Battery monomer and power utilization device

Abstract

The invention provides a battery monomer and a power utilization device, the battery monomer comprises a positive pole piece, a negative pole piece and an isolating membrane arranged between the positive pole piece and the negative pole piece, the positive pole piece comprises a positive current collector and a positive membrane layer arranged on at least one side surface of the positive current collector, and the negative pole piece comprises a negative current collector and a negative membrane layer arranged on at least one side surface of the negative current collector. The positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises lithium-containing phosphate, and the surface density of a single side of the positive electrode film layer is 0.35 g / 1540.25 mm < 2 > to 0.5 g / 1540.25 mm < 2 >; the negative electrode plate 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, and the surface density of the single-sided negative electrode film layer is 0.13 g / 1540.25 mm < 2 > to 0.19 g / 1540.25 mm < 2 >; the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises a silicon element-containing material, and the silicon element accounts for 2%-10% of the mass of the negative electrode active material.

Description

Battery cells and electrical devices

[0001] Cross-references

[0002] This application incorporates, in its entirety, PCT / CN2024 / 109591, International Patent Application No. PCT / CN2024 / 109591, entitled “Battery Cell and Electrical Device,” filed on August 2, 2024, which is hereby incorporated by reference. Technical Field

[0003] This application relates to the field of battery cell technology, and in particular to a battery cell and an electrical device. Background Technology

[0004] In recent years, battery cells have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. With the increasing application of battery cells, higher requirements are being placed on their power performance, cycle performance, and service life.

[0005] Summary of the Invention

[0006] This application is made in view of the above-mentioned issues, and its purpose is to provide a novel battery cell with high energy density, while also taking into account excellent fast charging performance and cycle performance.

[0007] To achieve the above objectives, a first aspect of this application provides a battery cell, comprising a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium phosphate-containing material. The areal density of the single-sided positive electrode film layer is 0.35 g / 1540.25 mm². 2 Up to 0.5g / 1540.25mm 2 The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, wherein the areal density of the single-sided negative electrode film layer is 0.13 g / 1540.25 mm. 2 Up to 0.19g / 1540.25mm 2 The negative electrode film layer includes a negative electrode active material, which includes silicon-containing materials, with the silicon content of the negative electrode active material ranging from 2% to 10% by mass.

[0008] In the battery cell provided in this application, the positive electrode film layer uses lithium phosphate with an areal density within the above-mentioned range, which can effectively improve the problem of low energy density when lithium phosphate is used as a positive electrode active material, and can maintain the basic charging capacity of the battery, thus improving both the energy density and charging performance of the battery. At the same time, the negative electrode film layer uses a negative electrode active material containing silicon elements within the above-mentioned range, which can effectively increase the specific capacity of the negative electrode. When it also uses an areal density within the above-mentioned range, it can also improve the fast charging performance of the battery.

[0009] Furthermore, by combining the aforementioned positive electrode film and the aforementioned negative electrode film at an appropriate areal density ratio, the lithium plating problem can be effectively improved, resulting in higher energy density, better charging capability, and superior cycle performance for the battery cell, thus comprehensively improving battery performance.

[0010] In any embodiment, silicon accounts for 4% to 8% of the mass of the anode active material.

[0011] When the negative electrode film layer uses a negative electrode active material containing silicon elements within the above range, it can further improve the energy density and charging performance of the battery.

[0012] In any embodiment, the negative electrode active material includes silicon-based materials and carbon-based materials, wherein the silicon-based materials include one or more of silicon-carbon composites and silicon oxides; and / or, the carbon-based materials include one or more of artificial graphite and natural graphite.

[0013] When graphite-based carbon materials are used as anode active materials, they exhibit good electrochemical performance, long cycle life, and low cost. When silicon-based materials are used together with graphite-based carbon materials, the specific capacity of the anode active material can be further improved.

[0014] In any embodiment, the battery cell further includes an electrolyte, which includes an organic solvent, said organic solvent including a carbonate solvent, which includes one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0015] When the above-mentioned type of carbonate solvent is used in the electrolyte, the wetting problem of the positive and negative electrode sheets in the electrolyte can be further improved; when combined with the above-mentioned positive and negative electrode film layers with high areal density, the wetting problem of the electrode sheets in the electrolyte caused by high areal density can be further avoided, thus comprehensively improving the performance of the battery.

[0016] In any embodiment, the organic solvent includes dimethyl carbonate, which accounts for 4% to 20% of the total mass of the electrolyte.

[0017] In any embodiment, the organic solvent includes dimethyl carbonate, which accounts for 8% to 16% of the total mass of the electrolyte.

[0018] When dimethyl carbonate within the above-mentioned ratio range is used as an electrolyte solvent, it can improve wetting issues while also improving gas production, thus comprehensively improving the battery's cycle performance.

[0019] In any embodiment, the electrolyte further comprises an additive, which includes a carbonate additive; the carbonate additive includes one or more of fluoroethylene carbonate, vinylene carbonate, and 1,3-propanesulfonate lactone.

[0020] When the above-mentioned type of carbonate additive is used in the electrolyte, an SEI film can be formed on the surface of the silicon-containing anode. This SEI film can cover the electrode surface to reduce the degree of electrode exposure to the electrolyte, reduce side reactions and gas generation on the surface of the silicon-containing anode, and further improve the cycle performance of the battery.

[0021] In any embodiment, the additive includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate in the electrolyte is 5% to 30% based on the total mass of the electrolyte.

[0022] In any embodiment, the additive includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate in the electrolyte is 5% to 15% based on the total mass of the electrolyte.

[0023] Using fluoroethylene carbonate within the above-mentioned ratio range as an electrolyte solvent can further improve the side reactions and gas generation problems on the silicon-containing anode surface, thereby further improving the cycle performance of the battery.

[0024] In any embodiment, the conductivity of the electrolyte is from 9 mS / cm to 14 mS / cm.

[0025] The battery cell provided in this application has a conductivity within the above-mentioned range, and therefore has good electrochemical performance.

[0026] In any embodiment, in a cross-section along the thickness direction of the positive electrode film, the lithium phosphate includes lithium phosphate particles with a longest diameter of 1 μm to 5 μm and lithium phosphate particles with a longest diameter of 0.1 μm to 0.3 μm.

[0027] When lithium phosphate in the positive electrode film is used in a combination of large and small particle sizes, the compaction density of the electrode can be increased, thereby further improving the energy density of the battery. When the particle size is combined in the range mentioned above, the compaction density of the electrode can be kept within a suitable range, thus balancing the improvement of energy density and cycle performance.

[0028] Meanwhile, when positive electrode active materials with different particle sizes are combined with the electrolyte provided in this application, the electrolyte wetting problem caused by high-density electrodes can be further avoided, thus comprehensively improving battery performance.

[0029] In any embodiment, the general formula for lithium phosphate is shown in Formula I.

[0030] Li x A y Me a M b P 1-c X c Y z Formula I,

[0031] Wherein, 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0032] When lithium phosphates of the above type are used as positive electrode active materials, the battery exhibits good energy density and cycle performance.

[0033] In any embodiment, the positive electrode film layer includes a lithium replenishing material, which includes one or more of the following: ternary materials, lithium phosphate, lithium ferrite, lithium nickel oxide, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, and lithium trilithium citrate.

[0034] When using lithium-containing phosphates as the positive electrode active material, the application of the above-mentioned lithium supplementation materials can further improve the specific capacity of the positive electrode active material.

[0035] In any embodiment, at least a portion of the surface of the lithium replenishing material has a coating layer.

[0036] In any embodiment, the coating layer includes a carbon-containing coating layer with a thickness of 10 nm to 200 nm.

[0037] Carbon coating on the surface of the lithium replenishing material can effectively protect the core lithium replenishing material. The carbon-coated lithium replenishing material has a stable structure, which can alleviate the strong side reaction between the electrolyte and the lithium replenishing material, thereby further improving the energy density and cycle performance of the battery. On the other hand, it can also increase the conductivity of the lithium replenishing agent, lower the delithiation potential, reduce the voltage during the formation stage, and alleviate the adverse effects of high voltage on the decomposition of electrolyte components.

[0038] In any embodiment, there is a gap between the lithium replenishing material and the carbon-containing coating layer, the width of which is 5 nm to 50 nm.

[0039] When there is a gap between the lithium replenishing material and its surface carbon coating layer, it is beneficial for the lithium replenishing material to have sufficient contact with the electrolyte, thereby achieving an effective lithium replenishment effect and further improving the energy density of the battery.

[0040] In any embodiment, the longest diameter of the lithium replenishment material is 5 μm to 20 μm.

[0041] In any embodiment, the longest diameter of the lithium replenishment material is 6 μm to 12 μm.

[0042] In any implementation, the mass percentage of the lithium replenishment material is 0.2% to 2% based on the total mass of the positive electrode film.

[0043] In any embodiment, the mass percentage of the lithium replenishment material is 0.1% to 1% based on the total mass of the positive electrode film.

[0044] When lithium replenishment materials with the above-mentioned particle size and proportion range are used, the stability of the lithium replenishment materials can be effectively improved while also having a good lithium replenishment effect.

[0045] In any embodiment, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.65 g / cm 3 .

[0046] The positive electrode sheet provided in this application has a compaction density within the above-mentioned range, and therefore has a better energy density.

[0047] In any embodiment, the thickness of the positive current collector is 10 μm to 15 μm.

[0048] In any embodiment, the thickness of the positive current collector is 10 μm to 13 μm.

[0049] Positive current collectors with the aforementioned thickness range can further improve energy density.

[0050] In any embodiment, the ratio of the one-sided thickness of the positive electrode film to the thickness of the positive electrode current collector is greater than 8 and less than 20.

[0051] In any embodiment, the ratio of the one-sided thickness of the positive electrode film to the thickness of the positive electrode current collector is 11 to 14.

[0052] When positive electrode films of the above thickness range are used in combination with positive electrode current collectors, energy density and charging performance can be further balanced, and battery performance can be comprehensively improved.

[0053] In any embodiment, the compaction density of the negative electrode sheet is 1.4 g / cm³. 3 Up to 1.6 g / cm 3 .

[0054] The negative electrode sheet provided in this application has a compaction density within the above-mentioned range, and therefore has a better energy density.

[0055] In any embodiment, the thickness of the negative electrode current collector is 4 μm to 6 μm.

[0056] In any embodiment, the thickness of the negative electrode current collector is 4 μm to 5.5 μm.

[0057] Anode current collectors with the aforementioned thickness range can further improve energy density.

[0058] In any embodiment, the ratio of the one-sided thickness of the negative electrode film to the thickness of the negative electrode current collector is greater than 11 and less than 20.

[0059] In any embodiment, the ratio of the thickness of the negative electrode film to the thickness of the negative electrode current collector is 12 to 18.

[0060] When negative electrode films of the aforementioned thickness range are combined with negative electrode current collectors, energy density and charging performance can be further balanced, thus comprehensively improving battery performance.

[0061] In any embodiment, the separator includes a substrate and a ceramic coating disposed at least on the side close to the positive electrode.

[0062] Applying a ceramic coating to the substrate surface can improve its thermal safety; and since the voltage is higher on the side closer to the positive electrode, applying a ceramic coating on that side can further improve its oxidation resistance.

[0063] In any embodiment, the substrate includes one or more of polypropylene film, polyethylene film, and polyimide film.

[0064] In any embodiment, the substrate comprises a polypropylene film with a thickness of 9 μm to 14 μm; and / or the substrate comprises a polyethylene film with a thickness of 5 μm to 8 μm.

[0065] In any embodiment, the thickness of the ceramic coating is from 1 μm to 3 μm.

[0066] When a substrate with the thickness range mentioned above is used in combination with a ceramic coating, it is possible to improve its thermal safety, while also taking into account its ion permeability and reducing its internal resistance.

[0067] In any embodiment, the battery cell includes an electrode assembly, which includes a positive electrode, a separator, and a negative electrode stacked sequentially. The ratio of the dimension of the positive electrode film layer along the length of the electrode assembly to the dimension of the electrode assembly along the length of the electrode assembly is 92% to 95%; the ratio of the dimension of the positive electrode film layer along the width of the electrode assembly to the dimension of the electrode assembly along the width of the electrode assembly is greater than or equal to 92% to 96%.

[0068] When the battery cell provided in this application uses the above-mentioned stacked cells, the energy density of the battery can be further improved.

[0069] In any embodiment, the positive electrode includes a positive tab and the negative electrode includes a negative tab; the positive tab extends along a first direction of the positive electrode, and in a second direction of the positive electrode, the ratio of the width of the positive tab to the width of the positive electrode is 50% to 100%, and the second direction is perpendicular to the first direction.

[0070] When the battery cell provided in this application uses the electrode with the above-mentioned width range and structural features, the charging temperature rise of the battery can be further improved.

[0071] In any embodiment, the battery cell also includes a top cover, which is provided with electrode terminals for direct connection to the positive and / or negative tabs.

[0072] Conventional batteries require adapter plates to connect the electrode terminals and tabs, which reduces the utilization rate of the electrode assembly and lowers the battery energy density. When the battery cell provided in this application adopts the above structure, eliminating the need for adapter plates effectively solves this problem, reduces the battery's internal resistance, and further improves both battery energy density and fast-charging performance.

[0073] In any embodiment, the battery cell further includes a housing, which is an aluminum housing with a thickness of 0.2 mm to 0.3 mm.

[0074] In any embodiment, the length-to-width ratio of the housing is 4 to 7.

[0075] In any embodiment, the length of the housing is 400 mm to 600 mm, the width is 90 mm to 120 mm, and the height is 13 mm to 25 mm.

[0076] Using a casing within the aforementioned size range allows for both increased energy density and reduced battery internal resistance, thereby improving both battery energy density and fast charging performance.

[0077] In any embodiment, the mass energy density of the battery cell is from 210Wh / Kg to 250Wh / Kg.

[0078] A second aspect of this application also provides an electrical device, including a battery cell from the first aspect of this application.

[0079] In any embodiment, the electrical device includes a vehicle, and the electrode assembly is positioned along the length direction of the vehicle's travel direction. Attached Figure Description

[0080] Figure 1 is an electron microscope observation of the positive electrode film obtained according to an embodiment of this application; wherein, 6 represents the lithium replenishing material, 61 represents the carbon coating layer on the surface of the lithium replenishing material, 62 represents the gap between the lithium replenishing material and the carbon coating layer, 7 represents lithium phosphate particles with a longest diameter of 1-5 μm, and 8 represents lithium phosphate particles with a longest diameter of 0.1-0.3 μm.

[0081] Figure 2 is a schematic diagram of a battery cell according to an embodiment of this application;

[0082] Figure 3 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 2;

[0083] Figure 4 is a schematic diagram of a battery module according to an embodiment of this application;

[0084] Figure 5 is a schematic diagram of a battery pack according to an embodiment of this application;

[0085] Figure 6 is an exploded view of the battery pack of one embodiment of this application shown in Figure 5;

[0086] Figure 7 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0087] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0088] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell and power supply device of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0089] 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.

[0090] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0091] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0092] 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.

[0093] 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.

[0094] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0095] When lithium phosphates are used as positive electrode active materials, such as lithium iron phosphate, they often suffer from low specific capacity. Conventional negative electrode active materials, such as graphite, also suffer from low specific capacity. Thick coatings on both positive and negative electrode sheets can improve the energy density of a single battery cell to some extent, but thick coatings also make it difficult for the electrodes to be fully wetted in the electrolyte, thus deteriorating the battery's kinetic and cycle performance.

[0096] To address the aforementioned issues, this application provides a battery cell comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrode.

[0097] [Positive electrode plate]

[0098] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0099] In some embodiments, the areal density of the positive electrode film layer on one side is 0.35 g / 1540.25 mm². 2 Up to 0.5g / 1540.25mm 2 For example, 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 0.35g / 1540.25mm 2 Up to 0.5g / 1540.25mm 2 Other values ​​not listed within the range.

[0100] In the battery cell provided in this application, the positive electrode film layer uses lithium phosphate with an areal density within the above range, which can effectively improve the problem of low energy density when lithium phosphate is used as a positive electrode active material, and can maintain the basic charging capacity of the battery, thus improving both the energy density and charging performance of the battery.

[0101] In this document, the "area density" of the positive or negative electrode film has a meaning known in the art and can be tested using methods known in the art. For example, take a negative electrode sheet that is coated on one side and cold-pressed (if it is a double-sided coated negative electrode sheet, the negative electrode film on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the negative electrode film of the weighed negative electrode sheet, weigh the negative current collector, and record it as M0. The area density of the negative electrode film = (weight of the negative electrode sheet M1 - weight of the negative current collector M0) / S1. To ensure the accuracy of the test results, multiple sets (e.g., 10 sets) of samples can be tested, and the average value can be calculated as the test result.

[0102] In some embodiments, the positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate.

[0103] In some embodiments, the general formula of the lithium phosphate is shown in Formula I.

[0104] Li x A y Me a M b P 1-c X c Y z Formula I,

[0105] Wherein, 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0106] When lithium phosphates of the above type are used as positive electrode active materials, the battery exhibits good energy density and cycle performance.

[0107] When used herein, "the general formula of the lithium phosphate is as shown in Formula I" is not limited to the substances represented by the general molecular formula, but also includes other substances formed by further appropriate modifications based on the general molecular formula, which are not limited herein. The use of "general formula" is for ease of description only and is not intended to limit this application. It is understood that new materials or substances obtained by appropriate modifications based on the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modifications refer to acceptable modification methods for positive electrode active materials, and non-limiting examples include coating modification.

[0108] In some embodiments, in a cross-section along the thickness direction of the positive electrode film, the lithium phosphate includes lithium phosphate particles with a longest diameter of 1 μm to 5 μm and lithium phosphate particles with a longest diameter of 0.1 μm to 0.3 μm. In some embodiments, the lithium phosphate particles with a longest diameter of 1 μm to 5 μm may be, for example, 1, 1.5, 2, 2.5, 3, 5, etc., or other unlisted values ​​within the range of 1 μm to 5 μm. In some embodiments, the lithium phosphate particles with a longest diameter of 0.1 μm to 0.3 μm may be, for example, 0.1, 0.15, 0.2, 0.25, 0.3, etc., or other unlisted values ​​within the range of 0.1 μm to 0.3 μm.

[0109] When lithium phosphate in the positive electrode film is used in a combination of large and small particle sizes, the compaction density of the electrode can be increased, thereby further improving the energy density of the battery. When the particle size is combined in the range mentioned above, the compaction density of the electrode can be kept within a suitable range, thus balancing the improvement of energy density and cycle performance.

[0110] Meanwhile, when positive electrode active materials with different particle sizes are combined with the electrolyte provided in this application, the electrolyte wetting problem caused by high-density electrodes can be further avoided, thus comprehensively improving battery performance.

[0111] In some implementations, "longest diameter" refers to: cutting the positive electrode sheet, which includes lithium phosphate particles, along the thickness direction to expose the longitudinal section of the positive electrode film; and determining the longest diameter of the lithium phosphate particles by scanning electron microscopy (SEM) of the longitudinal section of the positive electrode film. Specifically, the "longest diameter" of the lithium phosphate particles refers to the longest straight line passing through the center point of the lithium phosphate particle and extending to the outer periphery of the particle.

[0112] In some embodiments, the positive electrode film layer further includes a lithium replenishing material, which includes one or more of the following: ternary materials, lithium phosphate, lithium ferrite, lithium nickel oxide, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, and lithium trilithium citrate.

[0113] When using lithium-containing phosphates as the positive electrode active material, the application of the above-mentioned lithium supplementation materials can further improve the specific capacity of the positive electrode active material.

[0114] In some embodiments, at least a portion of the surface of the lithium replenishing material has a coating layer.

[0115] In some embodiments, the coating layer includes a carbon-containing coating layer with a thickness of 10 nm to 200 nm, such as 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, etc., or other unlisted values ​​within the range of 10 nm to 200 nm.

[0116] Carbon coating on the surface of the lithium replenishment material can effectively protect the core lithium replenishment material. The carbon-coated lithium replenishment material has a stable structure, avoiding strong side reactions between the electrolyte and the lithium replenishment material, thereby further improving the energy density and cycle performance of the battery.

[0117] In some embodiments, there is a gap between the lithium replenishing material and the carbon-containing coating layer, the width of which is 5nm to 50nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc., or other unlisted values ​​in the range of 5nm to 50nm.

[0118] When there is a gap between the lithium replenishing material and its surface carbon coating layer, it is beneficial for the lithium replenishing material to have sufficient contact with the electrolyte, thereby achieving an effective lithium replenishment effect and further improving the energy density of the battery.

[0119] In some embodiments, the longest diameter of the lithium replenishing material is 5 μm to 20 μm, such as 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, etc., or other unlisted values ​​in the range of 5 μm to 20 μm.

[0120] In some embodiments, the longest diameter of the lithium replenishing material is 6 μm to 12 μm.

[0121] In some implementations, "longest diameter" refers to: cutting the positive electrode sheet, which includes lithium-containing material particles, along the thickness direction to expose the longitudinal section of the positive electrode film; and determining the longest diameter of the lithium-containing material particles by scanning electron microscopy (SEM) testing of the longitudinal section of the positive electrode film. Specifically, the "longest diameter" of the lithium-containing material particles refers to the longest straight line passing through the center point of the lithium-containing material particles and extending to the outer periphery of the particles.

[0122] In some embodiments, the mass percentage of the lithium replenishment material is 0.2% to 2% based on the total mass of the positive electrode film, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or other unlisted values ​​within the range of 0.2% to 2%.

[0123] In some embodiments, the mass percentage of the lithium replenishment material is 0.1% to 1% based on the total mass of the positive electrode film.

[0124] When lithium replenishment materials with the above-mentioned particle size and proportion range are used, the stability of the lithium replenishment materials can be effectively improved while also having a good lithium replenishment effect.

[0125] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. An example of a metal material may be at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymeric material substrate may be at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0126] In some embodiments, the thickness of the positive current collector is 10 μm to 15 μm, such as 10, 11, 12, 13, 14, 15, etc., or other unlisted values ​​within the range of 10 μm to 15 μm. In some embodiments, the thickness of the positive current collector is 10 μm to 13 μm.

[0127] Positive current collectors with the aforementioned thickness range can further improve energy density.

[0128] In some embodiments, the ratio of the one-sided thickness of the positive electrode film to the thickness of the positive electrode 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, etc., or other unlisted values ​​within the range of greater than 8 and less than 20. In some embodiments, the ratio of the one-sided thickness of the positive electrode film to the thickness of the positive electrode current collector is 11 to 14.

[0129] When positive electrode films of the above thickness range are used in combination with positive electrode current collectors, energy density and charging performance can be further balanced, and battery performance can be comprehensively improved.

[0130] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0131] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0132] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0133] In some embodiments, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.65 g / cm 3 For example, 2.45, 2.50, 2.55, 2.60, 2.65, etc., or 2.45 g / cm³. 3 Up to 2.65 g / cm 3 Other values ​​not listed within the range.

[0134] The positive electrode sheet provided in this application has a compaction density within the above-mentioned range, and therefore has a good specific capacity.

[0135] When used in this article, the "compacted density" of the electrode is: compacted density = areal density / (electrode thickness - current collector thickness), and its determination method can be found in GB / T24533-2009.

[0136] [Negative electrode plate]

[0137] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising a negative electrode active material. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the opposite surfaces of the negative current collector.

[0138] In some embodiments, the areal density of the negative electrode film layer on one side is 0.13 g / 1540.25 mm. 2 Up to 0.19g / 1540.25mm 2 For example, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, etc., or 0.13g / 1540.25mm 2 Up to 0.19g / 1540.25mm 2 Other values ​​not listed within the range.

[0139] In some embodiments, the negative electrode film layer includes a negative electrode active material, which includes a silicon-containing material.

[0140] In the battery cell provided in this application, the negative electrode film layer uses a negative electrode active material containing silicon elements within the above-mentioned range, which can effectively improve the specific capacity of the negative electrode. When the areal density within the above-mentioned range is used at the same time, it can also improve the fast charging performance of the battery.

[0141] Furthermore, by combining the aforementioned positive electrode film and the aforementioned negative electrode film at an appropriate areal density ratio, lithium plating problems can be avoided, resulting in higher energy density, better charging capability, and superior cycle performance for the battery cell, thus comprehensively improving battery performance.

[0142] In some embodiments, the silicon element constitutes 2% to 10% of the negative electrode active material by mass, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or other unlisted values ​​within the range of 2% to 10%. In some embodiments, the silicon element constitutes 4% to 8% of the negative electrode active material by mass.

[0143] When the negative electrode film layer uses a negative electrode active material containing silicon elements within the above range, it can further improve the energy density and charging performance of the battery.

[0144] In some embodiments, the negative electrode active material includes silicon-based materials and carbon-based materials, wherein the silicon-based material includes one or more of silicon-carbon composites and silicon oxides; and / or, the carbon-based material includes one or more of artificial graphite and natural graphite.

[0145] When graphite-based carbon materials are used as anode active materials, they exhibit good electrochemical performance, long cycle life, and low cost. When silicon-based materials are used together with graphite-based carbon materials, the specific capacity of the anode active material can be further improved.

[0146] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0147] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 6 μm, such as 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 electrode current collector is 4 μm to 5.5 μm.

[0148] Anode current collectors with the aforementioned thickness range can further improve energy density.

[0149] In some embodiments, the ratio of the one-sided thickness of the negative electrode film to the thickness of the negative electrode 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 one-sided thickness of the negative electrode film to the thickness of the negative electrode current collector is 12 to 18.

[0150] When negative electrode films of the aforementioned thickness range are combined with negative electrode current collectors, energy density and charging performance can be further balanced, thus comprehensively improving battery performance.

[0151] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0152] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0153] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0154] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0155] In some embodiments, the compaction density of the negative electrode sheet is 1.4 g / cm³. 3 Up to 1.6 g / cm 3 For example, 1.4, 1.45, 1.5, 1.55, 1.6, or 1.4 g / cm³. 3 Up to 1.6 g / cm 3 Other values ​​not listed within the range.

[0156] The negative electrode sheet provided in this application has a compaction density within the above-mentioned range, and therefore has a better energy density.

[0157] In some embodiments, the electrode compaction density described in this application can be the compaction density of the corresponding electrode when the battery cell is discharged to 0% SOC.

[0158] In some embodiments, the film thickness in the electrode described in this application can be the film thickness of the electrode corresponding to the state of 0% SOC of a single battery cell.

[0159] [Electrolytes]

[0160] The electrolyte acts as a conductor of ions between the positive and negative electrodes. For example, the electrolyte can be liquid, solid, or gel-like.

[0161] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and an organic solvent.

[0162] In the embodiments of this application, the types and contents of organic components in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0163] In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or the battery can be fully discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC), and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis.

[0164] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis using standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or the free electrolyte obtained from the battery after it has been fully discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be used as a sample for detection by ion chromatography analysis.

[0165] In some embodiments, the organic solvent includes a carbonate solvent. In some embodiments, the carbonate solvent includes chain carbonate compounds. In some embodiments, the carbonate solvent includes one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0166] When the above-mentioned type of carbonate solvent is used in the electrolyte, the wetting problem of the positive and negative electrode sheets in the electrolyte can be further improved; when combined with the above-mentioned positive and negative electrode film layers with high areal density, the wetting problem of the electrode sheets in the electrolyte caused by high areal density can be further avoided, thus comprehensively improving the performance of the battery.

[0167] In some embodiments, the organic solvent comprises dimethyl carbonate, and the mass percentage of 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%, etc., or other unlisted values ​​within the range of 4% to 20%. In some embodiments, the organic solvent comprises dimethyl carbonate, and the mass percentage of dimethyl carbonate based on the total mass of the electrolyte is 8% to 16%.

[0168] When dimethyl carbonate within the above-mentioned ratio range is used as an electrolyte solvent, it can improve wetting issues while also improving gas production, thus comprehensively improving the battery's cycle performance.

[0169] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0170] In some embodiments, the electrolyte further includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0171] 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, and 1,3-propanesulfonate lactone.

[0172] When the above-mentioned type of carbonate additive is used in the electrolyte, an SEI film can be formed on the surface of the silicon-containing anode. This SEI film can cover the electrode surface to reduce the degree of electrode exposure to the electrolyte, reduce side reactions and gas generation on the surface of the silicon-containing anode, and further improve the cycle performance of the battery.

[0173] In some embodiments, the additive includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate in the electrolyte is 5% to 30% based on the total mass of the electrolyte, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 26%, 27%, 28%, 29%, 30%, etc., or other unlisted values ​​within the range of 5% to 30%. In some embodiments, the additive includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate in the electrolyte is 5% to 15% based on the total mass of the electrolyte.

[0174] Using fluoroethylene carbonate within the above-mentioned ratio range as an electrolyte solvent can further improve the side reactions and gas generation problems on the silicon-containing anode surface, thereby further improving the cycle performance of the battery.

[0175] In some embodiments, the conductivity of the electrolyte is from 9 mS / cm to 14 mS / cm, for example 9, 10, 11, 12, 13, 14, etc., or other unlisted values ​​in the range of 9 mS / cm to 14 mS / cm.

[0176] The battery cell provided in this application has a conductivity within the above-mentioned range, and therefore has good electrochemical performance.

[0177] [Isolation membrane]

[0178] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. The separator can be a single-layer thin film or a multi-layer composite thin film, without particular limitation. When the separator is a multi-layer composite thin film, the materials of each layer can be the same or different, without particular limitation.

[0179] In some embodiments, the separator includes a substrate and a ceramic coating disposed at least on the side close to the positive electrode.

[0180] Applying a ceramic coating to the substrate surface can improve its thermal safety; and since the voltage is higher on the side closer to the positive electrode, applying a ceramic coating on that side can further improve its oxidation resistance.

[0181] 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 with a thickness of 9 μm to 14 μm, such as 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 with a thickness of 5 μm to 8 μm, such as 5, 6, 7, 8, or other unlisted values ​​within the range of 5 μm to 8 μm. In some embodiments, the ceramic coating has a thickness of 1 μm to 3 μm, such as 1, 1.5, 2, 2.5, 3, or other unlisted values ​​within the range of 1 μm to 3 μm.

[0182] When a substrate with the thickness range mentioned above is used in combination with a ceramic coating, it is possible to improve its thermal safety, while also taking into account its ion permeability and reducing its internal resistance.

[0183] [Battery cell]

[0184] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0185] In some embodiments, the battery cell includes an electrode assembly comprising a positive electrode, a separator, and a negative electrode stacked sequentially. The ratio of the dimension of the positive electrode film layer along the length of the electrode assembly to the dimension of the electrode assembly along the length of the electrode assembly is 92% to 95%, such as 92%, 93%, 94%, 95%, or other unlisted values ​​within the range of 92% to 95%. In some embodiments, the ratio of the dimension of the positive electrode film layer along the width of the electrode assembly to the dimension of the electrode assembly along the width of the electrode assembly is 92% to 96%, such as 92%, 93%, 94%, 95%, 96%, or other unlisted values ​​within the range of 92% to 96%.

[0186] When the battery cells provided in this application are stacked in the manner described above, the energy density of the battery can be further improved.

[0187] In some embodiments, the positive electrode includes a positive tab, and the negative electrode includes a negative tab.

[0188] In some embodiments, the positive electrode tab extends along a first direction of the positive electrode sheet, and in a second direction of the positive electrode sheet, the ratio of the width of the positive electrode tab to the width of the positive electrode sheet is 50% to 100%, such as 50.1%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or other unlisted values ​​within the range of 50% to 100%. In some embodiments, the second direction is perpendicular to the first direction.

[0189] When the battery cell provided in this application uses the electrode with the above-mentioned width range and structural features, the charging temperature rise of the battery can be further improved.

[0190] In some embodiments, the battery cell further includes a top cover, which is provided with electrode terminals for direct electrical connection to the positive tab and / or the negative tab.

[0191] Conventional batteries require adapter plates to connect the electrode terminals and tabs, which reduces the utilization rate of the electrode assembly and lowers the battery energy density. When the battery cell provided in this application adopts the above structure, eliminating the need for adapter plates effectively solves this problem, reduces the battery's internal resistance, and further improves both battery energy density and fast-charging performance.

[0192] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0193] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0194] In some embodiments, the battery cell further includes a casing. In some embodiments, the length-to-width ratio of the casing is 4 to 7, for example, 4, 5, 6, 7, or other unlisted values ​​within the range of 4 to 7. In some embodiments, the length of the casing is 400 mm to 600 mm, for example, 400, 450, 500, 550, 600, or other unlisted values ​​within the range of 400 mm to 600 mm. In some embodiments, the width of the casing is 90 mm to 120 mm, for example, 90, 100, 110, 120, or other unlisted values ​​within the range of 90 mm to 120 mm. In some embodiments, the height of the casing is 13 mm to 25 mm, for example, 13, 15, 17, 19, 21, 23, 25, or other unlisted values ​​within the range of 13 mm to 25 mm. In some embodiments, the housing is an aluminum shell with a thickness of 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, or other unlisted values ​​within the range of 0.2 mm to 0.3 mm.

[0195] Using a casing within the aforementioned size range allows for both increased energy density and reduced battery internal resistance, thereby improving both battery energy density and fast charging performance.

[0196] In some embodiments, the energy density of the battery cell is between 210 Wh / kg and 250 Wh / kg.

[0197] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 shows a square-structured battery cell 5 as an example. Optionally, the battery cell is a lithium-ion battery or a sodium-ion battery.

[0198] In some embodiments, referring to FIG3, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed 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 practical needs.

[0199] In some embodiments, a battery device is provided, which may be a battery module, a battery pack, an energy storage battery, etc. The battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module may be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0200] Figure 4 shows a battery module 4 as an example. Referring to Figure 4, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0201] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0202] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0203] Figures 5 and 6 show a battery pack 1 as an example. Referring to Figures 5 and 6, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0204] [Electrical appliances]

[0205] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0206] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0207] Figure 7 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0208] In some embodiments, the electrical device includes a vehicle, and the electrode assembly is positioned along the length of the vehicle's direction of travel.

[0209] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0210] Example

[0211] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0212] I. Implementation Examples

[0213] Example 1

[0214] 1) Negative electrode plate

[0215] The composition includes negative electrode active material, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose, with a mass ratio of 96.4:0.6:1.0:2.0; the thickness of the copper foil for the negative electrode current collector is 4.5 μm; the ratio of the single-layer thickness of the negative electrode film to the thickness of the negative electrode current collector is 14.1; and the single-sided coating density of the negative electrode sheet is 0.152 g / 1540 mm². 2 The compaction density of the negative electrode sheet is 1.55 g / cm³.3 .

[0216] The negative electrode active material includes silicon-based materials and carbon-based materials. The silicon-based material (silicon-carbon material) is mixed with the carbon-based material (graphite) so that the silicon content in the negative electrode active material is 5%.

[0217] 2) Positive electrode plate

[0218] The composition includes lithium iron phosphate (LFP) as the positive electrode active material, lithium ferrite (Li5FeO4) as the lithium supplement agent, polyvinylidene fluoride (PVDF) as the binder, and acetylene black as the conductive agent, in a mass ratio of 95.9:0.3:2.3:1.5. The thickness of the aluminum foil used as the positive electrode current collector is 10 μm, the ratio of the thickness of the single-sided positive electrode film to the thickness of the positive electrode current collector is 11.1, and the single-sided coating areal density of the positive electrode sheet is 0.445 g / 1540 mm². 2 The compaction density of the positive electrode sheet is 2.55 g / cm³. 3 .

[0219] The positive electrode active material comprises lithium phosphate particles with a longest diameter of 0.1μm-0.3μm and lithium phosphate particles with a longest diameter of 1μm-5μm, with a mass ratio of 90:10 between the lithium phosphate particles with a longest diameter of 0.1μm-0.3μm and the lithium phosphate particles with a longest diameter of 1μm-5μm.

[0220] The longest diameter of the lithium supplement Li5FeO4 is 11 μm. The surface of the lithium supplement Li5FeO4 has a carbon coating layer with a thickness of 30 nm.

[0221] 3) Electrolyte

[0222] The electrolyte comprises DMC, EMC, DEC, and EC solvents (mass ratio 15:40:15:30), 13% lithium hexafluorophosphate (LiPF6) by mass relative to the total electrolyte mass, and 10% fluoroethylene carbonate (FEC) by mass relative to the total electrolyte mass. The lithium-ion conductivity of the electrolyte is 11 mS / cm.

[0223] 4) Separating membrane

[0224] The diaphragm consists of a PE base membrane with a thickness of 5 μm, and one side of the base membrane is coated with a ceramic coating with a thickness of 2 μm, the ceramic coating consisting of alumina.

[0225] 5) Battery cells

[0226] A stacked electrode assembly is prepared by stacking positive electrode sheets, a separator, and a negative electrode sheet. The ratio of the dimension of the positive electrode film along the length of the electrode assembly to the length of the electrode assembly is 93.5%, the ratio of the dimension of the positive electrode film along the width of the electrode assembly to the width of the electrode assembly is 93%, and the ratio of the width of the electrode tabs to the width of the electrode assembly is 70%. The positive and negative electrode tabs are located at opposite ends along the length 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 shell wall thickness is 0.3 mm, and electrolyte is injected into it. After processes such as encapsulation, settling, formation, aging, secondary encapsulation, and capacity testing, a battery cell is obtained, in which the electrode tabs of the electrode assembly are directly connected to the top cover. The energy density of the battery cell is 221 Wh / kg.

[0227] Examples 2-5

[0228] The difference between the battery cells in Examples 2-5 and Example 1 is that the mass content of silicon in the negative electrode active material is changed (the mass of graphite is changed accordingly), and the surface density of the coating on one side of the positive and negative electrode sheets is also changed. As a result, the ratio of the thickness of the positive electrode film to the thickness of the positive current collector and the ratio of the thickness of the negative electrode film to the thickness of the negative current collector change with the change of coating density, as shown in Tables 1-3.

[0229] Examples 6-9

[0230] The difference between the battery cells in Examples 6-9 and those in Example 1 is that the proportion of carbonate solvent (dimethyl carbonate) in the electrolyte was changed, and the amount of another solvent was increased accordingly, as detailed in Tables 1-3.

[0231] Examples 10-12

[0232] The difference between the battery cells in Examples 10-12 and those in Example 1 is that the content of lithium replenishing agent in the positive electrode film layer was changed, as detailed in Tables 1-3.

[0233] Example 13

[0234] The difference between the battery cell in Example 13 and that in Example 1 is that the type of lithium replenishing agent in the positive electrode film is changed, and the surface of the lithium replenishing agent does not have a carbon-containing coating layer, as detailed in Tables 1-3.

[0235] Examples 14-15

[0236] The difference between the battery cells in Examples 14-15 and those in Example 1 is that the thickness of the carbon coating layer on the surface of the lithium replenishing agent in the positive electrode film was changed, as detailed in Tables 1-3.

[0237] Examples 16-18

[0238] The difference between the battery cells in Examples 16-18 and those in Example 1 is that the amount of fluoroethylene carbonate (FEC) added to the electrolyte additive was changed, as detailed in Tables 1-3.

[0239] Example 19

[0240] The difference between the battery cell in Example 19 and that in Example 1 is that the type of carbonate solvent and the type of carbonate additive in the electrolyte have been changed, as detailed in Tables 1-3.

[0241] Comparative Examples 1-2

[0242] The difference between Comparative Examples 1-2 and Example 1 is that the negative electrode active material does not contain silicon-based materials, and therefore 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 and negative electrode sheets is changed. Therefore, the ratio of the single-sided thickness of the positive electrode film to the thickness of the positive current collector and the ratio of the single-sided thickness of the negative electrode film to the thickness of the negative current collector both change with the change of coating density, as shown in Tables 1-3.

[0243] Comparative Examples 3-4

[0244] The difference between Comparative Examples 3-4 and Example 1 is that the proportion of silicon-based material in the negative electrode active material was changed, thus changing the mass content of silicon (the mass of carbon-based material graphite was changed accordingly); and the surface density of the single-sided coating of the negative electrode sheet was changed, so the ratio of the single-sided thickness of the negative electrode film to the thickness of the negative electrode current collector changed with the change of coating density, as shown in Tables 1-3.

[0245] II. Performance Testing

[0246] 1. Test method for silicon content

[0247] After the negative electrode sheet is heated at 400℃ for 2 hours, the negative electrode active material powder is scraped off from the current collector, ground, and then sieved through a 200-mesh sieve. The mass percentage of silicon can be obtained by testing the ICP.

[0248] 2. The surface density of the coating on one side of the positive and negative electrode sheets.

[0249] The double-coated electrode sheets were disassembled, and the residual electrolyte was treated with dimethyl carbonate solvent. The electrode sheets were then dried and cut to a diameter of 1540 mm². 2 If a small circular sheet weighs M, and a current collector of the same area weighs N, then the single-sided coating weight of the positive electrode sheet is (MN) / 2.

[0250] 3. Test methods for electrolyte composition and content

[0251] The types and quality of additives and solvents in the electrolyte can be obtained by methods known to those skilled in the art. For example, the composition of the electrolyte can be determined by liquid chromatography, ultraviolet spectrophotometry, or ultraviolet-visible spectrophotometry. For instance, the electrolyte is diluted 3-10 times with acetonitrile to obtain a diluted electrolyte solution to be tested. Using a GC-MS 3100 organic component gas chromatograph, the diluted electrolyte solution is placed in the instrument for full-scan qualitative analysis. The injection port temperature is 250°C, and the scan range is 35μm~270μm. After the test, a total ion chromatogram of each organic compound is obtained. The peak positions are compared with the corresponding organic compounds, and the percentage content of each organic compound is calculated based on the peak area.

[0252] 4. Lithium-ion conductivity of the electrolyte

[0253] Take approximately 100 mL of electrolyte sample in a dry, clean, corrosion-resistant sample bottle, seal it, and place it in a constant-temperature water bath. Shake the sample occasionally and maintain the temperature at 25℃ (deviation ±0.5℃). After the sample temperature stabilizes, use a commercially available conductivity meter to test its conductivity. After thoroughly drying the conductivity meter with calibration solution, place it vertically into the liquid to be tested, click to start the test, and record the test results after the data has stabilized for more than 10 seconds.

[0254] 5. Morphological observation of the lithium replenishing agent and its carbon coating layer, observation of the longest diameter of the lithium replenishing agent, and observation of the longest diameter of the lithium phosphate-containing material in the positive electrode film.

[0255] The prepared positive electrode film was tested using an electron microscope.

[0256] 6. Under fully discharged battery cell conditions, the compaction density and film thickness of the positive and negative electrode sheets.

[0257] The battery cells were discharged to 0% SOC using a 0.33C discharge strategy. The fully discharged electrodes were then removed, and the residual electrolyte was treated with dimethyl carbonate solvent. The electrodes were dried, and a test sample with an area of ​​S was weighed using an electronic balance. The weight was recorded as W, and the thickness T of the electrode was measured using a micrometer. The compaction density is then calculated as W / (T×S).

[0258] The thickness of the positive and negative electrode films can be measured using a micrometer (e.g., Mitutoyo 293-100, with an accuracy of 0.1 μm).

[0259] 7. Fast charging performance

[0260] Charging time test: ① Voltage calibration: 1) The positive electrode, negative electrode, separator, and electrolyte in the example or comparative example are used to prepare a stacked three-electrode battery, and it is placed at 25℃ for 30 min; 2) At 25℃, the battery cell is charged at 0.33C to the charging cutoff voltage of 3.65V, and then constant voltage charging is continued at the charging cutoff voltage until the current is 0.05C, and the charging is cut off (where C represents the rated capacity of the battery cell); 3) Place it at 25℃ for 1 h; 4) At 25℃, the battery cell is discharged at 0.33C to the discharge cutoff voltage of 2.5V, and the total discharge capacity C0 of the battery cell is recorded; 5) Place it at 25℃ for 1 h. ② Room temperature charging test: 1) Prepare a stacked three-electrode battery using the positive electrode, negative electrode, separator, and electrolyte from the examples or comparative examples, and let it stand for 30 minutes; 2) Discharge with 0.33C0 DC to the discharge cutoff voltage of 2.5V, at which point the SOC is 0%; 3) Let it stand for 5 minutes; 4) Charge with 5C0 constant current until the negative electrode potential is 0V, and read the capacity C1 at this point, which corresponds to C1 / C0SOC; 5) Let it stand for 5 minutes; 6) Charge with 4.5C0 constant current until the negative electrode potential is 0V, and read the capacity C2 at this point, which corresponds to C2 / C0SOC; 7) Let it stand for 5 minutes; 8) Charge with 4C0 constant current until the negative electrode potential is 0V, and read the capacity C3 at this point, which corresponds to C3 / C0SOC; 9) Let it stand for 5 minutes; 10) Charge with 3C0 constant current until the negative electrode potential is 0V, and read the capacity C4 at this point. 11) Let stand for 5 minutes; 12) Charge with 2C0 at a constant current until the negative electrode potential is 0V, and read the capacity C5 at this time, which corresponds to C5 / C0SOC; 13) Let stand for 5 minutes; 14) Charge with 1C0 at a constant current until the negative electrode potential is 0V, and read the capacity C6 at this time, which corresponds to C6 / C0SOC; 15) Let stand for 5 minutes; 16) Charge with 0.8C0 at a constant current until the negative electrode potential is 0V, and read the capacity C7 at this time, which corresponds to C7 / C0SOC; 17) Let stand for 5 minutes; 18) Charge with 0.5C0 at a constant current until the negative electrode potential is 0V, and read the capacity C8 at this time, which corresponds to C8 / C0SOC; 19) Let stand for 5 minutes; 20) Charge with 0.33C0 at a constant current until the negative electrode potential is 0V, and read the capacity C9 (i.e., C0), which corresponds to 100%SOC. The required charging time is obtained by summing the total charging time from 10% SOC to 80% SOC.

[0261] 8. Mass energy density

[0262] At 25℃, the battery cell was discharged at a constant current of 0.33C to 2.5V, allowed to stand for 5 minutes, then charged at a constant current of 0.33C to the upper cutoff voltage of 3.65V, followed by constant voltage charging to a current of 0.05C, and allowed to stand for 5 minutes. It was then discharged at a constant current of 0.33C to the cutoff voltage of 2.5V, and the discharge energy E0 (Wh) was recorded. Mass energy density (Wh / kg) = Discharge energy E0 (Wh) / Battery cell mass (kg).

[0263] 9. Cyclic performance

[0264] At 25°C, charge the battery to 3.65V at a charging rate of 0.5C (the nominal capacity), then charge it to 0.05C at 3.65V, let it stand for 10 minutes, and then discharge it to 2.5V at a discharging rate of 1C, let it stand for 10 minutes. One charge-discharge cycle is one cycle. Continue the test until the battery capacity decreases to 80% of the nominal capacity. This number of cycles is recorded as the number of cycles @ 80% SOH.

[0265] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0266] Battery cells for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 3 below.

[0267] Table 1 Preparation parameters

[0268] Table 2 Preparation parameters

[0269] Table 3 Preparation and performance parameters

[0270] In the battery cells of Examples 1-19, a positive electrode film containing lithium phosphate as the positive electrode active material was used, and the areal density of the positive electrode film on one side was 0.35 g / 1540.25 mm. 2 Up to 0.5g / 1540.25mm 2 Meanwhile, all of them use a silicon-containing material as the negative electrode active material for the negative electrode film layer (the silicon content is 2% to 10% based on the mass percentage of the negative electrode active material), and the areal density of the single-sided negative electrode film layer is 0.13g / 1540.25mm. 2 Up to 0.19g / 1540.25mm 2 Therefore, the battery cells prepared in Examples 1 to 13 all have excellent energy density, cycle performance, and fast charging performance.

[0271] The negative electrode active material in Comparative Example 1 does not contain silicon, and the coating surface density of the positive electrode film is low (the surface density of the single-sided positive electrode film is less than 0.35 g / 1540.25 mm). 2 ).

[0272] A comparison of Comparative Example 1 with Examples 1-19 shows that the negative electrode active material contains silicon, and 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 Only 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.

[0273] 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 ).

[0274] 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.

[0275] 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 ).

[0276] 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 2Only 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.

[0277] 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 ).

[0278] 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.

[0279] 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.

[0280] 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.

[0281] 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.

[0282] 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.

[0283] 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.

[0284] 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.

[0285] 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.

[0286] 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.

[0287] 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.

[0288] 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 the 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; 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 gap has a width of 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 proportion 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 proportion 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 positive electrode current collector has a thickness of 10 μm to 15 μm.

23. The battery cell of claim 22, wherein, The positive electrode current collector has a thickness of 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 negative electrode current collector has a thickness of 4 μm to 6 μm.

28. The battery cell of claim 27, wherein, The negative electrode current collector has a thickness of 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 a 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 polypropylene film has a thickness of 9 μm to 14 μm; and / or The substrate comprises a polyethylene film, and the polyethylene film has a thickness of 5 μm to 8 μm. The ceramic coating layer has a thickness of 1 μm to 3 μm.

34. The battery cell of any one of claims 31-33, wherein, The battery monomer comprises an electrode assembly, and the electrode assembly comprises 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%, and the second direction is perpendicular to the first direction. The battery monomer 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 monomer further comprises a shell, and the shell is an aluminum shell, and the aluminum shell has a thickness of 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 shell has a length of 400 mm to 600 mm, a width of 90 mm to 120 mm, and a height of 13 mm to 25 mm.

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

41. The battery cell of any one of claims 1-40, wherein, The battery device comprises at least one of a battery module, a battery pack, and an energy storage battery, and the battery device comprises the battery monomer.

42. A battery device, comprising: The battery monomer comprises the battery monomer.

43. An electrical device, comprising: ​ 44. The powered device of claim 43, wherein, The power utilization device includes a vehicle, and the length direction of the electrode assembly is placed along a traveling direction of the vehicle.

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