Battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery. The battery comprises a positive plate, a negative plate and electrolyte, the positive plate comprises solid electrolyte particles, and the solid electrolyte particles comprise titanium aluminum lithium phosphate and / or lithium lanthanum titanium oxide; the electrolyte comprises non-fluorinated carboxylic ester, the non-fluorinated carboxylic ester comprises propyl propionate and / or ethyl propionate, and the mass content w1 of the non-fluorinated carboxylic ester in the electrolyte is 20%-55%; the electrolyte further comprises diethyl carbonate, the mass content of the diethyl carbonate in the electrolyte is w2, and w2 / w1 is 0.1-1.2; the electrolyte further comprises a first nitrile additive containing a carbon-carbon unsaturated bond, and the mass content w3 of the first nitrile additive in the electrolyte is 0.01%-3%; the negative plate comprises a silicon carbon material, and the silicon carbon material comprises first silicon carbon with the sphericity degree of 0.85-0.99. According to the battery, the dynamics and high-temperature performance are improved, and the lithium precipitation problem of the battery is solved.

Description

Technical Field

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

[0002] To meet the power demands of electronic products, power tools, and energy storage devices, it is necessary to further improve battery energy density. This is typically achieved by increasing the charging voltage. However, as the voltage rises, the lag in lithium-ion diffusion kinetics at the end of discharge leads to significant battery capacity loss. At this point, batteries using electrolytes with conventional carbonate solvents face insufficient kinetics at high voltages (charging cutoff voltage ≥ 4.5V), easily leading to lithium plating at the negative electrode and causing capacity loss. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and provide a battery that improves the electrolyte composition in the battery, combines the introduction of solid electrolyte in the positive electrode with a silicon-doped negative electrode system, overcomes the pain point of insufficient battery dynamics under high voltage, and improves the charge and discharge dynamics of the battery.

[0004] Using non-fluorinated carboxylic acid esters (such as propyl propionate and ethyl propionate) in the electrolyte can significantly reduce the viscosity of electrolytes containing non-fluorinated carboxylic acid esters due to their weak intermolecular forces and low viscosity. This characteristic can improve the transport performance of lithium ions in the electrolyte and thus improve the overall battery dynamics. Furthermore, the battery kinetic performance is improved by optimizing the interaction between the positive and negative electrodes and the electrolyte. Solid electrolyte particles (such as lithium titanium aluminum phosphate and lithium lanthanum titanium oxide) are introduced into the positive electrode. These solid electrolyte particles have three-dimensional lithium-ion transport channels, which endow them with high ionic conductivity. This further enhances the transport rate of lithium ions in the positive electrode and at the positive electrode-electrolyte interface, thereby improving the overall kinetic performance, alleviating lithium plating at the negative electrode, and improving the battery's cycle capacity retention. The negative electrode uses first silicon carbon with high sphericity. The low-viscosity non-fluorinated carboxylic acid ester can uniformly wet the silicon carbon particles. Combined with the high surface curvature consistency and regular morphology of the first silicon carbon, lithium ions can achieve efficient and rapid diffusion in all directions, improving the diffusion rate of lithium ions at the negative electrode and thus enhancing the kinetic performance. However, while the above strategies can significantly improve the kinetics, they will reduce the high-temperature stability of the battery to some extent. This is because the non-fluorinated carboxylic esters in the electrolyte have insufficient thermal stability, and the solid electrolyte particles in the cathode may be oxidized by oxygen released from the delithiated cathode when they come into contact with the cathode active material under high voltage, resulting in heat release and thus reducing the thermal stability of the system. At the same time, the solid electrolyte particles react with organic components such as non-fluorinated carboxylic esters in the electrolyte at high temperatures, consuming the electrolyte and generating gas, further accelerating the risk of thermal runaway. Therefore, the inventors of this invention further discovered that adding diethyl carbonate and a first nitrile additive with good thermal stability to the electrolyte can further improve the thermal stability of the electrolyte and the interface stability between the electrolyte and the positive electrode. This is because diethyl carbonate has a stable molecular structure with saturated alkyl carbon chains, exhibiting good high-temperature tolerance. The first nitrile additive, a nitrile compound containing carbon-carbon unsaturated bonds, can form a stable interfacial film at the positive electrode, reducing direct contact between the electrolyte and the positive electrode active material and solid electrolyte particles, suppressing interfacial side reactions under high voltage or high temperature, and improving the overall thermal stability of the battery. For the negative electrode, this electrolyte system not only promotes the formation of a structurally complete and dense SEI film at the negative electrode, suppressing side reactions between silicon particles and the electrolyte and restricting the volume expansion of silicon particles, thus improving battery cycle performance, but also complexes transition metal ions dissolved from the positive electrode, thereby preventing their deposition on the negative electrode surface and thus preventing them from damaging the structural stability of the negative electrode.

[0005] Based on this, the present invention proposes the following technical solution: This invention provides a battery comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode comprises solid electrolyte particles, which include lithium aluminum titanium phosphate and / or lithium lanthanum titanium oxide. The electrolyte comprises non-fluorinated carboxylic acid esters, which include propyl propionate and / or ethyl propionate. Based on the total mass of the electrolyte, the mass content of the non-fluorinated carboxylic acid ester is w1, where w1 is 20%-55%. The electrolyte further includes diethyl carbonate, and based on the total mass of the electrolyte, the mass content of diethyl carbonate is w2, and the w2 / w1 ratio is 0.1-1.2; the electrolyte further includes a first nitrile additive, which includes a nitrile compound containing carbon-carbon unsaturated bonds, and based on the total mass of the electrolyte, the mass content of the first nitrile additive is w3, and the w3 ratio is 0.01%-3%; the negative electrode includes a negative electrode active material, which includes a silicon-carbon material, and the silicon-carbon material includes a first silicon-carbon material, the sphericity of which is 0.85-0.99.

[0006] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: (1) The battery of the present invention improves the composition of electrolyte, positive electrode and negative electrode, so that the electrolyte and positive and negative electrodes are matched together to improve the dynamic performance of the battery under high voltage, reduce the problem of lithium plating on negative electrode, and improve the cycle stability of the battery.

[0007] (2) The battery of the present invention has good thermal stability at high temperature.

[0008] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Detailed Implementation

[0009] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0010] The present invention provides a battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises solid electrolyte particles, and the solid electrolyte particles comprise lithium aluminum titanium phosphate (LATP) and / or lithium lanthanum titanium oxide (LLTO).

[0011] In this invention, the electrolyte comprises a non-fluorinated carboxylic acid ester, which includes propyl propionate (PP) and / or ethyl propionate (EP). Based on the total mass of the electrolyte, the mass content of the non-fluorinated carboxylic acid ester is w1, which is 20%-55%, for example, 20%, 22%, 24%, 26%, 28%, 30%, 35%, 40%, 45%, 50%, or 55%.

[0012] In one embodiment, the non-fluorinated carboxylic acid ester includes PP, where w1 is the mass content of PP in the electrolyte.

[0013] In one embodiment, the non-fluorinated carboxylic acid ester includes EP, where w1 is the mass content of EP in the electrolyte.

[0014] In one embodiment, the non-fluorinated carboxylic acid ester includes PP and EP, where w1 is the sum of the mass contents of PP and EP in the electrolyte.

[0015] In this invention, the electrolyte further includes diethyl carbonate (DEC), and the mass content of the diethyl carbonate is w2 based on the total mass of the electrolyte, and the w2 / w1 ratio is 0.1-1.2, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1 or 1.2.

[0016] In this invention, the electrolyte further includes a first nitrile additive, which comprises a nitrile compound containing a carbon-carbon unsaturated bond.

[0017] It is understood that the carbon-carbon unsaturated bond refers to a covalent bond formed between carbon atoms by sharing multiple pairs of electrons (e.g., two or three pairs), and the carbon-carbon unsaturated bond contains a π bond.

[0018] In this invention, based on the total mass of the electrolyte, the mass content of the first nitrile additive is w3, where w3 is 0.01%-3%, for example, 0.01%, 0.02%, 0.04%, 0.06%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5% or 3%.

[0019] In one embodiment, w3 is 0.05%-2%.

[0020] In one embodiment, the first nitrile additive includes at least one of acrylonitrile, isophthalonitrile, terephthalonitrile, benzonitrile, 2-amino-1,1,3-tricyano-1-propene, and 1,4-dicyano-2-butene.

[0021] In this invention, the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a silicon-carbon material, the silicon-carbon material includes a first silicon-carbon, the sphericity of the first silicon-carbon is 0.85-0.99, for example 0.85, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98 or 0.99.

[0022] In this invention, the mass content of EP is 15%-35% based on the total mass of the electrolyte, for example, 15%, 16%, 18%, 20%, 25%, 30% or 35%.

[0023] In this invention, the mass content of PP is 0%-20% based on the total mass of the electrolyte, for example, 0%, 2%, 4%, 6%, 8%, 10%, 15% or 20%.

[0024] Lithium-ion batteries face higher kinetic requirements under high voltage, necessitating improvements to conventional battery systems to meet these demands. The electrolyte is a crucial component of the battery. Non-fluorinated carboxylic esters (such as EP and PP) possess low viscosity, which can reduce electrolyte viscosity, improve electrolyte wettability and lithium-ion migration efficiency, thereby enhancing battery kinetics. For the positive electrode, introducing solid electrolyte particles (such as LATP or lithium lanthanum titanium oxide) into the positive electrode active layer can improve battery kinetics. These solid electrolyte particles have high ionic conductivity and can more tightly fill the area around the positive electrode active material particles, increasing the contact points between particles and forming more continuous ion transport channels in the positive electrode active layer. This improves the ion conduction performance of the positive electrode, thereby enhancing battery kinetics and mitigating lithium plating at the negative electrode. However, the presence of Ti in the solid electrolyte particles... 4+ Ti is prone to dissolution at high temperatures. 4+ Easily reduced to Ti 3+ The generated Ti 4+ / Ti 3+ It can catalyze side reactions in the electrolyte, affecting the battery's high-temperature safety performance. At the same time, EP and PP have poor high-temperature stability, which will also degrade the battery's high-temperature performance.

[0025] To further improve the high-temperature stability of the battery, DEC and a first nitrile additive are added to the electrolyte. A small amount of DEC preferentially coordinates with titanium ions to form a complex, reducing the number of free titanium ions in the electrolyte. The small amount of DEC complexed with titanium ions is activated and decomposes to generate polycarbonate-like substances, which can form a denser and more stable CEI film at the positive electrode. The first nitrile additive also has a complexing effect on titanium ions, which can inhibit the dissolution of titanium ions from solid electrolyte particles and undergo a polymerization reaction on the positive electrode surface. Together with DEC, it forms a stable and robust CEI film, isolating the positive electrode material / solid electrolyte from direct contact with the electrolyte, suppressing side reactions of the solid electrolyte and the dissolution of transition metals under high voltage and high temperature, and improving the high-temperature stability of the battery.

[0026] By adjusting w2 / w1 within a suitable range, non-fluorinated carboxylic esters can reduce electrolyte viscosity and improve ion conduction efficiency, while DEC can inhibit electrolyte decomposition at high temperatures and improve interfacial stability. This achieves wide-temperature-range optimization of electrolyte performance, ensuring electrolyte kinetics and high-temperature stability. When w2 / w1 is too small (e.g., <0.1), too much non-fluorinated carboxylic ester or too little DEC is detrimental to improving the thermal stability of the electrolyte. When w2 / w1 is too large (e.g., >1.2), too little non-fluorinated carboxylic ester or too much DEC results in high overall electrolyte viscosity, reducing the lithium-ion transport rate in the electrolyte and hindering the improvement of battery kinetic performance.

[0027] The negative electrode uses a first silicon-carbon material with high sphericity. This first silicon-carbon material has a regular morphology and uniform surface curvature, allowing lithium ions to diffuse efficiently within it. Combined with a low-viscosity, high-flow electrolyte, it exhibits good wettability on the negative electrode surface, facilitating the formation of a dense, uniform SEI film. This restricts the volume expansion of silicon particles, improving the battery's cycle performance and rate capability. The electrolyte of this invention can also complex transition metal ions dissolved from the positive electrode, such as titanium ions in solid electrolyte particles or cobalt and manganese ions in the positive electrode active material, preventing transition metal ions from depositing on the negative electrode surface and thus reducing the structural stability of the negative electrode. Through overall optimization and synergistic combination of the positive electrode, negative electrode, and electrolyte, the kinetic performance and cycle stability of the silicon-doped negative electrode system under high voltage are optimized, alleviating the lithium plating problem at the negative electrode.

[0028] In this invention, the sphericity of the first silicon carbon can be obtained by conventional testing methods in the art, such as: discharging the battery to 0% SOC, disassembling and removing the negative electrode sheet, or directly removing the negative electrode sheet, polishing its cross-section with an argon ion mill, and then imaging the obtained cross-section using a scanning electron microscope (SEM) in backscatter imaging mode; analyzing the image of each silicon carbon particle in the SEM image (backscatter mode) of the negative electrode active layer at a certain magnification (e.g., 2500x) using image processing software such as Image Pro Plus, obtaining the perimeter and area of ​​each particle, calculating the perimeter equivalent radius r1 and area equivalent radius r2 of each silicon carbon particle respectively, then the sphericity of each particle S = r2 / r1, and then performing a weighted average of the sphericity of each particle to obtain the average sphericity of the silicon carbon material, and counting silicon carbon particles with a sphericity greater than or equal to 0.85 as the first silicon carbon.

[0029] In this invention, w1, w2 and w3 can all be obtained by conventional testing methods in the art, such as by gas chromatography or gas chromatography coupled with mass spectrometry.

[0030] In this invention, the chemical formula of the lithium titanium aluminum phosphate is Li. 1+x1 Al x1 Ti 2-x1 (PO4)3, 0 < x1 < 0.5 (e.g., 0.01, 0.02, 0.04, 0.06, 0.1, 0.2, 0.3, 0.4, 0.45, or 0.49), wherein the chemical formula of the lithium lanthanum titanium oxide is Li. 3-x2 La 2 / 3-x2 Ti 1-y M y O3, 0 < x2 < 2 / 3 (e.g., 1 / 15, 2 / 15, 1 / 5, 4 / 15, 1 / 3, 2 / 5 or 3 / 5), 0 ≤ y < 1 (e.g., 0, 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 0.9, 0.95 or 0.99), M includes at least one of Nb, W, Ga, Ge, Se, Ta, Zr and Hf.

[0031] In this invention, the average particle size of the solid electrolyte particles is 0.1 μm-1 μm (e.g., 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm or 1 μm).

[0032] Adjusting the average particle size of solid electrolyte particles within a suitable range allows them to have an appropriate specific surface area, increasing the contact area between solid electrolyte particles or between solid electrolyte particles and positive electrode binders, positive electrode active materials, etc. This enables the solid electrolyte particles to be well dispersed in the positive electrode active layer. When the average particle size of solid electrolyte particles is too small (e.g., <0.1μm), the specific surface area of ​​the solid electrolyte particles is large, which intensifies the side reactions with the electrolyte and is not conducive to further improving the cycle performance of the battery. On the other hand, when the average particle size of solid electrolyte particles is too large (e.g., greater than 1μm), the solid electrolyte particles cannot form a continuous lithium-ion transport network, and the effect on improving the ionic conductivity of the positive electrode is not significant, which is not conducive to further improving the kinetic performance of the battery.

[0033] In this invention, the average particle size of the solid electrolyte particles can be obtained by conventional testing methods in the art, such as the following method: discharging the battery to 0% SOC, disassembling and removing the positive electrode sheet, or directly removing the positive electrode sheet, polishing its cross-section with an argon ion milling machine, and imaging the obtained cross-section in a scanning electron microscope (SEM); finding 10 solid electrolyte particles in the region, and then using electron microscope image analysis software such as ImageJ to measure the particle size and perform distribution statistics to obtain the average particle size of the solid electrolyte particles.

[0034] In this invention, the values ​​of x1, x2, and y can be determined using conventional testing methods in the art, for example, by the following method: Take approximately 0.1g of solid electrolyte particles as a sample, add 10mL of hydrochloric acid, and digest on a 350℃ hot plate for 10min. After cooling, bring the volume to 100ml, then dilute 10 times. Take a portion of the solution and analyze it using an ICP spectrometer. After obtaining the corresponding test parameters, x1, x2, and y can be obtained by formula conversion. Alternatively, they can be determined using a combination of scanning electron microscopy and X-ray energy dispersive spectroscopy (SEM-EDS). For example, discharge the battery to empty charge at a low rate, disassemble the battery, remove the positive electrode, and process it using argon ion polishing technology to obtain a cross-sectional sample of the positive electrode. Then, test the obtained cross-section using the backscatter mode of a scanning electron microscope at a magnification of 10K. Select the middle region of a single solid electrolyte particle for EDS analysis to obtain x1, x2, and y.

[0035] In this invention, the electrolyte comprises propylene carbonate (PC), and the mass content of the propylene carbonate is w4 based on the total mass of the electrolyte, where w4 > w2.

[0036] Both PC and DEC are beneficial for improving the thermal stability of the electrolyte. PC molecules are less prone to ester bond breakage or hydrolysis at high temperatures, and have better thermal stability than DEC. Adjusting w4 > w2 can further improve the cycle stability of the battery at high temperatures and reduce the battery's gas production rate. PC can also ensure that lithium ions in the electrolyte have good dissociation performance, thereby improving the battery's charge and discharge efficiency.

[0037] In this invention, w2 is 5%-25%, for example, 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24% or 25%.

[0038] In one embodiment, w2 is 8%-20%.

[0039] The first nitrile additive and DEC can synergistically improve the high-temperature performance of the battery. The first nitrile additive can complex transition metal ions, suppress the valence change of Ti ions, and at the same time promote the formation of CEI film at the positive electrode and suppress the side reactions of the electrolyte at the positive electrode, which is conducive to further improving the cycle stability of the battery at high temperature and high voltage. DEC can improve the thermal stability of the electrolyte, reduce electrolyte drying and side reactions, and reduce the amount of gas generated at high temperature. The synergy between the two can further improve the high-temperature performance of the battery.

[0040] In this invention, w4 is 5%-28%, for example, 5%, 6%, 8%, 10%, 12%, 14%, 16%, 20%, 24% or 28%.

[0041] In this invention, the electrolyte includes a second nitrile additive, which includes butadienenitrile, adiponitrile, 1,3,6-hexanetrionitrile, 1,5-dicyanopentane, tris(2-cyanoethyl) phosphate, ethylene glycol bis(propionitrile) ether, 1,2,3,4-tetratetra(2-cyanoethoxy)butane, 1,2,4-butanetrionitrile (BTCN), 1,2,3,4,5-penta(2-cyanoethoxy)pentane, etc. (Equation 1) and At least one of (Equation 2), wherein n1, n2 and n3 are each independently an integer from 0 to 4 (e.g., 0, 1, 2, 3 or 4), and m1, m2 and m3 are each independently an integer from 1 to 4 (e.g., 1, 2, 3 or 4).

[0042] In one embodiment, (Equation 2) includes (Equation 2-1) and / or (Equation 2-2).

[0043] In this invention, based on the total mass of the electrolyte, the mass content of the second nitrile additive is w5, where w5 is 0.5%-8%, for example, 0.5%, 0.6%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%.

[0044] Based on the first nitrile additive, a second nitrile additive was further introduced. This second additive works synergistically with the first to improve the high-temperature cycle stability of the battery. The nitrile groups in the nitrile additive can complex transition metal ions (such as Ti) dissolved from the positive electrode. 4+ Co 3+ Ni 2+ Furthermore, it can further promote the formation of a nitrogen-containing CEI film at the positive electrode, suppressing direct contact between the electrolyte and the positive electrode and reducing the probability of side reactions, thus decreasing the oxidative decomposition of the electrolyte. When w5 is too low (e.g., <0.5%), it cannot effectively complex transition metal ions, which is not conducive to further improving the battery's cycle stability; when w5 is too high (e.g., >8%), excessive second nitrile additives will increase the electrolyte's impedance, which is not conducive to improving the battery's cycle performance and rate performance.

[0045] In one embodiment, the electrolyte does not include EC.

[0046] In this invention, when the electrolyte includes ethylene carbonate (EC), the mass content of the ethylene carbonate is w6 based on the total mass of the electrolyte, w6 ≤ 1%, for example, 1%, 0.9%, 0.8%, 0.6%, 0.4%, 0.2%, 0.1%, or 0.01%.

[0047] Electrolytes (EC) exhibit insufficient oxidation stability under high voltage or high temperature conditions, reacting with silicon-doped anodes to generate CO2 and H2, exacerbating battery gas production. Furthermore, electrolytes with high EC content have high viscosity, leading to the formation of an excessively thick SEI film at the anode, hindering lithium-ion transport and impacting battery cycle stability and rate performance. The electrolyte of this invention significantly reduces EC content, and an EC-free system can also be preferred. By improving the electrolyte composition, the gas production problem under high voltage / high temperature conditions is avoided, while the overall battery kinetic performance and cycle stability are improved.

[0048] In this invention, the electrolyte comprises vinylene carbonate, and the mass content of the vinylene carbonate is w7 based on the total mass of the electrolyte, where w7 is 0.01%-2%, for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%.

[0049] VC, with its lower reduction potential, preferentially undergoes a reduction reaction with the electrolyte solvent on the negative electrode surface, replacing EC in the negative electrode film formation. It synergistically forms a dense and stable SEI film with FEC in the electrolyte, reducing interfacial impedance and contributing to improved battery kinetic performance. When w7 is too high (e.g., >2%), the electrolyte viscosity increases, leading to increased impedance, which is detrimental to the rapid migration of lithium ions and reduces the battery's rate performance.

[0050] In this invention, the electrolyte includes a sulfur-containing additive, which includes at least one of 1,3-propanesulfonate lactone, vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate.

[0051] In this invention, based on the total mass of the electrolyte, the mass content of the sulfur-containing additive is w8, where w8 is 0.1%-5%, for example, 0.1%, 0.2%, 0.4%, 0.6%, 1%, 2%, 3%, 4% or 5%.

[0052] In one embodiment, w8 is 0.5%-4%.

[0053] Furthermore, introducing sulfur-containing additives into the electrolyte can form an SO2-containing SEI film on the negative electrode surface. The strongly polar sulfonyl group (-SO2) can preferentially react with Li. + Coordination reduces Li + The activation energy required for desolvation of Li + It can participate in the negative electrode reaction more efficiently, thereby improving the kinetic performance of the battery.

[0054] In this invention, the electrolyte comprises fluoroethylene carbonate (FEC), and the mass content of the fluoroethylene carbonate is w9 based on the total mass of the electrolyte, where w9 is 5%-25%, for example, 5%, 6%, 8%, 10%, 12%, 14%, 16%, 20%, 24% or 25%.

[0055] When the EC content in the electrolyte is low or there is no EC, the formation of the SEI film on the negative electrode can be promoted by further introducing FEC. When w9 is too high (e.g., >25%), it is not conducive to improving the kinetic performance of the electrolyte and the decomposition of FEC cannot be avoided at high temperatures, resulting in gas production in the battery. When w9 is too low (e.g., <5%), the formation of the SEI film cannot be further promoted, and the further protection effect on the negative electrode is not obvious.

[0056] In this invention, w1, w2, w3, w4, w5, w6, w7, w8 and w9 can all be obtained by conventional testing methods in the art, such as by gas chromatography, liquid chromatography or gas chromatography coupled with mass spectrometry.

[0057] In this invention, the silicon-carbon material further includes a second silicon-carbon.

[0058] In this invention, the average particle size of the first silicon carbide is 1μm-15μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 8μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm.

[0059] In this invention, the sphericity of the second silicon carbon is 0.25-0.75, for example, 0.25, 0.26, 0.28, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7 or 0.75; the average particle size of the second silicon carbon is 5μm-15μm, for example, 5μm, 6μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm.

[0060] In one embodiment, the silicon-carbon material comprises a first silicon-carbon and a second silicon-carbon.

[0061] The smaller sphericity of the second silicon-carbon material is beneficial for optimizing the packing density, increasing the compaction density of the negative electrode sheet, and reducing the thickness of the SEI film. When a mixture of first and second silicon-carbon materials is used, the packing between the first and second silicon-carbon materials is more compact, the bonding force with the negative electrode binder is enhanced, and the volume expansion is further mitigated, local stress concentration is reduced, and the overall compressive strength is improved. This reduces particle shedding and breakage, improves rate performance, increases K-value yield, and improves the stability of the electrode structure at high temperatures.

[0062] Adjusting the average particle size of the first and second silicon-carbon materials within a suitable range can be combined with sphericity to further enhance the kinetics of silicon-carbon materials, alleviate expansion stress, and improve battery cycle performance. Using the first and second silicon-carbon materials together can reduce the adverse effects of volume changes during charging, optimize packing density, increase negative electrode compaction density, and improve battery volumetric energy density. It can also regulate the SEI film structure, improve lithium-ion diffusion kinetics, enhance rate performance, and improve battery cycle stability at high temperatures.

[0063] When the first silicon-carbon and the second silicon-carbon are combined with the electrolyte system and the cathode system of the present invention, on the one hand, EP / PP improves the fluidity of the electrolyte and optimizes the wettability of the electrolyte on the surface of the negative electrode active material, further promoting the formation of the SEI film, which is beneficial to improving the battery dynamic performance; on the other hand, it can also optimize the stability of the electrolyte under high voltage, alleviate the side reactions between the silicon-doped negative electrode and the electrolyte, and improve the cycle stability and rate performance of the battery while ensuring high energy density, and reduce the risk of lithium plating; on the other hand, the introduction of solid electrolyte particles into the cathode improves the ionic conductivity of the cathode sheet, and together with the highly fluid electrolyte and the silicon-doped negative electrode, ensures the stability and dynamic performance of the battery under high voltage.

[0064] In this invention, the sphericity of the second silicon carbon can be obtained by conventional testing methods in the art, such as: discharging the battery to 0% SOC, disassembling and removing the negative electrode sheet, or directly removing the negative electrode sheet, polishing its cross-section with an argon ion mill, and then imaging the obtained cross-section using a scanning electron microscope (SEM) in backscatter imaging mode; analyzing the image of each silicon carbon particle in the SEM image (backscatter mode) of the negative electrode active layer at a certain magnification (e.g., 2500x) using image processing software such as Image Pro Plus, obtaining the perimeter and area of ​​each particle, calculating the perimeter equivalent radius r1 and area equivalent radius r2 of each silicon carbon particle respectively, then the sphericity of each particle S = r2 / r1, and then performing a weighted average of the sphericity of each particle to obtain the average sphericity of the silicon carbon material, and counting silicon carbon particles with a sphericity less than or equal to 0.75 as the second silicon carbon.

[0065] In this invention, the average particle size of the first silicon carbon and the second silicon carbon can be obtained by conventional testing methods in the art, such as: discharging the battery to 0% SOC, disassembling and removing the negative electrode, or directly removing the negative electrode, polishing its cross-section with an argon ion mill, and then imaging the obtained cross-section using a backscattering imaging mode on a scanning electron microscope (SEM) device; the silicon carbon particles in the image appear grayish-white, and then the particle size is measured and the distribution is statistically analyzed using electron microscope image analysis software such as ImageJ to obtain the average particle size of the silicon carbon material, and the first silicon carbon and the second silicon carbon are distinguished by the size of sphericity and the average particle size is statistically analyzed.

[0066] In this invention, the battery includes a separator, the separator including a base film and a functional coating located on at least one side of the base film.

[0067] In one embodiment, the diaphragm includes a base membrane and a functional coating located on one side of the base membrane.

[0068] In yet another embodiment, the diaphragm includes a base membrane and functional coatings located on both sides of the base membrane.

[0069] In this invention, the thickness of the functional coating is 0.3μm-5μm, for example, 0.3μm, 0.4μm, 0.6μm, 1μm, 1.5μm, 2μm, 3μm, 4μm or 5μm.

[0070] In this invention, the functional coating includes a first particle, which includes at least one of alumina, boehmite, alumina, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, and barium titanate.

[0071] In one embodiment, the first particle comprises at least one of melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, and melamine thiocyanate.

[0072] In this invention, the particle size Dv50 of the first particle is D, which is 0.05μm-2μm, for example, 0.05μm, 0.06μm, 0.08μm, 0.1μm, 0.2μm, 0.4μm, 0.6μm, 1μm, 1.5μm or 2μm.

[0073] In this invention, w3 / D is 0.002-0.3, for example, 0.002, 0.004, 0.006, 0.008, 0.01, 0.02, 0.04, 0.08, 0.1, 0.15, 0.2, 0.25 or 0.3.

[0074] Adjusting w3 / D within a suitable range ensures that the first nitrile additive can smoothly penetrate the gaps between the first particles when the electrolyte wets the separator, participating in the electrode interface film formation and further improving the lithium-ion transport rate and thermal safety performance. When w3 / D is too large (e.g., >0.3), the gaps between the first particles are too small, the electrolyte viscosity is too high, or the first nitrile additive in the electrolyte agglomerates, reducing the rate at which the electrolyte cannot permeate the separator, which is detrimental to further improving the battery's kinetic performance. When w3 / D is too small (e.g., <0.002), the gaps between the first particles increase, but the first nitrile additive is insufficient, resulting in poor CEI film formation at the positive electrode, uneven interfacial film on the electrode surface, and exacerbation of local side reactions leading to electrolyte decomposition and gas and acid production, causing the positive electrode active material structure to collapse, which is detrimental to further improving the battery's cycle stability.

[0075] In this invention, the particle size Dv50 of the first particle can be obtained by conventional testing methods in the art, such as by SEM, specifically as follows: discharge the battery to 0% SOC, disassemble and remove the separator, cut it to obtain a cross-section, use SEM to obtain a scanned image of the separator cross-section, use image analysis software such as ImageProPlus to find the functional coating and the first particle in the functional coating on the obtained scanned image, measure the maximum diameter of any 100 first particles, and the average value is the particle size Dv50 of the first particle. If the number of first particles in a region is less than 100, change the test region and repeat the above operation until 100 first particles are cumulatively tested.

[0076] In this invention, the thickness of the functional coating can be obtained by conventional testing methods in the art, such as by SEM, specifically as follows: discharge the battery to 0% SOC, disassemble and remove the separator, rinse it with NMP solvent, air dry it, cut the separator sample into a cross section and perform gold plating, take a high-magnification image of the obtained cross section with SEM, distinguish the functional coating by the interface, process the image with image processing software (ImageJ), take 10 different points to test the thickness of the functional coating and take the average value.

[0077] In this invention, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide.

[0078] In this invention, the lithium cobalt oxide includes Al element, and the mass content of Al element is 4000ppm-15000ppm based on the total mass of the lithium cobalt oxide, for example, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 10000ppm, 11000ppm, 12000ppm, 13000ppm, 14000ppm or 15000ppm.

[0079] Lithium cobalt oxide cathodes possess a two-dimensional layered structure, providing two-dimensional channels for lithium-ion insertion and extraction, thus improving the insertion and extraction rate. However, lithium cobalt oxide is prone to structural collapse and surface degradation during battery cycling, leading to rapid capacity decay and severely impacting its normal operation. 3+ ionic radius and Co 3+ When Al is present in lithium cobalt oxide, it encounters relatively less steric hindrance, allowing it to penetrate deep into the lithium cobalt oxide interior, stabilize its crystal structure, suppress irreversible phase transitions, and improve its structural stability. However, excessively high Al content in lithium cobalt oxide can negatively impact its rate performance and lead to a decrease in energy density; conversely, excessively low Al content has little effect on improving structural stability.

[0080] In this invention, the mass content of element Al in the lithium cobalt oxide can be determined by conventional testing methods in the art, for example by the following method: take lithium cobalt oxide material powder as a sample, take about 0.1g of the sample and add 10mL of hydrochloric acid to digest on a hot plate at 350℃ for 10min, cool and make up to 100ml, then dilute 10 times, and take a portion of the solution for analysis using an ICP spectrometer.

[0081] In this invention, the charging cutoff voltage of the battery is ≥4.5V.

[0082] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0083] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0084] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0085] The following examples illustrate the battery of the present invention.

[0086] Example 1: (1) Preparation of the positive electrode: Lithium cobalt oxide (containing 12745 ppm Al), LATP (average particle size 0.14 μm), polyvinylidene fluoride (PVDF 500), positive electrode conductive agent (Super P to carbon nanotube mass ratio 2:1) were mixed with N-methylpyrrolidone (NMP) solvent in a weight ratio of 93:3:2:2 and continuously stirred under the action of a stirrer to form a homogeneous and fluid positive electrode slurry. Subsequently, the positive electrode slurry was coated on the surface of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120 °C for 6 h. Then, it was rolled and slit to obtain the positive electrode sheet.

[0087] (2) Preparation of negative electrode: Artificial graphite, first silicon carbide, negative electrode conductive agent (carbon black to carbon nanotubes in a mass ratio of 1:1), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed with deionized water in a weight ratio of 90:8:1:0.5:0.5 and continuously stirred under the action of a stirrer to form a homogeneous and fluid negative electrode slurry. The slurry was then coated onto the surface of a 10 μm thick copper foil and dried in a vacuum oven at 120 °C for 6 hours. After rolling and slitting, the negative electrode sheet was obtained. The first silicon carbide had a sphericity of 0.932 and an average particle size of 9.4 μm.

[0088] (3) Preparation of electrolyte: In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), PP, EP, DEC, and PC were mixed into a homogeneous solvent. Then, LiPF6, 1,4-dicyano-2-butene, and 1,3-propanesulfonate lactone were slowly added and stirred until homogeneous to obtain the electrolyte. Based on the total mass of the electrolyte, w1 was 39.3% (26.5% EP + 12.8% PP), w2 was 12.5%, w3 was 1.2%, w4 was 18%, w8 was 3%, w9 was 12.3%, and the LiPF6 content was 13.7%.

[0089] At this point, w2 / w1 is 0.318, and w4 > w2.

[0090] (4) Preparation of the diaphragm: Melamine cyanurate (D = 0.5 μm), polyacrylate adhesive, and polyethylene glycol dispersant were added to deionized water in a mass ratio of 93:5:2 and stirred until homogeneous to obtain a functional coating slurry. This slurry was then applied to the first side surface of the base film using a gravure roller and dried in a multi-section oven at 60°C to form a functional coating (3.2 μm thick). Next, 800 parts by weight of polyvinylidene fluoride, 10 parts by weight of polyacrylic acid, 1 part by weight of ethylene oxide, and 3000 parts by weight of deionized water were mixed until homogeneous to obtain an adhesive layer slurry. This slurry was then applied to the second side surface of the base film and the functional coating, which was applied away from the base film, using a dot-coating technique. After drying, a separator was obtained. At this point, w3 / D was 0.024.

[0091] (5) Battery fabrication: The above-prepared positive electrode sheet, separator and negative electrode sheet are stacked and wound to obtain a bare cell; then the bare cell is placed in an aluminum-plastic film, and the above-prepared electrolyte is injected into the dried bare cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, the battery is obtained.

[0092] Example 2: (1) Preparation of the positive electrode: Lithium cobalt oxide (containing 4032 ppm Al), LLTO (average particle size 0.56 μm), PVDF500, and a positive electrode conductive agent (Super P to carbon nanotubes in a mass ratio of 2:1) were mixed with NMP solvent at a weight ratio of 93:3:2:2 and continuously stirred under the action of a stirrer to form a homogeneous and fluid positive electrode slurry. Subsequently, the positive electrode slurry was coated onto the surface of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120 °C for 6 hours. Then, it was rolled and slit to obtain the positive electrode sheet.

[0093] (2) Preparation of negative electrode: Artificial graphite, first silicon carbide, negative electrode conductive agent (carbon black to carbon nanotubes in a mass ratio of 1:1), CMC and SBR were mixed with deionized water in a weight ratio of 90:8:1:0.5:0.5 and continuously stirred under the action of a stirrer to form a homogeneous and fluid negative electrode slurry. The slurry was then coated onto the surface of a 10 μm thick copper foil and dried in a vacuum oven at 120 °C for 6 hours. After rolling and slitting, the negative electrode sheet was obtained. The first silicon carbide had a sphericity of 0.853 and an average particle size of 1.2 μm.

[0094] (3) Preparation of electrolyte: In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), PP, EP, DEC and PC were mixed into a homogeneous solvent. Then, LiPF6, 1,4-dicyano-2-butene and mannitol carbonate sulfate were slowly added and stirred until homogeneous to obtain the electrolyte. Based on the total mass of the electrolyte, w1 was 30.6% (20.4% EP + 10.2% PP), w2 was 19.8%, w3 was 0.05%, w4 was 18%, w8 was 4%, w9 was 15%, and the LiPF6 content was 12.55%.

[0095] At this point, w2 / w1 is 0.647, and w4 < w2.

[0096] (4) Preparation of the diaphragm: Melamine cyanurate (D = 0.07 μm), polyacrylate adhesive, and polyethylene glycol dispersant were added to deionized water in a mass ratio of 93:5:2 and stirred until homogeneous to obtain a functional coating slurry. This slurry was then applied to the first side surface of the base film using a gravure roller and dried in a multi-section oven at 60°C to form a functional coating (0.5 μm thick). Next, 800 parts by weight of polyvinylidene fluoride, 10 parts by weight of polyacrylic acid, 1 part by weight of ethylene oxide, and 3000 parts by weight of deionized water were mixed until homogeneous to obtain an adhesive layer slurry. This slurry was then applied to the second side surface of the base film and the functional coating, which was applied away from the base film, using a dot-coating technique. After drying, a separator was obtained. At this point, w3 / D was 0.00714.

[0097] (5) Battery fabrication: The above-prepared positive electrode sheet, separator and negative electrode sheet are stacked and wound to obtain a bare cell; then the bare cell is placed in an aluminum-plastic film, and the above-prepared electrolyte is injected into the dried bare cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, the battery is obtained.

[0098] Example 3: (1) Preparation of the positive electrode: Lithium cobalt oxide (containing 14984 ppm Al), LATP (average particle size 0.97 μm), PVDF500, and a positive electrode conductive agent (Super P to carbon nanotubes in a mass ratio of 2:1) were mixed with NMP solvent at a weight ratio of 93:3:2:2 and continuously stirred under the action of a stirrer to form a homogeneous and fluid positive electrode slurry. Subsequently, the positive electrode slurry was coated onto the surface of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120 °C for 6 hours. Then, it was rolled and slit to obtain the positive electrode sheet.

[0099] (2) Preparation of negative electrode: Artificial graphite, first silicon carbide, negative electrode conductive agent (carbon black to carbon nanotubes in a mass ratio of 1:1), CMC and SBR were mixed with deionized water in a weight ratio of 90:8:1:0.5:0.5 and continuously stirred under the action of a stirrer to form a homogeneous and fluid negative electrode slurry. The slurry was then coated onto the surface of a 10 μm thick copper foil and dried in a vacuum oven at 120 °C for 6 hours. After rolling and slitting, the negative electrode sheet was obtained. The first silicon carbide had a sphericity of 0.979 and an average particle size of 14.7 μm.

[0100] (3) Preparation of electrolyte: In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), PP, EP, DEC, and PC were mixed into a homogeneous solvent. Then, LiPF6, LiTFSI, 1,4-dicyano-2-butene, and vinyl sulfate were slowly added and stirred until homogeneous to obtain the electrolyte. Based on the total mass of the electrolyte, w1 was 44.7% (30% EP + 14.7% PP), w2 was 8.1%, w3 was 1.8%, w4 was 18%, w8 was 0.5%, w9 was 9.7%, the content of LiPF6 was 15%, and the content of LiTFSI was 2.2%.

[0101] At this point, w2 / w1 is 0.181, and w4 > w2.

[0102] (4) Preparation of the diaphragm: Melamine trithiocyanate (D = 1.9 μm), polyacrylate adhesive, and polyethylene glycol dispersant were added to deionized water in a mass ratio of 93:5:2 and stirred until homogeneous to obtain a functional coating slurry. This slurry was then applied to the first side surface of the base film using a gravure roller and dried in a multi-section oven at 60°C to form a functional coating (4.8 μm thick). Next, 800 parts by weight of polyvinylidene fluoride, 10 parts by weight of polyacrylic acid, 1 part by weight of ethylene oxide, and 3000 parts by weight of deionized water were mixed until homogeneous to obtain an adhesive layer slurry. This slurry was then applied to the second side surface of the base film and the functional coating, which was applied away from the base film, using a dot-coating technique. After drying, a separator was obtained. At this point, w3 / D was 0.00947.

[0103] (5) Battery fabrication: The above-prepared positive electrode sheet, separator and negative electrode sheet are stacked and wound to obtain a bare cell; then the bare cell is placed in an aluminum-plastic film, and the above-prepared electrolyte is injected into the dried bare cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, the battery is obtained.

[0104] Example 4 group: This set of examples is used to verify the impact of changes in "w1 and / or non-fluorinated carboxylic esters", as detailed below: Example 4a is based on Example 2, except that w1 is 20.3% (15.2% EP + 5.1% PP), w4 is 28.3%, the content of LiPF6 is 12.55%, and w2 / w1 is 0.975; Example 4b is based on Example 1, except that w1 is 54.8% (34.8% EP + 20% PP), w4 is 5.3%, the content of LiPF6 is 10.9%, w2 / w1 is 0.228, and w4 < w2. Example 4c is based on Example 1, except that w1 is 39.3% (39.3% of EP + 0% of PP).

[0105] Example 5 group: This set of examples is used to verify the impact of changes to "w5", as detailed below: Example 5a is based on Example 1, except that w2 is 5.2%, w1 is 46.6% (31.4% EP + 15.2% PP), and w2 / w1 is 0.112; Example 5b is based on Example 1, except that w2 is 24.9%, w1 is 26.9% (18.1% EP + 8.8% PP), w2 / w1 is 0.926, and w4 < w2.

[0106] Example 6 group: This set of examples is used to verify the impact of changes in "w2 / w1", as detailed below: Example 6a is based on Example 1, except that w1 is 20.3% (15.2% EP + 5.1% PP), w2 is 24%, w4 is 25.5%, and w2 / w1 is 1.182; Example 6b is based on Example 1, except that w1 is 54.8% (34.8% of EP + 20% of PP), w2 is 5.5%, w4 is 9.5%, and w2 / w1 is 0.1.

[0107] Example 7 group: This set of examples is used to verify the effects of changes in "w3" and / or the type of "first nitrile additive", as detailed below: Example 7a is based on Example 1, except that the first nitrile additive is replaced with benzyl mononitrile, w3 is 0.02%, the content of LiPF6 is 14.88%, D is 0.07 μm, and w3 / D is 0.00286; Example 7b is based on Example 1, except that the first nitrile additive is replaced with terephthalonitrile, w3 is 3%, the content of LiPF6 is 11.9%, and w3 / D is 0.06.

[0108] Example 8 group: This set of examples is used to verify the impact of changes to "w4", as follows: Example 8a is based on Example 1, except that w4 is 5%, w1 is 52.3% (35.2% EP + 17.1% PP), w2 / w1 is 0.239, and w4 < w2; Example 8b is based on Example 1, except that w4 is 27.8%, w1 is 29.5% (19.9% ​​EP + 9.6% PP), and w2 / w1 is 0.424.

[0109] Example 9 group: This set of examples is used to verify the impact of "w5" and / or "the selection of the second nitrile additive", as detailed below: Example 9a, based on Example 1, except that the electrolyte also contains a second nitrile additive (1,3,6-hexanetrionitrile and phosphazene shown in Formula 2-2 in a mass ratio of 2.5:1), w5 is 2.5%, and the content of LiPF6 is 11.2%; Example 9b is based on Example 1, except that the electrolyte also contains 1,3,6-hexanetrionitrile, w5 is 0.5%, and the content of LiPF6 is 13.2%. Example 9c, based on Example 1, except that the electrolyte also contains a second nitrile additive (1,3,6-hexanetrionitrile and butadionitrile in a mass ratio of 2.5:1), w5 is 7.7%, w1 is 31.6% (21.3% EP + 10.3% PP), and w2 / w1 is 0.396.

[0110] Example 10 group: This set of examples is used to verify the impact of changes in "EC and its content w6", as detailed below: Example 10a is based on Example 9a, except that w6 is 1% and the content of LiPF6 is 10.2%. Example 10b is based on Example 9a, except that w4 is 0%, w6 is 18%, and the content of LiPF6 is 11.2%.

[0111] Example 11 group: This set of examples is used to verify the impact of changes to "w8", as detailed below: Example 11a is based on Example 9a, except that w7 is 0.03% and the content of LiPF6 is 11.17%. Example 11b is based on Example 9a, except that w1 is 35% (23.6% EP + 11.4% PP), w7 is 1.8%, and w2 / w1 is 0.357.

[0112] Example 12 group: This set of examples is used to verify the impact of changes to "w8", as detailed below: Example 12a, based on Example 3, except that w8 is 0.1%, the electrolyte also includes VC and 1,3,6-hexanetrionitrile, w5 is 2.5%, w7 is 0.8%, w9 is 9.7%, w2 / w1 is 0.181, and the content of LiPF6 is 14.3%; Example 12b is based on Example 3, except that w8 is 5%, the electrolyte also includes VC and 1,3,6-hexanetrionitrile, w1 is 40.3% (27.2% EP + 13.1% PP), w5 is 2.5%, w7 is 0.8%, w9 is 9.7%, w2 / w1 is 0.201, and the content of LiPF6 is 13.8%.

[0113] Example 13 group: This set of examples is used to verify the impact of the changes to "w9", as follows: Example 13a is based on Example 1, except that w9 is 5%, w1 is 44.1% (29.8% EP + 14.3% PP), and w2 / w1 is 0.283; Example 13b is based on Example 1, except that w9 is 24.7%, w1 is 24.4% (16.5% EP + 7.9% PP), and w2 / w1 is 0.512; Example 13c is based on Example 1, except that w9 is 30%, w1 is 22.1% (14.9% EP + 7.2% PP), w2 / w1 is 0.566, and the content of LiPF6 is 10.7%.

[0114] Example 14 group: This set of examples is used to verify the impact of changes in "w3 / D", as detailed below: Example 14a is based on Example 1, except that w3 is 2.1%, the content of LiPF6 is 12.8%, D is 0.07 μm, and w3 / D is 0.3; Example 14b is based on Example 1, except that w3 is 0.1%, the content of LiPF6 is 14.8%, D is 0.5 μm, and w3 / D is 0.002; Example 14c is based on Example 1, except that w3 is 0.07%, the content of LiPF6 is 14.83%, D is 0.04 μm, and w3 / D is 0.0175; Example 14d is based on Example 1, except that w3 is 1.8%, the content of LiPF6 is 13.1%, D is 2.2 μm, and w3 / D is 0.0082; Example 14e is based on Example 1, except that w3 is 0.2%, the content of LiPF6 is 14.7%, D is 1.5 μm, and w3 / D is 0.0013; Example 14f is based on Example 1, except that w3 is 2.5%, the content of LiPF6 is 12.4%, D is 0.07 μm, and w3 / D is 0.357.

[0115] Example 15 group: This set of examples is used to verify the impact of "silicon-carbon materials", as detailed below: Example 15a is based on Example 1, except that the silicon-carbon material is composed of first silicon-carbon and second silicon-carbon in a mass ratio of 1:1, wherein the sphericity of the second silicon-carbon is 0.264 and the average particle size is 5.2 μm; Example 15b is based on Example 1, except that the silicon-carbon material is composed of first silicon-carbon and second silicon-carbon in a mass ratio of 1:1, wherein the second silicon-carbon has a sphericity of 0.763 and an average particle size of 14.6 μm.

[0116] Comparative Example 1: This comparative group is used to verify the impact of changes in "w1 and / or non-fluorinated carboxylic esters", as detailed below: Comparative Example 1a is based on Example 1, except that the non-fluorinated carboxylic esters EP and PP are replaced with butyl acetate of equal mass fraction. Comparative Example 1b is based on Example 3, except that w1 is 58.9% (39.7% EP + 19.2% PP), w4 is 7%, w2 / w1 is 0.138, and w4 < w2.

[0117] Comparative Example 2: This set of scales is used to verify the impact of changes in "w2", as detailed below: Based on Example 1, the difference is that w1 is 51.8% (34.9% of EP + 16.9% of PP), w2 is 0%, and w3 is 1.2%.

[0118] Comparative Example 3: This set of proportions is used to verify the impact of changes in "w2 / w1", as follows: Comparative Example 3a is based on Example 1, except that w1 is 20.3% (15.2% EP + 5.1% PP), w2 is 25%, w4 is 24.5%, w2 / w1 is 1.232, and w4 < w2. Comparative Example 3b is based on Example 1, except that w1 is 54.8% (34.8% of EP + 20% of PP), w2 is 5.1%, w4 is 9.9%, and w2 / w1 is 0.093.

[0119] Comparative Example 4: This set of scales is used to verify the impact of changes in "w3", as detailed below: Comparative Example 4a is based on Example 1, except that w3 is 0% and the content of LiPF6 is 14.9%. Comparative Example 4b is based on Example 1, except that w3 is 3.5%, the content of LiPF6 is 11.4%, and w3 / D is 0.07.

[0120] Comparative Example 5: Based on Example 1, the difference is that the positive electrode does not contain LATP, and the positive electrode slurry is composed of lithium cobalt oxide, PVDF 500 and positive electrode conductive agent in a weight ratio of 96:2:2.

[0121] Comparative Example 6: Based on Example 1, except that the sphericity of the first silicon-carbon is 0.804.

[0122] Test example: (1) 45℃ high temperature cycling test: The batteries prepared in the examples and comparative examples were subjected to cycle tests. The specific test method is as follows: At 45°C, the batteries were discharged to 3.0V at 0.7C, then allowed to stand for 10 minutes, and then charged to 4.55V at 1.2C with a cutoff current of 0.025C, followed by a 10-minute stand. The batteries were then discharged at a rate of 1.2C to the cutoff voltage of 3.0V, and allowed to stand for 10 minutes. The discharge capacity at this point was recorded as the initial capacity. This charge-discharge process was repeated until the 500th cycle of constant voltage charging was completed, followed by a 10-minute stand. The batteries were then discharged to 3.0V at 1.2C, and allowed to stand for 10 minutes. The discharge capacity at this point was recorded as the post-cycle capacity. The cycle capacity retention rate is calculated as: Post-cycle capacity × 100% / Initial capacity. The 45°C high-temperature cycle capacity retention rate is recorded in Table 1.

[0123] (2) Ratio performance test: The batteries prepared in the embodiments and comparative examples of this invention were charged at a constant current of 0.2C to 4.55V, then charged at a constant voltage of 4.55V with a cutoff current of 0.025C. After standing for 10 minutes, they were discharged to 3.0V at current densities of 0.2C and 2.5C, respectively. The ratio of the 2.5C discharge capacity to the 0.2C discharge capacity is the rate discharge capability of the battery. The test results are recorded in Table 1.

[0124] (3) Lithium plating test: After undergoing the cycle test described in (1) of the batteries prepared in the embodiments and comparative examples of the present invention, the batteries were retrieved and disassembled to observe the lithium plating state on the surface of the negative electrode. The criteria for judging the lithium plating phenomenon of the negative electrode were: 1) no lithium plating; 2) lithium plating occurred, and the lithium plating area was less than 10%, which was recorded as slight lithium plating, which had a relatively small impact on the battery and could be used normally; 3) the lithium plating area on the surface of the negative electrode was 10%-50%, which was recorded as moderate lithium plating; 4) the lithium plating area on the surface of the negative electrode was greater than 50%, which was recorded as severe lithium plating. The test results are recorded in Table 1.

[0125] Table 1: As can be seen from Table 1, the battery prepared in this invention has improved charge-discharge performance at high voltage and cycle stability at high temperature compared to the comparative example.

[0126] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes solid electrolyte particles, which include lithium titanium aluminum phosphate and / or lithium lanthanum titanium oxide. The electrolyte comprises non-fluorinated carboxylic acid esters, which include propyl propionate and / or ethyl propionate. Based on the total mass of the electrolyte, the mass content of the non-fluorinated carboxylic acid esters is w1, where w1 is 20%-55%. The electrolyte also includes diethyl carbonate, and based on the total mass of the electrolyte, the mass content of the diethyl carbonate is w2, and the ratio of w2 to w1 is 0.1-1.

2. The electrolyte further includes a first nitrile additive, which comprises a nitrile compound containing a carbon-carbon unsaturated bond. Based on the total mass of the electrolyte, the mass content of the first nitrile additive is w3, where w3 is 0.01%-3%. The negative electrode sheet includes a negative electrode active material, which includes a silicon-carbon material, and the silicon-carbon material includes a first silicon-carbon material, the first silicon-carbon material having a sphericity of 0.85-0.

99.

2. The battery according to claim 1, wherein, The chemical formula of the lithium titanium aluminum phosphate is Li 1+x1 Al x1 Ti2- x1 (PO4)3, 0 < x1 < 0.5, the chemical formula of the lithium lanthanum titanium oxide is Li 3-x2 La 2 / 3-x2 Ti 1-y M y O3, 0 < x2 < 2 / 3, 0 ≤ y < 1, M includes at least one of Nb, W, Ga, Ge, Se, Ta, Zr and Hf; And / or, the average particle size of the solid electrolyte particles is 0.1 μm-1 μm; And / or, the first nitrile additive includes at least one of acrylonitrile, isophthalonitrile, terephthalonitrile, benzonitrile, 2-amino-1,1,3-tricyano-1-propene and 1,4-dicyano-2-butene.

3. The battery according to claim 1 or 2, wherein, The electrolyte includes propylene carbonate, and based on the total mass of the electrolyte, the mass content of propylene carbonate is w4, where w4 > w2; And / or, w2 is 5%-25%; And / or, w3 is 0.05%-2%; And / or, w4 is 5%-28%.

4. The battery according to claim 1, wherein, The electrolyte includes a second nitrile additive, which includes succinic anionyl nitrile, adiponitrile, 1,3,6-hexanetrionitrile, 1,5-dicyanopentane, tris(2-cyanoethyl) phosphate, ethylene glycol bis(propionitrile) ether, 1,2,3,4-tetra(2-cyanoethoxy)butane, 1,2,4-butanetrionitrile, 1,2,3,4,5-penta(2-cyanoethoxy)pentane, etc. and At least one of the following, wherein n1, n2 and n3 are each independently an integer from 0 to 4, and m1, m2 and m3 are each independently an integer from 1 to 4; And / or, based on the total mass of the electrolyte, the mass content of the second nitrile additive is w5, where w5 is 0.5%-8%; Preferably, include and / or .

5. The battery according to claim 1, wherein, The electrolyte includes ethylene carbonate, and based on the total mass of the electrolyte, the mass content of the ethylene carbonate is w6, where w6 ≤ 1%. And / or, the electrolyte comprises vinylene carbonate, and the mass content of the vinylene carbonate is w7 based on the total mass of the electrolyte, where w7 is 0.01%-2%.

6. The battery according to claim 1, wherein, The electrolyte includes a sulfur-containing additive, which includes at least one of 1,3-propanesulfonate lactone, vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate. Preferably, based on the total mass of the electrolyte, the mass content of the sulfur-containing additive is w8, where w8 is 0.1%-5%.

7. The battery according to claim 1, wherein, The electrolyte includes fluoroethylene carbonate, and the mass content of the fluoroethylene carbonate is w9 based on the total mass of the electrolyte, where w9 is 5%-25%.

8. The battery according to claim 1, wherein, The silicon-carbon material further includes a second silicon-carbon; And / or, the average particle size of the first silicon carbide is 1 μm-15 μm; And / or, the sphericity of the second silicon carbide is 0.25-0.75, and the average particle size of the second silicon carbide is 5μm-15μm; Preferably, the silicon-carbon material comprises a first silicon-carbon and a second silicon-carbon.

9. The battery according to claim 1, wherein, The battery includes a separator, the separator including a base film and a functional coating located on at least one side of the base film; And / or, the thickness of the functional coating is 0.3μm-5μm; And / or, the functional coating includes first particles, the first particles comprising at least one of alumina, boehmite, alumina, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, and barium titanate. Preferably, the first particle comprises at least one of melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, and melamine trithiocyanate; More preferably, the particle size Dv50 of the first particle is D, where D is 0.05μm-2μm; More preferably, w3 / D is 0.002-0.

3.

10. The battery according to claim 1, wherein, The positive electrode sheet includes a positive electrode active material, which includes lithium cobalt oxide; preferably, the lithium cobalt oxide includes Al element, and the mass content of Al element is 4000ppm-15000ppm based on the total mass of the lithium cobalt oxide. And / or, the charging cut-off voltage of the battery is ≥4.5V.

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