Battery cells, battery devices and power-consuming devices

Abstract

The present application provides a battery cell, a battery device, and an electrical device. In the battery cell of the present application, the positive electrode active material comprises an olivine-structured lithium-containing phosphate. 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 with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm. The negative electrode active material has an average particle size (Dv50) of 8 μm to 15 μm, and the negative electrode active material comprises graphite.

Description

[0001] This application claims priority to PCT patent application PCT / CN2024 / 116594, entitled “Battery Cell, Battery Device, and Electrical Device,” filed on September 3, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of battery technology, 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 systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the widespread use of batteries, higher requirements have been placed on their energy density, fast charging performance, cycle performance, service life, and safety performance. 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 have low DC internal resistance, high energy density and good cycle performance.

[0005] In order to achieve the above-mentioned objectives, the first aspect of the present application provides a battery cell, comprising 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 comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising an olivine-structured lithium-containing phosphate; 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 with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm; the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material, the average particle size Dv50 of the negative electrode active material being 8 μm to 15 μm, and the negative electrode active material comprising graphite.

[0006] This application improves the transmission path of lithium ions inside the negative electrode active material during charging by adopting a small-particle negative electrode active material, which is beneficial to improving the fast charging capability of the battery cell. However, when the fast charging capability of the battery cell is improved, the corresponding charging current it can withstand is also increased accordingly. At this time, if the positive electrode active material is not set reasonably, it will lead to the accumulation of internal heat generated in the battery cell during fast charging, the internal temperature of the battery will increase, and it will cause adverse reactions such as electrolyte gas production and increased impedance of the solid electrolyte interface membrane (SEI film) of the negative electrode, thereby increasing the internal resistance of the battery and affecting the cycle performance of the battery cell. This application reasonably selects lithium-containing phosphates of different sizes as positive electrode active materials, and effectively reduces the heat accumulation inside the battery cell by mixing large and small particles, reduces the internal temperature rise of the battery cell, and suppresses 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 in the present application, when the positive electrode active material includes lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm, it can further improve the DC internal resistance of the battery cell, thereby further reducing the heat generation of the battery, so that the battery has excellent safety performance.

[0008] In the battery cell provided in the present application, when the lithium-containing phosphate serving as the positive electrode active material contains first lithium-containing phosphate particles with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm, the compaction density of the electrode can be effectively improved by grading the size of the particles, so that the battery cell also has a higher 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, the fast charging performance and DC internal resistance of the battery can be further improved, while at the same time enabling the battery to have better 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 speed of lithium ions between graphite layers, thereby further improving the fast charging performance of the battery.

[0014] In any embodiment, 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.

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

[0016] In any embodiment, the general formula of the lithium-containing phosphate with olivine structure is as shown in Formula I:

[0017] Li x A y Me a M b P 1-c X c Y z Formula I,

[0018] 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; and Y includes one or more of O and F.

[0019] When the lithium-containing phosphate as the positive electrode active material has the above-mentioned general chemical formula, the energy density of the battery can be further improved.

[0020] In any embodiment, M includes one or more of Al, Ti, V, and Mg.

[0021] In any embodiment, the positive electrode active material satisfies at least one of the following conditions:

[0022] (1) The positive electrode active material contains Al element, the mass content of which is 0.01 to 0.05%, based on the total mass of the positive electrode active material;

[0023] (2) The positive electrode active material contains Ti element, the mass content of which is 0.01 to 0.03%, based on the total mass of the positive electrode active material;

[0024] (3) The positive electrode active material contains V element, the mass content of which is 0.1 to 0.3%, based on the total mass of the positive electrode active material;

[0025] (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.

[0026] When the lithium-containing phosphate used as the positive electrode active material contains elements such as Al, Ti, V, and Mg, its specific capacity can be further increased.

[0027] In any embodiment, the compaction density of the positive electrode sheet is 2.3 g / cm 3 Up to 2.6g / cm 3 .

[0028] In any embodiment, the compacted density of the positive electrode sheet is 2.4 g / cm 3 Up to 2.55g / cm 3 .

[0029] When the compaction density of the positive electrode sheet is within the above range, the energy density of the battery can be further improved while ensuring the dynamic performance.

[0030] In any embodiment, 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 .

[0031] In any embodiment, the surface density of the positive electrode film layer on one side is 0.335 g / 1540.25 mm 2 Up to 0.38g / 1540.25mm 2 .

[0032] In the battery cell provided in the present application, when the coating surface 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.

[0033] In any embodiment, the thickness of the positive electrode current collector is 10 μm to 15 μm.

[0034] In any embodiment, the ratio of the thickness of the positive electrode film layer on a single side to the thickness of the positive electrode current collector is 5 to 12.

[0035] In any embodiment, the ratio of the thickness of the positive electrode film layer on a single side to the thickness of the positive electrode current collector is 6 to 10.

[0036] In the battery cell provided in the present application, when the ratio of the thickness of the positive electrode film layer on a single side to the thickness of the positive electrode current collector is within the above range, it is possible to further improve both the energy density and the fast charging performance of the battery.

[0037] In any embodiment, the compaction density of the negative electrode sheet is 1.3 g / cm 3 Up to 1.6g / cm 3 .

[0038] In any embodiment, the compaction density of the negative electrode sheet is 1.35 g / cm 3 Up to 1.55g / cm 3 .

[0039] When the compaction density of the negative electrode sheet is within the above range, the energy density of the battery can be further improved while ensuring the dynamic performance.

[0040] In any embodiment, the surface density of the negative electrode film layer on one side is 0.15 g / 1540.25 mm 2 Up to 0.19 g / 1540.25 mm 2 .

[0041] In any embodiment, the surface density of the negative electrode film layer on one side is 0.15 g / 1540.25 mm 2 Up to 0.165g / 1540.25mm 2 .

[0042] In the battery cell provided in the present application, when the coating surface 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 electrochemical performance can be avoided, thereby further improving the fast charging performance of the battery.

[0043] In any embodiment, the thickness of the negative electrode current collector is 4 μm to 6 μm.

[0044] In any embodiment, the ratio of the thickness of the negative electrode film layer on a single side to the thickness of the negative electrode current collector is 12 to 20.

[0045] In any embodiment, the ratio of the thickness of the negative electrode film layer on a single side to the thickness of the negative electrode current collector is 13 to 20.

[0046] In the battery cell provided in the present application, when the ratio of the thickness of the negative electrode film layer on one side to the thickness of the negative electrode current collector is within the above range, both the energy density and the fast charging performance of the battery can be further improved.

[0047] 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 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.

[0048] In any embodiment, the average particle size Dv50 of the first artificial graphite is 11 μm to 15 μm.

[0049] In any embodiment, the average particle size Dv50 of the second artificial graphite is 8 μm to 15 μm.

[0050] In any embodiment, the average particle size Dv50 of the second artificial graphite is 9.5 μm to 11.5 μm.

[0051] In the battery cell provided in the present application, when the above-mentioned double-layer coating scheme is adopted in the negative electrode film layer, the dynamic performance of the battery can be further improved.

[0052] In any embodiment, the battery cell further includes an electrolyte, the electrolyte includes an organic solvent, and the organic solvent includes a carboxylate solvent and a carbonate solvent.

[0053] In the battery cell provided in the present application, when the above-mentioned type of organic solvent is used in the electrolyte, the dynamic performance of the battery can be further improved.

[0054] In any embodiment, 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.

[0055] In any embodiment, 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 haloalkyl group.

[0056] 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.

[0057] When linear carboxylates of the above type and mass proportion are used as organic solvents in the electrolyte, the linear carboxylates can effectively improve the conductivity of the electrolyte due to their low viscosity, thereby further improving the fast charging performance of the battery.

[0058] In any embodiment, 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.

[0059] 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 ethyl methyl carbonate.

[0060] In any embodiment, the linear carbonate includes dimethyl carbonate, and the mass proportion of the dimethyl carbonate is 5% to 15% based on the total mass of the electrolyte.

[0061] When carbonates of the above types and mass proportions are used as organic solvents in the electrolyte, the side reactions and gas production levels of the battery during the cycle process can be improved, thereby enabling the battery to have better cycle performance.

[0062] In any embodiment, 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.

[0063] In any embodiment, 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 3.0 to 6.0.

[0064] When dimethyl carbonate and linear carboxylic acid ester are simultaneously used as organic solvents in the electrolyte in the above-mentioned mass ratio, the fast charging performance and cycle performance of the battery can be further improved by combining the two solvents.

[0065] In any embodiment, 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.

[0066] In any embodiment, 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).

[0067] Lithium hexafluorophosphate is not easy to produce gas during the cycle process, which can further improve the cycle performance of the battery; and the fluorinated sulfonyl imide salt has a strong dissociation ability, which can further improve the fast charging performance of the battery.

[0068] In any embodiment, the lithium salt includes lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI).

[0069] In any embodiment, in the electrolyte, the mass ratio of lithium hexafluorophosphate LiPF6 to lithium bis(fluorosulfonyl)imide LiFSI is 1.2:1 to 2:1.

[0070] When lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide within the above-mentioned mass ratio range are simultaneously used in the electrolyte, the fast charging performance and cycle performance of the battery can be further improved.

[0071] In any embodiment, the electrolyte includes a carbonate additive, and the carbonate additive includes fluoroethylene carbonate FEC and vinylene carbonate VC.

[0072] In any embodiment, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 0.5% to 7%.

[0073] In the battery cell provided in the present application, carbonate additives such as fluoroethylene carbonate and vinylene carbonate are also added to the electrolyte with a mass proportion within the above range, which can form an SEI film on the surface of the negative electrode, thereby reducing the side reactions between the electrode and the electrolyte, thereby further enabling the battery to have better cycle performance.

[0074] In any embodiment, 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.

[0075] When vinylene carbonate within the above-mentioned mass proportion range is added to the electrolyte as an additive, the SEI film formed is relatively stable, which is beneficial to further improve the cycle performance of the battery.

[0076] In any embodiment, 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.

[0077] When fluoroethylene carbonate within the above-mentioned mass proportion range is added to the electrolyte as an additive, the SEI film formed has low impedance, which can further improve the fast charging performance of the battery.

[0078] In any embodiment, the positive electrode current collector includes a positive electrode current collecting portion and at least two positive electrode tabs arranged on the same side of the positive electrode current collecting portion, the positive electrode tabs extending from the positive electrode 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 lines are parallel to the first direction; and / or,

[0079] The negative electrode current collector includes a negative electrode current collecting portion and at least two negative electrode tabs arranged on the same side of the negative electrode current collecting portion, the negative electrode tabs extending from the negative electrode current collecting portion along a first direction, wherein the distance between the center lines of two adjacent negative electrode tabs is 10 mm to 350 mm, and the center lines are parallel to the first direction.

[0080] In any embodiment, the distance between the center lines of two adjacent positive electrode tabs is 20 mm to 330 mm; and / or,

[0081] The distance between the center lines of two adjacent negative electrode tabs is 20 mm to 330 mm.

[0082] In the battery cell provided in the present application, when the positive and negative electrode current collectors include at least two tabs having the above-mentioned structural features, they 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.

[0083] In any embodiment, the battery cell further includes a top cover, the top cover including a positive electrode terminal and a negative electrode terminal with opposite polarities, the positive electrode terminal and the negative electrode terminal being respectively configured to be electrically connected to the positive electrode tab and the negative electrode tab.

[0084] Conventional batteries require adapters to connect the electrode terminals to the tabs, but this reduces the utilization of the electrode assembly and the battery's energy density. The battery cells provided in this application, when using the above-mentioned structure, eliminate the adapter, which effectively solves this problem, reduces the battery's internal resistance, and further improves both the battery's energy density and fast-charging performance.

[0085] In any embodiment, 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.

[0086] During battery cycling, lithium ions that fail to embed into the negative electrode in a timely manner may form lithium dendrites on the negative electrode surface, deteriorating the battery's cycling performance. In the battery cells provided herein, when the negative electrode film layer size W2 and the positive electrode film layer size W1 have the aforementioned relationship, the formation of lithium dendrites on the negative electrode surface can be reduced, thereby simultaneously ensuring the battery has good cycling performance.

[0087] In any embodiment, the battery cell further includes a shell, the shell is square, and the shell 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.

[0088] When a shell within the above-mentioned size range is used, it is possible to increase the energy density while reducing the internal resistance of the battery, thereby improving both the energy density and fast charging performance of the battery.

[0089] In any embodiment, the battery cell is configured to be charged from 10% SOC to 80% SOC in a charging time of 10 minutes to 17 minutes at room temperature.

[0090] The battery cell provided in this application has excellent fast charging performance.

[0091] The second aspect of the present application further provides a battery device, comprising the battery cell of the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0092] The third aspect of the present application further provides an electrical device, comprising the battery cell of the first aspect or the battery device of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 This is one of the schematic diagrams of the electrode film layer size in one embodiment of the present application;

[0094] Figure 2 This is a second schematic diagram of the dimensions of the electrode film layer according to one embodiment of the present application;

[0095] Figure 3 This is the third schematic diagram of the electrode film layer size in one embodiment of the present application;

[0096] Figure 4 This is an electron microscope observation result of a longitudinal section of a positive electrode sheet according to one embodiment of the present application;

[0097] Figure 5 is a schematic diagram of a pole piece according to one embodiment of the present application;

[0098] Figure 6 is an exploded view of a battery cell according to one embodiment of the present application;

[0099] Figure 7 is one of the schematic diagrams of a battery cell according to one embodiment of the present application;

[0100] Figure 8 This is a second schematic diagram of a battery cell according to an embodiment of the present application;

[0101] Figure 9 This is a third schematic diagram of a battery cell according to an embodiment of the present application;

[0102] Figure 10 is a schematic diagram of a battery cell according to one embodiment of the present application;

[0103] Figure 11 yes Figure 10 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0104] Figure 12 is a schematic diagram of a battery module according to one embodiment of the present application;

[0105] Figure 13 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0106] Figure 14 yes Figure 13 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0107] Figure 15 FIG2 is a schematic diagram of an electrical device using a battery cell according to an embodiment of the present application as a power source.

[0108] Description of reference numerals:

[0109] 1 Battery pack; 2 Upper case; 3 Lower case; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly; 10 Battery cell; 11 Current collector; 11a Current collector; 111a Positive current collector; 112a Negative current collector; 11b Tab; 111b Positive tab; 112b Negative tab; F1 First direction; W1 Dimension of the positive electrode film layer along the first direction; W2 Dimension of the negative electrode film layer along the first direction; L Centerline; 13 Top cover; 131 Electrode terminal; 14 Housing. DETAILED DESCRIPTION

[0110] Below, the embodiments of the battery cells and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary lengthiness in the following description and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0111] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0112] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0113] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0114] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0115] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0116] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0117] In recent years, with the increasing demand for batteries as energy sources, higher requirements have been placed on the comprehensive performance of batteries. Compared with the ternary battery of nickel cobalt manganese oxide, the lithium iron phosphate battery has become the mainstream of the secondary battery market due to its low cost, good safety and good cycle performance. However, the rate performance of the lithium iron phosphate battery has become a bottleneck for its wider application, especially under the premise of high demand for energy density, the improvement of rate performance is more difficult. This application aims to obtain a battery with fast charging and good energy density by rationally matching the particle size of the positive and negative electrodes of the lithium iron phosphate battery.

[0118] Based on this, the present application provides a battery cell, comprising 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 comprising 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 comprising a positive electrode active material, the positive electrode active material comprising an olivine-structured lithium-containing phosphate; 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 with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm; the negative electrode sheet comprising 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 comprising a negative electrode active material, the average particle size Dv50 of the negative electrode active material being 8 μm to 15 μm, and the negative electrode active material comprising graphite.

[0119] As used herein, "average particle size Dv50" refers to the particle size at which the cumulative volume percentage reaches 50% of the particle size distribution, starting from the smallest particle size. This measurement method can be found in accordance with GB / T19077-2016 / ISO13320:2009, using a Malvern MasterSizer 2000 laser particle size analyzer.

[0120] In some embodiments, since the first lithium-containing phosphate and the second lithium-containing phosphate have been fully mixed and uniformly coated on the current collector to form a positive electrode film layer when preparing the slurry, any cross-section along the thickness direction of the electrode can represent the particle size and distribution of the lithium-containing phosphate in the entire electrode; when selecting a cross-section, a relatively flat cross-section in the middle of the electrode is preferred so that the distribution of the lithium-containing phosphate therein can be observed more clearly.

[0121] In some embodiments, "the longest diameter" refers to: cutting a positive electrode sheet including lithium phosphate particles along the thickness direction of the sheet to expose a longitudinal section of the positive electrode film layer; and determining the longest diameter of the lithium phosphate particles by performing a scanning electron microscope (SEM) test on the longitudinal section of the positive electrode film layer.

[0122] Specifically, the maximum value of the distance between any two points on the peripheral edge line of the lithium-containing phosphate particle is the "longest diameter" of the particle. Figure 4 The longitudinal section of the electrode along the thickness direction is shown, which shows the longest diameter of a single particle that meets the first lithium-containing phosphate particle (the longest diameter is 0.05μm to 0.3μm), and also shows the shortest diameter of a single particle that meets the second lithium-containing phosphate particle (the longest diameter is 1μm to 3μm).

[0123] It should be noted that the first lithium-containing phosphate particle material with a smaller size and a longest diameter of 0.05 μm to 0.3 μm is one of the positive electrode active materials of the battery cell of the present application, and its particle size range of 0.05 μm to 0.3 μm is a characteristic parameter of the material itself.

[0124] The second lithium-containing phosphate particle material with a larger size and a longest diameter of 1 μm to 3 μm is one of the positive electrode active materials of the battery cell of the present application, and its particle size range of 1 μm to 3 μm is a characteristic parameter of the material itself.

[0125] Those skilled in the art can mix the lithium-containing phosphate particle materials in the above two size ranges according to actual needs.

[0126] This application improves the transmission path of lithium ions inside the negative electrode active material during charging by using small-particle negative electrode active materials, which is beneficial to improving the fast charging capability of the battery cell. However, when the fast charging capability of the battery cell is improved, the corresponding charging current it can withstand is also increased accordingly. At this time, if the positive electrode active material is not set reasonably, it will lead to the accumulation of internal heat generated in the battery cell during fast charging, the internal temperature of the battery will increase, and adverse reactions such as electrolyte gas production and increased impedance of the solid electrolyte interface membrane of the negative electrode will be triggered, thereby increasing the internal resistance of the battery and affecting the cycle performance of the battery cell. This application reasonably selects lithium-containing phosphates of different sizes as positive electrode active materials, and effectively reduces the heat accumulation inside the battery cell by mixing large and small particles, reduces the internal temperature rise of the battery cell, and inhibits the growth of the DC internal resistance of the battery cell; it also improves the energy density of the battery cell.

[0127] [Positive electrode]

[0128] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0129] In some embodiments, the positive electrode film layer includes a positive electrode active material.

[0130] In some embodiments, the positive electrode active material includes an olivine-structured lithium-containing phosphate.

[0131] In some embodiments, the general formula of the lithium-containing phosphate with an olivine structure is as shown in Formula I:

[0132] Li x A y Me a M b P 1-c X c Y z Formula I,

[0133] 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; and Y includes one or more of O and F.

[0134] When used in this article, "the general formula of the lithium-containing phosphate with an olivine structure is shown in Formula I" is not limited to the substances represented by the molecular general formula, but also includes other substances formed after further appropriate modification on the basis of the molecular general formula, which is not limited here. The use of "general formula" is only for the convenience of description and is not intended to limit this application. It can be understood that the materials obtained by appropriate modification on the basis of the listed positive active materials are also within the scope of positive active materials. The aforementioned appropriate modification refers to the acceptable modification method for the positive active material, and a non-limiting example is coating modification.

[0135] When the lithium-containing phosphate used as the positive electrode active material has the above-mentioned general chemical formula, the structural stability of the positive electrode active material can be further improved, thereby enhancing the cycle performance of the battery cell.

[0136] In some embodiments, M includes one or more of Al, Ti, V, and Mg.

[0137] In some embodiments, the positive electrode active material contains Al element, and its mass content is 0.001%~0.05%, which can be optionally 0.01%~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%~0.05%.

[0138] In some embodiments, the positive electrode active material contains Ti element, and its mass content is 0.001%~0.03%, which can be optionally 0.01~0.03%, 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%~0.03%.

[0139] In some embodiments, the positive electrode active material contains V element, and its mass content is 0.001%~0.3%, and can be optionally 0.1~0.3%, 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%~0.3%.

[0140] In some embodiments, 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, which can be selected as 0.001%, 0.002%, 0.005%, 0.01%, or other unlisted values ​​within the range of 0.001%~0.01%.

[0141] When the lithium-containing phosphate used as the positive electrode active material contains elements such as Al, Ti, V, and Mg, it can further enhance the structural stability of the material and improve the cycle performance.

[0142] In some embodiments, 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 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.

[0143] In some embodiments, 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, 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.

[0144] In some embodiments, in a cross section of the positive electrode film layer along the thickness direction, the olivine-structured lithium-containing phosphate comprises second lithium-containing phosphate particles having a longest diameter of 1 μm to 3 μm, for example, 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.

[0145] In the battery cell provided in the present application, when the positive electrode active material includes lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm, it can further improve the DC internal resistance of the battery cell, thereby further reducing the heat generation of the battery, so that the battery has excellent safety performance.

[0146] In the battery cell provided in the present application, when the lithium-containing phosphate serving as the positive electrode active material contains first lithium-containing phosphate particles with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm, the compaction density of the electrode can be effectively improved by grading the size of the particles, so that the battery cell also has a higher energy density.

[0147] In some embodiments, 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.

[0148] In the lithium-containing phosphate used as the positive electrode active material, when the number of first lithium-containing phosphate particles with a maximum diameter of 0.05 μm to 0.3 μm is greater than the number of second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm, the battery's DC internal resistance and fast charging performance can be further improved.

[0149] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0150] 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), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0151] In some embodiments, the surface density of the positive electrode film layer on a single side is 0.33g / 1540.25mm 2 Up to 0.4 g / 1540.25 mm 2 , for example 0.33 g / 1540.25 mm 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 0.33g / 1540.25mm 2 Up to 0.4 g / 1540.25 mm 2 Other values ​​not listed within the range.

[0152] In some embodiments, the surface density of the positive electrode film layer on a single side is 0.335 g / 1540.25 mm 2 Up to 0.38g / 1540.25mm 2 .

[0153] When used in this article, the "area density" of the positive electrode film layer or the negative electrode film layer has a meaning well known in the art and can be tested using methods known in the art. For example, take a negative electrode sheet that has been coated on one side and cold pressed (if it is a negative electrode sheet coated on both sides, the negative electrode film layer on one side can be wiped off first), punch it into small discs with an area of ​​S1, weigh it, and record it as M1. Then wipe off the negative electrode film layer of the weighed negative electrode sheet, weigh the weight of the negative electrode current collector, and record it as M0. The surface density of the negative electrode film layer = (the weight of the negative electrode sheet M1-the weight of the negative electrode current collector M0) / S1. In order to ensure the accuracy of the test results, multiple groups (for example, 10 groups) of test samples can be tested, and the average value can be calculated as the test result.

[0154] In the battery cell provided in the present application, when the coating surface 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.

[0155] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Aluminum foil may be used as an example of a metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material may include at least one of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0156] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm, for example, 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.

[0157] 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, for example, 5, 6, 7, 8, 9, 10, 11, 12, etc., or other unlisted values ​​within the range of 5 to 12.

[0158] In some embodiments, the ratio of the thickness of the positive electrode film layer on a single side to the thickness of the positive electrode current collector is 6 to 10.

[0159] In the battery cell provided in 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 an appropriate range, so as to avoid the loss of energy density due to excessive thickness, and avoid the problem of cracking of the electrode due to poor current capacity and low tensile strength caused by excessive thinness, thereby further taking into account the improvement of the energy density and fast charging performance of the battery.

[0160] In some embodiments, combined Figure 5As shown, the current collector 11 includes a current collecting portion 11a and at least two tabs 11b arranged on the same side of the current collecting portion 11a, and the tabs 11b extend from the current collecting portion 11a along a first direction F1, wherein 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, 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 unlisted values ​​within the range of 10 mm to 350 mm.

[0161] In some embodiments, the distance between the center lines L of two adjacent tabs 11b is 20 mm to 330 mm, and the center lines L are 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 unlisted values ​​within the range of 20 mm to 330 mm.

[0162] In some embodiments, combined Figure 5 and Figure 6 As shown, the current collector 11 may be a positive electrode current collector, and the tab 11b may be a positive electrode tab 111b.

[0163] In some embodiments, combined Figure 5 and Figure 6 As shown, the current collector 11 may be a negative electrode current collector, and the tab 11b may be a negative electrode tab 112b.

[0164] In some embodiments, the positive electrode current collector includes a positive electrode current collecting portion and at least two positive electrode tabs arranged on the same side of the positive electrode current collecting portion, and the positive electrode tabs extend from the positive electrode 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, 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 unlisted values ​​in the range of 10 mm to 350 mm.

[0165] In some embodiments, the distance between the center lines of two adjacent positive 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 unlisted values ​​within the range of 20 mm to 330 mm.

[0166] In some embodiments, combined Figure 5 As shown, the center line L is the symmetry axis passing through the midpoint of the tab 11b along the length direction of the current collector 11, and the center line 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.

[0167] In some embodiments, combined Figure 5 As shown, the distance between the center lines L of two adjacent tabs 11b includes S1 or S2, wherein S1 and S2 can be equal (in this case, the adjacent tabs are equally spaced), or S1 and S2 can be unequal (in this case, the adjacent tabs are unequally spaced).

[0168] In the battery cell provided in the present application, when the positive and negative electrode current collectors include at least two tabs with the above-mentioned structural features, they can further improve the current flow capacity and 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.

[0169] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0170] In some embodiments, the compacted density of the positive electrode sheet is 2.3 g / cm 3 Up to 2.6g / cm 3 , for example 2.30g / cm 3 , 2.35g / cm 3 , 2.40g / cm 3 , 2.45g / cm 3 , 2.50g / cm 3 , 2.55g / cm 3 , 2.60g / cm 3 etc., or 2.3g / cm 3 Up to 2.6g / cm 3 Other values ​​not listed within the range.

[0171] In some embodiments, the compacted density of the positive electrode sheet is 2.4 g / cm 3 Up to 2.55g / cm 3 .

[0172] When the compaction density of the positive electrode sheet is within the above range, the energy density of the battery can be further improved while ensuring the dynamic performance.

[0173] In some embodiments, the compaction density of the positive electrode sheet corresponds to the compaction density of the positive electrode film layer corresponding to the battery cell in the 0% SOC state, and the battery cell in the 0% SOC state refers to: the battery cell is discharged to 2.0V at 1 / 3C and then discharged to 2.0V at 0.05C.

[0174] [Negative electrode]

[0175] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0176] In some embodiments, the negative electrode film layer includes a negative electrode active material.

[0177] In some embodiments, the negative electrode active material has an average particle size Dv50 of 8 μm to 15 μm, such as 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or other values ​​not listed in the range of 8 μm to 15 μm. In some embodiments, the negative electrode active material includes graphite.

[0178] 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-mentioned range, it has a larger specific surface area, the migration channels of lithium ions between the graphite layers are increased, and the migration paths are shortened, thereby accelerating the insertion and extraction speed of lithium ions between the graphite layers, so that the battery cell has better fast charging performance; at the same time, when the negative electrode active material (such as graphite) has a particle size within the above-mentioned range, it can also improve the DC internal resistance of the battery cell, thereby reducing the heat generation of the battery, and making the battery have better safety performance.

[0179] In some embodiments, the average particle size Dv50 of the negative electrode active material is 9.5 μm to 11.5 μm, for example, 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.

[0180] When the negative electrode active material (such as graphite) has a particle size within the above range, the fast charging performance and DC internal resistance of the battery can be further improved, while at the same time enabling the battery to have better cycle performance.

[0181] In some embodiments, the specific surface area of ​​the negative electrode active material is 3 m 2 / g to 8m 2 / g, for example 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 3 m 2 / g to 8m 2 / Other values ​​not listed in the g range.

[0182] In some embodiments, the specific surface area of ​​the negative electrode active material is 4 m 2 / g to 6m 2 / g, for example 4 m 2 / g, 4.5 m 2 / g, 5 m 2 / g, 5.5 m 2 / g, 6 m 2 / g, etc., or 4m 2 / g to 6m 2 / Other values ​​not listed in the g range.

[0183] As used herein, "specific surface area" refers to the total surface area per unit mass of a material. This specific surface area can be determined according to GB / T 19587-2017 using nitrogen adsorption specific surface area analysis and calculation using the Brunauer-Emmett-Teller (BET) method. Nitrogen adsorption specific surface area analysis can be performed using a Micromeritics Tri-Star 3020 specific surface area pore size analyzer.

[0184] 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 speed of lithium ions between graphite layers, thereby further improving the fast charging performance of the battery.

[0185] 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 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, the average particle size Dv50 of the first artificial graphite is greater than the average particle size Dv50 of the second artificial graphite, and the artificial graphite in the upper negative electrode film layer (second negative electrode active material layer) has a small particle size because the upper graphite is in direct contact with the electrolyte and can respond to the insertion of lithium ions more quickly than the graphite in the lower layer. Therefore, the upper graphite has a small particle size, which helps lithium ions to be inserted into the graphite more quickly, thereby improving the electromagnetic fast charging capability; at the same time, the use of artificial graphite particles with larger particle size in the lower layer can reduce the probability of the graphite material being crushed, make it more pressure-resistant, and improve the compaction density of the electrode sheet.

[0186] In some embodiments, the average particle size Dv50 of the first artificial graphite is 11 μm to 15 μm, for example, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., or other unlisted values ​​within the range of 11 μm to 15 μm.

[0187] In some embodiments, the average particle size Dv50 of the second artificial graphite is 8 μm to 15 μm, for example, 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.

[0188] In some embodiments, the average particle size Dv50 of the second artificial graphite is 9.5 μm to 11.5 μm, for example, 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.

[0189] In the battery cell provided in the present application, when the above-mentioned double-layer coating scheme is adopted in the negative electrode film layer, the dynamic performance of the battery can be further improved.

[0190] In some embodiments, the negative electrode film layer may further 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).

[0191] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0192] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0193] In some embodiments, the surface density of the negative electrode film layer on a single side is 0.15 g / 1540.25 mm 2 Up to 0.19 g / 1540.25 mm 2 , for example 0.15 g / 1540.25 mm 2 、0.16 g / 1540.25mm 2 、0.17 g / 1540.25mm 2 、0.18 g / 1540.25mm 2 、0.19 g / 1540.25mm 2 etc., or 0.15 g / 1540.25mm 2 Up to 0.19 g / 1540.25 mm 2 Other values ​​not listed within the range.

[0194] In some embodiments, the surface density of the negative electrode film layer on a single side is 0.15 g / 1540.25 mm 2 Up to 0.165g / 1540.25mm 2 .

[0195] In the battery cell provided in the present application, when the coating surface 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 electrochemical performance can be avoided, thereby further improving the fast charging performance of the battery.

[0196] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0197] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc., or other unlisted values ​​within the range of 4 μm to 6 μm.

[0198] 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, for example, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc., or other unlisted values ​​within the range of 12 to 20.

[0199] In some embodiments, the ratio of the thickness of the negative electrode film layer on a single side to the thickness of the negative electrode current collector is 13 to 20.

[0200] In some embodiments, the thickness of the negative electrode film layer on a single side corresponds to the thickness of the negative electrode film layer on a single side of a battery cell at 0% SOC, where 0% SOC refers to a battery cell discharged at 1 / 3C to 2.0V and then discharged at 0.05C to 2.0V. In the battery cell provided herein, when the ratio of the thickness of the negative electrode film layer on a single side to the thickness of the negative electrode current collector is within the above range, both the energy density and fast charging performance of the battery can be further improved.

[0201] In some embodiments, the negative electrode current collector includes a negative electrode current collecting portion and at least two negative electrode tabs arranged on the same side of the negative electrode current collecting portion, and the negative electrode tabs extend from the negative electrode current collecting portion along a 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, 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 unlisted values ​​in the range of 10 mm to 350 mm.

[0202] In some embodiments, the distance between the center lines 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 unlisted values ​​within the range of 20 mm to 330 mm.

[0203] In the battery cell provided in the present application, when the positive and negative electrode current collectors include at least two tabs with the above-mentioned structural features, they can further improve the current flow capacity and 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.

[0204] In some embodiments, the size of the positive electrode film layer along the first direction is W1mm, and the size of the negative electrode film layer along the first direction is W2mm, wherein W2>W1, and the difference between W2 and W1 is 3mm to 5mm, for example, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm, 4.2mm, 4.4mm, 4.6mm, 4.8mm, 5mm, etc., or other unlisted values ​​within the range of 3mm to 5mm.

[0205] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0206] In some embodiments, the battery cell is a wound battery, Figure 3 As shown, after the electrode sheet is unwound from its wound state, the positive electrode current collector includes a positive electrode current collecting portion 111a and at least two positive electrode tabs 111b disposed on the same side of the positive electrode current collecting portion 111a, and the positive electrode tabs 111b extend from the positive electrode current collecting portion 111a along a first direction F1. The negative electrode current collector includes a negative electrode current collecting portion 112a and at least two negative electrode tabs 112b disposed on the same side of the negative electrode current collecting portion 112a, and the negative electrode tabs 112b extend from the negative electrode current collecting portion 112a along the first direction F1. The dimension W2 of the negative electrode film layer along the first direction is greater than the dimension W1 of the positive electrode film layer along the first direction, and the difference is 3 mm to 5 mm.

[0207] In some embodiments, the battery cell is a laminated battery. Figure 1 and Figure 2 As shown, each electrode sheet is stacked to form an electrode assembly. Each positive electrode sheet includes a positive current collector, which includes a positive current collector portion 111a and a positive electrode tab 111b disposed on the positive current collector portion 111a, extending from the positive current collector portion 111a along a first direction F1. Each negative electrode sheet includes a negative current collector, which includes a negative current collector portion 112a and a negative electrode tab 112b disposed on the negative current collector portion 112a, extending from the negative current collector portion 112a along the first direction F1. The dimension W2 of the negative electrode film layer along the first direction is greater than the dimension W1 of the positive electrode film layer along the first direction, and the difference is 3 mm to 5 mm.

[0208] During battery cycling, lithium ions that fail to embed into the negative electrode in a timely manner may form lithium dendrites on the negative electrode surface, deteriorating the battery's cycling performance. In the battery cells provided herein, when the negative electrode film layer size W2 and the positive electrode film layer size W1 have the aforementioned relationship, the formation of lithium dendrites on the negative electrode surface can be reduced, thereby simultaneously ensuring the battery has good cycling performance.

[0209] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0210] In some embodiments, the compacted density of the negative electrode sheet is 1.3 g / cm 3 Up to 1.6g / cm 3 , for example 1.3 g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 etc., or 1.3g / cm 3 Up to 1.6g / cm 3 Other values ​​not listed within the range.

[0211] In some embodiments, the compacted density of the negative electrode sheet is 1.35 g / cm 3 Up to 1.55g / cm 3 , for example 1.35g / cm 3 , 1.40g / cm 3 , 1.45g / cm 3 , 1.50g / cm 3 , 1.55g / cm 3 etc., or 1.35g / cm 3 Up to 1.55g / cm 3 Other values ​​not listed within the range.

[0212] In some embodiments, the compaction density of the negative electrode plate corresponds to the compaction density of the negative electrode film layer corresponding to the battery cell in the 0% SOC state, and the battery cell in the 0% SOC state refers to: the battery cell is discharged to 2.0V at 1 / 3C and then discharged to 2.0V at 0.05C.

[0213] As used in this article, the "compacted density" of the electrode is: compacted density = surface density / (electrode thickness - current collector thickness), and its determination method can refer to GB / T24533-2009.

[0214] When the compaction density of the negative electrode sheet is within the above range, the energy density of the battery can be further improved while ensuring the dynamic performance.

[0215] [Electrolytes]

[0216] The electrolyte conducts ions between the positive electrode and the negative electrode. For example, the electrolyte can be in liquid, solid or gel form.

[0217] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and an organic solvent.

[0218] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using 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-phase nuclear magnetic resonance, etc. For example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography with reference to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0219] The test sample in the embodiments of the present application can be a freshly prepared electrolyte as a sample, or a free electrolyte obtained from a battery after the battery is fully discharged (discharged to the lower limit cut-off voltage so that the battery's state of charge is approximately 0% SOC) as a sample.

[0220] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed using ion chromatography analysis methods in accordance with standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods." In the embodiments of the present application, a freshly prepared electrolyte can be used as a sample, or a battery can be fully discharged (discharged to the lower cutoff voltage so that the battery's state of charge is approximately 0%), and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis methods.

[0221] In some embodiments, the organic solvent includes a carboxylate solvent and a carbonate solvent.

[0222] In the battery cell provided in the present application, when the above-mentioned type of organic solvent is used in the electrolyte, the dynamic performance of the battery can be further improved.

[0223] In some embodiments, the organic solvent includes a linear carboxylate, and the mass proportion of the linear carboxylate based on the total mass of the electrolyte is 40% to 75%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, etc., or other unlisted values ​​within the range of 40% to 75%.

[0224] In some embodiments, the linear carboxylate 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 haloalkyl group.

[0225] 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.

[0226] When linear carboxylates of the above type and mass proportion are used as organic solvents in the electrolyte, the linear carboxylates can effectively improve the conductivity of the electrolyte due to their low viscosity, thereby further improving the fast charging performance of the battery.

[0227] 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 proportion of the linear carbonate is 10% to 40%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc., or other unlisted values ​​within the range of 10% to 40%.

[0228] 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.

[0229] In some embodiments, the linear carbonate includes dimethyl carbonate, and the mass proportion of the dimethyl carbonate is 5% to 15% based on the total mass of the electrolyte, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., or other unlisted values ​​within the range of 5% to 15%.

[0230] When carbonates of the above types and mass proportions are used as organic solvents in the electrolyte, the side reactions and gas production levels of the battery during the cycle process can be improved, thereby enabling the battery to have better cycle performance.

[0231] In some embodiments, the organic solvent comprises 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, for example, 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.

[0232] In some embodiments, 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 3.0 to 6.0.

[0233] When dimethyl carbonate and linear carboxylic acid ester are simultaneously used as organic solvents in the electrolyte in the above-mentioned mass ratio, the fast charging performance and cycle performance of the battery can be further improved by combining the two solvents.

[0234] 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0235] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the lithium salt is 13% to 20%, for example, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., or other unlisted values ​​within the range of 13% to 20%.

[0236] In some embodiments, the lithium salt includes at least two of lithium hexafluorophosphate (LiPF6) and a fluorine-containing sulfonyl imide salt, and the fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0237] Fluorinated sulfonyl imide salts have strong dissociation ability and can be used in combination with lithium hexafluorophosphate to further improve the fast charging performance of the battery. However, excessive content of LiTFSI will reduce the safety performance of the battery, especially making the thermal runaway of the battery more severe.

[0238] In some embodiments, the lithium salt includes lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI).

[0239] In some embodiments, in the electrolyte, the mass ratio of lithium hexafluorophosphate LiPF6 to lithium bis(fluorosulfonyl)imide LiFSI is 1.2:1 to 2:1, for example, 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.

[0240] When lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide within the above-mentioned mass ratio range are simultaneously used in the electrolyte, the fast charging performance and cycle performance of the battery can be further improved.

[0241] In some embodiments, the electrolyte further includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0242] In some embodiments, the electrolyte includes a carbonate additive, and the carbonate additive includes fluoroethylene carbonate FEC and vinylene carbonate VC.

[0243] In some embodiments, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 0.5% to 7%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 6.5%, 7%, etc., or other unlisted values ​​within the range of 0.5% to 7%.

[0244] In the battery cell provided in the present application, carbonate additives such as fluoroethylene carbonate and vinylene carbonate are also added to the electrolyte with a mass proportion within the above range, which can form an SEI film on the surface of the negative electrode, thereby reducing the side reactions between the electrode and the electrolyte, thereby further enabling the battery to have better cycle performance.

[0245] In some embodiments, the electrolyte includes vinylene carbonate VC, and based on the total mass of the electrolyte, the mass proportion of vinylene carbonate VC in the electrolyte is 0.5% to 2%, for example, 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%.

[0246] When vinylene carbonate within the above-mentioned mass proportion range is added to the electrolyte as an additive, the SEI film formed is relatively stable, which is beneficial to further improve the cycle performance of the battery.

[0247] In some embodiments, 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, for example, 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%.

[0248] When fluoroethylene carbonate within the above-mentioned mass proportion range is added to the electrolyte as an additive, the SEI film formed has low impedance, which can further improve the fast charging performance of the battery.

[0249] In some embodiments, the type and quality of the additives and solvents in the electrolyte can be obtained by detecting the electrolyte by 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 phase nuclear magnetic resonance, etc. Exemplarily, acetonitrile is used to dilute the electrolyte to 3-10 times to obtain an electrolyte dilution to be tested, and a GC-MS 3100 organic component gas chromatograph is used to place the above electrolyte dilution in the instrument for full scan qualitative analysis, with an injection port temperature of 250°C and a scanning range of 35μm~270μm. After the test is completed, a total ion current chromatogram of each organic matter is obtained, and the type of organic matter corresponding to the peak position of the chromatogram is compared, and the corresponding content percentage of each organic matter is calculated according to the peak area.

[0250] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0251] In the embodiments of the present application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art, such as gas chromatography, liquid chromatography, liquid nuclear magnetic resonance, etc.

[0252] In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse.

[0253] [Isolation film]

[0254] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0255] 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.

[0256] [Battery Cell]

[0257] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0258] In some embodiments, the positive electrode current collector, the separator, the negative electrode current collector, and the separator are stacked in sequence and wound together; after winding, the positive electrode tabs 111b of the positive electrode current collector are aligned and stacked, and the negative electrode tabs 112b of the negative electrode current collector are aligned and stacked, as shown in FIG. Figure 6 shown.

[0259] In some embodiments, the battery cell further includes a top cover, wherein the top cover includes electrode terminals with opposite polarities for electrically connecting to the positive electrode tab or the negative electrode tab.

[0260] In some embodiments, combined Figure 6 As shown, the battery cell 10 further includes a top cover 13 , which includes two electrode terminals 131 with opposite polarities, wherein one positive electrode terminal 131 is used to electrically connect to the positive electrode tab 111 b , and the other negative electrode terminal 131 is used to electrically connect to the negative electrode tab 112 b .

[0261] After winding, the positive electrode tabs 111b are aligned and stacked, with a large connection area, so that the positive electrode tabs 111b can be directly electrically connected to the electrode terminal 131 without the need for an adapter to connect the positive electrode tabs 111b to the electrode terminal 131. Similarly, after winding, the negative electrode tabs 112b are aligned and stacked, with a large connection area, so that the negative electrode tabs 112b can be directly electrically connected to the electrode terminal 131 without the need for an adapter to connect the negative electrode tabs 112b to the electrode terminal 131.

[0262] Conventional batteries require adapters to connect the electrode terminals to the tabs, but this reduces the utilization of the electrode assembly and the battery's energy density. The battery cells provided in this application, when using the above-mentioned structure, eliminate the adapter, which effectively solves this problem, reduces the battery's internal resistance, and further improves both the battery's energy density and fast-charging performance.

[0263] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0264] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0265] In some embodiments, as Figure 6-Figure 9 As shown, the battery cell 10 further includes a housing 14 , and the current collector 11 is disposed in the housing 14 .

[0266] In some embodiments, as Figure 6-Figure 9 As shown, the shell 14 is square, with a thickness T of 30 mm to 55 mm, a width W of 150 mm to 250 mm, and a height H of 90 mm to 120 mm.

[0267] In some embodiments, the thickness T of the shell is 30 mm to 55 mm, for example, 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.

[0268] In some embodiments, the width W of the shell is 150 mm to 250 mm, for example, 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.

[0269] In some embodiments, the height H of the shell is 90 mm to 120 mm, for example, 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.

[0270] In some embodiments, the battery cell is configured to charge from 10% SOC to 80% SOC in a charging time of 10 min to 17 min at room temperature, for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, etc., or other unlisted values ​​in the range of 10 min to 17 min.

[0271] The battery cell provided in this application has excellent fast charging performance.

[0272] In some embodiments, the present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, Figure 10 1 is a square-structured battery cell 5 as an example. Optionally, the battery cell is a lithium-ion battery or a sodium-ion battery.

[0273] In some embodiments, reference Figure 11, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination 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 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0274] In some embodiments, a battery device is provided. The battery device may be a battery module, a battery pack, an energy storage battery, etc. The above-mentioned battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0275] Figure 12 4 is an example of a battery module. Figure 12 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0276] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0277] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0278] Figure 13 and Figure 14 The battery pack 1 is used as an example. Figure 13 and Figure 14 The battery pack 1 may include a battery box and multiple battery modules 4 disposed 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 cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0279] [Electrical devices]

[0280] 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 in the present application. The battery cells, battery modules, or battery packs can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, 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.

[0281] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0282] Figure 15 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells in this device, a battery pack or battery module can be used.

[0283] In some embodiments, the power-consuming device includes a vehicle, and the length direction of the electrode assembly is placed along the traveling direction of the vehicle.

[0284] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0285] Example

[0286] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0287] Example 1

[0288] 1) Negative electrode

[0289] The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the binder, styrene-butadiene rubber, and the thickener, sodium carboxymethyl cellulose, were mixed in a mass ratio of 96:1:2:1. Deionized water was then added and stirred to form a negative electrode slurry. The negative electrode slurry was evenly coated on the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet. The thickness of the negative electrode current collector copper foil was 4.5 μm, and the single-sided surface density of the negative electrode sheet was 0.155 g / 1540.25 mm 2The size of the negative electrode film along 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.

[0290] 2) Positive electrode

[0291] The positive electrode active material lithium iron phosphate (LFP), the binder polyvinylidene fluoride, and the conductive agent acetylene black were mixed in a ratio of 97:2:1, and then the solvent N-methylpyrrolidone (NMP) was added and stirred to form a positive electrode slurry. The positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain the positive electrode sheet. The thickness of the positive electrode current collector aluminum foil is 13 μm, and the single-side density of the positive electrode sheet is 0.341g / 1540.25mm 2 The dimension of the positive electrode film layer along the first direction is 88.5 mm; the positive electrode active material comprises 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 cross-section of the positive electrode sheet, any region containing at least 100 lithium-containing phosphates with an olivine structure is selected, and in the region, the number of the first lithium-containing phosphate particles is greater than the number of the second lithium-containing phosphate particles.

[0292] 3) Electrolyte

[0293] The electrolyte solvent was prepared by uniformly mixing dimethyl carbonate (DMC), ethyl acetate (EA), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) in a mass ratio of 10:50:35:5. The electrolyte contained lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI) as lithium salts, which were stirred thoroughly until completely dissolved. The electrolyte was also prepared by adding 0.7% by mass of vinylene carbonate (VC) and 0.3% by mass of fluoroethylene carbonate (FEC), respectively, relative to the total mass of the electrolyte. Based on the total mass of the electrolyte, lithium hexafluorophosphate (LiPF6) accounted for 8.9% by mass, and lithium bis(fluorosulfonyl)imide (LiFSI) accounted for 4.6% by mass. The lithium ion conductivity of the electrolyte was 14.5 mS / cm.

[0294] 4) Isolation film

[0295] A commercially available polyethylene microporous film with a thickness of 7 μm and an average pore size of 80 nm was used as the separator.

[0296] 5) Battery cells

[0297] The positive and negative electrode sheets are cut to their tabs. The centerline distance between adjacent tabs on the positive electrode sheet is 316mm, and the centerline distance between adjacent tabs on the negative electrode sheet is 314mm. The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to form a wound electrode assembly, so that each layer of the positive and negative electrode sheets in the electrode assembly has at least one tab. The electrode assembly is placed in a square aluminum shell with a thickness of 50mm, a width of 208mm, and a height of 103mm for outer packaging. After drying, the electrolyte is injected. After packaging, standing, formation, aging, secondary packaging, and capacity testing, a battery cell is obtained, and the tabs of the battery cell are connected to the cover plate.

[0298] Examples 2 to 5

[0299] The battery cells of Examples 2 to 5 are basically similar to those of Example 1, except that the particle size Dv50 of the graphite is adjusted, as shown in Tables 1 to 4.

[0300] Example 6

[0301] The battery cell of Example 6 is basically similar to that of Example 1, except that the ratio of large and small particles of LFP in the positive electrode active material is changed so that in the longitudinal cross-section of the positive electrode plate, any region containing at least 100 olivine-structured lithium phosphate particles is selected, and in the arbitrary region, the number of first lithium phosphate particles (with a longest diameter of 0.3 μm to 1 μm) is less than the number of second lithium phosphate particles (with a longest diameter of 3 μm to 5 μm), as shown in Tables 1 to 4.

[0302] Examples 7-10

[0303] 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 lithium salt in the electrolyte are changed, as shown in Tables 1 to 4.

[0304] Example 11

[0305] The battery cell of Example 11 is essentially similar to that of Example 1, except that the negative electrode active material is coated using a double layer coating method: artificial graphite with a particle size Dv50 of 13 μm as the lower layer and artificial graphite with a particle size Dv50 of 10 μm as the upper layer are evenly coated on the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet is obtained. See Tables 1-4 for details.

[0306] Examples 12-13

[0307] The battery cells of Examples 12 to 13 are basically similar to those of Example 1, except that the thickness ratio of the single-sided film layer of the positive and negative electrodes to the current collector is changed, as shown in Tables 1 to 4.

[0308] Comparative Examples 1-2

[0309] Comparative Examples 1-2 are basically similar to Example 1, except that the particle size Dv50 and specific surface area of ​​the graphite are adjusted, as shown in Tables 1-4.

[0310] Comparative Example 3

[0311] Comparative Example 3 is substantially similar to Example 1, except that the ratio of large and small LFP particles in the positive electrode active material is varied, such that, in a longitudinal cross-section of the positive electrode sheet, a random region containing at least 100 olivine-structured lithium-containing phosphate particles is selected, and within the random region, second lithium-containing phosphate particles having a maximum diameter of 3 μm to 5 μm are present, and first lithium-containing phosphate particles having a maximum diameter of 0.3 μm to 1 μm are absent. See Tables 1-4 for details.

[0312] Comparative Example 4

[0313] Comparative Example 4 is substantially similar to Example 1, except that the ratio of large and small LFP particles in the positive electrode active material is varied, such that, in a longitudinal cross-section of the positive electrode sheet, a random region containing at least 100 olivine-structured lithium-containing phosphate particles is selected, and within the random region, first lithium-containing phosphate particles having a maximum diameter of 0.3 μm to 1 μm are present, and second lithium-containing phosphate particles having a maximum diameter of 3 μm to 5 μm are absent. See Tables 1-4 for details.

[0314] 1. Performance Testing

[0315] 1. DC internal resistance

[0316] The DC internal resistance (DCR) test for a battery cell can refer to the method in GB / T31467, "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEVs." For example, at room temperature, charge the battery cell to 3.65V at a constant current of 0.33C, let it rest for 1 minute, then charge it to 3.65V at a constant current of 0.1C, let it rest for 30 minutes, and discharge it to 2.0V at a constant current of 0.33C. Record the discharge capacity (A0) in Ah at this point. Then, charge it at a constant current of 0.5A0Ah at 0.33C, adjusting the SOC to 50%. After the battery cell is left at 25°C for 2 hours, discharge it at a constant current of 3C for 10 seconds. Record ∆U discharge and ∆I discharge. The discharge DCR data for the lithium-ion battery can be calculated using the following formula: R discharge = ∆U discharge / ∆I discharge, where ∆U discharge represents the voltage change within the first 10 seconds of discharge, and ∆I discharge represents the current value within the first 10 seconds of discharge.

[0317] 2. Charging time from 10% to 80% SOC

[0318] Charging time test: ① Voltage calibration: 1) Prepare a laminated three-electrode battery with the positive electrode sheet, negative electrode sheet, separator, and electrolyte in the embodiment or comparative example, and let it stand at 25°C for 30 minutes; 2) Charge the battery cell at 0.33C at 25°C to a charge cut-off voltage of 3.65V, and continue to charge at the charge cut-off voltage until the current reaches 0.05C and the charge is cut off (where C represents the rated capacity of the battery cell); 3) Let it stand at 25°C for 1 hour; 4) Discharge the battery cell at 0.33C at 25°C to a discharge cut-off voltage of 2.5V, and record the total discharge capacity C0 released by the battery cell; 5) Let it stand at 25°C for 1 hour. ② Room temperature charging test: 1) Prepare a laminated three-electrode battery with the positive electrode sheet, negative electrode sheet, separator, and electrolyte in the embodiment or comparative example, and let it stand for 30 minutes; 2) 0.33C0 DC discharge to the discharge cut-off voltage of 2.5V, which corresponds to 0% SOC; 3) Let it stand for 5 minutes; 4) 5C0 constant current charge to the negative electrode potential of 0V, read the capacity C1 at this time, which corresponds to C1 / C0SOC; 5) Let it stand for 5 minutes; 6) 4.5C0 constant current charge to the negative electrode potential of 0V, read the capacity C2 at this time, which corresponds to C2 / C0SOC; 7) Let it stand for 5 minutes; 8) 4C0 constant current charge to the negative electrode potential of 0V, read the capacity C3 at this time, which corresponds to C3 / C0SOC; 9) Let it stand for 5 minutes; 10) 3C0 constant current charge to the negative electrode potential of 0V, read the capacity C4 at this time, which corresponds to C4 / C0SOC; 11) Let it stand for 5 minutes; 12) 2C0 constant current charge 13) Let stand for 5 minutes; 14) Charge with a constant current of 1C0 until the negative electrode potential is 0V and read the capacity C6, which corresponds to C6 / C0SOC; 15) Let stand for 5 minutes; 16) Charge with a constant current of 0.8C0 until the negative electrode potential is 0V and read the capacity C7, which corresponds to C7 / C0SOC; 17) Let stand for 5 minutes; 18) Charge with a constant current of 0.5C0 until the negative electrode potential is 0V and read the capacity C8, which corresponds to C8 / C0SOC; 19) Let stand for 5 minutes; 20) Charge with a constant current of 0.33C0 until the negative electrode potential is 0V and read the capacity C9 (also known as C0), which corresponds to 100% SOC. The required charging time is calculated by adding the total charging time from 10% SOC to 80% SOC.

[0319] 3. Volumetric energy density

[0320] At 25°C, discharge the battery cell at a constant current of 0.33C to 2.5V, let it rest for 5 minutes, then charge it at a constant current of 0.33C to the upper cutoff voltage of 3.65V. Then charge it at a constant voltage to a current of 0.05C and let it rest for 5 minutes. Discharge it at a constant current of 0.33C to a cutoff voltage of 2.5V. Record the discharge capacity at this point and calculate the discharge energy (E0). Volumetric energy density (Wh / L) = discharge energy (E0) / cell volume (L).

[0321] 4. Cycle performance

[0322] At 25°C, charge the battery to 3.65V at a 0.5C charge rate, then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, and then discharge it to 2.5V at a 1C discharge rate and let it stand for 10 minutes. The above charge and discharge is one cycle. The test is stopped until the battery capacity decays to 80% of the nominal capacity, which is recorded as the number of cycles @80% SOH.

[0323] II. Analysis of test results of various embodiments and comparative examples

[0324] The battery cells of each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 5 below.

[0325] Table 1 Negative electrode sheet preparation parameters

[0326]

[0327] Table 2. Preparation parameters of positive electrode sheet

[0328]

[0329] Table 3 Electrolyte preparation parameters

[0330]

[0331] Table 4 Electrolyte preparation parameters

[0332]

[0333] Table 5 Battery performance parameters

[0334]

[0335] In the battery cells of Examples 1 to 13, the positive electrode film layer uses a lithium-containing phosphate containing an olivine structure as the positive electrode active material, and the negative electrode film layer uses graphite with an average particle size Dv50 of 8 μm to 15 μm as the negative electrode active material; and Figure 4As shown, in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate includes first lithium-containing phosphate particles with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum 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, cycle performance, and low DC internal resistance.

[0336] The average particle size Dv50 of the graphite in the negative electrode film layers of Comparative Examples 1 and 2 exceeds the range of 8 μm to 15 μm, wherein: the Dv50 of the graphite in Comparative Example 1 is too large, while the Dv50 of the graphite in Comparative Example 2 is too small.

[0337] From the comparison between Comparative Examples 1-2 and Examples 1-13, 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; and 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 is also reduced; therefore, the average particle size Dv50 of the graphite in the negative electrode film layer needs to be within the range of 8 μm to 15 μm to improve the cycle performance, fast charging performance, DC internal resistance and energy density of the battery. When it exceeds this range, the overall performance of the battery is poor.

[0338] In the positive electrode film of Comparative Example 3, the lithium-containing phosphate includes second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm, but does not include first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm.

[0339] From the comparison between Comparative Example 3 and Examples 1 to 13, it can be seen that when the lithium phosphate in the positive electrode film layer does not use a particle size grading method, and only uses particles with larger particle sizes (the longest diameter is 1μm to 3μm), the improvement effect on the battery fast charging performance and DC internal resistance is limited, and the energy density will be deteriorated.

[0340] In the positive electrode film of Comparative Example 4, the lithium-containing phosphate includes first lithium-containing phosphate particles with a longest diameter of 0.05 μm to 0.3 μm, but does not include second lithium-containing phosphate particles with a longest diameter of 1 μm to 3 μm.

[0341] Comparing Comparative Example 4 with Examples 1-13 shows that when the lithium phosphate in the positive electrode film layer uses only small particle sizes (0.05μm to 0.3μm in longest diameter) without using a large-size particle gradation, the electrode sheet's compaction density is low, thus deteriorating the energy density. Therefore, using both small particle sizes (0.05μm to 0.3μm in longest diameter) and large particle sizes (1μm to 3μm in longest diameter) in the positive electrode film layer improves the battery's energy density, cycling performance, fast-charging performance, and DC internal resistance. Exceeding this range results in poor overall battery performance.

[0342] In Examples 1 to 5, the average particle size Dv50 of the graphite in the negative electrode film layer is in the range of 8μm to 15μm, and the battery cells prepared therefrom can achieve excellent energy density, fast charging performance, cycle performance, and low DC internal resistance. In addition, the results also show that when the graphite Dv50 gradually increases within the range of 8μm to 15μm, the battery's cycle performance 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; while when the graphite Dv50 gradually decreases within the range of 8μm to 15μm, the battery's fast charging performance is improved to a certain extent, the DC internal resistance decreases to a certain extent, but the cycle performance decreases to a certain extent. Therefore, only when the Dv50 of the graphite in the negative electrode film layer is in the range of 8μm to 15μm can it achieve the goal of improving the battery's fast charging performance, cycle performance, and DC internal resistance; and when the graphite Dv50 is in the range of 9.5μm to 11.5μm, the battery's overall performance is even better. When the Dv50 of graphite is too low, the energy density of the battery decreases.

[0343] In Examples 1 and 6, the lithium-containing phosphate in the positive electrode film layer includes first lithium-containing phosphate particles with a maximum diameter of 0.05 μm to 0.3 μm and second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm. The battery cells prepared therefrom can achieve excellent energy density, fast charging performance, cycle performance, and low DC internal resistance. In addition, a comparison between Example 1 and Example 6 shows that when the number of first lithium-containing phosphate particles with a maximum diameter of 0.05 μm to 0.3 μm is greater than the number of second lithium-containing phosphate particles with a maximum diameter of 1 μm to 3 μm, the battery's DC internal resistance and fast charging performance can be further improved, resulting in better overall battery performance.

[0344] In Examples 1, 7 to 10, the electrolyte adopts the following formula, and the battery monomers prepared therefrom can take into account excellent energy density, fast charging performance, cycle performance, and low DC internal resistance: the organic solvent adopts a linear carboxylate (such as ethyl acetate) with a mass proportion of 40% to 75%, a linear carbonate (such as DMC, EMC) with a mass proportion of 10% to 40%, and a cyclic carbonate (such as ethylene carbonate), of which the mass proportion of dimethyl carbonate is 5% to 15%, and the mass ratio of linear carboxylate (such as ethyl acetate) to dimethyl carbonate is 2.0 to 7.0; the lithium salt adopts LiPF6 and LiFSI with a mass proportion of 13% to 20%, and the mass ratio of LiPF6 to LiFSI is 1.2:1 to 2:1.

[0345] At the same time, a comparison of Examples 1, 7, and 8 shows that: as the proportion of linear carboxylic acid esters (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; and as the proportion of linear carbonates (such as DMC) and LiPF6 added to the electrolyte gradually increases, the cycle performance of the battery is further improved.

[0346] At the same time, a comparison of Examples 1, 9, and 10 shows that when only linear carboxylates (such as ethyl acetate) are present in the organic solvent of the electrolyte without carbonates, and only LiFSI is present in the lithium salt without LiPF6, the fast charging performance and DC internal resistance of the battery are further improved, but the battery's cycling performance is poor. When only linear carbonates (such as DMC) are present in the organic solvent of the electrolyte without linear carboxylates, and only LiPF6 is present in the lithium salt without LiFSI, the battery's cycling performance is further improved, but the improvement in fast charging performance and DC internal resistance is limited. Therefore, when the above-mentioned mass ratio of linear carbonates and linear carboxylates is used as organic solvents in the electrolyte, and the above-mentioned mass ratio of LiPF6 and LiFSI is used as lithium salts, the combination of multiple solvents and lithium salts can further improve the battery's fast charging performance, DC internal resistance, and cycling performance, thereby improving the battery's overall performance.

[0347] In Examples 1 and 11, the negative electrode film layer includes at least one layer of graphite as the negative electrode active material, and its average particle size Dv50 is within the range of 8μm to 15μm. The battery cells prepared therefrom can achieve excellent energy density, fast charging performance, cycle performance, and low DC internal resistance. In addition, a comparison between Example 1 and Example 11 shows 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, and 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 the Dv50 of the second negative electrode active material layer), it can further improve the battery's fast charging performance and DC internal resistance, thereby improving the battery's overall performance.

[0348] In Examples 1, 12, and 13, the ratio of the thickness of the positive electrode film layer on a single surface to the thickness of the positive electrode current collector is 5 to 12, and the ratio of the thickness of the negative electrode film layer on a single surface to the thickness of the negative electrode current collector is 12 to 20. The resulting battery cells can achieve excellent energy density, fast-charging performance, cycling performance, and low DC internal resistance. Furthermore, the results show that increasing the ratio of the thickness of the positive and negative electrode film layers on a single surface to the thickness of the positive and negative electrode current collectors within the aforementioned range can further improve the battery's energy density; and decreasing the ratio of the thickness of the positive and negative electrode film layers on a single surface to the thickness of the positive and negative electrode current collectors within the aforementioned range can further improve the battery's fast-charging performance, DC internal resistance, and cycling performance.

[0349] In Examples 1 to 13, the specific surface area of ​​graphite in the positive electrode film is 3 m 2 / g to 8 m 2 / g, the compaction density of the positive electrode is 2.3g / cm 3 Up to 2.6g / cm 3 The compaction density of the negative electrode is 1.3g / cm 3 Up to 1.6g / cm 3 The battery cells prepared therefrom can have excellent energy density, fast charging performance, cycle performance, and low DC internal resistance.

[0350] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: It includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator located between the positive electrode sheet and the negative electrode sheet. 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, 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 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 ratio of the thickness of a single surface of the positive electrode film layer to the thickness of the positive electrode current collector is 5 to 12; 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 8 μm to 15 μm, and the negative electrode active material includes graphite; The electrolyte comprises an organic solvent and a lithium salt, wherein the organic solvent comprises a linear carboxylate; the mass proportion of the lithium salt is 13% to 20% based on the total mass of the electrolyte.

2. The battery cell according to claim 1, wherein: 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, wherein: 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, wherein: 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 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; and 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 to 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 to 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 to 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, wherein 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 thickness of the positive electrode film layer on a single side to the thickness of the positive electrode current collector is 6 to 10.

15. 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 .

16. 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 .

17. 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 .

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 0.165 g / 1540.25 mm 2 .

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

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

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

22. 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.

23. The battery cell according to claim 22, characterized in that The average particle size Dv50 of the first artificial graphite is 11 μm to 15 μm.

24. The battery cell according to claim 22, characterized in that The average particle size Dv50 of the second artificial graphite is 8 μm to 15 μm.

25. The battery cell according to claim 22, characterized in that The average particle size Dv50 of the second artificial graphite is 9.5 μm to 11.5 μm.

26. The battery cell according to claim 1, characterized in that The organic solvent also includes a carbonate solvent.

27. The battery cell according to claim 1, characterized in that The linear carboxylic acid ester accounts for 40% to 75% by mass, based on the total mass of the electrolyte.

28. The battery cell according to claim 1, 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.

29. The battery cell according to claim 28, 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.

30. The battery cell according to any one of claims 26 to 29, 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.

31. The battery cell according to claim 30, 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.

32. The battery cell according to claim 31, 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%.

33. The battery cell according to claim 26, 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.

34. The battery cell according to claim 33, characterized in that The mass ratio of the linear carboxylic acid ester to the dimethyl carbonate is 3.0 to 6.

0.

35. The battery cell according to claim 1, 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.

36. The battery cell according to claim 1, characterized in that The lithium salt includes lithium hexafluorophosphate LiPF6 and lithium bis(fluorosulfonyl)imide LiFSI.

37. The battery cell according to claim 1, 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.

38. The battery cell according to claim 26, characterized in that The electrolyte includes carbonate additives, and the carbonate additives include fluoroethylene carbonate FEC and vinylene carbonate VC.

39. The battery cell according to claim 38, characterized in that Based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 0.5% to 7%.

40. The battery cell according to claim 38 or 39, 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.

41. The battery cell according to claim 38 or 39, 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.

42. The battery cell according to claim 1, characterized in that The positive electrode current collector includes a positive electrode current collecting portion and at least two positive electrode tabs arranged on the same side of the positive electrode current collecting portion, the positive electrode tabs extending from the positive electrode 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 lines are parallel to the first direction; and / or, the negative electrode current collector includes a negative electrode current collecting portion and at least two negative electrode tabs arranged on the same side of the negative electrode current collecting portion, the negative electrode tabs extending from the negative electrode 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 lines are parallel to the first direction.

43. The battery cell according to claim 42, 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 tabs is 20 mm to 330 mm.

44. The battery cell according to claim 42, 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.

45. The battery cell according to any one of claims 42 to 44, 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.

46. ​​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.

47. 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 minutes to 17 minutes at room temperature.

48. A battery device, characterized in that The battery device comprises the battery cell according to any one of claims 1 to 47, wherein the battery device is at least one of a battery module and a battery pack.

49. An electrical device, characterized in that: The battery cell according to any one of claims 1 to 47 or the battery device according to claim 48 is included.

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