Battery cell, battery device and electric device

Abstract

Provided in the present disclosure are a battery cell, a battery device and an electric device. The length of the battery cell is L, and the width of the battery cell is H, wherein the value of L is 4 to 10 times that of H. The battery cell comprises an electrolyte, wherein a first lithium salt additive in the electrolyte comprises at least one of a fluorinated borate and a fluorinated phosphate, and the mass fraction of the first lithium salt additive ranges from 0.01% to 0.5%.

Description

Battery monomer, battery device, and electric device TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery monomer, a battery device, and an electric device. BACKGROUND

[0002] Lithium ion batteries have been widely applied in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, and electric vehicles. As the application range of batteries gradually expands, the market has higher requirements for the performance of batteries. However, the current batteries still have many deficiencies in the application process, and the fast charging performance needs to be further improved.

[0003] It should be noted that the above statements are only used to provide background technical information related to the present application, and do not necessarily constitute the prior art.

[0004] SUMMARY

[0005] In a first aspect of the present application, a battery monomer is provided, the length of the battery monomer is L, the width of the battery monomer is H, the value of L is 4 to 10 times the value of H; the battery monomer comprises an electrolyte, the electrolyte comprises an organic solvent and a first lithium salt additive, the first lithium salt additive comprises at least one of a fluorine-containing borate and a fluorine-containing phosphate, and the mass fraction of the first lithium salt additive is 0.01%-0.5% based on the total mass of the electrolyte. Thus, by adding the first lithium salt additive, the internal resistance of the battery monomer can be effectively reduced, so that the battery monomer has both high energy density and fast charging performance.

[0006] In some embodiments, the value of L is 4 to 7 times the value of H. Thus, it helps the battery monomer to have both high energy density and low internal resistance.

[0007] In some embodiments, L is 400mm-1000mm, and / or H is 80mm-160mm.

[0008] In some embodiments, the first lithium salt additive comprises at least one of lithium difluorophosphate, lithium difluoro oxalate phosphate, lithium difluoro oxalate borate, and lithium tetrafluoroborate. Thus, it helps to form a low-impedance solid-state electrolyte film on the surface of the negative active material.

[0009] In some embodiments, the mass fraction of the first lithium salt additive in the electrolyte is 0.05%-0.5%, and optionally 0.1%-0.3%. Thus, it helps to reduce the cost of the battery monomer.

[0010] In some embodiments, the electrolyte has an electrical conductivity of 10 ms / cm-20 ms / cm. Thus, the fast-charging performance of the battery cell is improved.

[0011] In some embodiments, the organic solvent comprises a first solvent, and the first solvent comprises at least one of dimethyl carbonate and linear carboxylate, wherein a structural formula of the linear carboxylate satisfies R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl. Thus, the viscosity of the electrolyte can be effectively reduced.

[0012] In some embodiments, the linear carboxylate comprises at least one of ethyl formate, isopropyl formate, ethyl acetate, methyl acetate, propyl acetate, and methyl propionate. Thus, the viscosity of the electrolyte can be further reduced.

[0013] In some embodiments, the mass fraction of the linear carboxylate is 32%-68% based on the total mass of the electrolyte.

[0014] In some embodiments, the mass fraction of the first solvent is greater than or equal to 4% based on the total mass of the organic solvent and the total mass of the electrolyte, and optionally, the mass fraction of the first solvent is 16%-80% based on the total mass of the electrolyte.

[0015] In some embodiments, the organic solvent further comprises a second solvent, and the second solvent comprises at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate. Thus, the cycle life of the battery cell is improved.

[0016] In some embodiments, the second solvent comprises diethyl carbonate, and the content of the diethyl carbonate is not less than 15% based on the total mass of the organic solvent.

[0017] In some embodiments, the electrolyte further comprises a non-lithium salt additive, and the non-lithium salt additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate. Thus, a dense and stable solid electrolyte film is formed on the surface of the negative active material.

[0018] In some embodiments, 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% based on the total mass of the electrolyte. Thus, a dense and stable solid electrolyte film is formed on the surface of the negative active material.

[0019] In some embodiments, the electrolyte further comprises a second lithium salt additive, the second lithium salt additive comprising at least one of lithium bis(oxalato)borate, lithium difluorodioxalate phosphate, lithium tetrafluorodioxalate phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium perchlorate. Thereby, it is helpful to form a solid electrolyte film with high ionic conductivity on the surface of the negative active material.

[0020] In some embodiments, the electrolyte further comprises an electrolyte lithium salt, the electrolyte lithium salt comprising at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, the mass fraction of the electrolyte lithium salt being greater than or equal to 13% based on the total mass of the electrolyte. Thereby, it is helpful to improve the conductivity of the electrolyte.

[0021] In some embodiments, the electrolyte lithium salt comprises lithium hexafluorophosphate and lithium bisfluorosulfonylimide, the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonylimide in the electrolyte being (1.2-2):1. Thereby, it is helpful to further improve the conductivity of the electrolyte.

[0022] In some embodiments, further comprising a positive electrode tab, the positive electrode tab comprising a positive electrode current collector and a positive electrode active material layer at least on one side of the positive electrode current collector, the positive electrode active material layer having a compacted density of 2.2 g / cm 3 -2.6 g / cm 3 . Thereby, it is helpful to improve the fast charging performance of the battery cell.

[0023] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprising an olivine-structured lithium-containing phosphate or a modified material thereof. Thereby, it is helpful to improve the cycle life of the battery cell.

[0024] In some embodiments, the olivine-structured lithium-containing phosphate or the modified material thereof comprises: a core portion comprising an olivine-structured lithium-containing phosphate, and a coating layer coated on the surface of the olivine-structured lithium-containing phosphate, the coating layer containing one or more elements of C, Fe, Ti, Zr, Hf, Ge and Sn. Thereby, it is helpful to improve the structural stability and ionic conductivity of the positive electrode active material.

[0025] In some embodiments, the olivine-structured lithium-containing phosphate comprises a general formula of Li x A y Me a M b P 1-c X c Y zA compound of formula (I), wherein 0.5≤x≤1.3, 0≤y≤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 comprises one or more of Na, K, Mg; Me comprises one or more of Mn, Fe, Co, Ni; M comprises 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 comprises one or more of S, Si, Cl, B, C, N; Y comprises one or more of O, F. Thus, it is helpful to improve the ionic conductivity and electronic conductivity of the core.

[0026] In some embodiments, the coating layer comprises a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.32. Thus, it is helpful to improve the electronic conductivity of the positive electrode active material.

[0027] In some embodiments, in a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material comprises lithium-containing olivine phosphate with a longest diameter of 1-3 μm, and lithium-containing olivine phosphate with a shortest diameter of 0.1-0.3 μm. Thus, it is helpful to improve the energy density of the battery cell.

[0028] 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 1-5 μm; the Dv10 particle size of the positive electrode active material is 0.4-0.7 μm; the positive electrode active material is primary particles or quasi-single crystal particles. Thus, the particle size of the positive electrode active material is large, which is helpful to improve the energy density of the battery cell.

[0029] In some embodiments, the positive electrode active material layer further comprises a lithium-rich material, and the lithium-rich material comprises one or more 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 metamanganate, lithium tartrate, trilithium citrate, lithium nickel cobalt manganese acid. Thus, it is helpful to improve the cycle life of the battery cell.

[0030] In some embodiments, further comprising a negative electrode tab, and the negative electrode tab comprises 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 compaction density of the negative electrode active material layer is 1.2 g / cm 3 -1.5 cm 3 . Thus, it is helpful to improve the fast charging performance of the battery cell.

[0031] In some embodiments, the coating weight of a single layer of the negative active material layer is greater than or equal to 0.1 g / 15 40.25 mm 2 .

[0032] In some embodiments, the coating weight of a single layer of the negative active material layer is 0.1 g / 15 40.25 mm 2 -0.145 g / 15 40.25 mm 2 . Thus, the negative active material layer has both a high lithium ion deintercalation rate and a high energy density.

[0033] In some embodiments, the coating weight of a single layer of the negative active material layer is 0.1 g / 15 40.25 mm 2 -0.135 g / 15 40.25 mm 2 . Thus, the battery cell has a high volumetric energy density.

[0034] In some embodiments, the battery cell takes 7 min-15 min to charge from 10% SOC to 80% SOC. Thus, the battery cell has a high fast-charging performance.

[0035] In some embodiments, the coating weight of a single layer of the negative active material layer is 0.136 g / 15 40.25 mm 2 -0.145 g / 15 40.25 mm 2 . Thus, the battery cell has a high volumetric energy density.

[0036] In some embodiments, the battery cell takes 20 min-30 min to charge from 10% SOC to 80% SOC. Thus, the battery cell has a high fast-charging performance.

[0037] In some embodiments, the negative active material layer comprises a first negative active material layer and a second negative active material layer arranged in a stack, the first negative active material layer is located on the side close to the negative current collector, the Dv50 of the first negative active material in the first negative active material layer is 9.2 pm-18.5 pm, and the Dv50 of the second negative active material in the second negative active material layer is 7.2 pm-15.5 pm. Thus, the fast-charging performance of the battery cell can be significantly improved.

[0038] In some embodiments, the negative active material layer comprises a negative active material, the negative active material comprises a silicon-containing material, and the mass fraction of silicon in the silicon-containing material is 0.1%-7%. Thus, the mass energy density of the battery cell can be improved.

[0039] In some embodiments, the mass fraction of silicon in the silicon-containing material is 1-5%. In this way, the mass energy density of the battery cell can be further improved.

[0040] In some embodiments, the housing further comprises two first housing walls arranged opposite to each other, and a surrounding wall connecting the two first housing walls, the surrounding wall comprising two second housing walls arranged opposite to each other along the length direction of the first housing wall, and two third housing walls arranged opposite to each other along the width direction of the first housing wall, wherein the distance between the two first housing walls is D, and D is less than or equal to 30 mm. In this way, the rapid heat dissipation of the battery cell is facilitated.

[0041] In some embodiments, D is 10-25 mm. In this way, the battery cell has higher mechanical strength and better heat dissipation capacity.

[0042] In some embodiments, the thickness of the first housing wall and the third housing wall is independently less than or equal to 0.5 mm. In this way, the volume energy density of the battery cell can be improved.

[0043] In some embodiments, the first housing wall and the third housing wall comprise at least one of an aluminum shell and a steel shell. In this way, the mechanical strength of the battery cell can be improved.

[0044] In some embodiments, the first housing wall and the third housing wall are steel shells, and the wall thickness of the steel shell is 0.1-0.5 mm. In this way, the volume expansion of the battery cell during charging and discharging can be effectively alleviated.

[0045] In some embodiments, the first housing wall and the third housing wall are aluminum shells, and the wall thickness of the aluminum shell is 0.3-0.4 mm. In this way, the mass energy density of the battery cell can be effectively improved.

[0046] In some embodiments, the first housing wall and the third housing wall are obtained by bending and welding an aluminum plate, and the weld of the welding is located at the connection of the first housing wall and the third housing wall. In this way, the electrolyte leakage can be reduced.

[0047] In some embodiments, a side support plate is arranged between the electrode assembly and the first housing wall. In this way, the structural stability of the battery cell is improved.

[0048] In some embodiments, at least one of the second housing walls is provided with a pressure relief portion configured to release 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. In this way, when the internal pressure of the battery cell is too high, the internal overpressure gas can be quickly released through the pressure relief portion.

[0049] In some embodiments, the capacity of the battery cell is Q, the area of the normal projection of the pressure relief portion on the second shell wall is P, and 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 In this way, the rapid release of overpressure gas inside the battery cell is facilitated.

[0050] In some embodiments, the positive electrode tab 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 and at least one positive tab portion, and the positive main body portion is connected to the positive tab portion; the negative electrode tab 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 and at least one negative tab portion, and the negative main body portion is connected to the negative tab portion, the second shell wall is provided with an electrode terminal, and the positive tab portion and the negative tab portion are respectively electrically connected to the electrode terminal on the two second shell walls, wherein a folding structure is provided between the second shell wall electrically connected to the positive tab portion and the positive main body portion, and the folding structure is configured to fold the plurality of positive tab portions. In this way, the fixation of the positive tab and the welding between the positive electrode tab and the pole are facilitated.

[0051] In some embodiments, a chamfer is provided at the edge of the positive electrode tab along the length direction of the first shell wall. In this way, the rapid assembly of the electrode assembly is facilitated.

[0052] In some embodiments, the total width of the positive tab portion along the width direction of the positive main body portion accounts for 30%-100% of the total width of the positive main body portion; and / or, the total width of the negative tab portion along the width direction of the negative main body portion accounts for 30%-100% of the total width of the negative main body portion. In this way, the current-carrying capacity of the tab can be effectively improved.

[0053] In some embodiments, the size of the positive tab portion along the width direction of the positive main body portion is 50%-80% of the size of the positive main body portion. In this way, the positive tab has a better heat dissipation capacity.

[0054] In some embodiments, the second shell wall connected to the negative tab portion is provided with a liquid injection hole. In this way, the injection of electrolyte is facilitated.

[0055] In some embodiments, 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 be able to release the pressure inside the shell. In this way, the corrosion of the electrolyte on the pressure relief portion during the injection process can be reduced.

[0056] In some embodiments, at least one mounting hole is provided on the electrode terminal, and the pole post is arranged in the mounting hole and riveted with the tab. In this way, the volume of the battery cell can be reduced, the weight of the battery cell can be reduced, and the energy density of the battery cell can be improved.

[0057] In some embodiments, at least two mounting holes are provided on the electrode terminal, and each pole post is arranged in the mounting hole and riveted with the tab. In this way, the overcurrent capacity of the pole post can be improved.

[0058] In some embodiments, the diameter of the pole post is 3-8 mm. In this way, the pole post has both high overcurrent capacity and low space occupation.

[0059] In some embodiments, the pole post riveted with the positive tab and the pole post riveted with the negative tab are arranged in a staggered manner along the length direction of the first shell wall, and optionally, the pole post riveted with the positive tab and the pole post riveted with the negative tab are arranged in a diagonal manner along the length direction of the first shell wall. In this way, the volume energy density of the assembled battery module or battery pack can be improved.

[0060] In some embodiments, the pole post and the tab are electrically connected through a adapter plate. In this way, the welding quality and connection reliability between the pole post and the tab can be significantly improved.

[0061] In some embodiments, the pole post and the tab are directly electrically connected. In this way, the structural complexity inside the battery cell can be reduced, the volume of the battery cell can be reduced, and the energy density can be improved.

[0062] In a second aspect of the present application, a battery device is provided, which includes at least one of a battery module, a battery pack, and an energy storage device, and includes the battery cell as described above. In this way, the battery device has all the features and advantages of the battery cell as described above, which will not be repeated here.

[0063] In a third aspect of the present application, a power consumption device is provided, which includes the battery cell as described above. In this way, the power consumption device has all the features and advantages of the battery cell as described above, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0064] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the following drawings in which:

[0065] FIG. 1 is a structural schematic view of a battery cell according to an embodiment of the present application;

[0066] FIG. 2 is a structural schematic view of a positive current collector according to an embodiment of the present application;

[0067] Fig. 3 is a schematic view of a structure of a negative current collector according to an embodiment of the present application;

[0068] Fig. 4 is a schematic view of a partial structure of a case according to an embodiment of the present application;

[0069] Fig. 5 is a schematic view of a partial structure of a case according to another embodiment of the present application;

[0070] Fig. 6 is a schematic view of a partial structure of a case according to another embodiment of the present application;

[0071] Fig. 7 is a schematic view of a partial structure of a case according to another embodiment of the present application;

[0072] Fig. 8 is a schematic view of a partial structure of a case according to another embodiment of the present application;

[0073] Fig. 9 is a schematic view of a partial structure of a case according to another embodiment of the present application;

[0074] Fig. 10 is a schematic view of a partial structure of a case according to another embodiment of the present application;

[0075] Fig. 11 is a schematic view of a structure of an electric device according to an embodiment of the present application.

[0076] Explanation of Reference Numerals: 11 positive main body portion; 12 positive tab portion; 21 negative main body portion; 22 negative tab portion; 101 first case wall; 102 second case wall; 103 third case wall; 104 pressure relief portion; 105 pole; 106 folding structure; 107 liquid injection hole; 108 adapter piece. DETAILED DESCRIPTION

[0077] Embodiments of the present application will be described in detail below, examples of which are shown in the accompanying drawings, but there will be cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are well known, repeated description of practically identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy, facilitating understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0078] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; unless otherwise specified, numerical parameters recited in this application can be measured using various measuring methods commonly used in the art (for example, can be tested according to the methods given in the embodiments of the present application).

[0079] The terms "comprise" and "have" and any variations thereof in the specification and claims of this application are open-ended transitional phrases, i.e., including, but not limited to, whatever falling within the scope of the terms.

[0080] In the description of the application, whether using "about" or "approximately" or not, all the numbers disclosed herein are approximate values. The value of each number can have a difference of 10% or less, or a reasonable difference in the opinion of those skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0081] The "range" disclosed in the present application is defined in the form of lower limit and 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 be inclusive or exclusive of the end value, and can be arbitrarily combined, i.e. any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 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, 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 stated, the numerical range "a-b" represents a shorthand notation for any real combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is only a shorthand notation for these numerical combinations. In addition, when a parameter is stated to be ≥2 integers, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0082] In the description of the application, it is understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0083] In the description of the application, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. "First feature", "second feature" can include one or more of the features.

[0084] In the description of the application, the meaning of "multiple" is two or more.

[0085] In the description of the present application, "A and / or B" can include any one of the case of A alone, the case of B alone, the case of A and B, where A, B are used for example only, which can be any technical feature connected by "and / or" in the present application.

[0086] If there is no special description, all the embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0087] If there is no special description, all the technical features and optional technical features of the present application can be combined to form new technical solutions.

[0088] By flattening and lengthening the battery monomer, a thin and long shape is formed. The long strip-shaped battery monomer is arranged and combined directly to form a battery pack, which saves the intermediate module structure, can effectively improve the volume utilization rate of the battery pack, and improve the energy density of the battery monomer. Further, when the electrode assembly is formed by a lamination process, the positive electrode and the negative electrode of the battery monomer are arranged on both sides of the battery monomer along the length direction, which in turn causes the transmission path of lithium ions in the battery monomer, i.e. the distance that lithium ions move between the positive electrode and the negative electrode, to be significantly lengthened. The resulting problems include: the longer lithium ion transmission path increases the migration resistance of lithium ions in the electrolyte, increases the internal resistance of the battery monomer, and significantly affects the charge-discharge efficiency and instantaneous power output capability of the battery monomer. Specifically, the charge-discharge efficiency of the battery monomer reflects the energy utilization rate of the battery monomer during charging and discharging, i.e. the ratio of actual available energy to input or theoretical energy. When the charge-discharge efficiency of the battery monomer is low, it indicates that a large amount of heat and internal stress will be generated in the battery monomer during charging and discharging, thereby accelerating the aging of the battery monomer. The instantaneous power output capability refers to the maximum energy output rate that the battery monomer can provide in a short time. When the instantaneous power output capability of the battery monomer is weak, the battery monomer is difficult to charge and discharge at a large current in a short time, and the fast charging performance of the battery monomer is poor. By adding at least one lithium salt additive containing fluoroborate and fluorophosphate to the electrolyte of the battery monomer, a low-impedance SEI film (solid-state electrolyte film) containing boron atoms and phosphorus atoms is formed on the surface of the negative active material, effectively reducing the internal resistance of the battery monomer, so that the battery monomer has high energy density and fast charging performance.

[0089] The present application limits the relative values of the length and width of the battery within a reasonable range, and further controls the content of the electrolyte additive to limit the battery to have high assembly efficiency while also having good fast charging performance.

[0090] In a first aspect, the present application provides a battery cell, as shown in FIG. 1, the length of the battery cell is L, the width of the battery cell is H, the value of L is 4 to 10 times the value of H; the battery cell comprises an electrolyte, the electrolyte comprises an organic solvent and a first lithium salt additive, the first lithium salt additive comprises at least one of a fluorine-containing borate and a fluorine-containing phosphate, and the mass fraction of the first lithium salt additive is 0.01%-0.5% based on the total mass of the electrolyte. Thus, by adding the first lithium salt additive, the internal resistance of the battery cell can be effectively reduced, thereby making the battery cell have better charge-discharge efficiency and instantaneous power output capability, so that the battery cell has higher energy density and fast charging performance.

[0091] During the charge-discharge process of the battery cell, active ions are embedded and extracted between the positive and negative electrode sheets. The electrolyte plays a role in conducting ions between the positive and negative electrode sheets. The separator is arranged between the positive and negative electrode sheets, mainly to prevent short circuit between the positive and negative electrodes, and can also allow ions to pass through.

[0092] For 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.

[0093] When the proportional relationship between the value of L and the value of H is within the above range, it helps to improve the volume utilization of the battery pack formed by assembling the battery cell, and when a collision or external force impact occurs, the stress on the battery cell is more uniform and dispersed, effectively reducing the risk of short circuit.

[0094] In some embodiments, the value of L is 4 to 7 times the value of H. Thus, it helps the battery cell to have higher energy density and lower internal resistance.

[0095] In some embodiments, L is 400mm-1000mm, and / or H is 80mm-160mm.

[0096] For example, L can be 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, 750mm, 800mm, 850mm, 900mm, 950mm or 1000mm.

[0097] For example, H can be 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm.

[0098] When L and H are within the above numerical ranges, the size of the battery cell is moderate, which is conducive to transfer and rapid assembly, the transmission path of lithium ions in the battery cell is relatively short, and the internal resistance of the battery cell is small.

[0099] In the embodiments of the present application, the size of the battery cell does not include the size of the pole column protruding from the main body part of the battery cell.

[0100] For example, 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%, based on the total mass of the electrolyte.

[0101] When the mass fraction of the first lithium salt additive is within the above range, the first lithium salt additive helps to form a low-impedance SEI film on the surface of the negative active material, while the amount is small, which helps to reduce the cost of the electrolyte.

[0102] In some embodiments, when the aspect ratio L / H of the battery cell is high, the amount of the first lithium salt additive can also be added more within the above range accordingly, so as to help the battery cell have better energy density and fast charging performance.

[0103] For example, the mass fraction of the first lithium salt additive can be tested based on the total mass of the electrolyte by the following method: taking out the free electrolyte in the finished battery, and testing the content of the first lithium salt additive by ion chromatography. The concentration of the first lithium salt additive in the electrolyte can be quantitatively analyzed by ion chromatography analysis method according to standard JY / T020-1996.

[0104] In some embodiments, the first lithium salt additive includes at least one of lithium difluorophosphate, lithium difluorophosphate oxalate, lithium difluorophosphate oxalate borate, and lithium tetrafluoroborate. In this way, a low-impedance solid electrolyte film can be formed on the surface of the negative active material.

[0105] The first lithium salt additive itself has 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 active material during the first charging, which can not only reduce the side reaction between the negative active material and the electrolyte, but also reduce the internal resistance of the battery.

[0106] In some embodiments, the mass fraction of the first lithium salt additive in the electrolyte is 0.05%-0.5%, which can be optionally 0.1%-0.3%. In this way, the cost of the battery cell can be reduced.

[0107] The amount 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, the amount of the first lithium salt additive in the electrolyte needs to be increased accordingly, so as to reduce the internal resistance of the battery, thereby alleviating 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 have both low internal resistance and low manufacturing cost.

[0108] [Electrolyte]

[0109] In some embodiments, the conductivity of the electrolyte is 10 ms / cm-20 ms / cm. In this way, the fast charging performance of the battery cell is improved.

[0110] For 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.

[0111] When the conductivity of the electrolyte is within the range, the electrolyte can more effectively conduct lithium ions, thereby effectively reducing the internal resistance of the battery, improving the fast charging performance of the battery, reducing the temperature rise of the battery caused by the resistance heat effect during charging and discharging, reducing the thermal stress inside the battery cell, and further improving the performance of the battery under high power.

[0112] For example, the conductivity of the electrolyte can be directly tested by a conductivity meter.

[0113] 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, wherein the structural formula of the linear carboxylic acid ester satisfies R1-COO-R2, and R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl. In this way, the viscosity of the electrolyte can be effectively reduced.

[0114] The viscosity of the aforementioned first solvent is low, and thus the overall viscosity of the electrolyte mainly composed of the organic solvent is low. The intermolecular interaction in the low-viscosity electrolyte is weak, and the motion between molecules is more free, so that the diffusion and migration speed of lithium ions in the electrolyte is accelerated. Further, when the battery cell is subjected to fast charging and discharging, concentration polarization occurs inside the battery. When the ion migration rate of the electrolyte is high, the concentration polarization inside the battery can be alleviated. The aforementioned low-viscosity electrolyte can effectively reduce the concentration polarization by increasing the ion migration rate, thereby improving the fast charging performance of the battery.

[0115] As an example, the viscosity of the electrolyte can be tested by the following method: the viscosity is tested by a viscometer. Refer to the national standard GB / T 10247-2008 "Viscosity Measurement Method": under a certain temperature, the shear force received by the rotor in the sample when rotating at a constant speed continuously generates a torque on the spring, and the torque is proportional to the viscosity, and the viscosity value is obtained.

[0116] 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. In this way, the viscosity of the electrolyte can be further reduced.

[0117] The linear carboxylic acid ester has good lithium salt solubility, can improve 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. In addition, the linear carboxylic acid ester has 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.

[0118] In some embodiments, the mass fraction of the linear carboxylic acid ester based on the total mass of the organic solvent is 40%-85%.

[0119] As an example, the mass fraction of the linear carboxylic acid ester based on the total mass of the organic solvent can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%.

[0120] The linear carboxylic acid ester has a low viscosity, and when the mass fraction of the linear carboxylic acid ester based on the total mass of the organic solvent is within the above range, the liquid phase transmission resistance of lithium ions can be further reduced, and the fast charging performance and cycle performance of the battery cell can be improved.

[0121] In this application, the organic solvent in the electrolyte is defined as: an organic substance with a mass fraction greater than or equal to 5% based on the total mass of the electrolyte.

[0122] As an example, the mass fraction of the linear carboxylic acid ester based on the total mass of the organic solvent can be tested by the following method: the organic components in the electrolyte can be quantitatively analyzed by gas chromatography according to the standard GB / T 9722-2006.

[0123] In some embodiments, the mass fraction of the first solvent based on the total mass of the organic solvent is greater than or equal to 5%.

[0124] As an example, the mass fraction of the first solvent can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%, based on the total mass of the organic solvent.

[0125] With the increase of the mass fraction of the first solvent, the viscosity of the electrolyte gradually decreases, and the fast-charging performance of the battery is further improved.

[0126] As an example, the mass fraction of the first solvent can be tested by the following method: the organic components in the electrolyte can be quantitatively analyzed by gas chromatography according to the standard GB / T 9722-2006.

[0127] In some embodiments, the mass fraction of the first solvent is 20%-100%, based on the total mass of the organic solvent.

[0128] It can be understood that, in general, the electrolyte includes an organic solvent and a lithium salt (including an electrolyte lithium salt and a lithium salt additive), and the mass fraction of the organic solvent is about 80%, based on the total mass of the electrolyte, and the rest is the lithium salt. Therefore, even if the mass fraction of the first solvent is 100%, based on the total mass of the organic solvent, the mass fraction of the lithium salt in the electrolyte is about 20%, and the electrolyte can still provide a sufficient amount of lithium ions that can migrate between the positive and negative electrodes of the battery cell.

[0129] In some embodiments, the organic solvent further includes a second solvent, and the second solvent includes at least one of ethylene carbonate EC, propylene carbonate, methyl ethyl carbonate (EMC), diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate. In this way, the cycle life of the battery cell is improved.

[0130] The aforementioned second solvent has a wide electrochemical stability window and can remain stable in a high-voltage environment, thereby reducing its decomposition in electrochemical reactions and improving the cycle life of the battery cell.

[0131] In some embodiments, the second solvent includes diethyl carbonate, and the content of the diethyl carbonate is not less than 15%, based on the total mass of the organic solvent.

[0132] Diethyl carbonate has a suitable viscosity and boiling point, which helps to adjust the physical properties of the electrolyte, so that the electrolyte has a suitable viscosity and better low-temperature performance.

[0133] In some embodiments, the electrolyte further comprises a non-lithium salt additive, the non-lithium salt additive comprising at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate. Thereby, it is helpful to form a dense and stable solid electrolyte film on the surface of the negative active material.

[0134] The carbonate non-lithium salt additive containing double bond is helpful to form a SEI film with good flexibility on the surface of the negative active material, which can slow down the destruction of the interface film due to the volume cyclic expansion of the negative active material during the cyclic charge and discharge process, improve the cycle stability of the battery cell, and improve the cycle life.

[0135] In some embodiments, the non-lithium salt additive comprises vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0136] In some embodiments, 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% based on the total mass of the electrolyte. Thereby, it is helpful to form a dense and stable solid electrolyte film on the surface of the negative active material.

[0137] For example, the mass fraction of the vinylene carbonate is 0.5%, 1%, 1.5%, 2.0% or 2.5% based on the total mass of the electrolyte.

[0138] For example, the mass fraction of the fluoroethylene carbonate is 0.05%, 0.1%, 0.5%, 1%, 1.5% or 2.0% based on the total mass of the electrolyte.

[0139] It can be understood that since the carbonate non-lithium salt additive containing double bond will participate in the formation of the SEI film on the surface of the negative active material during the formation process, it will be partially consumed, so the actual detected amount of the above-mentioned substance in the battery cell will be slightly less than its added amount. For example, when the added amount of vinylene carbonate is 2.0% based on the total mass of the electrolyte, its actual detected amount in the battery cell is about 0.87%; when the added amount of fluoroethylene carbonate is 1.3% based on the total mass of the electrolyte, its actual detected amount in the battery cell is about 0.05%.

[0140] In some embodiments, the electrolyte further comprises a second lithium salt additive, the second lithium salt additive comprising at least one of lithium bis(oxalato)borate, lithium difluorodioxalate phosphate, lithium tetrafluorodioxalate phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium perchlorate. Thereby, it is helpful to form a solid electrolyte film with high ionic conductivity on the surface of the negative active material.

[0141] In some embodiments, the electrolyte further comprises an electrolyte lithium salt, the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and the mass fraction of the electrolyte lithium salt is greater than or equal to 13% based on the total mass of the electrolyte. In this way, the conductivity of the electrolyte is improved.

[0142] For example, the mass fraction of the electrolyte lithium salt is 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 21%, 23%, 24%, or 25% based on the total mass of the electrolyte.

[0143] When the mass fraction of the electrolyte lithium salt is within the foregoing range based on the total mass of the electrolyte, the electrolyte has both high ionic conductivity and low viscosity.

[0144] After the electrolyte lithium salt is dissolved in the organic solvent, lithium ions are released, and the lithium ions form a solvation structure with the electrolyte, thereby improving the conductivity of the electrolyte and facilitating the rapid migration of lithium ions in the electrolyte.

[0145] In some embodiments, the electrolyte lithium salt comprises lithium hexafluorophosphate and lithium bisfluorosulfonylimide, and the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonylimide in the electrolyte is (1.2-2):1. In this way, the conductivity of the electrolyte is further improved.

[0146] Lithium bisfluorosulfonylimide has better conductivity, thermal stability, and hydrolysis resistance than lithium hexafluorophosphate, but lithium bisfluorosulfonylimide has the problem of difficult dissociation. Lithium hexafluorophosphate is superior in commercial production and application maturity, and has a lower production cost. When the electrolyte lithium salt comprises both lithium hexafluorophosphate and lithium bisfluorosulfonylimide, lithium hexafluorophosphate can promote the better dissociation of lithium bisfluorosulfonylimide, improve the performance of the electrolyte, and thus improve the cycle life and fast charging performance of the battery.

[0147] For example, the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonylimide in the electrolyte can be tested by the following method: the concentration of inorganic components in the electrolyte can be quantitatively analyzed by ion chromatography analysis method according to standard JY / T020-1996.

[0148] [Positive electrode sheet]

[0149] In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located at least on one side of the positive electrode current collector, and the positive electrode active material layer has a compacted density of 2.2 g / cm 3 -2.6 g / cm 3 . In this way, the fast charging performance of the battery cell is improved.

[0150] For example, the compact 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 .

[0151] When the compact density of the positive electrode active material layer is within the aforementioned range, the compact density of the positive electrode active material layer is moderate, and the positive electrode sheet has a high energy density.

[0152] For example, the compact density of the positive electrode active material layer can be tested by dividing the mass of the positive electrode active material layer by the thickness of the positive electrode active material layer. 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 sheet and calculating the difference in mass and thickness before and after wiping.

[0153] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive electrode active material, the conductive agent, the binder, and any other components in a solvent (for example, N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector; and performing drying, rolling (for example, cold pressing), and other processes to form the positive electrode active material layer and obtain the positive electrode sheet. The compact density of the positive electrode active material layer mentioned above refers to the compact density of the positive electrode active material layer after rolling. Specifically, the compact density of the positive electrode active material layer after rolling and formation, the compact density of the positive electrode active material layer when the battery cell is in a full charge state or a full discharge state, and the compact density of the positive electrode active material layer after the battery cell is left for a long time are all within the aforementioned range.

[0154] In some embodiments, the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate with an olivine structure or a modified material thereof. In this way, the cycle life of the battery cell is improved.

[0155] The lithium-containing phosphate with an olivine structure has a low cost and a 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 charging and discharging, reduce structural stress, and prolong the cycle life of the battery.

[0156] In some embodiments, the lithium-containing phosphate with an olivine structure or the modified material thereof comprises a core portion comprising the lithium-containing phosphate with an olivine structure, and a coating layer covering the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more of C, Fe, Ti, Zr, Hf, Ge, and Sn. In this way, the structural stability and ionic conductivity of the positive electrode active material are improved.

[0157] The coating layer can effectively alleviate the poor electronic conductivity and ionic conductivity of the olivine-structured lithium-containing phosphate, and improve the specific capacity of the positive electrode active material and the powder compaction density.

[0158] In some embodiments, the olivine-structured lithium-containing phosphate includes a compound with a general formula of Li x A y Me a M b P 1-c X c Y z , wherein 0.5≤x≤1.3, 0≤y≤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; M 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; and Y includes one or more of O, F. Thus, the ionic conductivity and electronic conductivity of the core are improved.

[0159] When the olivine-structured lithium-containing phosphate satisfies the aforementioned general formula, the advantages of the ternary material are fully utilized, the high-temperature resistance and structural stability of the battery cell prepared therefrom are improved, and the manufacturing cost of the battery cell is reduced.

[0160] The battery will be accompanied by Li deintercalation and consumption during charging and discharging, and the molar content of Li is different when the battery is discharged to different states. In the enumeration of the positive electrode active material in the present application, the molar content of Li is the initial state of the material, i.e., the state before feeding. After the positive electrode active material is applied to the battery system and undergoes charging and discharging cycles, the molar content of Li will change.

[0161] In the enumeration of the positive electrode active material for lithium ion batteries in the present application, the molar content of O is only the theoretical state value. 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.

[0162] In some embodiments, the coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.32. Thus, the electronic conductivity of the positive electrode active material is improved.

[0163] The carbon layer can significantly improve the electronic conductivity of the lithium-containing olivine-structured phosphate, compensate for the poor electronic conductivity of the lithium-containing olivine-structured phosphate, and improve the capacity of the battery cell.

[0164] For 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.

[0165] When the graphitization degree of the carbon layer is within the above range, the arrangement of carbon atoms in the carbon layer is relatively disordered, there are many lattice defects, and a complete graphite lattice is not formed, so the electronic conductivity is slightly lower than that of carbon materials with a higher graphitization degree. The carbon layer with a relatively disordered arrangement of carbon atoms generally has a higher specific surface area, which helps to ensure sufficient contact between the core and the electrolyte and improves the lithium ion transmission efficiency at the two-phase interface.

[0166] For example, the graphitization degree of the carbon layer can be tested by the following method: The graphitization degree can be determined by the lattice parameters of the carbon crystal by XRD diffraction according to the standards JB / T4220-2011 and JIS K0131-1996.

[0167] In some embodiments, in a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes lithium-containing olivine-structured phosphate with a longest diameter of 1 μm to 3 μm and lithium-containing olivine-structured phosphate with a shortest diameter of 0.1 μm to 0.3 μm. In this way, the energy density of the battery cell can be improved.

[0168] For example, in a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes lithium-containing olivine-structured phosphate with a longest diameter of 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0169] For example, in a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes lithium-containing olivine-structured phosphate with a shortest diameter of 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, or 0.3 μm.

[0170] In some embodiments, the Dv50 particle size of the positive electrode active material is 1 μm to 5 μm.

[0171] For 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.

[0172] In some embodiments, the Dv10 particle size of the positive electrode active material is 0.4 μm to 0.7 μm.

[0173] As an example, the Dv10 particle size of the positive electrode active material can be 0.4 pm, 0.5 pm, 0.6 pm, or 0.7 pm.

[0174] When the Dv50 particle size and the Dv10 particle size of the positive electrode active material are within the aforementioned ranges, the overall particle size distribution of the positive electrode active material is reasonable, which is conducive to improving the powder compaction density of the positive electrode active material, and then improving the electrode compaction density of the positive electrode sheet, and ultimately improving the volumetric energy density of the battery cell.

[0175] The aforementioned Dv50 particle size refers to the particle size corresponding to the cumulative volume distribution percentage of 50%.

[0176] The aforementioned Dv10 particle size refers to the particle size corresponding to the cumulative volume distribution percentage of 10%.

[0177] As an example, the particle size of the positive electrode active material can be determined by laser diffraction particle size analysis method. Specifically, the particle size of the positive electrode active material can be determined by using a laser particle size analyzer (for example, Malvern-Master-Size-3000) according to the standard GB / T19077-2016.

[0178] In some embodiments, the positive electrode active material is primary particles or quasi-single crystal particles. In this way, the particle size of the positive electrode active material is large, which is conducive to improving the energy density of the battery cell.

[0179] When the positive electrode active material is primary particles or quasi-single crystal particles, the particle size of the positive electrode active material is large, which is helpful to improve the powder compaction density thereof. Further, under the condition that the particle size distribution is similar, the larger the particle size of the primary particles of the positive electrode active material, the greater the powder compaction density of the positive electrode active material, which is conducive to improving the volumetric energy density of the battery cell.

[0180] In some embodiments, the positive electrode active material is a mixture of primary particles and secondary particles, so that the primary particles can improve the powder compaction density of the positive electrode active material, and the secondary particles can improve the ionic conductivity of the positive electrode active material. The combined use of primary particles and secondary particles can jointly improve the volumetric energy density and fast charging capability of the battery.

[0181] In some embodiments, the positive electrode active material layer further comprises a lithium-rich material, and the lithium-rich material comprises one or more of lithium ferrite, lithium nickelate, lithium nickel-copper oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, trilithium citrate, lithium nickel-cobalt-manganese oxide. In this way, it is helpful to improve the cycle life of the battery cell.

[0182] The SEI film is formed on the surface of the negative active material when the battery is first charged, and the breaking and recombination of the SEI during the charge and discharge cycle will cause irreversible consumption of lithium ions, resulting in a decrease in the first cycle efficiency of the battery and a loss of capacity. The addition of a lithium-rich material can pre-supplement the lost lithium during the preparation of the battery, reduce or eliminate the capacity decay caused by lithium loss, and prolong the cycle life of the battery.

[0183] In some embodiments, the lithium-rich material includes at least one of lithium ferrite, lithium nickelate, lithium oxalate. Thus, after the lithium-rich material releases lithium ions through the formation process, the residual product can improve the internal resistance of the positive active material, improve the direct current impedance of the battery, and improve the charge and discharge power of the battery.

[0184] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, as a metal foil, an 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0185] In some embodiments, the positive active material layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0186] In some embodiments, the positive active material layer can 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.

[0187] [Negative electrode sheet]

[0188] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer located at least on one side of the negative current collector, and the negative active material layer has a compaction density of 1.2 g / cm 3 -1.5 cm 3 . Thus, it helps to improve the fast charging performance of the battery monomer.

[0189] As an example, the compaction density of the negative active material layer can be 1.2 g / cm 3 , 1.3 g / cm3 1.4 g / cm3 3 or 1.5 g / cm3 3 .

[0190] When the compacted density of the negative active material layer is within the aforementioned range, the compacted density of the negative active material layer is moderate, and the lithium ion deintercalation rate of the negative electrode sheet is fast, which is beneficial to improve the fast charging performance of the battery.

[0191] For example, the test method of the compacted density of the negative active material layer can be consistent with the test method of the compacted density of the positive active material layer, which will not be described here.

[0192] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative current collector, and after drying, rolling treatment (such as cold pressing process) and other processes, the negative active material layer is formed to obtain the negative electrode sheet. The compacted density of the aforementioned negative active material layer refers to the compacted density of the negative active material layer after rolling treatment. Specifically, the compacted density of the negative active material layer after rolling treatment and formation treatment, the compacted density of the negative active material layer when the battery cell is in a full charge state or a full discharge state, and the compacted density of the negative active material layer after the battery cell is left for a long time are all within the aforementioned range.

[0193] In some embodiments, the coating weight of a single layer of the negative active material layer is greater than or equal to 0.1 g / 15 40.25 mm2 2 .

[0194] For example, the coating weight of a single layer of the negative active material layer can be 0.1 g / 15 40.25 mm2 2 , 0.105 g / 15 40.25 mm2 2 , 0.115 g / 15 40.25 mm2 2 , 0.12 g / 15 40.25 mm2 2 , 0.125 g / 15 40.25 mm2 2 , 0.13 g / 15 40.25 mm2 2 , 0.135 g / 15 40.25 mm2 2 , 0.14 g / 15 40.25 mm2 2 , 0.145 g / 15 40.25 mm2 2 .

[0195] When the coating weight of the single layer of the negative electrode active material layer is within the aforementioned range, the thickness of the negative electrode active material layer on the surface of the negative electrode current collector is moderate and has high uniformity, the transmission path of lithium ions in the negative electrode active material layer is short, and the negative electrode active material can be quickly embedded and de-embedded during the charging and discharging process, thereby improving the rapid charging and discharging capacity of the battery.

[0196] For example, the coating weight of the single layer of the negative electrode active material layer can be tested by the following method: the negative electrode active material layer on the negative electrode tab can be wiped, and the coating weight can be obtained by calculating the mass difference before and after wiping.

[0197] In some embodiments, the coating weight of the single layer of the negative electrode active material layer is 0.1 g / 15 40.25 mm 2 -0.145 g / 15 40.25 mm 2 Therefore, the negative electrode active material layer has a relatively optimal lithium ion de-embedding rate and a relatively high energy density.

[0198] In some embodiments, the coating weight of the single layer of the negative electrode active material layer is 0.1 g / 15 40.25 mm 2 -0.135 g / 15 40.25 mm 2 When the aforementioned positive electrode tab is used to assemble a battery cell, the volumetric energy density of the battery cell can be 380 Wh / L-405 Wh / L. Therefore, the battery cell has a relatively high volumetric energy density.

[0199] When the coating weight of the single layer of the negative electrode active material layer is 0.1 g / 15 40.25 mm 2 -0.135 g / 15 40.25 mm 2 At this time, the thickness of the negative electrode active material layer is relatively thin, and the distance that lithium ions need to diffuse in the negative electrode active material layer is relatively short, thereby accelerating the transmission of lithium ions and improving the fast charging performance of the battery. For example, the time for charging the battery cell from 10% SOC to 80% SOC is 7 min-15 min. Therefore, the battery cell has a relatively optimal fast charging performance.

[0200] For example, when the battery cell is used in a vehicle, the state of charge (SOC) of the battery of the vehicle is usually between 10% and 80% in actual use scenarios. Therefore, when the charging time of the battery within the SOC range is short, the user's waiting time for charging can be reduced, thereby greatly improving the user's experience. Specifically, when the time for charging the battery cell from 10% SOC to 80% SOC is 7 min-15 min, the battery cell has a 4C-6C equivalent fast charging performance within the SOC range.

[0201] In some embodiments, the coating weight of a single layer of the negative electrode active material is 0.136 g / 1540.25 mm. 2 -0.145g / 1540.25mm 2 When assembled using the aforementioned positive electrode plates, the volumetric energy density of the battery cell can be 410Wh / L-430Wh / L. Therefore, the battery cell possesses a high volumetric energy density.

[0202] When the coating weight of a single layer of the negative electrode active material is 0.136 g / 1540.25 mm... 2 -0.145g / 1540.25mm 2 When the negative electrode active material layer is thicker, there are more lithium-ion insertion / extraction sites that the negative electrode active material can provide, which helps to improve the energy density of the battery.

[0203] In some embodiments, the battery cell takes 20-30 minutes to charge from 10% SOC to 80% SOC. Therefore, the battery cell exhibits superior fast-charging performance. Specifically, when the battery cell takes 20-30 minutes to charge from 10% SOC to 80% SOC, it has an equivalent fast-charging performance of 2.2C-4C within that SOC range.

[0204] Test method: at 25℃, the battery is treated as follows: 1) rest for 30 min; 2) 0.33Cn direct current discharge to 2.5V; 3) pause; 4) rest for 120 min; 5) 0.33Cn constant current charging to 10% CnAh; 6) 6.45Cn constant current charging to 5% CnAh; 7) 5.33Cn constant current charging to 5% CnAh; 8) 4.5Cn constant current charging to 5% CnAh; 9) 3.98Cn constant current charging to 5% CnAh; 10) 3.55Cn constant current charging to 5% CnAh; 11) 3.25Cn constant current charging to 5% CnAh; 12) 3.02Cn constant current charging to 5% CnAh; 13) 2.83Cn constant current charging to 5% CnAh; 14) 2.66Cn constant current charging to 5% CnAh; 15) 2.49Cn constant current charging to 5% CnAh; 16) 2.33Cn constant current charging to 5% CnAh; 17) 2.14Cn constant current charging to 5% CnAh; 18) 1.94Cn constant current charging to 5% CnAh; 19) 1.71Cn constant current charging to 5% CnAh; 20) 0.33Cn constant current charging to 3.65V, constant voltage charging to 0.05C; 21) rest for 120 min; 22) repeat steps 2)-21) 50 times; 23) rest for 120 min; 24) 0.33Cn constant current charging to 3.65V, constant voltage charging to 0.05C. After the test is completed, the battery monomer is disassembled, and the lithium precipitation is observed. Specifically, for the negative electrode sheet, if at least one of the following conditions is met, lithium precipitation can not occur: ① the maximum area of a single lithium precipitation area is not greater than 5mm x 5mm; ② the number of lithium precipitation areas is not more than 5 per negative electrode sheet; ③ the total area of lithium precipitation is not greater than 100mm 2 / battery.

[0205] In some embodiments, the negative electrode active material layer comprises a first negative electrode active material layer and a second negative electrode active material layer arranged in a stack, the first negative electrode active material layer is located 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 9.2-18.5μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2-15.5μm. In this way, the fast charging performance of the battery monomer can be significantly improved.

[0206] When the Dv50 of the first negative electrode active material and the second negative electrode active material is within the aforementioned range, 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 first negative electrode active material layer is larger, which can provide more lithium extraction sites and improve the capacity of the battery; the particle size of the second negative electrode active material layer is smaller, the lithium ion extraction rate is faster, which helps to improve the fast charging performance of the battery.

[0207] In some embodiments, the negative active material layer comprises a negative active material, and the negative active material comprises a silicon-containing material, and a mass fraction of silicon in the silicon-containing material is 0.1%-7%. In this way, the mass energy density of the battery cell can be improved.

[0208] 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 active material, the mass energy density of the battery can be effectively improved. Further, since pure silicon material will undergo a huge volume expansion (more than 300%) after lithium ions are inserted, the SEI will be broken and recombined, the electrolyte and active lithium ions will be consumed, and ultimately the cycle life of the battery will be reduced. By controlling the mass fraction of silicon in the silicon-containing material to be 0.1%-7%, the mass energy density of the battery can be improved by taking advantage of the extremely high theoretical specific capacity of silicon, and the volume expansion and contraction of the silicon-containing material during charging and discharging can be alleviated.

[0209] For 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%.

[0210] For example, the silicon-containing material can be a silicon-carbon material.

[0211] In some embodiments, the mass fraction of silicon in the silicon-containing material is 1%-5%. In this way, the mass energy density of the battery cell can be further improved.

[0212] For example, the mass fraction of silicon in the silicon-containing material can be tested by the following method: the standard YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015 can be referred to. Specifically, an ICP inductively coupled plasma emission spectrometer can be used to measure according to the manufacturer's instructions.

[0213] In some embodiments, the negative current collector can be a metal foil or a composite current collector. For example, as a metal foil, a 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 base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0214] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0215] In some embodiments, the negative active material layer can further 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).

[0216] In some embodiments, the negative active material layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0217] In some embodiments, the negative active material layer can further optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0218] [Separator]

[0219] 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, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0220] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0221] In some embodiments, referring to FIG. 1, the shell includes two first shell walls 101 arranged opposite to each other, and a surrounding wall connecting the two first shell walls 101. The surrounding wall includes two second shell walls 102 arranged opposite to each other along the length direction of the first shell wall 101, two third shell walls 103 arranged opposite to each other along the width direction of the first shell wall 101, and the distance between the two first shell walls 101 is D, i.e., the thickness of the battery monomer is D, and D is less than or equal to 30 mm. Thus, it is beneficial for the rapid heat dissipation of the battery monomer.

[0222] Since under fast charging conditions, the charging current and voltage flowing through the battery monomer will increase accordingly, according to Joule's law, the heat generated will also increase substantially. For long strip-shaped battery monomers, the first shell wall is the surface with the largest area of the battery monomer, so the heat dissipation effect of the battery monomer near the first shell wall is good. However, in the thickness direction of the battery monomer, that is, the width direction of the third shell wall, the heat diffusion inside the battery monomer is slow. When the distance D between the two first shell walls 101 is within the above range, the heat dissipation effect of the battery monomer in the thickness direction is good, which is beneficial to achieve good heat dissipation under fast charging and improve the fast charging performance of the battery monomer.

[0223] In some embodiments, D is 10mm-25mm. In this way, the battery monomer has high mechanical strength and good heat dissipation capability.

[0224] As an example, D can be 5mm, 10mm, 15mm, 20mm, 25mm or 30mm.

[0225] In some embodiments, the thickness of the first shell wall 101 and the third shell wall 103 is independently less than or equal to 0.5mm. In this way, the volumetric energy density of the battery monomer can be improved.

[0226] When the thickness of the first shell wall 101 and the third shell wall 103 is within the above range, the shell wall is thin and the weight of the shell is light, which is beneficial to improve the mass energy density and volumetric energy density of the battery monomer.

[0227] As an example, the thickness of the first shell wall 101 and the third shell wall 103 can be the same.

[0228] In some embodiments, the first shell wall 101 and the third shell wall 103 comprise at least one of an aluminum shell and a steel shell. In this way, the mechanical strength of the battery monomer can be improved.

[0229] Under the same thickness, the mechanical strength of the steel shell is greater than that of the aluminum shell, which can better bind the electrode assembly and alleviate the expansion of the battery monomer during charging and discharging.

[0230] Under the same thickness, the density of the aluminum shell is lighter than that of the steel shell, the weight of the shell is further reduced, and the mass energy density of the battery monomer is further improved.

[0231] 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 0.1mm-0.5mm. In this way, the volume expansion of the battery monomer during charging and discharging can be effectively alleviated.

[0232] In some embodiments, the first shell wall 101 and the third shell wall 103 are aluminum shells, and the wall thickness of the aluminum shells is 0.3-0.4 mm. In this way, the mass energy density of the battery cell can be effectively improved.

[0233] In some embodiments, the first shell wall 101 and the third shell wall 103 are obtained by bending and welding an aluminum plate, and the weld of the welding is located at the connection of the first shell wall 101 and the third shell wall 103. In this way, the leakage of electrolyte can be reduced.

[0234] The aluminum shell obtained by bending and laser welding of an aluminum plate has excellent sealing effect, can effectively prevent electrolyte leakage, improve the stability of the internal environment of the battery cell, and improve the cycle life of the battery cell.

[0235] In some embodiments, when the organic solvent in the electrolyte is mainly low-viscosity solvent, the electrolyte as a whole also exhibits low viscosity. Low-viscosity electrolyte is prone to decomposition and gas production during high-rate charging and discharging, resulting in swelling of the battery cell. As a mechanical weak point, the weld may crack in extreme cases. In order to prevent rapid deterioration caused by electrolyte leakage after the weld cracks, the weld can be located at the connection of the third shell wall and the first shell wall away from the ground, so that after the weld cracks, the electrolyte is still not easy to flow out of the battery cell, effectively inhibiting the rapid deterioration of the battery.

[0236] In some embodiments, a side support plate is provided between the electrode assembly and the first shell wall 101. In this way, the structural stability of the battery cell can be improved.

[0237] The side support plate can block the direct contact between the pole piece and the shell, and reduce the damage of the round corner at the edge of the inner wall of the shell to the pole piece.

[0238] In some embodiments, at least one of the second shell walls 102 is provided with a pressure relief portion 104 configured to be able to release the pressure inside the shell, and the area of the orthographic projection of the pressure relief portion 104 on the second shell wall 102 is 7%-15% of the area of the second shell wall 102. In this way, when the internal pressure of the battery cell is too high, the internal overpressure gas can be quickly released through the pressure relief portion 104.

[0239] As an example, the area of the pressure relief portion can be 155 mm 2 , and the area of the second shell wall can be 1920 mm 2 .

[0240] When the area of the normal projection of the pressure relief portion 104 on the second shell wall 102 is within the aforementioned range, the pressure relief portion can quickly respond to the sudden increase in the internal pressure of the battery cell, break to release the internal pressure, and occupy less space on the second shell wall, facilitating the arrangement of other structural components on the second shell wall.

[0241] In some embodiments, the capacity of the battery cell is Q, the area of the normal projection of the pressure relief portion 104 on the second shell wall 102 is P, and 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 . Thus, it is helpful to quickly release the overpressure gas inside the battery cell.

[0242] When the capacity of the battery cell is large, the content of the low-viscosity electrolyte inside the battery is correspondingly high, and the gas production per unit time is large during high-rate charging and discharging. In addition, lithium bisfluorosulfonylimide will also produce a gas by-product reaction with the negative active material layer in the full state. Therefore, a pressure relief portion with a larger area is needed to provide more exhaust space, so that it can quickly respond to the initial stage of the sudden increase in the internal pressure of the battery cell 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 the pressure relief requirements of the battery cell with the corresponding capacity can be met.

[0243] In some embodiments, referring to FIGS. 2-4, the positive electrode tab includes a positive electrode current collector and a positive 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 portion 11 and at least one positive electrode tab portion 12, the positive electrode main body portion 11 is connected to the positive electrode tab portion 12; the negative electrode tab includes a negative electrode current collector and a negative 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 portion 21 and at least one negative electrode tab portion 22, the negative electrode main body portion 21 is connected to the negative electrode tab portion 22, the second shell wall 102 is provided with an electrode terminal, the positive electrode tab portion 12 and the negative electrode tab portion 22 are respectively electrically connected to the electrode terminals on the two second shell walls 102, and the second shell wall 102 electrically connected to the positive electrode tab portion 12 is provided with a folding structure 106 between the positive electrode main body portion 11, the folding structure 106 is configured to fold the plurality of positive electrode tab portions 12. Thus, it is convenient to fix the positive electrode tab and weld the positive electrode tab and the pole 105.

[0244] The positive and negative tabs 12 and 22 of the battery cell are respectively led out from two second shell walls 102 of the shell, i.e., the tabs are led out from different sides, which helps to arrange the battery cell more efficiently in limited space, facilitates the formation of efficient series and parallel structures of multiple battery cells inside the battery pack, reduces the space occupied by the connecting members between the battery cells, and improves the volumetric energy density of the battery pack. In order to improve the volumetric energy density, the electrode assembly can be formed by using a lamination process, wherein each positive tab has a corresponding positive tab part, and each negative tab has a corresponding negative tab part. In order to realize current collection, all the positive and negative tab parts need to be collected respectively and then electrically connected to the corresponding electrode terminals.

[0245] Generally, referring to FIG. 4, the positive current collector is made of aluminum foil, and the negative current collector is made of copper foil. Since the copper foil is soft and easy to break, the negative tab part needs to be welded to the corresponding pole on the second shell wall first and then loaded into the surrounding wall structure formed by the first and third shell walls, and finally the positive tab part is welded to the corresponding pole on the second shell wall. In order to reduce the risk of tab insertion in reverse during welding of the positive tab part to the corresponding second shell wall and thus causing internal short circuit of the battery cell, the plurality of positive tab parts 12 can be fixed by the folding structure 106 to reduce the risk of tab insertion in reverse and facilitate the welding of the positive tab part to the pole.

[0246] In some embodiments, the edge of the positive tab is chamfered along the length direction of the first shell wall 101. Thus, the electrode assembly can be quickly assembled, and the risk of poor puncture of the isolation film when the electrode assembly is loaded into the shell is reduced.

[0247] In some embodiments, the total width of the positive tab part 12 along the width direction of the positive main body part 11 accounts for 30%-100% of the total width of the positive main body part 11, and / or the total width of the negative tab part 22 along the width direction of the negative main body part 21 accounts for 30%-100% of the total width of the negative main body part 21. Thus, the overcurrent capacity of the tab can be effectively improved.

[0248] When the battery cell is subjected to high-rate charging and discharging, the current and voltage inside the battery cell will increase accordingly, and the current passing through the tab will also increase. A larger tab area means a lower resistance. On the one hand, according to Ohm's law, under the same voltage, a tab with a larger area can carry a higher current, i.e., has a stronger overcurrent capacity. On the other hand, when the resistance of the tab is low, the heat generated by the current flowing through the tab due to resistance loss can be reduced, which indirectly improves the heat dissipation efficiency of the battery under high current. At this time, the adverse effect of the low boiling point of the first solvent on the performance of the battery is significantly reduced, and the first solvent can fully play the advantages of improving the electrical conductivity of the electrolyte and improving the fast-charging capacity of the battery cell.

[0249] It should be noted that for the battery cell satisfying the aforementioned L / H ratio, when the electrode assembly is prepared by using the stacking process, the electrode assembly can include a plurality of layers of the positive electrode tab / isolation film / negative electrode tab / isolation film structure arranged continuously. At this time, the aforementioned ratio of the total width of the positive electrode tab 12 to the total width of the positive electrode body part 11 corresponds to the ratio of the width of the tab part to the width of the body part in any positive electrode tab, and similarly, the aforementioned ratio of the total width of the negative electrode tab 22 to the total width of the negative electrode body part 21 corresponds to the ratio of the width of the tab part to the width of the body part in any negative electrode tab; when the electrode assembly is prepared by using the winding process, the electrode assembly includes only one layer of the positive electrode tab, one layer of the isolation film, and one layer of the negative electrode tab, wherein the positive electrode tab has a plurality of tab parts thereon. At this time, the aforementioned ratio of the total width of the positive electrode tab 12 to the total width of the positive electrode body part 11 corresponds to the ratio of the sum of the widths of all the positive electrode tabs to the width of the positive electrode body part, and similarly, the aforementioned ratio of the total width of the negative electrode tab 22 to the total width of the negative electrode body part 21 corresponds to the ratio of the sum of the widths of all the negative electrode tabs to the width of the negative electrode body part.

[0250] In some embodiments, the size of the positive electrode tab 12 along the width direction of the positive electrode body part is 50%-80% of the size of the positive electrode body part 11. In this way, the positive electrode tab has a better heat dissipation capacity.

[0251] In some embodiments, referring to FIG. 5, the second shell wall 102 connected with the negative electrode tab part 22 is provided with an electrolyte injection hole 107. In this way, the injection of electrolyte is facilitated.

[0252] Since the second shell wall connected with the positive electrode tab part is provided with the folding structure 106 for folding the positive electrode tab part, in order to make the second shell wall have a higher mechanical strength, the electrolyte injection hole 107 is arranged on the second shell wall 102 connected with the negative electrode tab part 22.

[0253] In some embodiments, referring to FIGS. 5-7, the electrolyte injection hole 107 and the pressure relief part 104 of the shell are located on different second shell walls 102, and the pressure relief part 104 is configured to be able to release the pressure inside the shell. In this way, the corrosion of the electrolyte to the pressure relief part 104 during the injection of electrolyte can be reduced.

[0254] Since the electrolyte will corrode the pressure relief part when the electrolyte is injected into the battery cell through the electrolyte injection hole 107, the electrolyte injection hole 107 and the pressure relief part of the shell should be located on different second shell walls.

[0255] In some embodiments, the pressure relief part 104 can be arranged on both second shell walls 102. The proportional relationship between the area of the pressure relief part and the area of the second shell wall can refer to the foregoing content.

[0256] In some embodiments, referring to FIG. 7, at least one mounting hole is provided on the electrode terminal, and the pole 105 is inserted into the mounting hole and riveted with the tab. In this way, the volume of the battery cell can be reduced, the weight of the battery cell can be reduced, and the energy density of the battery cell can be improved.

[0257] The electrical connection realized by the single pole can reduce the connection points, simplify the production and assembly process, and require less material and processing steps, thus being low in cost.

[0258] In some embodiments, referring to FIGS. 5 and 6, at least two mounting holes are provided on the electrode terminal, and each pole 105 is inserted into the mounting hole and riveted with the tab. In this way, the overcurrent capacity of the pole 105 can be improved.

[0259] The electrical connection realized by the double pole can disperse the current, reduce local overheating, and improve the fast-charging performance of the battery.

[0260] In some embodiments, the diameter of the pole 105 is 3-8 mm. In this way, the pole 105 has both high overcurrent capacity and low space occupation.

[0261] As an example, the diameter of the pole can be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm.

[0262] When the diameter of the pole is within the above range, the overcurrent capacity of the pole is strong, the internal resistance is low, and the heat generation can be reduced.

[0263] In some embodiments, referring to FIG. 8, the pole 105 riveted with the positive tab and the pole 105 riveted with the negative tab are arranged in a staggered manner along the length direction of the first shell wall 101, and optionally, the pole 105 riveted with the positive tab and the pole 105 riveted with the negative tab are arranged in a diagonal manner along the length direction of the first shell wall 101. In this way, the battery cell can be arranged more efficiently in a limited space, and the volume energy density of the assembled battery module or battery pack can be improved.

[0264] In some embodiments, referring to FIG. 9, the pole 105 and the tab are electrically connected through the adapter sheet 108. In this way, the welding quality and connection reliability between the pole 105 and the tab can be significantly improved.

[0265] When the adapter sheet 108 is used to electrically connect the pole and the tab, the shape and size of the adapter sheet 108 can be adjusted as needed to adapt to different distances and positions, and the adapter sheet 108 has fewer welding process defects, which can help to more evenly distribute the current, reduce local overheating and potential difference, and improve the service life of the battery.

[0266] In some embodiments, referring to FIG. 10, the direct electrical connection is between the pole column 105 and the tab. In this way, the structural complexity inside the battery cell is reduced, the volume of the battery cell is reduced, and the energy density is improved.

[0267] When the pole column is directly electrically connected to the tab, the connecting member is omitted, the internal structure of the battery cell is simplified, the assembly steps are reduced, and the overall manufacturing cost is reduced.

[0268] In some embodiments, the above-mentioned battery cell can also be directly assembled into a battery pack, the structure of the battery module is omitted, and the energy density of the battery is improved. The number of battery cells contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0269] In a second aspect of the present application, a battery device is provided, which comprises the above-mentioned battery cell. The battery device can be a battery module, a battery pack, an energy storage device, etc. In this way, the battery device has all the features and advantages of the above-mentioned battery cell, which will not be repeated here.

[0270] In a third aspect of the present application, a power consuming device is provided, which comprises the above-mentioned battery cell. In this way, the power consuming device has all the features and advantages of the above-mentioned battery cell, which will not be repeated here.

[0271] The above-mentioned battery cell or battery pack can be used as a power source of the power consuming device, or as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0272] As the power consuming device, the battery cell or battery pack can be selected according to the use requirements thereof.

[0273] FIG. 11 is a power consuming device as an example. The power consuming 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 power consuming device for the battery, a battery pack can be used.

[0274] The scheme 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. If the specific technology or condition is not specified in the embodiments, it is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained from the market.

[0275] Example 1

[0276] 1) Preparation of positive electrode tab

[0277] The positive electrode tab comprises a positive current collector aluminum foil and a positive active material layer, the positive active material layer comprises a film layer formed by uniformly coating a positive slurry (solvent: N-methyl pyrrolidone) on the surface of the positive current collector aluminum foil, and then drying and cold pressing, the positive active material layer comprises positive active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.4:1.1. The positive active material is lithium-containing phosphate containing iron, aluminum, titanium, and vanadium, wherein 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 comprises lithium-containing phosphate with an olivine structure having a longest diameter of 2.5 μm, and lithium-containing phosphate with an olivine structure having a shortest diameter of 0.2 μm.

[0278] 2) Preparation of negative electrode tab

[0279] The negative electrode tab comprises a negative current collector copper foil and a negative active material layer, the negative active material layer comprises a film layer formed by uniformly coating a negative slurry (solvent: deionized water) on the surface of the negative current collector copper foil, and then drying and cold pressing, the negative active material layer comprises negative active material, binder styrene-butadiene rubber (SBR), thickening agent sodium carboxymethyl cellulose (CMC-Na), and conductive agent carbon black (Super P) in 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.

[0280] 3) Separation film

[0281] The separation film is a porous polypropylene (PP) film.

[0282] 4) Preparation of electrolyte

[0283] The composition of the electrolyte is shown in Tables 1, 2, and 3. In the examples, the first lithium salt additive is lithium difluorophosphate, except that in Example 9, the first lithium salt additive is lithium difluoro(oxalato)borate (LIDFOB).

[0284] 5) Preparation of battery

[0285] The lithium ion battery comprises a shell, an electrode assembly, and an electrolyte, the electrode assembly and the electrolyte are arranged in the shell, the electrode assembly comprises a positive electrode tab, a negative electrode tab, and a separation film, the separation film is arranged between the positive electrode tab and the negative electrode tab. The thickness D of the battery cell is 16 mm.

[0286] The differences between the remaining examples, comparative examples, and Example 1 are shown in Tables 1, 2, and 3.

[0287] Table 1

[0288] In the examples and comparative examples described in Table 1: the organic solvent material in the electrolyte and the mass ratio were DMC / EMC / EC = 30 / 35 / 35, the electrolyte lithium salt in the electrolyte was lithium hexafluorophosphate, the mass content was 12.5%, the coating weight of the single-layer positive electrode active material layer was 0.283 g / 1540.25 mm 2 , the compaction density of the positive electrode active material layer was 2.45 g / cm 3 , the coating weight of the single-layer negative electrode active material layer was 0.127 g / 1540.25 mm 2 , the compaction density of the negative electrode active material layer was 1.45 g / cm 3 .

[0289] The power density and volume energy density of the battery cells in the examples and comparative examples in Table 1 were tested, and the test results are shown in Table 1-1. The test method is as follows:

[0290] Volume energy density: at 25°C, the battery cell was discharged at 0.33C constant current to 2.5V; stand for 5min, 0.33C constant current charged to the upper limit cutoff voltage 3.65V, then constant voltage charged to the current of 0.05C, record the discharge capacity CO and discharge energy E0 at this time. Volume energy density = E0 / cell volume (L).

[0291] Power density: at 25°C, the battery was charged to the cutoff voltage 3.65V at 0.33C constant current, and rested for 10min; discharged at 0.33C0 constant current for 90min, and adjusted the battery SOC to 50%, then recorded the voltage U1 at this time, and then discharged at 3C0 pulse for 30s, and recorded the voltage U2 after discharging, then the corresponding direct current resistance R = (U1-U2) / 3C0, the power W = 2.5*(U1-2.5) / R, and the power density P = W / E0.

[0292] Table 1-1

[0293] Table 2

[0294] In the examples described in Table 2: the length L of the battery cell was 510mm, the width H of the battery cell was 120mm, the electrolyte lithium salt in the electrolyte was lithium hexafluorophosphate with a mass content of 12.5%, the mass fraction of the first lithium salt additive based on the total mass of the electrolyte was 0.22%, and the coating weight of the single-layer positive electrode active material layer was 0.283 g / 1540.25 mm 2The compaction densities of the positive active material layers are both 2.45 g / cm 3 The coating weights of the single-layer negative active material layers are both 0.127 g / 1540.25 mm 2 The compaction densities of the negative active material layers are both 1.45 g / cm 3 .

[0295] The power density and volume energy density tests of the battery cells in Table 2 are performed, and the test results are shown in Table 2-1.

[0296] Table 2-1

[0297] Table 3

[0298] In the examples described in Table 3: the length L of the battery cell is 510 mm, the width H of the battery cell is 120 mm, the organic solvent substance in the electrolyte and the mass ratio are both DMC / EMC / EC = 30 / 35 / 35, the electrolyte lithium salt in the electrolyte includes lithium hexafluorophosphate and lithium bisfluorosulfonylimide, the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonylimide in the electrolyte is 2:1, the concentration of the electrolyte lithium salt in the electrolyte is 1 mol / L, and the mass fraction of the first lithium salt additive is 0.22% based on the total mass of the electrolyte.

[0299] The rate performance and volume energy density tests of the battery cells in Table 3 are performed, and the test results are shown in Table 3-1.

[0300] Charging time test: ① Voltage calibration: 1) The battery cell with the same design of the stacked three-electrode core is placed at 25℃ for 30 min; 2) the battery cell is charged to the charging cut-off voltage 3.65V at 25℃ and 0.33C, and then constant voltage charging is continued at the charging cut-off voltage until the current is 0.05C, and the charging cut-off (wherein C represents the rated capacity of the battery cell); 3) placed at 25℃ for 1h; 4) the battery cell is discharged to the discharge cut-off voltage 2.5V at 25℃ and 0.33C, and the total discharge capacity C1 discharged by the battery cell is recorded; 5) placed at 25℃ for 1h. ② Charging test: 1) the stacked three-electrode core is placed at 25℃ for 30 min; 2) 0.33C1 direct current discharge to the discharge cut-off voltage 2.5V; 3) placed for 5 min; 4) xC1 constant current charging to the charging cut-off voltage 3.65V (three-electrode monitoring anode potential, when the anode potential is 0V, jump to the next step); 5) repeat steps 3)~4) for 9 times, and the value of x is 5, 4, 4.5, 3, 2, 1, 0.8, 0.5, 0.33, respectively; 6) take the x value and the charging capacity C x when the anode potential is 0V, and the corresponding SOC is obtained by C x / C1.x Total charging time T =∑(60 / x1xSOCx1), where x1 is the corresponding rate.

[0301] Table 3-1

[0302] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments or combining part of the configurations of the embodiments that a person skilled in the art can think of within the scope of the gist of the present application are also included in the scope of the present application.

Claims

1. A battery cell, wherein, a length of the battery cell is L, and a width of the battery cell is H, the value of L is 4 to 10 times the value of H; the battery cell comprises an electrolyte, the electrolyte comprises an organic solvent and a first lithium salt additive, the first lithium salt additive comprises at least one of a fluorine-containing borate and a fluorine-containing phosphate, and a mass fraction of the first lithium salt additive is 0.01%-0.5% based on a total mass of the electrolyte.

2. The battery cell of claim 1, wherein, The value of L is 4 to 7 times the value of H.

3. The battery cell of claim 1 or 2, wherein, L is 400mm-1000mm, and / or, H is 80mm-160mm.

4. The battery cell of any one of claims 1-3, wherein, The first lithium salt additive comprises at least one of lithium difluorophosphate, lithium difluoro oxalate phosphate, lithium difluoro oxalate borate, and lithium tetrafluoroborate.

5. The battery cell of any one of claims 1-4, wherein, The mass fraction of the first lithium salt additive in the electrolyte is 0.05%-0.5%, and optionally 0.1%-0.3%.

6. The battery cell of any one of claims 1-5, wherein, The conductivity of the electrolyte is 10ms / cm-20ms / cm.

7. The battery cell of any one of claims 1-6, wherein, The organic solvent comprises a first solvent, the first solvent comprises at least one of dimethyl carbonate and linear carboxylic acid ester, wherein a structural formula of the linear carboxylic acid ester satisfies R1-COO-R2, R1 and R2 are independently selected from C1-C5 alkyl or halogenated alkyl.

8. The battery cell of claim 7, wherein, The linear carboxylic acid ester comprises at least one of ethyl formate, isopropyl formate, ethyl acetate, methyl acetate, propyl acetate, and methyl propionate.

9. The battery cell of claim 7 or 8, wherein, A mass fraction of the linear carboxylic acid ester is 32%-68% based on a total mass of the electrolyte.

10. The battery cell of any one of claims 7-9, wherein, A mass fraction of the first solvent is greater than or equal to 4% based on a total mass of the electrolyte, and optionally, a mass fraction of the first solvent is 16%-80% based on a total mass of the electrolyte.

11. The battery cell of any one of claims 1-10, wherein, The organic solvent further comprises a second solvent, the second solvent comprises at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

12. The battery cell of claim 11, wherein, The second solvent comprises diethyl carbonate, and a content of the diethyl carbonate is not less than 12% based on a total mass of the electrolyte.

13. The battery cell of any one of claims 1-12, wherein, The electrolyte further comprises a non-lithium salt additive, the non-lithium salt additive comprises at least one of vinylene carbonate, fluoro-vinylene carbonate, and vinyl ethylene carbonate.

14. The battery cell of claim 13, wherein, A mass fraction of the vinylene carbonate is 0.5%-2.5% based on a total mass of the electrolyte, and / or, a mass fraction of the fluoro-vinylene carbonate is 0.05%-2% based on a total mass of the electrolyte.

15. The battery cell of any one of claims 1-14, wherein, The electrolyte further comprises a second lithium salt additive, the second lithium salt additive comprises at least one of lithium bis-oxalate borate, lithium difluoro di-oxalate phosphate, lithium tetrafluoro oxalate phosphate, lithium bis-trifluoromethanesulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium trifluoromethanesulfonate, and lithium perchlorate.

16. The battery cell of any one of claims 1-15, wherein, The electrolyte further comprises an electrolyte lithium salt, the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate and lithium bis-fluorosulfonyl imide, and a mass fraction of the electrolyte lithium salt is greater than or equal to 13% based on a total mass of the electrolyte.

17. The battery cell of claim 16, wherein, The electrolyte lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonimide, and the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonimide in the electrolyte is (1.2-2):

1.

18. The battery cell of any one of claims 1-17, wherein, Further comprising a positive electrode tab including a positive electrode current collector and a positive electrode active material layer at least on one side of the positive electrode current collector, the positive electrode active material layer having a compacted density of 2.2 g / cm 3 -2.6 g / cm 3 .

19. The battery cell of claim 18, wherein, The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure or a modified material thereof.

20. The battery cell of claim 19, wherein, The lithium-containing phosphate with an olivine structure or the modified material thereof includes: a core including a lithium-containing phosphate with an olivine structure, and a coating layer covering the surface of the lithium-containing phosphate with an olivine structure, and the coating layer contains one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn.

21. The battery cell of claim 20, wherein, The lithium-containing phosphate of olivine structure comprises a compound of general formula Li x A y Me a M b P 1-c X c Y z wherein 0.5≤x≤1.3, 0≤y≤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 comprises one or more of Na, K, Mg; Me comprises one or more of Mn, Fe, Co, Ni; M comprises 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 comprises one or more of S, Si, Cl, B, C, N; Y comprises one or more of O, F.

22. The battery cell of claim 20, wherein, The coating layer includes a carbon layer, and the graphitization degree of the carbon layer is 0.15-0.

32.

23. The battery cell of any one of claims 19-21, wherein, In a cross section of the positive electrode active material layer along the thickness direction, the positive electrode active material includes a lithium-containing phosphate with an olivine structure with a longest diameter of 1-3 μm, and a lithium-containing phosphate with an olivine structure with a shortest diameter of 0.1-0.3 μm.

24. The battery cell of any one of claims 19-23, 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 1-5 μm. The Dv10 particle size of the positive electrode active material is 0.4-0.7 μm. The positive electrode active material is a primary particle or a quasi-single crystal particle.

25. The battery cell of any one of claims 18-24, wherein, The positive electrode active material layer further includes a lithium-rich material, and the lithium-rich material includes one or more of lithium iron oxide, lithium nickel oxide, lithium nickel copper oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, and trilithium citrate.

26. The battery cell of any one of claims 1-25, wherein, Further comprising a negative electrode sheet including a negative electrode current collector and a negative electrode active material layer at least on one side of the negative electrode current collector, the negative electrode active material layer having a compacted density of 1.2 g / cm 3 -1.5 cm 3 .

27. The battery cell of claim 26, wherein, The coating weight of the single layer of the negative electrode active material layer is greater than or equal to 0.1 g / 1540.25 mm 2 .

28. The battery cell of claim 27, wherein, The coating weight of the single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 .

29. The battery cell of claim 27, wherein, The coating weight of the single layer of the negative electrode active material layer is 0.1 g / 1540.25 mm 2 -0.135 g / 1540.25 mm 2 .

30. The battery cell of claim 29, wherein, The time for charging the battery cell from 10% SOC to 80% SOC is 7-15 min.

31. The battery cell of claim 27, wherein, The coating weight of the single layer of the negative electrode active material layer is 0.136 g / 1540.25 mm 2 -0.145 g / 1540.25 mm 2 .

32. The battery cell of claim 31, wherein, The time for charging the battery cell from 10% SOC to 80% SOC is 20-30 min.

33. The battery cell of any one of claims 26-32, wherein, The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer arranged in a stacked manner, 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 9.2-18.5 μm, and the Dv50 of the second negative electrode active material in the second negative electrode active material layer is 7.2-15.5 μm.

34. The battery cell of any one of claims 26-33, wherein, The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-containing material, and the mass fraction of silicon in the silicon-containing material is 0.1%-7%.

35. The battery cell of claim 34, wherein, The mass fraction of silicon in the silicon-containing material is 1%-5%.

36. The battery cell of any one of claims 1-35, wherein, Further including a shell, the shell includes two first shell walls arranged oppositely, and a surrounding wall connecting the two first shell walls, the surrounding wall includes two second shell walls arranged oppositely along the length direction of the first shell wall, and two third shell walls arranged oppositely along the width direction of the first shell wall, wherein the distance between the two first shell walls is D, and D is less than or equal to 30 mm.

37. The battery cell of claim 36, wherein, D is 10-25 mm.

38. The battery cell of claim 36 or 37, wherein, The thickness of the first shell wall and the third shell wall is independently less than or equal to 0.5 mm.

39. The battery cell of claim 38, wherein, The first shell wall and the third shell wall comprise at least one of an aluminum shell and a steel shell.

40. The battery cell of claim 39, 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.

41. The battery cell of claim 39, 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.

42. The battery cell of claim 41, wherein, The first shell wall and the third shell wall are obtained by bending and welding an aluminum plate, and the weld of the welding is located at the connection of the first shell wall and the third shell wall.

43. The battery cell of any one of claims 36-42, wherein, A side supporting plate is arranged between the electrode assembly and the first shell wall.

44. The battery cell of any one of claims 36-43, wherein, At least one of the second shell walls is provided with a pressure relief portion configured to be able to release the pressure inside the shell, and the area of the orthographic projection of the pressure relief portion on the second shell wall is 7%-15% of the area of the second shell wall.

45. The battery cell of claim 44, wherein, The capacity of the battery cell is Q, the area of the orthographic projection of the pressure relief portion on the second shell wall 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 .

46. The battery cell of any one of claims 36-45, wherein, The positive electrode tab 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, and the positive electrode current collector comprises a positive electrode main body and at least one positive electrode tab, and the positive electrode main body is connected to the positive electrode tab. The second shell wall is provided with an electrode terminal, and the positive electrode tab and the negative electrode tab are respectively electrically connected to the electrode terminals on the two second shell walls, wherein a folding structure is arranged between the second shell wall electrically connected to the positive electrode tab and the positive electrode main body, and the folding structure is configured to fold the plurality of positive electrode tabs.

47. The battery cell of claim 46, wherein, A chamfer is arranged at the edge of the positive electrode tab along the length direction of the first shell wall.

48. The battery cell of claim 46 or 47, wherein, The total width of the positive electrode tab along the width direction of the positive electrode main body accounts for 30%-100% of the total width of the positive electrode main body; and / or, the total width of the negative electrode tab along the width direction of the negative electrode main body accounts for 30%-100% of the total width of the negative electrode main body.

49. The battery cell of claim 48, wherein, The size of the positive electrode tab along the width direction of the positive electrode main body is 50%-80% of the size of the positive electrode main body.

50. The battery cell of any one of claims 46-49, wherein, The second shell wall connected to the negative electrode tab is provided with a liquid injection hole.

51. The battery cell of claim 50, 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 be able to release the pressure inside the shell.

52. The battery cell of any one of claims 46-51, wherein, At least one mounting hole is arranged on the electrode terminal, and a pole is arranged in the mounting hole and riveted with the tab.

53. The battery cell of any one of claims 46-51, wherein, At least two mounting holes are arranged on the electrode terminal, and each pole is arranged in the mounting hole and riveted with the tab.

54. The battery cell of claim 52 or 53, wherein, The diameter of the pole is 3mm-8mm.

55. The battery cell of any one of claims 52-54, wherein, The poles riveted with the positive electrode tabs and the poles riveted with the negative electrode tabs are arranged in a staggered manner along the length direction of the first shell wall, and optionally, the poles riveted with the positive electrode tabs and the poles riveted with the negative electrode tabs are arranged in a diagonal manner along the length direction of the first shell wall.

56. The battery cell of any one of claims 52-55, wherein, The pole and the tab are electrically connected through an adapter plate.

57. The battery cell of any one of claims 52-56, wherein, The pole and the tab are directly electrically connected.

58. A battery device, wherein, The battery device includes at least one of a battery module, a battery pack, an energy storage device.

59. An electrical device, comprising: The battery device includes at least one of a battery module, a battery pack, an energy storage device.

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