Battery cell and electrical apparatus

Abstract

Provided in the present application are a battery cell and an electrical apparatus. The battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on the surface of at least one side of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate, and the areal density of the positive electrode film layer on one surface being 0.35g / 1540.25mm2 to 0.5g / 1540.25mm2. The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on the surface of at least one side of the negative electrode current collector, the areal density of the negative electrode film layer on one surface being 0.13g / 1540.25mm2 to 0.19g / 1540.25mm2. The negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprising a silicon element-containing material, and the mass ratio of the silicon element to the negative electrode active material being 2% to 10%.

Description

Battery cell and electric device TECHNICAL FIELD

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

[0002] In recent years, battery cells are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the popularization of battery cell applications, higher requirements are put forward for its power performance, cycle performance, service life, etc.

[0003] SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a novel battery cell with high energy density, while taking into account excellent fast charging performance and cycle performance.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a battery cell, the battery cell comprising a positive electrode sheet, a negative electrode sheet and a separator film arranged between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate, the areal density of the single-sided positive electrode film layer being 0.35 g / 15 40.25 mm 2 to 0.5 g / 15 40.25 mm 2 ; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side surface of the negative electrode current collector, the areal density of the single-sided negative electrode film layer being 0.13 g / 15 40.25 mm 2 to 0.19 g / 15 40.25 mm 2 ; the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprising a material containing silicon element, the mass fraction of silicon element based on the negative electrode active material being 2% to 10%.

[0006] In the battery cell provided by the present application, the lithium-containing phosphate with an areal density in the above range is used in the positive electrode film layer, which can effectively improve the problem of low energy density when the lithium-containing phosphate is used as the positive electrode active material, and can maintain the basic charging capacity of the battery, taking into account the improvement of the energy density and charging performance of the battery; at the same time, the negative electrode active material containing silicon element in the above range is used in the negative electrode film layer, which can effectively improve the negative electrode capacity, and when the areal density in the above range is used, the fast charging performance of the battery can also be improved.

[0007] In addition, by matching the positive electrode film layer and the negative electrode film layer in a proper surface density ratio, the problem of lithium precipitation can be better improved, and the battery monomer has higher energy density, better charging capacity and better cycle performance, and the battery performance is comprehensively improved.

[0008] In any embodiment, the proportion of silicon element in the negative electrode active material is 4% to 8% based on the mass of the negative electrode active material.

[0009] When the negative electrode active material containing the silicon element in the above range is used in the negative electrode film layer, the energy density and charging performance of the battery can be further improved.

[0010] In any embodiment, the negative electrode active material includes a silicon-based material and a carbon-based material, the silicon-based material includes one or more of silicon-carbon composite and silicon oxide compound; and / or, the carbon-based material includes one or more of artificial graphite and natural graphite.

[0011] When the graphite-based carbon-based material is used as the negative electrode active material, it has good electrochemical performance, long cycle life and low cost; and when the silicon-based material is used together with the graphite-based carbon-based material, the specific capacity of the negative electrode active material can be further improved.

[0012] In any embodiment, the battery monomer further includes an electrolyte, and the electrolyte includes an organic solvent, the organic solvent includes a carbonate solvent, and the carbonate solvent includes one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate and methyl ethyl carbonate.

[0013] When the above type of carbonate solvent is used in the electrolyte, the problem of wettability of the positive and negative electrode sheets in the electrolyte can be further improved; when the positive and negative electrode film layers with the above surface density are matched, the problem of wettability of the electrode sheets in the electrolyte caused by high surface density can be further avoided, and the performance of the battery is comprehensively improved.

[0014] In any embodiment, the organic solvent includes dimethyl carbonate, and the mass proportion of dimethyl carbonate is 4% to 20% based on the total mass of the electrolyte.

[0015] In any embodiment, the organic solvent includes dimethyl carbonate, and the mass proportion of dimethyl carbonate is 8% to 16% based on the total mass of the electrolyte.

[0016] When the above proportion range of dimethyl carbonate is used as the electrolyte solvent, the wettability problem can be improved while the gas production is improved, and the cycle performance of the battery is comprehensively improved.

[0017] In any embodiment, the electrolyte further comprises an additive, the additive comprises a carbonate additive; the carbonate additive comprises one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone.

[0018] When the electrolyte uses the carbonate additive of the above type, an SEI film can be generated on the surface of the silicon-containing negative electrode, the SEI film can cover the surface of the electrode tab to reduce the degree of exposure of the electrode tab to the electrolyte, reduce the side reaction and gas production on the surface of the silicon-containing negative electrode, and further improve the cycle performance of the battery.

[0019] In any embodiment, the additive comprises fluoroethylene carbonate, and the mass fraction of the fluoroethylene carbonate in the electrolyte is 5% to 30% based on the total mass of the electrolyte.

[0020] In any embodiment, the additive comprises fluoroethylene carbonate, and the mass fraction of the fluoroethylene carbonate in the electrolyte is 5% to 15% based on the total mass of the electrolyte.

[0021] When the electrolyte uses the fluoroethylene carbonate in the above proportion range as a solvent, the side reaction and gas production on the surface of the silicon-containing negative electrode can be further improved, thereby further improving the cycle performance of the battery.

[0022] In any embodiment, the electrolyte has an electrical conductivity of 9 mS / cm to 14 mS / cm.

[0023] The battery cell provided in the present application has an electrical conductivity in the above range, and thus has good electrochemical performance.

[0024] In any embodiment, in a cross section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate comprises lithium-containing phosphate particles with a longest diameter of 1 μm to 5 μm and lithium-containing phosphate particles with a longest diameter of 0.1 μm to 0.3 μm.

[0025] When the lithium-containing phosphate in the positive electrode film layer adopts a size particle diameter matching form, the compaction density of the electrode tab can be improved, and the energy density of the battery is further improved; and when the size particle diameter matching adopts the particle diameter range described above, the compaction density of the electrode tab can be in a suitable range, so that the energy density and cycle performance are improved.

[0026] At the same time, when the size particle diameter matching positive electrode active material is matched with the electrolyte provided in the present application, the electrolyte immersion problem caused by the high compaction density of the electrode tab can be further avoided, and the battery performance is comprehensively improved.

[0027] In any embodiment, the lithium-containing phosphate has a general formula as shown in Formula I,

[0028] Li x Ay Me a M b P 1-c X c Y z Formula I,

[0029] wherein, 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A comprises one or several of Na, K, Mg; Me comprises one or several of Mn, Fe, Co, Ni; M comprises one or several of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X comprises one or several of S, Si, Cl, B, C, N; Y comprises one or several of O, F.

[0030] When the above type of lithium-containing phosphate is used as the positive electrode active material, the battery has good energy density and cycle performance.

[0031] In any embodiment, the positive electrode film layer comprises a lithium supplementing material, and the lithium supplementing material comprises one or more of a ternary material, lithium phosphate, lithium ferrite, lithium nickelate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, and trilithium citrate.

[0032] When the lithium-containing phosphate is used as the positive electrode active material, and the above type of lithium supplementing material is simultaneously applied, the specific capacity of the positive electrode active material can be further improved.

[0033] In any embodiment, the lithium supplementing material has a coating layer on at least part of the surface thereof.

[0034] In any embodiment, the coating layer comprises a carbon-containing coating layer, and the thickness of the carbon-containing coating layer is 10 nm to 200 nm.

[0035] The carbon coating on the surface of the lithium supplementing material can effectively protect the lithium supplementing material in the core part. The lithium supplementing material after carbon coating has a stable structure, alleviates the strong side reaction between the electrolyte and the lithium supplementing material, and thus can further improve the energy density and cycle performance of the battery. On the other hand, the carbon coating can also increase the conductivity of the lithium supplementing agent, reduce the lithium stripping potential, reduce the formation stage voltage, and alleviate the adverse effects of high voltage on the decomposition of electrolyte components.

[0036] In any embodiment, there is a gap between the lithium supplementing material and the carbon-containing coating layer, and the width of the gap is 5 nm to 50 nm.

[0037] When there is a gap between the lithium supplement material and the carbon coating layer on the surface of the lithium supplement material, the lithium supplement material is beneficial to fully contact with the electrolyte, thereby achieving effective lithium supplement effect and further improving the energy density of the battery.

[0038] In any embodiment, the longest diameter of the lithium supplement material is 5-20 μm.

[0039] In any embodiment, the longest diameter of the lithium supplement material is 6-12 μm.

[0040] In any embodiment, the mass ratio of the lithium supplement material is 0.2-2% based on the total mass of the positive electrode film layer.

[0041] In any embodiment, the mass ratio of the lithium supplement material is 0.1-1% based on the total mass of the positive electrode film layer.

[0042] When the lithium supplement material with the above particle size and proportion range is used, the stability of the lithium supplement material can be effectively improved, and the lithium supplement effect is also good.

[0043] In any embodiment, the compaction density of the positive electrode tab is 2.45 g / cm 3 -2.65 g / cm 3 .

[0044] The positive electrode tab provided in the application has the compaction density in the above range, and thus has good energy density.

[0045] In any embodiment, the thickness of the positive electrode current collector is 10-15 μm.

[0046] In any embodiment, the thickness of the positive electrode current collector is 10-13 μm.

[0047] The positive electrode current collector with the above thickness range can further improve the energy density.

[0048] In any embodiment, the ratio of the single-side thickness of the positive electrode film layer to the thickness of the positive electrode current collector is greater than 8 and less than 20.

[0049] In any embodiment, the ratio of the single-side thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 11-14.

[0050] When the positive electrode film layer and the positive electrode current collector with the above thickness range are matched, the energy density and the charging performance can be further considered, and the battery performance is comprehensively improved.

[0051] In any embodiment, the compaction density of the negative electrode tab is 1.4 g / cm 3 -1.6 g / cm 3 .

[0052] The negative electrode tab provided by the present application has the compaction density in the above range, and thus has a good energy density.

[0053] In any embodiment, the thickness of the negative electrode current collector is 4-6 μm.

[0054] In any embodiment, the thickness of the negative electrode current collector is 4-5.5 μm.

[0055] The negative electrode current collector with the above thickness range can further improve the energy density.

[0056] In any embodiment, the ratio of the single-side thickness of the negative electrode film layer to the thickness of the negative electrode current collector is greater than 11 and less than 20.

[0057] In any embodiment, the ratio of the single-side thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 12-18.

[0058] When the negative electrode film layer with the above thickness range is matched with the negative electrode current collector, the energy density and the charging performance can be further considered, and the battery performance can be comprehensively improved.

[0059] In any embodiment, the separator film comprises a substrate and a ceramic coating layer arranged at least on the side close to the positive electrode tab.

[0060] The ceramic coating layer arranged on the surface of the substrate can improve its thermal safety; and the voltage on the side close to the positive electrode tab is higher, and the ceramic coating layer arranged on this side can further improve its oxidation resistance.

[0061] In any embodiment, the substrate comprises one or more of a polypropylene film, a polyethylene film and a polyimide film.

[0062] In any embodiment, the substrate comprises a polypropylene film, and the thickness of the polypropylene film is 9-14 μm; and / or the substrate comprises a polyethylene film, and the thickness of the polyethylene film is 5-8 μm.

[0063] In any embodiment, the thickness of the ceramic coating layer is 1-3 μm.

[0064] When the substrate and the ceramic coating layer with the above thickness range are matched, the ion permeability and the internal resistance of the separator film can be considered on the basis of improving its thermal safety.

[0065] In any embodiment, the battery cell comprises an electrode assembly, the electrode assembly comprises a positive electrode sheet, a separator film and a negative electrode sheet which are sequentially stacked, the ratio of the size of the positive electrode film layer along the length direction of the electrode assembly to the size of the electrode assembly along the length direction of the electrode assembly is 92-95%, and the ratio of the size of the positive electrode film layer along the width direction of the electrode assembly to the size of the electrode assembly along the width direction of the electrode assembly is greater than or equal to 92-96%.

[0066] The battery cell provided in the application can further improve the energy density of the battery when the above-mentioned laminated sheet battery is used.

[0067] In any embodiment, the positive electrode sheet comprises a positive electrode tab, and the negative electrode sheet comprises a negative electrode tab; the positive electrode tab extends out along a first direction of the positive electrode sheet, and the ratio of the width of the positive electrode tab to the width of the positive electrode sheet in a second direction of the positive electrode sheet is 50-100%, and the second direction is perpendicular to the first direction.

[0068] The battery cell provided in the application can further improve the charging temperature rise of the battery when the above-mentioned width range and structural features of the electrode sheet are used.

[0069] In any embodiment, the battery cell further comprises a top cover, and the top cover is provided with an electrode terminal for directly connecting with the positive electrode tab and / or the negative electrode tab.

[0070] In a conventional battery, a jumper is needed to connect the electrode terminal and the tab, but this will cause a loss of utilization of the electrode assembly and reduce the energy density of the battery. The battery cell provided in the application can effectively solve this problem by canceling the jumper, reduce the internal resistance of the battery, and further improve the energy density and fast charging performance of the battery.

[0071] In any embodiment, the battery cell further comprises a shell, and the shell is an aluminum shell, and the thickness of the aluminum shell is 0.2-0.3 mm.

[0072] In any embodiment, the ratio of the length to the width of the shell is 4-7.

[0073] In any embodiment, the length of the shell is 400-600 mm, the width is 90-120 mm, and the height is 13-25 mm.

[0074] The shell with the above-mentioned size range can improve the energy density while reducing the internal resistance of the battery, thereby improving the energy density and fast charging performance of the battery.

[0075] In any embodiment, the mass energy density of the battery cell is 210-250 Wh / Kg.

[0076] The second aspect of the present application also provides a power consuming device comprising the battery cell of the first aspect of the present application.

[0077] In any embodiment, the power consuming device comprises a vehicle, and the length direction of the electrode assembly is placed along a traveling direction of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0078] FIG. 1 is an electron microscope observation result of a positive electrode film layer prepared in an embodiment of the present application; wherein 6 represents a lithium supplement material, 61 represents a carbon coating layer on the surface of the lithium supplement material, 62 represents a gap between the lithium supplement material and the carbon coating layer, 7 represents lithium-containing phosphate particles with a longest diameter of 1-5 μm, and 8 represents lithium-containing phosphate particles with a longest diameter of 0.1-0.3 μm;

[0079] FIG. 2 is a schematic diagram of a battery cell in an embodiment of the present application;

[0080] FIG. 3 is an exploded view of the battery cell in the embodiment of the present application shown in FIG. 2;

[0081] FIG. 4 is a schematic diagram of a battery module in an embodiment of the present application;

[0082] FIG. 5 is a schematic diagram of a battery pack in an embodiment of the present application;

[0083] FIG. 6 is an exploded view of the battery pack in the embodiment of the present application shown in FIG. 5;

[0084] FIG. 7 is a schematic diagram of a power consuming device using the battery cell in an embodiment of the present application as a power source.

[0085] REFERENCE SIGNS DETAILED DESCRIPTION

[0086] Hereinafter, embodiments of the battery cell and the power consuming device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are well known, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0087] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0088] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0089] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0090] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0091] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0092] If not specifically stated, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0093] When lithium-containing phosphates are used as positive electrode active materials, for example, lithium iron phosphate positive electrode active materials, there is often a problem of low gravimetric capacity. Conventional negative electrode active materials, for example, graphite, also have a problem of low gravimetric capacity. Thick coating of positive electrode and negative electrode sheets can improve the energy density of the battery cell to some extent, but thick coating can also cause the electrode sheets to be difficult to fully soak in the electrolyte, thereby deteriorating the kinetics and cycle performance of the battery.

[0094] To solve the above problems, the present application provides a battery cell, which comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator film arranged between the positive electrode sheet and the negative electrode sheet.

[0095] [Positive electrode sheet]

[0096] In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side surface of the positive electrode current collector. For example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0097] In some embodiments, the areal density of the positive electrode film layer on one side is 0.35g / 15 40.25mm 2 to 0.5g / 15 40.25mm 2 such as 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.42, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, or 0.50, or other unlisted values within the range of 0.35g / 15 40.25mm 2 to 0.5g / 15 40.25mm 2 .

[0098] In the battery cell provided by the present application, the lithium-containing phosphate with an areal density within the above range is used in the positive electrode film layer, which can effectively improve the problem of low energy density when lithium-containing phosphate is used as a positive electrode active material, and can maintain the basic charging capacity of the battery, and improve the energy density and charging performance of the battery.

[0099] As used herein, the "areal density" of the positive electrode film layer or the negative electrode film layer has the meaning known in the art and can be tested using methods known in the art. For example, a single-side coated and cold-pressed negative electrode sheet (if it is a double-side coated negative electrode sheet, the negative electrode film layer on one side can be wiped off first) is punched into a small round piece with an area of S1, weighed, and recorded as M1. Then the negative electrode film layer of the weighed negative electrode sheet is wiped off, the weight of the negative electrode current collector is weighed and recorded as M0, and the areal density of the negative electrode film layer = (weight of the negative electrode sheet M1 - weight of the negative electrode current collector M0) / S1. To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of samples to be tested can be tested, and the average value is calculated as the test result.

[0100] In some embodiments, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium-containing phosphate.

[0101] In some embodiments, the lithium-containing phosphate has a general formula as shown in Formula I,

[0102] Li x A y Me a M b P 1-c X c Y z Formula I,

[0103] wherein 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A comprises one or more of Na, K, Mg; Me comprises one or more of Mn, Fe, Co, Ni; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X comprises one or more of S, Si, Cl, B, C, N; and Y comprises one or more of O, F.

[0104] When the lithium-containing phosphate of the above type is used as the positive electrode active material, the battery has good energy density and cycle performance.

[0105] As used herein, "the general formula of the lithium-containing phosphate is shown as formula I" is not limited to the substances represented by the general formula of the molecule, but also includes other substances formed by further appropriate modification on the basis of the general formula of the molecule, which is not limited herein. The use of "general formula" is only for convenience of description and is not intended to limit the present application. It can be understood that new materials or new substances obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode active materials, and the foregoing appropriate modification refers to acceptable modification of the positive electrode active material, and non-limiting examples include coating modification.

[0106] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate includes lithium-containing phosphate particles with a longest diameter of 1 μm to 5 μm and lithium-containing phosphate particles with a longest diameter of 0.1 μm to 0.3 μm. In some embodiments, the lithium-containing phosphate particles with a longest diameter of 1 μm to 5 μm are, for example, 1, 1.5, 2, 2.5, 3, 5, or other unlisted values within the range of 1 μm to 5 μm. In some embodiments, the lithium-containing phosphate particles with a longest diameter of 0.1 μm to 0.3 μm are, for example, 0.1, 0.15, 0.2, 0.25, 0.3, or other unlisted values within the range of 0.1 μm to 0.3 μm.

[0107] When the lithium-containing phosphate in the positive electrode film layer is in the form of a combination of particle sizes, the compaction density of the electrode tab can be improved, further improving the energy density of the battery; and when the particle size range is used, the compaction density of the electrode tab can be within a suitable range, thereby improving the energy density and cycle performance.

[0108] At the same time, when the positive electrode active material with a combination of particle sizes is combined with the electrolyte provided in the present application, the problem of electrolyte infiltration caused by high compaction density of the electrode tab can be further avoided, and the battery performance is comprehensively improved.

[0109] In some embodiments, "the longest diameter" refers to: cutting the positive electrode tab including lithium-containing phosphate particles along the thickness direction of the tab to expose the longitudinal section of the positive electrode film layer; determining the longest diameter of the lithium-containing phosphate particles by scanning electron microscopy (SEM) test on the longitudinal section of the positive electrode film layer. Specifically, the "longest diameter" of the lithium-containing phosphate particles refers to the longest straight line passing through the center point of the lithium-containing phosphate particles and extending to the outer periphery of the particles.

[0110] In some embodiments, the positive electrode film layer further includes a lithium supplementing material, and the lithium supplementing material includes one or more of ternary materials, lithium phosphate, lithium ferrite, lithium nickelate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, and trilithium citrate.

[0111] When the lithium-containing phosphate is used as the positive active material, and the above-mentioned lithium supplementing material is simultaneously used, the specific capacity of the positive active material can be further improved.

[0112] In some embodiments, the lithium supplementing material has a coating layer on at least part of the surface thereof.

[0113] In some embodiments, the coating layer comprises a carbon-containing coating layer, and the thickness of the carbon-containing coating layer is 10 nm to 200 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, or other values not listed in the range of 10 nm to 200 nm.

[0114] The carbon coating on the surface of the lithium supplementing material can effectively protect the lithium supplementing material in the core part. The lithium supplementing material after carbon coating has a stable structure, and the strong side reaction between the electrolyte and the lithium supplementing material is avoided, thereby further improving the energy density and cycle performance of the battery.

[0115] In some embodiments, the lithium supplementing material and the carbon-containing coating layer have a gap therebetween, and the width of the gap is 5 nm to 50 nm, for example, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or other values not listed in the range of 5 nm to 50 nm.

[0116] When the lithium supplementing material and the carbon coating layer on the surface thereof have a gap therebetween, the lithium supplementing material can be fully contacted with the electrolyte, thereby achieving effective lithium supplementing effect and further improving the energy density of the battery.

[0117] In some embodiments, the longest diameter of the lithium supplementing material is 5 μm to 20 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or other values not listed in the range of 5 μm to 20 μm.

[0118] In some embodiments, the longest diameter of the lithium supplementing material is 6 μm to 12 μm.

[0119] In some embodiments, the "longest diameter" refers to: cutting the positive electrode tab including the lithium supplement material particles along the thickness direction of the tab to expose the longitudinal section of the positive electrode film layer; and determining the longest diameter of the lithium supplement material particles by scanning electron microscopy (SEM) test on the longitudinal section of the positive electrode film layer. Specifically, the "longest diameter" of the lithium supplement material particles refers to the longest straight line passing through the center point of the lithium supplement material particles and extending to the outer periphery of the particles.

[0120] In some embodiments, the mass percentage of the lithium supplement material is 0.2% to 2%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or the like, or other unlisted values within the range of 0.2% to 2%, based on the total mass of the positive electrode film layer.

[0121] In some embodiments, the mass percentage of the lithium supplement material is 0.1% to 1%, based on the total mass of the positive electrode film layer.

[0122] When the lithium supplement material with the above particle size and proportion range is used, the stability of the lithium supplement material can be effectively improved, and the lithium supplement effect is also good.

[0123] In some embodiments, the positive electrode current collector can use a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one side surface of the polymer material base layer. As an example, the metal material can include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0124] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 15 μm, for example, 10, 11, 12, 13, 14, 15, or the like, or other unlisted values within the range of 10 μm to 15 μm. In some embodiments, the thickness of the positive electrode current collector is 10 μm to 13 μm.

[0125] The positive electrode current collector with the above thickness range can further improve the energy density.

[0126] In some embodiments, the ratio of the single-side thickness of the cathode film layer to the thickness of the cathode current collector is greater than 8 and less than 20, for example, 8.1, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 19.9, or other unlisted values within the range of greater than 8 and less than 20. In some embodiments, the ratio of the single-side thickness of the cathode film layer to the thickness of the cathode current collector is 11 to 14.

[0127] When the cathode film layer having the above thickness range is matched with the cathode current collector, the energy density and the charging performance can be further balanced, and the battery performance can be comprehensively improved.

[0128] In some embodiments, the cathode film layer optionally further comprises a cathode conductive agent. The type of the cathode conductive agent is not particularly limited in the present application, and as an example, the cathode conductive agent comprises at least one of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0129] In some embodiments, the cathode film layer optionally further comprises a cathode binder. The type of the cathode binder is not particularly limited in the present application, and as an example, the cathode binder can comprise at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0130] In some embodiments, the cathode electrode sheet can be prepared by dispersing the above components for preparing the cathode electrode sheet, such as the cathode active material, the conductive agent, the binder, and any other components, in a solvent (for example, N-methylpyrrolidone) to form a cathode slurry; coating the cathode slurry on the cathode current collector, and after drying, cold pressing, and other processes, the cathode electrode sheet can be obtained.

[0131] In some embodiments, the compaction density of the cathode electrode sheet is 2.45 g / cm 3 to 2.65 g / cm 3 , for example, 2.45, 2.50, 2.55, 2.60, 2.65, or other unlisted values within the range of 2.45 g / cm 3 to 2.65 g / cm 3 .

[0132] The cathode electrode sheet provided in the present application has a compaction density within the above range, and thus has a good specific capacity.

[0133] As used herein, the “compaction density” of the electrode sheet is: compaction density = areal density / (electrode sheet thickness - current collector thickness), and the determination method can refer to GB / T 24533-2009.

[0134] [negative electrode sheet]

[0135] In some embodiments, the negative electrode sheet includes a negative current collector and a negative film layer disposed on at least one side surface of the negative current collector, the negative film layer including a negative active material. As an example, the negative current collector has two surfaces opposite in its own thickness direction, and the negative film layer is disposed on any one or both of the two surfaces of the negative current collector.

[0136] In some embodiments, the negative film layer has an areal density of 0.13 g / 15 40.25 mm 2 to 0.19 g / 15 40.25 mm 2 such as 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, etc., or other unlisted values within the range of 0.13 g / 15 40.25 mm 2 to 0.19 g / 15 40.25 mm 2 .

[0137] In some embodiments, the negative film layer includes a negative active material, the negative active material including a material containing silicon element.

[0138] The battery cell provided in the present application uses the negative active material containing silicon element within the above range in the negative film layer, which can effectively improve the negative electrode specific capacity. When the areal density within the above range is also used, the fast charging performance of the battery can also be improved.

[0139] In addition, by matching the positive film layer and the negative film layer at a proper areal density ratio, the problem of lithium precipitation can be avoided, and the battery cell has higher energy density, better charging capacity, and better cycle performance, thereby comprehensively improving the battery performance.

[0140] In some embodiments, the silicon element accounts for 2% to 10% of the mass of the negative active material, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or other unlisted values within the range of 2% to 10%. In some embodiments, the silicon element accounts for 4% to 8% of the mass of the negative active material.

[0141] When the negative film layer uses the negative active material containing silicon element within the above range, the energy density and charging performance of the battery can be further improved.

[0142] In some embodiments, the negative active material comprises a silicon-based material and a carbon-based material, the silicon-based material comprises one or more of silicon-carbon composite, silicon oxide compound; and / or, the carbon-based material comprises one or more of artificial graphite, natural graphite.

[0143] Graphite-based carbon material as negative active material has good electrochemical performance, long cycle life and low cost; and silicon-based material and graphite-based carbon material together can further improve the specific capacity of the negative active material.

[0144] In some embodiments, the negative current collector can be a metal foil or a composite current collector. For example, as a metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base material. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0145] In some embodiments, the thickness of the negative current collector is 4 μm to 6 μm, for example, 4, 4.5, 5, 5.5, 6, etc., or other unlisted values within the range of 4 μm to 6 μm. In some embodiments, the thickness of the negative current collector is 4 μm to 5.5 μm.

[0146] The negative current collector with the above thickness range can further improve the energy density.

[0147] In some embodiments, the ratio of the single-sided thickness of the negative film layer to the thickness of the negative current collector is greater than 11 and less than 20, for example, 11.1, 11.5, 11.8, 12.2, 12.8, 13, 14, 15, 16, 17, 18, 19, 19.9, etc., or other unlisted values within the range of greater than 11 and less than 20. In some embodiments, the ratio of the single-sided thickness of the negative film layer to the thickness of the negative current collector is 12 to 18.

[0148] When the negative film layer and the negative current collector with the above thickness range are matched, the energy density and the charging performance can be further considered, and the battery performance can be comprehensively improved.

[0149] In some embodiments, the negative electrode film layer can further optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0150] In some embodiments, the negative electrode film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

[0152] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after processes such as drying, cold pressing, and the like, the negative electrode sheet can be obtained.

[0153] In some embodiments, the compaction density of the negative electrode sheet can be in the range of 1.4 g / cm 3 to 1.6 g / cm 3 , such as 1.4, 1.45, 1.5, 1.55, 1.6, and the like, or other unlisted values in the range of 1.4 g / cm 3 to 1.6 g / cm 3 .

[0154] The negative electrode sheet provided herein has a compaction density in the above-mentioned range, and thus has a good energy density.

[0155] In some embodiments, the compaction density of the electrode sheet described herein can be the compaction density of the corresponding electrode sheet when the battery monomer is discharged to 0% SOC state.

[0156] In some embodiments, the film layer thickness in the electrode sheet described herein can be the film layer thickness of the corresponding electrode sheet when the battery monomer is discharged to 0% SOC state.

[0157] [Electrolyte]

[0158] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. For example, the electrolyte can be liquid, solid, or gel.

[0159] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and an organic solvent.

[0160] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are in the meanings known in the art, which can be detected by using the devices and methods known in the art, for example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography according to GB / T 9722-2006 "General rule for gas chromatography of chemical reagents".

[0161] In the embodiments of the present application, the newly prepared electrolyte can be taken as the sample, or the free electrolyte obtained from the battery after the battery is fully discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0162] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are in the meanings known in the art, which can be detected by using the devices and methods known in the art, for example, the qualitative or quantitative analysis of the inorganic components / lithium salt concentrations in the electrolyte can be performed by ion chromatography according to the standard JY / T020-1996 "General rule for ion chromatography analysis method". In the embodiments of the present application, the newly prepared electrolyte can be taken as the sample, or the free electrolyte obtained from the battery after the battery is fully discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0163] In some embodiments, the organic solvent includes a carbonate solvent. In some embodiments, the carbonate solvent includes a chain carbonate compound. In some embodiments, the carbonate solvent includes one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0164] When the above-mentioned type of carbonate solvent is used in the electrolyte, the problem of the positive and negative electrode sheets being immersed in the electrolyte can be further improved; when matched with the above-mentioned areal density of the positive and negative electrode films, the problem of the electrode sheets being immersed in the electrolyte caused by high areal density can be further avoided, and the performance of the battery is comprehensively improved.

[0165] In some embodiments, the organic solvent includes dimethyl carbonate, and the mass fraction of the dimethyl carbonate based on the total mass of the electrolyte is 4% to 20%, for example, 4%, 5.6%, 7.2%, 8.8%, 10.4%, 12%, 13.6%, 15.2%, 16.8%, 18.4%, 20%, or other values in the range of 4% to 20% not listed. In some embodiments, the organic solvent includes dimethyl carbonate, and the mass fraction of the dimethyl carbonate based on the total mass of the electrolyte is 8% to 16%.

[0166] When the above-mentioned dimethyl carbonate is used as the electrolyte solvent in the above-mentioned proportion range, the problems of wettability and gas generation can be improved, and the cycle performance of the battery can be comprehensively improved.

[0167] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0168] In some embodiments, the electrolyte further comprises an additive. For example, the additive can comprise a negative electrode film-forming additive, a positive electrode film-forming additive, and can further comprise an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, and the like.

[0169] In some embodiments, the additive comprises a carbonate additive. In some embodiments, the carbonate additive comprises a cyclic carbonate compound. In some embodiments, the carbonate additive comprises one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone.

[0170] When the above-mentioned carbonate additive is used in the electrolyte, an SEI film can be generated on the surface of the silicon-containing negative electrode, which can cover the surface of the electrode sheet to reduce the degree of exposure of the electrode sheet to the electrolyte, reduce the side reactions and gas generation on the surface of the silicon-containing negative electrode, and further improve the cycle performance of the battery.

[0171] In some embodiments, the additive comprises fluoroethylene carbonate, and the mass fraction of the fluoroethylene carbonate in the electrolyte is 5% to 30%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 26%, 27%, 28%, 29%, 30%, or other values in the range of 5% to 30% not listed, based on the total mass of the electrolyte. In some embodiments, the additive comprises fluoroethylene carbonate, and the mass fraction of the fluoroethylene carbonate in the electrolyte is 5% to 15%, based on the total mass of the electrolyte.

[0172] When the above-mentioned fluoroethylene carbonate is used as the electrolyte solvent in the above-mentioned proportion range, the problems of side reactions and gas generation on the surface of the silicon-containing negative electrode can be further improved, thereby further improving the cycle performance of the battery.

[0173] In some embodiments, the electrolyte has an electrical conductivity of 9 mS / cm to 14 mS / cm, for example 9, 10, 11, 12, 13, 14, or other unlisted values within the range of 9 mS / cm to 14 mS / cm.

[0174] The battery cell provided herein has an electrical conductivity within the above range, and thus has good electrochemical performance.

[0175] [Separator]

[0176] In some embodiments, the battery cell further comprises a separator. The type of separator is not particularly limited herein, and any known porous structure separator having good chemical stability and mechanical stability can be used. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0177] In some embodiments, the separator comprises a substrate and a ceramic coating disposed on at least one side close to the positive electrode tab.

[0178] The ceramic coating disposed on the surface of the substrate can improve its thermal safety. The voltage is higher on the side close to the positive electrode tab, and the ceramic coating disposed on this side can further improve its oxidation resistance.

[0179] In some embodiments, the substrate comprises one or more of a polypropylene film, a polyethylene film, and a polyimide film. In some embodiments, the substrate comprises a polypropylene film, and the thickness of the polypropylene film is 9 μm to 14 μm, for example 9, 10, 11, 12, 13, 14, or other unlisted values within the range of 9 μm to 14 μm. In some embodiments, the substrate comprises a polyethylene film, and the thickness of the polyethylene film is 5 μm to 8 μm, for example 5, 6, 7, 8, or other unlisted values within the range of 5 μm to 8 μm. In some embodiments, the thickness of the ceramic coating is 1 μm to 3 μm, for example 1, 1.5, 2, 2.5, 3, or other unlisted values within the range of 1 μm to 3 μm.

[0180] When the substrate and the ceramic coating are combined within the above thickness ranges, the ion permeability and the internal resistance of the battery cell can be improved while maintaining its thermal safety.

[0181] [Battery cell]

[0182] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator can be combined to form an electrode assembly by a rolling process or a stacking process.

[0183] In some embodiments, the battery cell comprises an electrode assembly, the electrode assembly comprises a positive electrode sheet, a separator film and a negative electrode sheet which are sequentially stacked, the ratio of the dimension of the positive electrode film layer along the length direction of the electrode assembly to the dimension of the electrode assembly along the length direction of the electrode assembly is 92-95%, for example, 92%, 93%, 94%, 95%, or other values not listed in the range of 92-95%. In some embodiments, the ratio of the dimension of the positive electrode film layer along the width direction of the electrode assembly to the dimension of the electrode assembly along the width direction of the electrode assembly is 92-96%, for example, 92%, 93%, 94%, 95%, 96%, or other values not listed in the range of 92-96%.

[0184] The battery cell provided in the present application can further improve the energy density of the battery when the above-mentioned laminated battery is used.

[0185] In some embodiments, the positive electrode sheet comprises a positive electrode tab, and the negative electrode sheet comprises a negative electrode tab.

[0186] In some embodiments, the positive electrode tab extends out along a first direction of the positive electrode sheet, and the ratio of the width of the positive electrode tab to the width of the positive electrode sheet in a second direction of the positive electrode sheet is 50-100%, for example, 50.1%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or other values not listed in the range of 50-100%. In some embodiments, the second direction is perpendicular to the first direction.

[0187] The battery cell provided in the present application can further improve the charging temperature rise of the battery when the above-mentioned width range and structural features of the electrode sheet are used.

[0188] In some embodiments, the battery cell further comprises a top cover, the top cover is provided with an electrode terminal for directly electrically connecting with the positive electrode tab and / or the negative electrode tab.

[0189] In conventional batteries, a jumper is needed to connect the electrode terminal and the tab, which will cause a loss of utilization of the electrode assembly and reduce the energy density of the battery. The battery cell provided in the present application can effectively solve this problem by canceling the jumper, reduce the internal resistance of the battery, and further improve the energy density and fast charging performance of the battery.

[0190] In some embodiments, the battery cell can comprise an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte.

[0191] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0192] In some embodiments, the battery cell further comprises a shell. In some embodiments, the ratio of the length to the width of the shell is 4 to 7, such as 4, 5, 6, 7, etc., or other non-listed values within the range of 4 to 7. In some embodiments, the length of the shell is 400 mm to 600 mm, such as 400, 450, 500, 550, 600, etc., or other non-listed values within the range of 400 mm to 600 mm. In some embodiments, the width of the shell is 90 mm to 120 mm, such as 90, 100, 110, 120, etc., or other non-listed values within the range of 90 mm to 120 mm. In some embodiments, the height of the shell is 13 mm to 25 mm, such as 13, 15, 17, 19, 21, 23, 25, etc., or other non-listed values within the range of 13 mm to 25 mm. In some embodiments, the shell is an aluminum shell, and the thickness of the aluminum shell is 0.2 mm to 0.3 mm, such as 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, etc., or other non-listed values within the range of 0.2 mm to 0.3 mm.

[0193] With the shell in the above size range, the energy density can be improved while the internal resistance of the battery is reduced, so that the energy density and fast charging performance of the battery are improved.

[0194] In some embodiments, the mass energy density of the battery cell is 210 Wh / Kg to 250 Wh / Kg.

[0195] The shape of the battery cell is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, FIG. 2 is a battery cell 5 in a square structure as an example. Optionally, the battery cell is a lithium ion battery or a sodium ion battery.

[0196] In some embodiments, referring to FIG. 3, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separator film can be wound or stacked to form an electrode assembly 52. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0197] In some embodiments, a battery device, which can be a battery module, a battery pack, an energy storage battery, etc., is provided. The above battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0198] FIG. 4 is a battery module 4 as an example. Referring to FIG. 4, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0199] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0200] In some embodiments, the above battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0201] FIGS. 5 and 6 are a battery pack 1 as an example. Referring to FIGS. 5 and 6, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0202] [Electric device]

[0203] In addition, the application also provides a power utilization device comprising at least one of the battery cell, the battery module, or the battery pack provided by the application. The battery cell, the battery module, or the battery pack can be used as a power supply of the power utilization device, and can also be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0204] As the power utilization device, the battery cell, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0205] FIG. 7 is a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the battery cell of the power utilization device, the battery pack or the battery module can be used.

[0206] In some embodiments, the power utilization device comprises a vehicle, and the length direction of the electrode assembly is arranged along the running direction of the vehicle.

[0207] As another example of the device, the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the battery cell can be used as a power supply.

[0208] Embodiments

[0209] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0210] I. Embodiments

[0211] Embodiment 1

[0212] 1) Negative electrode sheet

[0213] The negative electrode active material, the conductive agent acetylene black, the binder styrene butadiene rubber, and the thickening agent sodium carboxymethyl cellulose are included, and the mass ratio is 96.4:0.6:1.0:2.0; the thickness of the negative electrode current collector copper foil is 4.5 μm, the ratio of the single-layer thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 14.1, and the single-sided coating area density of the negative electrode sheet is 0.152 g / 1540 mm 2 The compaction density of the negative electrode sheet is 1.55 g / cm3 .

[0214] The negative active material comprises a silicon-based material and a carbon-based material, and the silicon-based material is mixed with the carbon-based material graphite so that the content of silicon element in the negative active material is 5%.

[0215] 2) Positive electrode sheet

[0216] The positive electrode active material lithium iron phosphate (LFP), the lithium supplement lithium iron oxide (Li5FeO4), the binder polyvinylidene fluoride, and the conductive agent acetylene black are in a mass ratio of 95.9:0.3:2.3:1.5; the thickness of the positive current collector aluminum foil is 10 μm, the ratio of the thickness of the single-sided positive film layer to the thickness of the positive current collector is 11.1, the single-sided coating area density of the positive electrode sheet is 0.445 g / 1540 mm 2 , and the compaction density of the positive electrode sheet is 2.55 g / cm 3 .

[0217] The positive electrode active material comprises lithium-containing phosphate particles with a longest diameter of 0.1 μm-0.3 μm and lithium-containing phosphate particles with a longest diameter of 1 μm-5 μm, and the mass ratio of the lithium-containing phosphate particles with a longest diameter of 0.1 μm-0.3 μm to the lithium-containing phosphate particles with a longest diameter of 1 μm-5 μm is 90:10.

[0218] The lithium supplement Li5FeO4 has a longest diameter of 11 μm, and the lithium supplement Li5FeO4 has a carbon coating layer with a thickness of 30 nm on the surface.

[0219] 3) Electrolyte

[0220] The electrolyte comprises DMC, EMC, DEC, and EC solvents (mass ratio 15:40:15:30), 13% of lithium hexafluorophosphate (LiPF6) relative to the total mass of the electrolyte, and 10% of fluoroethylene carbonate FEC relative to the total mass of the electrolyte. The lithium ion conductivity of the electrolyte is 11 mS / cm.

[0221] 4) Separation film

[0222] The separation film comprises a PE-based film with a thickness of 5 μm, and the film is coated on one side with a ceramic coating layer with a thickness of 2 μm, and the ceramic coating layer comprises an aluminum oxide component.

[0223] 5) Battery cell

[0224] The positive electrode sheet, the separator, and the negative electrode sheet are prepared into a laminated electrode assembly through a lamination process. The ratio of the size of the positive film layer along the length direction of the electrode assembly to the length of the electrode assembly is 93.5%, the ratio of the size of the positive film layer along the width direction of the electrode assembly to the width of the electrode assembly is 93%, and the ratio of the width of the electrode assembly tab to the width of the electrode assembly is 70%. The positive electrode tab and the negative electrode tab are located at opposite ends along the length direction of the electrode assembly. The square aluminum shell containing the electrode assembly has a length of 574 mm, a width of 120 mm, and a thickness of 17.9 mm. The aluminum shell has a shell wall thickness of 0.3 mm and is filled with electrolyte. Through packaging, standing, formation, aging, secondary packaging, capacity, and other processes, a battery monomer is obtained, wherein the electrode assembly tab is directly connected to the top cover. The energy density of the battery monomer is 221 Wh / Kg.

[0225] Examples 2-5

[0226] The battery monomer of Example 2-5 is different from Example 1 in that the mass content of silicon element in the negative electrode active material is changed (the mass of graphite is correspondingly changed), and the single-sided coating density of the positive electrode sheet and the negative electrode sheet is changed, so that the ratio of the single-sided thickness of the positive film layer to the thickness of the positive current collector and the ratio of the single-sided thickness of the negative film layer to the thickness of the negative current collector are changed with the change of the coating density. See Tables 1-3 for details.

[0227] Examples 6-9

[0228] The battery monomer of Example 6-9 is different from Example 1 in that the proportion of the carbonate solvent (dimethyl carbonate) in the electrolyte is changed, and the amount of another solvent is correspondingly increased. See Tables 1-3 for details.

[0229] Examples 10-12

[0230] The battery monomer of Example 10-12 is different from Example 1 in that the content of the lithium supplement in the positive film layer is changed. See Tables 1-3 for details.

[0231] Example 13

[0232] The battery monomer of Example 13 is different from Example 1 in that the type of the lithium supplement in the positive film layer is changed, and the lithium supplement does not have a carbon-containing coating layer on the surface. See Tables 1-3 for details.

[0233] Examples 14-15

[0234] The battery monomer of Example 14-15 is different from Example 1 in that the thickness of the carbon-containing coating layer on the surface of the lithium supplement in the positive film layer is changed. See Tables 1-3 for details.

[0235] Examples 16-18

[0236] The battery cells of Examples 16-18 differ from Example 1 in that the amount of fluoroethylene carbonate FEC in the electrolyte additive is changed, as shown in Tables 1-3.

[0237] Example 19

[0238] The battery cells of Example 19 differ from Example 1 in that the type of carbonate solvent in the electrolyte and the type of carbonate additive are changed, as shown in Tables 1-3.

[0239] Comparative Examples 1-2

[0240] Comparative Examples 1-2 differ from Example 1 in that the negative active material does not contain silicon-based materials, and thus does not contain silicon elements (the mass of the carbon-based material graphite is changed accordingly); and the single-sided coating density of the positive electrode sheet and the negative electrode sheet is changed, so that the ratio of the single-sided thickness of the positive electrode film layer to the thickness of the positive current collector and the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative current collector are changed with the change in the coating density, as shown in Tables 1-3.

[0241] Comparative Examples 3-4

[0242] Comparative Examples 3-4 differ from Example 1 in that the proportion of silicon-based materials in the negative active material is changed, so that the mass content of silicon elements is changed (the mass of the carbon-based material graphite is changed accordingly); and the single-sided coating density of the negative electrode sheet is changed, so that the ratio of the single-sided thickness of the negative electrode film layer to the thickness of the negative current collector is changed with the change in the coating density, as shown in Tables 1-3.

[0243] II. Performance Test

[0244] 1. Test method for silicon element content

[0245] After the negative electrode sheet is burned at 400°C for 2h, the negative active material powder is scraped off from the current collector, ground, and sieved through a 200-mesh sieve, and the ICP test is performed to obtain the mass proportion of silicon elements.

[0246] 2. Single-sided coating density of positive electrode sheet and negative electrode sheet

[0247] The sheet is disassembled, the residual electrolyte is treated with dimethyl carbonate solvent, the sheet is dried, and a small disc with an area of 1540mm 2 is cut and weighed as M, and the weight of the current collector with the same area is N, then the single-sided coating weight of the positive electrode sheet is (M-N) / 2.

[0248] 3. Test method for components and content of electrolyte

[0249] The types and qualities of the additives and solvents in the electrolyte can be obtained by detecting the electrolyte by methods known to those skilled in the art. For example, the composition in the electrolyte can be measured by liquid chromatography, ultraviolet spectrophotometry, ultraviolet-visible spectrophotometry, etc. Illustratively, the electrolyte is diluted to 3-10 times with acetonitrile to obtain an electrolyte diluent to be tested, and the electrolyte diluent is placed in a GC-MS 3100 organic component gas chromatograph for full-scan qualitative analysis. The injection port temperature is 250°C, and the scanning range is 35 μm-270 μm. After the test is completed, the total ion current chromatogram of each organic matter is obtained. According to the peak position of the chromatogram, the corresponding organic matter type is compared, and the content percentage of each organic matter is calculated according to the peak area.

[0250] 4. Lithium ion conductivity of the electrolyte

[0251] About 100 mL of the electrolyte sample is taken with a dry and clean corrosion-resistant sample bottle, and is placed in a constant-temperature water bath. The sample is shaken from time to time, and is heated to 25°C (deviation ±0.5°C). After the temperature of the sample is constant, the conductivity of the electrolyte is tested by using a commercially available conductivity meter. The conductivity meter is cleaned with a calibration liquid, and is then placed vertically in the liquid to be tested. The test is started by clicking, and the test result is recorded after the data is stable for more than 10 s.

[0252] 5. Observation of the morphology of the lithium supplement agent and the carbon coating layer thereof, observation of the longest diameter of the lithium supplement agent, and observation of the longest diameter of the lithium-containing phosphate in the positive electrode film layer

[0253] The prepared positive electrode film layer is tested by an electron microscope.

[0254] 6. Compaction density and film thickness of the positive electrode sheet and the negative electrode sheet under the full discharge state of the battery monomer

[0255] The battery monomer is discharged to 0% SOC by using a 0.33C discharge strategy. The full-discharged electrode sheet is disassembled, residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and the electrode sheet sample with an area of S is weighed by using an electronic balance. The weight is W, and the thickness T of the electrode sheet is measured by using a micrometer. Then, the compaction density is W / (T×S).

[0256] The thickness of the positive and negative electrode film layers can be tested by using a micrometer (for example, Mitutoyo 293-100, with a precision of 0.1 μm).

[0257] 7. Fast charging performance

[0258] Charging time test: ① Voltage calibration: 1) The positive electrode sheet, negative electrode sheet, separator and electrolyte in the example or comparative example were prepared into a stacked three-electrode battery, which was placed at 25 °C for 30 min; 2) After the battery monomer was charged to a charging cutoff voltage of 3.65 V at 25 °C and 0.33 C, constant voltage charging was continued at the charging cutoff voltage until the current was 0.05 C, and the charging was stopped (wherein C represents the rated capacity of the battery monomer); 3) 25 °C for 1 h; 4) the battery monomer was discharged to a discharge cutoff voltage of 2.5 V at 25 °C and 0.33 C, and the total discharge capacity C0 discharged by the battery monomer was recorded; 5) 25 °C for 1 h. ② Normal temperature charging test: 1) The positive electrode sheet, negative electrode sheet, separator and electrolyte in the example or comparative example were prepared into a stacked three-electrode battery, which was placed for 30 min; 2) 0.33 C0 direct current discharge to the discharge cutoff voltage of 2.5 V, which corresponds to 0% SOC at this time; 3) stand for 5 min; 4) 5C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C1 at this time, which corresponds to C1 / C0 SOC at this time; 5) stand for 5 min; 6) 4.5C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C2 at this time, which corresponds to C2 / C0 SOC at this time; 7) stand for 5 min; 8) 4C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C3 at this time, which corresponds to C3 / C0 SOC at this time; 9) stand for 5 min; 10) 3C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C4 at this time, which corresponds to C4 / C0 SOC at this time; 11) stand for 5 min; 12) 2C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C5 at this time, which corresponds to C5 / C0 SOC at this time; 13) stand for 5 min; 14) 1C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C6 at this time, which corresponds to C6 / C0 SOC at this time; 15) stand for 5 min; 16) 0.8C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C7 at this time, which corresponds to C7 / C0 SOC at this time; 17) stand for 5 min; 16) 0.5C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C8 at this time, which corresponds to C8 / C0 SOC at this time; 15) stand for 5 min; 16) 0.33C0 constant current charging to the negative electrode potential of 0 V, reading the capacity C9 (also C0) at this time, which corresponds to 100% SOC. The total charging time from 10% SOC to 80% SOC charging process is obtained by summation.

[0259] 8、mass energy density

[0260] At 25 °C, charge to 3.65 V at a charging rate of 0.33 C of the nominal capacity of the battery, then constant voltage charge to 0.05 C at 3.65 V, stand for 10 min, then discharge to 2.5 V at a discharge rate of 0.33 C, stand for 10 min, get the discharge energy E, get the mass M of the battery monomer by the balance, then the mass energy density = E / M.

[0261] 9. Cycle performance

[0262] Charged at 0.5C rate of the nominal capacity of the battery to 3.65V at 25℃, then charged at 3.65V constant voltage to 0.05C, stand for 10min, then discharged at 1C rate to 2.5V, stand for 10min, the above one charge-discharge is a cycle, until the capacity of the battery decays to 80% of the nominal capacity, stop the test, recorded as the cycle number @80%SOH.

[0263] III. Analysis of test results of each embodiment and comparative example

[0264] The battery cells of each embodiment and comparative example were prepared according to the above method, and each performance parameter was measured, and the results are shown in Table 3 below.

[0265] Table 1. Preparation parameters

[0266] Table 2. Preparation parameters

[0267] Table 3. Preparation and performance parameters

[0268] In the battery cells of Examples 1-19, the positive electrode film layer containing lithium-containing phosphate as the positive electrode active material was used, and the areal density of the single-sided positive electrode film layer was 0.35g / 15 40.25mm 2 to 0.5g / 15 40.25mm 2 ; at the same time, the negative electrode film layer containing a material containing silicon element as the negative electrode active material (the mass fraction of silicon element in the negative electrode active material was 2% to 10%) was used, and the areal density of the single-sided negative electrode film layer was 0.13g / 15 40.25mm 2 to 0.19g / 15 40.25mm 2 ; therefore, the battery cells prepared in Examples 1-13 all have excellent energy density, cycle performance and fast charging performance.

[0269] The negative electrode active material of Comparative Example 1 does not contain silicon element, and the coating areal density of the positive electrode film layer is low (the areal density of the single-sided positive electrode film layer is less than 0.35g / 15 40.25mm 2 ).

[0270] From the comparison of Comparative Example 1 and Examples 1-19, it can be seen that the negative electrode active material contains silicon element, and the areal density of the single-sided positive electrode film layer needs to be 0.35g / 15 40.25mm 2 to 0.5g / 15 40.25mm 2Only when silicon is within a certain range can the energy density of the battery be effectively improved; however, when the negative electrode active material does not contain silicon, or when the areal density of the positive electrode film is low (the areal density of a single-sided positive electrode film is less than 0.35g / 1540.25mm), the energy density of the battery can be significantly improved. 2 If the energy density of a single battery cell is not increased, then it is impossible to improve the energy density of the battery cell.

[0271] The negative electrode active material in Comparative Example 2 does not contain silicon, and the coating surface density of both the positive and negative electrode films is relatively high (the surface density of the positive electrode film on one side is higher than 0.35 g / 1540.25 mm). 2 The areal density of the single-sided negative electrode film is higher than 0.19 g / 1540.25 mm. 2 ).

[0272] A comparison of Comparative Example 2 with Examples 1-19 shows that the areal density of the single-sided positive electrode film needs to be 0.35 g / 1540.25 mm. 2 Up to 0.5g / 1540.25mm 2 Within this range, the areal density of the single-sided negative electrode film is 0.13 g / 1540.25 mm. 2 Up to 0.19g / 1540.25mm 2 Only when the energy density of the battery is improved can its cycle performance and fast charging capability be simultaneously enhanced; and when the coating surface density of the positive and negative electrode films is high (the surface density of the positive electrode film on one side is higher than 0.35g / 1540.25mm), it is possible to improve both the energy density and the cycle performance and fast charging capability. 2 The areal density of the single-sided negative electrode film is higher than 0.19 g / 1540.25 mm. 2 While this can improve the energy density of individual battery cells, it will worsen their fast-charging capability and cycle performance.

[0273] The negative electrode active material in Comparative Example 3 has a low silicon content (less than 2% by mass) and a high coating density of the negative electrode film (the surface density of the single-sided negative electrode film is higher than 0.19 g / 1540.25 mm). 2 ).

[0274] A comparison of Comparative Example 3 with Examples 1-19 shows that the silicon content in the negative electrode active material is in the range of 2% to 10%, and the areal density of the single-sided negative electrode film is 0.13 g / 1540.25 mm. 2 Up to 0.19g / 1540.25mm 2 Only when these conditions are met can the battery's energy density, fast-charging performance, and cycle performance be improved simultaneously. However, when the silicon content in the negative electrode active material is low (less than 2% by mass), even using a negative electrode film with a high surface density (a single-sided negative electrode film surface density higher than 0.19g / 1540.25mm²) will not achieve optimal performance. 2 When the battery energy density is reduced, the improvement effect is still limited, and the cycle performance and charging capacity will be deteriorated.

[0275] The negative electrode active material in Comparative Example 4 has a high silicon content (more than 10% by mass) and a low coating surface density (less than 0.13 g / 1540.25 mm² for a single-sided negative electrode film). 2 ).

[0276] A comparison of Comparative Example 4 with Examples 1-19 shows that the silicon content in the negative electrode active material is in the range of 2% to 10%, and the areal density of the single-sided negative electrode film is 0.13 g / 1540.25 mm. 2 Up to 0.19g / 1540.25mm 2 Only when this is achieved can the battery's energy density, fast-charging performance, and cycle performance be improved simultaneously. However, when the silicon content in the negative electrode active material is high (greater than 10% by mass), even with a negative electrode film layer having a low surface density (less than 0.13g / 1540.25mm² on one side), the battery's performance will be significantly improved. 2 While this can improve battery energy density, it will still severely degrade cycle performance.

[0277] The areal densities of the positive electrode films used in Examples 1-5 were 0.445 g / 1540.25 mm, respectively. 2 0.35g / 1540.25mm 2 0.5g / 1540.25mm 2 The areal density of the negative electrode film is 0.152 g / 1540.25 mm. 2 0.142g / 1540.25mm 2 0.136g / 1540.25mm 2 0.18g / 1540.25mm 2 0.148g / 1540.25mm 2 The mass percentage of silicon in the negative electrode active material is 5%, 2%, 10%, 4%, and 8%, and the battery cells prepared from it can achieve excellent energy density, fast charging performance, and cycle performance.

[0278] In Examples 1 and 6-9, the carbonate solvent (e.g., dimethyl carbonate) constituted 4% to 20% of the electrolyte by mass, resulting in battery cells that achieved excellent energy density, fast-charging performance, and cycle performance. Furthermore, the results showed that increasing the amount of carbonate solvent further improved the battery's cycle performance; however, when the mass percentage in the electrolyte exceeded 20%, such as 25% in Example 7, the cycle performance actually decreased to some extent. Therefore, a carbonate solvent (e.g., dimethyl carbonate) content of 4% to 20% in the electrolyte can further improve the battery's cycle performance while maintaining good energy density, fast-charging performance, and cycle performance.

[0279] In Examples 1 and 10-12, the mass percentage of the lithium replenishment material in the positive electrode film layer was 0.2% to 2%, and the prepared battery cells achieved excellent energy density, fast charging performance, and cycle performance. The results also showed that as the mass percentage of the lithium replenishment material gradually increased, the battery cycle performance was further improved. However, when the mass percentage in the positive electrode film layer exceeded 2%, such as 2.5% in Example 12, the energy density decreased to some extent. Therefore, when the mass percentage of the lithium replenishment material in the positive electrode film layer was 0.2% to 2%, it was possible to improve both the energy density and the battery cycle performance.

[0280] In Examples 1 and 13, a variety of lithium-replenishing materials (such as lithium iron phosphate and lithium nickel oxide) were used in the positive electrode film layer, and the battery cells prepared therefrom can achieve excellent energy density, fast charging performance and cycle performance.

[0281] In Examples 1 to 19, the longest diameter of the lithium replenishment material in the positive electrode film layer is 5 μm to 20 μm, as shown in Figure 1. The position indicated by label 6 is the lithium replenishment material particle with a longest diameter of about 7.5 μm. Therefore, the battery cell prepared by it can take into account excellent energy density, fast charging performance and cycle performance.

[0282] In Examples 1 and 14-15, the surface of the lithium replenishing material in the positive electrode film has carbon-containing coatings of various thicknesses, as shown in Figure 1. The position indicated by label 61 is the carbon-containing coating, and there is a spacer layer between the carbon-containing coating and the lithium replenishing agent (as shown by label 62 in Figure 1). The spacer layer facilitates full contact between the lithium replenishing material and the electrolyte, thereby achieving effective lithium replenishment and further improving the energy density of the battery. Therefore, the battery cells prepared by this method can achieve excellent energy density, fast charging performance, and cycle performance.

[0283] In Examples 1-19, the lithium phosphate in the positive electrode film layer is arranged in a combination of large and small particle sizes, as shown in Figure 1. The position indicated by label 7 represents lithium iron phosphate particles with a longest diameter of 1μm-5μm, and the position indicated by label 8 represents lithium iron phosphate particles with a longest diameter of 0.1μm-0.3μm. This combination of large and small particle sizes increases the compaction density of the electrode, further improving the battery energy density. Furthermore, using the aforementioned particle size range ensures that the compaction density of the electrode is within a suitable range, thereby further improving energy density and cycle performance. In addition, when the positive electrode active material with the combined large and small particle sizes is used in conjunction with the electrolyte in this application, it can further avoid the electrolyte wetting problem caused by high compaction density electrodes, comprehensively improving battery performance.

[0284] In Examples 1 and 16-18, the carbonate additive (e.g., fluoroethylene carbonate) in the electrolyte accounts for 5% to 30% of the electrolyte by mass. The resulting battery cells exhibit excellent energy density, fast-charging performance, and cycle performance. Specifically, in Examples 1 and 11, the carbonate additive accounts for 10% and 15% of the electrolyte by mass, respectively, with cycle performances of 1850 and 1810. In Examples 10 and 12, the carbonate additive accounts for 5% and 30% of the electrolyte by mass, respectively, with cycle performances of 1740 and 1720. These results demonstrate that a carbonate additive mass percentage of 10% to 15% significantly improves cycle performance; while excessively high or low percentages still offer some improvement, their effect is limited.

[0285] In Examples 1 and 19, various carbonate additives (such as fluoroethylene carbonate and vinylene carbonate) or various carbonate solvents (such as dimethyl carbonate and ethyl methyl carbonate) were used in the electrolyte, and the prepared battery cells could achieve excellent energy density, fast charging performance and cycle performance.

[0286] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized by, The battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator film arranged between the positive electrode sheet and the negative electrode sheet, The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises lithium-containing phosphate, and the areal density of one side of the positive electrode film layer is 0.35 g / 15 40.25 mm 2 to 0.5 g / 15 40.25 mm 2 ; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one side surface of the negative electrode current collector, the areal density of the negative electrode film layer on one side is 0.13 g / 1540.25 mm 2 to 0.19 g / 1540.25 mm 2 The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a material containing silicon elements, the proportion of the silicon elements based on the mass of the negative electrode active material is 2% to 10%.

2. The battery cell of claim 1, wherein, The silicon element accounts for 4% to 8% of the mass of the negative electrode active material.

3. The battery cell according to claim 1 or 2, characterized in that, The negative electrode active material comprises a silicon-based material and a carbon-based material, The silicon-based material comprises one or more of silicon-carbon composite, silicon oxide compound; and / or The carbon-based material comprises one or more of artificial graphite and natural graphite.

4. The battery cell of any one of claims 1-3, wherein, The battery cell further comprises an electrolyte, the electrolyte comprising an organic solvent, the organic solvent comprising a carbonate solvent, the carbonate solvent comprising one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate.

5. The battery cell of claim 4, wherein, The organic solvent comprises dimethyl carbonate, and the mass fraction of the dimethyl carbonate in the total mass of the electrolyte is 4% to 20%.

6. The battery cell of claim 4, wherein, The organic solvent comprises dimethyl carbonate, and the mass fraction of the dimethyl carbonate in the total mass of the electrolyte is 8% to 16%.

7. The battery cell of any one of claims 1-6, wherein, The electrolyte further comprises an additive, and the additive comprises a carbonate additive; The carbonate additive comprises one or more of fluoroethylene carbonate, vinylene carbonate, and 1,3-propane sultone.

8. The battery cell of claim 7, wherein, The additive comprises fluoroethylene carbonate, and the mass fraction of the fluoroethylene carbonate in the total mass of the electrolyte is 5% to 30%.

9. The battery cell of claim 7, wherein, The additive comprises fluoroethylene carbonate, and the mass fraction of the fluoroethylene carbonate in the total mass of the electrolyte is 5% to 15%.

10. The battery cell of any one of claims 4-9, wherein, The conductivity of the electrolyte is 9 mS / cm to 14 mS / cm.

11. The battery cell of any one of claims 1-10, wherein, In a cross section of the positive electrode film layer along the thickness direction, the lithium-containing phosphate comprises lithium-containing phosphate particles with a longest diameter of 1 μm to 5 μm and lithium-containing phosphate particles with a longest diameter of 0.1 μm to 0.3 μm.

12. The battery cell of any one of claims 1-11, wherein, The lithium-containing phosphate has a general formula as shown in Formula I, Li x A y Me a M b P 1-c X c Y z Formula I, wherein 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A comprises one or more of Na, K, and Mg; Me comprises one or more of Mn, Fe, Co, and Ni; M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X comprises one or more of S, Si, Cl, B, C, and N; and Y comprises one or more of O and F.

13. The battery cell of any one of claims 1-12, wherein, The positive electrode film layer comprises a lithium supplement material, and the lithium supplement material comprises one or more of a ternary material, lithium phosphate, lithium ferrite, lithium nickelate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metavanadate, lithium tartrate, and trilithium citrate.

14. The battery cell of claim 13, wherein, At least part of the surface of the lithium supplement material has a coating layer.

15. The battery cell of claim 14, wherein, The coating layer comprises a carbon-containing coating layer, and the thickness of the carbon-containing coating layer is 10 nm to 200 nm.

16. The battery cell of claim 14, wherein, The lithium supplement material and the carbon-containing coating layer have a gap therebetween, and the width of the gap is 5 nm to 50 nm.

17. The battery cell of any one of claims 13-16, wherein, The longest diameter of the lithium supplement material is 5 μm to 20 μm.

18. The battery cell of any one of claims 13-16, wherein, The longest diameter of the lithium supplement material is 6 μm to 12 μm.

19. The battery cell of any one of claims 13-18, wherein, The mass percentage of the lithium supplement material is 0.2% to 2% based on the total mass of the positive electrode film layer.

20. The battery cell of claim 19, wherein, The mass percentage of the lithium supplement material is 0.1% to 1% based on the total mass of the positive electrode film layer.

21. The battery cell of any one of claims 1-20, wherein, The compacted density of the positive electrode plate is 2.45 g / cm 3 to 2.65 g / cm 3 .

22. The battery cell of any one of claims 1-21, wherein, The thickness of the positive electrode current collector is 10 μm to 15 μm.

23. The battery cell of claim 22, wherein, The thickness of the positive electrode current collector is 10 μm to 13 μm.

24. The battery cell of claim 22 or 23, wherein, The ratio of the single-side thickness of the positive electrode film layer to the thickness of the positive electrode current collector is greater than 8 and less than 20.

25. The battery cell of claim 22 or 23, wherein, The ratio of the single-side thickness of the positive electrode film layer to the thickness of the positive electrode current collector is 11 to 14.

26. The battery cell of any one of claims 1-25, wherein, The compacted density of the negative electrode sheet is 1.4 g / cm 3 to 1.6 g / cm 3 .

27. The battery cell of any one of claims 1-26, wherein, The thickness of the negative electrode current collector is 4 μm to 6 μm.

28. The battery cell of claim 27, wherein, The thickness of the negative electrode current collector is 4 μm to 5.5 μm.

29. The battery cell of claim 27 or 28, wherein, The ratio of the single-side thickness of the negative electrode film layer to the thickness of the negative electrode current collector is greater than 11 and less than 20.

30. The battery cell of claim 27 or 28, wherein, The ratio of the single-side thickness of the negative electrode film layer to the thickness of the negative electrode current collector is 12 to 18.

31. The battery cell of any one of claims 1-30, wherein, The separator film comprises a substrate and a ceramic coating layer arranged at least on one side close to the positive electrode tab.

32. The battery cell of claim 31, wherein, The substrate comprises one or more of a polypropylene film, a polyethylene film, and a polyimide film.

33. The battery cell of claim 32, wherein, The substrate comprises a polypropylene film, and the thickness of the polypropylene film is 9 μm to 14 μm; and / or The substrate comprises a polyethylene film, and the thickness of the polyethylene film is 5 μm to 8 μm. The thickness of the ceramic coating layer is 1 μm to 3 μm.

34. The battery cell of any one of claims 31-33, wherein, The battery cell comprises an electrode assembly, the electrode assembly comprising a positive electrode tab, a separator film, and a negative electrode tab arranged in sequence, 35. The battery cell of any one of claims 1-34, wherein, The ratio of the size of the positive electrode film layer along the length direction of the electrode assembly to the size of the electrode assembly along the length direction of the electrode assembly is 92-95%. The ratio of the size of the positive electrode film layer along the width direction of the electrode assembly to the size of the electrode assembly along the width direction of the electrode assembly is 92-96%. The positive electrode tab comprises a positive electrode ear, and the negative electrode tab comprises a negative electrode ear.

36. The battery cell of any one of claims 1-35, wherein, The positive electrode ear extends out along a first direction of the positive electrode tab, and the ratio of the width of the positive electrode ear to the width of the positive electrode tab in a second direction of the positive electrode tab is 50%-100%, the second direction being perpendicular to the first direction. The battery cell further comprises a top cover, and the top cover is provided with an electrode terminal for directly connecting with the positive electrode ear and / or the negative electrode ear.

37. The battery cell of claim 36, wherein, The battery cell further comprises a shell, and the shell is an aluminum shell, and the thickness of the aluminum shell is 0.2 mm to 0.3 mm.

38. The battery cell of any one of claims 1-36, wherein, The ratio of the length to the width of the shell is 4 to 7.

39. The battery cell of claim 38, wherein, The length of the shell is 400 mm to 600 mm, the width is 90 mm to 120 mm, and the height is 13 mm to 25 mm.

40. The battery cell of either claim 38 or 39, wherein, The mass energy density of the battery cell is 210 Wh / Kg to 250 Wh / Kg.

41. The battery cell of any one of claims 1-40, wherein, ​ 42. A battery device, comprising: The battery device is at least one of a battery module, a battery pack, an energy storage battery.

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

44. The powered device of claim 43, wherein, The electric device includes a vehicle, and a length direction of the electrode assembly is placed along a traveling direction of the vehicle.

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