrode current collector. The first negative electrode film layer includes a first negative electrode active material and a first binder, the first binder including a first lithium-containing polymer. The second negative electrode film layer includes a second negative electrode active material and a second binder; the second binder includes a second lithium-containing polymer. Based on the total mass of the first negative electrode film layer, the mass percentage of the first binder is in the range of 1% to 5%. Based on the total mass of the second negative electrode film layer, the mass percentage of the second binder is in the range of 2% to 6%.

[0132] Based on the total mass of the first negative electrode film layer, the mass percentage of the first binder can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., or a range of any two of the above values, for example, 1%~3%, 2%~4%, 3%~5%, etc.

[0133] Based on the total mass of the second negative electrode film, the mass percentage of the second binder can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%, or a range of any two of the above values, such as 2%~4%, 3%~5%, or 4%~6%.

[0134] The embodiments of this application establish a high solid-phase lithium-ion channel by adjusting the mass ratio of the binder in each layer of the negative electrode film, thereby reducing the solid-phase mass transfer impedance and improving the low-temperature charging performance and high-temperature charging performance of the battery cell 20.

[0135] In some embodiments, the compaction density of the negative electrode sheet is in the range of 1.5 g / cc to 1.7 g / cc.

[0136] The compaction density of the negative electrode film can be 1.5 g / cc, 1.55 g / cc, 1.6 g / cc, 1.65 g / cc, 1.7 g / cc, or any range of two of the above values, such as 1.5 g / cc to 1.6 g / cc or 1.6 g / cc to 1.7 g / cc.

[0137] The compaction density of the negative electrode film refers to the weight per unit volume of the material forming the negative electrode film on the negative electrode current collector after compaction treatment, usually expressed in g / cc (grams per cubic centimeter). The compaction density reflects the degree of compaction of the material forming the negative electrode film. The compaction density of the negative electrode film can be tested using equipment and methods known in the art. The compaction density of the negative electrode film is equal to the ratio of the coating weight of the negative electrode film to the thickness of the negative electrode film. The coating weight of the negative electrode film refers to the weight of the material forming the negative electrode film per unit area coated on the negative electrode current collector, and can be expressed as mg / 1540.25mm². 2 The weight of the negative electrode coating is measured in milligrams per 1540.25 mm². The coating weight can be tested using equipment and methods known in the art, for example, by taking a single-sided coated negative electrode sheet that has been cold-pressed (if it is a double-sided coated negative electrode sheet, the negative electrode film on one side can be wiped off first), and cutting it into pieces with an area of ​​1540.25 mm². 2 Take the small disc and weigh it; then wipe off the negative electrode film layer of the weighed negative electrode sheet and weigh the negative electrode current collector. The coating weight of the negative electrode film layer is equal to the weight of the small disc minus the weight of the negative electrode current collector.

[0138] The embodiments of this application improve the energy density of the battery cell 20 by using a negative electrode film layer within the above-mentioned compaction density range.

[0139] In some embodiments, the coating weight of the negative electrode film is 140 mg / 1540.25 mm. 2 ~170mg / 1540.25mm 2 Within the range.

[0140] The coating weight of the negative electrode film can be 140mg / 1540.25mm. 2 145mg / 1540.25mm 2 150mg / 1540.25mm 2 155mg / 1540.25mm 2 160mg / 1540.25mm 2 165mg / 1540.25mm 2 170mg / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 140mg / 1540.25mm. 2 ~150mg / 1540.25mm 2 145mg / 1540.25mm 2 ~155mg / 1540.25mm 2 150mg / 1540.25mm 2~160mg / 1540.25mm 2 Or 160mg / 1540.25mm 2 ~170mg / 1540.25mm 2 wait.

[0141] The embodiments of this application improve the energy density of the battery cell 20 by employing a negative electrode film layer within the above-described coating weight range.

[0142] In some embodiments, the mass percentage of the fluorosulfonylimide lithium salt is in the range of 1% to 5% based on the total mass of the electrolyte. Based on the total mass of the lithium salt, the mass percentage of the fluorosulfonylimide lithium salt can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., or a range of any two of the above values, such as 1% to 3%, 2% to 4%, or 3% to 5%, etc.

[0143] The embodiments of this application improve the high-temperature stability of the electrolyte, reduce high-temperature gas generation and side reactions, improve the film formation stability of the SEI film of the negative electrode layer, and improve the high-temperature charging performance of the battery cell 20 by introducing fluorinated sulfonamide lithium salt within the above-mentioned mass percentage range into the electrolyte.

[0144] In some embodiments, the lithium salt further includes lithium hexafluorophosphate. The mass percentage of lithium hexafluorophosphate is in the range of 5% to 12% based on the total mass of the electrolyte. Based on the total mass of the lithium salt, the mass percentage of lithium hexafluorophosphate can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, etc., or a range consisting of any two of the above values, such as 5%~7%, 6%~8%, 7%~9%, 8%~10%, or 10%~12%, etc.

[0145] The embodiments of this application introduce lithium hexafluorophosphate within the above-mentioned mass percentage range into the electrolyte, thereby giving the electrolyte higher solubility, better antioxidant capacity and stronger electrochemical stability, and improving the cycle life of the battery cell 20.

[0146] In some embodiments, the lithium salt may also include one or more of lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0147] In some embodiments, the concentration of the lithium salt is in the range of 0.8 mol / L to 1.1 mol / L. The concentration of the lithium salt can be 0.8 mol / L, 0.81 mol / L, 0.82 mol / L, 0.83 mol / L, 0.84 mol / L, 0.85 mol / L, 0.86 mol / L, 0.87 mol / L, 0.88 mol / L, 0.9 mol / L, 0.91 mol / L, 0.92 mol / L, 0.93 mol / L, 0.94 mol / L, 0.95 mol / L, 0.96 mol / L, 0.97 mol / L, 0.98 mol / L, 1.0 mol / L, 1.1 mol / L, etc., or a range consisting of any two of the above values, for example, 0.8 mol / L to 1.0 mol / L or 0.9 mol / L to 1.1 mol / L, etc.

[0148] Lithium salts are compounds containing lithium ions that act as carriers of lithium ions in electrolytes, migrating between the positive and negative electrodes.

[0149] The embodiments of this application, by employing lithium salts of the above concentration, are beneficial to improving the film-forming stability of the electrolyte at the negative electrode, regulating the conductivity of the electrolyte, enhancing the migration rate of lithium ions, and improving the cycle life of the battery cell 20.

[0150] In some embodiments, the conductivity of the electrolyte is in the range of 6 mS / m to 10 mS / m. The conductivity of the electrolyte can be 6 mS / cm, 6.1 mS / cm, 6.2 mS / cm, 6.3 mS / cm, 6.4 mS / cm, 6.5 mS / cm, 6.6 mS / cm, 6.7 mS / cm, 6.8 mS / cm, 6.9 mS / cm, 7 mS / cm, 7.1 mS / cm, 7.2 mS / cm, 7.3 mS / cm, 7.4 mS / cm, 7.5 mS / cm, 7.6 mS / cm, 7.7 mS / cm, 7.8 mS / cm, 7.9 mS / cm, 8 mS / cm, 8.1 mS / cm, 8... 2 mS / cm, 8.3 mS / cm, 8.4 mS / cm, 8.5 mS / cm, 8.6 mS / cm, 8.7 mS / cm, 8.8 mS / cm, 8.9 mS / cm, 9 mS / cm, 9.1 mS / cm, 9.2 mS / cm, 9.3 mS / cm, 9.4 mS / cm, 9.5 mS / cm, 9.6 mS / cm, 9.7 mS / cm, 9.8 mS / cm, 9.9 mS / cm, 10 mS / cm, etc., or any range of two of the above values, such as 6 mS / cm~8 mS / cm, 7 mS / cm~9 mS / cm, or 8 mS / cm~10 mS / cm, etc.

[0151] Electrolyte conductivity refers to the ability of active ions to conduct within the electrolyte. Higher conductivity indicates greater conductivity of active ions, which is beneficial for improving the charging performance of individual battery cells. The conductivity of the electrolyte at 25°C can be tested using any known method. For example, a possible electrolyte testing method includes: heating the test sample and standard liquid to 25°C (±0.1°C); calibrating the testing instrument (Leici DDSJ-308F) using two standard liquids at an ambient temperature of 25°C (±0.5°C); after calibration and cleaning the electrodes, vertically immersing the test sample electrode in the test liquid to begin testing; and recording the test results after the data has stabilized for at least 10 seconds.

[0152] The embodiments of this application improve the transport capability of lithium ions in the electrolyte by using an electrolyte within the above-mentioned conductivity range, thereby enhancing the charging performance of the battery cell 20.

[0153] In some embodiments, the viscosity of the electrolyte is in the range of 25 mPa·s to 35 mPa·s. The viscosity of the electrolyte can be 25 mPa·s, 26 mPa·s, 27 mPa·s, 28 mPa·s, 29 mPa·s, 30 mPa·s, 31 mPa·s, 32 mPa·s, 33 mPa·s, 34 mPa·s, 35 mPa·s, etc., or a range of any two of the above values, for example, 25 mPa·s to 30 mPa·s, 28 mPa·s to 32 mPa·s, or 30 mPa·s to 35 mPa·s, etc.

[0154] The viscosity of the electrolyte can be tested using any known method. As an example, methods for testing the viscosity of the electrolyte may include: using a Bollerfeld (DV) method... The viscosity of the finished electrolyte was tested using a 2TLV viscometer. The ambient temperature was controlled at 25℃ and the ambient humidity was <80%. 30mL of electrolyte was taken and kept at a constant temperature in a water bath at 25℃ for at least 30min. The rotor was placed in the sample cup, and the sample was added to a depth of about 0.3cm from the cup opening. The connected viscometer was started, and the test was performed at a speed of 70rpm. Ten data points were collected, and the average value of the multiple points was calculated.

[0155] The embodiments of this application improve the wetting effect of the positive electrode film layer and the negative electrode film layer in the electrolyte by using an electrolyte within the above viscosity range, thereby improving the liquid phase transport conditions of lithium ions and providing more active sites in the negative electrode film layer for lithium ion insertion, thereby improving the charging performance of the battery cell 20.

[0156] In some embodiments, the electrolyte injection coefficient is in the range of 2.8 g / Ah to 3.4 g / Ah.

[0157] The electrolyte injection coefficient is the ratio of the amount of electrolyte injected to the battery's rated capacity. The battery's rated capacity refers to the amount of electricity the battery can discharge to its cutoff voltage under specified charge and discharge conditions.

[0158] The embodiments of this application improve the uniformity of electrolyte distribution within the battery cell 20 by using electrolytes within the above-mentioned electrolyte injection coefficient range, improve the film formation stability of electrolytes on the negative electrode sheet, and enhance the cycle life of the battery cell 20.

[0159] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material; the positive electrode active material includes a lithium phosphate with an olivine structure.

[0160] The olivine-structured lithium phosphate has a stable layered structure, which is beneficial to improving the cycle life of the battery cell 20.

[0161] The embodiments of this application use positive electrode sheets including the above-mentioned positive electrode active materials to improve the cycle life of the battery cell 20.

[0162] In some embodiments, the weight percentage of lithium phosphate with an olivine structure is in the range of 95% to 97% based on the total mass of the positive electrode film.

[0163] Based on the total mass of the positive electrode film, the weight percentage of lithium phosphate in the olivine structure can be 95%, 95.5%, 96%, 96.5%, 97%, or any range of two of the above values, such as 95%~96%, 95.5%~96.5%, or 96%~97%.

[0164] The embodiments of this application improve the energy density of the battery cell 20 by adjusting the mass ratio of lithium phosphate with olivine structure based on the total mass of the positive electrode film layer.

[0165] In some embodiments, the specific capacity of the positive electrode active material is in the range of 140 mAh / g to 150 mAh / g. The specific capacity of the positive electrode active material can be 140 mAh / g, 141 mAh / g, 142 mAh / g, 143 mAh / g, 144 mAh / g, 145 mAh / g, 146 mAh / g, 147 mAh / g, 148 mAh / g, 149 mAh / g, 150 mAh / g, etc., or a range of any two of the above values, for example, 140 mAh / g to 145 mAh / g or 145 mAh / g to 160 mAh / g, etc.

[0166] The specific capacity of the positive electrode active material refers to the ratio of the electrical capacity that the positive electrode active material inside the battery cell 20 can release to the mass of the positive electrode active material. It is an important indicator for measuring the energy storage capacity of the positive electrode active material in the battery cell 20, and is usually expressed in milliampere-hours per gram (mAh / g).

[0167] The specific capacity of the positive electrode active material can be tested using any known method. As an example, a method for testing the specific capacity of the positive electrode active material may include: assembling a CR2430 coin cell using the positive electrode sheet of this invention as the positive electrode, a lithium metal sheet as the negative electrode, a separator, and an electrolyte in an argon-protected glove box. The resulting coin cell is left to stand for 12 hours, then discharged at a constant current of 0.05C to 0.005V, left to stand for 10 minutes, then discharged at a constant current of 50μA to 0.005V, left to stand for 10 minutes, and then discharged at a constant current of 10μA to 0.005V; then charged at a constant current of 0.1C to 2V, and the charging capacity is recorded. The ratio of the charging capacity to the mass of the positive electrode active material is the specific capacity of the positive electrode active material.

[0168] The embodiments of this application improve the energy density of the battery cell 20 by using positive electrode active materials within the above-mentioned specific capacity range.

[0169] In some embodiments, the compaction density of the positive electrode sheet is in the range of 2.55 g / cc to 2.75 g / cc.

[0170] The compaction density of the positive electrode sheet can be 2.55 g / cc, 2.60 g / cc, 2.65 g / cc, 2.70 g / cc, 2.75 g / cc, or any range of two of the above values, such as 2.55 g / cc to 2.65 g / cc, 2.60 g / cc to 2.70 g / cc, or 2.65 g / cc to 2.75 g / cc.

[0171] The compaction density of the positive electrode sheet refers to the weight per unit volume of the material forming the positive electrode film layer on the positive electrode current collector after compaction treatment, usually expressed in g / cc (grams per cubic centimeter). The compaction density of the positive electrode sheet reflects the degree of compaction of the material forming the positive electrode film layer. The compaction density of the positive electrode sheet can be tested using equipment and methods known in the art. The compaction density of the positive electrode sheet is equal to the ratio of the coating weight of the positive electrode film layer to the thickness of the positive electrode film layer. The coating weight of the positive electrode film layer refers to the weight per unit area of ​​the material forming the positive electrode film layer on the positive electrode current collector, and can be expressed as mg / 1540.25mm². 2The weight of the positive electrode coating is measured in milligrams per 1540.25 square millimeters. The coating weight can be tested using equipment and methods known in the art, for example, by taking a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the coating on one side can be wiped off first), and cutting it into pieces with an area of ​​1540.25 mm². 2 Take the small circular electrode and weigh it; then wipe off the positive electrode film layer of the weighed positive electrode sheet and weigh the positive current collector. The coating weight of the positive electrode film layer is equal to the weight of the small circular electrode sheet minus the weight of the positive current collector.

[0172] The embodiments of this application improve the energy density of the battery cell 20 by using positive electrode sheets within the above-mentioned compaction density range.

[0173] In some embodiments, the coating weight of the positive electrode film is 225 mg / 1540.25 mm. 2 ~320mg / 1540.25mm 2 Within this range. The coating weight of the positive electrode film can be 225mg / 1540.25mm. 2 230mg / 1540.25mm 2 235mg / 1540.25mm 2 240mg / 1540.25mm 2 245mg / 1540.25mm 2 250mg / 1540.25mm 2 255mg / 1540.25mm 2 260mg / 1540.25mm 2 265mg / 1540.25mm 2 270mg / 1540.25mm 2 275mg / 1540.25mm 2 280mg / 1540.25mm 2 285mg / 1540.25mm 2 290mg / 1540.25mm 2 295mg / 1540.25mm 2 300mg / 1540.25mm 2 305mg / 1540.25mm 2 310mg / 1540.25mm 2 315mg / 1540.25mm 2 320mg / 1540.25mm 2 etc., or a range consisting of any two of the above values, for example, 225mg / 1540.25mm.2 ~255mg / 1540.25mm 2 240mg / 1540.25mm 2 ~280mg / 1540.25mm 2 260mg / 1540.25mm 2 ~300mg / 1540.25mm 2 Or 280mg / 1540.25mm 2 ~320mg / 1540.25mm 2 wait.

[0174] The embodiments of this application improve the energy density of the battery cell 20 by employing a positive electrode film layer within the above-described coating weight range.

[0175] Secondly, referring to FIG2, an embodiment of this application provides a battery device 100, which includes a heating film 30, a control module (not shown), and at least one battery cell 20 provided in the first aspect. The heating film 30 is connected to the battery cell 20. The control module is communicatively connected to the battery cell 20. The control module is configured to control the heating film 30 to heat or stop heating the battery cell 20 based on the temperature status information of the battery cell 20.

[0176] The control module refers to the module that manages and optimizes the battery cell 20 based on its parameter information.

[0177] In some existing solutions, a water-cooled plate is placed between the battery cells 20 in the battery device 100. The water-cooled plate cools the battery cells 20 at high temperatures and heats them at low temperatures. However, the design of the water-cooled plate will encroach on the storage space of the battery cells 20 in the battery device 100, which will have an adverse effect on the energy density of the battery device 100.

[0178] The embodiments of this application introduce a heating film 30 into the battery device 100, which can control the heating film 30 to heat or stop heating the battery cell 20 according to the temperature state information of the battery cell 20, so that the battery cell 20 is in an appropriate temperature state, which can improve the low-temperature charging performance of the battery device 100 while increasing the energy density of the battery device 100.

[0179] In some embodiments, the temperature state information includes a first temperature state and a second temperature state. Controlling the heating film 30 to heat or stop heating the battery cell 20 based on the temperature state information of the battery cell 20 includes:

[0180] In response to the battery cell 20 being in a first temperature state, the heating film 30 is controlled to heat the battery cell 20.

[0181] In response to the battery cell 20 being in the second temperature state, the heating film 30 is controlled to stop heating the battery cell 20.

[0182] The first temperature state is defined as a temperature state that is less than or equal to a first preset temperature, and the second temperature state is defined as a temperature state that is greater than the first preset temperature, wherein the first preset temperature is 17℃~20℃.

[0183] The embodiments of this application control the heating film 30 to heat or stop heating the battery cell 20 by setting a first preset temperature, thereby regulating the temperature state of the battery cell 20 and improving the low-temperature charging performance of the battery cell 20.

[0184] In some embodiments, the control module is further configured to: control the charging of the battery cell 20 at a rate of 2C to 2.7C when the battery cell 20 is at a temperature state less than or equal to a second preset temperature; and / or control the charging of the battery cell 20 at a rate of 0.3C to 1C when the battery cell 20 is at a temperature state greater than 30% and less than or equal to 80% SOC; and / or control the charging of the battery cell 20 at a rate of 0.1C to 0.3C when the battery cell 20 is at a temperature state greater than 80% and less than or equal to 100% SOC.

[0185] And / or, the control module is further configured to: control the charging of the battery cell 20 at a rate of 1.3C to 1.8C when the battery cell 20 is at a temperature greater than a second preset temperature; and / or control the charging of the battery cell 20 at a rate of 0.3C to 1C when the battery cell 20 is at a temperature greater than 30% SOC and less than or equal to 80% SOC; and / or control the charging of the battery cell 20 at a rate of 0.1C to 0.3C when the battery cell 20 is at a temperature greater than 80% SOC and less than or equal to 100% SOC.

[0186] The second preset temperature is 35℃~45℃.

[0187] The embodiments of this application reduce the heat generation of the battery cell 20 during charging by using different charging rate modes according to the temperature state of the battery cell 20, thereby reducing the temperature rise of the battery cell 20 during charging and improving the high-temperature charging performance of the battery cell 20.

[0188] The beneficial effects of this application are further illustrated below with reference to the embodiments.

[0189] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0190] Example 1

[0191] The preparation of a single battery cell 20 includes the following steps:

[0192] (1) Provide positive electrode plates:

[0193] The positive electrode active material (lithium iron phosphate, specific capacity of 146 mAh / g), conductive agent (Super-P), binder (PVDF), and flexible agent (polyurethane resin) were mixed in a weight ratio of 97.3:0.7:1.8:0.2. Then, a solvent (N-methylpyrrolidone) was added, and after thorough mixing, the mixture was coated onto aluminum foil. Following drying and cold pressing, the positive electrode sheet was obtained. The compaction density of the positive electrode film was 2.6 g / cm³, and the coating weight of the positive electrode film was 300 mg / 1540.25 mm. 2 .

[0194] (2) Providing a negative electrode sheet: The first negative electrode active material (artificial graphite with a carbon coating), conductive agent (Super-P), and binder (lithium-containing polymer binder [C6H7O2(OH)2(OCH2COOLi)1] are combined. 600 The plasticizer (polyacrylic acid) is mixed evenly in a solvent (deionized water) at a weight ratio of 97:0.7:1.7:0.6 to obtain the first negative electrode film layer.

[0195] The composition includes: second negative electrode active material (artificial graphite with a carbon coating): conductive agent (Super-P): binder (lithium-containing polymer binder [C6H7O2(OH)2(OCH2COOLi)1)). 600 The plasticizer (polyacrylic acid) was mixed evenly in a solvent (deionized water) at a weight ratio of 96:0.7:2.9:0.4 to obtain the second negative electrode film layer.

[0196] The second negative electrode film is pre-coated onto a copper foil, and then the first negative electrode film is pre-coated onto the surface of the first negative electrode film away from the copper foil. After drying and cold pressing, the negative electrode sheet is obtained. The compaction density of the negative electrode film is 1.6 g / cm³. 3 The coating weight is 150mg / 1540.25mm. 2 .

[0197] (3) Provide a separating membrane:

[0198] A 7-micrometer-thick polyethylene film was used as the separator, with a porosity of 35% to 45%.

[0199] (4) Provide electrolyte:

[0200] The electrolyte comprises lithium salt, solvent, and additives; wherein the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) in a mass ratio of 3:7; the solvent is diethyl carbonate (DEC) / ethylene carbonate (EC) / ethyl methyl carbonate (EMC) in a volume ratio of 1:2:7; the additives are vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in a mass ratio of 2:1; the weight ratio of solvent:lithium salt:additives is 85%:12%:3%; and the concentration of lithium salt is 1M.

[0201] (5) The electrodes are arranged in the order of “separator-negative electrode-separator-positive electrode”. One end of the positive electrode, negative electrode and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode, negative electrode and two separators to obtain a dry cell. The dry cell is subjected to one liquid injection, high temperature settling, formation, second liquid injection and high temperature settling. The liquid injection coefficient is 3g / Ah to obtain 20 battery cells.

[0202] The steps for preparing battery cell 20 in Examples 2 to 4 are similar to those in Example 1. The difference is that in step (2) of Examples 2 to 4, the mass ratio of negative electrode active material, conductive agent, binder and plasticizer in the first negative electrode film layer and / or the second negative electrode film layer is different from that in Example 1. Specifically, in step (2) of Example 2, the mass ratio of the first negative electrode active material, conductive agent, binder, and plasticizer is 97:1:1:1; the mass ratio of the second negative electrode active material, conductive agent, binder, and plasticizer is 96:1:2.5:0.5; in step (2) of Example 3, the mass ratio of the second negative electrode active material, conductive agent, binder, and plasticizer is 94:0.5:5:0.5; in step (2) of Example 4, the mass ratio of the first negative electrode active material, conductive agent, binder, and plasticizer is 96.7:1:1.7:0.6; the mass ratio of the second negative electrode active material, conductive agent, binder, and plasticizer is 94.9:0.6:4:0.5.

[0203] The steps for preparing the battery cell 20 in Example 5 are similar to those in Example 4. The difference is that the specific capacity of the first negative electrode active material in step (2) of Example 5 is different from that in Example 4.

[0204] The steps for preparing the battery cell 20 in Examples 6 and 7 are similar to those in Example 1. The difference is that the specific composition of the binder for the first negative electrode film layer / second negative electrode film layer in the negative electrode sheet obtained in step (2) of Examples 6 and 7 is different from that in Example 1.

[0205] The steps for preparing battery cell 20 in Examples 8 to 9 are similar to those in Example 1. The difference is that the mass ratio of lithium fluorosulfonylimide salt in the electrolyte obtained in step (4) of Examples 8 to 9 is different from that in Example 1.

[0206] The steps for preparing the battery cell 20 in Comparative Example 1 are similar to those in Example 1, except that the binder used in step (2) of Comparative Example 1 is different from that in Example 1.

[0207] The steps for preparing battery cell 20 in Comparative Example 2 are similar to those in Example 1. The difference is that the lithium salt in the electrolyte in step (4) of Comparative Example 2 is different from that in Example 1. The lithium salt in the electrolyte in step (4) of Comparative Example 2 is 100% lithium hexafluorophosphate.

[0208] The battery cells 20 prepared in Examples 1 to 9 and Comparative Examples 1 to 2 were tested for room temperature capacity retention (cycle life), high temperature capacity retention (cycle life), energy density, room temperature charging performance, and low temperature charging performance. The test results are shown in Table 1.

[0209] (1) Room temperature capacity retention test:

[0210] At 25°C, the prepared battery cell 20 was charged at a constant current of 1C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0. Then, it was discharged at a rate of 1C followed by a discharge at 0.33C, and the discharge capacity C of each cycle was recorded. n Continue this process until the battery reaches 500 cycles, then record the capacity retention rate at this point. The capacity retention rate at this point is equal to C. 500 / C0*100%, the higher the capacity retention rate, the better the cycle life of the battery cell 20.

[0211] (2) High-temperature capacity retention test:

[0212] At 45°C, the prepared battery cell 20 was charged at a constant current of 1C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0. Then, it was discharged at a rate of 1C followed by a discharge at 0.33C, and the discharge capacity C of each cycle was recorded. nContinue this process until the battery reaches 500 cycles, then record the capacity retention rate at this point. The capacity retention rate at this point is equal to C. 500 / C0*100%, the higher the capacity retention rate, the better the cycle life of the battery cell 20.

[0213] (3) Room temperature charging performance test:

[0214] At 25°C, the prepared battery cell 20 was charged at a constant current of 0.33C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0.

[0215] Then, the battery cells 20 were sequentially charged at constant currents of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until they reached the full-cell charging cutoff voltage or the 0V negative electrode cutoff potential (whichever comes first). After each charging cycle, they were discharged at 1C0 until they reached the full-cell discharge cutoff voltage. The negative electrode potentials corresponding to the charging rates to 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% SOC (State of Charge) were recorded. The charging rates at different SOC states were plotted. The negative electrode potential curve, after linear fitting, yields the charging rate corresponding to a negative electrode potential of 0V under different SOC states. This charging rate is the charging window under that SOC state, denoted as C. 10 ％ SOC C 20 ％ SOC C 30 ％ SOC C 40 ％ SOC C 50 ％ SOC C 60 ％ SOC C 70 ％ SOC C 80 ％ SOC According to the formula (60 / C) 10 ％ SOC +60 / C 30 ％ SOC +60 / C40 ％ SOC +60 / C 50 ％ SOC +60 / C 60 ％ SOC +60 / C 70 ％ SOC +60 / C 80 ％ SOC The charging time T for the battery cell 20 from 10% SOC to 80% SOC is calculated by multiplying the charging time by 10%. The shorter the charging time, the better the charging performance.

[0216] (4) Low-temperature charging performance test:

[0217] At 0°C, the prepared battery cell 20 was charged at a constant current of 0.33C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. Its actual capacity was recorded as C0.

[0218] Then, the battery cells 20 were sequentially charged at constant currents of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until they reached the full-cell charging cutoff voltage or the 0V negative electrode cutoff potential (whichever comes first). After each charging cycle, they were discharged at 1C0 until they reached the full-cell discharge cutoff voltage. The negative electrode potentials corresponding to the charging rates to 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% SOC (State of Charge) were recorded. The charging rates at different SOC states were plotted. The negative electrode potential curve, after linear fitting, yields the charging rate corresponding to a negative electrode potential of 0V under different SOC states. This charging rate is the charging window under that SOC state, denoted as C. 10 ％ SOC C 20 ％ SOC C 30 ％ SOC C 40 ％ SOC C 50 ％ SOC C 60 ％ SOCC 70 ％ SOC C 80 ％ SOC According to the formula (60 / C) 10 ％ SOC +60 / C 30 ％ SOC +60 / C 40 ％ SOC +60 / C 50 ％ SOC +60 / C 60 ％ SOC +60 / C 70 ％ SOC +60 / C 80 ％ SOC The charging time T for the battery cell 20 from 10% SOC to 80% SOC is calculated by multiplying the charging time by 10%. The shorter the charging time, the better the charging performance.

[0219] (5) Energy density test:

[0220] The battery cells 20 prepared in each embodiment and comparative example were placed at 25°C and charged to 3.8V with a constant current of 0.33C, allowed to stand for 1 minute, and then charged to 0.05C with a constant voltage of 3.8V, allowed to stand for 30 minutes. They were then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 was recorded in Ah. The length, width, and height of the outer surface of the battery cell 20 were measured using calipers, and the cell volume V0 was calculated in L. The volumetric energy density VED of the battery cell 20 was calculated as (A0 × discharge plateau voltage of the battery cell 20) / V0, in Wh / L. It should be understood that the discharge plateau voltage of the battery cells 20 with different positive and negative electrode systems is different, which can be obtained by testing their charge-discharge curves or referring to existing literature. It should be noted that the energy density values ​​of some embodiments and / or comparative examples are rounded to show the same value.

[0221] Table 1 Performance test results of individual cells in each embodiment and comparative example

[0222]

[0223] As can be seen from Table 1, the embodiments of this application, by introducing a binder containing lithium polymer and a lithium salt containing fluorosulfonylimide into the battery cell 20, can achieve the effects of wide temperature range, long life and fast charging in the high energy density battery cell 20.

[0224] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0225] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0226] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A battery cell, wherein, The battery cell includes a positive electrode, a negative electrode, a separator, and an electrolyte; The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector; the negative electrode film layer includes a negative electrode active material and a binder; the binder includes a lithium-containing polymer. The electrolyte includes a lithium salt; the lithium salt includes a fluorosulfonylimide lithium salt.

2. The battery cell according to claim 1, wherein, The chemical formula of the lithium-containing polymer includes [C6H7O2(OH)]. x (OCH2COOLi) y ] n And / or [CH2CH(COOLi)] n , where x+y=3, and the value of n ranges from 200 to 3500.

3. The battery cell according to claim 1 or 2, wherein, Based on the total mass of the negative electrode film, the mass percentage of the binder is in the range of 1% to 6%.

4. The battery cell according to any one of claims 1 to 3, wherein, The fluorosulfonylimide lithium salt includes bisfluorosulfonylimide lithium salt.

5. The battery cell according to any one of claims 1 to 4, wherein, The negative electrode active material includes artificial graphite; based on the total mass of the negative electrode film, the mass percentage of the negative electrode active material is in the range of 90% to 99%.

6. The battery cell according to claim 5, wherein, The negative electrode active material also includes amorphous carbon.

7. The battery cell according to claim 6, wherein, At least a portion of the surface of the artificial graphite is covered with the amorphous carbon.

8. The battery cell according to claim 6 or 7, wherein, Based on the total mass of the negative electrode film, the mass percentage of amorphous carbon is in the range of 1% to 5%.

9. The battery cell according to any one of claims 1 to 8, wherein, The specific capacity of the negative electrode active material is in the range of 330 mAh / g to 360 mAh / g.

10. The battery cell according to any one of claims 1 to 9, wherein, The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, wherein the second negative electrode film layer is disposed between the first negative electrode film layer and the negative electrode current collector; the first negative electrode film layer includes a first negative electrode active material and a first binder, wherein the first binder includes a first lithium-containing polymer; the second negative electrode film layer includes a second negative electrode active material and a second binder; the second binder includes a second lithium-containing polymer; based on the total mass of the first negative electrode film layer, the mass percentage of the first binder is in the range of 1% to 5%; based on the total mass of the second negative electrode film layer, the mass percentage of the second binder is in the range of 2% to 6%.

11. The battery cell according to any one of claims 1 to 10, wherein, The compaction density of the negative electrode sheet is in the range of 1.5 g / cc to 1.7 g / cc.

12. The battery cell according to any one of claims 1 to 11, wherein, The coating weight of the negative electrode film is 140 mg / 1540.25 mm. 2 ~170mg / 1540.25mm 2 Within the range.

13. The battery cell according to any one of claims 1 to 12, wherein, Based on the total mass of the electrolyte, the mass percentage of the fluorosulfonylimide lithium salt is in the range of 1% to 5%.

14. The battery cell according to any one of claims 1 to 13, wherein, The lithium salt also includes lithium hexafluorophosphate; based on the total mass of the electrolyte, the mass percentage of lithium hexafluorophosphate is in the range of 5% to 12%.

15. The battery cell according to any one of claims 1 to 14, wherein, The conductivity of the electrolyte is in the range of 6 mS / m to 10 mS / m.

16. The battery cell according to any one of claims 1 to 15, wherein, The viscosity of the electrolyte is in the range of 25 mPa·s to 35 mPa·s.

17. The battery cell according to any one of claims 1 to 16, wherein, The electrolyte injection coefficient is in the range of 2.8 g / Ah to 3.4 g / Ah.

18. The battery cell according to any one of claims 1 to 17, wherein, The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector; the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes a lithium phosphate with an olivine structure.

19. The battery cell according to claim 18, wherein, Based on the total mass of the positive electrode film, the weight percentage of lithium phosphate in the olivine structure is in the range of 95% to 97%.

20. The battery cell according to claim 18 or 19, wherein, The specific capacity of the positive electrode active material is in the range of 140 mAh / g to 150 mAh / g.

21. The battery cell according to any one of claims 18 to 20, wherein, The compaction density of the positive electrode sheet is in the range of 2.55 g / cc to 2.75 g / cc.

22. The battery cell according to any one of claims 18 to 21, wherein, The coating weight of the positive electrode film is 225 mg / 1540.25 mm. 2 ~320mg / 1540.25mm 2 Within the range.

23. A battery device, wherein, include: At least one battery cell as described in any one of claims 1 to 22; A heating film, wherein the heating film is connected to the battery cell; The control module is communicatively connected to the individual battery cells; The control module is configured as follows: The heating film is controlled to heat or stop heating the battery cell based on the temperature status information of the battery cell.

24. The battery device according to claim 23, wherein, The temperature status information includes a first temperature status and a second temperature status; controlling the heating film to heat or stop heating the battery cell based on the temperature status information of the battery cell includes: In response to the battery cell being at a first temperature state, the heating film is controlled to heat the battery cell. In response to the battery cell being in a second temperature state, the heating film is controlled to stop heating the battery cell; Wherein, the first temperature state is defined as a temperature state less than or equal to a first preset temperature, and the second temperature state is defined as a temperature state greater than the first preset temperature, wherein the first preset temperature is 17℃~20℃.

25. The battery device according to claim 23 or 24, wherein, The control module is further configured to: control the charging of the battery cell at a rate of 2C to 2.7C when the battery cell is at a temperature less than or equal to a second preset temperature; and / or control the charging of the battery cell at a rate of 0.3C to 1C when the battery cell is at a temperature greater than 30% and less than or equal to 80% SOC; and / or control the charging of the battery cell at a rate of 0.1C to 0.3C when the battery cell is at a temperature greater than 80% and less than or equal to 100% SOC. And / or, the control module is further configured to: control the charging of the battery cell at a rate of 1.3C to 1.8C when the battery cell is at a temperature greater than a second preset temperature, such that the battery cell is at a state of less than or equal to 30% SOC; and / or control the charging of the battery cell at a rate of 0.3C to 1C when the battery cell is at a state of greater than 30% SOC and less than or equal to 80% SOC; and / or control the charging of the battery cell at a rate of 0.1C to 0.3C when the battery cell is at a state of greater than 80% SOC and less than or equal to 100% SOC. The second preset temperature is 35℃~45℃.

26. An electrical appliance, wherein, It includes a battery cell as described in any one of claims 1 to 22 or a battery device as described in any one of claims 23 to 25.

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