Battery cell, battery device, and electric device

Abstract

The invention provides a single battery, a battery device and a power utilization device, the single battery comprises an electrode assembly, the total width of a positive pole lug part accounts for 50%-100% of the total size of a pole lug connecting edge along the extension direction of the pole lug connecting edge of a positive pole main body part, and the total width of a negative pole lug part accounts for 50%-100% of the total size of the pole lug connecting edge along the extension direction of the pole lug connecting edge of a negative pole main body part; wherein the coating weight of the single negative electrode active material layer is 0.1 g / 1540.25 mm < 2 >-0.145 g / 1540.25 mm < 2 >, the electrolyte comprises at least one of dimethyl carbonate and linear carboxylic ester, the structural formula of the linear carboxylic ester meets R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl respectively; based on the total mass of the organic solvent, the mass fraction of the first solvent is 4-72%.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority benefit of the PCT patent application with application number PCT / CN2024 / 107376 filed on July 24, 2024, and incorporates all of it herein by reference. Technical field

[0003] This application relates to the field of battery technology, and specifically, to battery cells, battery devices, and power - consuming devices. Background art

[0004] Lithium - ion battery cells have been widely used in energy - storage power - supply systems such as hydraulic, thermal, wind, and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles, and electric vehicles. With the gradual expansion of the application scope of battery cells, the market has put forward higher requirements for battery performance. However, there are still many deficiencies in the current batteries during application, and the fast - charging performance needs to be further improved.

[0005] It should be noted that the above statements are only used to provide background - technology information related to this application and do not necessarily constitute prior art. Summary of the invention

[0006] In the first aspect of this application, a battery cell is proposed, including: an electrode assembly, the electrode assembly includes a positive - electrode sheet, a negative - electrode sheet, and a separator located between the positive - electrode sheet and the negative - electrode sheet. Among them, the positive - electrode sheet includes a positive - electrode current collector and a positive - electrode active - material layer located on at least one side of the positive - electrode current collector. The positive - electrode current collector includes a positive - electrode main body part and at least one positive - electrode tab. The tab - connecting edge of the positive - electrode main body part is connected to the positive - electrode tab. Along the direction of extension of the tab - connecting edge, the total width of the positive - electrode tab accounts for 50% - 100% of the total size of the tab - connecting edge of the positive - electrode main body part. The negative - electrode sheet includes a negative - electrode current collector and a negative - electrode active - material layer located on at least one side of the negative - electrode current collector. The negative - electrode current collector includes a negative - electrode main body part and at least one negative - electrode tab. The tab - connecting edge of the negative - electrode main body part is connected to the negative - electrode tab. Along the direction of extension of the tab - connecting edge, the total width of the negative - electrode tab accounts for 50% - 100% of the total size of the tab - connecting edge of the negative - electrode main body part. Among them, the coating weight of a single layer of the negative - electrode active - material layer is 0.1 g / 1540.25 mm 2 - 0.145 g / 1540.25 mm 2 , an electrolyte, the electrolyte includes an organic solvent, the organic solvent includes a first solvent, the first solvent includes at least one of dimethyl carbonate and linear carboxylic acid ester. Among them, the structural formula of the linear carboxylic acid ester satisfies R 1-COO-R 2 ,R 1 、R 2 are each independently selected from C 1 -C 5 alkyl or haloalkyl; based on the total mass of the electrolyte, the mass fraction of the first solvent is 4% - 72%. Thus, the fast charging performance of the battery cell can be effectively improved, and the performance of the battery cell under fast charging conditions can be enhanced.

[0007] In some embodiments, the total width of the positive electrode tab is 40 mm - 160 mm; and / or, the total width of the negative electrode tab is 40 mm - 160 mm; and / or, the width of the positive electrode tab is 40 mm - 160 mm; and / or, the width of the negative electrode tab is 40 mm - 160 mm. Thus, the current-carrying area of the positive electrode tab and the negative electrode tab is relatively large, and the heat dissipation ability is relatively excellent.

[0008] In some embodiments, the positive electrode tab and the negative electrode tab are located on the same side of the positive electrode main body, or, the positive electrode tab and the negative electrode tab are located on opposite sides of the positive electrode main body. Thus, the connection of the external circuit can be simplified, and the assembly process can be simplified.

[0009] In some embodiments, the positive electrode current collector includes the positive electrode main body and a plurality of the positive electrode tabs, and at least two of the positive electrode tabs are located on opposite sides of the positive electrode main body; and / or, the negative electrode current collector includes the negative electrode main body and a plurality of the negative electrode tabs, and at least two of the negative electrode tabs are located on opposite sides of the negative electrode main body. Thus, a more uniform heat distribution can be provided, and the tab deformation caused by excessive force on one side can be reduced.

[0010] In some embodiments, the positive electrode current collector includes the positive electrode main body and a plurality of the positive electrode tabs arranged at intervals; and / or, the negative electrode current collector includes the negative electrode main body and a plurality of the negative electrode tabs arranged at intervals. Thus, the electron transmission path can be shortened, and the heat generation of the battery can be reduced.

[0011] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135 g / 1540.25 mm 2 . Thus, the battery cell has a relatively high volumetric energy density.

[0012] In some embodiments, the time for the battery to be charged from 10% SOC to 80% SOC is 7 min - 15 min. Thus, the battery cell has relatively excellent fast charging performance.

[0013] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 - 0.145 g / 1540.25 mm 2 Thus, the battery cell has a high volumetric energy density.

[0014] In some embodiments, the time for the battery to be charged from 10% SOC to 80% SOC is 20 min - 30 min. Thus, the battery cell has excellent fast charging performance.

[0015] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer at least on one side of the negative electrode current collector, and the tap density of the negative electrode active material layer is 1.2 g / cm3 - 1.5 g / cm 3 Thus, it helps to improve the fast charging performance of the battery cell.

[0016] In some embodiments, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the negative electrode active material is 0.1% - 7%. Thus, the mass energy density of the battery cell can be improved.

[0017] In some embodiments, the mass fraction of silicon in the negative electrode active material is 1% - 5%. Thus, the mass energy density of the battery cell can be further improved.

[0018] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer stacked, the first negative electrode active material layer is located on the side close to the negative electrode current collector, the Dv50 of the first negative electrode active material in the first negative electrode active material layer is 9.2 μm - 18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2 μm - 15.5 μm. Thus, the fast charging performance and energy density of the battery cell can be significantly improved.

[0019] In some embodiments, the conductivity of the electrolyte is 10 ms / cm - 20 ms / cm. Thus, it helps to improve the fast charging performance of the battery cell.

[0020] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the first solvent is 16% - 72%. Thus, the fast charging performance of the battery cell can be improved.

[0021] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the linear carboxylic acid ester is 32% - 68%. Thus, the viscosity of the electrolyte can be effectively reduced, and the fast charging performance of the battery can be improved.

[0022] In some embodiments, the electrolyte further includes a first lithium salt additive, the first lithium salt additive includes at least one of a fluoroborate and a fluorophosphate, and based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.05% - 0.5%. Thereby, the internal resistance of the battery cell can be effectively reduced.

[0023] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalate phosphate, lithium difluorooxalate borate, and lithium tetrafluoroborate. Thereby, it helps to form a solid electrolyte film with low impedance on the surface of the negative electrode active material.

[0024] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.1% - 0.3%. Thereby, it helps to reduce the cost of the battery cell.

[0025] In some embodiments, the organic solvent further includes a second solvent, the second solvent includes at least one of ethylene carbonate, vinylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate. Thereby, it helps to improve the cycle life of the battery cell.

[0026] In some embodiments, the second solvent includes diethyl carbonate, and based on the total mass of the electrolyte, the content of diethyl carbonate is not less than 12%.

[0027] In some embodiments, the electrolyte further includes a non-lithium salt additive, the non-lithium salt additive includes at least one of vinylene carbonate, fluorinated vinylene carbonate, and ethylene vinylene carbonate. Thereby, it helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0028] In some embodiments, the carbonate additive includes at least one of vinylene carbonate (VC), fluorinated vinylene carbonate (FEC), and ethylene vinylene carbonate. Thereby, it helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0029] In some embodiments, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate is 0.5% - 2.5%, and / or the mass fraction of fluorinated vinylene carbonate is 0.05% - 2%. Thereby, it helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0030] In some embodiments, the sulfate additive includes at least one of 4,4-vinyl sulfone, bis(vinylsulfonyl)methane, cyclic tris(vinylsulfonyl)methane, and 1,3-propane sultone.

[0031] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the non-lithium salt additive is 0.05% - 3%. Thereby, it helps to reduce the cost of the battery cell.

[0032] In some embodiments, the electrolyte further includes a second lithium salt additive, and the second lithium salt additive includes at least one of lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, lithium tetrafluorobis(oxalato)phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate. Thereby, it helps to form a solid electrolyte film with relatively high ionic conductivity on the surface of the negative electrode active material.

[0033] In some embodiments, the electrolyte further includes an electrolyte lithium salt, and the electrolyte lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte, the mass fraction of the electrolyte lithium salt is greater than or equal to 13%. Thereby, it helps to improve the conductivity of the electrolyte.

[0034] In some embodiments, the electrolyte lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide in the electrolyte is (1.2 - 2):1. Thereby, it helps to further improve the conductivity of the electrolyte.

[0035] In some embodiments, the tap density of the positive electrode active material layer is 2.2 g / cm 3 - 2.6 g / cm 3 . Thereby, it helps to improve the fast charging performance and energy density of the battery cell.

[0036] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes: a core portion, the core portion includes a lithium-containing phosphate with an olivine structure, and a coating layer, the coating layer covers the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn. Thereby, it helps to improve the structural stability and ionic conductivity of the positive electrode active material.

[0037] In some embodiments, the lithium-containing phosphate with an olivine structure includes a general formula of Li x1 A y1 Me a M1 b P 1-c X c Y zCompounds, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3; 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5; 0 ≤ c ≤ 0.5; 3 ≤ z ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M1 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F. Thus, it helps to improve the ionic conductivity and electronic conductivity of the core part.

[0038] In some embodiments, the coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15 - 0.32. Thus, it helps to improve the electronic conductivity of the positive electrode active material.

[0039] In some embodiments, in the cross-section of the positive electrode active material layer in the thickness direction, the positive electrode active material includes lithium-containing phosphate with an olivine structure having a longest diameter of 1 μm - 3 μm and lithium-containing phosphate with an olivine structure having a shortest diameter of 0.1 μm - 0.3 μm. Thus, it is beneficial to improve the energy density of the battery cell.

[0040] In some embodiments, the positive electrode active material satisfies at least one of the following conditions: the Dv50 particle size of the positive electrode active material is 1 μm - 5 μm; the Dv10 particle size of the positive electrode active material is 0.4 μm - 0.7 μm; the positive electrode active material is primary particles or quasi-single crystal particles. Thus, the relatively large particle size of the positive electrode active material is beneficial to improve the energy density of the battery cell.

[0041] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, and the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, lithium nickel copperate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, trilithium citrate, and lithium nickel cobalt manganate. Thus, it helps to improve the cycle life of the battery cell.

[0042] In some embodiments, the length of the battery cell is L and the width of the battery cell is H, and the value of L is 4 to 10 times the value of H. Thus, the volume utilization rate of the battery can be effectively improved, and the overall energy density of the battery can be increased.

[0043] In some embodiments, the value of L is 4 to 7 times the value of H. Thus, it helps the battery cell to have both a relatively high energy density and a relatively low internal resistance.

[0044] In some embodiments, L is 400 mm-1000 mm, and / or H is 80 mm-160 mm.

[0045] In some embodiments, a shell is further included, the electrode assembly is located in the shell, the shell includes two first shell walls arranged opposite to each other, and a surrounding wall connecting the two first shell walls, the surrounding wall includes: two second shell walls arranged opposite to each other along the length direction of the first shell wall, and two third shell walls arranged opposite to each other along the width direction of the first shell wall, the second shell wall is provided with an electrode terminal, the positive pole ear and the negative pole ear are electrically connected to the electrode terminals on the two second shell walls respectively, wherein a folding structure is provided between the second shell wall electrically connected to the positive pole ear and the positive main body, and the folding structure is configured to fold a plurality of the positive pole ears. Thus, the fixation of the positive pole ear and the welding between the positive pole sheet and the pole column are facilitated.

[0046] In some embodiments, the edge of the positive electrode sheet is chamfered in the length direction of the first shell wall, thereby facilitating the rapid assembly of the electrode assembly.

[0047] In some embodiments, a liquid injection hole is provided on the second shell wall connected to the negative electrode ear portion, thereby facilitating the injection of electrolyte.

[0048] In some embodiments, the injection hole and the pressure relief portion of the shell are located on different second shell walls, and the pressure relief portion is configured to release the pressure inside the shell, thereby reducing the corrosion of the pressure relief portion by the electrolyte during the injection process.

[0049] In some embodiments, the electrode terminal is provided with at least one mounting hole, and the pole is passed through the mounting hole and riveted to the pole ear portion, thereby helping to reduce the volume of the battery cell, reduce the weight of the battery cell, and improve the energy density of the battery cell.

[0050] In some embodiments, the electrode terminal is provided with at least two mounting holes, and each pole is passed through the mounting holes and riveted to the pole ear portion, thereby helping to improve the current carrying capacity of the pole.

[0051] In some embodiments, the diameter of the pole is 3 mm to 8 mm. Thus, the pole has both high current capacity and low space occupation.

[0052] In some embodiments, the pole columns riveted to the positive electrode tab and the pole columns riveted to the negative electrode tab are arranged in a staggered manner in the length direction of the first housing wall. Optionally, the pole columns riveted to the positive electrode tab and the pole columns riveted to the negative electrode tab are arranged diagonally in the length direction of the first housing wall. Thus, it helps to improve the volume energy density of the assembled battery module or battery pack.

[0053] In some embodiments, the pole column and the pole ear are electrically connected through a connecting piece. Thus, the welding quality and connection reliability between the pole column and the pole ear can be significantly improved.

[0054] In some embodiments, the pole column and the pole ear are directly electrically connected. Thus, it helps to reduce the structural complexity inside the battery cell, helps to reduce the volume of the battery cell, and improve the energy density.

[0055] In some embodiments, the distance between the two first housing walls is D, and D is less than or equal to 30 mm. Thus, it is beneficial to the rapid heat dissipation of the battery cell.

[0056] In some embodiments, D is 10 mm - 25 mm. Thus, the battery cell has high mechanical strength and excellent heat dissipation ability.

[0057] In some embodiments, the thicknesses of the first housing wall and the third housing wall are each independently less than or equal to 0.5 mm. Thus, the volume energy density of the battery cell can be improved.

[0058] In some embodiments, the first housing wall and the third housing wall include at least one of an aluminum shell and a steel shell. Thus, the mechanical strength of the battery cell can be improved.

[0059] In some embodiments, the first housing wall and the third housing wall are steel shells, and the wall thickness of the steel shell is 0.1 mm - 0.5 mm. Thus, the volume expansion of the battery cell during charge and discharge can be effectively alleviated.

[0060] In some embodiments, the first housing wall and the third housing wall are aluminum shells, and the wall thickness of the aluminum shell is 0.3 mm - 0.4 mm. Thus, the mass energy density of the battery cell can be effectively improved.

[0061] In some embodiments, the first housing wall and the third housing wall are obtained by bending and welding aluminum plates, and the weld of the welding is located at the connection of the first housing wall and the third housing wall. Thus, the leakage of the electrolyte can be reduced.

[0062] In some embodiments, a side support plate is provided between the electrode assembly and the first housing wall. Thus, it helps to improve the structural stability of the battery cell.

[0063] In some embodiments, at least one of the second housing walls is provided with a pressure relief portion configured to be able to relieve the pressure inside the housing, and the area of the orthographic projection of the pressure relief portion on the second housing wall is 7%-15% of the area of the second housing wall. Thus, it helps to quickly release the internal overpressure gas through the pressure relief portion when the pressure inside the battery cell is too high.

[0064] In some embodiments, the capacity of the battery is Q, and the ratio of the area of the orthographic projection of the pressure relief portion on the second housing wall to Q is greater than or equal to 1.1. The unit of Q is Ah, and the unit of the area is mm 2 . Thus, it helps to quickly release the internal overpressure gas in the battery cell.

[0065] In a second aspect of the present application, a battery device is provided, including the aforementioned battery cell, and the battery device includes at least one of a battery module, a battery pack, and an energy storage device. Thus, the battery device has all the features and advantages of the aforementioned battery cell, which will not be elaborated herein.

[0066] In a third aspect of the present application, an electrical device is provided, including the aforementioned battery cell. Thus, the electrical device has all the features and advantages of the aforementioned battery cell, which will not be elaborated herein. Description of the Drawings

[0067] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where: Figure 1 is a schematic structural diagram of an electrode assembly prepared by a lamination process according to an embodiment of the present application; Figure 2 is a schematic structural diagram of a positive current collector according to an embodiment of the present application; Figure 3 is a schematic structural diagram of a positive current collector according to another embodiment of the present application; Figure 4 is a schematic structural diagram of a positive current collector according to another embodiment of the present application; Figure 5 is a schematic structural diagram of a positive current collector according to another embodiment of the present application; Figure 6 is a schematic structural diagram of an electrode assembly prepared by a winding process according to an embodiment of the present application; Figure 7 is a schematic structural diagram of a battery cell according to an embodiment of the present application; Figure 8 is a partial structural schematic diagram of a housing according to an embodiment of the present application; Figure 9A partial structural schematic diagram of a housing according to another embodiment of the present application; Figure 10 A partial structural schematic diagram of a housing according to another embodiment of the present application; Figure 11 A partial structural schematic diagram of a housing according to another embodiment of the present application; Figure 12 A partial structural schematic diagram of a housing according to another embodiment of the present application; Figure 13 A partial structural schematic diagram of a housing according to another embodiment of the present application; Figure 14 A partial structural schematic diagram of a housing according to another embodiment of the present application; Figure 15 This is a schematic diagram of the structure of an electrical device according to an embodiment of the present application.

[0068] Description of reference numerals: 11 positive electrode main body; 12 positive electrode ear; 21 negative electrode main body; 22 negative electrode ear; 101 first shell wall; 102 second shell wall; 103 third shell wall; 104 pressure relief portion; 105 pole; 106 folding structure; 107 injection hole; 108 adapter plate. DETAILED DESCRIPTION

[0069] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description 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.

[0070] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0071] The terms "including" and "having" in the specification and claims of the present application and any modifications thereof are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0072] In the description of the present application, all the numbers disclosed herein are approximate values, whether or not the words "about" or "approximately" are used. The numerical value of each number may have a difference of less than 10% or a reasonable difference considered by those skilled in the art, such as a difference of 1%, 2%, 3%, 4% or 5%.

[0073] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4 and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0074] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0075] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. The "first feature" and "second feature" may include one or more of such features.

[0076] In the description of the present application, the meaning of "a plurality of" is two or more.

[0077] In the description of the present application, "A and / or B" may include the case of A alone, the case of B alone, or any one of the cases of A and B, where A and B are only for example and may be any technical features connected by "and / or" in the present application.

[0078] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0079] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0080] By improving the fast charging performance of the battery, users can replenish a large amount of power for the device in a short time, reduce the charging waiting time, and improve the overall user experience. However, during fast charging, the chemical reaction rate inside the battery cell accelerates, resulting in more heat generated by the battery. A continuous high-temperature environment will accelerate the aging of battery materials, especially the decomposition of the electrolyte and the degradation of the positive electrode active material, thereby shortening the battery cycle life. At the same time, the current flowing through the tab during fast charging is also relatively large, which also places high requirements on the maximum current that the tab can carry.

[0081] When the coating weight of the single-layer negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2When the coating weight of the single-layer negative electrode active material layer is high, and the thickness of the negative electrode active material layer on the surface of the negative electrode current collector is moderate and the uniformity is high, the transmission path of lithium ions in the negative electrode active material layer is short, and they can be quickly inserted into and extracted from the negative electrode active material during charge and discharge. At the same time, the battery cell has a high energy density and is suitable for battery cells with high requirements for fast charging performance. Further, by adopting ear portions with a total width accounting for 50%-100% of the total size of the ear connection edges of the corresponding main portions in the positive electrode current collector and the negative electrode current collector, the current conduction paths on the ears can be effectively increased. Thus, when the battery is rapidly charged and discharged, a higher current can pass through the ear portions, meeting the performance requirements for the current-carrying capacity of the ear portions under fast charging conditions. Meanwhile, the larger cross-sectional area of the ear portions can reduce their resistance, thereby reducing the heat generation at the roots of the ear portions. Therefore, the ear portions that meet the above requirements can withstand a larger current while reducing the generation and accumulation of heat inside the battery cell and providing a larger surface area for heat dissipation, thus enhancing the heat dissipation effect of the ear portions and helping the battery cell maintain a relatively low system temperature during fast charging. Furthermore, due to its low viscosity, the first solvent has a high conductivity, which can effectively reduce the internal resistance of the battery cell. However, it also has the characteristic of a low boiling point. When the above-mentioned battery cell can maintain a relatively low system temperature under fast charging conditions, the heat loss of the first solvent caused by the high temperature rise of the battery cell can be effectively reduced, enabling the first solvent to stably and fully exert its advantage of high conductivity, thereby reducing the heat generation of the battery cell during fast charging and increasing the output power under fast charging conditions, further improving the fast charging performance of the battery cell.

[0082] By adopting an appropriate coating weight of the negative electrode active material layer and an appropriate amount of the first solvent in this application, the energy density of the battery cell and its performance under fast charging conditions can be improved. However, in a fast charging scenario, a large amount of heat is easily generated and accumulated inside the battery cell, resulting in adverse effects on the fast charging performance of the battery, such as gas generation and acid release of the first solvent with a low boiling point. By combining with an ear structure with a larger overcurrent area, the temperature rise of the battery cell during fast charging can be effectively slowed down, and the above-mentioned adverse effects of the first solvent with high conductivity and low boiling point in the fast charging scenario can be alleviated, making the internal resistance of the battery cell lower, reducing the heat generation of the battery cell under fast charging conditions, increasing the output power, and having better performance under fast charging conditions.

[0083] In the first aspect of this application, a battery cell is proposed. Refer to Figures 1 - 6, comprising: an electrode assembly, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator film located between the positive electrode sheet and the negative electrode sheet. Wherein, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side of the positive current collector. The positive current collector includes a positive main body portion 11 and at least one positive tab portion 12. The tab connection edge of the positive main body portion 11 is connected to the positive tab portion 12. Along the extension direction of the tab connection edge of the positive main body portion 11, the total width W1 of the positive tab portion 12 accounts for 50%-100% of the total dimension V1 of the tab connection edge of the positive main body portion 11. The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one side of the negative current collector. The negative current collector includes a negative main body portion 21 and at least one negative tab portion 22. The tab connection edge of the negative main body portion 21 is connected to the negative tab portion 22. Along the extension direction of the tab connection edge of the negative main body portion 21, the total width W2 of the negative tab portion 22 accounts for 50%-100% of the total dimension V2 of the tab connection edge of the negative main body portion 21. Wherein, the coating weight of a single layer of the negative active material layer is 0.1 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 , an electrolyte, the electrolyte includes an organic solvent, the organic solvent includes a first solvent, the first solvent includes at least one of dimethyl carbonate and a linear carboxylic acid ester. Wherein, the structural formula of the linear carboxylic acid ester satisfies R 1 -COO-R 2 , R 1 , R 2 are independently selected from alkyl or haloalkyl groups of C 1 -C 5 . Based on the total mass of the electrolyte, the mass fraction of the first solvent is 4%-72%. Thus, by adopting an appropriate coating weight of the negative active material layer, the energy density of the battery cell can be improved, as well as its performance under fast charging conditions. Further, by adopting a tab structure with a larger tab portion, the current-carrying capacity of the tab portion can be effectively improved, and the temperature rise of the battery cell during fast charging can be alleviated. Furthermore, a first solvent with high conductivity and low boiling point can be used to further reduce the internal resistance of the battery cell, thereby alleviating the heat generation of the battery cell under fast charging conditions, enhancing the output power, improving the fast charging performance of the battery cell, and improving the performance of the battery cell under fast charging conditions.

[0084] It can be understood that the positive active material layer is located on at least one side of the positive main body portion of the positive current collector, and the negative active material layer is located on at least one side of the negative main body portion of the negative current collector.

[0085] As an example, the widths of the positive electrode tab portion and the negative electrode tab portion can be the same. When the lengths of the tab connection edges of the positive electrode current collector and the negative electrode current collector are also the same, along the direction in which the tab connection edge of the positive electrode main body portion 11 extends, the ratio of the total width of the positive electrode tab portion 12 to the total size of the tab connection edge of the positive electrode main body portion 11 is the same as the ratio of the total width of the negative electrode tab portion 22 to the total size of the tab connection edge of the negative electrode main body portion 21 along the direction in which the tab connection edge of the negative electrode main body portion 21 extends.

[0086] It should be noted that when the electrode assembly is prepared by a lamination process, the electrode assembly may include a multi-layer structure of a positive electrode tab / separator / negative electrode tab / separator arranged continuously. At this time, the ratio of the total width W1 of the aforementioned positive electrode tab portion 12 to the total size V1 of the tab connection edge of the positive electrode main body portion 11 corresponds to the ratio of the width of the tab portion to the side length of the main body portion in any positive electrode tab. Similarly, the ratio of the total width W2 of the aforementioned negative electrode tab portion 22 to the total size V2 of the tab connection edge of the negative electrode main body portion 21 corresponds to the ratio of the width of the tab portion to the side length of the main body portion in any negative electrode tab. When the electrode assembly is prepared by a winding process, the electrode assembly includes only one layer of positive electrode tab, one layer of separator, and one layer of negative electrode tab. Among them, there are multiple positive electrode tab portions 12 on the positive electrode tab. At this time, the ratio of the total width of the aforementioned positive electrode tab portion 12 to the total size of the tab connection edge of the positive electrode main body portion 11 corresponds to the ratio of the sum of the widths of all positive electrode tab portions to the side length of the positive electrode main body portion. Similarly, the ratio of the total width of the aforementioned negative electrode tab portion 22 to the total size of the tab connection edge of the negative electrode main body portion 21 corresponds to the ratio of the sum of the widths of all negative electrode tab portions to the side length of the negative electrode main body portion.

[0087] As an example, along the width direction of the positive electrode main body portion 11, the total width W1 of the positive electrode tab portion 12 can account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% of the total width V1 of the positive electrode main body portion 11.

[0088] As an example, along the width direction of the negative electrode main body portion 21, the total width W2 of the negative electrode tab portion 22 can account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% of the total width V2 of the negative electrode main body portion 21.

[0089] When the battery cell undergoes high-rate charge and discharge, both the current and voltage inside the battery cell will increase correspondingly, and the current passing through the tab increases. A larger tab area means lower resistance. On the one hand, according to Ohm's law, at the same voltage, a tab with a larger area can carry a higher current, that is, it has a stronger overcurrent capacity. On the other hand, when the resistance of the tab is small, the heat generated due to resistance loss can be reduced when the current flows through the tab, reducing the heat generation of the battery under high current and indirectly improving the heat dissipation efficiency of the battery. At this time, the adverse effect of the lower boiling point of the first solvent on the performance of the battery cell is significantly reduced, and the first solvent can fully play its advantage of improving the conductivity of the electrolyte and the fast charging ability of the battery cell.

[0090] In some embodiments, the size of the tab connection edge of the positive electrode main body 11 can be greater than its size in the length direction, or, the size of the tab connection edge of the positive electrode main body 11 can be equal to its size in the length direction, or, the size of the tab connection edge of the positive electrode main body 11 can be less than its size in the length direction. That is, the positive electrode tab portion 12 can be located on the long side of the positive electrode main body 11, or on the short side of the positive electrode main body 11. Similarly, the negative electrode tab portion 22 can be located on the long side of the negative electrode main body 21, or on the short side of the negative electrode main body 21.

[0091] In some embodiments, the total width W1 of the positive electrode tab portion 12 can be 40 mm - 160 mm.

[0092] As an example, W1 can be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or 160 mm.

[0093] Similarly, in some embodiments, the total width W2 of the negative electrode tab portion 22 can also be 40 mm - 160 mm.

[0094] As an example, W2 can be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or 160 mm.

[0095] When the total widths of the positive electrode tab portion and the negative electrode tab portion are respectively within the aforementioned ranges, the overcurrent area of the tab portion is relatively large, which can effectively improve the overcurrent capacity of the tab portion, alleviate the temperature rise of the battery cell during fast charging, and then a first solvent with high conductivity and low boiling point can be used to further reduce the internal resistance of the battery cell, thereby alleviating the heat generation of the battery cell under fast charging conditions, improving the fast charging performance of the battery cell, and improving the performance of the battery cell under fast charging conditions.

[0096] In some embodiments, the width W3 of the positive electrode tab 12 may be 40 mm - 160 mm.

[0097] As an example, W1 may be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or 160 mm.

[0098] Similarly, in some embodiments, the width W4 of the negative electrode tab 22 may be 40 mm - 160 mm.

[0099] As an example, W2 may be 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or 160 mm.

[0100] As an example, referring to Figure 4 , when the electrode assembly is prepared by the lamination process, the total width W1 of the positive electrode tab 12 corresponds to the total width after stacking multiple positive electrode tabs 12 after the positive electrode sheet, negative electrode sheet and separator are laminated. Similarly, the total width W2 of the negative electrode tab 22 corresponds to the total width after stacking multiple negative electrode tabs 22 after the positive electrode sheet, negative electrode sheet and separator are laminated.

[0101] As an example, referring to Figure 6 , when the electrode assembly is prepared by the winding process, the total width W1 of the aforementioned positive electrode tab 12 corresponds to the total width after stacking multiple positive electrode tabs 12 after the positive electrode sheet, negative electrode sheet and separator are wound. Similarly, the total width W2 of the aforementioned negative electrode tab 22 corresponds to the total width after stacking multiple negative electrode tabs 22 after the positive electrode sheet, negative electrode sheet and separator are wound.

[0102] In some embodiments, the positive electrode tab 12 and the negative electrode tab 22 are located on the same side of the positive electrode main body 11. For the electrode assembly obtained by the lamination process or winding process, its positive electrode main body 11 is arranged in parallel with the negative electrode main body 21. Therefore, the positive electrode tab 12 and the negative electrode tab 22 are also located on the same side of the negative electrode main body 21. Thus, the connection of the external circuit can be simplified and the assembly process can be simplified.

[0103] In some embodiments, the positive electrode tab 12 and the negative electrode tab 22 are located on opposite sides of the positive electrode main body 11. For an electrode assembly obtained by a stacking process or a winding process, the positive electrode main body 11 is arranged parallel to the negative electrode main body 21, and the positive electrode tab 12 and the negative electrode tab 22 are also located on both sides of the negative electrode main body 21. Thereby, a more uniform heat distribution can be provided, and the deformation of the tab caused by excessive force on one side can be reduced.

[0104] In some embodiments, referring to Figure 2 , the positive electrode current collector includes the positive electrode main body 11 and a plurality of the positive electrode tabs 12. At least two of the positive electrode tabs 12 are located on opposite sides of the positive electrode main body 11. Similarly, the negative electrode current collector may include the negative electrode main body and a plurality of the negative electrode tabs, and at least two of the negative electrode tabs are located on opposite sides of the negative electrode main body. Thereby, a more uniform heat distribution can be provided, and the deformation of the tab caused by excessive force on one side can be reduced.

[0105] In some embodiments, referring to Figure 3 , the positive electrode current collector includes the positive electrode main body 11 and a plurality of positive electrode tabs 12 spaced apart along the length direction of the positive electrode current collector. Similarly, the negative electrode current collector may also include the negative electrode main body 21 and a plurality of negative electrode tabs 22 spaced apart along the length direction of the negative electrode current collector.

[0106] When the positive electrode current collector includes a plurality of positive electrode tabs 12 and the negative electrode current collector includes a plurality of negative electrode tabs 22, the transmission path of electrons between the positive electrode tab and the negative electrode tab is shorter, which can reduce the heat generation of the battery and improve the fast charging performance.

[0107] Next, referring to Figures 1 - 6 a specific embodiment will be described: Referring to Figure 1 , in some specific embodiments, taking the electrode assembly prepared by the stacking process as an example, the positive electrode plate used is rectangular. At this time, one of the short sides of the two short sides on both sides of the positive electrode current collector has a positive electrode tab 12 extending along the length direction of the positive electrode current collector. The width of the positive electrode tab is W3, and the total dimension V1 of the tab connection side of the positive electrode main body is the width of the positive electrode current collector. Similarly, the corresponding negative electrode current collector may also have a similar structure. At this time, one of the short sides of the two short sides on both sides of the negative electrode current collector has a negative electrode tab extending along the length direction of the negative electrode current collector. The width of the negative electrode tab is W4, and the total dimension V2 of the tab connection side of the negative electrode main body is the width of the negative electrode current collector.

[0108] Referring to Figure 2, in some specific embodiments, taking the preparation of the electrode assembly by the lamination process as an example, the positive electrode tab used is rectangular. At this time, the short sides on both sides of the positive current collector respectively have positive electrode tab portions 12 extending along the length direction of the positive current collector, and the extending directions of the two positive electrode tab portions 12 are opposite. Among them, the widths W3 of the multiple positive electrode tab portions 12 can be the same or different, and the total dimension V1 of the tab connection side of the positive electrode main body portion is the width of the positive current collector. Similarly, the corresponding negative current collector can also have a similar structure. At this time, the widths W4 of the multiple negative electrode tab portions can be the same or different, and the total dimension V2 of the tab connection side of the negative electrode main body portion is the width of the negative current collector.

[0109] Reference Figure 3 , in some specific embodiments, taking the preparation of the electrode assembly by the lamination process as an example, the positive electrode tab used is rectangular. At this time, one of the long sides of the two long sides on both sides of the positive current collector has multiple positive electrode tab portions 12 extending along the width direction of the positive current collector, and the multiple positive electrode tab portions 12 are arranged at intervals along the length direction of the positive current collector. Among them, the width of each positive electrode tab portion can be the same or different. Taking the case of having three positive electrode tab portions as an example, the widths of the three positive electrode tab portions 12 are L1, L2, and L3 respectively. L1, L2, and L3 can all be the same, or all different, or any two of them can be the same. At this time, the total width W1 of the positive electrode tab portion is the sum of the widths of the multiple positive electrode tab portions, that is, W1 = L1 + L2 + L3, and the total dimension V1 of the tab connection side of the positive electrode main body portion is the length of the positive current collector. Similarly, the corresponding negative current collector can also have a similar structure. At this time, the total width W2 of the negative electrode tab portion is the sum of the widths of the multiple negative electrode tab portions, and the width of the negative electrode main body portion is the length of the negative current collector.

[0110] Reference Figure 4 , in some specific embodiments, in the electrode assembly prepared by the lamination process, the multiple positive electrode tab portions 12 are arranged in a staggered manner (at least partially overlapping between adjacent positive electrode tab portions). At this time, the total width W1 of the positive electrode tab portions 12 corresponds to the total width after stacking of the multiple positive electrode tab portions 12 after the lamination of the positive electrode tab, the negative electrode tab, and the separator film. Similarly, the multiple negative electrode tab portions 22 are arranged in a staggered manner (at least partially overlapping between adjacent negative electrode tab portions), and the total width W2 of the negative electrode tab portions 22 corresponds to the total width after stacking of the multiple negative electrode tab portions 22 after the lamination of the positive electrode tab, the negative electrode tab, and the separator film.

[0111] Reference Figure 5, in some specific embodiments, taking the preparation of the electrode assembly by winding process as an example, the corresponding positive current collector can have a plurality of positive electrode tab portions 12 extending in a direction perpendicular to the long side of the positive electrode main body 11 after being horizontally expanded. Among them, the width W3 of each positive electrode tab portion can be the same or different. Similarly, the corresponding negative current collector can also have a similar structure, and the width W4 of each negative electrode tab portion can be the same or different.

[0112] Reference Figure 6 , in some specific embodiments, in the electrode assembly prepared by winding process, wherein, the positive current collector and the negative current collector have the structure as Figure 5 shown. The total width W1 of the aforementioned positive electrode tab portions 12 corresponds to the total width after stacking of a plurality of positive electrode tab portions 12 after winding the positive electrode sheet, the negative electrode sheet and the separator (at least partial overlap between adjacent positive electrode tab portions). Similarly, the total width W2 of the aforementioned negative electrode tab portions 22 corresponds to the total width after stacking of a plurality of negative electrode tab portions 22 after winding the positive electrode sheet, the negative electrode sheet and the separator (at least partial overlap between adjacent negative electrode tab portions).

[0113] As an example, the coating weight of the single-layer negative active material layer can be 0.1 g / 1540.25 mm 2 、0.105 g / 1540.25 mm 2 、0.115 g / 1540.25 mm 2 、0.12 g / 1540.25 mm 2 、0.125 g / 1540.25 mm 2 、0.13 g / 1540.25 mm 2 、0.135 g / 1540.25 mm 2 、0.14 g / 1540.25 mm 2 、0.145 g / 1540.25 mm 2 .

[0114] As an example, the coating weight of the single-layer negative active material layer can be obtained by the following method: The coating weight can be obtained by wiping the negative active material layer on the negative electrode sheet and calculating the mass difference before and after.

[0115] In some embodiments, the organic solvent includes a first solvent, and the first solvent includes at least one of dimethyl carbonate (DMC) and linear carboxylic acid ester. Among them, the structural formula of the linear carboxylic acid ester satisfies R 1 -COO-R 2 , R 1 、R 2 are independently selected from C 1 -C 5An alkyl or haloalkyl group. Thereby, the viscosity of the electrolyte can be effectively reduced.

[0116] The viscosity of the aforementioned first solvent is relatively low, and thus the overall viscosity of the electrolyte mainly composed of organic solvents is relatively low. In the low-viscosity electrolyte, the intermolecular interaction force is weak, and the movement between molecules is more free, enabling the diffusion and migration rate of lithium ions in the electrolyte to increase. Further, when the battery cell undergoes rapid charge and discharge, concentration polarization will occur inside the battery. When the ion migration rate of the electrolyte is relatively high, the concentration polarization inside the battery can be alleviated. The aforementioned low-viscosity electrolyte can effectively reduce concentration polarization by increasing the ion migration rate and improve the fast-charging performance of the battery.

[0117] As an example, the viscosity of the electrolyte can be measured by the following method: The viscosity is measured by a viscometer. Referring to the national standard GB / T 10247-2008 "Viscosity Measurement Method": At a certain temperature, when the rotor rotates continuously in the sample at a constant speed, the shear force causes the spring to generate torque, and the torque is proportional to the viscosity, obtaining the viscosity value.

[0118] In some embodiments, the linear carboxylic acid ester includes at least one of ethyl formate, isopropyl formate, ethyl acetate (EA), methyl acetate, propyl acetate, and methyl propionate. Thereby, the viscosity of the electrolyte can be further reduced.

[0119] The linear carboxylic acid ester has good lithium salt solubility, can increase the conductivity of the electrolyte, accelerate the migration rate of lithium ions inside the battery, and improve the charge and discharge efficiency of the battery. Moreover, the linear carboxylic acid ester exhibits good thermal stability and oxidation stability at high temperatures, which helps to improve the stability of the battery under fast-charging conditions and reduce the risk of thermal runaway.

[0120] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the first solvent is 16% - 72%. Thereby, the fast-charging performance of the battery cell can be improved.

[0121] As an example, based on the total mass of the electrolyte, the mass fraction of the first solvent can be 4%, 8%, 12%, 16%, 20%, 24%, 28%, 32%, 36%, 40%, 44%, 48%, 52%, 56%, 60%, 64%, 68% or 72%.

[0122] As the mass fraction of the first solvent increases, the viscosity of the electrolyte gradually decreases, and the fast-charging performance of the battery is further improved.

[0123] As an example, the quantitative test of the first solvent can be obtained by the following method: The organic components in the electrolyte can be quantitatively analyzed by gas chromatography with reference to the standard GB / T 9722-2006.

[0124] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the linear carboxylic ester is 32% - 68%.

[0125] As an example, based on the total mass of the electrolyte, the mass fraction of the linear carboxylic ester can be 32%, 36%, 40%, 44%, 48%, 52%, 56%, 60%, 64% or 68%.

[0126] The linear carboxylic ester has a low viscosity. When the mass fraction of the linear carboxylic ester is within the above range based on the total mass of the electrolyte, the liquid-phase transport resistance of lithium ions can be further reduced, and the fast charging performance and cycling performance of the battery cell can be improved. As an example, the quantitative analysis of the linear carboxylic ester can be obtained by the following method: The organic components in the electrolyte can be quantitatively analyzed by gas chromatography with reference to Standard GB / T9722 - 2006.

[0127] It can be understood that generally, the electrolyte includes organic solvents and lithium salts (including electrolyte lithium salts and lithium salt additives). Based on the total mass of the electrolyte, the mass fraction of the organic solvents is about 80%, and the rest can be lithium salts and / or additives.

[0128] In some embodiments, the coating weight of the single-layer negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135 g / 1540.25 mm 2 . Thus, the battery cell has a high volumetric energy density.

[0129] When the coating weight of the single-layer negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135 g / 1540.25 mm 2 At this time, the thickness of the negative electrode active material layer is relatively thin, and the diffusion distance required for lithium ions in the negative electrode active material layer is short, so the transport of lithium ions can be accelerated, which is beneficial to improving the fast charging performance of the battery. For example, the time required for the battery cell using the negative electrode sheet with the aforementioned coating weight to charge from 10% SOC to 80% SOC is 7 min - 15 min. Thus, the battery cell has excellent fast charging performance.

[0130] Taking the electrical device as an automobile as an example, in the actual use scenario, for an automobile, the state of charge (SOC) of its battery is usually between 10% and 80%. Thus, when the charging time of the battery within this SOC range is short, the waiting time of the user for charging can be reduced, greatly improving the user experience.

[0131] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 . Thus, the battery cell has a relatively high volumetric energy density.

[0132] In some embodiments, the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 When the battery cell is assembled with the aforementioned positive electrode sheet, the volumetric energy density of the battery cell can be 410 Wh / L - 430 Wh / L. Thus, the battery cell has a relatively high volumetric energy density.

[0133] When the coating weight of a single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 the thickness of the negative electrode active material layer is relatively thick, and there are more lithium ion insertion and extraction sites provided by the negative electrode active material, which helps to improve the energy density of the battery.

[0134] In some embodiments, the time for the battery cell to charge from 10% SOC to 80% SOC is 20 min - 30 min. Thus, the battery cell has relatively good fast charging performance.

[0135] In some embodiments, the negative electrode sheet includes a negative electrode current collector and at least one negative electrode active material layer on one side of the negative electrode current collector, and the tap density of the negative electrode active material layer is 1.2 g / cm3 - 1.5 g / cm 3 . Thus, it helps to improve the fast charging performance of the battery cell.

[0136] As an example, the tap density of the negative electrode active material layer can be 1.2 g / cm 3 、1.3 g / cm 3 、1.4 g / cm 3 or 1.5 g / cm 3 .

[0137] When the tap density of the negative electrode active material layer is within the aforementioned range, the tap density of the negative electrode active material layer is relatively moderate. At this time, the lithium ion insertion and extraction rate of the negative electrode sheet is relatively fast, which is beneficial to improving the fast charging performance of the battery.

[0138] As an example, the test method for the tap density of the negative electrode active material layer can be the same as that for the tap density of the positive electrode active material layer, which will not be elaborated here.

[0139] In some embodiments, the negative electrode sheet can be prepared in the following manner: The components for preparing the negative electrode sheet described above, such as the negative electrode active material, conductive agent, binder, and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on a negative electrode current collector, and after processes such as drying and rolling (such as a cold pressing process), a negative electrode active material layer can be formed, and the negative electrode sheet is obtained. The tap density of the aforementioned negative electrode active material layer refers to the tap density of the negative electrode active material layer after the rolling process. Specifically, the tap density of the negative electrode active material layer after the rolling process and formation process, the tap density of the negative electrode active material layer when the battery cell is in a fully charged state or a fully discharged state, and the tap density of the negative electrode active material layer after the battery cell has been static for a long time are all within the aforementioned range.

[0140] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0141] In some embodiments, the negative electrode active material can be a negative electrode active material for batteries well-known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material can 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 can 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 conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0142] In some embodiments, the negative electrode active material layer may also optionally include a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0143] In some embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0145] In some embodiments, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the negative electrode active material is 0.1% - 7%. Thereby, the mass energy density of the battery cell can be improved.

[0146] The theoretical specific capacity of silicon is as high as 4200 mAh / g, which is much higher than that of graphite materials. By adding a silicon-containing material to the negative electrode active material, the mass energy density of the battery can be effectively improved; further, since the pure silicon material will undergo a huge volume expansion (up to more than 300%) after lithium ions are inserted, resulting in the rupture and recombination of the SEI (solid electrolyte interface), the electrolyte and active lithium ions are consumed, and ultimately the cycle life of the battery decreases. By controlling the mass fraction of silicon in the silicon-containing material to be 0.1% - 7%, it is possible to not only utilize the extremely high theoretical specific capacity of silicon to improve the mass energy density of the battery, but also help alleviate the volume expansion and contraction of the silicon-containing material during charge and discharge.

[0147] As an example, the mass fraction of silicon in the silicon-containing material is 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5% or 7%.

[0148] As an example, the silicon-containing material can be a silicon-carbon material.

[0149] In some embodiments, the mass fraction of silicon in the silicon-containing material is 1% - 5%. Thereby, the mass energy density of the battery cell can be further improved.

[0150] As an example, the mass fraction of silicon in the silicon-containing material can be measured by the following method: Standards YS / T 1006.2 - 2014, GB / T 23367.2 - 2009 or YS / T 1028.5 - 2015 can be referred to. Specifically, an ICP inductively coupled plasma emission spectrometer can be used for measurement according to the manufacturer's instructions.

[0151] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer which are stacked. The first negative electrode active material layer is located on the side close to the negative electrode current collector. The Dv50 of the first negative electrode active material in the first negative electrode active material layer is 9.2 μm - 18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2 μm - 15.5 μm. Thus, the fast charging performance and energy density of the battery cell can be significantly improved.

[0152] When the Dv50 particle sizes of the first negative electrode active material and the second negative electrode active material are within the aforementioned ranges, the particle size of the second negative electrode active material is smaller than that of the first negative electrode active material. The particle size of the particles in the first negative electrode active material layer is larger, which can provide more lithium insertion and extraction sites and improve the battery capacity. The particle size of the particles in the second negative electrode active material layer is smaller, and the lithium ion insertion and extraction rate is faster, which helps to improve the fast charging performance of the battery.

[0153] In some embodiments, the conductivity of the electrolyte is 10 mS / cm - 20 mS / cm. Thus, it helps to improve the fast charging performance of the battery cell.

[0154] As an example, the conductivity of the electrolyte can 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 or 20 mS / cm.

[0155] When the conductivity of the electrolyte is within the range, the electrolyte can conduct lithium ions more effectively, thereby effectively reducing the internal resistance of the battery, helping to improve the fast charging performance of the battery, and reducing the temperature rise of the battery caused by the resistance thermal effect during charge and discharge, reducing the thermal stress inside the battery cell, and further improving the performance of the battery under high power.

[0156] As an example, the conductivity of the electrolyte can be directly measured by a conductivity meter using a method well-known in the art.

[0157] In some embodiments, the electrolyte further includes a first lithium salt additive. The first lithium salt additive includes at least one of a fluoroborate and a fluorophosphate. Based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.05% - 0.5%. Thus, the internal resistance of the battery cell can be effectively reduced.

[0158] As an example, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0159] By adding a lithium salt additive containing at least one of fluoroborate and fluorophosphate to the electrolyte of the battery cell, it helps to form a low-impedance SEI film containing boron atoms and phosphorus atoms on the surface of the negative electrode active material, effectively reducing the internal resistance of the battery cell, so that the battery cell has both a high energy density and fast charging performance. When the mass fraction of the first lithium salt additive is within the aforementioned range, the first lithium salt additive helps to form a low-impedance SEI film on the surface of the negative electrode active material, and at the same time, the dosage is small, which helps to reduce the cost of the electrolyte.

[0160] As an example, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive can be obtained by the following method: Take out the free electrolyte in the finished battery and use an ion chromatography test method to test the content of the first lithium salt additive. The concentration of the first lithium salt additive in the electrolyte can be quantitatively analyzed by ion chromatography analysis method with reference to the standard JY / T020-1996.

[0161] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalate phosphate, lithium difluorooxalate borate, and lithium tetrafluoroborate. Thus, it helps to form a low-impedance solid electrolyte film on the surface of the negative electrode active material.

[0162] The first lithium salt additive itself has a high ionic conductivity, which can increase the migration rate of lithium ions in the electrolyte; further, the first lithium salt additive can form a stable and dense low-resistance SEI film on the surface of the negative electrode active material during the first charge, which can not only reduce the side reaction between the negative electrode active material and the electrolyte, but also reduce the internal resistance of the battery.

[0163] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.1% - 0.3%. Thus, it helps to reduce the cost of the battery cell.

[0164] The dosage of the first lithium salt additive in the electrolyte is related to the migration distance of lithium ions between the positive and negative electrodes. When the migration distance of lithium ions between the positive and negative electrodes is long, it is necessary to correspondingly increase the dosage of the first lithium salt additive in the electrolyte, so as to reduce the internal resistance of the battery and relieve the increase in the internal resistance of the battery caused by the long migration distance of lithium ions. When the mass fraction of the first lithium salt additive in the electrolyte is within the aforementioned range, the battery cell can balance a lower internal resistance and a lower manufacturing cost.

[0165] In some embodiments, the organic solvent further includes a second solvent, and the second solvent includes at least one of ethylene carbonate, ethylene carbonate (EC), propylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, and fluoroethylene carbonate. Thereby, it helps to improve the cycle life of the battery cell.

[0166] The aforementioned second solvent has a wide electrochemical stability window and can remain stable even in a high-voltage environment, thereby reducing its own decomposition in the electrochemical reaction and improving the cycle life of the battery cell.

[0167] In some embodiments, the second solvent includes diethyl carbonate, and based on the total mass of the electrolyte, the mass fraction of diethyl carbonate is greater than or equal to 12%. Thereby, it helps to further improve the cycle life of the battery cell.

[0168] Diethyl carbonate has appropriate viscosity and boiling point, which helps to adjust the physical properties of the electrolyte, making the electrolyte have appropriate viscosity and excellent low-temperature performance.

[0169] In some embodiments, the electrolyte further includes non-lithium salt additives, and the non-lithium salt additives include sulfate additives and carbonate additives. Thereby, it helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0170] The carbonate non-lithium salt additive containing a double bond helps to form a SEI film with good flexibility on the surface of the negative electrode active material, which can slow down the destruction of the interface film caused by the volume cyclic expansion of the negative electrode active material during the cyclic charge and discharge process, improve the cycle stability of the battery cell, and increase the cycle life.

[0171] In some embodiments, the carbonate additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and ethylene vinylene carbonate. Thereby, it helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0172] In some embodiments, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate is 0.5% - 2.5%, and / or the mass fraction of fluoroethylene carbonate is 0.05% - 2%. Thereby, it helps to form a dense and stable solid electrolyte film on the surface of the negative electrode active material.

[0173] As an example, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate is 0.5%, 1%, 1.5%, 2.0% or 2.5%.

[0174] As an example, based on the total mass of the electrolyte, the mass fraction of vinylene carbonate fluoride is 0.05%, 0.1%, 0.5%, 1%, 1.5% or 2.0%.

[0175] It can be understood that since the carbonate non-lithium salt additive containing a double bond participates in the formation of the SEI film on the surface of the negative electrode active material during the formation process and is thus partially consumed, the actual detected amount of the above substances in the battery cell will be slightly less than the added amount. For example, based on the total mass of the electrolyte, when the addition amount of vinylene carbonate is 2.0%, its actual detected amount in the battery cell is about 0.87%; based on the total mass of the electrolyte, when the addition amount of vinylene carbonate fluoride is 1.3%, its actual detected amount in the battery cell is about 0.05%.

[0176] In some embodiments, the sulfate additive includes at least one of 4,4-vinylsulfate, divinylsulfate, trithioethylene carbonate, 1,3-propane sultone.

[0177] In some embodiments, based on the total mass of the electrolyte, the mass fraction of the non-lithium salt additive is 0.05% - 3%. Thereby, it helps to reduce the cost of the battery cell.

[0178] In some embodiments, the electrolyte further includes a second lithium salt additive, and the second lithium salt additive includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium perchlorate. Thereby, it helps to form a solid electrolyte film with higher ionic conductivity on the surface of the negative electrode active material.

[0179] The second lithium salt additive can preferentially form a dense and stable interfacial film on the surface of the negative electrode active material over the organic solvent, inhibit the oxidative decomposition of the organic solvent at the negative electrode, reduce the consumption of active lithium due to the side reaction between the negative electrode active material and the electrolyte; effectively prevent the direct contact between the organic solvent and the negative electrode active material, and the presence of the interfacial film also helps to reduce the dissolution of transition metals from the negative electrode active material.

[0180] In some embodiments, the electrolyte further includes an electrolyte lithium salt, and the electrolyte lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte, the mass fraction of the electrolyte lithium salt is greater than or equal to 13%. Thereby, it helps to improve the conductivity of the electrolyte.

[0181] As an example, based on the total mass of the electrolyte, the mass fraction of the electrolyte lithium salt is 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 21%, 23%, 24% or 25%.

[0182] When the mass fraction of the electrolyte lithium salt is within the aforementioned range based on the total mass of the electrolyte, the electrolyte has both high ionic conductivity and low viscosity. After the electrolyte lithium salt is dissolved in the organic solvent, lithium ions can be released. The lithium ions form a solvation structure with the electrolyte, improving the conductivity of the electrolyte and facilitating the rapid migration of lithium ions in the electrolyte.

[0183] In some embodiments, the electrolyte lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide in the electrolyte is (1.2 - 2):1. Thereby, it helps to further improve the conductivity of the electrolyte.

[0184] Lithium bis(fluorosulfonyl)imide has better conductivity, thermal stability, hydrolysis resistance, etc. than lithium hexafluorophosphate. However, lithium bis(fluorosulfonyl)imide has the problem of being difficult to dissociate sufficiently. Lithium hexafluorophosphate has advantages in commercial production and application maturity and lower production costs. When the electrolyte lithium salt includes both lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate can promote the better dissociation of lithium bis(fluorosulfonyl)imide, improve the performance of the electrolyte, and thus improve the battery cycle life and fast charging performance.

[0185] As an example, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide in the electrolyte can be obtained by the following method: The concentration of inorganic components in the electrolyte can be quantitatively analyzed by ion chromatography analysis method with reference to the standard JY / T020 - 1996.

[0186] As an example, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide in the electrolyte can be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1.

[0187] In some embodiments, the tap density of the positive electrode active material layer is 2.2 g / cm 3 - 2.6 g / cm 3 . Thereby, it helps to improve the fast charging performance and energy density of the battery cell.

[0188] As an example, the tap density of the positive electrode active material layer can be 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 or 2.6 g / cm 3 .

[0189] When the tap density of the positive electrode active material layer is within the aforementioned range, the tap density of the positive electrode active material layer is relatively moderate, and at this time, the positive electrode plate has a high energy density.

[0190] As an example, the tap density of the positive electrode active material layer can be obtained by the following method: by dividing the mass of the positive electrode active material layer by the thickness. The mass and thickness of the positive electrode active material layer can be obtained by wiping the positive electrode active material layer on the positive electrode plate and calculating the difference in mass and thickness before and after.

[0191] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the positive electrode active material, conductive agent, binder and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and rolling (such as cold pressing process), a positive electrode active material layer can be formed to obtain the positive electrode plate.

[0192] The aforementioned tap density of the positive electrode active material layer refers to the tap density of the positive electrode active material layer after rolling treatment. Specifically, the tap density of the positive electrode active material layer after rolling treatment and formation treatment, the tap density of the positive electrode active material layer when the battery cell is in a fully charged state or a fully discharged state, and the tap density of the positive electrode active material layer after the battery cell is static for a long time are all within the aforementioned range.

[0193] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes: a core portion, the core portion includes a lithium-containing phosphate with an olivine structure, and a coating layer, the coating layer covers the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, Sn. Thereby, it helps to improve the structural stability and ionic conductivity of the positive electrode active material.

[0194] The lithium-containing phosphate with an olivine structure has both low cost and high theoretical specific capacity, which helps to improve the energy density of the battery cell, and the olivine structure can maintain good crystal integrity during charge and discharge, reduce structural stress, and extend the cycle life of the battery. The coating layer can effectively alleviate the poor electron conductivity and ionic conductivity of the lithium-containing phosphate with an olivine structure, and improve the specific capacity and powder tap density of the positive electrode active material.

[0195] In some embodiments, the lithium-containing phosphate with an olivine structure includes a general formula of Li x1 A y1 Me a M1 b P 1-c X c Y zcompounds, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3; 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5; 0 ≤ c ≤ 0.5; 3 ≤ z ≤ 5; A includes one or more of Na, K, Mg; Me includes one or more of Mn, Fe, Co, Ni; M1 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N; Y includes one or more of O, F. Thus, it helps to improve the ionic conductivity and electronic conductivity of the core part.

[0196] When the lithium-containing phosphate with olivine structure satisfies the aforementioned general formula, its advantages for ternary materials are fully utilized to improve the high-temperature resistance and structural stability of the battery monomer prepared therefrom, and reduce the manufacturing cost of the battery monomer.

[0197] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode active material in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Li will change after charge and discharge cycles.

[0198] In the listing of the positive electrode active material for lithium-ion batteries in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0199] In some embodiments, the coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15 - 0.32. Thus, it helps to improve the electronic conductivity of the positive electrode active material.

[0200] The setting of the carbon layer can significantly improve the electronic conductivity of the lithium-containing phosphate with olivine structure, make up for the defect of poor electronic conduction performance of the lithium-containing phosphate with olivine structure, and improve the capacity utilization of the battery monomer.

[0201] As an example, the graphitization degree of the carbon layer can be 0.15, 0.17, 0.19, 0.21, 0.23, 0.25, 0.27, 0.29, 0.31 or 0.32.

[0202] When the graphitization degree of the carbon layer is within the aforementioned range, the arrangement of carbon atoms in the carbon layer is relatively disordered, with many lattice defects and no complete graphite lattice formed. The electronic conductivity is slightly lower compared to carbon materials with a higher graphitization degree. The carbon layer with a relatively disordered arrangement of carbon atoms usually has a higher specific surface area, which helps to fully contact the core and the electrolyte and improve the lithium-ion transport efficiency at the two-phase interface.

[0203] As an example, the graphitization degree of the carbon layer can be measured by the following method: The graphitization degree can refer to the standards JB / T4220-2011 and JISK0131-1996 and be determined by the lattice parameters of the carbon crystal using the XRD diffraction method.

[0204] In some embodiments, in the cross-section of the positive electrode active material layer in the thickness direction, the positive electrode active material includes lithium-containing phosphate with an olivine structure having a longest diameter of 1 μm - 3 μm and lithium-containing phosphate with an olivine structure having a shortest diameter of 0.1 μm - 0.3 μm. Thus, it is beneficial to improve the energy density of the battery cell.

[0205] As an example, in the cross-section of the positive electrode active material layer in the thickness direction, the positive electrode active material includes lithium-containing phosphate with an olivine structure having a longest diameter of 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0206] As an example, in the cross-section of the positive electrode active material layer in the thickness direction, the positive electrode active material includes lithium-containing phosphate with an olivine structure having a shortest diameter of 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, or 0.3 μm.

[0207] In some embodiments, the Dv50 particle size of the positive electrode active material is 1 μm - 5 μm.

[0208] As an example, the Dv50 particle size of the positive electrode active material can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm.

[0209] In some embodiments, the Dv10 particle size of the positive electrode active material is 0.4 μm - 0.7 μm.

[0210] As an example, the Dv10 particle size of the positive electrode active material can be 0.4 μm, 0.5 μm, 0.6 μm, or 0.7 μm.

[0211] When the Dv50 particle size and the Dv10 particle size of the positive electrode active material are within the aforementioned range, the overall particle size distribution of the positive electrode active material is relatively reasonable, which is beneficial to improving the powder compaction density of the positive electrode active material, and then beneficial to improving the electrode compaction density of the positive electrode sheet, and ultimately enhancing the volume energy density of the battery cell.

[0212] The aforementioned Dv50 particle size refers to the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 50%.

[0213] The aforementioned Dv10 particle size refers to the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 10%.

[0214] As an example, the particle size of the positive electrode active material can be measured by laser diffraction particle size analysis method. Specifically, the particle size of the positive electrode active material can be measured with reference to the standard GB / T19077-2016 using a laser particle size analyzer (such as Malvern-Master-Size-3000).

[0215] In some embodiments, the positive electrode active material is primary particles or quasi-single crystal particles. Thus, the relatively large particle size of the positive electrode active material is beneficial to improving the energy density of a single battery cell.

[0216] When the positive electrode active material is primary particles or quasi-single crystal particles, the particle size of the positive electrode active material is relatively large, which helps to improve its powder tap density. Further, in the case of a similar particle size distribution, the larger the primary particle size of the positive electrode active material, the greater the powder tap density of the positive electrode active material, which is beneficial to improving the volume energy density of a single battery cell.

[0217] In some embodiments, the positive electrode active material is a mixture of primary particles and secondary particles. Thus, the primary particles can improve the powder tap density of the positive electrode active material, and the secondary particles can enhance the ionic conductivity of the positive electrode active material. The combined use of primary particles and secondary particles can jointly improve the volume energy density and fast charging ability of the battery.

[0218] In some embodiments, the positive electrode active material layer further includes a lithium-rich material, and the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, lithium nickel copperate, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, and lithium nickel cobalt manganate. Thus, it helps to improve the cycle life of a single battery cell.

[0219] During the first charge of the battery, an SEI film will be formed on the surface of the negative electrode active material, and the rupture and recombination of the SEI during the charge-discharge cycle will both cause irreversible consumption of lithium ions, resulting in a decrease in the first-cycle efficiency and capacity loss of the battery. By adding the lithium-rich material, this part of the lost lithium can be replenished in advance during the battery preparation process, reducing or eliminating the capacity decay caused by lithium loss and extending the cycle life of the battery.

[0220] In some embodiments, the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, and lithium oxalate. Thus, after the lithium-rich material releases lithium ions through the formation process, the remaining products can improve and reduce the internal resistance of the positive electrode active material, improve the DC impedance of the battery, and increase the charge and discharge power of the battery.

[0221] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0222] In some embodiments, the positive electrode active material layer may also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0223] In some embodiments, the positive electrode active material layer may also optionally include a conductive agent. As an example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0224] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0225] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0226] In some embodiments, the length of the battery cell is L, and the width of the battery cell is H. The value of L is 4 to 10 times the value of H. Thus, the volume utilization rate of the battery can be effectively improved, and the overall energy density of the battery can be increased.

[0227] By flattening and extending the battery cell, a thin and long shape is formed. Arranging and combining the long-strip-shaped battery cells directly forms a battery pack, eliminating the intermediate module structure, which can effectively improve the volume utilization rate of the battery pack and increase the overall energy density of the battery cell.

[0228] As an example, the value of L can be 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times, 9.5 times or 10 times the value of H.

[0229] When the proportional relationship between the values ​​of L and H is within the above range, it helps to improve the volume utilization of the battery pack formed by the assembly of battery cells, and when a collision or external impact occurs, the force on the battery cells is more uniform and dispersed, effectively reducing the risk of short circuit.

[0230] In some embodiments, the value of L is 4 to 7 times the value of H. This helps the battery cell to have both higher energy density and lower internal resistance.

[0231] In some embodiments, L is 400 mm-1000 mm, and / or H is 80 mm-160 mm.

[0232] As an example, L may be 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, 700 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm or 1000 mm.

[0233] As an example, H may be 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or 160 mm.

[0234] When L and H are within the above numerical range, the size of the battery cell is moderate, which is conducive to transfer and rapid assembly, and the transmission path of lithium ions in the battery cell is relatively short, and the internal resistance of the battery cell is small.

[0235] In some embodiments, reference Figures 1 - 8 , further comprising a shell, the electrode assembly is located in the shell, the shell comprises two first shell walls 101 arranged opposite to each other, and a surrounding wall connecting the two first shell walls 101, the surrounding wall comprises: two second shell walls 102 arranged opposite to each other along the length direction of the first shell wall 101, and two third shell walls 103 arranged opposite to each other along the width direction of the first shell wall 101, the second shell wall 102 is provided with an electrode terminal, the positive pole ear 12 and the negative pole ear 22 are respectively electrically connected to the electrode terminals on the two second shell walls 102, wherein a folding structure 106 is provided between the second shell wall 102 electrically connected to the positive pole ear 12 and the positive main body 11, and the folding structure 106 is configured to fold a plurality of the positive pole ears 12. Thus, the fixing of the positive pole ear and the welding between the positive pole sheet and the pole 105 are facilitated.

[0236] refer to Figure 4 and Figure 5 , the positive pole ear 12 and the negative pole ear 22 of the battery cell are respectively led out from the two second shell walls of the shell, that is, the pole ears are led out from the opposite sides, which helps to arrange the battery cells more efficiently in a limited space, and facilitates multiple battery cells to form an efficient series and parallel structure inside the battery pack, while reducing the space occupied by the connectors between the battery cells and improving the volume energy density of the battery pack. In order to improve the volume energy density, a lamination process can be used to form an electrode assembly, in which each positive pole piece has a corresponding positive pole ear, and each negative pole piece has a corresponding negative pole ear. In order to achieve convergence, all the positive pole ears 12 and negative pole ears 22 need to be collected separately and then electrically connected to the corresponding electrode terminals.

[0237] Normally, the positive electrode current collector is made of aluminum foil and the negative electrode current collector is made of copper foil. Since copper foil is soft and prone to breakage, it is necessary to first weld the negative electrode ear to the corresponding pole on the second shell wall and then install it into the surrounding wall structure formed by the first shell wall and the third shell wall, and finally weld the positive electrode ear to the corresponding pole on the second shell wall. In order to reduce the possibility of the positive electrode ear being inverted during the welding process with the corresponding second shell wall, thereby causing an internal short circuit in the battery cell, multiple positive electrode ears can be fixed by a folding structure to reduce the inverted insertion of the pole ears and facilitate the welding of the positive electrode ear to the lower seat of the pole.

[0238] In some embodiments, the edge of the positive electrode sheet is chamfered in the length direction of the first shell wall 101. This facilitates the rapid assembly of the electrode assembly and alleviates the occurrence of poor puncture of the separator when the electrode assembly is inserted into the shell.

[0239] In some embodiments, a liquid injection hole is provided on the second shell wall 102 connected to the negative electrode ear portion 22, thereby facilitating the injection of electrolyte.

[0240] Since a gathering structure for gathering the positive electrode ear is provided on the second shell wall connected to the positive electrode ear, in order to make the second shell wall have higher mechanical strength, the injection hole is provided on the second shell wall 102 connected to the negative electrode ear 22 .

[0241] In some embodiments, reference Figure 9 and Figure 10 The injection hole 107 and the pressure relief portion 104 of the shell are located on different second shell walls 102, and the pressure relief portion 104 is configured to release the pressure inside the shell. Thus, the corrosion of the pressure relief portion 104 by the electrolyte during the injection process can be reduced.

[0242] When injecting electrolyte into the battery cell through the liquid injection hole, the electrolyte will corrode the pressure relief part. Therefore, the liquid injection hole and the pressure relief part of the housing should be located on different second side walls.

[0243] In some embodiments, referring to Figure 11 , at least one mounting hole is provided on the electrode terminal, and the pole post 105 passes through the mounting hole and is riveted to the pole ear part. Thereby, it helps to reduce the volume of the battery cell, reduce the weight of the battery cell, and improve the energy density of the battery cell.

[0244] Implementing electrical connection through a single pole post can reduce the connection points, simplify the production and assembly processes, and requires less materials and processing steps, resulting in lower costs.

[0245] In some embodiments, referring to Figure 9 and Figure 10 , at least two mounting holes are provided on the electrode terminal, and each pole post 105 passes through the mounting hole and is riveted to the pole ear part. Thereby, it helps to improve the current-carrying capacity of the pole post 105.

[0246] Implementing electrical connection through a double pole post can disperse the current, reduce local overheating, and improve the fast charging performance of the battery.

[0247] In some embodiments, the diameter of the pole post 105 is 3 mm - 8 mm. Thereby, the pole post 105 has both a relatively high current-carrying capacity and a relatively low space occupation.

[0248] As an example, the diameter of the pole post can be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm.

[0249] When the diameter of the pole post is within the above range, the pole post has a relatively strong current-carrying capacity and a relatively low internal resistance, and can reduce heat generation.

[0250] In some embodiments, referring to Figure 12 , the pole post 105 riveted to the positive pole ear part 12 and the pole post 105 riveted to the negative pole ear part are arranged in a staggered manner along the length direction of the first housing wall 101. Optionally, the pole post 105 riveted to the positive pole ear part and the pole post 105 riveted to the negative pole ear part are arranged diagonally along the length direction of the first housing wall 101. Thereby, it helps to more efficiently arrange the battery cell in a limited space and improve the volume energy density of the assembled battery module or battery pack.

[0251] In some embodiments, referring to Figure 13 , the pole post 105 and the pole ear are electrically connected through a connecting piece 108. Thereby, the welding quality and connection reliability between the pole post 105 and the pole ear can be significantly improved.

[0252] When realizing the electrical connection between the terminal post and the tab through an adapter piece, the shape and size of the adapter piece can be adjusted as needed to adapt to different distances and positions. Moreover, there are fewer welding process defects in the adapter piece, which can help distribute the current more evenly, reduce local overheating and potential difference, and extend the service life of the battery.

[0253] In some embodiments, referring to Figure 14 , there is a direct electrical connection between the terminal post 105 and the tab. Thus, it helps to reduce the structural complexity inside the battery cell, helps to reduce the volume of the battery cell, and improve the energy density.

[0254] When there is a direct electrical connection between the terminal post and the tab, the connecting piece is omitted, simplifying the internal structure of the battery cell, reducing the assembly steps, and lowering the overall manufacturing cost.

[0255] In some embodiments, the above-mentioned battery cells can also be directly assembled into a battery pack, omitting the structure of the battery module and enhancing the energy density of the battery. The number of battery cells contained in the battery pack can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0256] In some embodiments, the distance between the two first shell walls 101 is D, and D is less than or equal to 30 mm. Thus, it is beneficial to the rapid heat dissipation of the battery cell.

[0257] Under fast charging conditions, both the charging current and voltage flowing through the battery cell will increase accordingly. According to Joule's law, the generated heat will also increase significantly. For a long-strip battery cell, the first shell wall is the surface with the largest area of the battery cell, so the heat dissipation effect near the first shell wall of the battery cell is better. However, in the thickness direction of the battery cell, that is, the width direction of the third shell wall, the heat diffusion inside the battery cell is slower. When the distance D between the two first shell walls 101 is within the aforementioned range, the heat dissipation effect of the battery cell in the thickness direction is better, which is beneficial to achieving good heat dissipation under fast charging and enhancing the fast charging performance of the battery cell.

[0258] In some embodiments, D is 10 mm - 25 mm. Thus, the battery cell has relatively high mechanical strength and excellent heat dissipation ability.

[0259] As an example, D can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm or 30 mm.

[0260] In some embodiments, the thicknesses of the first shell wall 101 and the third shell wall 103 are each independently less than or equal to 0.5 mm. Thus, the volumetric energy density of the battery cell can be improved.

[0261] When the thicknesses of the first shell wall 101 and the third shell wall 103 are within the aforementioned range, the shell walls are relatively thin and the weight of the housing is relatively light, which is beneficial to improving the mass energy density and volume energy density of the battery cell.

[0262] As an example, the thicknesses of the first shell wall 101 and the third shell wall 103 can be the same.

[0263] In some embodiments, the first shell wall 101 and the third shell wall 103 include at least one of an aluminum shell and a steel shell. Thereby, the mechanical strength of the battery cell can be improved.

[0264] At the same thickness, the mechanical strength of the steel shell is greater than that of the aluminum shell, which can better confine the electrode assembly and relieve the expansion of the battery cell during charge and discharge.

[0265] At the same thickness, the density of the aluminum shell is lighter than that of the steel shell, the weight of the housing is further reduced, and the mass energy density of the battery cell is further improved.

[0266] In some embodiments, the first shell wall 101 and the third shell wall 103 are steel shells, and the wall thickness of the steel shell is 0.1 mm - 0.5 mm. Thereby, the volume expansion of the battery cell during charge and discharge can be effectively relieved.

[0267] In some embodiments, the first shell wall 101 and the third shell wall 103 are aluminum shells, and the wall thickness of the aluminum shell is 0.3 mm - 0.4 mm. Thereby, the mass energy density of the battery cell can be effectively improved.

[0268] In some embodiments, the first shell wall 101 and the third shell wall 103 are obtained by bending and welding aluminum plates, and the weld of the welding is located at the connection of the first shell wall 101 and the third shell wall 103. Thereby, the leakage of the electrolyte can be reduced.

[0269] The aluminum shell obtained by bending and laser welding aluminum plates has excellent sealing effect, can effectively prevent the leakage of the electrolyte, improve the stability of the internal environment of the battery cell, and improve the cycle life of the battery cell.

[0270] In some embodiments, when the organic solvent in the electrolyte is mainly a low-viscosity solvent, the overall electrolyte also shows a low viscosity. The low-viscosity electrolyte is prone to decompose and generate gas during high-rate charge and discharge, resulting in the expansion of the battery cell. As a mechanical weak point, the weld may crack in extreme cases. To prevent the rapid deterioration caused by the leakage of the electrolyte after the weld cracks, the weld can be located at the connection of the third shell wall and the first shell wall far from the ground. Thus, after the weld cracks, the electrolyte is still not easy to flow out of the battery cell, effectively suppressing the rapid deterioration of the battery condition.

[0271] In some embodiments, a side support plate is provided between the electrode assembly and the first housing wall 101. Thereby, it helps to improve the structural stability of the battery cell.

[0272] The side support plate can block the direct contact between the electrode and the housing, reducing the damage to the electrode caused by the rounded corners at the edges of the inner wall of the housing.

[0273] In some embodiments, a pressure relief portion 104 is provided on at least one of the second housing walls 102. The pressure relief portion 104 is configured to be able to release the pressure inside the housing. The area of the orthographic projection of the pressure relief portion 104 on the second housing wall 102 is 7% - 15% of the area of the second housing wall 102. Thereby, it helps to quickly release the internal overpressure gas through the pressure relief portion 104 when the pressure inside the battery cell is too high.

[0274] As an example, the area of the pressure relief portion can be 155 mm 2 , and the area of the second housing wall can be 1920 mm 2 .

[0275] When the area of the orthographic projection of the pressure relief portion 104 on the second housing wall 102 is within the aforementioned range, the pressure relief portion can not only respond quickly when the internal pressure of the battery cell suddenly increases, break to release the internal pressure, but also occupy less space on the second housing wall, facilitating the arrangement of other structural components on the second housing wall.

[0276] In some embodiments, the capacity of the battery cell is Q, and the area of the orthographic projection of the pressure relief portion 104 on the second housing wall 102 is P. The ratio of P to Q is greater than or equal to 1.1. The unit of Q is Ah, and the unit of P is mm 2 . Thereby, it helps to quickly release the internal overpressure gas inside the battery cell.

[0277] When the capacity of the battery cell is relatively large, the content of low-viscosity electrolyte inside the battery is correspondingly higher, and the gas generation amount per unit time during high-rate charge and discharge is larger. In addition, lithium bis(fluorosulfonyl)imide will also have a gas generation side reaction with the negative electrode active material layer in the fully charged state. Therefore, a pressure relief portion with a larger area is required to provide more exhaust space, so as to quickly respond at the initial stage when the internal pressure of the battery cell suddenly increases and break to release the internal pressure. When the ratio of P to Q is within the aforementioned range, the area of the pressure relief portion matches the capacity of the battery, and can meet the pressure relief requirements of battery cells with corresponding capacities.

[0278] In some embodiments, pressure relief portions can be provided on both of the second housing walls. The proportional relationship between the area of the pressure relief portion and the area of the second housing wall can refer to the foregoing content.

[0279] In the second aspect of the present application, a battery device is proposed, including the aforementioned battery cell. The battery device can be a battery module, a battery pack, an energy storage device, etc. Thus, the battery device has all the features and advantages of the aforementioned battery cell, which will not be elaborated here.

[0280] In the third aspect of the present application, an electrical device is proposed, including the aforementioned battery cell. Thus, the electrical device has all the features and advantages of the aforementioned battery cell, which will not be elaborated here.

[0281] The aforementioned battery cell or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can 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, satellites, energy storage systems, etc., but not limited thereto.

[0282] As the electrical device, the battery cell or battery pack can be selected according to its usage requirements.

[0283] Figure 15 Here is an example of an electrical device. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery pack can be used.

[0284] The solution of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product instructions. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0285] Example 1 1) Preparation of the positive electrode sheet The positive electrode plate includes a positive current collector aluminum foil and a positive active material layer. The positive active material layer is formed by uniformly coating a positive electrode paste (with N-methylpyrrolidone as the solvent) on the surface of the positive current collector aluminum foil, and then drying and cold pressing to form a film layer. The positive active material layer includes a positive active material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) with a weight ratio of 97.5:1.4:1.1. The positive active material is lithium iron phosphate containing phosphorus and including aluminum, titanium, and vanadium, where the mass fractions of aluminum, titanium, and vanadium are 0.012%, 0.025%, and 0.025% respectively. In the cross-section of the positive active material layer along the thickness direction, the positive active material includes lithium phosphate with an olivine structure having a longest diameter of 2.5 μm and lithium phosphate with an olivine structure having a shortest diameter of 0.2 μm. Among them, the total width of the positive electrode tab accounts for 50% of the total width of the positive electrode main body, and the coating weight of a single-layer positive active material layer is 0.283 g / 1540.25 mm 2 , and the tap density of the positive active material layer is 2.45 g / cm 3 .

[0286] 2) Preparation of the negative electrode plate The negative electrode plate includes a negative current collector copper foil and a negative active material layer. The negative active material layer is formed by uniformly coating a negative electrode paste (with deionized water as the solvent) on the surface of the negative current collector copper foil, and then drying and cold pressing to form a film layer. The negative active material layer includes a negative active material, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na), and conductive carbon black (Super P) with a weight ratio of 96.2:1.8:1.2:0.8. The negative active material is single-layer graphite. The Dv50 particle size of the negative active material is 10.5 μm. Among them, the total width of the negative electrode tab accounts for 50% of the total width of the negative electrode main body, and the coating weight of a single-layer negative active material layer is 0.127 g / 1540.25 mm 2 , and the tap density of the negative active material layer is 1.45 g / cm 3 .

[0287] 3) Separator The separator is a porous polypropylene (PP) membrane.

[0288] 4) Preparation of the electrolyte The organic solvent substances in the electrolyte and their proportion are EA / DMC / EC = 10 / 55 / 35, and the electrolyte lithium salt in the electrolyte is lithium hexafluorophosphate with a mass content of 12.5%.

[0289] 5) Preparation of the battery The lithium-ion battery includes a housing, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are disposed within the housing. The electrode assembly includes a positive electrode tab, a negative electrode tab, and a separator. The electrode assembly is a wound electrode assembly, and the separator is disposed between the positive electrode tab and the negative electrode tab. The length L of the battery cell is 510 m, the width H of the battery cell is 120 mm, and the thickness D of the battery cell is 16 mm.

[0290] For the differences between the remaining embodiments and Embodiment 1, refer to Tables 1 - 5.

[0291] Table 1

[0292] Table 2

[0293] Table 3

[0294] Table 4

[0295] Table 5

[0296] Comparative Example 1 Comparative Example 1 is consistent with Embodiment 1. The difference is that the total width of the positive electrode ear portion accounts for 30% of the total width of the positive electrode main body portion, the total width of the negative electrode ear portion accounts for 30% of the total width of the negative electrode main body portion, the coating weight of the single-layer positive electrode active material layer is 0.25 g / 1540.25 mm 2 , and the coating weight of the single-layer negative electrode active material layer is 0.1 g / 1540.25 mm 2 , and the organic solvent substances and their proportion in the electrolyte are EA / EC = 90 / 10.

[0297] Comparative Example 2 Comparative Example 2 is consistent with Embodiment 1. The difference is that the coating weight of the single-layer positive electrode active material layer is 0.3 g / 1540.25 mm 2 , and the coating weight of the single-layer negative electrode active material layer is 0.145 g / 1540.25 mm 2 , and the organic solvent substances and their proportion in the electrolyte are DMC / EC = 60 / 40.

[0298] Comparative Example 3 Comparative Example 3 is consistent with Embodiment 1. The difference is that the total width of the positive electrode ear portion accounts for 100% of the total width of the positive electrode main body portion, the total width of the negative electrode ear portion accounts for 100% of the total width of the negative electrode main body portion, and the coating weight of the single-layer positive electrode active material layer is 0.31 g / 1540.25 mm2 The coating weight of the single-layer negative electrode active material layer is 0.16 g / 1540.25 mm 2 In the electrolyte, the organic solvent substance and the proportion are EA / EC = 90 / 10.

[0299] The fast charging performance of the batteries in Examples 1-10 and Comparative Examples 1-3 was tested. The test method is as follows, and the test results are shown in Table 1-1.

[0300] Charging time test: ① Voltage calibration: 1) The positive electrode sheet, negative electrode sheet, separator, and electrolyte in the example or comparative example were prepared into a laminated three-electrode battery and left to stand at 25°C for 30 min; 2) At 25°C, the battery cell was charged to the charging cut-off voltage of 3.65 V at 0.33C, and then constant voltage charging was continued at this charging cut-off voltage until the current was 0.05C, and the charging was cut off (where C represents the rated capacity of the battery cell); 3) Left to stand at 25°C for 1 h; 4) At 25°C, the battery cell was discharged to the discharge cut-off voltage of 2.5 V at 0.33C, and the total discharge capacity C0 discharged by the battery cell was recorded; 5) Left to stand at 25°C for 1 h. ② Normal temperature charging test: 1) The positive electrode sheet, negative electrode sheet, separator, and electrolyte in the example or comparative example were prepared into a laminated three-electrode battery and left to stand for 30 min; 2) Discharge to the discharge cut-off voltage of 2.5 V at 0.33C0 DC, corresponding to 0% SOC at this time; 3) Left to stand for 5 min; 4) Charge at 5C0 constant current until the negative electrode potential is 0 V, and read the capacity C1 at this time, corresponding to C1 / C0 SOC at this time; 5) Left to stand for 5 min; 6) Charge at 4.5C0 constant current until the negative electrode potential is 0 V, and read the capacity C2 at this time, corresponding to C2 / C0 SOC at this time; 7) Left to stand for 5 min; 8) Charge at 4C0 constant current until the negative electrode potential is 0 V, and read the capacity C3 at this time, corresponding to C3 / C0 SOC at this time; 9) Left to stand for 5 min; 10) Charge at 3C0 constant current until the negative electrode potential is 0 V, and read the capacity C4 at this time, corresponding to C4 / C0 SOC at this time; 11) Left to stand for 5 min; 12) Charge at 2C0 constant current until the negative electrode potential is 0 V, and read the capacity C5 at this time, corresponding to C5 / C0 SOC at this time; 13) Left to stand for 5 min; 14) Charge at 1C0 constant current until the negative electrode potential is 0 V, and read the capacity C6 at this time, corresponding to C6 / C0 SOC at this time; 15) Left to stand for 5 min; 16) Charge at 0.8C0 constant current until the negative electrode potential is 0 V, and read the capacity C7 at this time, corresponding to C7 / C0 SOC at this time; 17) Left to stand for 5 min; 18) Charge at 0.5C0 constant current until the negative electrode potential is 0 V, and read the capacity C8 at this time, corresponding to C8 / C0 SOC at this time; 19) Left to stand for 5 min; 20) Charge at 0.33C0 constant current until the negative electrode potential is 0 V, and read the capacity C9 (i.e., C0) at this time, corresponding to 100% SOC. The required charging time is obtained by adding up the total charging time during the charging process from 10% SOC to 80% SOC.

[0301] Temperature rise test: Arrange a temperature-sensing wire at any position on the top cover sheet of the battery cell to monitor the top cover temperature, and then perform the following charging process on the battery cell: 1) Discharge the battery cell of the example or comparative example at 0.33C DC to the discharge cut-off voltage of 2.5V, corresponding to 0% SOC at this time; 2) Stand still for 5 min, and charge at a constant current of 5C to C1 / CSOC (the value of C1 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 3) Stand still for 5 min, and charge at a constant current of 4.5C to C2 / CSOC (the value of C2 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 4) Stand still for 5 min, and charge at a constant current of 4C to C3 / CSOC (the value of C3 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 5) Stand still for 5 min, and charge at a constant current of 3C to C4 / CSOC (the value of C4 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 6) Stand still for 5 min, and charge at a constant current of 2C to C5 / CSOC (the value of C5 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 7) Stand still for 5 min, and charge at a constant current of 1C to C6 / CSOC (the value of C6 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 8) Stand still for 5 min, and charge at a constant current of 0.8C to C7 / CSOC (the value of C7 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 9) Stand still for 5 min, and charge at a constant current of 0.5C to C8 / CSOC (the value of C8 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell); 10) Stand still for 5 min, and charge at a constant current of 0.33C to C9 / CSOC (the value of C9 is the capacity corresponding to the negative electrode delithiation window test of the laminated three-electrode battery, and C represents the rated capacity of the battery cell). At this time, the battery cell reaches the full charge state, that is, 100% SOC; Monitor the temperature rise of the battery cell during charging from 10% SOC to 80% SOC and record it.

[0302] Perform a cycle performance test on the battery cells in Example 1 and Examples 11-13. The test method is as follows, and the test results are shown in Tables 1-2.

[0303] Cycle life: At 45 °C, charge the single battery at a constant current of 1C until the cut-off voltage of 3.65V, then charge at a constant voltage until 0.05C, set aside for 10 min, discharge at a constant current of 1C until 2.5V, and repeat this step until the capacity retention rate decays to 80% and then stop, and record the number of cycles at this time.

[0304] Table 1-1

[0305] Table 1-2

[0306] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same effect within the technical scope of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A battery cell, wherein: include: An electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet, wherein: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode current collector comprises a positive electrode main body and at least one positive electrode ear portion, the ear connection edge of the positive electrode main body is connected to the positive electrode ear portion, and along the direction in which the ear connection edge extends, the total width of the positive electrode ear portion accounts for 50%-100% of the total size of the ear connection edge of the positive electrode main body, The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, the negative electrode current collector comprises a negative electrode main body and at least one negative electrode ear portion, the ear connection edge of the negative electrode main body is connected to the negative electrode ear portion, and along the direction in which the ear connection edge extends, the total width of the negative electrode ear portion accounts for 50%-100% of the total size of the ear connection edge of the negative electrode main body, wherein the coating weight of a single layer of the negative electrode active material layer is 0.1g / 1540.25mm 2 -0.145 g / 1540.25 mm 2 , An electrolyte, wherein the electrolyte comprises an organic solvent, the organic solvent comprises a first solvent, the first solvent comprises at least one of dimethyl carbonate and a linear carboxylic acid ester, wherein the linear carboxylic acid ester has a structural formula satisfying R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl groups; based on the total mass of the electrolyte, the mass fraction of the first solvent is 4%-72%.

2. The battery cell according to claim 1, wherein: The total width of the positive pole ear is 40mm-160mm; and / or, the total width of the negative pole ear is 40mm-160mm; and / or, the width of the positive pole ear is 40mm-160mm; and / or, the width of the negative pole ear is 40mm-160mm.

3. The battery cell according to claim 1 or 2, wherein: The positive electrode ear portion and the negative electrode ear portion are located on the same side of the positive electrode main body portion, or the positive electrode ear portion and the negative electrode ear portion are located on two opposite sides of the positive electrode main body portion.

4. The battery cell according to claim 1, wherein: The positive electrode current collector includes the positive electrode main body and multiple positive electrode ear portions, and at least two of the positive electrode ear portions are located on two opposite sides of the positive electrode main body; and / or, the negative electrode current collector includes the negative electrode main body and multiple negative electrode ear portions, and at least two of the negative electrode ear portions are located on two opposite sides of the negative electrode main body.

5. The battery cell according to claim 1, wherein: The positive electrode current collector includes the positive electrode main body and a plurality of positive electrode tabs arranged at intervals; and / or the negative electrode current collector includes the negative electrode main body and a plurality of negative electrode tabs arranged at intervals.

6. The battery cell according to claim 1, wherein: The coating weight of the single layer of the negative electrode active material layer is 0.1g / 1540.25mm 2 -0.135g / 1540.25mm 2 .

7. The battery cell according to claim 6, wherein: The time for charging the battery from 10% SOC to 80% SOC is 7min-15min.

8. The battery cell according to claim 1, wherein: The coating weight of the single layer of the negative electrode active material layer is 0.136g / 1540.25mm 2 -0.145g / 1540.25mm 2 .

9. The battery cell according to claim 8, wherein: The time for charging the battery from 10% SOC to 80% SOC is 20min-30min.

10. The battery cell according to claim 1, wherein: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer at least located on one side of the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.2 g / cm3-1.5 g / cm 3 .

11. The battery cell according to claim 10, wherein: The negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the negative electrode active material is 0.1%-7%.

12. The battery cell according to claim 11, wherein: The mass fraction of silicon in the negative electrode active material is 1%-5%.

13. The battery cell according to claim 10, wherein: The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer which are stacked, the first negative electrode active material layer is located on a side close to the negative electrode current collector, the Dv50 of the first negative electrode active material in the first negative electrode active material layer is 9.2 μm-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2 μm-15.5 μm.

14. The battery cell according to claim 1, wherein: The conductivity of the electrolyte is 10 ms / cm-20 ms / cm.

15. The battery cell according to claim 1, wherein: Based on the total mass of the electrolyte, the mass fraction of the first solvent is 16%-72%.

16. The battery cell according to claim 1, wherein: Based on the total mass of the electrolyte, the mass fraction of the linear carboxylic acid ester is 32%-68%.

17. The battery cell according to claim 1, wherein: The electrolyte further includes a first lithium salt additive, which includes at least one of a fluorine-containing borate and a fluorine-containing phosphate. Based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.05%-0.5%.

18. The battery cell according to claim 17, wherein: The first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorooxalatephosphate, lithium difluorooxalateborate, and lithium tetrafluoroborate.

19. The battery cell according to claim 17, wherein: Based on the total mass of the electrolyte, the mass fraction of the first lithium salt additive is 0.1%-0.3%.

20. The battery cell according to claim 1, wherein: The organic solvent further includes a second solvent, and the second solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

21. The battery cell according to claim 20, wherein: The second solvent includes diethyl carbonate, and the mass fraction of the diethyl carbonate is greater than or equal to 12% based on the total mass of the electrolyte.

22. The battery cell according to claim 1, wherein: The electrolyte further includes non-lithium salt additives, and the non-lithium salt additives include sulfate additives and carbonate additives.

23. The battery cell according to claim 22, wherein: The carbonate additive includes at least one of vinylene carbonate, fluoroethylene carbonate and vinyl ethylene carbonate.

24. The battery cell according to claim 23, wherein: Based on the total mass of the electrolyte, the mass fraction of the vinylene carbonate is 0.5%-2.5%, and / or the mass fraction of the fluoroethylene carbonate is 0.05%-2%.

25. The battery cell according to claim 22, wherein: The sulfate ester additive includes at least one of 4,4-ethylene sulfate, vinyl disulfate, vinyl cyclotrisulfate, and 1,3-propane sultone.

26. The battery cell according to claim 22, wherein: Based on the total mass of the electrolyte, the mass fraction of the non-lithium salt additive is 0.05%-3%.

27. The battery cell according to claim 1, wherein: The electrolyte also includes a second lithium salt additive, which includes at least one of lithium bis(oxalatoborate), lithium difluorobis(oxalatephosphate), lithium tetrafluorooxalatephosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate.

28. The battery cell according to claim 1, wherein: The electrolyte also includes an electrolyte lithium salt, which includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte, the mass fraction of the electrolyte lithium salt is greater than or equal to 13%.

29. The battery cell according to claim 28, wherein: The electrolyte lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide in the electrolyte is (1.2-2):

1.

30. The battery cell according to claim 1, wherein: The compaction density of the positive electrode active material layer is 2.2 g / cm 3 -2.6g / cm 3 .

31. The battery cell according to claim 1, wherein: The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes: a core portion, the core portion comprising an olivine-structured lithium-containing phosphate, and The coating layer is coated on the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

32. The battery cell according to claim 31, wherein: The olivine-structured lithium-containing phosphate includes a general formula of Li x1 A y1 Me a M1 b P 1-c X c Y z A compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M1 includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F.

33. The battery cell according to claim 31 or 32, wherein: The coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.

32.

34. The battery cell according to claim 31, wherein: In a cross section of the positive electrode active material layer along a thickness direction, the positive electrode active material includes an olivine structured lithium-containing phosphate having a longest diameter of 1 μm to 3 μm and an olivine structured lithium-containing phosphate having a shortest diameter of 0.1 μm to 0.3 μm.

35. The battery cell according to claim 31, wherein: The positive electrode active material satisfies at least one of the following conditions: The Dv50 particle size of the positive electrode active material is 1 μm-5 μm; The Dv10 particle size of the positive electrode active material is 0.4 μm-0.7 μm; The positive electrode active material is a primary particle or a quasi-single crystal particle.

36. The battery cell according to claim 31, wherein: The positive electrode active material layer also includes a lithium-rich material, and the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, lithium nickel copperate, lithium phosphate, dilithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, and lithium nickel cobalt manganese oxide.

37. The battery cell according to claim 1, wherein: The length of the battery cell is L, the width of the battery cell is H, and the value of L is 4 to 10 times the value of H.

38. The battery cell according to claim 37, wherein: The value of L is 4 to 7 times the value of H.

39. The battery cell according to claim 37 or 38, wherein: L is 400mm-1000mm, and / or H is 80mm-160mm.

40. The battery cell according to claim 1, wherein: It also includes a shell, the electrode assembly is located in the shell, the shell includes two first shell walls arranged opposite to each other, and a surrounding wall connecting the two first shell walls, the surrounding wall includes: two second shell walls arranged opposite to each other along the length direction of the first shell walls, two third shell walls arranged opposite to each other along the width direction of the first shell walls, the second shell walls are provided with electrode terminals, the positive electrode ear portion and the negative electrode ear portion are electrically connected to the electrode terminals on the two second shell walls respectively, wherein a retracting structure is provided between the second shell wall electrically connected to the positive electrode ear portion and the positive electrode main body portion, and the retracting structure is configured to retract the plurality of positive electrode ears.

41. The battery cell according to claim 40, wherein: In the length direction of the first shell wall, the edge of the positive electrode sheet is chamfered.

42. The battery cell according to claim 40 or 41, wherein: A liquid injection hole is provided on the second shell wall connected to the negative electrode ear portion.

43. The battery cell according to claim 42, wherein: The liquid injection hole and the pressure relief portion of the shell are located on different second shell walls, and the pressure relief portion is configured to release the pressure inside the shell.

44. The battery cell according to claim 40, wherein: At least one mounting hole is provided on the electrode terminal, and the pole is passed through the mounting hole and riveted to the pole ear.

45. The battery cell according to claim 40, wherein: The electrode terminal is provided with at least two mounting holes, and each pole is passed through the mounting holes and riveted to the pole ear portion.

46. ​​The battery cell according to claim 44 or 45, wherein: The diameter of the pole is 3mm-8mm.

47. The battery cell according to claim 44 or 45, wherein: The pole riveted to the positive pole ear portion and the pole riveted to the negative pole ear portion are staggered in the length direction of the first shell wall.

48. The battery cell according to claim 44 or 45, wherein: The pole riveted to the positive electrode ear portion and the pole riveted to the negative electrode ear portion are arranged diagonally in the length direction of the first shell wall.

49. The battery cell according to claim 44 or 45, wherein: The pole and the tab are electrically connected via a switching plate.

50. The battery cell according to claim 44 or 45, wherein: The pole is directly electrically connected to the pole lug.

51. The battery cell according to claim 40, wherein: The distance between the two first shell walls is D, which is less than or equal to 30 mm.

52. The battery cell according to claim 51, wherein: D is 10mm-25mm.

53. The battery cell according to claim 40, wherein: The thickness of the first shell wall and the third shell wall are independently less than or equal to 0.5 mm.

54. The battery cell according to claim 53, wherein: The first shell wall and the third shell wall include at least one of an aluminum shell and a steel shell.

55. The battery cell according to claim 54, wherein: The first shell wall and the third shell wall are steel shells, and the wall thickness of the steel shells is 0.1mm-0.5mm.

56. The battery cell according to claim 54, wherein: The first shell wall and the third shell wall are aluminum shells, and the wall thickness of the aluminum shells is 0.3mm-0.4mm.

57. The battery cell according to claim 56, wherein: The first shell wall and the third shell wall are obtained by bending and welding aluminum plates, and the welding seam is located at the connection between the first shell wall and the third shell wall.

58. The battery cell according to claim 40, wherein: A side support plate is provided between the electrode assembly and the first shell wall.

59. The battery cell according to claim 40, wherein: At least one of the second shell walls is provided with a pressure relief portion, and the pressure relief portion is configured to release the pressure inside the shell, and the area of ​​the positive projection of the pressure relief portion on the second shell wall is 7%-15% of the area of ​​the second shell wall.

60. The battery cell according to claim 59, wherein: The capacity of the battery is Q, the ratio of the area of ​​the orthographic projection of the pressure relief portion on the second shell wall to Q is greater than or equal to 1.1, the unit of Q is Ah, and the unit of the area is mm 2 .

61. A battery device, wherein: Comprising the battery cell described in any one of claims 1-60, the battery device comprises at least one of a battery module, a battery pack, and an energy storage device.

62. An electrical device, wherein: A battery cell comprising the battery cell according to any one of claims 1 to 60.

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