Battery cell, electrolyte, battery device, and electrical apparatus

Abstract

The present application discloses a battery cell, an electrolyte, a battery device, and an electrical device. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte. The electrolyte comprises a lithium salt, a solvent, and a sulfonate ester additive. Based on the total mass of the electrolyte, a mass percentage of the solvent is 65 wt% to 85 wt%, a mass percentage of the lithium salt is 8 wt% to 15 wt%, and a mass percentage of the sulfonate additive is 0.1 wt% to 5 wt%. The solvent comprises a cyclic carbonate having a mass content of 20 wt% to 35 wt% and a linear carboxylate having a mass content of 60 wt% to 80 wt%. The lithium salt comprises a first lithium salt and a second lithium salt in a mass ratio of 1:10 to 4:1. A length of the battery cell is 200 mm to 1600 mm, a width of the battery cell is 100 mm to 500 mm, and a thickness of the battery cell is 20 mm to 80 mm. The length-to-thickness ratio of the battery cell is 5 to 150. According to the embodiments of the present application, both the high-rate charging and discharging performance and the cycle life of a battery cell can be ensured.

Description

Battery cell, electrolyte, battery device and electric device TECHNICAL FIELD

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

[0002] Battery cells have become one of important energy sources in human production and life because they can convert chemical energy into electrical energy, and are widely used in many fields such as electric tools, electric vehicles and electronic devices to provide electrical energy.

[0003] With the wide application of battery cells in various fields, the requirements for their performance are also increasingly high, among which the charge-discharge performance and cycle performance of battery cells have become the focus of attention. Therefore, how to improve the charge-discharge performance and cycle performance of battery cells is one of the technical problems to be solved by battery cells at present. SUMMARY

[0004] The embodiments of the present application provide a battery cell, an electrolyte, a battery device and an electric device, which can balance the large-rate charge-discharge performance and cycle life of the battery cell.

[0005] In a first aspect, the embodiments of the present application provide a battery cell, which comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, the electrolyte comprising a lithium salt, a solvent and a sulfonate additive; the mass percentage of the solvent is 65wt% to 85wt%, the mass percentage of the lithium salt is 8wt% to 15wt%, and the mass percentage of the sulfonate additive is 0.1wt% to 5wt% based on the total mass of the electrolyte; wherein the solvent comprises 20wt% to 35wt% of a cyclic carbonate and 60wt% to 80wt% of a linear carboxylate; the lithium salt comprises a first lithium salt and a second lithium salt with a mass ratio of 1:10 to 4:1; the length of the battery cell is 200mm to 1600mm, the width of the battery cell is 80mm to 500mm, the thickness of the battery cell is 10mm to 100mm, and the length-thickness ratio of the battery cell is 5 to 150.

[0006] The embodiments of the present application design the electrolyte formula as a whole, so that the components in the electrolyte can synergistically enhance each other, and when applied to the battery cell, the large-rate charge-discharge performance and cycle life can be improved at the same time.

[0007] Meanwhile, the size of the battery cell in the embodiments of the present application can increase the heat dissipation area of the battery cell, and also make the current density distribution of the battery cell more uniform during the charge-discharge process, thereby reducing the internal resistance of the battery and improving the charge-discharge efficiency.

[0008] In any embodiment of this application, in order to better improve the heat dissipation performance of the battery cell and thus improve the fast charging performance of the battery cell, the length of the battery cell is 200-1200mm, the width of the battery cell is 100-300mm, the thickness of the battery cell is 15-60mm, and the length-to-thickness ratio of the battery cell is 5-60.

[0009] In any embodiment of this application, the negative electrode includes a negative electrode tab and a negative electrode membrane. The width W of the negative electrode tab, the height H1 of the negative electrode membrane, and the length L1 of the negative electrode membrane satisfy the following relationship: 0.04 mm / cm 2 ×H1×L1≤W≤1.40mm / cm 2 ×H1×L1.

[0010] By adjusting the dimensions of the negative electrode tab and the negative electrode film, the heat dissipation and current carrying capacity of the negative electrode tab and other current-carrying components can be improved, thereby increasing the charging and discharging efficiency of the battery cell.

[0011] In any embodiment of this application, in order to better improve the heat dissipation and current carrying capacity of the tabs and other current-carrying components, thereby improving the charging and discharging efficiency of the battery cell, the negative electrode sheet includes a negative electrode tab and a negative electrode film. The width W of the negative electrode tab, the height H1 of the negative electrode film, and the length L1 of the negative electrode film satisfy the following relationship: 0.05 mm / cm 2 ×H1×L1≤W≤1.20mm / cm 2 ×H1×L1.

[0012] In any embodiment of this application, the first lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, and lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide.

[0013] The first lithium salt in this application embodiment has better thermal stability, chemical stability and hydrolysis resistance. When used in an electrolyte, it can improve the stability of the electrolyte and increase the cycle life of the battery cell.

[0014] In any embodiment of this application, the second lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

[0015] The second lithium salt in this embodiment can react with the current collector to form a passivation film, reducing the possibility of corrosion of the current collector; it also has high ionic conductivity. This improves the reliability and rate performance of the battery cell.

[0016] In any embodiment of this application, the lithium salt comprises lithium bisfluorosulfonylimide and lithium hexafluorophosphate in a mass ratio of 1:10 to 4:1.

[0017] The embodiments of this application use a mixed lithium salt with a specific ratio for the electrolyte, which can better balance the reliability and rate performance of the battery cells.

[0018] In any embodiment of this application, the thermal decomposition temperature of the first lithium salt is 150–600°C.

[0019] The embodiments of this application have a suitable range of first lithium salt thermal decomposition temperatures, which can better balance the reliability and rate performance of the battery cells.

[0020] In any embodiment of this application, the thermal decomposition temperature of the second lithium salt is 60–200°C.

[0021] The embodiments of this application have a suitable range of second lithium salt thermal decomposition temperatures, which can better balance the reliability and rate performance of the battery cells.

[0022] In any embodiment of this application, the concentration of the first lithium salt is 0.1 to 0.5 mol / L.

[0023] The embodiments of this application have a suitable range of first lithium salt concentrations, which can better balance the reliability and rate performance of the battery cells.

[0024] In any embodiment of this application, the concentration of the second lithium salt is 0.5 to 1.5 mol / L.

[0025] The embodiments of this application have a suitable range of second lithium salt concentrations, which can better balance the reliability and rate performance of the battery cells.

[0026] In any embodiment of this application, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and γ-butyrolactone.

[0027] The cyclic carbonate used in the embodiments of this application is used in the electrolyte to promote the dissociation of lithium salt, thereby improving the ionic conductivity of the electrolyte.

[0028] In any embodiment of this application, the linear carboxylic acid ester includes one or more of ethyl acetate, propyl acetate, methyl formate, methyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

[0029] The linear carboxylic acid esters used in the embodiments of this application can reduce the viscosity of the electrolyte and thereby improve the ionic conductivity of the electrolyte.

[0030] In any embodiment of this application, based on the total mass of the solvent, the mass percentage of cyclic carbonates is 20wt% to 35wt%, and the mass percentage of linear carboxylic acid esters is 60wt% to 80wt%.

[0031] In any embodiment of this application, the sulfonate additives include one or more of 1,3-propanesulfonate lactone, propenyl-1,3-propanesulfonate lactone, 1,3-sulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, and methylene disulfonate.

[0032] When the sulfonate ester additives of this application are used as electrolyte additives in battery cells, they can form stable CEI and SEI films on the electrode surface, thereby improving ion transport between the electrode and the electrolyte and reducing electrolyte corrosion of the electrode. Simultaneously, the sulfonate ester additives of this application can also promote the dissolution and ionization of the first and second lithium salts, thereby increasing the lithium ion migration rate. Furthermore, the sulfonate ester additives of this application can reduce the possibility of metal ion deposition and further reduce interfacial impedance.

[0033] The sulfonate additives in this application embodiment can also work synergistically with the first lithium salt to jointly inhibit the decomposition and gas generation reaction of the electrolyte, thereby reducing the interfacial impedance.

[0034] In any embodiment of this application, the electrolyte further includes one or more of unsaturated cyclic carbonate additives and dehydration and deacidification additives.

[0035] The sulfonate additives in this application embodiment can work synergistically with unsaturated cyclic carbonate additives to jointly reduce interfacial impedance.

[0036] In any embodiment of this application, the electrolyte further includes lithium salt additives, which include one or more of LiDFOB, LiBOB, LiBF4, LiPO2F2 and LiSO3F.

[0037] The additives in this application embodiment can better reduce interface impedance, thereby improving the rate performance of the battery cell.

[0038] In any embodiment of this application, the unsaturated cyclic carbonate additives include one or more of vinylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

[0039] The unsaturated cyclic carbonates of this application embodiment can form an SEI film on the negative electrode surface, thereby improving the cycle stability and lifespan of the battery cell. Simultaneously, the unsaturated cyclic carbonates of this application embodiment can synergistically interact with the first lithium salt in the electrolyte, inhibiting electrolyte decomposition and gas generation reactions, thus improving electrolyte stability and extending the battery cell's lifespan when used in battery cells.

[0040] In any embodiment of this application, the dehydration and deacidification additive includes one or more of the following: additives containing isocyanate groups, additives containing isothiocyanate groups, additives containing siloxane groups, additives containing silazane groups, and additives containing phosphate ester groups.

[0041] The dehydrating and deacidifying additives of this application can reduce trace amounts of water and acidic substances in the electrolyte, thereby improving the cycle life of the battery cells.

[0042] In any embodiment of this application, the additives containing isocyanate groups include one or more of phenyl isocyanate, hexamethylene diisocyanate, tetraisocyanosilane, 3-isocyanopropyltrimethoxysilane, isophorone diisocyanate, and 4-fluorophenyl isocyanate; the additives containing isothiocyanate groups include 1-isothiocyanate-PEG3-azide; the additives containing siloxane groups include one or more of (trimethylsilyl)phosphite, tris(trimethylsilane)borate, tris(trimethylsilyl)phosphite, tetravinylsilane, and tetraethynylsilane; the additives containing silazane groups include one or more of heptamethyldisilazane and N,N-diethyltrimethylsilaneamine; and the additives containing phosphate ester groups include triargyl phosphate.

[0043] The dehydrating and deacidifying additives of this application can better reduce trace amounts of water and acidic substances in the electrolyte, thereby improving the cycle life of the battery cells.

[0044] In any embodiment of this application, based on the total mass of the electrolyte, the mass percentage of unsaturated cyclic carbonate additives is 1% to 5%; and the mass percentage of dehydration and deacidification additives is 0.01% to 2%.

[0045] The hybrid additives in this application embodiment can better balance the high-rate charge-discharge performance and cycle life of individual battery cells.

[0046] In any embodiment of this application, the positive electrode sheet includes a current collector and a positive active material layer stacked together. The positive active material layer includes positive active material particles with an average particle size Dv50 of 0.2–10 μm and a specific surface area of ​​10–20 m². 2 / g.

[0047] The positive electrode active material particles with suitable particle size and specific surface area in this application embodiment can reduce the DC internal resistance (DCR) of the electrode, and when used in a battery cell, can improve ionic conductivity, thereby increasing discharge power. Simultaneously, it can also reduce the possibility of excessive absorption of trace water due to an excessively large specific surface area.

[0048] In any embodiment of this application, the negative electrode sheet includes a current collector and a negative electrode active material layer stacked together. The negative electrode active material layer includes negative electrode active material particles, which are artificial graphite. The average particle size Dv50 of the artificial graphite is 5–15 μm, and the specific surface area is 0.5–3 m². 2 / g.

[0049] The negative electrode active material particles with suitable particle size and specific surface area in this application embodiment can reduce the DC internal resistance (DCR) of the electrode, and when used in battery cells, can improve ionic conductivity, thereby increasing discharge power. Simultaneously, it can also reduce the possibility of excessive absorption of trace water due to an excessively large specific surface area.

[0050] In any embodiment of this application, the positive electrode active material particles include first lithium iron phosphate particles and second lithium iron phosphate particles, wherein the particle size Dv50 of the first lithium iron phosphate particles is 0.2 to 5 μm, and the particle size Dv50 of the second lithium iron phosphate particles is 0.8 to 10 μm.

[0051] The positive electrode active material particles with suitable particle size and specific surface area used in this application embodiment can improve ionic conductivity and thus increase discharge power in battery cells. To further improve the energy density of battery cells, this application embodiment uses a compounding of positive electrode active material particles of different sizes. This reduces the voids formed by the stacking of the positive electrode active material particles, thereby increasing the compaction density and ultimately improving the energy density.

[0052] In any embodiment of this application, the positive electrode active material layer includes a first surface, a second surface, a first region and a second region located between the first surface and the second surface. The first surface is distributed away from the current collector. The thickness of the positive electrode active material layer is denoted as H. The region from the first surface of the positive electrode active material layer to a thickness range of 0.3 to 0.7H is denoted as the first region of the positive electrode active material layer. The region from the second surface of the positive electrode active material layer to a thickness range of 0.3 to 0.7H is denoted as the second region of the positive electrode active material layer. The average particle size Dv50 of the active material particles in the first region is smaller than that in the second region.

[0053] In this embodiment, the average particle size of the active material particles in different regions of the positive electrode active material layer is set in a gradient, so that the average particle size Dv50 of the active material particles in the first region far from the negative electrode current collector side is smaller than the average particle size Dv50 of the active material particles in the second region close to the negative electrode current collector side. That is, the active material particles in the first region with smaller particle size can accept ions from the negative electrode side first, thereby reducing the ion transport path, improving ion conductivity, and thus improving discharge power.

[0054] In any embodiment of this application, the positive electrode active material layer further includes a binder, a conductive agent, and a surfactant.

[0055] In any embodiment of this application, the coating quality CW of the positive electrode active material layer satisfies: 200 / 1540.25mm. 2 ≤CW≤400 / 1540.25mm 2 The compacted density is 2–2.6 g / cm³. 3 .

[0056] The positive electrode active material layer in this application embodiment can better improve the energy density of the battery cell.

[0057] In any embodiment of this application, the negative electrode active material particles further include silicon-based materials, which include one or more of elemental silicon, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0058] In any embodiment of this application, the mass ratio of silicon to carbon in the negative electrode active material particles is (0-10):100.

[0059] The negative electrode active material particles in the embodiments of this application can improve the energy density of a single battery cell.

[0060] In any embodiment of this application, the negative electrode active material layer includes a first surface, a second surface, a first region and a second region located between the first surface and the second surface. The first surface is distributed away from the current collector. The thickness of the negative electrode active material layer is denoted as H. The region from the first surface of the negative electrode active material layer to a thickness range of 0.3–0.7H is denoted as the first region of the negative electrode active material layer, and the region from the second surface of the negative electrode active material layer to a thickness range of 0.3–0.7H is denoted as the second region of the negative electrode active material layer. The porosity of the active material particles in the first region is larger than that in the second region. The average particle size Dv50 of the artificial graphite in the second region is 3–10 μm, and the specific surface area is 0.8–5 m². 2 / g.

[0061] This application embodiment improves the wettability of the negative electrode active material layer and increases the ionic conductivity by gradient setting of the pore size of the active material particles in different regions of the negative electrode active material layer, so that the pore size of the active material particles in the first region is larger than that in the second region.

[0062] Secondly, embodiments of this application provide an electrolyte comprising a lithium salt, a solvent, and sulfonate additives. Based on the total mass of the electrolyte, the solvent accounts for 65 wt% to 85 wt%, the lithium salt accounts for 8 wt% to 15 wt%, and the sulfonate additives account for 0.1 wt% to 5 wt%. The solvent comprises 20 wt% to 35 wt% cyclic carbonates and 60 wt% to 80 wt% linear carboxylic acid esters. The lithium salt comprises a first lithium salt and a second lithium salt in a mass ratio of 1:10 to 4:1.

[0063] This application embodiment designs the electrolyte formulation as a whole, so that the components in the electrolyte can work together to enhance their efficiency. When applied to a single battery cell, it can improve the high-rate charge and discharge performance while also increasing the cycle life.

[0064] Thirdly, embodiments of this application provide a battery device including a battery cell as described in the first aspect.

[0065] Fourthly, embodiments of this application provide an electrical device including a battery cell as described in the first aspect. Attached Figure Description

[0066] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 shows a schematic diagram of a battery cell provided in some embodiments of this application.

[0068] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this application.

[0069] Figure 3 shows a cross-sectional schematic diagram of a stacked electrode assembly provided in some embodiments of this application.

[0070] Figure 4 shows a schematic diagram of the negative electrode sheet provided in some embodiments of this application.

[0071] The accompanying drawings are not necessarily drawn to scale.

[0072] The following are the annotations in the attached diagram: 1. Positive electrode plate; 2. Separator membrane; 3. Negative electrode plate; 4. Negative electrode tab; 5. Negative electrode film. Detailed Implementation

[0073] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0074] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0075] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, electrolyte, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical 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.

[0076] 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 understood that ranges of 60–110 and 80–120 are also expected. 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 "a–b" 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.

[0077] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0078] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0079] 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.

[0080] Unless otherwise specified, in this application, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0081] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0082] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0083] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0084] The battery cells mentioned in the embodiments of this application are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited in this respect. Figure 1 shows an example of a cuboid battery cell.

[0085] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0086] The battery cell provided in the embodiments of this application includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the negative electrode and the positive electrode. During the charging and discharging process of the battery cell, active ions (e.g., lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0087] The electrode assembly has a stacked structure, as shown in Figure 3, including a positive electrode 1, a separator 2, and a negative electrode 3. The positive electrode 1, separator 2, and negative electrode 3 are stacked sequentially. The negative electrode 3 contains a negative electrode film 5 and a negative electrode tab 4. As shown in Figure 4, the negative electrode tab 4 is located on the long side of the negative electrode film 5. The width W of the negative electrode tab 4 is parallel to the length L1 of the negative electrode film 5, and there is one negative electrode tab 4 on each negative electrode.

[0088] The battery cell also includes an outer packaging, which encapsulates the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0089] The battery cells provided in the embodiments of this application can be lithium-ion battery cells, sodium-ion battery cells, sodium-lithium-ion battery cells, lithium metal battery cells, sodium metal battery cells, lithium-sulfur battery cells, magnesium-ion battery cells, nickel-metal hydride battery cells, nickel-cadmium battery cells, lead-acid battery cells, etc., and the embodiments of this application are not limited to these.

[0090] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, the separator, and the negative electrode can be stacked to form an electrode assembly, which is then placed in an outer packaging, dried, injected with electrolyte, and subjected to vacuum sealing, settling, formation, and shaping processes to obtain the battery cell.

[0091] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0092] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0093] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0094] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0095] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0096] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0097] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0098] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0099] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0100] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, 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. Battery cells and battery devices are used to store or provide electrical energy.

[0101] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0102] With the continuous deepening of battery cell research and the continuous improvement of market demand, especially the widespread application of electric vehicles (EVs) and hybrid electric vehicles (HEVs) in recent years, not only are high energy density, sufficient reliability and ultra-long cycle life required for battery cells, but the demand for high-rate charging and discharging of battery cells is also increasing.

[0103] However, currently, improving the high-rate charge and discharge performance of individual battery cells inevitably reduces their cycle performance.

[0104] Therefore, embodiments of this application provide a battery cell, electrolyte, battery device, and power supply device that can balance the high-rate charge / discharge performance and cycle life of the battery cell.

[0105] battery cell

[0106] This application provides a battery cell comprising a positive electrode, a negative electrode, and an electrolyte. The electrolyte includes a lithium salt, a solvent, and sulfonate additives. Based on the total mass of the electrolyte, the solvent accounts for 65 wt% to 85 wt%, the lithium salt accounts for 8 wt% to 15 wt%, and the sulfonate additives account for 0.1 wt% to 5 wt%. The solvent comprises 20 wt% to 35 wt% cyclic carbonate and 60 wt% to 80 wt% linear carboxylic acid ester. The lithium salt comprises a first lithium salt and a second lithium salt with a mass ratio of 1:10 to 4:1. The battery cell has a length of 200 to 1600 mm, a width of 80 to 500 mm, a thickness of 10 to 100 mm, and an aspect ratio of 5 to 150.

[0107] The length-to-thickness ratio of a battery cell refers to the ratio of the length of the battery cell to its thickness.

[0108] In improving the rapid charge / discharge capability of battery cells, many related technologies employ methods such as increasing the ionic conductivity of the electrolyte (liquid-phase mass transfer) and improving the particle kinetics of the positive and negative electrode active materials (solid-phase diffusion). Increasing ionic conductivity is generally achieved by increasing the content of low-viscosity solvents in the electrolyte; however, low-viscosity solvents typically suffer from poor electrochemical stability, inevitably reducing the cycle life of the battery cell. Improving the particle kinetics of the positive and negative electrode active materials is generally achieved by reducing the particle size to shorten the solid-phase diffusion path. However, this increases the specific surface area of ​​the positive and negative electrode active materials and the number of active reaction sites, introducing more trace water and increasing the difficulty of removal, thereby reducing the cycle life of the battery cell.

[0109] Therefore, this application embodiment designs the electrolyte formulation holistically, enabling the components in the electrolyte to synergistically enhance each other, thereby improving both high-rate charge / discharge performance and cycle life. Specifically, this application embodiment uses a mixed solvent of cyclic carbonates and linear carboxylic esters in a specific ratio as the electrolyte solvent. The cyclic carbonates have a high dielectric constant, which can improve the dissociation and migration of lithium ions, thereby increasing the ionic conductivity of the electrolyte. The linear carboxylic esters have a low viscosity, which can reduce the adverse effects of introducing cyclic carbonates on the electrolyte viscosity. In addition, the mixing of cyclic carbonates and linear carboxylic esters in a specific ratio can reduce the viscosity of the mixed solvent, promote the dissociation of lithium salts by the mixed solvent, and improve the stability of the mixed solvent, thus balancing the ionic conductivity and stability of the electrolyte. Meanwhile, by mixing first and second lithium salts with different stabilities in a specific ratio, the stability of the electrolyte can be improved by utilizing the highly stable first lithium salt, and the second lithium salt can react with the current collector to form a passivation film, reducing the possibility of the current collector being corroded by the first lithium salt. Furthermore, the interaction between the mixed lithium salts and the mixed solvent can form a stable and highly ion-conductive passivation film on the surface of the electrode sheets, reducing the impact of the poor electrochemical stability of low-viscosity solvents on the cycle life of the battery cells. Additionally, by introducing sulfonate ester additives to form a low interfacial impedance and highly stable SEI film, the impact of the generated passivation film on kinetics and cycle stability is reduced. Thus, through the overall design of the electrolyte formulation, both high-rate charge / discharge performance and cycle life of the battery cells can be balanced.

[0110] Meanwhile, the embodiments of this application can increase the heat dissipation area of ​​the battery cell by setting the size of the battery cell, and can also make the current density distribution of the battery cell more uniform during the charging and discharging process, thereby reducing the internal resistance of the battery and improving the charging and discharging efficiency.

[0111] The mass content of solvents, lithium salts, and sulfonate ester additives in the embodiments of this application can be detected using methods commonly used in the art. As an example: first, collect freshly prepared electrolyte, or electrolyte obtained from a single battery cell, and then test it using one or more of the following methods: gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), and nuclear magnetic resonance spectroscopy (NMR).

[0112] Gas chromatography-mass spectrometry (GC-MS): In accordance with GB / T-9722-2006 / GB / T6041-2002, gas chromatography and mass spectrometry are coupled. After the components in the electrolyte are separated by gas chromatography, the components are broken into ion fragments in mass spectrometry. They are separated according to the mass-to-charge ratio (m / z) and form specific mass spectra, thereby obtaining qualitative analysis of each organic component in the electrolyte. Then, the organic components in the electrolyte are separated in the chromatographic column and the detection signal spectrum of each component is generated. The retention time is used for component qualitative analysis, and the peak area is corrected by standardization to achieve quantification, thereby obtaining quantitative analysis of the organic components in the electrolyte.

[0113] Ion chromatography (IC): In accordance with JY / T-020, the anions of lithium salts and lithium salt additives in the electrolyte are detected and quantified by ion chromatography.

[0114] Nuclear magnetic resonance spectroscopy (NMR): According to JY / T 057-2020, qualitative and quantitative analysis of the components in the electrolyte is obtained.

[0115] Optionally, the mass percentage of the solvent is independently selected from any value or a range between 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, and 85wt%.

[0116] Optionally, the mass percentage of lithium salt is independently selected from any value of 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, or a range between any two.

[0117] Optionally, based on the total mass of the electrolyte, the mass percentage of sulfonate additives is independently selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2 ... The value is any one of the following: 0.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or a range between any two.

[0118] Optionally, the mass ratio of the first lithium salt and the second lithium salt is independently selected from any value or a range between any two of the following: 1:10, 2:10, 3:10, 4:10, 5:10, 6:10, 7:10, 8:10, 9:10, 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3.0:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, and 4.0:1.

[0119] Optionally, based on the total mass of the solvent, the mass percentage of the cyclic carbonate is independently selected from any value or a range between 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, and 35 wt%.

[0120] Optionally, based on the total mass of the solvent, the mass percentage of the linear carboxylic acid ester is independently selected from any value or a range between 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, and 80 wt%.

[0121] Optionally, the length of the battery cell is independently selected from any value or a range between any two of 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, 750mm, 800mm, 850mm, 900mm, 950mm, 1000mm, 1050mm, 1100mm, 1150mm, 1200mm, 1250mm, 1300mm, 1350mm, 1400mm, 1450mm, 1500mm, 1550mm, and 1600mm.

[0122] Optionally, the width of the battery cell is independently selected from any value or a range between any two of the following: 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, 360mm, 370mm, 380mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm, 460mm, 470mm, 480mm, 490mm, and 500mm.

[0123] Optionally, the thickness of the battery cell is independently selected from 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, 36mm, 37mm, 38mm, 39mm, 40mm, 41mm, 42mm, 43mm, 44mm, 45mm, 46mm, 47mm, 48mm, 49mm, 50mm, 51mm, 52mm, 53mm, 54mm, and 55mm. Any value or a range between any two of the following: m, 56mm, 57mm, 58mm, 59mm, 60mm, 61mm, 62mm, 63mm, 64mm, 65mm, 66mm, 67mm, 68mm, 69mm, 70mm, 71mm, 72mm, 73mm, 74mm, 75mm, 76mm, 77mm, 78mm, 79mm, 80mm, 81mm, 82mm, 83mm, 84mm, 85mm, 86mm, 87mm, 88mm, 89mm, 90mm, 91mm, 92mm, 93mm, 94mm, 95mm, 96mm, 97mm, 98mm, 99mm, 100mm.

[0124] Optionally, the length-to-thickness ratio of the battery cell is independently selected from any value or a range between any two of the following: 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150.

[0125] In some embodiments, the length of the battery cell is 200-1200 mm, the width of the battery cell is 100-300 mm, the thickness of the battery cell is 15-60 mm, and the length-to-thickness ratio of the battery cell is 5-60.

[0126] The battery cell dimensions in this embodiment can be set to obtain a long and thin battery cell, thereby improving the heat dissipation performance of the battery cell and thus improving the fast charging performance of the battery cell.

[0127] In some embodiments, the negative electrode includes a negative electrode tab and a negative electrode membrane, and the width W of the negative electrode tab, the height H1 of the negative electrode membrane, and the length L1 of the negative electrode membrane satisfy the following relationship: 0.04 mm / cm 2 ×H1×L1≤W≤1.40mm / cm 2 ×H1×L1.

[0128] For a stacked battery cell, the width W of the negative electrode tab is the sum of the widths of all negative electrode tabs on a single negative electrode sheet. A single negative electrode sheet can have one or more negative electrode tabs; for example, a single negative electrode sheet may have one negative electrode tab or three negative electrode tabs. Multiple negative electrode tabs can have the same width. Regarding the negative electrode tab, when it is located on the long side of the negative electrode film, its width direction is parallel to the length direction of the negative electrode film; when it is located on the short side of the negative electrode film, its width direction is parallel to the width direction of the negative electrode film.

[0129] In related technologies, a smaller width W and a larger H1×L1 of the negative electrode tab result in a relatively small overcurrent area, which in turn creates an overcurrent bottleneck at the negative electrode tab, increasing ohmic resistance and reducing the fast charging efficiency of the battery cell under high current. On the other hand, a larger width W and a smaller H1×L1 of the negative electrode tab result in excessive redundancy in the width and overcurrent area of ​​the negative electrode tab, increasing the weight of the battery cell and thus reducing its energy density.

[0130] Therefore, by adjusting the dimensions of the negative electrode tab and the negative electrode film, the heat dissipation and current carrying capacity of the tab and other current-carrying components can be improved, thereby increasing the charging and discharging efficiency of the battery cell.

[0131] In some embodiments, to better improve the heat dissipation and current carrying capacity of current-carrying components such as tabs, thereby improving the charging and discharging efficiency of a single battery cell, the negative electrode includes a negative electrode tab and a negative electrode film. The width W of the negative electrode tab, the height H1 of the negative electrode film, and the length L1 of the negative electrode film satisfy the following relationship: 0.05 mm / cm 2 ×H1×L1≤W≤1.20mm / cm 2 ×H1×L1.

[0132] In some embodiments, the first lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, and lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide.

[0133] The first lithium salt in this embodiment is a lithium salt containing sulfonylimide groups. The stable sulfonyl groups in the sulfonylimide group help improve the overall stability of the molecule. Under high temperature conditions, these groups can resist decomposition and maintain the integrity of the lithium salt. In humid environments or aqueous electrolytes, these groups also remain relatively stable, thereby reducing the HF produced by the reaction of the electrolyte salt with trace amounts of water, thus reducing the acidity in the electrolyte and improving the stability of the battery cell. Furthermore, the chemical bonds and molecular structure in the sulfonylimide group also possess a certain degree of chemical stability, making it less prone to oxidation, reduction, and other chemical reactions when in contact with water, thereby improving its water resistance. Therefore, sulfonylimide lithium salts can better reduce the acid rise of the electrolyte and also have a higher decomposition temperature. Thus, when used in electrolytes, they can improve the stability of the electrolyte and increase the cycle life of the battery cell.

[0134] In some embodiments, the second lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

[0135] In the embodiments of this application, both the first and second lithium salts contain fluoride ions with strong electron-withdrawing ability, which weakens the coordination effect between cations and anions in the lithium salt, making the lithium ions more mobile and improving the ionic conductivity of the electrolyte. Furthermore, the second lithium salt contains more fluoride ions, resulting in a more significant ionic conductivity when used in the electrolyte; while the sulfonylimide group in the first lithium salt exhibits better thermal stability, chemical stability, and hydrolysis resistance. Additionally, the second lithium salt can react with the current collector to form a passivation film, reducing the possibility of corrosion of the current collector. Therefore, when the first and second lithium salts are mixed in a specific ratio for use in the electrolyte, the electrolyte can possess both high ionic conductivity and high stability.

[0136] In the embodiments of this application, the types of the first and second lithium salts can be detected using methods commonly used in the art, such as ion chromatography (IC). As an example, freshly prepared electrolyte can be collected first, or electrolyte can be obtained from a single battery cell, and then tested according to JY / T-020. Finally, the anions of lithium salts in the electrolyte are detected and quantified by ion chromatography.

[0137] In some embodiments, in order to enable the electrolyte to better balance high ionic conductivity and high stability, the lithium salt includes lithium bisfluorosulfonamide and lithium hexafluorophosphate in a mass ratio of 1:10 to 4:1.

[0138] In some embodiments, in order to enable the electrolyte to better balance high ionic conductivity and high stability, the thermal decomposition temperature of the first lithium salt is 150–600°C.

[0139] In some embodiments, the thermal decomposition temperature of the second lithium salt is 60–200°C.

[0140] Optionally, the thermal decomposition temperature of the first lithium salt is independently selected from 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, and 370℃. The value or a range between any two of the following: ℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, and 600℃.

[0141] Optionally, the thermal decomposition temperature of the second lithium salt is independently selected from any value or a range between any two of 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C.

[0142] The thermal decomposition temperatures of the first and second lithium salts in this application embodiment can be detected using methods commonly used in the art. As an example, freshly prepared electrolyte, or electrolyte obtained from a single battery cell, is first collected and tested using ion chromatography (IC) according to JY / T-020. Finally, the lithium salt anions in the electrolyte are detected by ion chromatography to qualitatively identify the first and second lithium salts. Based on the qualitative results, pure substances of the first or second lithium salt are synthesized or purchased, and the thermal decomposition temperature is obtained through DSC characterization analysis. As another example, the electrolyte can be evaporated under vacuum to remove the solvent, yielding the lithium salt; this is then characterized by DSC or TGA analysis.

[0143] In other embodiments, in order to enable the electrolyte to better balance high ionic conductivity and high stability, the chemical stability and hydrolysis resistance of the first lithium salt are superior to those of the second lithium salt. The chemical stability of the two lithium salts can be compared by comparing their oxidation potential or reduction potential under the same solvent and lithium salt concentration.

[0144] In some embodiments, the concentration of the first lithium salt is 0.1 to 0.5 mol / L.

[0145] In some embodiments, the concentration of the second lithium salt is 0.5 to 1.5 mol / L.

[0146] In this embodiment, when a first lithium salt and a second lithium salt of suitable concentration are mixed in the electrolyte, the high stability of the first lithium salt and the high ionic conductivity of the second lithium salt can be better utilized, so that the electrolyte has both high ionic conductivity and high stability. At the same time, when a first lithium salt and a second lithium salt of suitable concentration are mixed in the electrolyte, the overall lithium salt concentration in the electrolyte can be kept within a suitable range, thereby reducing the possibility of increased electrolyte viscosity due to excessive lithium salt concentration.

[0147] Optionally, the first lithium salt concentration is independently selected from any value or a range between 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L, and 0.50 mol / L.

[0148] Optionally, the concentration of the second lithium salt is independently selected from any value or a range between 0.50 mol / L, 0.55 mol / L, 0.60 mol / L, 0.65 mol / L, 0.70 mol / L, 0.75 mol / L, 0.80 mol / L, 0.85 mol / L, 0.90 mol / L, 0.95 mol / L, 1.00 mol / L, and 1.50 mol / L.

[0149] In some embodiments, in order to better improve the dissociation and movement of lithium ions and improve the stability of the electrolyte, the cyclic carbonate includes one or more of ethylene carbonate (EC), propylene carbonate (PC), and γ-butyrolactone (γ-BL).

[0150] In some embodiments, in order to better reduce the viscosity of the electrolyte, the linear carboxylic acid ester includes one or more of ethyl acetate (EA), propyl acetate (PA), methyl formate (MF), methyl acetate (MA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).

[0151] In some embodiments, the sulfonate additives include one or more of 1,3-propanesulfonate lactone, propenyl-1,3-propanesulfonate lactone, 1,3-sulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, and methylene disulfonate.

[0152] When the sulfonate ester additives of this application are used as electrolyte additives in battery cells, they can form stable CEI and SEI films on the electrode surface. These interfacial films can effectively prevent direct contact between the electrode material and the electrolyte, thereby reducing interfacial reactions. This barrier effect can reduce interfacial impedance, making lithium ion transport between the electrode and the electrolyte smoother. Simultaneously, the sulfonate ester additives of this application have a high dielectric constant, which can promote the solubility and ionization of the first and second lithium salts, thereby increasing the lithium ion migration rate. Furthermore, the sulfonate ester additives of this application can also form complexes with metal ions, reducing the possibility of metal ion deposition and precipitation, further reducing interfacial impedance.

[0153] The sulfonate additives in this application embodiment can also work synergistically with the first lithium salt to jointly inhibit the decomposition and gas generation reaction of the electrolyte, thereby reducing the accumulation of by-products on the interface, improving the cleanliness and stability of the interface film, and achieving the purpose of reducing interface impedance.

[0154] In some embodiments, the electrolyte may further include one or more of unsaturated cyclic carbonate additives and dehydration and deacidification additives.

[0155] The sulfonate additives in this application embodiment can work synergistically with unsaturated cyclic carbonate additives to jointly reduce interfacial impedance.

[0156] In some embodiments, unsaturated cyclic carbonate additives include one or more of vinylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

[0157] The unsaturated cyclic carbonates of this application embodiment can undergo a reduction reaction preferentially over other solvents in the electrolyte on the negative electrode surface, forming a dense and stable SEI film. This SEI film can effectively prevent the co-intercalation of solvent molecules and further decomposition of the electrolyte, thereby reducing lithium ion consumption and repeated SEI film repair, and improving the cycle stability and lifespan of the battery. Simultaneously, the unsaturated cyclic carbonates of this application embodiment can synergistically interact with the first lithium salt in the electrolyte, inhibiting electrolyte decomposition and gas generation reactions, thus improving electrolyte stability and extending the lifespan of battery cells when used in individual cells.

[0158] In some embodiments, the dehydration and deacidification additives include one or more of the following: additives containing isocyanate groups, additives containing isothiocyanate groups, additives containing siloxane groups, additives containing silazane groups, and additives containing phosphate groups.

[0159] In related technologies, the rapid charge and discharge capability of a single battery cell is often improved by enhancing the particle dynamics of the positive and negative electrode active materials. This is generally achieved by reducing the particle size of the positive and negative electrode active materials to shorten the solid-phase diffusion path. However, this increases the specific surface area of ​​the positive and negative electrode active materials, which means introducing more trace water into the positive and negative electrodes. At the same time, a large specific surface area increases the number of active reaction sites, thereby increasing the difficulty of water removal and further reducing the cycle life of the battery cell.

[0160] The isocyanate-containing additives in this application can remove water from the electrolyte by reacting the isocyanate group (-NCO) with water molecules in the electrolyte to generate amides. Furthermore, the isocyanate-containing additives in this application can react with electrophilic hydrogen ions through the nucleophilic center (nitrogen or oxygen atom) of the isocyanate group (-NCO). During the reaction, the hydrogen ions may attack the nitrogen or oxygen atom in the isocyanate group, leading to a change in the group structure and generating corresponding amide or urea products. These products are generally insoluble in the electrolyte, thus helping to remove acidic substances from the electrolyte. Additionally, isocyanate additives can also react directly with acidic molecules in the electrolyte, for example, with the carboxyl groups in organic acid molecules, to generate corresponding ester or amide products.

[0161] The additives containing isothiocyanate groups in this application embodiment can react with water molecules in the electrolyte through the isothiocyanate groups (-NCS) to generate corresponding thiourea substances, thereby achieving the purpose of water removal.

[0162] The additives containing siloxane groups in this application can be hydrolyzed into products such as silanols. These products can combine with water molecules, thereby reducing the water content in the electrolyte. Furthermore, the hydrolysis product silanol (Si-OH) can react with hydrofluoric acid (HF) to form silicon-fluorine bonds (Si-F) and water molecules. This reaction not only consumes the hydrofluoric acid in the electrolyte, reducing its acidity, but also generates more stable silicon-fluorine bonds, further reducing the impact of acidic substances in the electrolyte on the cycle life of the battery cells.

[0163] The additives containing silazane groups in this application embodiment can reduce the water and acid content in the electrolyte by reacting the silazane groups with water and acid.

[0164] The additives containing phosphate groups in this application can form stable SEI or CEI films in the electrolyte. These interfacial films can reduce the possibility of direct contact between the electrode material and the electrolyte, thereby reducing side reactions and water molecule penetration at the interface.

[0165] In some embodiments, to better remove trace amounts of water and acid from the electrolyte, additives containing isocyanate groups include one or more of phenyl isocyanate, hexamethylene diisocyanate, tetraisocyanosilane, 3-isocyanopropyltrimethoxysilane, isophorone diisocyanate, and 4-fluorophenyl isocyanate; additives containing isothiocyanate groups include 1-isothiocyanate-PEG3-azide; additives containing siloxane groups include one or more of (trimethylsilyl)phosphite, tris(trimethylsilane)borate, tris(trimethylsilyl)phosphite, tetravinylsilane, and tetraethynylsilane; additives containing silazane groups include one or more of heptamethyldisilazane and N,N-diethyltrimethylsilaneamine; and additives containing phosphate ester groups include triargyl phosphate.

[0166] In some embodiments, in order to better balance the high-rate charge-discharge performance and cycle life of individual battery cells, the mass percentage of unsaturated cyclic carbonate additives is 1% to 5% based on the total mass of the electrolyte; and the mass percentage of dehydration and deacidification additives is 0.01% to 2%.

[0167] Optionally, based on the total mass of the electrolyte, the mass percentage of unsaturated cyclic carbonate additives is independently selected from any value or a range between 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, and 5%.

[0168] Optionally, based on the total mass of the electrolyte, the mass percentage of the dehydration and deacidification additive is independently selected from any value or a range between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60%, 0.70%, 0.80%, 0.90%, 1.00%, 1.10%, 1.20%, 1.30%, 1.40%, 1.50%, 1.60%, 1.70%, 1.80%, 1.90%, and 2.00%.

[0169] In some embodiments, in order to better reduce interfacial impedance, the electrolyte also includes lithium salt additives, which include one or more of LiDFOB, LiBOB, LiBF4, LiPO2F2 and LiSO3F.

[0170] In some embodiments, the positive electrode sheet includes a current collector and a positive active material layer stacked together. The positive active material layer includes positive active material particles with an average particle size Dv50 of 0.2–10 μm and a specific surface area of ​​10–20 m². 2 / g.

[0171] The positive electrode active material particles with suitable particle size and specific surface area in this application embodiment can reduce the path of ions, thereby reducing the DC internal resistance (DCR). When used in battery cells, this can improve ionic conductivity and thus increase discharge power. At the same time, it can also reduce the possibility of excessive absorption of trace water due to an excessively large specific surface area.

[0172] In some embodiments, the positive electrode active material particles include first lithium iron phosphate particles and second lithium iron phosphate particles, wherein the particle size Dv50 of the first lithium iron phosphate particles is 0.2 to 5 μm and the particle size Dv50 of the second lithium iron phosphate particles is 0.8 to 10 μm.

[0173] The positive electrode active material particles with suitable particle size and specific surface area used in this application embodiment can improve ionic conductivity and thus increase discharge power in battery cells. To further improve the energy density of battery cells, this application embodiment uses a compounding of positive electrode active material particles of different sizes. This reduces the voids formed by the stacking of the positive electrode active material particles, thereby increasing the compaction density and ultimately improving the energy density.

[0174] Optionally, the average particle size Dv50 of the positive electrode active material particles is independently selected from 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, and 2.3 μm. , 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5. 0μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6.0μm, 6.1μm, 6.2μm, 6.3 μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7.0μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm The value can be any value from 7.7μm, 7.8μm, 7.9μm, 8.0μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, 9.1μm, 9.2μm, 9.3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, or any value between any two.

[0175] Optionally, the specific surface area of ​​the positive electrode active material particles is independently selected from 10 m². 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g、20m 2 Any value in / g or any range between the two.

[0176] In some embodiments, the positive electrode active material layer includes a first surface, a second surface, a first region and a second region located between the first surface and the second surface, the first surface being distributed away from the current collector, wherein the thickness of the positive electrode active material layer is denoted as H, the region from the first surface of the positive electrode active material layer to a thickness range of 0.3 to 0.7H is denoted as the first region of the positive electrode active material layer, the region from the second surface of the positive electrode active material layer to a thickness range of 0.3 to 0.7H is denoted as the second region of the positive electrode active material layer, and the average particle size Dv50 of the active material particles in the first region is smaller than that in the second region.

[0177] In this embodiment, the average particle size of the active material particles in different regions of the positive electrode active material layer is set in a gradient, so that the average particle size Dv50 of the active material particles in the first region far from the negative electrode current collector side is smaller than the average particle size Dv50 of the active material particles in the second region close to the negative electrode current collector side. That is, the active material particles in the first region with smaller particle size can accept ions from the negative electrode side first, thereby reducing the ion transport path, improving ion conductivity, and thus improving discharge power.

[0178] In some embodiments, the positive electrode active material layer further includes a binder, a conductive agent, and a surfactant.

[0179] In some embodiments, to better improve the stability and energy density of the positive electrode sheet, the positive electrode sheet includes a conductive undercoat layer and a positive electrode active material layer sequentially stacked on a current collector. The conductive undercoat layer includes a binder, a conductive agent, and a surfactant; the positive electrode active material includes lithium iron phosphate active particles, a conductive agent, a binder, and a surfactant; wherein the average particle size Dv50 of the lithium iron phosphate active particles is 0.2–5.0 μm, and the specific surface area is 10–20 g / m². 2 Conductive agents include carbon nanotubes.

[0180] In some embodiments, to better improve energy density, the coating quality CW of the positive electrode active material layer meets the following requirements: 200 / 1540.25mm. 2 ≤CW≤400 / 1540.25mm 2 The compacted density is 2–2.6 g / cm³. 3 .

[0181] In some embodiments, the negative electrode sheet includes a current collector and a negative electrode active material layer stacked together. The negative electrode active material layer includes negative electrode active material particles, which are artificial graphite with an average particle size Dv50 of 5–15 μm and a specific surface area of ​​0.5–3 m². 2 / g.

[0182] The negative electrode active material particles with suitable particle size and specific surface area in this application embodiment can reduce the path of ions, thereby reducing the DC internal resistance (DCR) of the electrode. When used in a battery cell, this can improve ionic conductivity and thus increase discharge power. Simultaneously, it can also reduce the possibility of excessive absorption of trace water due to an excessively large specific surface area.

[0183] Optionally, the average particle size Dv50 of the artificial graphite is independently selected from 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, and 7. 2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8.0μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8. 5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, 9.1μm, 9.2μm, 9.3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9. 8μm, 9.9μm, 10.0μm, 11.1μm, 11.2μm, 11.3μm, 11.4μm, 11.5μm, 11.6μm, 11.7μm, 11.8μm, 11.9μm m, 12.0μm, 12.1μm, 12.2μm, 12.3μm, 12.4μm, 12.5μm, 12.6μm, 12.7μm, 12.8μm, 12.9μm, 13.0μm The value can be any value from 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13.7μm, 13.8μm, 13.9μm, 14.0μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15.0μm, or any value between any two.

[0184] Optionally, the specific surface area of ​​the artificial graphite is independently selected from 0.5 m². 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g、2.1m 2 / g, 2.2m 2 / g, 2.3m 2 / g, 2.4m 2 / g, 2.5m 2 / g, 2.6m 2 / g, 2.7m 2 / g, 2.8m 2 / g, 2.9m 2 / g、3m 2 Any value in / g or any range between the two.

[0185] In some embodiments, in order to improve the energy density of a single battery cell, the negative electrode active material particles may further include silicon-based materials, which may include one or more of elemental silicon, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0186] In some embodiments, the mass ratio of silicon to carbon in the negative electrode active material particles is (0-10):100.

[0187] Optionally, the mass ratio of silicon to carbon in the negative electrode active material particles is independently selected from any value or a range between 0, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, and 10:100.

[0188] Introducing silicon-based materials into the negative electrode active material particles can improve the energy density of the battery cell, but the significant volume expansion of silicon during charging and discharging (up to 300% or more) reduces the stability of the negative electrode structure and the capacity of the battery cell.

[0189] To overcome this problem, embodiments of this application introduce fluoroethylene carbonate (FEC) into the electrolyte solvent. On the one hand, FEC has strong chemical stability and solvent properties, enabling it to undergo a reduction reaction on the surface of the negative electrode material during the first charge of the battery, forming a stable and dense solid electrolyte interphase (SEI) film. This SEI film is mainly composed of inorganic materials (such as LiF) and organic materials, possessing excellent ionic conductivity and electronic insulation, while also exhibiting a certain degree of elasticity, thus accommodating volume changes in the negative electrode material. On the other hand, FEC can also promote the formation of a more uniform and dense SEI film on the surface of silicon particles, further suppressing the impact of volume expansion on the structural stability of the negative electrode sheet.

[0190] In some embodiments, the negative electrode active material layer includes a first surface, a second surface, a first region and a second region located between the first surface and the second surface, with the first surface facing away from the current collector. The thickness of the negative electrode active material layer is denoted as H. The region extending from the first surface of the negative electrode active material layer to a thickness range of 0.3–0.7H is denoted as the first region of the negative electrode active material layer, and the region extending from the second surface of the negative electrode active material layer to a thickness range of 0.3–0.7H is denoted as the second region of the negative electrode active material layer. The porosity of the active material particles in the first region is larger than that in the second region. The average particle size Dv50 of the artificial graphite in the second region is 3–10 μm, and the specific surface area is 0.8–5 m². 2 / g.

[0191] This application embodiment improves the wettability of the negative electrode active material layer and increases the ionic conductivity by gradient setting of the pore size of the active material particles in different regions of the negative electrode active material layer, so that the pore size of the active material particles in the first region is larger than that in the second region.

[0192] In this application embodiment, the Dv50 of the positive electrode active material particles / negative electrode active material particles represents the particle size corresponding to a cumulative volume distribution percentage of 50%, which can be detected using methods commonly used in the art. As an example, the battery cell is disassembled to obtain the electrode sheet, which is then cut into 6mm*6mm pieces using ceramic scissors and attached to a sample stage coated with paraffin wax, with the electrode sheet slightly protruding (<1mm) from the edge of the sample stage. Appropriate polishing time and voltage are then set to polish the electrode sheet end face (ion cross-section polishing). Then, scanning electron microscopy and energy dispersive spectroscopy (SEM & EDS) are used for testing (equipment model Sigma300), according to JY / T010-1996. Finally, based on the SEM & EDS results, active material particles at different positions on the electrode sheet are selected, and Avizo image processing is used to analyze the particle size and distribution at different positions.

[0193] In this application embodiment, the specific surface area of ​​the positive electrode active material particles / negative electrode active material particles has a meaning known in the art and can be measured using instruments and methods known in the art. As an example, the electrode sheet is first subjected to ion section polishing morphology analysis (CP), and the thickness of the active material coating in the first region and the active material coating in the second region are measured respectively. Based on the measured thickness, active material particles are scraped from different positions, and an appropriate amount of active material particles are collected and then tested according to the BET standard test method; the BET standard test method refers to standard GB / T19587-2004 "Determination of Specific Surface Area of ​​Solid Materials by Gas Adsorption BET Method".

[0194] electrolyte

[0195] This application provides an electrolyte comprising a lithium salt, a solvent, and sulfonate additives. Based on the total mass of the electrolyte, the solvent accounts for 65 wt% to 85 wt%, the lithium salt accounts for 8 wt% to 15 wt%, and the sulfonate additives account for 0.1 wt% to 5 wt%. The solvent comprises 20 wt% to 35 wt% cyclic carbonates and 60 wt% to 80 wt% linear carboxylic acid esters. The lithium salt comprises a first lithium salt and a second lithium salt in a mass ratio of 1:10 to 4:1.

[0196] In improving the rapid charge / discharge capability of battery cells, many related technologies employ methods such as increasing the ionic conductivity of the electrolyte (liquid-phase mass transfer) and improving the particle kinetics of the positive and negative electrode active materials (solid-phase diffusion). Increasing ionic conductivity is generally achieved by increasing the content of low-viscosity solvents in the electrolyte; however, low-viscosity solvents typically suffer from poor electrochemical stability, inevitably reducing the cycle life of the battery cell. Improving the particle kinetics of the positive and negative electrode active materials is generally achieved by reducing the particle size to shorten the solid-phase diffusion path. However, this increases the specific surface area of ​​the positive and negative electrode active materials and the number of active reaction sites, introducing more trace water and increasing the difficulty of removal, thereby reducing the cycle life of the battery cell.

[0197] Therefore, this application embodiment designs the electrolyte formulation holistically, enabling the components in the electrolyte to synergistically enhance each other, thereby improving both high-rate charge / discharge performance and cycle life. Specifically, this application embodiment uses a mixed solvent of cyclic carbonates and linear carboxylic esters in a specific ratio as the electrolyte solvent. The cyclic carbonates have a high dielectric constant, which can improve the dissociation and migration of lithium ions, thereby increasing the ionic conductivity of the electrolyte; while the linear carboxylic esters have a low viscosity, which can reduce the adverse effects of introducing cyclic carbonates on the electrolyte viscosity; in addition, the mixing of cyclic carbonates and linear carboxylic esters in a specific ratio can balance the ionic conductivity and stability of the electrolyte. Meanwhile, by mixing first and second lithium salts with different stabilities in a specific ratio, the stability of the electrolyte can be improved by utilizing the highly stable first lithium salt, and the second lithium salt can react with the current collector to form a passivation film, reducing the possibility of the current collector being corroded by the first lithium salt. Furthermore, the interaction between the mixed lithium salts and the mixed solvent can form a stable and highly ion-conductive passivation film on the surface of the electrode sheets, reducing the impact of the poor electrochemical stability of low-viscosity solvents on the cycle life of the battery cells. Additionally, by introducing sulfonate ester additives to form a low interfacial impedance and highly stable SEI film, the impact of the generated passivation film on kinetics and cycle stability is reduced. Thus, through the overall design of the electrolyte formulation, both high-rate charge / discharge performance and cycle life of the battery cells can be balanced.

[0198] [Positive electrode plate]

[0199] 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 and comprising a positive electrode active material. 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.

[0200] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0201] As examples, positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0202] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e D f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0203] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0204] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2 O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0205] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0206] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0207] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0208] 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 polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0209] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0210] [Negative electrode plate]

[0211] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0212] The negative electrode active material may be any material known in the art that can be used in battery cells. As an example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloys.

[0213] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0214] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0215] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0216] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. 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. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0217] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0218] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0219] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0220] [Isolation membrane]

[0221] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes, while allowing metal ions to pass through. 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.

[0222] In some embodiments, the isolation membrane includes a porous base membrane and a coating located on at least one side of the porous base membrane.

[0223] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0224] In some embodiments, the coating includes a heat-resistant layer and an adhesive layer, the heat-resistant layer being disposed between the base film and the adhesive layer, the heat-resistant layer including heat-resistant particles, and the adhesive layer including organic particles.

[0225] In some embodiments, the heat-resistant particles include one or more of inorganic particles or organic particles.

[0226] In some embodiments, inorganic particles may include one or more of the following: inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ion conductivity but not storing ions, or inorganic particles capable of undergoing electrochemical reactions.

[0227] In some embodiments, inorganic particles having a dielectric constant of 5 or higher may include boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxides, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1), Pb (Mg3Nb) 2 / 3 The inorganic particles can be selected from one or more of PbTiO3 (PMN-PT) and their respective modified inorganic particles. Optionally, the modification of each inorganic particle can be chemical modification and / or physical modification.

[0228] In some embodiments, inorganic particles that are ion-conductive but do not store ions may include Li3PO4, lithium titanium phosphate (Li3PO4), etc. x1 Ti y1 (PO4)3, Lithium aluminum titanium phosphate (Li) x2 Al y2 Ti z1 (PO4)3、(LiAlTiP) x3 O y3 Type glass, lithium lanthanum titanate (Li) x4 La y4 TiO3, lithium germanium thiophosphate (Li) x5 Ge y5 P z2 S w Lithium nitride (Li) x6 N y6 SiS2 type glass Li x7 Si y7 S z3 and P2S5 type glass Lix8 P y8 S z4 One or more of the following are given: 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, 0 < z4 < 7. This can improve the ion conductivity of the separator.

[0229] In some embodiments, the inorganic particles capable of undergoing electrochemical reactions may include one or more of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.

[0230] In some embodiments, the organic particles may include at least one of a thermoplastic resin polymer, a thermosetting resin polymer, or a crosslinked polymer.

[0231] In some embodiments, the thermoplastic resin polymer may include one or more of the following: polycarbonate organic particles, polymethyl methacrylate organic particles, polyoxymethylene organic particles, polyamide organic particles, styrene-acrylonitrile copolymer, polyphenylene sulfide organic particles, polyether ether ketone organic particles, polyimide organic particles, polysulfone organic particles, polyether sulfone organic particles, polyphenylene sulfone organic particles, polybenzimidazole organic particles, polyamide-imide organic particles, and polyethyleneimine organic particles.

[0232] In some embodiments, the thermosetting resin polymer may include one or more of the following: phenolic resin organic particles, polymer particles containing triazine ring structural units, epoxy resin organic particles, unsaturated polyester resin organic particles, urea-formaldehyde resin organic particles, and furan resin organic particles.

[0233] In some embodiments, the crosslinking polymer may include one or more of crosslinked styrene organic particles and silicon-containing organic crosslinked resin particles.

[0234] In some embodiments, the coating includes an adhesive, which may include, but is not limited to, one or more of polyacrylate adhesives, nitrile rubber adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0235] In some embodiments, the coating may further include a dispersant, such as one or more of alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants, including but not limited to. For example, the dispersant may include one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0236] Example

[0237] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0238] Examples 1-7, Comparative Examples 1-7

[0239] 1. Electrolyte preparation:

[0240] In an argon-filled glove box with a water content of less than 10 ppm and an oxygen content of less than 1 ppm, a certain amount of cyclic carbonate and linear carboxylic acid ester are weighed based on the total mass of the electrolyte and mixed evenly.

[0241] Then, a certain amount of lithium salt is added based on the total mass of the electrolyte to obtain a mixed solution;

[0242] Then, a certain amount of lithium salt additive, sulfonate additive, unsaturated cyclic carbonate additive and dehydration and deacidification additive are added to the mixed solution in sequence, and the mixture is mixed evenly to obtain the electrolyte.

[0243] The electrolyte formulation parameters for Examples 1-7 and Comparative Examples 1-7 are shown in Table 1 below.

[0244] 2. Preparation of the positive electrode sheet:

[0245] Lithium iron phosphate active material particles, PVDF (polyvinylidene fluoride) binder, and CNT (carbon nanotube) conductive agent are mixed in a mass ratio of 97.6:1.8:0.6, and a certain amount of NMP (N-methylpyrrolidone) solvent is added. The mixture is stirred to form a uniform slurry. The slurry is then uniformly coated onto the current collector using a coating device. After drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0246] 3. Preparation of the negative electrode sheet:

[0247] The negative electrode active material graphite, the negative electrode binder styrene-butadiene rubber (SBR), the negative electrode thickener carboxymethyl cellulose sodium (CMC-Na), and the negative electrode conductive agent acetylene black are thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 96:1.5:0.5:2 to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto the surface of the negative electrode current collector copper foil, and the negative electrode sheet is prepared by drying, cold pressing, and slitting.

[0248] 4. Separating membrane:

[0249] Porous polyethylene (PE) membrane is used as the separator.

[0250] 5. Assembly:

[0251] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain a bare cell. The bare cell is placed in an outer packaging, injected with prepared electrolyte, and then subjected to processes such as encapsulation, electrolyte injection, formation, and venting to obtain a lithium-ion battery cell with a length of 300mm, a width of 101.5mm, and a thickness of 28mm.

[0252] In Example 7, the positive and negative electrode sheets were prepared using the following method:

[0253] Positive electrode sheet:

[0254] The first lithium iron phosphate active material particles, binder PVDF (polyvinylidene fluoride), and conductive agent CNT (carbon nanotubes) are mixed in a mass ratio of 97.6:1.8:0.6, and a certain amount of solvent NMP (N-methylpyrrolidone) is added and stirred to prepare a uniform first slurry.

[0255] The second lithium iron phosphate active material particles, binder PVDF (polyvinylidene fluoride), and conductive agent CNT (carbon nanotubes) are mixed in a mass ratio of 97.6:1.8:0.6, and a certain amount of solvent NMP (N-methylpyrrolidone) is added. The mixture is stirred to prepare a uniform second slurry.

[0256] Using a double-layer extrusion coating equipment, a second slurry and a first slurry are uniformly coated sequentially on the current collector. After double-sided coating, the positive electrode sheet with different regions is prepared by drying, cold pressing, and slitting. The region closer to the current collector surface is the second region, and the region farther from the current collector and coated on the surface of the second region is the first region.

[0257] Negative electrode plate:

[0258] A mixture of graphite and silicon materials as the negative electrode active material, styrene-butadiene rubber (SBR) as the negative electrode binder, carboxymethyl cellulose sodium (CMC-Na) as the negative electrode thickener, and acetylene black as the negative electrode conductive agent are thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 96:1.5:0.5:2 to form a uniform first slurry.

[0259] A mixture of graphite and silicon materials as the negative electrode active material, styrene-butadiene rubber (SBR) as the negative electrode binder, carboxymethyl cellulose sodium (CMC-Na) as the negative electrode thickener, and acetylene black as the negative electrode conductive agent are thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 96:1.5:0.5:2 to form a uniform second slurry.

[0260] Using a double-layer extrusion coating equipment, a second slurry and a first slurry are uniformly coated sequentially on the current collector. After double-sided coating, the negative electrode sheet with different regions is prepared by drying, cold pressing, and slitting. The region closer to the current collector surface is the second region, and the region farther from the current collector and coated on the surface of the second region is the first region.

[0261] Table 1 Electrolyte formulation parameters for Examples 1-7 and Comparative Examples 1-7 Wherein, EC: ethylene carbonate; EA: ethyl acetate; DMC: dimethyl carbonate; LiFSI: lithium bis(fluorosulfonyl)imide; LiPF6: lithium hexafluorophosphate; LiPO2F2: lithium difluorophosphate; DTD: ethylene sulfate; VC: ethylene carbonate; FEC: fluoroethylene carbonate; TMSB: tris(trimethylsilane)borate.

[0262] Data Analysis:

[0263] The following tests were performed on Examples 1-7 and Comparative Examples 1-7:

[0264] 1. Active material particle size test (Dv50):

[0265] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20ml of deionized water, and simultaneously incubate for 5 minutes (53KHz / 120W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0266] 2. BET test

[0267] The test method refers to the standard GB / T19587-2004 "Determination of specific surface area of ​​solid substances by gas adsorption BET method".

[0268] 3. Fast charging performance test:

[0269] At 25℃, the battery cell was charged at a constant current of 1C to the charging cutoff voltage of 3.8V, then charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to the discharge cutoff voltage of 2.0V. The actual capacity was recorded as C0.

[0270] Then, the individual battery cells are sequentially charged at constant current rates of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, 3.5C0, 4C0, and 4.5C0 until the full battery charging cutoff voltage of 3.8V or the negative terminal cutoff potential of 0V (whichever comes first). After each charging cycle, the cells are discharged at 1C0 until the full battery discharge cutoff voltage of 2.8V. The state of charge (SOC) is recorded at different charging rates until it reaches 10%, 20%, 30%...80%. By plotting the negative electrode potential corresponding to the state of charge (SOC), rate-negative electrode potential curves are generated for different SOC states. Linear fitting yields the charging rate corresponding to a negative electrode potential of 0V for each SOC state. This charging rate is the charging window for that SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC. The charging time T for a single battery cell to charge from 10% SOC to 80% SOC is calculated using the formula (60 / C20%SOC + 60 / C30%SOC + 60 / C40%SOC + 60 / C50%SOC + 60 / C60%SOC + 60 / C70%SOC + 60 / C80%SOC) × 10%. A shorter charging time T indicates better fast-charging performance of the battery cell.

[0271] 4. High-temperature cycling performance test:

[0272] Under a constant temperature environment of 45℃, the prepared battery cells were charged at a constant current of 0.5C to the upper limit voltage, then charged at a constant voltage at the upper limit voltage until the current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 1C to the lower limit voltage. This constitutes one cycle of charge and discharge. The discharge capacity at this point is recorded as the discharge capacity of the first cycle. The battery cells were subjected to cycle charge and discharge tests using the above method, and the discharge capacity after each cycle was recorded until the discharge capacity of the battery cell decreased to 80% of the discharge capacity of the first cycle. The cycle number at this point is used to characterize the cycle performance of the battery cell. The higher the cycle number of the battery cell, the better the cycle life.

[0273] 3.50% SOC DC impedance test (25℃):

[0274] Under a constant temperature environment of 25℃, the battery cells of the device were left to stand for 10 minutes, and then discharged at a constant current of 0.33C to the lower limit of the voltage used by the battery cells. After standing for 10 minutes, they were charged at a constant current of 0.33C to the upper limit voltage, and then charged at a constant voltage until the current was 0.05C. After standing for 10 minutes, they were discharged at a constant current of 0.33C to the lower limit voltage, and the discharge capacity C0 at this time was recorded. Then, they were left to stand for 10 minutes, and then charged at a constant current of 0.33C to 0.2C0. After standing for 10 minutes, they were discharged at 4C0 for 30 seconds, and the DC impedance value of the cell was calculated.

[0275] Table 2. Parameters of positive and negative electrode active materials in Examples 1-7 and Comparative Examples 1-7

[0276] Table 3. High-rate charge / discharge performance and cycle performance of individual cells in Examples 1-7 and Comparative Examples 1-7

[0277] As can be seen from Examples 1-7 and Comparative Examples 1-7, by using a suitable amount of mixed solvent (cyclic carbonate and linear carboxylic acid ester) and mixed lithium salt to prepare an electrolyte and using it in a battery cell, the synergistic effect of the electrolyte components can achieve both high-rate charge-discharge performance and cycle life.

[0278] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A battery cell, comprising a positive electrode, a negative electrode, and an electrolyte, wherein, The electrolyte comprises lithium salt, solvent, and sulfonate additives; based on the total mass of the electrolyte, the solvent accounts for 65wt% to 85wt%, the lithium salt accounts for 8wt% to 15wt%, and the sulfonate additives account for 0.1wt% to 5wt%. The solvent comprises cyclic carbonates at a mass content of 20 wt% to 35 wt% and linear carboxylic acid esters at a mass content of 60 wt% to 80 wt%. The lithium salt comprises a first lithium salt and a second lithium salt in a mass ratio of 1:10 to 4:1; The length of the battery cell is 200-1600mm, the width of the battery cell is 80-500mm, the thickness of the battery cell is 10-100mm, and the length-to-thickness ratio of the battery cell is 5-150.

2. The battery cell according to claim 1, wherein, The length of the battery cell is 200-1200mm, the width of the battery cell is 100-300mm, the thickness of the battery cell is 15-60mm, and the length-to-thickness ratio of the battery cell is 5-60.

3. The battery cell according to claim 1 or 2, wherein, The negative electrode includes a negative electrode tab and a negative electrode membrane. The width W of the negative electrode tab, the height H1 of the negative electrode membrane, and the length L1 of the negative electrode membrane satisfy the following relationship: 0.04 mm / cm 2 ×H1×L1≤W≤1.40mm / cm 2 ×H1×L1; Optionally, the negative electrode includes a negative electrode tab and a negative electrode membrane, wherein the width W of the negative electrode tab, the height H1 of the negative electrode membrane, and the length L1 of the negative electrode membrane satisfy the following relationship: 0.05 mm / cm 2 ×H1×L1≤W≤1.20mm / cm 2 ×H1×L1.

4. The battery cell according to any one of claims 1-3, wherein, The first lithium salt comprises one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, and lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide; and / or, The second lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

5. The battery cell according to any one of claims 1-4, wherein, The lithium salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate in a mass ratio of 1:10 to 4:

1.

6. The battery cell according to any one of claims 1-5, wherein, The thermal decomposition temperature of the first lithium salt is 150–600 °C; and / or, The thermal decomposition temperature of the second lithium salt is 60–200°C.

7. The battery cell according to any one of claims 1-6, wherein, The concentration of the first lithium salt is 0.1–0.5 mol / L; and / or, The concentration of the second lithium salt is 0.5–1.5 mol / L.

8. The battery cell according to any one of claims 1-7, wherein, The cyclic carbonates include one or more of ethylene carbonate, propylene carbonate, and γ-butyrolactone; and / or, The linear carboxylic acid esters include one or more of ethyl acetate, propyl acetate, methyl formate, methyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

9. The battery cell according to any one of claims 1-8, wherein, The sulfonate additives include one or more of 1,3-propanesulfonate lactone, propenyl-1,3-propanesulfonate lactone, 1,3-sulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, and methylene disulfonate.

10. The battery cell according to any one of claims 1-9, wherein, The electrolyte also includes one or more of unsaturated cyclic carbonate additives and dehydration and deacidification additives.

11. The battery cell according to claim 10, wherein, The unsaturated cyclic carbonate additives include one or more of vinylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

12. The battery cell according to claim 10 or 11, wherein, The dehydration and deacidification additives include one or more of the following: additives containing isocyanate groups, additives containing isothiocyanate groups, additives containing siloxane groups, additives containing silazane groups, and additives containing phosphate groups.

13. The battery cell according to claim 12, wherein, The additives containing isocyanate groups include one or more of phenyl isocyanate, hexamethylene diisocyanate, tetraisocyanate silane, 3-isocyanate propyltrimethoxysilane, isophorone diisocyanate and 4-fluorophenyl isocyanate. The additives containing isothiocyanate groups include 1-isothiocyanate-PEG3-azide; The additives containing siloxane groups include one or more of (trimethylsilyl) phosphite, tri(trimethylsilane)borate, tri(trimethylsilyl) phosphite, tetravinylsilane, and tetraethynylsilane; The additive containing silazane groups includes one or more of heptamethyldisilazane and N,N-diethyltrimethylsilaneamine; The additive containing phosphate ester groups includes triargyl phosphate.

14. The battery cell according to any one of claims 10-13, wherein, Based on the total mass of the electrolyte, the unsaturated cyclic carbonate additive accounts for 1% to 5% of the mass; the dehydration and deacidification additive accounts for 0.01% to 2% of the mass.

15. The battery cell according to any one of claims 1-14, wherein, The positive electrode sheet includes a current collector and a positive active material layer stacked together. The positive active material layer includes positive active material particles with an average particle size Dv50 of 0.2–10 μm and a specific surface area of ​​10–20 m². 2 / g; and / or, The negative electrode sheet includes a current collector and a negative electrode active material layer stacked together. The negative electrode active material layer includes negative electrode active material particles, which are artificial graphite. The artificial graphite has an average particle size Dv50 of 5–15 μm and a specific surface area of ​​0.5–3 m². 2 / g.

16. The battery cell according to claim 15, wherein, The positive electrode active material particles include first lithium iron phosphate particles and second lithium iron phosphate particles. The particle size Dv50 of the first lithium iron phosphate particles is 0.2 to 5 μm, and the particle size Dv50 of the second lithium iron phosphate particles is 0.8 to 10 μm.

17. The battery cell according to claim 15 or 16, wherein, The positive electrode active material layer includes a first surface, a second surface, a first region and a second region located between the first surface and the second surface. The first surface is distributed away from the current collector. The thickness of the positive electrode active material layer is denoted as H. The region from the first surface of the positive electrode active material layer to a thickness range of 0.3 to 0.7H is denoted as the first region of the positive electrode active material layer. The region from the second surface of the positive electrode active material layer to a thickness range of 0.3 to 0.7H is denoted as the second region of the positive electrode active material layer. The average particle size Dv50 of the active material particles in the first region is smaller than that in the second region.

18. The battery cell according to any one of claims 15-17, wherein, The positive electrode active material layer further includes a binder, a conductive agent, and a surfactant; and / or, The coating quality (CW) of the positive electrode active material layer meets the following requirement: 200 / 1540.25mm. 2 ≤CW≤400 / 1540.25mm 2 The compacted density is 2–2.6 g / cm³. 3 .

19. The battery cell according to any one of claims 15-18, wherein, The negative electrode active material particles also include silicon-based materials, which include one or more of elemental silicon, silicon-carbon composite materials, and silicon-oxygen composite materials.

20. The battery cell according to claim 19, wherein, The mass ratio of silicon to carbon in the negative electrode active material particles is (0-10):

100.

21. The battery cell according to any one of claims 15-20, wherein, The negative electrode active material layer includes a first surface, a second surface, a first region and a second region located between the first surface and the second surface. The first surface is distributed away from the current collector. The thickness of the negative electrode active material layer is denoted as H. The region extending from the first surface to a thickness of 0.3H is designated as the first region of the negative electrode active material layer, and the region extending from the second surface to a thickness of 0.3H is designated as the second region. The porosity of the active material particles in the first region is larger than that in the second region. The average particle size Dv50 of the artificial graphite in the second region is 3–10 μm, and the specific surface area is 0.8–5 m². 2 / g.

22. An electrolyte, wherein, The electrolyte comprises lithium salt, solvent, and sulfonate additives; based on the total mass of the electrolyte, the solvent accounts for 65wt% to 85wt%, the lithium salt accounts for 8wt% to 15wt%, and the sulfonate additives account for 0.1wt% to 5wt%. The solvent comprises cyclic carbonates at a mass content of 20 wt% to 35 wt% and linear carboxylic acid esters at a mass content of 60 wt% to 80 wt%. The lithium salt includes a first lithium salt and a second lithium salt with a mass ratio of 1:10 to 4:

1.

23. A battery device comprising a plurality of battery cells according to any one of claims 1-21.

24. An electrical device comprising a battery cell according to any one of claims 1-21.

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