Battery cell, battery device, and electric device

Abstract

The invention discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises a winding battery cell, and the winding battery cell comprises a positive pole piece, a negative pole piece, electrolyte and an isolating membrane arranged between the positive pole piece and the negative pole piece; the positive pole piece comprises a positive current collector and a positive film layer arranged on at least one side of the surface of the positive current collector, the positive current collector comprises a positive current collecting part and positive tabs arranged on at least one side of the side surface of the positive current collecting part, and at least one circle of the positive pole piece comprises at least two positive tabs; the electrolyte comprises a solvent and an electrolyte salt, the solvent comprises a chain carboxylic ester solvent, and based on the total mass of the electrolyte, the mass ratio of the chain carboxylic ester solvent is greater than or equal to 5%; and the lithium ion conductivity of the electrolyte is 10 mS / cm to 25 mS / cm.

Description

[0001] This application is a divisional application based on the invention with application number 202411605958.3, application date November 12, 2024, applicant being Contemporary Amperex Technology Co., Ltd., and invention name being “Battery Cell, Battery Device and Electrical Device”. Technical Field

[0002] The present application relates to the technical field of battery cells, and in particular to a battery cell, a battery device and an electrical device. Background Art

[0003] In recent years, battery monomers have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0004] With the market's increasing demand for both energy density and fast-charging cycle life of battery cells, how to take both into account at the same time has become a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell having both good cycle life and fast charge cycle stability.

[0006] According to a first aspect of the present application, a battery cell is provided, which comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator arranged between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprises a positive current collector and a positive electrode film layer arranged on at least one side of the surface of the positive current collector, the positive current collector comprises a positive current collecting portion and a positive electrode ear arranged on at least one side of the side of the positive current collecting portion, and the width of the positive current collecting portion is 62mm-98mm; along the width direction of the positive current collecting portion, the size of the positive electrode film layer is 63mm-90mm; the lithium ion conductivity of the electrolyte is 10mS / cm-25mS / cm.

[0007] The electrolyte with lithium ion conductivity within the above range has a high lithium ion transmission rate, which can reduce the internal resistance of the battery cell, thereby reducing the temperature rise of the battery cell during the fast charging process, narrowing the temperature difference inside the battery cell, and reducing the negative impact of inconsistent temperature rise inside the battery cell on the fast charging cycle life of the battery, so that the battery cell can be compatible with a larger positive electrode collector width under the same temperature difference inside. The battery cell in the embodiment of the present application can improve the fast charging cycle life of the battery cell while maintaining a good energy density of the battery cell through the cooperation of the electrolyte and the positive electrode collector.

[0008] In any embodiment, the battery cell comprises a laminated battery cell, and the lithium ion conductivity of the electrolyte is 10 mS / cm-20 mS / cm.

[0009] In any embodiment, the electrolyte includes a solvent and an electrolyte salt, the solvent includes a chain carboxylate solvent, and based on the total mass of the electrolyte, the mass proportion of the chain carboxylate solvent is greater than or equal to 5%, and can be optionally 7%-75%.

[0010] The addition of chain carboxylic acid ester solvents to the electrolyte is not only conducive to improving the lithium ion conductivity of the electrolyte, but also can reduce the viscosity of the electrolyte, improve the infiltration between the electrolyte and the pole piece and the flow of the electrolyte in the width direction of the pole piece, further improve the transmission rate of lithium ions at the solid-liquid interface of the battery cell, reduce the internal resistance of the battery cell, reduce the temperature rise of the battery cell during the fast charging process, reduce the temperature difference inside the battery cell, and enable the battery cell to carry a larger positive electrode collector width at the same temperature rise. The battery cell in the embodiment of the present application can achieve a balance between the fast charging cycle life and energy density of the battery cell through the cooperation of the electrolyte and the positive electrode collector.

[0011] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the chain carboxylate solvent is 7%-60%.

[0012] Chain carboxylic acid ester solvents have high reactivity and are prone to side reactions with negative electrode materials, increasing battery gas production and having a negative impact on battery safety performance. Chain carboxylic acid ester solvents with a mass content within the above range can control the side reactions of battery monomers within a reasonable range, so that the battery monomers have good fast charge cycle life and energy density while also having low gas production levels, thus taking into account the safety performance of the battery.

[0013] In any embodiment, the electrolyte salt comprises lithium bis(fluorosulfonyl)imide, and based on the total mass of the electrolyte salt in the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide is 5%-60%, and optionally 10%-50%.

[0014] Lithium bis(fluorosulfonyl)imide is easy to dissociate in the electrolyte solvent, which is beneficial to improve the dynamics of the battery cell, reduce the internal resistance of the battery, further reduce the heat generation and temperature rise of the battery during fast charging, and alleviate the phenomenon of inconsistent internal temperature rise of the battery cell during fast charging. However, lithium bis(fluorosulfonyl)imide is easy to react with LiC formed during the deep lithium insertion process of the negative electrode. 6 The occurrence of side reactions reduces the reversible lithium capacity, which is not conducive to maintaining the battery cell capacity during the cycle. The electrolyte of lithium bis(fluorosulfonyl)imide within the above mass range can not only reduce the phenomenon of inconsistent temperature rise inside the battery cell, but also maintain the side reaction with the negative electrode material at a reasonable level, comprehensively improving the fast charge cycle life of the battery.

[0015] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 1%-10%, and optionally 1%-8%.

[0016] When the mass content of lithium bis(fluorosulfonyl)imide in the electrolyte is within the above range, the fast-charging cycle life of the battery cell can be further improved while taking into account the energy density of the battery cell.

[0017] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 3%-6%.

[0018] When the mass content of lithium bis(fluorosulfonyl)imide in the electrolyte is within the above range, the battery monomer can better balance fast charging cycle life and low gas production level while maintaining good energy density, thereby achieving a balance between fast charging cycle life and safety performance.

[0019] In any embodiment, the linear carboxylate solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate.

[0020] The above-mentioned chain carboxylic acid ester solvents have a small molecular volume, which is beneficial to reducing the viscosity of the electrolyte, increasing the infiltration rate of the electrolyte, improving the electrolyte dynamics, increasing the carrier transmission rate inside the battery cell, reducing the inconsistency of the current density inside the battery, and further reducing the inconsistent internal temperature rise of the battery cell during the fast charging process, thereby improving the fast charging cycle life of the battery cell.

[0021] In any embodiment, the chain carboxylate solvent includes one or more of ethyl acetate and methyl acetate. Based on the total mass of the solvent, the total mass of ethyl acetate and methyl acetate accounts for 5%-80%.

[0022] Compared with other chain carboxylic acid ester solvents, ethyl acetate and methyl acetate have both relatively high kinetic activity and relatively low gas production levels, which is beneficial to further improve the transmission rate of lithium ions and reduce the level of side reactions in the electrolyte, reduce the internal temperature difference of the battery cell during the fast charging process, take into account the fast charging cycle life and low gas production level of the battery cell, and achieve a balance between fast charging life and safety performance.

[0023] In any embodiment, the linear carboxylate solvent includes methyl acetate, and the mass content of methyl acetate is 5%-80%, optionally 5%-50%, based on the total mass of the solvent.

[0024] In any embodiment, along the width direction of the positive electrode current collecting portion, the size of the positive electrode film layer is 60 mm-97 mm, and can be optionally 63 mm-90 mm.

[0025] The size of the positive electrode film layer is within the above range and matches the size of the positive electrode current collector, which can further take into account the energy density of the battery cell.

[0026] In any embodiment, the positive electrode current collector comprises aluminum foil, and the thickness of the aluminum foil is 10 μm-16 μm.

[0027] When the thickness of the aluminum foil is within the above range, it will neither occupy too large a proportion of the battery's mass nor cause excessive internal resistance of the battery due to reduced flow area. It can reduce the heat generation and temperature rise of the battery during fast charging, alleviate the inconsistent temperature rise of the battery cells during fast charging, and take into account both the energy density and fast charging cycle life of the battery cells.

[0028] In any embodiment, the thickness of the aluminum foil is 12 μm-14 μm.

[0029] When the thickness of the aluminum foil is within the above range, the battery cell further improves the fast charging cycle life of the battery while taking into account the energy density.

[0030] In any embodiment, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes lithium iron phosphate and a modified material thereof.

[0031] In any embodiment, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the projection of the positive electrode film layer along the thickness direction falls within the range of the negative electrode film layer, and along the width direction of the negative electrode current collector, the distance between the edge of the negative electrode film layer and the projected edge of the positive electrode film layer adjacent thereto is 1mm-4mm.

[0032] During fast charging, the larger polarization of the negative electrode can easily cause the negative electrode lithium insertion potential to drop below 0V, resulting in the precipitation of lithium metal on the surface of the negative electrode. The precipitated metallic lithium easily reacts with the electrolyte to form high-resistance inorganic salts, reducing the battery capacity. The projection of the positive electrode film layer along the thickness direction falls within the range of the negative electrode film layer. On the one hand, it can reduce the risk of lithium precipitation of the battery cell during discharge and improve the fast charging performance of the battery. On the other hand, it is conducive to controlling the capacity loss caused by the diffusion of lithium ions into the excessive area of ​​the negative electrode, while taking into account the fast charging cycle life of the battery.

[0033] In any embodiment, the negative electrode current collector comprises copper foil, and the thickness of the copper foil is 4 μm-6 μm.

[0034] When the thickness of the copper foil is within the above range, it will neither occupy too large a proportion of the battery's mass, nor cause the battery's temperature to rise too much during fast charging, making it difficult for heat to dissipate. This can further take into account both the energy density and fast charging cycle life of the battery cell.

[0035] In any embodiment, the single-side density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 -0.20g / 1540.25mm 2 , optional: 0.10g / 1540.25mm 2 -0.16g / 1540.25mm 2 .

[0036] A battery cell with a single-side density of the negative electrode film layer within the above range can reduce the transmission distance of lithium ions in the negative electrode film layer, match the electrolyte with high conductivity, reduce the concentration polarization generated during fast charging, and is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0037] In any embodiment, the compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.9g / cm 3 , optional 1.2g / cm 3 -1.65g / cm 3 .

[0038] The negative electrode sheet with a compaction density within the above range has a suitable porosity, can match the electrolyte with high conductivity, facilitate the transmission of lithium ions in the negative electrode, reduce the concentration polarization generated during fast charging, and is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0039] In any embodiment, the average thickness of a single side of the negative electrode film layer is 30 μm-150 μm, and can be 30 μm-80 μm.

[0040] A battery cell with an average single-side thickness of the negative electrode film layer within the above range can reduce the transmission distance of lithium ions in the negative electrode film layer, match the electrolyte with high conductivity, reduce the concentration polarization generated during fast charging, and is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0041] In any embodiment, the porosity of the negative electrode sheet is 20%-60%, and optionally 25%-40%.

[0042] The negative electrode plate with a porosity within the above range can be matched with an electrolyte with high conductivity, thereby increasing the diffusion rate of lithium ions in the negative electrode and reducing the concentration polarization generated by the battery cell during fast charging, which is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0043] In any embodiment, the porosity of the isolation membrane is 25%-55%, and optionally 28%-42%.

[0044] The separator with a porosity within the above range is conducive to improving the liquid phase transmission rate of lithium ions and reducing the liquid phase transmission resistance of lithium ions, thereby reducing the impedance of the battery, reducing the temperature rise of the battery and the phenomenon of inconsistent temperature rise, so that the width of the current collector can be further increased and the energy density can be further increased. At the same time, the reduction in the temperature rise can reduce the degree of side reactions of the electrolyte and the negative electrode active material and reduce gas production. The porosity of the separator within the above range can also make the separator have a certain mechanical strength, while reducing the probability of lithium dendrites piercing the separator and causing a short circuit, and comprehensively improving the fast charging cycle life of the battery cell.

[0045] In any embodiment, the porosity of the separator is 30%-42%.

[0046] The isolation membrane with a porosity within the above range is conducive to further reducing the temperature rise of the battery and the phenomenon of inconsistent temperature rise, alleviating the technical problems of severe local polarization of the battery and increased risk of lithium plating, and further improving the fast charging cycle life of the battery cell on the basis of maintaining certain mechanical properties of the isolation membrane.

[0047] In any embodiment, the Gurley value G of the isolation membrane is 50s-620s, optionally 250s-610s, wherein the Gurley value refers to the time required for 100 mL of air to pass through 1 square inch of the isolation membrane under a pressure of 1.22 kPa when the isolation membrane is placed in an air permeability tester, and the unit is s.

[0048] The separator with a Gurley value within the above range is beneficial to reduce the impedance of the battery cell, reduce the temperature rise of the battery and the phenomenon of inconsistent temperature rise, so that the width of the current collector that the battery can carry is further increased, and the energy density is further increased. At the same time, the reduction in the temperature rise can reduce the degree of side reactions of the electrolyte and the negative electrode active material and reduce gas production. The Gurley value of the separator within the above range can also make the separator have a certain mechanical strength, while reducing the probability of lithium dendrites piercing the separator and causing a short circuit, and comprehensively improve the fast charging cycle life of the battery cell.

[0049] In any embodiment, the battery cell comprises a wound cell, wherein at least one turn of the positive electrode sheet of the wound cell comprises at least two positive electrode tabs.

[0050] In any embodiment, the negative electrode plate includes a negative electrode collector and a negative electrode film layer arranged on at least one side of the negative electrode collector, the negative electrode collector includes a negative electrode collecting part and a negative electrode tab arranged on at least one side of the negative electrode collecting part, and at least one circle of the negative electrode plate of the wound battery cell includes at least two negative electrode tabs.

[0051] In the prior art, a positive electrode sheet or a negative electrode sheet in a wound battery cell is usually provided with a pole ear in each winding circle. The embodiment of the present application reduces the overcurrent at the pole ear by providing at least two pole ears on at least one circle of the wound battery cell pole sheet, reduces the temperature rise at the pole ear, and alleviates the uneven current density distribution on the pole sheet and the inconsistent temperature rise inside the battery cell during the fast charging process, thereby improving the fast charging cycle life of the battery cell.

[0052] In any embodiment, the wound battery cell includes a large surface area and a bending area, and the positive electrode lug is arranged in the large surface area of ​​the wound battery cell. The number of layers of the positive electrode sheets in the wound battery cell is defined by the rule that the number of layers of the positive electrode sheets in the large surface area increases successively along the winding direction from the inside to the outside, and the positive electrode sheets of the wound battery cell have at least two consecutive layers, each of which is provided with a positive electrode lug.

[0053] In the prior art, the pole lugs in the wound battery cell are generally arranged in the Nth layer, the N+2nd layer, the N+4th layer, etc., and at most one pole lug is arranged in every two layers of the pole sheet in the wound battery cell. In the embodiment of the present application, the pole lugs are arranged in each of at least two consecutive layers of the pole sheet, that is, the pole lugs are arranged continuously in the Nth layer and the N+1 layer, so as to reduce the overcurrent at the pole lugs and reduce the temperature rise at the pole lugs, so that the uneven current density distribution on the pole sheet and the inconsistent temperature rise inside the battery cell during the fast charging process are alleviated, thereby improving the fast charging cycle life of the battery cell.

[0054] In any embodiment, the battery cell comprises a laminated battery core, and the length of the positive electrode current collecting portion in the laminated battery core is 100 mm-700 mm, and can be optionally 200 mm-600 mm.

[0055] During the research, the applicant found that the length of the current collector in the laminated battery cell has a key impact on the current uniformity and temperature rise consistency during the fast charging process of the battery cell. The length of the positive current collector in the laminated battery cell within the above range can further improve the phenomenon of inconsistent temperature rise during the fast charging process of the battery cell and improve the fast charging cycle life of the battery cell.

[0056] In any embodiment, the liquid filling coefficient of the battery cell is 2.5 g / Ah-3.1 g / Ah, and can be optionally 2.6 g / Ah-2.9 g / Ah.

[0057] Battery cells with a liquid filling coefficient within the above range can improve the wettability between the electrolyte and the electrode, reduce the battery interface resistance, and reduce the battery impedance, so that the phenomenon of inconsistent temperature rise in the current collector during fast charging can be alleviated, the width of the battery current collector can be further increased, and at the same time, the increase in gas production caused by the side reaction of the electrolyte solvent can be within a controllable range, further taking into account the battery's fast charging cycle performance, energy density and safety performance.

[0058] A second aspect of the present application provides a battery device, including the battery cell provided by the first aspect of the present application, and the battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0059] The third aspect of the present application further provides an electrical device, which includes the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0061] Figure 2 is a schematic diagram of a battery module according to an embodiment of the present application;

[0062] Figure 3 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0063] Figure 4 yes Figure 3 An exploded schematic diagram of a battery pack is shown;

[0064] Figure 5 is an exploded schematic diagram of a battery cell according to an embodiment of the present application;

[0065] Figure 6 is a schematic diagram of an electrical device using a battery cell as a power source according to an embodiment of the present application;

[0066] Figure 7 is a partial schematic diagram of a battery cell according to an embodiment of the present application;

[0067] Figure 8 is a schematic diagram of a positive electrode sheet according to an embodiment of the present application;

[0068] Fig. 9 It is a schematic diagram of a wound battery cell according to one embodiment of the present application.

[0069] Description of reference numerals:

[0070] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly; 6 wound battery cell; 61 large surface area; 62 bending area; 10 battery cell; 101 positive electrode sheet; 102 negative electrode sheet; 103 separator; 1011 positive current collector; 1012 positive electrode film layer; 10111 positive current collector; 10112 positive electrode ear; 1021 negative electrode collector; 1022 negative electrode film layer; 1023 negative electrode ear. DETAILED DESCRIPTION

[0071] Hereinafter, the battery cells, battery devices and power devices of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0072] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0073] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0074] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0075] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0076] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0077] Unless otherwise specified, the terms used in this application have the commonly understood meanings that are commonly understood by those skilled in the art.

[0078] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured by various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0079] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack.

[0080] A battery cell is the smallest unit of a battery, which can independently realize the functions of charging and discharging. The battery cell can be cylindrical, rectangular or in other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 The battery cell 5 is a rectangular parallelepiped structure as an example.

[0081] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a box and battery cells, and the battery cells or battery modules are accommodated in the box. In some embodiments, the box may serve as part of the chassis structure of the vehicle. For example, part of the box may become at least a part of the floor of the vehicle, or part of the box may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0082] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0083] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 2 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 2 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0084] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0085] In some embodiments, the battery modules and battery cells mentioned above may be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0086] Figure 3 and Figure 4 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 3 and Figure 4 As shown, the battery pack 1 may include a box body and a plurality of battery modules 4 disposed in the box body. The box body includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the box body in any manner.

[0087] The battery provided in the embodiment of the present application may include a lithium-ion battery.

[0088] A battery cell includes an electrode assembly and an electrolyte.

[0089] The battery cell may also include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte. The outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0090] In some embodiments, Figure 5 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0091] The electrode assembly usually includes a positive electrode plate and a negative electrode plate. The negative electrode plate is an electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode plate is an electrode that releases or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0092] At present, the charging time of lithium-ion batteries for pure electric vehicles is generally more than 1 hour, and the time required to fully charge is about 20 times the time it takes to fill up an ordinary fuel vehicle. Therefore, the charging speed of electric vehicles has become one of the most concerned issues for consumers, and improving the fast charging performance of batteries is a common pursuit of the industry. Although fast charging technology has increased the charging rate of batteries and shortened the charging time, it still faces the problem of fast reversible capacity decay and low fast charging cycle life during fast charging.

[0093] The applicant has found that the problem of low cycle life of fast-charging batteries is closely related to the high current density, fast temperature rise rate and large temperature rise amplitude during fast charging. During the battery charging process, the current first converges at the pole ear and then transmits to the current collector of the current collector. Since the electron transmission takes time, there is a difference in the current density between the pole ear and the current collector, and the difference in current density between the pole ear and the site at different distances from the pole ear on the current collector is also different. In general, the difference in current density between the current collector and the pole ear increases with the increase of the distance between the current collector and the pole ear, and also increases with the increase of current density. In other words, the phenomenon of inconsistent current density on the current collector is more significant during high-rate charging and discharging, that is, fast charging. According to Joule's law, the inconsistency of current density at different sites on the current collector will further lead to inconsistent temperature rise in different positions of the battery, increase the temperature gradient on the current collector, make the transmission rate of lithium ions inside the battery cell uneven, increase the risk of battery polarization and local lithium precipitation, and reduce the cycle life of the battery cell. Reducing the maximum distance between the bottom edge of the current collector (the side away from the pole ear) and the pole ear, that is, reducing the width of the current collector can alleviate the phenomenon of inconsistent temperature rise inside the battery cell during fast charging and improve the cycle stability of the battery cell during fast charging. However, the reduction in the width of the battery current collector will cause a decrease in the battery energy density.

[0094] Based on the above problems, this application provides a battery cell, see Figure 7 and Figure 8The battery cell 10 includes a positive electrode sheet 101, a negative electrode sheet 102, an electrolyte (not shown in the figure) and a separator 103 arranged between the positive electrode sheet 101 and the negative electrode sheet 102; the positive electrode sheet 101 includes a positive electrode collector 1011 and a positive electrode film layer 1012 arranged on at least one side of the surface of the positive electrode collector 1011, the positive electrode collector 1011 includes a positive electrode current collecting portion 10111 and a positive electrode ear 10112 arranged on at least one side of the side of the positive electrode current collecting portion 10111, and the width L1 of the positive electrode current collecting portion 10111 is 62mm-98mm; along the width direction of the positive electrode current collecting portion, the size of the positive electrode film layer is 63mm-90mm; the lithium ion conductivity of the electrolyte is 10mS / cm-25mS / cm.

[0095] Please continue to see Figure 8 The width L1 of the positive electrode current collector 10111 refers to the dimension of the positive electrode current collector 10111 in the direction perpendicular to the rolling direction of the positive electrode film layer 1012 in the positive electrode sheet 101, and also refers to the dimension of the positive electrode current collector 10111 in the direction perpendicular to the connection between the positive electrode tab 10112 and the positive electrode current collector 10111 (i.e. Figure 8 The size in the X direction.

[0096] The positive electrode current collector surface refers to a surface defined by the length and width of the positive electrode current collector; the positive electrode current collector side surface refers to a surface defined by the dimension of the positive electrode current collector in the thickness direction.

[0097] In some embodiments, the width L1 of the positive electrode current collector may be selected as 62 mm, 64 mm, 66 mm, 68 mm, 70 mm, 72 mm, 74 mm, 76 mm, 78 mm, 80 mm, 82 mm, 84 mm, 86 mm, 88 mm, 90 mm, 92 mm, 94 mm, 96 mm, 98 mm or any range therebetween.

[0098] The material of the positive electrode current collector is not particularly limited, as long as it does not cause chemical changes in the battery cell and has conductivity. The current collector includes a metal foil with a pure metal content of more than 95%, such as at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil, and also includes an alloy foil of at least two main elements, such as copper, aluminum, nickel, titanium, and iron. It can also include copper, aluminum-cadmium alloy, iron, or stainless steel that is surface-treated with carbon, nickel, titanium, silver, copper, etc. In addition, the binding force with the negative electrode active material can be enhanced by forming fine concave-convex on the surface, and it can be used in various forms such as film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0099] In the present application, the lithium ion conductivity of the electrolyte is the ability to describe the conductive process formed by the directional movement of dissociated ions in the electrolyte solution in an electric field, and can be tested by any known method in the art. As an example, disassemble the battery cell, take about 100mL of electrolyte sample with a dry, clean, corrosion-resistant sample bottle, seal it in a constant temperature water bath, shake the sample from time to time, and keep the temperature at 25°C (deviation ±0.5°C). After the sample temperature is constant, use a commercially available conductivity meter to test its conductivity. After the conductivity meter is wiped clean with calibration fluid, place it vertically in the liquid to be tested, click to start the test, and record the test results after the data is stable for more than 10s. It can be understood that the lithium ion conductivity of the electrolyte is closely related to the components and formulas in the electrolyte, such as the solvent, lithium-containing electrolyte salt, and additives.

[0100] In some embodiments, the lithium ion conductivity of the electrolyte may be selected to be 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, 19 mS / cm, 20 mS / cm, 21 mS / cm, 22 mS / cm, 23 mS / cm, 24 mS / cm, 25 mS / cm or any range therebetween.

[0101] The electrolyte with lithium ion conductivity within the above range has a high lithium ion transmission rate, which can reduce the internal resistance of the battery cell, thereby reducing the temperature rise of the battery cell during the fast charging process, narrowing the temperature difference inside the battery cell, and reducing the negative impact of inconsistent temperature rise inside the battery cell on the fast charging cycle life of the battery, so that the battery cell can be compatible with a larger positive electrode collector width under the same temperature difference inside. The battery cell in the embodiment of the present application can improve the fast charging cycle life of the battery cell while maintaining a good energy density of the battery cell through the cooperation of the electrolyte and the positive electrode collector.

[0102] In some embodiments, the battery cell comprises a laminated battery cell, and the lithium ion conductivity of the electrolyte is 10 mS / cm-20 mS / cm.

[0103] In some embodiments, the electrolyte includes a solvent and an electrolyte salt, the solvent includes a chain carboxylate solvent, and based on the total mass of the electrolyte, the mass proportion of the chain carboxylate solvent is greater than or equal to 5%, and can be optionally 7%-75%.

[0104] In the present application, chain carboxylate refers to a linear organic solvent containing a carboxylate group, including but not limited to one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate.

[0105] Herein, the type and mass content of each component in the electrolyte can be obtained by detecting the electrolyte by any method known to those skilled in the art. As an example, the composition and content of the electrolyte can be characterized by one or more of gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS). Exemplarily, referring to GB / T-9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" and / or GB / T6041-2002 "General Rules for Mass Spectrometry Methods", gas chromatography and mass spectrometry are used together. After the gas chromatography separates the components in the sample, each component is broken into ion fragments in the mass spectrum, and separated according to the mass-to-charge ratio (m / z) to form a specific mass spectrum, and the qualitative analysis of each organic component in the electrolyte is obtained. Then, the organic components in the electrolyte are separated in the chromatographic column and the detection signal spectra of each component are generated. The retention time is used for component qualitative analysis, and the peak area is calibrated to achieve quantitative analysis, and the quantitative test analysis of the organic components in the electrolyte is obtained. Referring to JY / T-020, the anion species of the electrolyte salt in the electrolyte are detected by ion chromatography and quantitatively tested. Referring to JY / T0578-2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0106] Herein, based on the total mass of the electrolyte, the mass content of the chain carboxylic acid ester solvent can be calculated by dividing the mass of the chain carboxylic acid ester solvent obtained by detection by the total mass of the electrolyte sample. The electrolyte referred to herein can be either a fresh electrolyte or an electrolyte obtained by disassembling a battery cell. The electrolyte obtained by disassembling a battery cell can be either a free electrolyte in the battery casing or an electrolyte obtained by centrifugation from a pole piece.

[0107] In some embodiments, based on the total mass of the electrolyte, the mass content of the linear carboxylate solvent can be selected to be 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or any numerical range therebetween.

[0108] The addition of chain carboxylic acid ester solvents to the electrolyte is not only conducive to improving the lithium ion conductivity of the electrolyte, but also can reduce the viscosity of the electrolyte, improve the infiltration between the electrolyte and the pole piece and the flow of the electrolyte in the width direction of the pole piece, further improve the transmission rate of lithium ions at the solid-liquid interface of the battery cell, reduce the internal resistance of the battery cell, reduce the temperature rise of the battery cell during the fast charging process, reduce the temperature difference inside the battery cell, and enable the battery cell to carry a larger positive electrode collector width at the same temperature rise. The battery cell in the embodiment of the present application can achieve a balance between the fast charging cycle life and energy density of the battery cell through the cooperation of the electrolyte and the positive electrode collector.

[0109] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the linear carboxylate solvent is 7%-60%.

[0110] Chain carboxylic acid ester solvents have high reactivity and are prone to side reactions with negative electrode materials, increasing battery gas production and having a negative impact on battery safety performance. Chain carboxylic acid ester solvents with a mass content within the above range can control the side reactions of battery monomers within a reasonable range, so that the battery monomers have good fast charge cycle life and energy density while also having low gas production levels, thus taking into account the safety performance of the battery.

[0111] In some embodiments, the electrolyte salt includes lithium bis(fluorosulfonyl)imide LiFSI, and based on the total mass of the electrolyte salt in the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide LiFSI is 5%-60%, and optionally 10%-50%.

[0112] In some embodiments, based on the total mass of the electrolyte salt in the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide may be selected to be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or any numerical range therebetween.

[0113] Lithium bis(fluorosulfonyl)imide is easy to dissociate in the electrolyte solvent, which is beneficial to improve the dynamics of the battery cell, reduce the internal resistance of the battery, further reduce the heat generation and temperature rise of the battery during fast charging, and alleviate the phenomenon of inconsistent internal temperature rise of the battery cell during fast charging. However, lithium bis(fluorosulfonyl)imide is easy to react with LiC formed during the deep lithium insertion process of the negative electrode. 6 The occurrence of side reactions reduces the reversible lithium capacity, which is not conducive to maintaining the battery cell capacity during the cycle. The electrolyte of lithium bis(fluorosulfonyl)imide within the above mass range can not only reduce the phenomenon of inconsistent temperature rise inside the battery cell, but also maintain the side reaction with the negative electrode material at a reasonable level, comprehensively improving the fast charge cycle life of the battery.

[0114] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide LiFSI is 1%-10%, and optionally 1%-8%.

[0115] In some embodiments, based on the total mass of the electrolyte, the mass content of the lithium bis(fluorosulfonyl)imide LiFSI may be 1%, 1.5%, 2%, 2.5%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or any range between the two.

[0116] When the mass content of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is within the above range, the fast charging cycle life of the battery cell can be further improved while taking into account the energy density of the battery cell.

[0117] In some embodiments, based on the total mass of the electrolyte, the mass of the lithium bis(fluorosulfonyl)imide LiFSI accounts for 3%-6%.

[0118] When the mass content of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is within the above range, the battery monomer can better balance fast charging cycle life and low gas production level while maintaining good energy density, thereby achieving a balance between fast charging life and safety performance.

[0119] In some embodiments, the linear carboxylate solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate.

[0120] The above-mentioned chain carboxylic acid ester solvents have a small molecular volume, which is beneficial to reducing the viscosity of the electrolyte, increasing the infiltration rate of the electrolyte, improving the electrolyte dynamics, increasing the carrier transmission rate inside the battery cell, reducing the inconsistency of the current density inside the battery, and further reducing the inconsistent internal temperature rise of the battery cell during the fast charging process, thereby improving the fast charging cycle life of the battery cell.

[0121] In some embodiments, the linear carboxylate solvent includes one or more of ethyl acetate and methyl acetate.

[0122] Compared with other chain carboxylic acid ester solvents, ethyl acetate and methyl acetate have both relatively high kinetic activity and relatively low gas production levels, which is beneficial to further improve the transmission rate of lithium ions and reduce the level of side reactions in the electrolyte, reduce the internal temperature difference of the battery cell during the fast charging process, take into account the fast charging cycle life and low gas production level of the battery cell, and achieve a balance between fast charging life and safety performance.

[0123] In some embodiments, based on the total mass of the solvent, the total mass of ethyl acetate and methyl acetate accounts for 5%-80%.

[0124] In some embodiments, based on the total mass of the solvent, the total mass proportion of ethyl acetate and methyl acetate can be selected to be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any numerical range therebetween.

[0125] In some embodiments, the linear carboxylic acid ester solvent includes methyl acetate.

[0126] In some embodiments, based on the total mass of the solvent, the mass content of methyl acetate is 5%-80%, optionally 5%-50%.

[0127] In some embodiments, the mass content of methyl acetate can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any numerical range therebetween, based on the total mass of the solvent.

[0128] In some embodiments, please continue to refer to Figure 7 and Figure 8 Along the width direction X of the positive electrode current collector, the size L2 of the positive electrode film layer 1012 is 60 mm-97 mm, and can be optionally 63 mm-90 mm.

[0129] In some embodiments, along the width direction X of the positive electrode current collecting portion, the size L2 of the positive electrode film layer 1012 can be selected as 60mm, 61mm, 62mm, 63mm, 64mm, 65mm, 66mm, 67mm, 70mm, 74mm, 77mm, 80mm, 84mm, 87mm, 90mm, 94mm, 97mm or any numerical range therebetween.

[0130] The size of the positive electrode film layer is within the above range and matches the size of the positive electrode current collector, which can further take into account the energy density of the battery cell.

[0131] In some embodiments, the positive electrode current collector includes aluminum foil, and the thickness of the aluminum foil is 10 μm-16 μm.

[0132] In some embodiments, the thickness of the aluminum foil may be 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or any range therebetween.

[0133] When the thickness of the aluminum foil is within the above range, it will neither occupy too large a proportion of the battery's mass nor cause excessive internal resistance of the battery due to reduced flow area. It can reduce the heat generation and temperature rise of the battery during fast charging, alleviate the inconsistent temperature rise of the battery cells during fast charging, and take into account both the energy density and fast charging cycle life of the battery cells.

[0134] In some embodiments, the aluminum foil has a thickness of 12 μm-14 μm.

[0135] When the thickness of the aluminum foil is within the above range, the battery cell further improves the fast charging cycle life of the battery while taking into account the energy density.

[0136] In some embodiments, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes lithium iron phosphate and a modified material thereof.

[0137] In some embodiments, the modified material of lithium iron phosphate includes one or more of a lithium iron phosphate coating material and a lithium iron phosphate doping material.

[0138] In some embodiments, please continue to refer to Figure 7 The negative electrode sheet 102 includes a negative electrode current collector 1021 and a negative electrode film layer 1022 arranged on at least one side of the negative electrode current collector 1021. The projection of the positive electrode film layer 1012 along the thickness direction Z falls within the range of the negative electrode film layer 1022, and along the width direction X of the negative electrode current collector 1021, the distance L3 between the edge of the negative electrode film layer 1022 and the projection edge of the adjacent positive electrode film layer 1012 is 1mm-4mm.

[0139] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As an example of a metal foil, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As an example of a three-dimensional porous current collector, copper mesh, nickel mesh, foam copper, foam nickel, and foam aluminum may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, aluminum, aluminum alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0140] In some embodiments, along the width direction of the negative electrode current collector, the distance between the edge of the negative electrode film layer and the projected edge of the adjacent positive electrode film layer can be selected to be 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm or any numerical range therebetween.

[0141] During fast charging, the larger polarization of the negative electrode can easily cause the negative electrode lithium insertion potential to drop below 0V, resulting in the precipitation of lithium metal on the surface of the negative electrode. The precipitated metallic lithium easily reacts with the electrolyte to form high-resistance inorganic salts, reducing the battery capacity. The projection of the positive electrode film layer along the thickness direction falls within the range of the negative electrode film layer. On the one hand, it can reduce the risk of lithium precipitation of the battery cell during discharge and improve the fast charging performance of the battery. On the other hand, it is conducive to controlling the capacity loss caused by the diffusion of lithium ions into the excessive area of ​​the negative electrode, while taking into account the fast charging cycle life of the battery.

[0142] In some embodiments, the negative electrode current collector includes copper foil, and the thickness of the copper foil is 4 μm-6 μm.

[0143] In some embodiments, the thickness of the copper foil may be 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm or any range therebetween.

[0144] When the thickness of the copper foil is within the above range, it will neither occupy too large a proportion of the battery's mass, nor cause the battery's temperature to rise too much during fast charging, making it difficult for heat to dissipate. This can further take into account both the energy density and fast charging cycle life of the battery cell.

[0145] In some embodiments, the single-side density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 -0.20g / 1540.25mm 2 , optional: 0.10g / 1540.25mm 2 -0.16g / 1540.25mm 2 .

[0146] In this application, the surface density of the film layer is a well-known meaning in the art and can be tested by methods known in the art. For example, take a single-sided coated and cold-pressed electrode (if it is a double-sided coated electrode, the film layer on one side can be wiped off first), and punch it into an area of ​​S 1 Weigh the small disc and record it as M 1 Then wipe off the film layer of the pole piece after weighing, weigh the weight of the current collector, and record it as M 0 . Single side density of the film layer = (M 1 -M 0 ) / S 1 In order to ensure the accuracy of the test results, multiple groups (eg, 10 groups) of samples to be tested may be tested, and the average value may be calculated as the test result.

[0147] In some embodiments, the single-side density of the negative electrode film layer can be selected to be 0.08 g / 1540.25 mm 2 , 0.09g / 1540.25mm 2 , 0.10g / 1540.25mm 2 , 0.11g / 1540.25mm 2 , 0.12g / 1540.25mm 2 , 0.13g / 1540.25mm 2 , 0.14g / 1540.25mm 2 , 0.15g / 1540.25mm 2 , 0.16g / 1540.25mm 2 , 0.17g / 1540.25mm 2 , 0.18g / 1540.25mm 2 , 0.19g / 1540.25mm 2 , 0.20g / 1540.25mm 2 Or any range of values ​​in between.

[0148] It can be understood that the single-side density of the negative electrode film layer is tested on the negative electrode sheet, and the single-side density of the positive electrode film layer is tested on the positive electrode sheet.

[0149] A battery cell with a single-side density of the negative electrode film layer within the above range can reduce the transmission distance of lithium ions in the negative electrode film layer, match the electrolyte with high conductivity, reduce the concentration polarization generated during fast charging, and is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0150] In some embodiments, the compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.9g / cm 3 , optional 1.2g / cm 3 -1.65g / cm 3 .

[0151] In this application, the compaction density of the negative electrode plate has a well-known meaning in the art and can be tested by methods known in the art. Remove the negative electrode plate from the lithium-ion battery, take a certain area of ​​the plate, and measure the mass and thickness of the plate and the current collector after removing the film layer. Calculate the compaction density of the plate according to the following formula. Compaction density of the plate = (pole plate mass - current collector mass) / [(pole plate thickness - current collector thickness) × pole plate area].

[0152] In some embodiments, the compaction density of the negative electrode sheet can be selected to be 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 Or any range of values ​​in between.

[0153] The negative electrode sheet with a compaction density within the above range has a suitable porosity, can match the electrolyte with high conductivity, facilitate the transmission of lithium ions in the negative electrode, reduce the concentration polarization generated during fast charging, and is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0154] In some embodiments, the average thickness of a single side of the negative electrode film layer is 30 μm-150 μm, and can be 30 μm-80 μm.

[0155] In some embodiments, the average thickness of a single side of the negative electrode film layer may be selected to be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm or any range of values ​​therebetween.

[0156] A battery cell with an average single-side thickness of the negative electrode film layer within the above range can reduce the transmission distance of lithium ions in the negative electrode film layer, match the electrolyte with high conductivity, reduce the concentration polarization generated during fast charging, and is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0157] In some embodiments, the porosity of the negative electrode sheet is 20%-60%, and optionally 25%-40%.

[0158] In the present application, the porosity of the pole piece can be tested by methods known in the art. For example, the test is based on the national standard GB / T24586-2009, the pole piece is immersed in ethyl methyl carbonate (EMC) for cleaning; a true density meter (instrument model is American Micrometer AccuPycII1340) is used for measurement based on the gas displacement method. Among them, the percentage of the pore volume in the pole piece to the total volume of the pole piece is the pole piece porosity, and the calculation formula is: Porosity = (V-V0) / V×100%, where V0 is the true volume and V is the apparent volume.

[0159] In some embodiments, the porosity of the negative electrode sheet may be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or any range therebetween.

[0160] The negative electrode plate with a porosity within the above range can be matched with an electrolyte with high conductivity, thereby increasing the diffusion rate of lithium ions in the negative electrode and reducing the concentration polarization generated by the battery cell during fast charging, which is beneficial to improving the fast charging cycle life of the battery cell while taking into account the energy density of the battery cell.

[0161] In some embodiments, the porosity of the isolation membrane is 25%-55%, and optionally 28%-42%.

[0162] In the present application, the porosity of the isolation membrane can be measured by methods known in the art. As an example, the porosity is measured by the gas displacement method in accordance with GB / T24586. Porosity ε = (V1-V2) / V1*100%, where V1 is the apparent volume of the sample and V2 is the real volume of the sample.

[0163] In some embodiments, the porosity of the isolation membrane may be selected to be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 50%, 55% or any range of values ​​therebetween.

[0164] The separator with a porosity within the above range is conducive to improving the liquid phase transmission rate of lithium ions and reducing the liquid phase transmission resistance of lithium ions, thereby reducing the impedance of the battery, reducing the temperature rise of the battery and the phenomenon of inconsistent temperature rise, so that the width of the current collector can be further increased and the energy density can be further increased. At the same time, the reduction in the temperature rise can reduce the degree of side reactions of the electrolyte and the negative electrode active material and reduce gas production. The porosity of the separator within the above range can also make the separator have a certain mechanical strength, while reducing the probability of lithium dendrites piercing the separator and causing a short circuit, and comprehensively improving the fast charging cycle life of the battery cell.

[0165] In some embodiments, the porosity of the isolation membrane is 30%-42%.

[0166] The isolation membrane with a porosity within the above range is conducive to further reducing the temperature rise of the battery and the phenomenon of inconsistent temperature rise, alleviating the technical problems of severe local polarization of the battery and increased risk of lithium plating, and further improving the fast charging cycle life of the battery cell on the basis of maintaining certain mechanical properties of the isolation membrane.

[0167] In some embodiments, the Gurley value G of the isolation film is 50s-620s, and can be optionally 250s-610s.

[0168] In this application, the term "Gurley value" is used to characterize the air permeability of an isolation membrane, which refers to the time required for 100 mL of air to pass through 1 square inch of the isolation membrane under a pressure of 1.22 kPa, with the unit being s.

[0169] In the present application, the Gurley value of the isolation membrane can be tested by any known means. As an example, the isolation membrane is placed in an air permeability tester, and the time required for 100 mL of air to pass through 1 square inch of the isolation membrane under a pressure of 1.22 kPa is the Gurley value. The average value of the test results of multiple (for example, 3) parallel samples can be taken as the Gurley value of the isolation membrane.

[0170] In some embodiments, the Gurley value G of the isolation film can be selected as 50s, 100s, 150s, 200s, 250s, 260s, 270s, 280s, 290s, 300s, 310s, 320s, 330s, 340s, 350s, 360s, 370s, 380s, 390s, 400s, 410s, 420s, 430s, 440s, 450s, 460s, 470s, 480s, 490s, 500s, 510s, 520s, 530s, 540s, 550s, 560s, 570s, 580s, 590s, 600s, 610s, 620s or any numerical range therebetween.

[0171] The separator with a Gurley value within the above range is beneficial to reduce the impedance of the battery cell, reduce the temperature rise of the battery and the phenomenon of inconsistent temperature rise, so that the width of the current collector that the battery can carry is further increased, and the energy density is further increased. At the same time, the reduction in the temperature rise can reduce the degree of side reactions of the electrolyte and the negative electrode active material and reduce gas production. The Gurley value of the separator within the above range can also make the separator have a certain mechanical strength, while reducing the probability of lithium dendrites piercing the separator and causing a short circuit, and comprehensively improve the fast charging cycle life of the battery cell.

[0172] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.

[0173] In some embodiments, Fig. 9 As shown, the battery cell includes a wound battery cell 6, and at least one circle of the positive electrode sheet 101 of the wound battery cell 6 includes at least two positive electrode tabs.

[0174] In some embodiments, the negative electrode plate includes a negative electrode collector and a negative electrode film layer disposed on at least one side of the negative electrode collector, the negative electrode collector includes a negative electrode collecting part and a negative electrode tab 1023 disposed on at least one side of the negative electrode collecting part, and at least one turn of the negative electrode plate of the wound battery cell includes at least two negative electrode tabs.

[0175] The tabs are connected to the battery housing or external module structure, and the current must flow through the tabs to connect to the outside of the battery.

[0176] In some embodiments, the tab extending in the width direction of the current collector means that the tab is located at the end of the battery cell in the height direction.

[0177] In some embodiments, the wound battery cell 6 is as follows Fig. 9 As shown, it is a square wound battery cell.

[0178] In some embodiments, the wound battery cell 6 is a cylindrical wound battery cell.

[0179] Please continue to refer to Fig. 9 Whether in a square wound cell or a cylindrical wound cell, one circle of the positive electrode sheet refers to the winding direction from any point A of the positive electrode sheet, which is free from inside to outside, that is, winding Fig. 9 After winding around the winding needle once in the clockwise direction, it is wound to the point B which is closest to point A in the next circle.

[0180] In some embodiments, at least two, three, four or more consecutive turns of the positive electrode sheet 101 of the wound battery cell 6 each include at least two tabs.

[0181] In the prior art, a positive electrode sheet or a negative electrode sheet in a wound battery cell is usually provided with a pole ear in each winding turn. The embodiment of the present application reduces the overcurrent at the pole ear and the temperature rise at the pole ear by providing at least two pole ears on at least one turn of the wound battery cell pole sheet, thereby alleviating the uneven current density distribution on the pole sheet and the inconsistent temperature rise inside the battery cell during fast charging, thereby improving the fast charging cycle life of the battery cell.

[0182] In some embodiments, the wound battery cell 6 is as follows Fig. 9 As shown, the wound cell 6 includes a large surface area 61 and a bending area 62, and the positive electrode tab 10112 is arranged on the large surface area 61 of the wound cell 6, and the positive electrode tab 10112 is arranged along the winding direction from inside to outside (such as Fig. 9 The number of layers of the positive electrode sheets in the wound battery cell is defined by the rule that the number of positive electrode sheets in the large surface area increases successively (clockwise direction in the figure). The positive electrode sheets of the wound battery cell 6 have at least two consecutive layers, each of which is provided with a positive electrode ear.

[0183] As an example, a layer of the large surface area of ​​the positive electrode sheet 101 is taken as the Nth layer of the positive electrode sheet, and the positive electrode sheet is wound in a direction from inside to outside (eg Fig. 9 The positive electrode sheet 101 passes through the bending area 62 and is wound to the large surface area on the opposite side of the Nth layer. The positive electrode sheet of this layer is recorded as the N+1 layer. The winding direction continues from the inside to the outside. The positive electrode sheet passes through the bending area on the other side and is wound to the N+2 layer on the same side as the Nth layer. This is deduced by analogy to define the number of layers of the positive electrode sheet 101.

[0184] In some embodiments, the positive electrode sheet of the wound battery cell has at least three, four, five, six or more consecutive layers, each of which is provided with a positive electrode tab.

[0185] In the prior art, the pole lugs in the wound battery cell are generally arranged in the Nth layer, the N+2nd layer, the N+4th layer, etc., and at most one pole lug is arranged in every two layers of the pole sheet in the wound battery cell. In the embodiment of the present application, the pole lugs are arranged in each of at least two consecutive layers of the pole sheet, that is, the pole lugs are arranged continuously in the Nth layer and the N+1 layer, so as to reduce the overcurrent at the pole lugs and reduce the temperature rise at the pole lugs, so that the uneven current density distribution on the pole sheet and the inconsistent temperature rise inside the battery cell during the fast charging process are alleviated, thereby improving the fast charging cycle life of the battery cell.

[0186] It can be understood that the tabs in the negative electrode plate can be configured in the same manner as the positive electrode plate.

[0187] In some embodiments, the negative electrode sheet of the wound battery cell has at least two, three, four, five, six or more consecutive layers, each of which is provided with a negative electrode tab.

[0188] In some embodiments, the battery cell comprises a laminated battery core, and the length of the positive electrode current collecting portion in the laminated battery core is 100 mm-700 mm, and can be optionally 200 mm-600 mm.

[0189] In some embodiments, the battery cell comprises a laminated battery cell, and the length of the positive electrode current collecting portion in the laminated battery cell is 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, 700 mm or any range therebetween.

[0190] During the research, the applicant found that the length of the current collector in the laminated battery cell has a key impact on the current uniformity and temperature rise consistency during the fast charging process of the battery cell. The length of the positive current collector in the laminated battery cell within the above range can further improve the phenomenon of inconsistent temperature rise during the fast charging process of the battery cell and improve the fast charging cycle life of the battery cell.

[0191] In some embodiments, the liquid injection coefficient of the battery cell is 2.5 g / Ah-3.1 g / Ah, and can be optionally 2.6 g / Ah-2.9 g / Ah.

[0192] The injection coefficient of a battery cell refers to the ratio of the mass of the electrolyte inside the battery cell to the battery capacity. The injection coefficient of a battery cell can be obtained by any known method in the art. Exemplarily, the battery cell is weighed and the mass is recorded as M0. The battery cell is disassembled and the free electrolyte is poured out; the internal electrode assembly is taken out and the positive electrode sheet, negative electrode sheet, separator and mechanical parts are separated, and the positive electrode sheet, negative electrode sheet, separator and mechanical parts are soaked and cleaned with dimethyl carbonate (DMC) solvent for 24h to 48h, and the soaking time is repeated for more than 3 times. The above-mentioned positive electrode sheet, negative electrode sheet, separator and mechanical parts are placed in a 100°C oven for more than 24h until completely dried. The above-mentioned dried positive electrode sheet, negative electrode sheet, separator and mechanical parts are weighed and the mass is recorded as M1. The mass of the electrolyte in the battery cell is thus obtained as (M0-M1). The injection coefficient is calculated by (M0-M1) / rated capacity of the battery cell. The rated capacity of a battery cell is the nominal capacity of the battery, or it is charged to 3.65V at a 0.33C charge rate, then charged to 0.05C at a 3.65V constant voltage, left to rest for 10 minutes, and then discharged to 2.0V at a 0.33C discharge rate, with the discharge capacity of the battery cell as the rated capacity. It is understandable that in order to improve the accuracy of the injection coefficient test, it is better to use the battery that has just been shipped for testing.

[0193] In some embodiments, the liquid filling coefficient of the battery cell may be 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, 3 g / Ah, 3.1 g / Ah or any range therebetween.

[0194] Battery cells with a liquid filling coefficient within the above range can improve the wettability between the electrolyte and the electrode, reduce the battery interface resistance, and reduce the battery impedance, so that the phenomenon of inconsistent temperature rise in the current collector during fast charging can be alleviated, the width of the battery current collector can be further increased, and at the same time, the increase in gas production caused by the side reaction of the electrolyte solvent can be within a controllable range, further taking into account the battery's fast charging cycle performance, energy density and safety performance.

[0195] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0196] In some embodiments, the negative electrode film layer may also optionally include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0197] In some embodiments, the negative electrode film layer may also optionally include a negative electrode binder. As an example, the negative electrode binder may include, butadiene styrene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) or more.

[0198] In some embodiments, the negative electrode film layer may further include other additives. As an example, the other additives may include but are not limited to thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0199] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, other optional additives, etc. in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0200] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate may also include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate may also include a protective layer covering the surface of the negative electrode film layer.

[0201] In some embodiments, the positive electrode current collector includes a positive electrode active material. The positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds, etc. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), at least one of a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0202] In some embodiments, the positive electrode film layer may also optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include but is not limited to one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0203] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) One or more.

[0204] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, positive electrode conductive agent, positive electrode binder and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0205] In some embodiments, the lithium-containing electrolyte salt may also include, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0206] In some embodiments, the solvent further includes, but is not limited to, one or more of an ester solvent, a sulfone solvent, and an ether solvent. As an example, the solvent may include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0207] In some embodiments, the electrolyte may optionally include other additives.

[0208] A second aspect of the present application provides a battery device, including the battery cell provided by the first aspect of the present application, and the battery device includes at least one of a battery module, a battery pack, and an energy storage battery.

[0209] In addition, the third aspect of the present application further provides an electric device, the electric device comprising the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application. The battery cell, battery module or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0210] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0211] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0212] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a battery cell may be used as a power source.

[0213] Example

[0214] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0215] 1. Preparation method

[0216] Example 1

[0217] (1) Preparation of negative electrode sheet

[0218] The negative electrode active material artificial graphite, thickener sodium carboxymethyl cellulose, negative electrode binder styrene butadiene rubber (SBR), and negative electrode conductive agent Super P are mixed in a mass ratio of 96.9:1.1:1.5:0.5, and deionized water is added as a solvent. The mixture is stirred evenly under the action of a vacuum mixer to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the double-sided surface of the negative electrode current collector copper foil once or multiple times, and the thickness of the copper foil is 4.5μm. After drying, a negative electrode film layer is obtained, and the projection of the positive electrode film layer in the thickness direction falls within the area range of the negative electrode film layer, and along the width direction of the negative electrode current collector, the distance between the edge of the negative electrode film layer and the projection edge of the adjacent positive electrode film layer is 3mm, and the negative electrode sheet is obtained by cold pressing and cutting. The thickness of the negative electrode film layer on one side of the negative electrode current collector is 53μm, and the single side density of the negative electrode film layer is 0.131g / 1540.25mm 2 The compaction density of the negative electrode is 1.6g / cm 3 , the porosity of the negative electrode sheet is 30%.

[0219] (2) Preparation of positive electrode sheet

[0220] The lithium iron phosphate positive electrode material, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were added to the solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and the positive electrode slurry (solid content of 67%) was obtained after being fully stirred and mixed. Then, the positive electrode slurry was evenly coated on the double-side surface of the positive electrode current collector aluminum foil, wherein the thickness of the aluminum foil was 13 μm, and the single-side coating weight was about 350 mg / 1540.25 mm 2 After drying, the positive electrode film layer is obtained. Along the width direction of the positive electrode current collector, the size of the positive electrode film layer is 84 mm. The pole ears are cut out on the aluminum foil by cold pressing, and the width of the current collector is 87 mm to obtain the positive electrode sheet.

[0221] (3) Preparation of electrolyte

[0222] In an argon atmosphere glove box (H 2 O<0.1ppm, O 2 <0.1ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and methyl acetate are mixed uniformly in a mass ratio of 3:2:5, and then additives are added. The additives include vinylene carbonate VC, fluoroethylene carbonate FEC, lithium difluorooxalatoborate LiDFOB and 1,3-propyl sultone PS. Based on the total mass of the electrolyte, the mass proportion of VC is 2%, the mass proportion of FEC is 1%, the mass proportion of LiDFOB is 0.5%, and the mass proportion of PS is 1%.

[0223] After mixing well, add lithium hexafluorophosphate (LiPF 6) and LiFSI, so that they are dissolved in an organic solvent, based on the total mass of the electrolyte, LiPF 6 The mass proportion of is 9%, and the mass proportion of LiFSI is 5%. The two are stirred evenly to obtain an electrolyte.

[0224] (4) Preparation of isolation membrane

[0225] A conventional commercially available polyethylene film is used as the separator, and a ceramic coating is provided on the surface of the separator facing the positive electrode. The ceramic coating contains Al 2 O 3 and PVDF adhesive, the porosity of the isolation membrane is 36%, and the Gurley value of the isolation membrane is 601s.

[0226] (5) Preparation of battery cells

[0227] The positive electrode sheet (collecting part width 87mm, length 270mm), the separator (width 98mm), and the negative electrode sheet (collecting part width 90mm) are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a battery cell, so that each layer of the positive electrode sheet and the negative electrode sheet in the wound battery cell is provided with a pole ear.

[0228] The battery cell is placed in a battery casing, and after drying, the electrolyte is injected, and then the lithium-ion battery is manufactured through processes such as formation and standing.

[0229] The capacity of the prepared lithium-ion battery and the quality of the electrolyte were tested, and the battery filling coefficient was calculated to be 3.0 g / Ah.

[0230] The preparation method of Example 2-11 is basically the same as that of Example 1, except that the corresponding parameters of the battery cells are adjusted, as shown in Table 1.

[0231] In Example 2, the width of the positive electrode current collector is 63 mm, the width of the positive electrode film layer is 60 mm, the width of the negative electrode current collector is 63 mm, and the width of the negative electrode film layer is 63 mm.

[0232] In Example 3, the width of the positive electrode current collector is 97 mm, the width of the positive electrode film layer is 94 mm, the width of the negative electrode current collector is 97 mm, and the width of the negative electrode film layer is 97 mm.

[0233] The solvent of the electrolyte in Example 4 is ethylene carbonate (EC), ethyl methyl carbonate (EMC) and ethyl acetate, and the mass ratio of the solvents is 3:2:5.

[0234] The solvent of the electrolyte in Example 5 is ethylene carbonate (EC), ethyl methyl carbonate (EMC) and methyl acetate, and the mass ratio is 3:6:1.

[0235] The solvent of the electrolyte in Example 6 is ethylene carbonate (EC) and methyl acetate, and the mass ratio is 24:76.

[0236] In Example 7, the electrolyte salt content in the electrolyte was adjusted so that the mass content of LIFSI was 1% based on the total mass of the electrolyte, and the mass content of LiPF 6 The quality accounts for 13%.

[0237] In Example 8, the electrolyte salt content in the electrolyte was adjusted so that the mass content of LIFSI was 8% and the mass content of LiPF was 1.8% based on the total mass of the electrolyte. 6 The mass share is 6%.

[0238] In Example 9, the number of pole tabs is adjusted so that one pole tab is provided for every two layers of the positive electrode sheets and the negative electrode sheets in the wound battery cell.

[0239] In Example 10, the thickness of the aluminum foil in the positive electrode current collector was adjusted, and the thickness of the aluminum foil was 10 μm.

[0240] In Example 11, the porosity of the separator was adjusted, and the porosity of the separator was 28%.

[0241] The preparation method of Comparative Example 1 is substantially the same as that of Example 9, except that no methyl acetate solvent is added to the electrolyte.

[0242] The preparation method of Comparative Example 2 is basically the same as that of Example 9, except that the corresponding parameters of the battery cell are adjusted, the width of the positive electrode current collector is 110 mm, the length is 270 mm, the width of the positive electrode film layer is 107 mm, the width of the negative electrode current collector is 110 mm, and the width of the negative electrode film layer is 110 mm.

[0243] 2. Performance Test

[0244] 1) Battery fast charge temperature rise and fast charge cycle life test

[0245] First, the fast charging window must be obtained: the batteries of the above embodiments and comparative examples are charged and discharged for the first time at a current of 1C (i.e., the current value that completely discharges the theoretical capacity within 1 hour), specifically including: at 35°C, the battery is charged at a constant current rate of 1C to a voltage of 3.65V, then charged at a constant voltage to a current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a voltage of 2.5V, and its actual capacity is recorded as C0. Then the battery is charged with constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, 5C0 in sequence to the full battery charge cut-off voltage of 3.65V or 0V negative electrode cut-off potential (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to the full battery discharge cut-off voltage of 2.1V. Record the SOC (State of Charge) at different charge rates to 10%, 20%, 30%, ..., 80% Charge, state of charge, when "SOC = 0" indicates that the battery is fully discharged, when "SOC = 100%" indicates that the battery is fully charged) the corresponding negative electrode potential, draw the charging rate-negative electrode potential curve under different SOC states, and obtain the charging rate corresponding to the negative electrode potential of 0V under different SOC states after linear fitting. The charging rate is the charging window under the SOC state, which are recorded as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), and C(80% SOC) respectively, and the maximum charging rate under the corresponding charge state, that is, the fast charging window, is obtained.

[0246] At 25°C, the obtained fast charging window distribution was used for charging, and C (10% SOC) was charged to 10% SOC, C (20% SOC) was charged to 20% SOC, C (30% SOC) was charged to 30% SOC, C (40% SOC) was charged to 40% SOC, C (50% SOC) was charged to 50% SOC, C (60% SOC) was charged to 60% SOC, C (70% SOC) was charged to 70% SOC, and C (80% SOC) was charged to 80% SOC. 0.33C was charged to 100% SOC. After standing for 10 minutes, it was charged to 2.1V with 0.33C DC. The discharge capacity at this time was recorded as C1. The temperature rise at the pole ear during this charging process was monitored. The above process was repeated, and the discharge capacity of each cycle was recorded as Cn. The cycle capacity retention rate = Cn / C1. The number of cycles when the cycle capacity retention rate dropped to 80% SOH was recorded.

[0247] 2) Battery hot box safety test

[0248] The battery cell is fully charged to the corresponding design upper limit voltage of 3.65V, and the battery cell is equipped with a clamp. The mass m1 of the battery cell at this time is recorded. The battery cell is placed in an incubator. The incubator starts to heat up from room temperature, and the temperature is increased at 2℃ / min to 100℃, and maintained for 1 hour. Then the temperature is increased at 5℃ / min, and maintained for 30 minutes every 5℃ until the battery cell fails (smoke or fire occurs when the valve is opened). The test is stopped, and the battery cell mass m2 is recorded at room temperature. 1-(m2 / m1) is the weight loss rate of the battery cell. The higher the weight loss rate of the battery cell, the more side reaction products that are easy to spray in the battery cell, and the worse the safety performance.

[0249] Table 1

[0250]

[0251]

[0252] From the comparison between the embodiment and the comparative example, it can be seen that the width of the positive electrode current collector in the battery cell is 62mm-98mm, and the lithium ion conductivity of the electrolyte is 10mS / cm-25mS / cm, which is beneficial to improving the fast charging cycle life of the battery while maintaining a good energy density of the battery.

[0253] Table 2

[0254]

[0255] From the comparison of Examples 1 and 4-6, it can be seen that when the mass content of the chain carboxylic acid ester solvent is 7%-60% based on the total mass of the electrolyte, the battery monomer has a lower gas production level and higher safety performance while taking into account energy density and fast charging cycle life.

[0256] Table 3

[0257]

[0258] From the comparison of Examples 1 and 7-8, it can be seen that when the mass proportion of lithium bis(fluorosulfonyl)imide LiFSI is 3%-6% based on the total mass of the electrolyte, the battery monomer can better balance the fast charging cycle life and low gas production level while maintaining good energy density, thereby achieving a balance between fast charging life and safety performance.

[0259] Table 4

[0260] Aluminum foil thickness μm Fast charge cycle life Example 1 13 2850 Example 10 10 2790

[0261] From the comparison between Examples 1 and 10, it can be seen that when the thickness of the aluminum foil is 12 μm-14 μm, the fast charging cycle life of the battery cell can be further improved while maintaining a certain energy density.

[0262] Table 5

[0263] Separator membrane porosity Fast charge cycle life Example 1 36％ 2850 Embodiment 11 28％ 2620

[0264] From the comparison between Examples 1 and 11, it can be seen that when the porosity of the isolation membrane is 30%-42%, the battery cell can further improve the fast charging cycle life while maintaining high safety.

[0265] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises a wound cell, wherein the wound cell comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator disposed between the positive electrode sheet and the negative electrode sheet; The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side of the surface of the positive electrode current collector, the positive electrode current collector comprises a positive electrode current collecting portion and a positive electrode tab disposed on at least one side of the side of the positive electrode current collecting portion, and at least one circle of the positive electrode sheet comprises at least two positive electrode tabs; The electrolyte comprises a solvent and an electrolyte salt, the solvent comprises a chain carboxylate solvent, and the mass proportion of the chain carboxylate solvent is greater than or equal to 5% based on the total mass of the electrolyte; The lithium ion conductivity of the electrolyte is 10mS / cm-25mS / cm.

2. The battery cell according to claim 1, characterized in that: The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode current collector includes a negative electrode current collecting part and a negative electrode tab arranged on at least one side of the negative electrode current collecting part, and at least one circle of the negative electrode plate includes at least two negative electrode tabs.

3. The battery cell according to claim 1 or 2, characterized in that: The wound battery cell includes a large surface area and a bending area, and the positive electrode lug is arranged in the large surface area of ​​the wound battery cell. The number of layers of the positive electrode sheets in the wound battery cell is defined by the rule that the number of positive electrode sheets in the large surface area increases successively along the winding direction from the inside to the outside. The positive electrode sheets of the wound battery cell have at least two consecutive layers, each of which is provided with a positive electrode lug.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The lithium ion conductivity of the electrolyte is 12mS / cm-20mS / cm.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The lithium ion conductivity of the electrolyte is 14mS / cm-20mS / cm.

6. The battery cell according to any one of claims 1 to 5, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the chain carboxylic acid ester solvent is 7%-75%.

7. The battery cell according to any one of claims 1 to 6, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the chain carboxylic acid ester solvent is 7%-60%.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The electrolyte salt includes lithium bis(fluorosulfonyl)imide, and based on the total mass of the electrolyte salt in the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide is 5%-60%.

9. The battery cell according to claim 8, characterized in that: Based on the total mass of the electrolyte salt in the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide is 10%-50%.

10. The battery cell according to claim 8 or 9, characterized in that: Based on the total mass of the electrolyte salt in the electrolyte, the mass proportion of lithium bis(fluorosulfonyl)imide is 25%-50%.

11. The battery cell according to any one of claims 8 to 10, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 1%-10%.

12. The battery cell according to any one of claims 8 to 11, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 1%-8%.

13. The battery cell according to any one of claims 8 to 12, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 3%-6%.

14. The battery cell according to any one of claims 8 to 13, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 4%-6%.

15. The battery cell according to any one of claims 1 to 14, characterized in that: The chain carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate.

16. The battery cell according to claim 1, characterized in that: The chain carboxylic acid ester solvent includes one or more of ethyl acetate and methyl acetate. Based on the total mass of the solvent, the total mass of ethyl acetate and methyl acetate accounts for 5%-80%.

17. The battery cell according to claim 1, characterized in that: The chain carboxylic acid ester solvent includes methyl acetate, and the mass content of methyl acetate is 5%-80% based on the total mass of the solvent.

18. The battery cell according to claim 17, characterized in that: Based on the total mass of the solvent, the mass content of methyl acetate is 5%-50%.

19. The battery cell according to any one of claims 1 to 18, characterized in that: The width of the positive electrode current collecting portion is 62 mm-98 mm.

20. The battery cell according to any one of claims 1 to 19, characterized in that: Along the width direction of the positive electrode current collecting portion, the size of the positive electrode film layer is 60mm-97mm.

21. The battery cell according to claim 20, characterized in that: Along the width direction of the positive electrode current collecting portion, the size of the positive electrode film layer is 63mm-90mm.

22. The battery cell according to any one of claims 1 to 21, characterized in that: The positive electrode current collector comprises aluminum foil, and the thickness of the aluminum foil is 10 μm-16 μm.

23. The battery cell according to claim 22, characterized in that: The thickness of the aluminum foil is 12 μm-14 μm.

24. The battery cell according to any one of claims 1 to 23, characterized in that: The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes lithium iron phosphate and a modified material thereof.

25. The battery cell according to any one of claims 1 to 24, characterized in that: The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the projection of the positive electrode film layer along the thickness direction falls within the range of the negative electrode film layer, and along the width direction of the negative electrode current collector, the distance between the edge of the negative electrode film layer and the projected edge of the adjacent positive electrode film layer is 1mm-4mm.

26. The battery cell according to claim 2, characterized in that: The negative electrode current collector includes copper foil, and the thickness of the copper foil is 4 μm-6 μm.

27. The battery cell according to claim 2, characterized in that: The single side density of the negative electrode film layer is 0.08g / 1540.25mm 2 -0.20g / 1540.25mm 2 .

28. The battery cell according to claim 27, characterized in that: The single side density of the negative electrode film layer is 0.10g / 1540.25mm 2 -0.16g / 1540.25mm 2 .

29. The battery cell according to any one of claims 1 to 28, characterized in that: The compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.9g / cm 3 .

30. The battery cell according to any one of claims 1 to 29, characterized in that: The compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.65g / cm 3 .

31. The battery cell according to any one of claims 1 to 30, characterized in that: The compaction density of the negative electrode sheet is 1.3 g / cm 3 -1.65g / cm 3 .

32. The battery cell according to any one of claims 1 to 31, characterized in that: The compaction density of the negative electrode plate is 1.4 g / cm 3 -1.6g / cm 3 .

33. The battery cell according to claim 2, characterized in that: The average thickness of one side of the negative electrode film layer is 30 μm-150 μm.

34. The battery cell according to claim 33, characterized in that: The average thickness of one side of the negative electrode film layer is 30 μm-80 μm.

35. The battery cell according to any one of claims 1 to 34, characterized in that: The porosity of the negative electrode plate is 20%-60%.

36. The battery cell according to any one of claims 1 to 35, characterized in that: The porosity of the negative electrode plate is 25%-40%.

37. The battery cell according to any one of claims 1 to 36, characterized in that: The porosity of the isolation film is 25%-55%.

38. The battery cell according to any one of claims 1 to 37, characterized in that: The porosity of the isolation membrane is 28%-42%.

39. The battery cell according to any one of claims 1 to 38, characterized in that: The porosity of the isolation film is 30%-42%.

40. The battery cell according to any one of claims 1 to 39, characterized in that: The Gurley value G of the isolation membrane is 50s-620s, and the Gurley value refers to the time required for 100 mL of air to pass through 1 square inch of the isolation membrane under a pressure of 1.22 kPa when the isolation membrane is placed in an air permeability tester, and the unit is s.

41. The battery cell according to claim 40, characterized in that The Gurley value G of the isolation film is 250s-610s.

42. The battery cell according to any one of claims 1 to 41, characterized in that: The liquid injection coefficient of the battery monomer is 2.5g / Ah-3.1g / Ah.

43. The battery cell according to any one of claims 1 to 42, characterized in that: The liquid injection coefficient of the battery monomer is 2.6g / Ah-2.9g / Ah.

44. A battery device, characterized in that: Comprising the battery monomer described in any one of claims 1 to 43, the battery device comprises at least one of a battery module, a battery pack, and an energy storage battery.

45. An electrical device, characterized in that: A battery cell comprising any one of claims 1 to 43 or a battery device according to claim 44.

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