Battery monomer, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. In the battery monomer, a positive active material comprises lithium-containing phosphate with an olivine structure, and in a cross section of a positive film layer along a thickness direction, the lithium-containing phosphate with the olivine structure comprises first lithium-containing phosphate particles with a longest diameter of 0.05-0.3 [mu] m and second lithium-containing phosphate particles with a longest diameter of 1-3 [mu] m; the average particle diameter Dv50 of the negative electrode active material is 8 [mu] m to 15 [mu] m, and the negative electrode active material includes graphite.

Description

[0001] This application claims the priority of PCT patent application PCT / CN2024 / 116594 titled "Battery Cell, Battery Device and Electrical Device" filed on September 3, 2024, the entire content of which is incorporated herein by reference. Technical Field

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

[0003] In recent years, batteries have been widely used in energy storage power systems such as hydro, thermal, wind and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the popularization of battery applications, higher requirements have also been put forward for their energy density, fast charging performance, cycle performance, service life, safety performance, etc. Summary of the Invention

[0004] The purpose of this application is to provide a new type of battery cell, which has excellent fast charging performance and can also take into account having a lower DC internal resistance, a higher energy density and better cycle performance.

[0005] To achieve the above object, a first aspect of this application provides a battery cell, including a positive electrode plate, a negative electrode plate and a separator located between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive current collector and at least one positive electrode film layer provided on the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate with an olivine structure includes a first lithium-containing phosphate particle with a longest diameter of 0.05 μm to 0.3 μm and a second lithium-containing phosphate particle with a longest diameter of 1 μm to 3 μm; the negative electrode plate includes a negative current collector and at least one negative electrode film layer provided on the surface of the negative current collector. The negative electrode film layer includes a negative electrode active material, the average particle size Dv50 of the negative electrode active material is 8 μm to 15 μm, and the negative electrode active material includes graphite.

[0006] By using a negative electrode active material with a small particle size, the present application improves the transmission path of lithium ions inside the negative electrode active material during charging, which is beneficial to improving the fast charging ability of the battery cell. However, when the fast charging ability of the battery cell is improved, the corresponding charging current it can withstand also increases. At this time, if the positive electrode active material is not reasonably arranged, it will cause the heat generated inside the battery cell to accumulate during fast charging, the internal temperature of the battery to rise, and adverse reactions such as gas generation in the electrolyte and an increase in the impedance of the solid electrolyte interface membrane (SEI membrane) of the negative electrode to occur, thereby increasing the internal resistance of the battery and affecting the cycle performance of the battery cell. The present application effectively reduces the heat accumulation inside the battery cell and the internal temperature rise of the battery cell by reasonably selecting lithium-containing phosphates with different sizes as the positive electrode active material and using a mixture of large and small particles, and inhibits the growth of the direct current internal resistance (DCR) of the battery cell; at the same time, it improves the energy density of the battery cell.

[0007] In the battery cell provided by the present application, when the positive electrode active material contains lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm, it can further improve the direct current internal resistance of the battery cell, thereby further reducing the heat generation of the battery and enabling the battery to have excellent safety performance.

[0008] In the battery cell provided by the present application, when the lithium-containing phosphate serving as the positive electrode active material contains first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm at the same time, the tap density of the electrode can be effectively improved by grading the large and small particles, so that the battery cell also has a relatively high energy density.

[0009] In any embodiment, the average particle size Dv50 of the negative electrode active material is 9.5 μm to 11.5 μm.

[0010] When the negative electrode active material (such as graphite) has a particle size within the above range, it can further improve the fast charging performance and direct current internal resistance of the battery, and at the same time enable the battery to have good cycle performance.

[0011] In any embodiment, the specific surface area of the negative electrode active material is 3m 2 / g to 8m 2 / g.

[0012] In any embodiment, the specific surface area of the negative electrode active material is 4m 2 / g to 6m 2 / g.

[0013] When the negative electrode active material (such as graphite) has a specific surface area within the above range, it can further accelerate the insertion and extraction rate of lithium ions between the graphite layers, thereby further improving the fast charging performance of the battery.

[0014] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction, the number of the first lithium-containing phosphate particles is greater than the number of the second lithium-containing phosphate particles.

[0015] In the lithium-containing phosphate as the positive electrode active material, when the number of the first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm is greater than the number of the second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm, the DC internal resistance and fast charging performance of the battery can be further improved while taking both into account.

[0016] In any embodiment, the general formula of the lithium-containing phosphate with an olivine structure is shown in Formula I, Li x A y Me a M b P 1-c X c Y z Formula I, wherein, 0.1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1.3, and 0.9 ≤ x + 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, and Mg; Me includes one or more of Mn, Fe, Co, and 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, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0017] When the lithium-containing phosphate as the positive electrode active material has the above chemical general formula, the energy density of the battery can be further improved.

[0018] In any embodiment, M includes one or more of Al, Ti, V, and Mg.

[0019] In any embodiment, the positive electrode active material satisfies at least one of the following conditions: (1) The positive electrode active material contains Al element, and the mass content is 0.01% to 0.05% based on the total mass of the positive electrode active material; (2) The positive electrode active material contains Ti element, and the mass content is 0.01% to 0.03% based on the total mass of the positive electrode active material; (3) The positive electrode active material contains V element, and the mass content is 0.1% to 0.3% based on the total mass of the positive electrode active material; (4) The positive electrode active material contains Mg element, and the mass content is 0.001% to 0.01% based on the total mass of the positive electrode active material.

[0020] When the lithium-containing phosphate as the positive electrode active material contains elements such as Al, Ti, V, and Mg, the specific capacity per gram can be further improved.

[0021] In any embodiment, the tap density of the positive electrode plate is 2.3 g / cm 3 to 2.6 g / cm 3 .

[0022] In any embodiment, the tap density of the positive electrode plate is 2.4 g / cm 3 to 2.55 g / cm 3 .

[0023] When the tap density of the positive electrode plate is within the above range, the energy density of the battery can be further improved while ensuring the kinetic performance.

[0024] In any embodiment, the areal density of the single-sided positive electrode film layer is 0.33 g / 1540.25 mm 2 to 0.4 g / 1540.25 mm 2 .

[0025] In any embodiment, the areal density of the single-sided positive electrode film layer is 0.335 g / 1540.25 mm 2 to 0.38 g / 1540.25 mm 2 .

[0026] In the battery cell provided by this application, when the coating areal density of the positive electrode film layer is within the above range, the energy density of the battery can be further improved, and the influence of thick coating on the electrochemical performance can be avoided, thereby further improving the fast charging performance of the battery.

[0027] In any embodiment, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0028] In any embodiment, the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 5 to 12.

[0029] In any embodiment, the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 6 to 10.

[0030] In the battery cell provided by the present application, when the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is within the above range, the energy density and fast charging performance of the battery can be further balanced.

[0031] In any embodiment, the tap density of the negative electrode tab is 1.3 g / cm 3 to 1.6 g / cm 3 .

[0032] In any embodiment, the tap density of the negative electrode tab is 1.35 g / cm 3 to 1.55 g / cm 3 .

[0033] When the tap density of the negative electrode tab is within the above range, the energy density of the battery can be further improved while ensuring the kinetic performance.

[0034] In any embodiment, the areal density of the single-sided negative electrode film layer is 0.15 g / 1540.25 mm 2 to 0.19 g / 1540.25 mm 2 .

[0035] In any embodiment, the areal density of the single-sided negative electrode film layer is 0.15 g / 1540.25 mm 2 to 0.165 g / 1540.25 mm 2 .

[0036] In the battery cell provided by the present application, when the coating areal density of the negative electrode film layer is within the above range, the energy density of the battery can be further improved, and the influence of thick coating on the electrochemical performance can be avoided, thereby further improving the fast charging performance of the battery.

[0037] In any embodiment, the thickness of the negative electrode current collector is 4 μm to 6 μm.

[0038] In any embodiment, the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 12 to 20.

[0039] In any embodiment, the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 13 to 20.

[0040] In the battery cell provided by the present application, when the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is within the above range, the energy density and fast charging performance of the battery can be further balanced.

[0041] In any embodiment, the negative electrode current collector includes a negative electrode current collecting portion, the negative electrode film layer includes a first negative electrode active material layer provided on the surface of the negative electrode current collecting portion and a second negative electrode active material layer provided on the side of the first negative electrode active material layer away from the negative electrode current collecting portion. The negative electrode active material in the first negative electrode active material layer includes first artificial graphite, the negative electrode active material in the second negative electrode active material layer includes second artificial graphite, and the average particle size Dv50 of the first artificial graphite is greater than the average particle size Dv50 of the second artificial graphite.

[0042] In any embodiment, the average particle size Dv50 of the first artificial graphite is 11 μm to 15 μm.

[0043] In any embodiment, the average particle size Dv50 of the second artificial graphite is 8 μm to 15 μm.

[0044] In any embodiment, the average particle size Dv50 of the second artificial graphite is 9.5 μm to 11.5 μm.

[0045] In the battery cell provided by the present application, when the above double-layer coating scheme is adopted in the negative electrode film layer, the kinetic performance of the battery can be further improved.

[0046] In any embodiment, the battery cell further includes an electrolyte, the electrolyte contains an organic solvent, and the organic solvent includes a carboxylic acid ester solvent and a carbonate solvent.

[0047] In the battery cell provided by the present application, when the above type of organic solvent is adopted in the electrolyte, the kinetic performance of the battery can be further improved.

[0048] In any embodiment, the organic solvent includes a linear carboxylic acid ester, and the mass ratio of the linear carboxylic acid ester is 40% to 75% based on the total mass of the electrolyte.

[0049] In any embodiment, the linear carboxylic acid ester has the structural general formula of R 1 -COO-R 2 wherein R 1 and R 2 each independently include one or more of an alkyl group of C 1 ~C 5 and a haloalkyl group of C 1 ~C 5

[0050] In any embodiment, the linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0051] When the above types and mass ratios of linear carboxylic esters are used as organic solvents in the electrolyte, due to the low viscosity of the linear carboxylic esters, they can effectively improve the conductivity of the electrolyte, thereby further improving the fast charging performance of the battery.

[0052] In any embodiment, the organic solvent includes a carbonate solvent, the carbonate solvent includes a linear carbonate and a cyclic carbonate, and the mass ratio of the linear carbonate is 10% to 40% based on the total mass of the electrolyte.

[0053] In any embodiment, the cyclic carbonate includes one or more of ethylene carbonate and propylene carbonate, and the linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0054] In any embodiment, the linear carbonate includes dimethyl carbonate, and the mass ratio of the dimethyl carbonate is 5% to 15% based on the total mass of the electrolyte.

[0055] When the above types and mass ratios of carbonates are used as organic solvents in the electrolyte, the side reactions and gas generation degree during the cycling of the battery can be improved, so that the battery can simultaneously have good cycling performance.

[0056] In any embodiment, the organic solvent includes dimethyl carbonate and a linear carboxylic ester, and the mass ratio of the linear carboxylic ester to the dimethyl carbonate is 2.0 to 7.0.

[0057] In any embodiment, the organic solvent includes dimethyl carbonate and a linear carboxylic ester, and the mass ratio of the linear carboxylic ester to the dimethyl carbonate is 3.0 to 6.0.

[0058] When dimethyl carbonate and a linear carboxylic ester with the above mass ratio are simultaneously used as organic solvents in the electrolyte, through the combination of the two solvents, the fast charging performance and cycling performance of the battery can be further improved.

[0059] In any embodiment, the electrolyte further includes a lithium salt, and the mass ratio of the lithium salt is 13% to 20% based on the total mass of the electrolyte.

[0060] In any embodiment, the lithium salt includes at least two of lithium hexafluorophosphate LiPF 6 and fluorosulfonimide salts, and the fluorosulfonimide salts include one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0061] Lithium hexafluorophosphate is not prone to gas generation during cycling, which can further improve the cycling performance of the battery; while the fluorosulfonimide salt has strong dissociation ability, which can further improve the fast charging performance of the battery.

[0062] In any embodiment, the lithium salt includes lithium hexafluorophosphate LiPF 6 and lithium bis(fluorosulfonyl)imide LiFSI.

[0063] In any embodiment, in the electrolyte, the mass ratio of lithium hexafluorophosphate LiPF 6 to lithium bis(fluorosulfonyl)imide LiFSI is from 1.2:1 to 2:1.

[0064] When lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide within the above mass ratio range are simultaneously used in the electrolyte, the fast charging performance and cycling performance of the battery can be further taken into account and improved.

[0065] In any embodiment, the electrolyte includes carbonate additives, and the carbonate additives include fluoroethylene carbonate FEC and vinylene carbonate VC.

[0066] In any embodiment, based on the total mass of the electrolyte, the mass fraction of the carbonate additives is from 0.5% to 7%.

[0067] In the battery cell provided by the present application, carbonate additives such as fluoroethylene carbonate and vinylene carbonate with a mass fraction within the above range are further added to the electrolyte, which can form a SEI film on the surface of the negative electrode, thereby reducing the side reactions occurring between the electrode sheet and the electrolyte, and further enabling the battery to have good cycling performance.

[0068] In any embodiment, the electrolyte includes vinylene carbonate VC, and the mass fraction of vinylene carbonate VC in the electrolyte is from 0.5% to 2%, based on the total mass of the electrolyte.

[0069] When vinylene carbonate within the above mass fraction range is added as an additive to the electrolyte, the formed SEI film is relatively stable, which is beneficial to further improving the cycling performance of the battery.

[0070] In any embodiment, the electrolyte includes fluoroethylene carbonate FEC, and the mass fraction of fluoroethylene carbonate FEC in the electrolyte is from 0.1% to 1%, based on the total mass of the electrolyte.

[0071] When fluoroethylene carbonate within the above mass fraction range is added as an additive to the electrolyte, the impedance of the formed SEI film is low, which can further improve the fast charging performance of the battery.

[0072] In any embodiment, the positive current collector includes a positive current collecting portion and at least two positive tabs provided on the same side of the positive current collecting portion. The positive tabs extend from the positive current collecting portion along a first direction. Among them, the distance between the centerlines of two adjacent positive tabs is 10 mm to 350 mm, and the centerline is parallel to the first direction; and / or, The negative current collector includes a negative current collecting portion and at least two negative tabs provided on the same side of the negative current collecting portion. The negative tabs extend from the negative current collecting portion along a first direction. Among them, the distance between the centerlines of two adjacent negative tabs is 10 mm to 350 mm, and the centerline is parallel to the first direction.

[0073] In any embodiment, the distance between the centerlines of two adjacent positive tabs is 20 mm to 330 mm; and / or, The distance between the centerlines of two adjacent negative tabs is 20 mm to 330 mm.

[0074] In the battery cell provided by the present application, when the positive and negative current collectors include at least two tabs having the above structural features, it can further improve the DC internal resistance of the battery cell, thereby further reducing the heat generation of the battery and making the battery have better safety performance.

[0075] In any embodiment, the battery cell further includes a top cover. The top cover includes a positive electrode terminal and a negative electrode terminal with opposite polarities. The positive electrode terminal and the negative electrode terminal are respectively used for electrically connecting with the positive tab and the negative tab.

[0076] In a conventional battery, a connecting piece is required to connect the electrode terminal and the tab, but this will reduce the utilization rate of the electrode assembly and the battery energy density. When the above structure is adopted in the battery cell provided by the present application, canceling the setting of the connecting piece can effectively solve this problem, reduce the battery internal resistance, and further take into account improving the battery energy density and fast charging performance.

[0077] In any embodiment, the size of the positive electrode film layer along the first direction is W 1 mm, and the size of the negative electrode film layer along the first direction is W 2 mm, where W 2 >W 1 , and the difference between W 2 and W 1 is 3 mm to 5 mm.

[0078] During the cycling of the battery, lithium ions that cannot be embedded in the negative electrode in time may form lithium dendrites on the surface of the negative electrode, deteriorating the cycling performance of the battery. In the battery cell provided by the present application, when the size W 2 of the negative electrode film layer and the size W1 When having the above relationship, it can improve the formation of lithium dendrites on the surface of the negative electrode by lithium ions, thereby enabling the battery to have good cycle performance at the same time.

[0079] In any embodiment, the battery cell further includes a housing, the housing is square, the thickness of the housing is 30 mm to 55 mm, the width is 150 mm to 250 mm, and the height is 90 mm to 120 mm.

[0080] When using a housing within the above size range, it can improve the energy density while reducing the internal resistance of the battery, thereby improving the energy density and fast charging performance of the battery.

[0081] In any embodiment, the battery cell is configured to have a charging time of 10 min to 17 min from 10% SOC to 80% SOC at room temperature.

[0082] The battery cell provided by the present application has excellent fast charging performance.

[0083] The second aspect of the present application further provides a battery device, including the battery cell of the first aspect of the present application, and the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0084] The third aspect of the present application further provides an electrical device, including the battery cell of the first aspect of the present application or the battery device of the second aspect of the present application. Description of the Drawings

[0085] Figure 1 is one of the schematic diagrams of the size of the electrode sheet film layer in an embodiment of the present application; Figure 2 is the second of the schematic diagrams of the size of the electrode sheet film layer in an embodiment of the present application; Figure 3 is the third of the schematic diagrams of the size of the electrode sheet film layer in an embodiment of the present application; Figure 4 is the electron microscope observation result diagram of the longitudinal section of the positive electrode sheet in an embodiment of the present application; Figure 5 is the schematic diagram of the electrode sheet in an embodiment of the present application; Figure 6 is the exploded view of the battery cell in an embodiment of the present application; Figure 7 is the first of the schematic diagrams of the battery cell in an embodiment of the present application; Figure 8 is the second of the schematic diagrams of the battery cell in an embodiment of the present application; Figure 9 is the third of the schematic diagrams of the battery cell in an embodiment of the present application; Figure 10 is a schematic diagram of a battery cell according to an embodiment of the present application; Figure 11 is Figure 10 an exploded view of the battery cell according to an embodiment of the present application shown; Figure 12 is a schematic diagram of a battery module according to an embodiment of the present application; Figure 13 is a schematic diagram of a battery pack according to an embodiment of the present application; Figure 14 is Figure 13 an exploded view of the battery pack according to an embodiment of the present application shown; Figure 15 is a schematic diagram of an electrical device using the battery cell according to an embodiment of the present application as a power source.

[0086] Description of reference numerals: 1 battery pack; 2 upper box body; 3 lower box body; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 top cover assembly; 10 battery cell; 11 current collector; 11a current collecting portion; 111a positive current collecting portion; 112a negative current collecting portion; 11b tab; 111b positive tab; 112b negative tab; F1 first direction; W 1 dimension of the positive electrode film layer in the first direction; W 2 dimension of the negative electrode film layer in the first direction; L center line; 13 top cover; 131 electrode terminal; 14 housing. Detailed embodiments

[0087] Hereinafter, embodiments of the battery cell and the electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0088] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0089] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0090] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0091] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0092] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can also mean that only the listed components are included or comprised.

[0093] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or present) and B is false (or absent); A is false (or absent) while B is true (or present); or both A and B are true (or present).

[0094] In recent years, with the increasing demand for batteries as an energy source, higher requirements have been put forward for the comprehensive performance of batteries. Compared with ternary lithium nickel cobalt manganese oxide batteries, lithium iron phosphate batteries have become the mainstream in the secondary battery market due to their low cost, good safety, and good cycling performance. However, the rate performance of lithium iron phosphate batteries has become a bottleneck for their wider application, especially under the premise of higher demand for energy density, it is more difficult to improve the rate performance. This application aims to obtain a battery with fast charging and good energy density through reasonable matching of the particle sizes of the positive and negative electrodes of the lithium iron phosphate battery.

[0095] Based on this, this application provides a battery cell, including a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive electrode film layer provided on at least one surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate with an olivine structure includes a first lithium-containing phosphate particle with a longest diameter of 0.05 μm to 0.3 μm and a second lithium-containing phosphate particle with a longest diameter of 1 μm to 3 μm; the negative electrode sheet includes a negative current collector and a negative electrode film layer provided on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material, and the average particle size Dv50 of the negative electrode active material is 8 μm to 15 μm, and the negative electrode active material includes graphite.

[0096] As used herein, "average particle size Dv50" refers to: in the particle size distribution of particles, starting from the small particle size side, the particle size corresponding to the cumulative volume distribution percentage reaching 50%. Its measurement method can refer to GB / T19077-2016 / ISO13320:2009 and be measured using a Malvern 2000 (MasterSizer 2000) laser particle size analyzer.

[0097] In some embodiments, since the first lithium-containing phosphate and the second lithium-containing phosphate have been fully mixed and evenly coated on the current collector to form the positive electrode film layer during the preparation of the slurry, therefore, any cross-section taken along the thickness direction of the electrode sheet can represent the particle size and distribution of the lithium-containing phosphate in the entire electrode sheet; when selecting the cross-section, it is preferred to select a relatively flat cross-section in the middle of the electrode sheet to more clearly observe the distribution of the lithium-containing phosphate therein.

[0098] In some embodiments, the "longest diameter" means: cutting the positive electrode sheet including lithium-containing phosphate particles along the thickness direction of the sheet to expose the longitudinal section of the positive electrode film layer; determining the longest diameter of the lithium-containing phosphate particles by performing a scanning electron microscope (SEM) test on the longitudinal section of the positive electrode film layer.

[0099] Specifically, among the distances between any two points on the outer peripheral edge line of the lithium-containing phosphate particles, the maximum value is the "longest diameter" of the particles. In some embodiments, as Figure 4 shown in the longitudinal section of the electrode sheet along the thickness direction, which shows the longest diameter of a single particle satisfying the first lithium-containing phosphate particles (with a longest diameter of 0.05 μm to 0.3 μm), and also shows the shortest diameter of a single particle satisfying the second lithium-containing phosphate particles (with a longest diameter of 1 μm to 3 μm).

[0100] It should be noted that the first lithium-containing phosphate particle material with a smaller size having a longest diameter of 0.05 μm to 0.3 μm is one of the positive electrode active materials of the battery monomer of the present application, and the particle size range of 0.05 μm to 0.3 μm is a characteristic parameter of the material itself.

[0101] The second lithium-containing phosphate particle material with a larger size having a longest diameter of 1 μm to 3 μm is one of the positive electrode active materials of the battery monomer of the present application, and the particle size range of 1 μm to 3 μm is a characteristic parameter of the material itself.

[0102] Those skilled in the art can mix the lithium-containing phosphate particle materials in the above two size ranges according to actual needs.

[0103] By adopting a small-particle-size negative electrode active material in the present application, the transmission path of lithium ions inside the negative electrode active material during charging is improved, which is beneficial to improving the fast charging ability of the battery monomer. However, when the fast charging ability of the battery monomer is improved, the corresponding charging current it bears also increases. At this time, if the positive electrode active material is not set reasonably, it will lead to the aggregation of internal heat generation in the battery monomer during fast charging, the increase of the internal temperature of the battery, and adverse reactions such as gas generation in the electrolyte and an increase in the impedance of the solid electrolyte interface film of the negative electrode, thereby increasing the battery internal resistance and affecting the cycle performance of the battery monomer. By reasonably selecting lithium-containing phosphates of different sizes as the positive electrode active material in the present application, the heat aggregation inside the battery monomer is effectively reduced by mixing large and small particles, the internal temperature rise of the battery monomer is reduced, and the increase of the DC internal resistance of the battery monomer is inhibited; at the same time, the energy density of the battery monomer is also improved.

[0104] [Positive electrode sheet] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0105] In some embodiments, the positive electrode film layer includes a positive electrode active material.

[0106] In some embodiments, the positive electrode active material includes a lithium-containing phosphate in an olivine structure.

[0107] In some embodiments, the general formula of the composition of the lithium-containing phosphate in the olivine structure is as shown in Formula I, Li x A y Me a M b P 1-c X c Y z Formula I, where 0.1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1.3, and 0.9 ≤ x + 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, and Mg; Me includes one or more of Mn, Fe, Co, and 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, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0108] As used herein, "the general formula of the composition of the lithium-containing phosphate in the olivine structure is as shown in Formula I" is not limited to the substances represented by the molecular general formula, but also includes other substances formed by further appropriate modification on the basis of the molecular general formula, which are not limited herein. The use of "general formula" is only for convenience of description and is not intended to limit the present application. It can be understood that materials obtained by appropriate modification on the basis of the listed positive electrode active substances are also within the scope of the positive electrode active substances. The aforementioned appropriate modification refers to the acceptable modification methods for the positive electrode active substances. Non-limiting examples include coating modification.

[0109] When the lithium-containing phosphate as the positive electrode active material has the above chemical general formula, it can further improve the structural stability of the positive electrode active material and improve the cycling performance of the battery cell.

[0110] In some embodiments, M includes one or more of Al, Ti, V, and Mg.

[0111] In some embodiments, the positive electrode active material contains Al element, and its mass content is 0.001% to 0.05%, optionally 0.01% to 0.05%. Based on the total mass of the positive electrode active material, for example, 0.001%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, etc., or other unlisted values within the range of 0.001% to 0.05%.

[0112] In some embodiments, the positive electrode active material contains Ti element, and its mass content is 0.001% to 0.03%, optionally 0.01 to 0.03%. Based on the total mass of the positive electrode active material, for example, 0.001%, 0.01%, 0.02%, 0.03%, etc., or other unlisted values within the range of 0.001% to 0.03%.

[0113] In some embodiments, the positive electrode active material contains V element, and its mass content is 0.001% to 0.3%, optionally 0.1 to 0.3%. Based on the total mass of the positive electrode active material, for example, 0.001%, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc., or other unlisted values within the range of 0.001% to 0.3%.

[0114] In some embodiments, the positive electrode active material contains Mg element, and the mass content is 0.001% to 0.01%. Based on the total mass of the positive electrode active material, it can be optionally 0.001%, 0.002%, 0.005%, 0.01%, or other unlisted values within the range of 0.001% to 0.01%.

[0115] When the lithium-containing phosphate as the positive electrode active material contains elements such as Al, Ti, V, and Mg, it can further improve the structural stability of the material and enhance the cycling performance.

[0116] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate with olivine structure includes a first lithium-containing phosphate particle with a longest diameter of 0.05 μm to 0.3 μm and a second lithium-containing phosphate particle with a longest diameter of 1 μm to 3 μm.

[0117] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate with olivine structure includes a first lithium-containing phosphate particle with a longest diameter of 0.05 μm to 0.3 μm, for example, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, etc., or other unlisted values within the range of 0.05 μm to 0.3 μm.

[0118] In some embodiments, in a cross-section of the positive electrode film layer in the thickness direction, the lithium-containing phosphate of the olivine structure includes second lithium-containing phosphate particles having a longest diameter of 1 μm to 3 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc., or other unlisted values within the range of 1 μm to 3 μm.

[0119] In the battery cell provided by the present application, when the lithium-containing phosphate particles having a longest diameter of 0.05 μm to 0.3 μm are included in the positive electrode active material, it can further improve the DC internal resistance of the battery cell, thereby further reducing the heat generation of the battery, and enabling the battery to have excellent safety performance.

[0120] In the battery cell provided by the present application, when the lithium-containing phosphate as the positive electrode active material simultaneously contains first lithium-containing phosphate particles having a longest diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles having a longest diameter of 1 μm to 3 μm, the tap density of the electrode sheet can be effectively improved by the method of grading of large and small particles, so that the battery cell also has a relatively high energy density.

[0121] In some embodiments, in a cross-section of the positive electrode film layer in the thickness direction, the number of the first lithium-containing phosphate particles is greater than the number of the second lithium-containing phosphate particles.

[0122] In the lithium-containing phosphate as the positive electrode active material, when the number of the first lithium-containing phosphate particles having a longest diameter of 0.05 μm to 0.3 μm is greater than the number of the second lithium-containing phosphate particles having a longest diameter of 1 μm to 3 μm, the improvement of the DC internal resistance and the fast charging performance of the battery can be further taken into account.

[0123] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0124] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The present application does not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0125] In some embodiments, the areal density of the single-sided positive electrode film layer is 0.33 g / 1540.25 mm 2 to 0.4 g / 1540.25 mm2 , such as 0.33 g / 1540.25mm 2 , 0.34 g / 1540.25mm 2 , 0.35 g / 1540.25mm 2 , 0.36 g / 1540.25mm 2 , 0.37 g / 1540.25mm 2 , 0.38 g / 1540.25mm 2 , 0.39 g / 1540.25mm 2 , 0.4 g / 1540.25mm 2 etc., or values other than those listed within the range of 0.33g / 1540.25mm 2 to 0.4 g / 1540.25mm 2 and other unlisted values within the range.

[0126] In some embodiments, the areal density of the single-sided positive electrode film layer is 0.335 g / 1540.25mm 2 to 0.38g / 1540.25mm 2 .

[0127] As used herein, the "areal density" of the positive electrode film layer or the negative electrode film layer has the meaning well-known in the art and can be tested by methods known in the art. For example, take a single-sided coated and cold-pressed negative electrode sheet (if it is a double-sided coated negative electrode sheet, the negative electrode film layer on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, and record it as M1. Then wipe off the negative electrode film layer of the above-mentioned weighed negative electrode sheet and weigh the weight of the negative electrode current collector, record it as M0, and the areal density of the negative electrode film layer = (the weight M1 of the negative electrode sheet - the weight M0 of the negative electrode current collector) / S1. To ensure the accuracy of the test results, multiple groups (for example, 10 groups) of samples to be tested can be tested and the average value can be calculated as the test result.

[0128] In the battery cell provided by the present application, when the coating areal density of the positive electrode film layer is within the above range, the energy density of the battery can be further improved, and the influence of thick coating on the electrochemical performance can be avoided, thereby further improving the fast charging performance of the battery.

[0129] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0130] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., or other unlisted values within the range of 10 μm to 15 μm.

[0131] In some embodiments, the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 5 to 12, such as 5, 6, 7, 8, 9, 10, 11, 12, etc., or other unlisted values within the range of 5 to 12.

[0132] In some embodiments, the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 6 to 10.

[0133] In the battery cell provided by the present application, when the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is within the above range, the thickness of the current collector is within a suitable range, which will not cause energy density loss due to excessive thickness, nor will it cause problems such as poor overcurrent capacity and low tensile strength resulting in pole piece cracking due to too thin thickness, further taking into account the improvement of the energy density and fast charging performance of the battery.

[0134] In some embodiments, as shown in Figure 5 FIG. 17, the current collector 11 includes a current collecting portion 11a and at least two tabs 11b provided on the same side of the current collecting portion 11a. The tabs 11b extend from the current collecting portion 11a along the first direction F1. Among them, the distance between the center lines L of two adjacent tabs 11b is 10 mm to 350 mm, and the center line L is parallel to the first direction F1, such as 10 mm, 20 mm, 40 mm, 60 mm, 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 340 mm, 350 mm, etc., or other unlisted values within the range of 10 mm to 350 mm.

[0135] In some embodiments, the distance between the centerlines L of two adjacent tabs 11b is from 20 mm to 330 mm, and the centerline L is parallel to the first direction F1. For example, 20 mm, 40 mm, 60 mm, 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 330 mm, etc., or other values not listed within the range of 20 mm to 330 mm.

[0136] In some embodiments, in combination with Figure 5 and Figure 6 as shown, the current collector 11 may be a positive current collector, and the tab 11b may be a positive tab 111b.

[0137] In some embodiments, in combination with Figure 5 and Figure 6 as shown, the current collector 11 may be a negative current collector, and the tab 11b may be a negative tab 112b.

[0138] In some embodiments, the positive current collector includes a positive current collecting portion and at least two positive tabs provided on the same side of the positive current collecting portion. The positive tabs extend from the positive current collecting portion in the first direction. Among them, the distance between the centerlines of two adjacent positive tabs is from 10 mm to 350 mm, and the centerline is parallel to the first direction. For example, 10 mm, 20 mm, 40 mm, 60 mm, 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 340 mm, 350 mm, etc., or other values not listed within the range of 10 mm to 350 mm.

[0139] In some embodiments, the distance between the centerlines of two adjacent positive tabs is from 20 mm to 330 mm. For example, 20 mm, 40 mm, 60 mm, 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 330 mm, etc., or other values not listed within the range of 20 mm to 330 mm.

[0140] In some embodiments, in combination with Figure 5 as shown, the centerline L refers to the symmetry axis passing through the midpoint of the tab 11b along the length direction of the current collector 11, and the centerline L is parallel to the first direction F1. In some embodiments, the dimensions of each tab 11b along the length direction of the current collector 11 are equal.

[0141] In some embodiments, in combination with Figure 5 As shown, the distance between the center lines L of two adjacent tab ears 11b includes S1 or S2, where S1 and S2 may be equal (in this case, the adjacent tab ears are equally spaced), and S1 and S2 may also be unequal (in this case, the adjacent tab ears are unequally spaced).

[0142] In the battery cell provided by the present application, when the positive and negative current collectors include at least two tab ears having the above structural characteristics, it can further improve the overcurrent capacity, improve the DC internal resistance of the battery cell, thereby further reducing the heat generation of the battery, and making the battery have better safety performance.

[0143] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0144] In some embodiments, the tap density of the positive electrode plate is 2.3 g / cm 3 to 2.6 g / cm 3 , such as 2.30 g / cm 3 , 2.35 g / cm 3 , 2.40 g / cm 3 , 2.45 g / cm 3 , 2.50 g / cm 3 , 2.55 g / cm 3 , 2.60 g / cm 3 , etc., or other unlisted values within the range of 2.3 g / cm 3 to 2.6 g / cm 3 .

[0145] In some embodiments, the tap density of the positive electrode plate is 2.4 g / cm 3 to 2.55 g / cm 3 .

[0146] When the tap density of the positive electrode plate is within the above range, it can further improve the energy density of the battery while ensuring the kinetic performance.

[0147] In some embodiments, the tap density of the positive electrode plate corresponds to the tap density of the positive electrode film layer of the battery cell in the 0% SOC state. The battery cell in the 0% SOC state refers to the state in which the battery cell is discharged to 2.0 V at 1 / 3 C and then discharged to 2.0 V at 0.05 C.

[0148] Negative electrode plate In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0149] In some embodiments, the negative electrode film layer includes a negative electrode active material.

[0150] In some embodiments, the average particle size Dv50 of the negative electrode active material is 8 μm to 15 μm, such as 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., or other unlisted values within the range of 8 μm to 15 μm. In some embodiments, the negative electrode active material includes graphite.

[0151] In the battery cell provided by the present application, when the negative electrode active material (such as graphite) has a particle size within the above range, it has a relatively large specific surface area, the migration channels between the graphite layers for lithium ions increase, and the migration path becomes shorter, thereby accelerating the intercalation and deintercalation rate of lithium ions between the graphite layers, enabling the battery cell to have good fast charging performance; at the same time, when the negative electrode active material (such as graphite) has a particle size within the above range, it can also improve the DC internal resistance of the battery cell, thereby reducing battery heat generation and enabling the battery to have good safety performance.

[0152] In some embodiments, the average particle size Dv50 of the negative electrode active material is 9.5 μm to 11.5 μm, such as 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, etc., or other unlisted values within the range of 9.5 μm to 11.5 μm.

[0153] When the negative electrode active material (such as graphite) has a particle size within the above range, it can further improve the fast charging performance and DC internal resistance of the battery, and at the same time enable the battery to have good cycle performance.

[0154] In some embodiments, the specific surface area of the negative electrode active material is 3 m 2 / g to 8 m 2 / g, such as 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, etc., or other unlisted values within the range of 3 m 2 / g to 8 m 2 / g.

[0155] In some embodiments, the specific surface area of the negative electrode active material is 4 m 2 / g to 6 m 2 / g, such as 4 m 2 / g, 4.5 m 2 / g, 5 m 2 / g, 5.5 m 2 / g, 6 m 2 / g, etc., or other unlisted values within the range of 4 m 2 / g to 6 m 2 / g.

[0156] As used herein, "specific surface area" refers to the total area per unit mass of the material. The measurement method can refer to GB / T19587-2017, and the nitrogen adsorption specific surface area analysis test method is used for testing and calculated by the BET (Brunauer Emmett Teller) method. Among them, the nitrogen adsorption specific surface area analysis test can be carried out by the Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics Company in the United States.

[0157] When the negative electrode active material (such as graphite) has a specific surface area within the above range, it can further accelerate the intercalation and deintercalation rate of lithium ions between the graphite layers, thereby further improving the fast charging performance of the battery.

[0158] In some embodiments, the negative electrode film layer includes at least two negative electrode active material layers. In some embodiments, the negative electrode current collector includes a negative electrode current collecting portion. The negative electrode film layer includes a first negative electrode active material layer disposed on the surface of the negative electrode current collecting portion and a second negative electrode active material layer disposed on the side of the first negative electrode active material layer away from the negative electrode current collecting portion. The negative electrode active material in the first negative electrode active material layer includes first artificial graphite, and the negative electrode active material in the second negative electrode active material layer includes second artificial graphite. The average particle size Dv50 of the first artificial graphite is greater than the average particle size Dv50 of the second artificial graphite. The particle size of the artificial graphite in the upper negative electrode film layer (the second negative electrode active material layer) is small because the upper graphite is in direct contact with the electrolyte and can respond to the intercalation of lithium ions more quickly than the lower graphite. Therefore, the small particle size of the upper graphite helps lithium ions to intercalate into the graphite more quickly and improves the electromagnetic fast charging ability. At the same time, using larger artificial graphite particles in the lower layer can reduce the probability of the graphite material being crushed, be more pressure-resistant, and improve the compaction density of the electrode sheet.

[0159] In some embodiments, the average particle size Dv50 of the first artificial graphite is from 11 μm to 15 μm, such as 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., or other values not listed within the range of 11 μm to 15 μm.

[0160] In some embodiments, the average particle size Dv50 of the second artificial graphite is from 8 μm to 15 μm, such as 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., or other values not listed within the range of 8 μm to 15 μm.

[0161] In some embodiments, the average particle size Dv50 of the second artificial graphite is from 9.5 μm to 11.5 μm, such as 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, etc., or other values not listed within the range of 9.5 μm to 11.5 μm.

[0162] In the battery cell provided by the present application, when the above double-layer coating scheme is adopted in the negative electrode film layer, the kinetic performance of the battery can be further improved.

[0163] In some embodiments, the negative electrode film layer may further optionally include a binder. The binder may 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).

[0164] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0165] In some embodiments, the negative electrode film layer may further optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0166] In some embodiments, the areal density of the single-sided negative electrode film layer is 0.15 g / 1540.25mm 2 to 0.19 g / 1540.25mm 2 , such as 0.15 g / 1540.25mm 2 、0.16 g / 1540.25mm 2 、0.17 g / 1540.25mm 2 、0.18 g / 1540.25mm 2 、0.19 g / 1540.25mm 2etc., or 0.15 g / 1540.25mm 2 to 0.19 g / 1540.25mm 2 Other unlisted values within the range.

[0167] In some embodiments, the areal density of the single-sided negative electrode film layer is 0.15 g / 1540.25mm 2 to 0.165 g / 1540.25mm 2 .

[0168] In the battery cell provided by the present application, when the coating areal density of the negative electrode film layer is within the above range, the energy density of the battery can be further improved, and the influence of thick coating on the electrochemical performance can be avoided, thereby further improving the fast charging performance of the battery.

[0169] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0170] In some embodiments, the thickness of the negative electrode current collector is 4μm to 6μm, such as 4μm, 4.5μm, 5μm, 5.5μm, 6μm, etc., or other unlisted values within the range of 4μm to 6μm.

[0171] In some embodiments, the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 12 to 20, such as 12, 13, 14, 15, 16, 17, 18, 19, 20, etc., or other unlisted values within the range of 12 to 20.

[0172] In some embodiments, the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 13 to 20.

[0173] In some embodiments, the single-sided thickness of the negative electrode film layer corresponds to the single-sided thickness of the negative electrode film layer of the battery cell in the 0% SOC state. The battery cell in the 0% SOC state refers to the state in which the battery cell is discharged to 2.0V at 1 / 3C and then discharged to 2.0V at 0.05C. In the battery cell provided by the present application, when the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is within the above range, the improvement of the energy density and the fast charging performance of the battery can be further balanced.

[0174] In some embodiments, the negative electrode current collector includes a negative electrode current collecting portion and at least two negative electrode tabs disposed on the same side of the negative electrode current collecting portion. The negative electrode tabs extend from the negative electrode current collecting portion in a first direction. The distance between the centerlines of two adjacent negative electrode tabs is 10 mm to 350 mm, and the centerlines are parallel to the first direction. For example, 10 mm, 20 mm, 40 mm, 60 mm, 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 340 mm, 350 mm, etc., or other values not listed within the range of 10 mm to 350 mm.

[0175] In some embodiments, the distance between the centerlines of two adjacent negative electrode tabs is 20 mm to 330 mm. For example, 20 mm, 40 mm, 60 mm, 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 330 mm, etc., or other values not listed within the range of 20 mm to 330 mm.

[0176] In the battery cell provided by the present application, when the positive and negative electrode current collectors include at least two tabs having the above structural features, the overcurrent capacity can be further improved, the DC internal resistance of the battery cell can be improved, thereby further reducing the heat generation of the battery, and making the battery have better safety performance.

[0177] In some embodiments, the size of the positive electrode film layer in the first direction is W 1 mm, and the size of the negative electrode film layer in the first direction is W 2 mm, where W 2 >W 1 , and the difference between W 2 and W 1 is 3 mm to 5 mm. For example, 3 mm, 3.2 mm, 3.4 mm, 3.6 mm, 3.8 mm, 4 mm, 4.2 mm, 4.4 mm, 4.6 mm, 4.8 mm, 5 mm, etc., or other values not listed within the range of 3 mm to 5 mm.

[0178] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0179] In some embodiments, the battery cell is a wound battery. Combining Figure 3As shown, after the electrode sheet is unfolded from the wound state, the positive current collector includes a positive current collecting portion 111a and at least two positive electrode tabs 111b provided on the same side of the positive current collecting portion 111a. The positive electrode tabs 111b extend from the positive current collecting portion 111a along the first direction F1. The negative current collector includes a negative current collecting portion 112a and at least two negative electrode tabs 112b provided on the same side of the negative current collecting portion 112a. The negative electrode tabs 112b extend from the negative current collecting portion 112a along the first direction F1. Wherein, the size W of the negative electrode film layer in the first direction 2 > the size W of the positive electrode film layer in the first direction 1 , and the difference is 3 mm to 5 mm.

[0180] In some embodiments, the battery cell is a stacked battery. As shown in combination with Figure 1 and Figure 2 , each electrode sheet becomes an electrode assembly in a stacked state. Among them, each positive electrode sheet includes a positive current collector. The positive current collector includes a positive current collecting portion 111a and a positive electrode tab 111b provided on the positive current collecting portion 111a. The positive electrode tab 111b extends from the positive current collecting portion 111a along the first direction F1. Each negative electrode sheet includes a negative current collector. The negative current collector includes a negative current collecting portion 112a and a negative electrode tab 112b provided on the negative current collecting portion 112a. The negative electrode tab 112b extends from the negative current collecting portion 112a along the first direction F1. Wherein, the size W of the negative electrode film layer in the first direction 2 > the size W of the positive electrode film layer in the first direction 1 , and the difference is 3 mm to 5 mm.

[0181] During the cycling of the battery, lithium ions that cannot be embedded in the negative electrode in time may form lithium dendrites on the surface of the negative electrode, deteriorating the cycling performance of the battery. In the battery cell provided in the present application, when the size W of the negative electrode film layer 2 and the size W of the positive electrode film layer 1 have the above relationship, the formation of lithium dendrites on the surface of the negative electrode can be improved, so that the battery can simultaneously have good cycling performance.

[0182] In some embodiments, the negative electrode sheet can be prepared by the following method: dispersing the above components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, 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 processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0183] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cm 3 to 1.6 g / cm3 , such as 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 and so on, or other unlisted values within the range of 1.3 g / cm 3 to 1.6 g / cm 3 .

[0184] In some embodiments, the tap density of the negative electrode tab is 1.35 g / cm 3 to 1.55 g / cm 3 , such as 1.35 g / cm 3 , 1.40 g / cm 3 , 1.45 g / cm 3 , 1.50 g / cm 3 , 1.55 g / cm 3 and so on, or other unlisted values within the range of 1.35 g / cm 3 to 1.55 g / cm 3 .

[0185] In some embodiments, the tap density of the negative electrode tab corresponds to the tap density of the negative electrode film layer of the battery cell corresponding to the 0% SOC state. The battery cell in the 0% SOC state refers to the state where the battery cell is discharged at 1 / 3C to 2.0V and then discharged at 0.05C to 2.0V.

[0186] When used herein, the "tap density" of the electrode tab is: tap density = areal density / (electrode tab thickness - current collector thickness), and its measurement method can refer to GB / T24533-2009.

[0187] When the tap density of the negative electrode tab is within the above range, the energy density of the battery can be further improved while ensuring the kinetic performance.

[0188] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode tab and the negative electrode tab. For example, the electrolyte can be liquid, solid or gel state.

[0189] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and an organic solvent.

[0190] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, the composition of the electrolyte can be measured by liquid chromatography, gas chromatography, ion chromatography, liquid nuclear magnetic resonance, etc. Exemplarily, qualitative and quantitative analysis of the organic components in the electrolyte can be carried out by gas chromatography with reference to GB / T9722-2006 General Rules for Gas Chromatography of Chemical Reagents.

[0191] In the embodiments of the present application, the test sample can be a newly prepared electrolyte as the sample, or the battery is discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC), and the free electrolyte obtained from the battery is used as the sample.

[0192] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentration in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, qualitative or quantitative analysis of the inorganic components / lithium salt concentration in the electrolyte can be carried out by ion chromatography with reference to the standard JY / T020-1996 General Rules for Ion Chromatographic Analysis. In the embodiments of the present application, a newly prepared electrolyte can be taken as the sample, or the battery is discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC), and the free electrolyte obtained from the battery is used as the sample, and ion chromatography analysis method is used for detection.

[0193] In some embodiments, the organic solvent includes a carboxylic acid ester solvent and a carbonate solvent.

[0194] In the battery cell provided by the present application, when the above types of organic solvents are used in the electrolyte, the kinetic performance of the battery can be further improved.

[0195] In some embodiments, the organic solvent includes a linear carboxylic acid ester. Based on the total mass of the electrolyte, the mass ratio of the linear carboxylic acid ester is 40% to 75%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, etc., or other unlisted values within the range of 40% to 75%.

[0196] In some embodiments, the linear carboxylic acid ester has the general structural formula of R 1 -COO-R 2 wherein R 1 and R 2 each independently includes one or more of an alkyl group of C 1 ~C 5 and a haloalkyl group of C 1 ~C 5 .

[0197] In some embodiments, the linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0198] When the above types and mass ratios of linear carboxylic acid esters are used as organic solvents in the electrolyte, due to the low viscosity of the linear carboxylic acid esters, they can effectively improve the conductivity of the electrolyte, thereby further improving the fast charging performance of the battery.

[0199] In some embodiments, the organic solvent includes a carbonate solvent, and the carbonate solvent includes a linear carbonate and a cyclic carbonate. Based on the total mass of the electrolyte, the mass ratio of the linear carbonate is 10% to 40%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc., or other unlisted values within the range of 10% to 40%.

[0200] In some embodiments, the cyclic carbonate includes one or more of ethylene carbonate and propylene carbonate, and the linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0201] In some embodiments, the linear carbonate includes dimethyl carbonate. Based on the total mass of the electrolyte, the mass ratio of dimethyl carbonate is 5% to 15%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., or other unlisted values within the range of 5% to 15%.

[0202] When the above types and mass ratios of carbonates are used as organic solvents in the electrolyte, the side reactions and gas generation during the cycling of the battery can be improved, so that the battery can simultaneously have good cycling performance.

[0203] In some embodiments, the organic solvent includes dimethyl carbonate and a linear carboxylic acid ester, and the mass ratio of the linear carboxylic acid ester to dimethyl carbonate is 2.0 to 7.0, such as 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, etc., or other unlisted values within the range of 2.0 to 7.0.

[0204] In some embodiments, the organic solvent includes dimethyl carbonate and a linear carboxylic acid ester, and the mass ratio of the linear carboxylic acid ester to dimethyl carbonate is 3.0 to 6.0.

[0205] When dimethyl carbonate and a linear carboxylic acid ester with the above mass ratio are simultaneously used as organic solvents in the electrolyte, through the combination of the two solvents, the fast charging performance and cycling performance of the battery can be further improved simultaneously.

[0206] In some embodiments, the electrolyte further includes a lithium salt, such as at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro-bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0207] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the lithium salt is 13% to 20%, such as 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., or other unlisted values within the range of 13% to 20%.

[0208] In some embodiments, the lithium salt includes lithium hexafluorophosphate LiPF 6 and at least two of fluorosulfonylimide salts, and the fluorosulfonylimide salts include one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0209] The fluorosulfonylimide salt has strong dissociation ability. When used in combination with lithium hexafluorophosphate, it can further improve the fast charging performance of the battery. However, an excessive content of LiTFSI will reduce the safety performance of the battery, especially making the thermal runaway of the battery more severe.

[0210] In some embodiments, the lithium salt includes lithium hexafluorophosphate LiPF 6 and lithium bis(fluorosulfonyl)imide LiFSI.

[0211] In some embodiments, in the electrolyte, the mass ratio of lithium hexafluorophosphate LiPF 6 to lithium bis(fluorosulfonyl)imide LiFSI is 1.2:1 to 2:1, such as 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, etc., or other unlisted values within the range of 1.2:1 to 2:1.

[0212] When lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide within the above mass ratio range are simultaneously used in the electrolyte, it can further balance the improvement of the fast charging performance and cycling performance of the battery.

[0213] In some embodiments, the electrolyte further includes additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain performance of the battery, such as additives for improving the overcharging performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0214] In some embodiments, the electrolyte includes a carbonate additive, and the carbonate additive includes fluoroethylene carbonate (FEC) and vinylene carbonate (VC).

[0215] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 0.5% to 7%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 6.5%, 7%, etc., or other unlisted values within the range of 0.5% to 7%.

[0216] In the battery cell provided by the present application, a carbonate additive with a mass percentage within the above range, such as fluoroethylene carbonate and vinylene carbonate, is further added to the electrolyte. It can form a SEI film on the surface of the negative electrode, thereby reducing the side reactions occurring between the electrode sheet and the electrolyte, and further enabling the battery to have good cycle performance.

[0217] In some embodiments, the electrolyte includes vinylene carbonate (VC). Based on the total mass of the electrolyte, the mass percentage of vinylene carbonate (VC) in the electrolyte is 0.5% to 2%, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc., or other unlisted values within the range of 0.5% to 2%.

[0218] When vinylene carbonate within the above mass percentage range is added as an additive to the electrolyte, the formed SEI film is relatively stable, which is beneficial to further improving the cycle performance of the battery.

[0219] In some embodiments, the electrolyte includes fluoroethylene carbonate (FEC). Based on the total mass of the electrolyte, the mass percentage of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 1%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc., or other unlisted values within the range of 0.1% to 1%.

[0220] When fluoroethylene carbonate within the above mass percentage range is added as an additive to the electrolyte, the impedance of the formed SEI film is low, which can further improve the fast charging performance of the battery.

[0221] In some embodiments, the types and masses of additives and solvents in the electrolyte can be obtained by detecting the electrolyte through methods well-known to those skilled in the art. For example, the composition of the electrolyte can be measured by liquid chromatography, gas chromatography, ion chromatography, liquid nuclear magnetic resonance, etc. Exemplarily, the electrolyte is diluted 3 - 10 times with acetonitrile to obtain a diluted electrolyte solution for testing. Using a GC-MS 3100 organic component gas chromatograph, the above-mentioned diluted electrolyte solution is placed in the instrument for full-scan qualitative analysis. The inlet temperature is 250°C, and the scanning range is 35μm - 270μm. After the test is completed, the total ion current chromatogram of each organic substance is obtained. The types of corresponding organic substances are compared according to the peak positions of the chromatogram, and the percentage content of each organic substance is calculated according to the peak areas.

[0222] In this application, the qualitative and quantitative analysis of each substance or each element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative analysis, or several detection methods can be used in combination for qualitative or quantitative determination.

[0223] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art, such as gas chromatography, liquid chromatography, liquid nuclear magnetic resonance, etc.

[0224] In the embodiments of this application, newly prepared electrolyte can be taken as a sample, or the battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse.

[0225] [Separator] In some embodiments, the battery cell further includes a separator. This application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0226] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0227] [Battery cell] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be made into an electrode assembly through a winding process or a stacking process.

[0228] In some embodiments, the positive current collector, the separator, the negative current collector, and the separator are stacked in sequence and wound together; after winding, the positive current collector tabs 111b of the positive current collector are aligned and stacked, and the negative current collector tabs 112b of the negative current collector are aligned and stacked, as Figure 6 shown.

[0229] In some embodiments, the battery cell further includes a top cover, and the top cover includes electrode terminals with opposite polarities for electrically connecting to the positive current collector tab or the negative current collector tab.

[0230] In some embodiments, as Figure 6 shown, the battery cell 10 further includes a top cover 13, and the top cover 13 includes two electrode terminals 131 with opposite polarities, where one positive electrode terminal 131 is used to electrically connect to the positive current collector tab 111b, and the other negative electrode terminal 131 is used to electrically connect to the negative current collector tab 112b.

[0231] The wound positive current collector tabs 111b are aligned and stacked, having a large connection area, so as to facilitate the direct electrical connection between the positive current collector tabs 111b and the electrode terminals 131 without connecting the positive current collector tabs 111b and the electrode terminals 131 through a transition piece. Similarly, the wound negative current collector tabs 112b are aligned and stacked, having a large connection area, so as to facilitate the direct electrical connection between the negative current collector tabs 112b and the electrode terminals 131 without connecting the negative current collector tabs 112b and the electrode terminals 131 through a transition piece.

[0232] In a conventional battery, a transition piece is required to connect the electrode terminal and the tab, but this will reduce the utilization rate of the electrode assembly and lower the battery energy density. When the above structure is adopted in the battery cell provided in the present application, canceling the setting of the transition piece can effectively solve this problem, reduce the battery internal resistance, and further take into account improving the battery energy density and fast charging performance.

[0233] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0234] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0235] In some embodiments, as Figures 6 - 9 shown, the battery cell 10 further includes a housing 14, and the current collector 11 is disposed inside the housing 14.

[0236] In some embodiments, as Figures 6 - 9As shown, the housing 14 is square, and the thickness T of the housing is 30 mm to 55 mm, the width W is 150 mm to 250 mm, and the height H is 90 mm to 120 mm.

[0237] In some embodiments, the thickness T of the housing is 30 mm to 55 mm, such as 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, etc., or other unlisted values within the range of 30 mm to 55 mm.

[0238] In some embodiments, the width W of the housing is 150 mm to 250 mm, such as 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, etc., or other unlisted values within the range of 150 mm to 250 mm.

[0239] In some embodiments, the height H of the housing is 90 mm to 120 mm, such as 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, etc., or other unlisted values within the range of 90 mm to 120 mm.

[0240] In some embodiments, the battery cell is configured to have a charging time of 10 min to 17 min from 10% SOC to 80% SOC at room temperature, such as 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, etc., or other unlisted values within the range of 10 min to 17 min.

[0241] The battery cell provided by the present application has excellent fast charging performance.

[0242] In some embodiments, the present application does not particularly limit the shape of the battery cell, and it can be cylindrical, square or any other shape. For example, Figure 10 is a battery cell 5 with a square structure as an example. Optionally, the battery cell is a lithium-ion battery or a sodium-ion battery.

[0243] In some embodiments, with reference to Figure 11, the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0244] In some embodiments, a battery device is provided. The battery device can be a battery module, a battery pack, an energy storage battery, etc. The above battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0245] Figure 12 is a battery module 4 as an example. Refer to Figure 12 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0246] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0247] In some embodiments, the above battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0248] Figure 13 and Figure 14 is a battery pack 1 as an example. Refer to Figure 13 and Figure 14 , in the battery pack 1, it may include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0249] [Power-consuming device] In addition, the present application also provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs provided by the present application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0250] As the electrical device, the battery cell, battery module, or battery pack can be selected according to its usage requirements.

[0251] Figure 15 Take an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery cell for this electrical device, a battery pack or a battery module can be used.

[0252] In some embodiments, the electrical device includes a vehicle, and the length direction of the electrode assembly is placed along the traveling direction of the vehicle.

[0253] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be used as the power source.

[0254] Examples Hereinafter, examples of the present application will be described. The examples described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those techniques or conditions not specified in the examples, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0255] Example 1 1) Negative electrode sheet Mix artificial graphite as the negative electrode active material, acetylene black as the conductive agent, styrene-butadiene rubber as the binder, and sodium carboxymethyl cellulose as the thickening agent in a mass ratio of 96:1:2:1. Then add deionized water as the solvent and stir to form a negative electrode slurry. Coat the negative electrode slurry evenly on the negative electrode current collector copper foil, and after drying and cold pressing, obtain a negative electrode sheet; wherein, the thickness of the negative electrode current collector copper foil is 4.5 μm, and the single-sided areal density of the negative electrode sheet is 0.155 g / 1540.25 mm 2 , the size of the negative electrode film layer in the first direction is 92 mm; the volume particle size Dv50 of the artificial graphite is 11 μm, and the specific surface area is 5.5 m 2 / g.

[0256] 2) Positive electrode sheet Mix the positive active material lithium iron phosphate (LFP), binder polyvinylidene fluoride, and conductive agent acetylene black in a ratio of 97:2:1. Then add the solvent N-methylpyrrolidone (NMP) and stir to form a positive electrode paste. Coat the positive electrode paste evenly on the positive current collector aluminum foil, and after drying and cold pressing, obtain the positive electrode sheet. Among them, the thickness of the positive current collector aluminum foil is 13 μm, and the single-sided areal density of the positive electrode sheet is 0.341 g / 1540.25 mm 2 , the size of the positive electrode film layer in the first direction is 88.5 mm; the positive active material includes first lithium-containing phosphate particles with a longest diameter of 0.3 μm - 1 μm and second lithium-containing phosphate particles with a longest diameter of 3 μm - 5 μm. In the longitudinal section of the positive electrode sheet, select any area containing at least 100 olivine-structured lithium-containing phosphates. In this area, the number of first lithium-containing phosphate particles is greater than the number of second lithium-containing phosphate particles.

[0257] 3) Electrolyte Mix dimethyl carbonate (DMC), ethyl acetate (EA), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) evenly in a mass ratio of 10:50:35:5 to obtain an electrolyte solvent. It includes lithium hexafluorophosphate (LiPF 6 ) and lithium bis(fluorosulfonyl)imide (LiFSI) as lithium salts, and stir well until they are completely dissolved. It includes additives vinylene carbonate (VC) with a mass percentage of 0.7% and fluoroethylene carbonate (FEC) with a mass percentage of 0.3% based on the total mass of the electrolyte. Based on the total mass of the electrolyte, the mass fraction of lithium hexafluorophosphate (LiPF 6 ) is 8.9%; the mass fraction of lithium bis(fluorosulfonyl)imide LiFSI is 4.6%, and the lithium ion conductivity of the electrolyte is 14.5 mS / cm.

[0258] 4) Separator Use a commercially available polyethylene microporous film with a thickness of 7 μm and an average pore diameter of 80 nm as the separator.

[0259] 5) Battery cell The positive electrode plate and the negative electrode plate are cut for tab ears. The distance between the center lines of two adjacent tab ears on the positive electrode plate is 316 mm, and the distance between the center lines of two adjacent tab ears on the negative electrode plate is 314 mm. The positive electrode plate, the separator, and the negative electrode plate are stacked and wound in sequence to obtain a wound electrode assembly, such that each layer of the positive electrode plate and the negative electrode plate in the electrode assembly has at least one tab ear. The electrode assembly is placed into a square aluminum outer package with a thickness of 50 mm, a width of 208 mm, and a height of 103 mm, and after drying, electrolyte is injected. Through processes such as encapsulation, standing, formation, aging, secondary encapsulation, and capacity measurement, a battery cell is obtained, and the tab ear of the battery cell is connected to the cover plate.

[0260] Examples 2 to 5 The battery cells of Examples 2 to 5 are basically similar to those of Example 1, except that the particle size Dv50 of graphite is adjusted, as shown in Tables 1 to 4 specifically.

[0261] Example 6 The battery cell of Example 6 is basically similar to that of Example 1, except that the proportion of large and small particles of LFP in the positive electrode active material is changed, such that in the longitudinal section of the positive electrode plate, any region containing at least 100 lithium-containing phosphates with an olivine structure is selected, and in the any region, the number of the first lithium-containing phosphate particles (the longest diameter is 0.3 μm - 1 μm) is less than the number of the second lithium-containing phosphate particles (the longest diameter is 3 μm - 5 μm), as shown in Tables 1 to 4 specifically.

[0262] Examples 7 to 10 The battery cells of Examples 7 to 10 are basically similar to those of Example 1, except that the types or contents of the organic solvent and the lithium salt in the electrolyte are changed, as shown in Tables 1 to 4 specifically.

[0263] Example 11 The battery cell of Example 11 is basically similar to that of Example 1, except that the negative electrode active material uses double-layer coating, and the method is as follows: artificial graphite with a particle size Dv50 of 13 μm is used as the lower layer, and artificial graphite with a particle size Dv50 of 10 μm is used as the upper layer, and they are uniformly coated on the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode plate is obtained. As shown in Tables 1 to 4 specifically.

[0264] Examples 12 to 13 The battery cells of Examples 12 to 13 are basically similar to those of Example 1, except that the ratio of the single-sided film layer thickness to the current collector thickness of the positive and negative electrodes is changed, as shown in Tables 1 to 4 specifically.

[0265] Comparative Examples 1 to 2 Comparative Examples 1 to 2 are basically similar to Example 1, except that the particle size Dv50 and the specific surface area of graphite are adjusted, as shown in Tables 1 to 4 specifically.

[0266] Comparative Example 3 Comparative Example 3 is basically similar to Example 1, except that the proportion of large and small particles of LFP in the positive electrode active material is changed. In the longitudinal section of the positive electrode sheet, any region containing at least 100 lithium-containing phosphates with an olivine structure is selected. In the any region, there are second lithium-containing phosphate particles with a longest diameter of 3 μm - 5 μm, and there are no first lithium-containing phosphate particles with a longest diameter of 0.3 μm - 1 μm. See Tables 1 - 4 for details.

[0267] Comparative Example 4 Comparative Example 4 is basically similar to Example 1, except that the proportion of large and small particles of LFP in the positive electrode active material is changed. In the longitudinal section of the positive electrode sheet, any region containing at least 100 lithium-containing phosphates with an olivine structure is selected. In the any region, there are first lithium-containing phosphate particles with a longest diameter of 0.3 μm - 1 μm, and there are no second lithium-containing phosphate particles with a longest diameter of 3 μm - 5 μm. See Tables 1 - 4 for details.

[0268] I. Performance Tests 1. DC Internal Resistance The DC internal resistance DCR test of the battery cell can refer to the method in GB / T31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV". For example, at room temperature, the battery cell is charged to 3.65 V at a constant current of 0.33C, left standing for 1 min, then charged to 3.65 V at a constant current of 0.1C, left standing for 30 min, discharged to 2.0 V at a constant current of 0.33C, and the discharge capacity A0 at this time is recorded, with the unit Ah. Then, it is charged at a constant current of 0.33C for 0.5A0Ah to adjust the SOC to 50%. After the battery cell is placed at 25°C and left standing for 2 h, it is discharged at a constant current of 3C for 10 s, and ∆U discharge and ∆I discharge are recorded. The discharge DCR data of the lithium-ion battery is calculated through the following formula: R discharge = ∆U discharge / ∆I discharge, where ∆U discharge represents the voltage change within the first 10 s of discharge, and ∆I discharge represents the current value within the first 10 s of discharge.

[0269] 2. Charging Time at 10% - 80% SOC Charging time test: ① Voltage calibration: 1) Prepare a laminated three-electrode battery with the positive electrode plate, negative electrode plate, separator, and electrolyte in the example or comparative example, and let it stand at 25°C for 30 min; 2) Charge the battery monomer to the charging cut-off voltage of 3.65 V at 0.33C at 25°C, and then continue to perform constant voltage charging at this charging cut-off voltage until the current is 0.05C, and the charging is terminated (where C represents the rated capacity of the battery monomer); 3) Let it stand at 25°C for 1 h; 4) Discharge the battery monomer to the discharge cut-off voltage of 2.5 V at 0.33C at 25°C, and record the total discharge capacity C0 discharged by the battery monomer; 5) Let it stand at 25°C for 1 h. ② Normal temperature charging test: 1) Prepare a laminated three-electrode battery with the positive electrode plate, negative electrode plate, separator, and electrolyte in the example or comparative example, and let it stand for 30 min; 2) Discharge at 0.33C0 DC to the discharge cut-off voltage of 2.5 V, corresponding to 0% SOC at this time; 3) Let it stand for 5 min; 4) Charge at 5C0 constant current until the negative electrode potential is 0 V, and read the capacity C1 at this time, corresponding to C1 / C0 SOC at this time; 5) Let it stand for 5 min; 6) Charge at 4.5C0 constant current until the negative electrode potential is 0 V, and read the capacity C2 at this time, corresponding to C2 / C0 SOC at this time; 7) Let it stand for 5 min; 8) Charge at 4C0 constant current until the negative electrode potential is 0 V, and read the capacity C3 at this time, corresponding to C3 / C0 SOC at this time; 9) Let it stand for 5 min; 10) Charge at 3C0 constant current until the negative electrode potential is 0 V, and read the capacity C4 at this time, corresponding to C4 / C0 SOC at this time; 11) Let it stand for 5 min; 12) Charge at 2C0 constant current until the negative electrode potential is 0 V, and read the capacity C5 at this time, corresponding to C5 / C0 SOC at this time; 13) Let it stand for 5 min; 14) Charge at 1C0 constant current until the negative electrode potential is 0 V, and read the capacity C6 at this time, corresponding to C6 / C0 SOC at this time; 15) Let it stand for 5 min; 16) Charge at 0.8C0 constant current until the negative electrode potential is 0 V, and read the capacity C7 at this time, corresponding to C7 / C0 SOC at this time; 17) Let it stand for 5 min; 18) Charge at 0.5C0 constant current until the negative electrode potential is 0 V, and read the capacity C8 at this time, corresponding to C8 / C0 SOC at this time; 19) Let it stand for 5 min; 20) Charge at 0.33C0 constant current until the negative electrode potential is 0 V, and read the capacity C9 (i.e., C0) at this time, corresponding to 100% SOC. The required charging time is obtained by summing up the total charging time during the charging process from 10% SOC to 80% SOC.

[0270] 3. Volume energy density At 25 °C, the battery cell is discharged at a constant current of 0.33C to 2.5V, left standing for 5 minutes, charged at a constant current of 0.33C to the upper cut-off voltage of 3.65V, then charged at a constant voltage until the current is 0.05C, and left standing for 5 minutes; discharged at a constant current of 0.33C to the cut-off voltage of 2.5V, and record the discharge capacity at this time to obtain the discharge energy E0. The volume energy density (Wh / L) = discharge energy E0 / monomer volume (L).

[0271] 4. Cycling performance At 25 °C, charge at a charging rate of 0.5C to 3.65V, then charge at a constant voltage of 3.65V until 0.05C, left standing for 10 minutes, then discharge at a discharge rate of 1C to 2.5V, left standing for 10 minutes. The above one charge and discharge cycle is one cycle, and the test is stopped until the battery capacity decays to 80% of the nominal capacity, denoted as the cycle number @80% SOH.

[0272] II. Analysis of test results of each example and comparative example Prepare the battery cells of each example and comparative example respectively according to the above method, and measure various performance parameters. The results are shown in Table 5 below.

[0273] Table 1 Preparation parameters of the negative electrode sheet

[0274] Table 2 Preparation parameters of the positive electrode sheet

[0275] Table 3 Preparation parameters of the electrolyte

[0276] Table 4 Preparation parameters of the electrolyte

[0277] Table 5 Battery performance parameters

[0278] In the battery cells of Examples 1 to 13, a lithium-containing phosphate containing an olivine structure was used as the positive electrode active material in the positive electrode film layer, and graphite with an average particle size Dv50 of 8 μm to 15 μm was used as the negative electrode active material in the negative electrode film layer; and as Figure 4 shown, in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate contains a first lithium-containing phosphate particle with a longest diameter of 0.05 μm to 0.3 μm and a second lithium-containing phosphate particle with a longest diameter of 1 μm to 3 μm; therefore, the battery cells prepared in Examples 1 to 13 all have excellent fast charging performance, energy density, cycling performance, and low DC internal resistance.

[0279] The average particle size Dv50 of the graphite in the negative electrode film layers of Comparative Examples 1 to 2 exceeded the range of 8 μm to 15 μm, where: the Dv50 of the graphite in Comparative Example 1 was too large, while the Dv50 of the graphite in Comparative Example 2 was too small.

[0280] From the comparison between Comparative Examples 1 to 2 and Examples 1 to 13, it can be seen that: when the average particle size Dv50 of the graphite is greater than 15 μm, the fast charging performance and DC internal resistance of the battery cell cannot be effectively improved; while when the average particle size Dv50 of the graphite is less than 8 μm, the cycle performance of the battery cell cannot be effectively improved, and the energy density also decreases; therefore, when the average particle size Dv50 of the graphite in the negative electrode film layer is within the range of 8 μm to 15 μm, the cycle performance, fast charging performance, DC internal resistance and energy density of the battery can be improved simultaneously. When it exceeds this range, the comprehensive performance of the battery is poor.

[0281] In the positive electrode film layer of Comparative Example 3, the lithium-containing phosphate contains second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm, and does not contain first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm.

[0282] From the comparison between Comparative Example 3 and Examples 1 to 13, it can be seen that: when the lithium-containing phosphate in the positive electrode film layer does not use the method of particle size grading, and only uses particles with a larger particle size (longest diameter of 1 μm to 3 μm), the improvement effect on the fast charging performance and DC internal resistance of the battery is limited, and the energy density will deteriorate.

[0283] In the positive electrode film layer of Comparative Example 4, the lithium-containing phosphate contains first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm, and does not contain second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm.

[0284] From the comparison between Comparative Example 4 and Examples 1 to 13, it can be seen that: when the lithium-containing phosphate in the positive electrode film layer does not use the method of particle size grading, and only uses particles with a smaller particle size (longest diameter of 0.05 μm to 0.3 μm), the compaction density of the electrode sheet is relatively low, so the energy density will deteriorate. Therefore, when the lithium-containing phosphate in the positive electrode film layer uses the method of particle size grading with both smaller particle size (longest diameter of 0.05 μm to 0.3 μm) and larger particle size (longest diameter of 1 μm to 3 μm), the energy density, cycle performance, fast charging performance and DC internal resistance of the battery can be improved simultaneously. When it exceeds this range, the comprehensive performance of the battery is poor.

[0285] In Examples 1 to 5, the average particle size Dv50 of graphite in the negative electrode film layer ranges from 8 μm to 15 μm. The prepared battery cells can take into account excellent energy density, fast charging performance, cycling performance, and low DC internal resistance. In addition, the results also show that when the Dv50 of graphite gradually increases within the range of 8 μm to 15 μm, the cycling performance of the battery is improved to a certain extent, but the fast charging performance decreases to a certain extent and the DC internal resistance increases to a certain extent; when the Dv50 of graphite gradually decreases within the range of 8 μm to 15 μm, the fast charging performance of the battery is improved to a certain extent, the DC internal resistance decreases to a certain extent, but the cycling performance decreases to a certain extent. Therefore, only when the Dv50 of graphite in the negative electrode film layer is within the range of 8 μm to 15 μm can the fast charging performance, cycling performance, and DC internal resistance of the battery be improved while taking into account; when the Dv50 of graphite is within the range of 9.5 μm to 11.5 μm, the comprehensive performance of the battery is better. When the Dv50 of graphite is too low, the energy density of the battery decreases.

[0286] In Examples 1 and 6, the lithium-containing phosphate in the positive electrode film layer includes first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm. The prepared battery cells can take into account excellent energy density, fast charging performance, cycling performance, and low DC internal resistance. In addition, from the comparison between Example 1 and Example 6, it can be seen that when the number of first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm is greater than the number of second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm, the DC internal resistance and fast charging performance of the battery can be further improved while taking into account, and the comprehensive performance of the battery is better.

[0287] In Examples 1 and 7 to 10, the electrolyte uses the following formula. The prepared battery cells can take into account excellent energy density, fast charging performance, cycling performance, and low DC internal resistance: The organic solvent uses a linear carboxylic acid ester (such as ethyl acetate) with a mass fraction of 40% to 75%, a linear carbonate (such as DMC, EMC) with a mass fraction of 10% to 40%, and a cyclic carbonate (such as ethylene carbonate), where the mass fraction of dimethyl carbonate is 5% to 15%, and the mass ratio of the linear carboxylic acid ester (such as ethyl acetate) to dimethyl carbonate is 2.0 to 7.0; the lithium salt uses LiPF 6 and LiFSI, and the mass ratio of LiPF 6 and LiFSI is 1.2:1 to 2:1.

[0288] At the same time, comparing Examples 1, 7, and 8, it can be seen that as the proportion of the linear carboxylic acid ester (such as ethyl acetate) and LiFSI added to the electrolyte gradually increases, the fast charging performance and DC internal resistance of the battery are further improved; as the proportion of the linear carbonate (such as DMC) and LiPF 6The proportion gradually increases, further improving the cycling performance of the battery.

[0289] At the same time, by comparing Examples 1, 9, and 10: when there is only linear carboxylic acid ester (such as ethyl acetate) in the organic solvent of the electrolyte and no carbonate, and there is only LiFSI in the lithium salt and no LiPF 6 When there is only linear carbonate (such as DMC) in the organic solvent of the electrolyte and no linear carboxylic acid ester, and there is only LiPF 6 in the lithium salt and no LiFSI, the fast charging performance and DC internal resistance of the battery are further improved, but the cycling performance of the battery is poor; when there is only linear carbonate (such as DMC) in the organic solvent of the electrolyte and no linear carboxylic acid ester, and there is only LiPF 6 in the lithium salt and no LiFSI, the cycling performance of the battery is further improved, but the improvement of the fast charging performance and DC internal resistance is limited. Therefore, when linear carbonate and linear carboxylic acid ester with the above mass ratio are used as organic solvents in the electrolyte at the same time, and LiPF 6 and LiFSI are used as lithium salts at the same time, through the mutual combination of various solvents and lithium salts, the fast charging performance, DC internal resistance and cycling performance of the battery can be further improved simultaneously, making the comprehensive performance of the battery better.

[0290] In Examples 1 and 11, the negative electrode film layer contains at least one layer of graphite as the negative electrode active material, and its average particle size Dv50 is in the range of 8 μm to 15 μm. The battery monomer prepared therefrom can take into account excellent energy density, fast charging performance, cycling performance, and low DC internal resistance. In addition, from the comparison between Example 1 and Example 11, it can be seen that when the negative electrode film layer includes two layers of artificial graphite with different particle sizes as the negative electrode active material layers (the first negative electrode active material layer is disposed on the surface of the negative electrode current collector, the second negative electrode active material layer is disposed on the side of the first negative electrode active material layer away from the negative electrode current collector, and the Dv50 of the first negative electrode active material layer is greater than that of the second negative electrode active material layer), the fast charging performance and DC internal resistance of the battery can be further improved simultaneously, making the comprehensive performance of the battery better.

[0291] In Examples 1, 12 to 13, the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 5 to 12, and the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 12 to 20. The battery monomer prepared therefrom can take into account excellent energy density, fast charging performance, cycling performance, and low DC internal resistance. In addition, the results also show that when the ratio of the single-sided thickness of the positive and negative electrode film layers to the thickness of the positive and negative electrode current collectors gradually increases within the above range, the energy density of the battery can be further improved; when the ratio of the single-sided thickness of the positive and negative electrode film layers to the thickness of the positive and negative electrode current collectors gradually decreases within the above range, the fast charging performance, DC internal resistance and cycling performance of the battery can be further improved.

[0292] In Examples 1 to 13, the specific surface area of graphite in the positive electrode film layer is 3 m 2 / g to 8 m2 / g, the tap density of the positive electrode sheet is 2.3 g / cm 3 to 2.6 g / cm 3 , the tap density of the negative electrode sheet is 1.3 g / cm 3 to 1.6 g / cm 3 , and the battery monomer prepared therefrom can take into account excellent energy density, fast charging performance, cycle performance, and low DC internal resistance.

[0293] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the scope of the technical solution of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that: It includes a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate with an olivine structure; In a cross section of the positive electrode film layer along the thickness direction, the olivine-structured lithium-containing phosphate comprises first lithium-containing phosphate particles having a longest diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles having a longest diameter of 1 μm to 3 μm; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the average particle size Dv50 of the negative electrode active material is 8μm to 15μm, and the negative electrode active material includes graphite.

2. The battery cell according to claim 1, characterized in that: The average particle size Dv50 of the negative electrode active material is 9.5 μm to 11.5 μm.

3. The battery cell according to claim 1, characterized in that: The specific surface area of ​​the negative electrode active material is 3 m 2 / g to 8m 2 / g.

4. The battery cell according to claim 1, characterized in that: The specific surface area of ​​the negative electrode active material is 4 m 2 / g to 6m 2 / g.

5. The battery cell according to claim 1, characterized in that: In a cross section of the positive electrode film layer along the thickness direction, the number of the first lithium-containing phosphate particles is greater than the number of the second lithium-containing phosphate particles.

6. The battery cell according to claim 1, characterized in that: The general composition formula of the lithium-containing phosphate with olivine structure is as shown in Formula I: Li x A y Me a M b P 1-c X c Y z Formula I Among them, 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤x+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, and Mg; Me includes one or more of Mn, Fe, Co, and 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, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

7. The battery cell according to claim 6, characterized in that: M includes one or more of Al, Ti, V, and Mg.

8. The battery cell according to claim 6 or 7, characterized in that: The positive electrode active material satisfies at least one of the following conditions: (1) The positive electrode active material contains Al element, the mass content of which is 0.01-0.05%, based on the total mass of the positive electrode active material; (2) The positive electrode active material contains Ti element, the mass content of which is 0.01-0.03%, based on the total mass of the positive electrode active material; (3) The positive electrode active material contains V element, the mass content of which is 0.1-0.3%, based on the total mass of the positive electrode active material; (4) The positive electrode active material contains Mg element, with a mass content of 0.001-0.01% based on the total mass of the positive electrode active material.

9. The battery cell according to claim 1, characterized in that: The compaction density of the positive electrode sheet is 2.3 g / cm 3 Up to 2.6g / cm 3 .

10. The battery cell according to claim 1, characterized in that: The compaction density of the positive electrode sheet is 2.4 g / cm 3 Up to 2.55g / cm 3 .

11. The battery cell according to claim 1, characterized in that: The surface density of the positive electrode film layer on one side is 0.33g / 1540.25mm 2 Up to 0.4 g / 1540.25 mm 2 .

12. The battery cell according to claim 1, characterized in that: The surface density of the positive electrode film layer on one side is 0.335g / 1540.25mm 2 Up to 0.38 g / 1540.25 mm 2 .

13. The battery cell according to claim 1, characterized in that: The thickness of the positive electrode current collector is 10 μm to 15 μm.

14. The battery cell according to claim 1, characterized in that: The ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 5 to 12.

15. The battery cell according to claim 1, characterized in that: The ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 6 to 10.

16. The battery cell according to claim 1, characterized in that: The compaction density of the negative electrode sheet is 1.3 g / cm 3 Up to 1.6g / cm 3 .

17. The battery cell according to claim 1, characterized in that: The compaction density of the negative electrode sheet is 1.35 g / cm 3 Up to 1.55g / cm 3 .

18. The battery cell according to claim 1, characterized in that: The surface density of the negative electrode film layer on one side is 0.15g / 1540.25mm 2 Up to 0.19 g / 1540.25 mm 2 .

19. The battery cell according to claim 1, characterized in that: The surface density of the negative electrode film layer on one side is 0.15g / 1540.25mm 2 Up to 0.165 g / 1540.25 mm 2 .

20. The battery cell according to claim 1, characterized in that The thickness of the negative electrode current collector is 4 μm to 6 μm.

21. The battery cell according to claim 1, characterized in that: The ratio of the single-side thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 12 to 20.

22. The battery cell according to claim 1, characterized in that: The ratio of the single-side thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 13 to 20.

23. The battery cell according to claim 1, characterized in that: The negative electrode current collector includes a negative electrode current collecting portion, the negative electrode film layer includes a first negative electrode active material layer arranged on the surface of the negative electrode current collecting portion and a second negative electrode active material layer arranged on the side of the first negative electrode active material layer away from the negative electrode current collecting portion, the negative electrode active material in the first negative electrode active material layer includes a first artificial graphite, the negative electrode active material in the second negative electrode active material layer includes a second artificial graphite, and the average particle size Dv50 of the first artificial graphite is greater than the average particle size Dv50 of the second artificial graphite.

24. The battery cell according to claim 23, characterized in that: The average particle size Dv50 of the first artificial graphite is 11 μm to 15 μm.

25. The battery cell according to claim 23, characterized in that: The average particle size Dv50 of the second artificial graphite is 8 μm to 15 μm.

26. The battery cell according to claim 23, characterized in that: The average particle size Dv50 of the second artificial graphite is 9.5 μm to 11.5 μm.

27. The battery cell according to claim 1, characterized in that: The battery cell further includes an electrolyte solution, the electrolyte solution includes an organic solvent, and the organic solvent includes a carboxylate solvent and a carbonate solvent.

28. The battery cell according to claim 27, characterized in that: The organic solvent includes a linear carboxylic acid ester, and the mass proportion of the linear carboxylic acid ester is 40% to 75% based on the total mass of the electrolyte.

29. The battery cell according to claim 28, characterized in that: The linear carboxylic acid ester has a general structural formula of R1-COO-R2, wherein R1 and R2 each independently include one or more of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

30. The battery cell according to claim 29, characterized in that The linear carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

31. The battery cell according to any one of claims 27 to 30, characterized in that: The organic solvent includes a carbonate solvent, and the carbonate solvent includes a linear carbonate and a cyclic carbonate. The mass proportion of the linear carbonate is 10% to 40% based on the total mass of the electrolyte.

32. The battery cell according to claim 31, characterized in that: The cyclic carbonate includes one or more of ethylene carbonate and propylene carbonate, and the linear carbonate includes one or more of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

33. The battery cell according to claim 32, characterized in that: The linear carbonate includes dimethyl carbonate, and based on the total mass of the electrolyte, the mass proportion of the dimethyl carbonate is 5% to 15%.

34. The battery cell according to claim 27, characterized in that: The organic solvent includes dimethyl carbonate and linear carboxylic acid ester, and the mass ratio of the linear carboxylic acid ester to the dimethyl carbonate is 2.0 to 7.

0.

35. The battery cell according to claim 34, characterized in that: The mass ratio of the linear carboxylic acid ester to the dimethyl carbonate is 3.0 to 6.

0.

36. The battery cell according to claim 27, characterized in that: The electrolyte further includes a lithium salt, and the mass proportion of the lithium salt is 13% to 20% based on the total mass of the electrolyte.

37. The battery cell according to claim 36, characterized in that: The lithium salt includes at least two of lithium hexafluorophosphate LiPF6 and fluorine-containing sulfonyl imide salts, and the fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

38. The battery cell according to claim 36, characterized in that The lithium salt includes lithium hexafluorophosphate LiPF6 and lithium bis(fluorosulfonyl)imide LiFSI.

39. The battery cell according to claim 38, characterized in that In the electrolyte, the mass ratio of lithium hexafluorophosphate LiPF6 to lithium bis(fluorosulfonyl)imide LiFSI is 1.2:1 to 2:

1.

40. The battery cell according to claim 27, characterized in that The electrolyte includes carbonate additives, and the carbonate additives include fluoroethylene carbonate FEC and vinylene carbonate VC.

41. The battery cell according to claim 40, characterized in that Based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 0.5% to 7%.

42. The battery cell according to claim 40 or 41, characterized in that: The electrolyte includes vinylene carbonate VC, and the mass proportion of vinylene carbonate VC in the electrolyte is 0.5% to 2% based on the total mass of the electrolyte.

43. The battery cell according to claim 40 or 41, characterized in that: The electrolyte includes fluoroethylene carbonate (FEC), and the mass proportion of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 1% based on the total mass of the electrolyte.

44. The battery cell according to claim 1, characterized in that The positive current collector comprises a positive current collecting portion and at least two positive electrode tabs arranged on the same side of the positive current collecting portion, the positive electrode tab extends from the positive current collecting portion along a first direction, wherein the distance between the center lines of two adjacent positive electrode tabs is 10 mm to 350 mm, and the center line is parallel to the first direction; and / or, the negative current collector comprises a negative current collecting portion and at least two negative electrode tabs arranged on the same side of the negative current collecting portion, the negative electrode tab extends from the negative current collecting portion along the first direction, wherein the distance between the center lines of two adjacent negative electrode tabs is 10 mm to 350 mm, and the center line is parallel to the first direction.

45. The battery cell according to claim 44, characterized in that The distance between the center lines of two adjacent positive electrode tabs is 20 mm to 330 mm; and / or, The distance between the center lines of two adjacent negative electrode ears is 20 mm to 330 mm.

46. ​​The battery cell according to claim 44, characterized in that The battery cell further includes a top cover, wherein the top cover includes a positive electrode terminal and a negative electrode terminal with opposite polarities, wherein the positive electrode terminal and the negative electrode terminal are respectively used to be electrically connected to the positive electrode tab and the negative electrode tab.

47. The battery cell according to any one of claims 44 to 46, characterized in that: The size of the positive electrode film layer along the first direction is W1 mm, and the size of the negative electrode film layer along the first direction is W2 mm, wherein W2>W1, and the difference between W2 and W1 is 3 mm to 5 mm.

48. The battery cell according to claim 1, characterized in that The battery cell further includes a shell, which is square in shape, has a thickness of 30 mm to 55 mm, a width of 150 mm to 250 mm, and a height of 90 mm to 120 mm.

49. The battery cell according to claim 1, characterized in that The battery cell is configured to be charged from 10% SOC to 80% SOC in a charging time of 10 min to 17 min at room temperature.

50. A battery device, characterized in that: Comprising the battery monomer described in any one of claims 1 to 49, the battery device is at least one of a battery module, a battery pack, and an energy storage device.

51. An electrical device, characterized in that: A battery cell comprising any one of claims 1 to 49 or a battery device according to claim 50.

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