Battery

Abstract

The embodiment of the invention provides a battery, and relates to the technical field of batteries, the battery comprises a positive plate, a negative plate and an electrolyte, the positive plate comprises a positive current collector and a positive active material layer on at least one surface of the positive current collector; the positive active material layer comprises a solid electrolyte, and the solid electrolyte comprises a titanium element; the mass percentage content of a titanium element in the positive electrode active material layer is 0.05 wt%-4wt%; the electrolyte comprises a compound as shown in a formula 1, and the mass percentage content of the compound as shown in the formula 1 in the electrolyte is 0.1 wt%-3wt%. The battery can give consideration to both low-temperature performance and high-temperature stability in a high-voltage system.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a battery. Background Technology

[0002] With the increasing demand for high-energy-density batteries from new energy vehicles and portable electronic devices, the development of lithium-ion batteries capable of stable operation at high voltages has become a research hotspot. However, there is often a contradiction between the stable operation of batteries at high voltages and the application requirements across a wide temperature range, which has become a bottleneck in the current development of battery technology.

[0003] Therefore, there is an urgent need in this field to develop a battery that can balance low-temperature performance and high-temperature stability in a high-voltage system. Summary of the Invention

[0004] This application provides a battery that can balance low-temperature performance and high-temperature stability under high-voltage conditions.

[0005] This application provides a battery, including: a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive current collector and a positive active material layer on at least one surface of the positive current collector;

[0006] The positive electrode active material layer includes a solid electrolyte, which includes titanium; the mass percentage of titanium in the positive electrode active material layer is 0.05wt%-4wt%.

[0007] The electrolyte comprises the compound shown in Formula 1, wherein the mass percentage of the compound shown in Formula 1 in the electrolyte is 0.1 wt%-3 wt%.

[0008] Formula 1;

[0009] R1-R3 are independently selected from hydrogen atoms, fluorine atoms, chlorine atoms, nitrile groups, aryl groups, heterocyclic groups, alkyl or fluoroalkyl groups with 1-5 carbon atoms, alkenyl or fluoroalkenyl groups with 1-5 carbon atoms, and alkynyl or fluoroalkynyl groups with 1-5 carbon atoms.

[0010] In some embodiments, the titanium element in the positive electrode active material layer satisfies the following relationship with the compound shown in Formula 1:

[0011] 0.1≤A / B≤20;

[0012] Wherein, A is the mass percentage of titanium in the positive electrode active material layer, and B is the mass percentage of the compound shown in Formula 1 in the electrolyte.

[0013] In some embodiments, the solid electrolyte includes at least one of lithium titanium aluminum phosphate and lithium lanthanum titanate, wherein the general formula of lithium titanium aluminum phosphate is as follows:

[0014] Where 0.2 < x < 0.8;

[0015] And / or,

[0016] The compound represented by Formula 1 includes at least one of the following compounds:

[0017] Equation 1-1; Equation 1-2;

[0018] Equation 1-3; Equation 1-4;

[0019] Equations 1-5; Equations 1-6.

[0020] In some embodiments, the particle size Dv50 of the solid electrolyte is 0.1 μm-1 μm; and / or, the specific surface area of ​​the solid electrolyte is 0.5 m² / g-200 m² / g; and / or, the mass percentage content of the solid electrolyte in the positive electrode active material layer is 0.01 wt%-15 wt%.

[0021] In some embodiments, the electrolyte further includes a first solvent and a second solvent; the first solvent includes at least one of propyl propionate, ethyl propionate, ethyl butyrate, and propyl acetate, and the second solvent includes at least one of ethylene carbonate, propylene carbonate, and diethyl carbonate.

[0022] Preferably, the first solvent has a mass percentage content of 10wt%-70wt% in the electrolyte solvent, and the second solvent has a mass percentage content of 5wt%-50wt% in the electrolyte solvent.

[0023] Preferably, the mass ratio of the first solvent to the second solvent is (0.5-8):1.

[0024] In some embodiments, the electrolyte further includes sulfur-containing additives;

[0025] The sulfur-containing additive includes at least one of 1,3-propanesulfonate lactone, dimethyl sulfate, the compound shown in Formula 2, and the compound shown in Formula 3.

[0026] Formula 2; Formula 3;

[0027] Preferably, the sulfur-containing additive has a mass percentage content of 0.5wt%-20wt% in the electrolyte.

[0028] In some embodiments, the electrolyte further includes a lithium salt additive; the lithium salt additive includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium difluorophosphate, and lithium tetrafluoroborate.

[0029] Preferably, the lithium bis(trifluoromethanesulfonyl)imide in the electrolyte has a mass percentage content of 0.1wt%-10wt%, and / or, the lithium difluorooxalateborate in the electrolyte has a mass percentage content of 0.1wt%-2wt%, and / or, the lithium difluorophosphate in the electrolyte has a mass percentage content of 0.1wt%-2wt%, and / or, the lithium tetrafluoroborate in the electrolyte has a mass percentage content of 0.1wt%-3wt%.

[0030] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a silicon-based material; the silicon-based material comprising first silicon-based particles and second silicon-based particles; the battery satisfies at least one of the following conditions:

[0031] The sphericity of the first silicon-based particle is less than 0.7;

[0032] The sphericity of the second silicon-based particle is 0.8-0.99;

[0033] The particle size Dv50 of the first silicon-based particle is 1μm-7.5μm;

[0034] The particle size Dv50 of the second silicon-based particle is 8μm-15μm;

[0035] The mass percentage of silicon in the negative electrode active material layer is 1.5wt%-30wt%.

[0036] In some embodiments, the positive electrode active material layer further includes lithium cobalt oxide material; the particle size Dv50 of the lithium cobalt oxide material is 5μm-25μm;

[0037] Preferably, the particle size Dv50 of the lithium cobalt oxide material is 7μm-20μm.

[0038] In some embodiments, the electrolyte further includes ethyl fluorophosphate;

[0039] Preferably, the ethyl fluoroacetate in the electrolyte has a mass percentage of 2wt%-50wt%;

[0040] Preferably, the fluoroethyl acetate includes at least one of ethyl monofluoroacetate, ethyl 2,2-difluoroacetate, and 2,2-difluoroethyl acetate.

[0041] The battery provided in this application embodiment, by adding a solid electrolyte to the positive electrode active material of the battery and adding the compound shown in Formula 1 to the electrolyte, can effectively improve low-temperature performance while ensuring cycle stability under high temperature and high pressure based on the synergy between the solid electrolyte and the compound shown in Formula 1. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] In the embodiments of this application, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect, without limiting their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" do not necessarily imply that they are different.

[0044] It should be noted that, in the embodiments of this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0045] To address the problem in existing technologies that low-temperature and high-temperature stability cannot be simultaneously achieved under high voltage, this application provides a battery comprising: a positive electrode, a negative electrode, and an electrolyte.

[0046] The positive electrode includes a positive current collector and a positive active material layer on at least one surface of the positive current collector, the positive active material layer including a solid electrolyte, the solid electrolyte including titanium.

[0047] Solid electrolytes are solid materials that can conduct ions (such as lithium ions and sodium ions) but not electrons.

[0048] The electrolyte includes the compound shown in Formula 1.

[0049] Formula 1;

[0050] R1-R3 are independently selected from hydrogen atoms, fluorine atoms, chlorine atoms, nitrile groups, aryl groups, heterocyclic groups, alkyl or fluoroalkyl groups with 1-5 carbon atoms, alkenyl or fluoroalkenyl groups with 1-5 carbon atoms, and alkynyl or fluoroalkynyl groups with 1-5 carbon atoms.

[0051] In the embodiments of this application, fluoroalkyl can refer to an alkyl group in which one or more hydrogen atoms in the alkyl group are replaced by fluorine atoms.

[0052] The embodiments of this application do not specifically limit the source of the solid electrolyte and the compound shown in Formula 1. Any commercially available product or product prepared by conventional preparation methods that are well known to those skilled in the art can be used.

[0053] In this embodiment, titanium in the solid electrolyte acts as a structural stabilizer and ion carrier for the solid electrolyte framework. Titanium can form a three-dimensional network structure with acid radicals in the solid electrolyte, sharing octahedral and tetrahedral vertices, thus supporting lithium ions (…). The addition of titanium-containing solid electrolytes to the cathode can effectively improve the low-temperature cycle performance of the battery by providing migration channels. However, under high temperature and high pressure (4.53°C and above), titanium ions in the solid electrolyte are easily dissolved, and titanium elements existing in the form of tetravalent titanium ions will be reduced to more active trivalent titanium ions, thereby catalyzing a series of side reactions in the electrolyte. This will also cause excessive lithium ion extraction in local areas on the surface of the cathode material, but the corresponding charge is not fully compensated by the oxidation of transition metals, resulting in lattice oxygen loss. Consequently, the cathode material undergoes structural collapse, reducing the battery's cycle stability at high temperatures.

[0054] Adding the compound shown in Formula 1 to the electrolyte allows it to form a BO-Ti coordination bond with titanium in the solid electrolyte. This inhibits the dissolution of titanium ions and the reduction of tetravalent titanium ions under high temperature and pressure, improving the stability of the solid electrolyte, reducing side reactions caused by titanium ion dissolution and reduction, and enhancing the cycle stability of the battery under high temperature and pressure. Furthermore, the low oxidation potential of the formed BO-Ti coordination bond allows it to preferentially participate in film formation at the positive electrode interface, further suppressing the reduction of tetravalent titanium ions and side reactions between the electrolyte and the positive electrode. This effectively improves low-temperature performance while ensuring cycle stability under high temperature and pressure.

[0055] In some embodiments, the mass percentage content of titanium in the positive electrode active material layer is 0.05wt%-4wt%. For example, the mass percentage content of titanium in the positive electrode active material layer can be 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, or any two of the above values. Preferably, the mass percentage content of titanium in the positive electrode active material layer is 0.1wt%-3wt%.

[0056] When the mass percentage of titanium in the positive electrode active material layer is within the above-mentioned range, it can improve low-temperature cycling performance while preventing further deterioration of high-temperature and high-pressure cycling performance. A titanium content of less than 0.05 wt% is considered... Providing too few migration channels has limited improvement on low-temperature performance. A titanium content higher than 4 wt% will affect the stability of the solid electrolyte. The higher the titanium content, the more it will exacerbate the side reactions with the electrolyte, leading to electrolyte decomposition, deterioration of the interface, and further structural collapse of the cathode material, severely reducing the battery's cycle stability at high temperatures.

[0057] In some embodiments, the compound of Formula 1 in the electrolyte has a mass percentage content of 0.1 wt% to 3 wt%. For example, the mass percentage content of the compound of Formula 1 in the electrolyte can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, or any two of the above values. Preferably, the mass percentage content of the compound of Formula 1 in the electrolyte is 0.2 wt% to 2.5 wt%.

[0058] When the mass percentage of the compound shown in Formula 1 in the electrolyte is within the above-mentioned range, it can effectively improve the high-temperature and high-pressure cycle performance of the battery. If the amount of the compound in Formula 1 added to the electrolyte is less than 0.1 wt%, its effect on inhibiting the dissolution of titanium ions and the reduction of titanium ions under high temperature and high pressure is not significant, and it cannot effectively improve the cycle stability of the battery under high temperature and high pressure. If the amount added is greater than 3 wt%, the compound in Formula 1 cannot be completely dissolved in the electrolyte, affecting the quality of the electrolyte, increasing charge transfer impedance, and deteriorating low-temperature performance.

[0059] In some embodiments, the solid electrolyte includes at least one of lithium aluminum titanium phosphate (LATP) and lithium lanthanum titanate.

[0060] The general formula of the lithium titanium aluminum phosphate is as follows:

[0061] , where 0.2 < x < 0.8.

[0062] As the x value increases, the structure of LATP becomes more compact, and the lithium-ion transport path is more optimized. Too low a x value and too high a Ti value are detrimental to the stability of the cathode interface under high temperature and pressure; too high a x value... exist The solid solubility in the NASICON structure is limited, which disrupts the stability of the crystal structure, induces the precipitation of impurity phases, and blocks the lithium-ion migration channels, resulting in a decrease in ionic conductivity and adversely affecting low-temperature performance.

[0063] In some embodiments, the compound represented by Formula 1 includes at least one of the following compounds:

[0064] Equation 1-1; Equation 1-2;

[0065] Equation 1-3; Equation 1-4;

[0066] Equations 1-5; Equations 1-6.

[0067] When the compound shown in Formula 1 includes the above-mentioned compound, it can be better matched with the solid electrolyte, further improving the high-temperature cycling performance while ensuring the low-temperature cycling performance of the battery.

[0068] When the compound shown in Formula 1 is a mixture of the aforementioned compounds, the present invention does not impose specific limitations on the proportions between the individual compounds.

[0069] In some embodiments, the titanium element and the compound shown in Formula 1 satisfy the following relationship:

[0070] 0.1≤A / B≤20.

[0071] Wherein, A is the mass percentage of titanium in the positive electrode active material layer, and B is the mass percentage of the compound shown in Formula 1 in the electrolyte.

[0072] Preferably, 0.3 ≤ A / B ≤ 15.

[0073] For example, A / B can be a range consisting of any two values ​​of 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1, 1.5, 2, 3, 4, 5, 7, 9, 10, 12, 14, 16, 18, 20 or more.

[0074] By limiting the content of titanium and the compound shown in Formula 1 to the above range, the titanium and the compound shown in Formula 1 can be better coordinated, improving both the low-temperature cycle performance and high-temperature cycle performance of the battery. If the A / B ratio is too high, it indicates that the titanium content is relatively too high, or the content of the compound shown in Formula 1 is relatively too low. In this case, the oxidation of tetravalent titanium ions under high temperature and pressure cannot be effectively suppressed, and high-temperature cycle performance cannot be guaranteed. If the A / B ratio is too low, it indicates that the titanium content is too low, or the content of the compound shown in Formula 1 is relatively too high. This will increase the battery impedance, making lithium ion migration difficult, and failing to guarantee the low-temperature cycle performance of the battery.

[0075] In some embodiments, the particle size Dv50 of the solid electrolyte is 0.1 μm-1 μm, for example, 0.1 μm, 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 μm, or any two of the above values.

[0076] When the particle size of the solid electrolyte is controlled within the above-mentioned range, the solid electrolyte can provide more active sites, thereby improving lithium-ion transport efficiency, increasing ionic conductivity, and further enhancing the low-temperature cycling performance of the battery. Solid electrolyte particle sizes smaller than 0.1 μm are prone to side reactions with the electrolyte, which is detrimental to improving high-temperature cycling performance. Excessively large solid electrolyte particle sizes lead to high porosity of the sintered body, huge grain boundary and interfacial impedance, severely reducing overall ionic conductivity and diminishing the improvement in low-temperature performance.

[0077] In some embodiments, the specific surface area of ​​the solid electrolyte is 0.5 m² / g to 200 m² / g, for example, 0.5 m² / g, 1 m² / g, 10 m² / g, 30 m² / g, 50 m² / g, 100 m² / g, 150 m² / g, 200 m² / g, or any range of two of the above values.

[0078] Preferably, the specific surface area of ​​the solid electrolyte is 1.5 m² / g to 40 m² / g, for example, 1.5 m² / g, 5 m² / g, 10 m² / g, 15 m² / g, 20 m² / g, 25 m² / g, 35 m² / g, 40 m² / g, or any two of the above values.

[0079] When the specific surface area of ​​the solid electrolyte is controlled within the above range, a reaction interface of suitable size can be provided for the cathode material and the electrolyte, thereby improving the lithium-ion transport efficiency and increasing the ionic conductivity.

[0080] In some embodiments, the mass percentage of the solid electrolyte in the positive electrode active material layer is 0.01wt%-15wt%, for example, 0.01wt%, 0.1wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, or any two of the above values.

[0081] Controlling the doping amount of solid electrolyte in the positive electrode active material layer within the above-mentioned range is beneficial to improving the stability of the positive electrode structure and interface, as well as improving electrolyte film formation, and ensuring the cycle stability and safety of the battery. In some embodiments, the electrolyte further includes a first solvent and a second solvent.

[0082] The first solvent includes a carboxylic acid ester, for example, the first solvent includes at least one of propyl propionate (PP), ethyl propionate (EP), ethyl butyrate (EB), and propyl acetate (PA).

[0083] The second solvent includes carbonates, for example, at least one of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC).

[0084] In some embodiments, the mass percentage of the first solvent in the electrolyte solvent is 10wt%-70wt%. For example, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, or any two of the above values.

[0085] In some embodiments, the mass percentage of the second solvent in the electrolyte solvent is 5wt%-50wt%, for example, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, or any two of the above values.

[0086] The first solvent has stronger antioxidant capacity than the second solvent. The solubility of the compound shown in Formula 1 in the first solvent is higher than that in the second solvent. The second solvent can help the compound shown in Formula 1 form a stable interface film (SEI / CEI film) at the electrode. Therefore, when the amount of the first solvent and the second solvent added to the electrolyte is controlled within the above range, the compound shown in Formula 1 can be fully dissolved in the electrolyte and form a stable interface film at the electrode during battery cycling, inhibiting the oxidative decomposition of the electrolyte at high temperature, thereby improving the high-temperature and low-temperature cycling performance of the battery.

[0087] In some embodiments, the mass ratio of the first solvent to the second solvent is (0.5-8):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or any range of two of the above values.

[0088] When the mass ratio of the first solvent to the second solvent is controlled within the above range, the electrolyte can simultaneously possess good resistance to high-pressure oxidation and sufficient film-forming ability, thereby further improving the high and low temperature cycle performance of the battery.

[0089] In some embodiments, the electrolyte further includes sulfur-containing additives.

[0090] In some embodiments, the sulfur-containing additive includes at least one of 1,3-propanesulfonate lactone, dimethyl sulfate, the compound shown in Formula 2, and the compound shown in Formula 3.

[0091] Formula 2; Formula 3.

[0092] In some embodiments, the sulfur-containing additive has a mass percentage content of 0.5wt%-20wt% in the electrolyte. For example, 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, or any two of the above values.

[0093] In some embodiments, the mass percentage of 1,3-propanesulfonate lactone in the electrolyte is 0.1wt%-2wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or any two of the above values.

[0094] 1,3-Propanesulfonate lactone (PS) undergoes reduction and decomposition during battery cycling to form lithium sulfite. ) and lithium alkyl sulfonate ( It can buffer the expansion stress of the negative electrode sheet and prevent the interface film of the negative electrode sheet from brittlely cracking, thereby improving the high-temperature cycle stability of the battery.

[0095] In some embodiments, the mass percentage of dimethyl sulfate (DTD) in the electrolyte is 0.1wt%-1.5wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, or any two of the above values.

[0096] Dimethyl sulfate decomposes into lithium sulfate during battery cycling. This inhibits the oxidative decomposition of the electrolyte, thereby improving the high-temperature cycle stability of the battery.

[0097] In some embodiments, the mass percentage of the compound represented by Formula 2 in the electrolyte is 0.1wt%-3wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, or any two of the above values.

[0098] The compound shown in Formula 2 can generate soluble polysulfides during battery cycling, which dynamically repair the interfacial film through electrochemical reversible reactions, ensuring the stability of the interfacial film and thus improving the high-temperature cycling performance of the battery.

[0099] Alternatively, the compound shown in Formula 2 can be called a sulfur-containing polyheterocyclic compound.

[0100] In some embodiments, the mass percentage of the compound represented by Formula 3 in the electrolyte is 0.5wt%-15wt%, for example, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, or any two of the above values.

[0101] The compound shown in Equation 3 can provide a fluorine source during battery cycling ( ) and sulfonic acid group ( ), and The resulting compound, LiF, possesses high modulus and electronic insulation properties, which can inhibit the continuous decomposition of the electrolyte. Groups participate in formation This enhances the mechanical strength of the interfacial film, thereby adapting to the volume changes of the negative electrode and ensuring high-temperature cycling stability.

[0102] In some embodiments, the electrolyte further includes lithium salt additives.

[0103] The lithium salt additives include lithium bis(trifluoromethanesulfonylimide) (LiTFSI), lithium difluorooxalate borate (LiDFOB), and lithium difluorophosphate (LiTFSI). Lithium tetrafluoroborate () At least one of the following.

[0104] In some embodiments, the lithium bis(trifluoromethanesulfonyl)imide in the electrolyte has a mass percentage content of 0.1 wt% to 10 wt%. For example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, or any range of two of the above values.

[0105] In some embodiments, the lithium difluorooxalate borate has a mass percentage content of 0.1wt%-2wt% in the electrolyte. For example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or any two of the above values.

[0106] In some embodiments, the lithium difluorophosphate has a mass percentage content of 0.1wt%-2wt% in the electrolyte. For example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or any two of the above values.

[0107] In some embodiments, the lithium tetrafluoroborate in the electrolyte has a mass percentage content of 0.1wt%-3wt%. For example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, or any two of the above values.

[0108] LiTFSI exhibits high high-temperature stability, and both it and LiDFOB can form a stable LiF anode interface at high temperatures, reducing high-temperature desolvation resistance and ensuring high-temperature cycling stability.

[0109] Lithium difluorophosphate Groups can weaken It interacts with the solvent, lowering the desolvation energy barrier, while lithium tetrafluoroborate... Promote low temperature Therefore, adding appropriate amounts of lithium difluorophosphate and / or lithium tetrafluoroborate to the electrolyte can reduce impedance and improve the low-temperature performance of the battery.

[0110] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer on at least one surface of the negative current collector, the negative active material layer comprising a silicon-based material.

[0111] In some embodiments, the silicon-based material includes silicon-carbon materials and / or silicon-oxygen materials. Preferably, the silicon-based material includes silicon-carbon materials. The silicon-carbon material comprises a porous carbon matrix and silicon particles dispersed within the porous carbon matrix.

[0112] In some embodiments, the silicon-based material comprises first silicon-based particles and second carbon-based particles.

[0113] In some embodiments, the sphericity of the first silicon-based particle is less than 0.7. For example, the sphericity of the first silicon-based particle is 0.1, 0.3, 0.5, 0.55, 0.6, 0.65, 0.69, or any two of the above values.

[0114] Optionally, the first silicon-based particle may be referred to as bulk silicon.

[0115] In some embodiments, the sphericity of the second silicon-based particle is 0.8-0.99. For example, the sphericity of the second silicon-based particle is 0.8, 0.85, 0.9, 0.95, 0.99, or any two of the above values.

[0116] Alternatively, the second silicon-based particle may be referred to as spherical silicon.

[0117] Adding silicon-based materials to the negative electrode can further improve the energy density of the battery. First-stage silicon particles have a high surface roughness and a large contact area with the binder, which can improve the mechanical strength of the electrode and result in a high theoretical capacity, but also a large expansion rate. Second-stage silicon particles have a high packing density, providing more uniform buffering against volume expansion, but have a lower capacity. Therefore, using silicon-based materials that include both first-stage and second-stage silicon particles can achieve a balance between high capacity and resistance to expansion.

[0118] Sphericity testing can be performed using conventional methods in the field. For example, using image processing software (such as Image Pro Plus), at least 10 silicon-based particles can be selected from a scanning electron microscope (SEM) image of silicon-based particles at a certain magnification (e.g., 2500x). The perimeter and area of ​​each particle can be measured, and the perimeter equivalent radius r1 and area equivalent radius r2 of each particle can be calculated. The sphericity is then r2 / r1. The average value is taken to obtain the sphericity of the silicon-based particle.

[0119] In some embodiments, the mass percentage of the first silicon-based particles in the silicon-based material is 10wt%-40wt%. For example, 10wt%, 15wt%, 20wt%, 30wt%, 40wt%, or any two of the above values.

[0120] In some embodiments, the mass percentage of the second silicon-based particles in the silicon-based material is 60wt%-90wt%, for example, 60wt%, 70wt%, 80wt%, 90wt%, or any two of the above values.

[0121] By controlling the content of the first silicon-based particles and the second silicon-based particles within the above-mentioned range, the advantages of high capacity and anti-expansion can be taken into account.

[0122] In some embodiments, the particle size Dv50 of the first silicon-based particles is 1μm-7.5μm, for example, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7.5μm, or any two of the above values. Controlling the particle size of the first silicon-based particles within the above range helps to shorten the diffusion path of lithium ions, enhance the surface adhesion between the particles and the conductive agent and binder, thereby effectively improving the cycle stability and capacity retention of the battery.

[0123] In some embodiments, the particle size Dv50 of the second silicon-based particles is 8μm-15μm, for example, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any two of the above values. Controlling the particle size of the second silicon-based particles within the above range is beneficial for achieving a higher material packing density, making the electrode structure more compact, increasing the volumetric energy density, and more uniformly dispersing the volumetric expansion stress caused by the silicon material during charge and discharge, reducing damage to the electrode structure, thereby improving the cycle performance of the battery.

[0124] In some embodiments, the silicon content of the silicon-based material in the negative electrode active material layer is 1.5 wt%-30 wt%, for example, 1.5 wt%, 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any two of the above values. A low silicon content in the silicon-based material has little effect on increasing the capacity of the negative electrode, while a high silicon content leads to a sharp increase in expansion stress, which can easily cause cracking of the electrode during battery cycling. Therefore, controlling the silicon content in the silicon-based material within the above range can balance increasing capacity and reducing expansion stress.

[0125] In some embodiments, the positive electrode active material layer further includes lithium cobalt oxide material.

[0126] In some embodiments, the particle size Dv50 of the lithium cobalt oxide material is 5μm-25μm, for example, 5μm, 8μm, 10μm, 15μm, 18μm, 20μm, 22μm, 25μm, or any two of the above values.

[0127] Preferably, the particle size Dv50 of the lithium cobalt oxide material is 7μm-20μm. Specifically, it can be 7μm, 9μm, 11μm, 13μm, 16μm, 20μm, or any two of these values. This can further improve the high and low temperature cycle performance of the battery under high voltage.

[0128] In some embodiments, the electrolyte further includes ethyl fluorophosphate.

[0129] In some embodiments, the fluoroethyl acetate includes at least one of ethyl monofluoroacetate, ethyl 2,2-difluoroacetate, and 2,2-difluoroethyl acetate.

[0130] In some embodiments, the ethyl fluoroacetate in the electrolyte has a mass percentage content of 2wt%-50wt%. For example, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, or any range of two of the above values.

[0131] The fluorine atom in ethyl fluoroacetate can effectively weaken... The interaction with the solvent promotes the desolvation process at low temperatures. This solvation effect helps improve the battery's performance under low-temperature conditions, enabling the battery to maintain a high cycle discharge efficiency at lower temperatures.

[0132] It should be understood that the electrolyte of the present invention is a non-aqueous electrolyte. In addition to the first solvent and the second solvent, the electrolyte also includes organic solvents, lithium salts, and other functional additives (such as nitrile additives).

[0133] The organic solvent may also be selected from one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethyl acetate (EA), propyl acetate, n-butyl acetate, isobutyl acetate, methyl propionate (MP), methyl butyrate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (D2) and fluorinated derivatives of the above solvents. Other functional additives include one or more of vinylene carbonate (VC), ethylene ethylene carbonate (VEC), ethylene sulfate (DTD), 3-propenesulfonyl lactone (PST), fluoroethylene carbonate (FEC), tetravinylsilane (TVS), tris(trimethylsilyl)borate (TMSB), hexamethyldisilazane (HMDS), fluorobenzene (FB), and triphenyl phosphite (TPPi).

[0134] Other functional additives include nitrile additives, which include one or more of the following: benzonitrile, p-toluenenitrile, 3,5-difluorobenzonitrile, adiponitrile (AND), succinate (SN), glutaronitrile, octanoic acid nitrile, ethylene glycol bis(propionitrile) ether, 1,3,6-hexanetrionitrile (HTCN), 1,2,6-hexanetrionitrile, glycerol trinitrile, 1,2,3-tris(2-acrylonitrile ethoxy)propane, tris(2-cyanoethyl) phosphate, ethoxy(pentafluoro)cyclotriphosphazene (PFPN), pentafluoro(phenoxy)cyclotriphosphazene, etc.

[0135] In this application, the lithium salt or lithium salt additive may be selected from electrolyte lithium salts commonly used in the art, including but not limited to lithium hexafluorophosphate (LiPF6), lithium bis(oxalato)borate (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium 4,5-dicyano-2-trifluoromethylimidazolium (LiDTI), and one or more of lithium difluorobis(oxalato)borate.

[0136] In this application, the battery also includes a separator, which comprises a base membrane and a ceramic coating, wherein the coating is disposed on the base membrane. The base membrane may be selected from commonly used base membrane materials in the art, including but not limited to polyethylene (PE), polypropylene (PP), and PP and PE composite separators.

[0137] To ensure a secure adhesion of the coating to the base film, the ceramic coating comprises ceramic particles and a binder. The ceramic particles are selected from one or more of the following: alumina, boehmite, silica, zirconium dioxide, barium sulfate, magnesium hydroxide, fluorapatite, fluorophlogopite, mullite, aluminum titanate, copper oxide, titanium dioxide, and zinc oxide. The binder comprises one, two, or more of the following: polyvinylidene fluoride and polyacrylate. Single-sided or double-sided coating is performed using any one of the following coating processes: gravure coating, transfer coating, dip coating, and spray coating.

[0138] In this application, the positive electrode includes an active material, a conductive agent, and a binder. The positive electrode sheet includes a current collector and a positive electrode active material layer disposed on the surface of the current collector. The positive electrode active material layer comprises, by weight percentage, 80% to 99.8% positive electrode active material, 0.1% to 10% conductive agent, and 0.1% to 10% binder. Preferably, the positive electrode active material layer comprises, by weight percentage, 90% to 99.6% positive electrode active material, 0.2% to 5% conductive agent, and 0.2% to 5% binder.

[0139] This application uses lithium cobalt oxide as the positive electrode active material.

[0140] This application does not impose any particular limitation on the conductive agent in the positive electrode sheet, which may be selected from conductive agents commonly used in the art, including but not limited to one or more of acetylene black, conductive carbon black, Ketjen black, conductive graphite, carbon nanotubes, conductive carbon fibers, and graphene.

[0141] This application does not impose any particular limitation on the binder in the positive electrode sheet, which may be selected from binders commonly used in the art, including but not limited to one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyethylene oxide.

[0142] The negative electrode includes an active material, a conductive agent, and a binder. According to the battery of the present invention, the negative electrode active material includes a silicon-based material, and the negative electrode active material accounts for 80~98.5 wt% of the mass of the negative electrode active material layer. The conductive agent and the binder account for 0.1~10 wt% of the mass of the negative electrode active material layer, respectively.

[0143] According to the battery of the present invention, the negative electrode active material further includes a carbon-based material, which includes at least one of graphite, amorphous carbon, and graphene.

[0144] According to the battery of the present invention, the conductive agent is selected from at least one of long multi-walled carbon nanotubes, acetylene black, conductive carbon black, Ketjen black, conductive graphite, carbon nanotubes, conductive carbon fibers, and graphene.

[0145] According to the battery of the present invention, the binder is selected from at least one of polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyethylene oxide. The present invention does not particularly limit the types of conductive agents and binders in the negative electrode sheet; their selection range can be referenced to the types of conductive agents and binders in the positive electrode sheet, and will not be elaborated further here.

[0146] The lithium-ion battery provided by the present invention will be further described in detail below through specific embodiments.

[0147] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0148] Example 1

[0149] 1) Preparation of the positive electrode: Positive electrode active material LATP ( Particle size 0.4μm, specific surface area 9m² 2 The positive electrode slurry is prepared by dispersing the following ingredients in N-methylpyrrolidone at a mass ratio of 97:1.6:0.6:0.8: and stirring thoroughly to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto a safety primer, dried, rolled, and cut to obtain a positive electrode sheet with a titanium content of 0.3wt%.

[0150] 2) Preparation of negative electrode sheet: Weigh graphite, silicon-based material (sphericity 0.6, particle size Dv50 of 5μm), conductive agent carbon black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a weight ratio of 79.3:18:0.6:1.2:0.9, disperse them in an appropriate amount of deionized water, and stir thoroughly to form a uniform negative electrode slurry. Coat the negative electrode slurry onto the negative electrode current collector copper foil, and then dry, roll, and cut to obtain the negative electrode sheet. The silicon content of the negative electrode active material layer is 12%.

[0151] 3) Electrolyte preparation: In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / PC / EP / PP are mixed evenly in a mass ratio of 15 / 15 / 50 / 20. Then, fully dried lithium hexafluorophosphate is added to the mixture at 14% of the total electrolyte mass. After dissolution, add 14 wt% FEC, 0.5 wt% of Formula 1 compound, 1.5 wt% HTCN, 1 wt% ADN, and 1 wt% SN based on the total mass of the electrolyte.

[0152] 4) Separator: The diaphragm is obtained by using a gravure coating process to coat the PE diaphragm substrate with a slurry containing ceramic particles as alumina (Al2O3) and PVDF as the binder on both sides.

[0153] 5) Assembly of lithium-ion batteries: The positive electrode, negative electrode and separator are placed in sequence, with the separator in the middle of the positive and negative electrodes. Then, the electrode tabs are welded and the core is wound. The core is then placed in an aluminum-plastic film packaging bag. Then, the processes of liquid injection, formation, secondary sealing and sorting are carried out to prepare the lithium-ion battery. Finally, the electrical performance of the battery is tested.

[0154] Examples 2-11

[0155] The preparation methods of the lithium-ion batteries in Examples 2-11 are basically the same as those in Example 1. The difference is that the content of titanium in the positive electrode active material is adjusted, and the content of the compound shown in Formula 1 in the electrolyte is adjusted. The specific adjustments are shown in Table 1.

[0156] Examples 12-20

[0157] The preparation methods of lithium-ion batteries in Examples 12-20 are basically the same as those in Example 1. The difference is that the particle size and specific surface area of ​​the solid electrolyte in the positive electrode active material, the particle size of the lithium cobalt oxide material, and the contents of the first solvent and the second solvent in the electrolyte were adjusted. The specific adjustments are shown in Table 2.

[0158] Examples 21-25

[0159] The preparation methods of the lithium-ion batteries in Examples 21-25 are basically the same as those in Example 1, except that the morphology and content of silicon-based materials in the negative electrode are adjusted. The specific adjustments are shown in Table 3.

[0160] Examples 26-39

[0161] The preparation methods of the lithium-ion batteries in Examples 26-39 are basically the same as those in Example 21. The difference lies in the adjustment of the types and amounts of sulfur-containing additives, lithium salt additives and ethyl fluoroacetate in the electrolyte. The specific adjustments are shown in Table 4.

[0162] Comparative Example 1

[0163] The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that titanium is not included in the positive electrode active material.

[0164] Comparative Example 2

[0165] The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the electrolyte does not contain the compound shown in Formula 1.

[0166] Comparative Example 3

[0167] The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the content of titanium in the positive electrode active material is adjusted to 0.01 wt%.

[0168] Comparative Example 4

[0169] The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the content of titanium in the positive electrode active material is adjusted to 5wt%.

[0170] Comparative Example 5

[0171] The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the content of the compound shown in Formula 1 in the electrolyte is adjusted to 0.01 wt%.

[0172] Comparative Example 6

[0173] The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the content of the compound shown in Formula 1 in the electrolyte is adjusted to 4 wt%.

[0174] Experimental Example

[0175] The cycle performance of the lithium-ion batteries in Examples 1-39 and Comparative Examples 1-6 was tested. The specific test results are shown in Table 5.

[0176] 1. Low-Temperature Cycling Performance Test: The lithium-ion battery was placed in a 0℃ environment and left to stand for 4 hours. At a battery temperature of 0±2℃, it was discharged at 0.2C to 3.0V; left to stand for 10 minutes; then charged at a constant current of 0.34C to the upper limit voltage (4.55V), followed by charging at a constant voltage of 4.55V to 0.05C, and then discharging at a constant current of 0.5C to 3.0V, followed by a 10-minute stand. This constitutes one charge-discharge cycle, which was repeated 100 times. The highest discharge capacity of the first 3 cycles was recorded as the initial capacity Q1, and the discharge capacity of the 100th cycle was recorded as Q2. The battery capacity retention rate was calculated as Q2 / Q1 × 100%.

[0177] 2. High-Temperature Cycling Performance Test: The lithium-ion battery was placed in a 45℃ environment and allowed to stand for 10 minutes. When the battery temperature was 25±2℃, it was discharged at 0.2C to 3.0V; allowed to stand for 10 minutes; then charged at 1.5C to 4.25V (current cut off at 1.5C), then fully charged at 1.5C (cut off at 0.05C) to the upper limit voltage (4.55V), then charged at a constant voltage of 4.55V to 0.05C, followed by discharging at 1C to 3.5V, then discharging at 0.7C to 3V, and allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. 500 charge-discharge cycles were performed. The highest discharge capacity of the first 3 cycles was recorded as the initial capacity Q3, and the discharge capacity of the 500th cycle was recorded as Q4. The battery capacity retention rate was calculated as Q4 / Q3 × 100%.

[0178] Table 1

[0179]

[0180] Table 2

[0181]

[0182] Table 3

[0183]

[0184] Note: In Table 3, a sphericity or particle size of 0 for the second silicon-based particles in Example 1 indicates that Example 1 does not contain the second silicon-based particles.

[0185] Table 4

[0186]

[0187] Table 5

[0188]

[0189] After testing:

[0190] 1. As can be seen from Tables 1 and 5, compared with Comparative Examples 1-6, the lithium-ion batteries in Examples 1-11, when the positive electrode active material includes a solid electrolyte and the electrolyte includes the compound shown in Formula 1, and when the content of titanium in the positive electrode active material is limited to 0.1wt%-3wt% and the content of the compound shown in Formula 1 in the electrolyte is limited to 0.2wt%-2.5wt%, can effectively improve low-temperature performance while ensuring high-temperature cycle stability.

[0191] Furthermore, as can be seen from Examples 9-11, limiting the ratio of titanium content to the content of the compound shown in Formula 1 to 0.1-20 can improve the low-temperature cycle performance of the battery while better taking into account the high-temperature cycle performance. If the ratio is too large or too small, it will lead to the deterioration of cycle stability at high temperatures.

[0192] 2. As shown in Tables 2 and 5, limiting the particle size of the solid electrolyte in the positive electrode active material to 0.1 μm-1 μm and the specific surface area of ​​the solid electrolyte to 0.5 m² / g-200 m² / g can further improve the low-temperature cycle performance of lithium-ion batteries. Excessively large or small particle size of the solid electrolyte and / or excessively large or small specific surface area (Examples 14 and 15) will lead to a decrease in the improvement effect on low-temperature and high-temperature performance.

[0193] Furthermore, limiting the particle size of lithium cobalt oxide in the positive electrode active material to 5μm-25μm can further improve the high and low temperature cycle performance of the battery under high voltage.

[0194] Furthermore, limiting the ratio of the first solvent to the second solvent in the electrolyte to (0.5-8):1 can further improve the high and low temperature cycling performance of the battery.

[0195] 3. As shown in Tables 3 and 5, compared to Example 1, when the negative electrode active material includes first silicon-based particles and second silicon-based particles, and the sphericity of the first silicon-based particles is limited to below 0.7 and the particle size is limited to 1μm-7.5μm, and the sphericity of the first silicon-based particles is limited to 0.8-0.99 and the particle size is limited to 5μm-15μm, the low-temperature performance can be effectively improved while ensuring cycle stability at high temperatures. Furthermore, it balances high capacity and resistance to expansion, thereby improving the battery's performance.

[0196] Furthermore, by limiting the silicon content in the negative electrode active material to 1.5wt%-30wt%, it is possible to balance increasing capacity and reducing expansion stress.

[0197] 4. As shown in Tables 4 and 5, compared with Example 21, adding sulfur-containing additives to the electrolyte and limiting the content of sulfur-containing additives to 0.5wt%-20wt% can further improve the high-temperature cycle stability of the battery.

[0198] Furthermore, adding lithium salt additives to the electrolyte and limiting the content of lithium salt additives to 0.1wt%-17wt% can further improve the low-temperature cycle stability of the battery and ensure high-temperature cycle stability.

[0199] Furthermore, adding ethyl fluoroacetate to the electrolyte, and limiting the content of ethyl fluoroacetate to 2wt%-50wt%, can further improve the low-temperature cycle stability and high-temperature cycle stability of the battery.

[0200] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery, comprising: A positive electrode, a negative electrode, and an electrolyte, characterized in that the positive electrode comprises a positive current collector and a positive active material layer on at least one surface of the positive current collector; The positive electrode active material layer includes a solid electrolyte, which includes titanium; the mass percentage of titanium in the positive electrode active material layer is 0.05wt%-4wt%. The electrolyte comprises the compound shown in Formula 1, wherein the mass percentage of the compound shown in Formula 1 in the electrolyte is 0.1 wt%-3 wt%. Formula 1; R1-R3 are independently selected from hydrogen atoms, fluorine atoms, chlorine atoms, nitrile groups, aryl groups, heterocyclic groups, alkyl or fluoroalkyl groups with 1-5 carbon atoms, alkenyl or fluoroalkenyl groups with 1-5 carbon atoms, and alkynyl or fluoroalkynyl groups with 1-5 carbon atoms.

2. The battery according to claim 1, characterized in that, The titanium element in the positive electrode active material layer satisfies the following relationship with the compound shown in Formula 1: 0.1≤A / B≤20; Wherein, A is the mass percentage of titanium in the positive electrode active material layer, and B is the mass percentage of the compound shown in Formula 1 in the electrolyte.

3. The battery according to claim 1, characterized in that, The solid electrolyte includes at least one of lithium titanium aluminum phosphate and lithium lanthanum titanate, and the general formula of lithium titanium aluminum phosphate is as follows: Li1+xAlxTi2-x(PO4)3, where 0.2<x<0.8; And / or, The compound represented by Formula 1 includes at least one of the following compounds: Equation 1-1; Equation 1-2; Equation 1-3; Equation 1-4; Equations 1-5; Equations 1-6.

4. The battery according to claim 1, characterized in that, The particle size Dv50 of the solid electrolyte is 0.1 μm-1 μm; and / or, The specific surface area of ​​the solid electrolyte is 0.5 m² / g-200 m² / g; and / or, The solid electrolyte has a mass percentage content of 0.01wt%-15wt% in the positive electrode active material layer.

5. The battery according to any one of claims 1-4, characterized in that, The electrolyte further includes a first solvent and a second solvent; the first solvent includes at least one of propyl propionate, ethyl propionate, ethyl butyrate, and propyl acetate, and the second solvent includes at least one of ethylene carbonate, propylene carbonate, and diethyl carbonate. Preferably, the first solvent has a mass percentage content of 10wt%-70wt% in the electrolyte solvent, and the second solvent has a mass percentage content of 5wt%-50wt% in the electrolyte solvent. Preferably, the mass ratio of the first solvent to the second solvent is (0.5-8):

1.

6. The battery according to any one of claims 1-4, characterized in that, The electrolyte also includes sulfur-containing additives; The sulfur-containing additive includes at least one of 1,3-propanesulfonate lactone, dimethyl sulfate, the compound shown in Formula 2, and the compound shown in Formula 3. Formula 2; Formula 3; Preferably, the sulfur-containing additive has a mass percentage content of 0.5wt%-20wt% in the electrolyte.

7. The battery according to any one of claims 1-4, characterized in that, The electrolyte further includes lithium salt additives; the lithium salt additives include at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium difluorophosphate, and lithium tetrafluoroborate. Preferably, the lithium bis(trifluoromethanesulfonyl)imide in the electrolyte has a mass percentage content of 0.1wt%-10wt%, and / or, the lithium difluorooxalateborate in the electrolyte has a mass percentage content of 0.1wt%-2wt%, and / or, the lithium difluorophosphate in the electrolyte has a mass percentage content of 0.1wt%-2wt%, and / or, the lithium tetrafluoroborate in the electrolyte has a mass percentage content of 0.1wt%-3wt%.

8. The battery according to any one of claims 1-4, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a silicon-based material; the silicon-based material comprising first silicon-based particles and second silicon-based particles; the battery satisfies at least one of the following conditions: The sphericity of the first silicon-based particle is less than 0.7; The sphericity of the second silicon-based particle is 0.8-0.99; The particle size Dv50 of the first silicon-based particle is 1μm-7.5μm; The particle size Dv50 of the second silicon-based particle is 8μm-15μm; The mass percentage of silicon in the negative electrode active material layer is 1.5wt%-30wt%.

9. The battery according to any one of claims 1-4, characterized in that, The positive electrode active material layer also includes lithium cobalt oxide material; the particle size Dv50 of the lithium cobalt oxide material is 5μm-25μm. Preferably, the particle size Dv50 of the lithium cobalt oxide material is 7μm-20μm.

10. The battery according to any one of claims 1-4, characterized in that, The electrolyte also includes ethyl fluoroacetate; Preferably, the ethyl fluoroacetate in the electrolyte has a mass percentage of 2wt%-50wt%; Preferably, the fluoroethyl acetate includes at least one of ethyl monofluoroacetate, ethyl 2,2-difluoroacetate, and 2,2-difluoroethyl acetate.

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