A battery

Abstract

The application relates to the technical field of batteries, in particular to a battery. The battery comprises a negative electrode sheet, a positive electrode sheet, an electrolyte and a diaphragm. The diaphragm comprises a base material layer and a coating layer. The coating layer comprises a solid electrolyte material. The composition of the solid electrolyte material comprises a solid electrolyte. The Dv10 of the solid electrolyte material is 0.03-0.5 mu m. The thickness of the coating layer is 0.3-5 mu m. The puncture strength of the diaphragm is 200-700 gf. The negative electrode sheet comprises a spherical silicon-carbon material. The sphericity of the spherical silicon-carbon material is 0.8-1. The battery satisfies the following relationship: 0.75<=(D 9 -D 1 ) / D 5 <=1.5, 0.2<=S 1 / d 1 <=5. The battery of the application can improve the transmission performance of lithium ions, thereby reducing the self-discharge caused by the solid electrolyte, and making the battery have higher low-temperature discharge performance and higher high-temperature storage performance.

Description

Technical Field

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

[0002] Lithium-ion batteries have been widely used in smartphones, tablets, smart wearables, power tools, and electric vehicles due to their high energy density, long cycle life, lack of memory effect, and environmental friendliness.

[0003] To meet consumer demand, battery energy density is constantly being improved. Increasing the amount of silicon doped in the negative electrode can effectively improve battery energy density. However, due to the volume effect, interface impedance and kinetic hysteresis of silicon particles, low-temperature performance is greatly degraded, which has become a challenge for current silicon-containing batteries. Summary of the Invention

[0004] Research has shown that while silicon doping of the negative electrode can improve battery energy density, batteries with silicon-doped negative electrodes exhibit poor low-temperature performance. Solid-state electrolytes, as fast ion conductors, possess lithium-ion conduction characteristics unaffected by temperature, and coating the separator surface with solid-state electrolytes can improve the battery's low-temperature performance. However, compared to traditional inorganic coatings such as alumina and boehmite, the transition metal ions in solid-state electrolytes are prone to detaching from the crystal lattice in high-voltage environments, shuttling between the positive and negative electrodes, which easily induces chemical self-discharge effects. Especially during high-temperature storage, transition metal ions accelerate electrolyte reactions to form LiF deposits, further accelerating self-discharge. This causes the battery voltage to decay rapidly when stored at high temperatures. Moreover, the expansion of silicon-based materials further exacerbates side reactions in the electrolyte, further intensifying the chemical self-discharge effect, especially when the battery is stored at high temperatures, leading to a further deterioration in voltage decay.

[0005] To address the problem of rapid voltage decay in silicon anode batteries due to self-discharge caused by the solid electrolyte in the separator, which leads to rapid voltage drop under high-temperature storage conditions, this invention provides a battery. The battery of this invention improves lithium-ion transport performance, thereby reducing self-discharge caused by the solid electrolyte, enabling the battery to possess both high low-temperature discharge performance and high-temperature storage performance.

[0006] To achieve the above objectives, the present invention provides a battery comprising a negative electrode, a positive electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode. The separator comprises a carrier layer, the carrier layer comprising a substrate layer and a coating layer located on at least one surface of the substrate layer. The coating layer comprises a solid electrolyte material, the solid electrolyte material comprising a solid electrolyte, and the solid electrolyte material having a Dv10 of 0.03 μm-0.5 μm. The coating layer has a thickness of 0.3 μm-5 μm, and the separator has a puncture strength of 200 gf-700 gf. The negative electrode includes a negative current collector and a negative active layer located on at least one side surface of the negative current collector. The negative active layer includes a silicon-based material, which is a spherical silicon-carbon material with a sphericity of 0.8-1. The battery satisfies the following relationship: 0.75 ≤ (D 9 -D 1 ) / D 5 ≤1.5, where D 1 Dv10 of the spherical silicon-carbon material is expressed in μm. 5 Dv50 of the spherical silicon-carbon material is expressed in μm. 9 Dv90 of the spherical silicon-carbon material, in μm; The electrolyte comprises fluoroethylene carbonate, and the battery satisfies the following relationship: 0.2 ≤ S 1 / d 1 ≤5, where S 1 d represents the weight percentage of the fluoroethylene carbonate in the electrolyte. 1 Dv10 of the solid electrolyte material is expressed in μm.

[0007] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: In the battery of the present invention, the coating of the separator includes a solid electrolyte material. The solid electrolyte material can ensure the rapid transport of lithium ions between the positive and negative electrodes at low temperatures, thereby improving the kinetic performance of the battery and enhancing its low-temperature discharge performance. At the same time, it controls the Dv10 of the solid electrolyte material, the thickness of the coating, and the puncture strength of the separator. This can reduce the risk of transition metal ions detaching from the lattice of the solid electrolyte material while ensuring the low-temperature discharge performance of the battery. It can also improve or even prevent the coating in the separator from being too loose, which would make the coating easy to fall off and expose the substrate, making the separator easy to be punctured by silicon-based materials, thereby further reducing the voltage drop of the battery during high-temperature storage. Meanwhile, by controlling the sphericity and particle size relationship of the silicon-based material in the negative electrode sheet, on the one hand, the silicon-based material has fewer sharp edges and better dispersion, avoiding an overly loose negative electrode active layer and reducing the risk of silicon particles falling and puncturing the separator during battery cycling; on the other hand, it can also improve the dispersion uniformity of the silicon-based material, increase the smoothness of the negative electrode active layer surface, reduce the number of agglomerated particles protruding from the negative electrode active layer surface, and reduce the risk of silicon-based material protruding from the negative electrode active layer surface puncturing the separator during expansion, thereby further reducing self-discharge and further reducing the voltage drop of the battery during high-temperature storage. Furthermore, by controlling the battery to satisfy the relationship 0.2≤S 1 / d 1≤5, improves the matching degree between fluoroethylene carbonate and solid electrolyte material, reduces the dissolution of transition metal ions in solid electrolyte material, and enables fluoroethylene carbonate in electrolyte to complex most of the transition metal ions that have separated from solid electrolyte material, reducing or even avoiding the risk of transition metal ions migrating to the surface of negative electrode and damaging SEI film, thus worsening self-discharge, thereby improving both high-temperature storage voltage drop and rate performance.

[0008] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0009] 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. Attached Figure Description

[0010] Figure 1 The image shown is a SEM image of the coating of the diaphragm in Embodiment 1 of the present invention. Detailed Implementation

[0011] 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 invention. Unless otherwise specified herein, data ranges include endpoints.

[0012] 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.

[0013] This invention provides a battery comprising a negative electrode, a positive electrode, an electrolyte, and a separator located between the positive and negative electrodes. The separator includes a carrier layer, which comprises a substrate layer and a coating layer located on at least one surface of the substrate layer. The coating layer includes a solid electrolyte material (such as...). Figure 1The solid electrolyte material has a Dv10 of 0.03 μm to 0.5 μm (e.g., 0.03 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or within any two of the above values); the coating thickness is 0.3 μm to 5 μm (e.g., 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm). The diaphragm has a puncture strength of 200gf-700gf (e.g., 200gf, 250gf, 300gf, 350gf, 400gf, 450gf, 500gf, 550gf, 600gf, 650gf, 700gf, or within any two of the above values). The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector. The negative electrode active layer includes a silicon-based material, which is a spherical silicon-carbon material with a sphericity of 0.8-1 (e.g., 0.8, 0.83, 0.85, 0.88, 0.9, 0.93, 0.95, 0.98, 1, or within any two of the above values). The battery satisfies the following relationship: 0.75 ≤ (D 9 -D 1 ) / D 5 ≤1.5 (e.g., 0.75, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or within any two of the above values), where D 1 Dv10 of the spherical silicon-carbon material is expressed in μm. 5 Dv50 of the spherical silicon-carbon material is expressed in μm. 9 Dv90 of the spherical silicon-carbon material, in μm; The electrolyte comprises fluoroethylene carbonate, and the battery satisfies the following relationship: 0.2 ≤ S 1 / d 1 ≤5 (e.g., 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or within any two of the above values), where S 1 d represents the weight percentage of the fluoroethylene carbonate in the electrolyte. 1 Dv10 of the solid electrolyte material is expressed in μm.

[0014] In this invention, the Dv10 of the solid electrolyte material is the particle size corresponding to the cumulative particle size distribution reaching 10% in the volumetric particle size distribution of the solid electrolyte material. In this invention, the volumetric particle size distribution of the solid electrolyte material can be obtained by measuring and statistically processing the Dv10 of the solid electrolyte material in an SEM image taken at 5000x magnification on the coating surface, combined with image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv10 of the solid electrolyte material can also be obtained by testing with a laser particle size analyzer; for example, before preparing the separator, the Dv10 of the solid electrolyte material particles can be obtained by measuring the Dv10 of the solid electrolyte material using a laser particle size analyzer.

[0015] In this invention, the puncture strength of the separator can be measured by the following method: disassemble the battery and remove the separator, or use the prepared separator as a test sample. Cut a sample of 50mm×50mm in any size from the test sample. Lay the sample flat in the fixture of the universal tensile testing machine and clamp it. Select the puncture strength test item and puncture at a rate of (100±10)mm / min. Read the puncture strength test result from the test report. Repeat 3 times and take the average value as the puncture strength of the separator.

[0016] In this invention, the sphericity of the spherical silicon-carbon material can be tested using the following method: An image of the particles on the surface of the negative electrode active layer is captured using a scanning electron microscope (SEM). Within an arbitrarily selected 100μm × 100μm area in the image, spherical silicon-carbon materials are identified using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.), and the radius r of the equivalent circle representing the projected circumference of a single spherical silicon-carbon material is calculated. 1 The radius r of the equivalent circle of the projected area of ​​the spherical silicon-carbon material 2 The sphericity of a single spherical silicon-carbon material = r 2 / r 1 The sphericity of 100 spherical silicon-carbon materials was statistically analyzed and averaged. This process was repeated 5 times, and the average value was taken as the final test result. The scanning images were obtained by observing the surface of the negative electrode active layer using a scanning electron microscope (S-3400N, manufactured by Hitachi, Ltd.).

[0017] In this invention, the Dv10 of the spherical silicon-carbon material is the particle size corresponding to 10% of the cumulative particle size distribution in the volumetric particle size distribution of the spherical silicon-carbon material; the Dv50 of the spherical silicon-carbon material is the particle size corresponding to 50% of the cumulative particle size distribution in the volumetric particle size distribution of the spherical silicon-carbon material; and the Dv90 of the spherical silicon-carbon material is the particle size corresponding to 90% of the cumulative particle size distribution in the volumetric particle size distribution of the spherical silicon-carbon material. In this invention, the volumetric particle size distribution of the spherical silicon-carbon material can be obtained by measuring and statistically processing SEM images taken on the surface of the negative electrode active layer using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv10, Dv50, and Dv90 of the spherical silicon-carbon material can also be obtained by testing with a laser particle size analyzer.

[0018] Research has found that although silicon doping of the negative electrode can improve the energy density of the battery, the low-temperature performance of the battery with silicon doped negative electrode is poor. The specific reasons are as follows: 1- Silicon-based materials are prone to expansion, which damages the conductive network and affects the overall conductivity of the negative electrode sheet; 2- The volume expansion of silicon-based particles makes the SEI film on the surface of silicon-based particles easy to break. Therefore, the surface of the expanded silicon-based particles will continue to react with the electrolyte to form an SEI film, which leads to an increase in battery impedance; 3- The lithium intercalation phase transition reaction of silicon-based materials is slow at low temperatures, and the capacity is prone to a sharp decline.

[0019] In the battery of this invention, the separator coating includes a solid electrolyte material. This solid electrolyte material possesses high ion-conducting performance, enabling the construction of a rapid lithium-ion transport channel between the positive and negative electrodes. Furthermore, the solid electrolyte material exhibits lithium-ion conduction performance unaffected by temperature, ensuring rapid lithium-ion transport between the positive and negative electrodes even at low temperatures, thereby improving the battery's kinetic performance and consequently enhancing its low-temperature discharge performance. However, high pressure or high temperature exacerbates the risk of transition metal ions detaching from the crystal lattice in the solid electrolyte, especially in smaller-particle-size solid electrolyte materials. Increased contact area with the electrolyte leads to increased lattice defect density. Both high temperature and high pressure environments lower the energy barrier for transition metal ions to detach from the solid electrolyte material surface and increase side reactions between byproducts in the electrolyte (e.g., HF) and the solid electrolyte, making it easier for transition metal ions to detach from the crystal lattice. Moreover, excessive coating thickness leads to increased electrolyte retention in the solid electrolyte layer, increasing side reactions under high temperature and high pressure conditions, further exacerbating the detachment of transition metal lithium ions from the solid electrolyte lattice and increasing the total amount of precipitated transition metals. Moreover, while a thicker coating can improve the battery's low-temperature discharge performance, it also leads to the release of more transition metal ions from the solid electrolyte material. Once these transition ions dissolve from the solid electrolyte material, the structure of the solid electrolyte material collapses, increasing the risk of a deterioration in the battery's self-discharge. Controlling the puncture strength of the separator can reduce the risk of battery self-discharge.

[0020] Based on this, the battery of the present invention, by controlling the Dv10 of the solid electrolyte material, the thickness of the coating, and the puncture strength of the separator, can reduce the risk of transition metal ions detaching from the crystal lattice of the solid electrolyte material while ensuring the low-temperature discharge performance of the battery. It can also improve or even prevent the coating in the separator from being too loose, making it easy for the coating to fall off and for the separator to be easily punctured by silicon-based materials. Furthermore, controlling the puncture strength of the separator within the aforementioned range can reduce or even overcome the risk of the separator being punctured by silicon-based materials, thereby further reducing the voltage drop of the battery during high-temperature storage.

[0021] Because silicon-based materials are relatively hard, they are prone to squeezing or puncturing the separator in the battery, exacerbating self-discharge. Furthermore, silicon-based materials increase side reactions, intensifying the dissolution of transition metals in the solid electrolyte material, leading to further self-discharge. Therefore, the battery of this invention limits the silicon-based material in the negative electrode to spherical silicon-carbon material, and simultaneously controls the sphericity and particle size relationship of the spherical silicon-carbon material. Controlling the sphericity of the spherical silicon-carbon material within the aforementioned range prevents the sharp edges of the spherical silicon-carbon material from puncturing the separator, and controlling the particle size of the spherical silicon-carbon material to meet the aforementioned requirements... This system enables spherical silicon-carbon materials to have better dispersibility, preventing the negative electrode active layer from being too loose. It reduces the risk of particles of spherical silicon-carbon materials falling off or breaking during battery cycling, producing sharp edges that puncture the separator. It also improves the dispersion uniformity of spherical silicon-carbon materials, increases the smoothness of the negative electrode active layer surface, reduces the number of agglomerated particles protruding from the surface of the negative electrode active layer, and reduces the risk of spherical silicon-carbon materials protruding from the surface of the negative electrode active layer puncturing the separator when expanding. This further reduces self-discharge and further reduces the voltage drop of the battery during high-temperature storage.

[0022] Furthermore, the fluoroethylene carbonate in the electrolyte not only reduces the occurrence of side reactions and lowers the risk of transition metal ions detaching from the crystal lattice of the solid electrolyte material, but also complexes the transition metal ions dissolved from the solid electrolyte material (e.g., Ti). 4+ Zr 4+ This prevents the substance from migrating to the surface of the negative electrode and damaging the SEI film, thus worsening self-discharge. Simultaneously, the battery also satisfies the following relationship: 0.2 ≤ S 1 / d 1 ≤5, controlling the battery to satisfy the above relationship, improves the matching degree between fluoroethylene carbonate and solid electrolyte material, reduces the dissolution of transition metal ions in solid electrolyte material, and enables fluoroethylene carbonate in electrolyte to complex most of the transition metal ions that have separated from solid electrolyte material, reducing or even avoiding the risk of transition metal ions migrating to the surface of negative electrode and damaging SEI film, thus worsening self-discharge, thereby improving both high-temperature storage voltage drop and rate performance.

[0023] When the Dv10 of the solid electrolyte material is less than 0.03 μm and / or the coating thickness is greater than 5 μm, the risk of transition metal ions detaching from the solid electrolyte material under high pressure and / or high temperature increases dramatically. Even if the puncture strength of the separator and the sphericity and particle size relationship of the spherical silicon-carbon material are controlled, the chemical self-discharge effect caused by the shuttle between the positive and negative electrodes cannot be effectively improved. When the Dv10 of the solid electrolyte material is greater than 0.5 μm and / or the coating thickness is less than 0.5 μm, the Dv10 of the solid electrolyte material is too high, resulting in an overly loose coating that is easy to fall off from the substrate layer. This makes it easy for silicon-based particles to puncture the separator, and also prevents the ion-conducting properties of the solid electrolyte material from being fully utilized or to play a smaller role, resulting in the inability to improve the low-temperature performance of the separator.

[0024] When S 1 / d 1 When the concentration is <0.2, the weight percentage of FEC in the electrolyte is too low, which cannot effectively prevent transition metal ions from migrating to the surface of the negative electrode, damaging the SEI, resulting in a significant deterioration of chemical self-discharge and affecting the high-temperature storage performance of the battery; S 1 / d 1 When the temperature exceeds 5°C, the solid electrolyte material particles are too small, resulting in excessive dissolution of transition metal ions and an excessively high FEC weight ratio. This can lead to uneven or excessively thick SEI film formation on the spherical silicon-carbon surface, which is detrimental to the rate performance and low-temperature performance of the battery.

[0025] In this invention, by controlling the particle size of silicon-based particles, the Dv10 of the solid electrolyte material, the coating thickness, the puncture strength of the separator, and the relationship between the Dv10 of fluoroethylene carbonate in the electrolyte and the solid electrolyte material, compared with the prior art, it is possible to improve the self-discharge tendency of the solid electrolyte in the separator, enabling the battery to have both high low-temperature performance, high rate performance, and low high-temperature storage voltage drop. To further improve the effect, one or more of the technical features can be further optimized.

[0026] In some instances, the XRD pattern of the solid electrolyte material includes a first characteristic peak and a second characteristic peak, with the first characteristic peak located at 20.5°-21.5° and the second characteristic peak located at 23.5°-24.5°. The battery satisfies the following relationship: 0.3 ≤ I 1 / I 2 ≤0.7 (e.g., 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, 0.5, 0.7, or within any two of the above values), where I 1 I represents the intensity of the first characteristic peak. 2The intensity of the second characteristic peak is given. The first characteristic peak is the diffraction peak corresponding to the 104 crystal plane. The first characteristic peak represents the lithium ion transport channels in the solid electrolyte material. The greater the intensity of the first characteristic peak, the more lithium ion transport channels there are in the solid electrolyte material. The second characteristic peak is the diffraction peak corresponding to the 113 crystal plane. The second characteristic peak represents the crystallization of the NASICON structure of the solid electrolyte material. The greater the intensity of the second characteristic peak, the better the integrity of the crystal phase of the single crystal particles of the solid electrolyte material and the higher the purity. However, in the solid electrolyte material, the first and second characteristic peaks are inversely related and cannot be improved simultaneously. Therefore, controlling the battery to satisfy the above relationship can ensure that the solid electrolyte material has a sufficient number of lithium ion transport channels while maintaining the integrity of the crystal phase of the single crystal particles of the solid electrolyte, further improving the lithium ion transport capability of the solid electrolyte material, and making its lithium ion transport capability unaffected by temperature, thereby improving the low-temperature discharge performance of the separator including the solid electrolyte material in the battery.

[0027] In some instances, the solid electrolyte material includes one or more of the following: lithium lanthanum zirconium oxide solid electrolyte, lithium lanthanum zirconium tantalum oxide solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum titanium oxide solid electrolyte.

[0028] In some instances, the Dv50 of the solid electrolyte material is 0.05 μm to 5 μm (e.g., 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or within any two of the above values). The Dv50 of the solid electrolyte material is the particle size corresponding to 50% of the cumulative particle size distribution in the volumetric particle size distribution of the solid electrolyte material.

[0029] In some instances, the Dv50 of the solid electrolyte material is 0.1 μm-4 μm.

[0030] In some instances, the Dv90 of the solid electrolyte material is 0.1 μm-9 μm (e.g., 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or within any two of the above values). The Dv90 of the solid electrolyte material is the particle size corresponding to 90% of the cumulative particle size distribution in the volumetric particle size distribution of the solid electrolyte material.

[0031] In some instances, the Dv90 of the solid electrolyte material is 0.3 μm-6 μm.

[0032] In some instances, the solid electrolyte material accounts for 30%-99% of the total weight of the coating (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or any combination of the above values).

[0033] In some instances, the coating comprises a transition metal, which includes one or more of lanthanum, zirconium, and titanium. The transition metal is derived from a solid electrolyte material.

[0034] In some instances, the coating is applied to the side facing the positive electrode.

[0035] In some instances, the coating is located on one side of the substrate layer, facing the positive electrode, and the weight percentage of the transition metal in the coating is 2%-15% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or within any two of these values). Controlling the weight percentage of the transition metal in the coating avoids the situation where an excessively high weight percentage of transition metal ions in the coating would prevent further improvement in low-temperature performance.

[0036] In some instances, the coating also includes a second particle.

[0037] In some instances, the weight percentage of the second particle is 0%-60% based on the total weight of the coating (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any two of the above values). It is understood that when the weight percentage of the second particle is 0% based on the total weight of the coating, it indicates that the second particle is absent.

[0038] In some instances, the second particle comprises one or more of the following: alumina, boehmite, magnesium hydroxide, silicon dioxide, magnesium oxide, boron nitride, melamine, melamine cyanurate, melamine polyphosphate, aluminum diethylphosphite, 4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, guanine, 2-mercaptobenzimidazole, and 2-mercaptobenzimidazole derivatives.

[0039] In some instances, the coating also includes a first adhesive.

[0040] In some instances, the first adhesive accounts for 1%-10% of the total weight of the coating (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of the above values).

[0041] In some instances, the first adhesive comprises one or more of the following: fluoropolymers, polyimide, polyacrylonitrile, aramid resin, styrene-butadiene rubber, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose, sodium carboxymethyl cellulose, carboxyethyl cellulose, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, acrylic polymers, acrylate polymers, lithium polystyrene sulfonate, silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, and pure styrene latex.

[0042] In this invention, the fluoropolymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0043] In this invention, the acrylate polymers include one or more of polymethyl methacrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymers, acrylate monomer-ethylene copolymers, acrylate monomer-acrylonitrile-ethylene copolymers, styrene-acrylate monomer-acrylonitrile copolymers, ethylhexyl acrylate-methyl methacrylate copolymers, butyl acrylate-methyl methacrylate copolymers, methyl acrylate-N,N-dimethylacrylamide copolymers, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymers, ethyl acrylate-N,N-diethylacrylamide copolymers, and ethyl acrylate-2-(diethylamino)ethyl acrylate. The acrylate monomers include one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, hydroxyethyl methacrylate, butyl acrylate, and ethyl methacrylate.

[0044] In some instances, the areal density of the coating is 0.5 g / m³. 2 -5g / m 2 (For example, 0.5g / m 2 1g / m 2 1.5g / m 2 2g / m 2 2.5g / m 2 3g / m 2 3.5g / m 2 4g / m 2 4.5g / m 2 5g / m2 Or within the range formed by any two of the above values).

[0045] In some instances, the areal density of the coating is 0.8 g / m³. 2 -4g / m 2 .

[0046] In this invention, the areal density of the coating refers to the areal density of a single-sided coating. When the coating is located on one side of the substrate layer, the areal density of the coating is the areal density of the coating on that side (i.e., the side with the coating); when the coating is located on both sides of the substrate layer, the areal density of the coating is the areal density of the coating on either side, and the areal densities of the coatings on both sides may be the same or different.

[0047] In some instances, the diaphragm further includes an adhesive layer located on at least one surface of the carrier layer.

[0048] In some instances, the adhesive layer comprises a first polymer and optionally (“optionally” means that it may or may not be present) filler particles.

[0049] In some instances where the adhesive layer comprises a first polymer and optionally filler particles, the first polymer accounts for 20%-100% of the total weight of the adhesive layer (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or any two of the above values), and the filler particles account for 0%-80% of the total weight (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any two of the above values).

[0050] In some instances, the first polymer includes one or more of the following: fluoropolymers, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, styrene-butadiene rubber, polyvinyl alcohol, polyimide, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, lithium polystyrene sulfonate, pure styrene latex, polyvinylpyrrolidone, polyethylene oxide, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose.

[0051] In some instances, the filler particles are composed of one or more of the following: alumina, boehmite, magnesium oxide, magnesium hydroxide, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, melamine, melamine cyanurate, melamine polyphosphate, aluminum diethylphosphite, 4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, guanine, 2-mercaptobenzimidazole, and 2-mercaptobenzimidazole derivatives.

[0052] In other embodiments, the adhesive layer comprises polymer particles.

[0053] In some instances where the adhesive layer comprises polymer particles, the battery satisfies the following relationship: 10 ≤ D 5 / k 1 ≤23 (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or any two of the above values), where k 1 The average particle size of the polymer particles is expressed in μm. Controlling the battery to satisfy the above relationship can improve the bonding strength between the separator and the negative electrode, prevent short circuits caused by misalignment of the separator and electrode during high-temperature cycling expansion, and thus improve the high-temperature safety of the battery.

[0054] In some instances, the average particle size k of the polymer particles 1 The value is 0.4μm-0.95μm (e.g., 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 0.95μm, or within any two of the above values).

[0055] In some instances, the average particle size k of the polymer particles 1 The range is 0.65μm-0.85μm.

[0056] In some instances, the polymer particles comprise a second polymer, which includes one or more of the following: fluoropolymers, polyimide, polyacrylonitrile, polyimide, styrene-butadiene rubber, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, acrylate polymers, lithium polystyrene sulfonate, silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, and pure styrene latex.

[0057] In some instances, the puncture strength of the diaphragm is 250gf-600gf (e.g., 250gf, 300gf, 350gf, 400gf, 450gf, 500gf, 550gf, 600gf or within any two of the above values).

[0058] In this invention, the puncture strength of the separator can be measured by the following method: disassemble the battery and remove the separator, or use the separator without the battery as a test sample. Cut a test sample of 50mm×50mm in any size from the test sample. Lay the test sample flat in the fixture of the universal tensile testing machine and clamp it. Select the puncture strength test item and puncture at a rate of (100±10)mm / min. Read the puncture strength test result from the test report. Repeat 3 times and take the average value as the puncture strength of the separator.

[0059] In some instances, the negative electrode active layer includes a negative electrode active material, which includes a silicon-based material and optionally ("optionally" means that it may or may not be present) a graphite material, wherein the silicon-based material is a spherical silicon-carbon material.

[0060] In some instances, the particle size of the spherical silicon-carbon material satisfies the following relationship: 0.8 ≤ (D 9 -D 1 ) / D 5 ≤1.25 (e.g., 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, or within any two of the above values).

[0061] In some instances, the Dv50 of the spherical silicon carbide material is 5 μm-10 μm (e.g., 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.3 μm, 8.5 μm, 8.8 μm, 9 μm, 9.3 μm, 9.5 μm, 9.8 μm, 10 μm or within any two of the above values).

[0062] In some instances, the Dv90 of the spherical silicon carbide material is 9.5 μm-18 μm (e.g., 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or within any two of the above values).

[0063] In some instances, the Dv10 of the spherical silicon carbide material is 2.5 μm to 6 μm (e.g., 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm or within any two of the above values).

[0064] According to some specific embodiments, D 1 For 2.5-6, D 5 For 5-10, D 9The particle size of the spherical silicon-carbon material is 9.5-18, and the particle size satisfies the following relationship: 0.75 ≤ (D 9 -D 1 ) / D 5 ≤1.5.

[0065] According to some specific embodiments, D 1 For 2.5-6, D 5 For 8-10, D 9 The particle size of the spherical silicon-carbon material is 9.5-18, and the particle size satisfies the following relationship: 0.8 ≤ (D 9 -D 1 ) / D 5 ≤1.25.

[0066] In some instances, the spherical silicon-carbon material comprises porous carbon and silicon particles at least partially located in the pores of the porous carbon.

[0067] In some instances, the weight percentage of the silicon-based material is 1%-100% (e.g., 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or within any two of the above values) based on the total weight of the negative electrode active material.

[0068] In some instances, the graphite material accounts for 0%-99% of the total weight of the negative electrode active material (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or within any two of the above values).

[0069] In some instances, the graphite material includes one or more of synthetic graphite and natural graphite.

[0070] In some instances, the weight percentage of the negative electrode active material is 75%-95% (e.g., 75%, 78%, 80%, 83%, 85%, 88%, 90%, 93%, or 95%, or within any two of the above values) based on the total weight of the negative electrode active layer.

[0071] In some instances, the negative electrode active layer further includes a negative electrode conductive agent and a negative electrode binder.

[0072] In some instances, the negative electrode conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, graphene, and carbon fiber.

[0073] In some instances, the negative electrode binder includes one or more of styrene-butadiene rubber (SBR), fluoropolymers, lithium polyacrylate (PAALi), acrylonitrile polymers, polyacrylic acid (PAA), polyurethane, sodium polymethylcellulose (CMC-NA), and lithium polymethylcellulose (CMC-Li).

[0074] In some instances, based on the total weight of the negative electrode active layer, the weight percentage of the negative electrode conductive agent is 1%-8% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%, or within any two of the above values), and the weight percentage of the negative electrode binder is 2%-15% (e.g., 2%, 3%, 5%, 8%, 10%, 13%, or 15%, or within any two of the above values).

[0075] In some instances, the weight percentage S of the fluoroethylene carbonate in the electrolyte is... 1 It is between 4% and 30% (for example, 4%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, or within any two of the above values).

[0076] In some instances, the weight percentage S of the fluoroethylene carbonate in the electrolyte is... 1 It ranges from 5% to 25%.

[0077] In some instances, the electrolyte includes an organic solvent and an additive, wherein the organic solvent includes one or more of carbonates and carboxylic esters.

[0078] In some instances, the carbonate comprises ethylene carbonate and / or one or more of the following solvents: propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, whether fluorinated or unsubstituted.

[0079] In some instances, the carboxylic acid ester includes one or more of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl butyrate, and n-ethyl butyrate. In some instances, the additive comprises fluoroethylene carbonate and optionally one or more of the following substances: vinylene carbonate, vinyl ethylene carbonate, vinyl sulfate, succinic acid nitrile, glutaronitrile, adiponitrile, heptonitrile, octanoic acid nitrile, sebaconitrile, 1,3,6-hexanetrionitrile, glyceryl trionitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,3-propanesulfonic acid lactone, and propenyl-1,3-sulfonic acid lactone.

[0080] In some instances, the electrolyte also includes lithium salts.

[0081] In some examples, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPF2O2), lithium difluorobis(oxalate) phosphate (LiPF2(C2O4)2), lithium tetrafluorooxalate phosphate (LiPF4C2O4), lithium oxalate phosphate (LiPO2C2O4), lithium bis(oxalate) borate (LiBOB), lithium difluorooxalate borate (LiODFB), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0082] In some instances, based on the total weight of the electrolyte, the lithium salt accounts for 5%-20% by weight (e.g., 5%, 8%, 10%, 13%, 15%, 18%, or 20%, or any two of the above values), the organic solvent accounts for 40%-90% by weight (e.g., 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 85%, or 90%, or any two of the above values), and the additives account for 0.1%-40% by weight (e.g., 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40%, or any two of the above values).

[0083] In some instances, the positive electrode includes a positive current collector and a positive active layer located on at least one side surface of the positive current collector.

[0084] In some instances, the positive electrode active layer comprises a positive electrode active material having an average particle size of 3 μm-20 μm (e.g., 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm or within any two of the above values).

[0085] In this invention, the average particle size of the positive electrode active material can be obtained by the following method: In an SEM image of the surface of the positive electrode active layer, arbitrarily select a 10μm × 10μm area, and measure the particle size of 100 randomly selected positive electrode active materials using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The average particle size of the 100 positive electrode active materials is the average particle size of the positive electrode active material. It is understood that if no 100 positive electrode active materials are observed in the image, multiple images are taken, and the average of the total particle sizes of the 100 positive electrode active materials is taken as the average particle size of the positive electrode active material.

[0086] In some instances, the positive electrode active material includes lithium cobalt oxide and optionally ("optionally" means that it may or may not be present) one or more of the following substances: lithium nickel oxide, lithium iron phosphate, lithium manganese oxide, and lithium nickel cobalt manganese oxide.

[0087] In some instances, the positive electrode active layer in the positive electrode sheet further includes carbon nanotubes, the average diameter of which is 5nm-12nm (e.g., 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, or any two of these values). In this invention, the diameter of the carbon nanotubes is the average diameter, which can be obtained by testing as follows: using a transmission electron microscope (TEM), 20 carbon nanotubes are randomly selected within a field of view, the diameter of each carbon nanotube is measured, and the average value is taken. It is understood that when carbon nanotubes have an outer diameter and an inner diameter, the outer diameter is used.

[0088] In some instances, the carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0089] In some examples, the average particle size of the positive electrode active material is 3 μm-20 μm, the average diameter of the carbon nanotubes is 5 nm-12 nm, and the areal density of the coating is 0.5 g / m³. 2 -5g / m 2 Controlling the particle size of the positive electrode active material within the aforementioned range can balance its electron and ion conduction capabilities. Controlling the diameter of the carbon nanotubes can enhance the electron conduction capability between the positive electrode active materials. Controlling the areal density of the coating can improve the electron conduction capability between the positive electrode sheet and the separator. Therefore, through the synergistic effect of the particle size of the positive electrode active material, the diameter of the carbon nanotubes, and the areal density of the coating, the overall electron conduction capability of the battery can be further improved, and the low-temperature performance can be further enhanced.

[0090] In some instances, the positive electrode active layer includes a positive electrode conductive agent and a positive electrode binder.

[0091] In some instances, the positive electrode conductive agent includes one or more of carbon black, carbon nanotubes, conductive graphite, and graphene.

[0092] In some instances, the positive electrode binder includes one or more of polyvinylidene fluoride (PVDF), acrylic-modified PVDF, acrylonitrile-vinylidene fluoride copolymer, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, and polyimide.

[0093] In some instances, based on the total weight of the positive electrode active layer, the weight percentage of the positive electrode active material is 90wt%-98wt% (e.g., 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, or 98wt%, or within any two of the above values), the weight percentage of the positive electrode conductive agent is 0.5wt%-5wt% (e.g., 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%, or within any two of the above values), and the weight percentage of the positive electrode binder is 0.5wt%-5wt% (e.g., 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%, or within any two of the above values).

[0094] In some instances, the battery is a lithium-ion rechargeable battery.

[0095] In some instances, the charge / discharge cutoff voltage of the battery is greater than 4.5V (e.g., 4.51V, 4.53V, 4.55V, 4.58V, 4.6V, 4.63V, 4.65V, 4.68V, or 4.7V).

[0096] 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.

[0097] The following examples illustrate the battery of the present invention.

[0098] Example 1 (1) Diaphragm LATP, polyvinylidene fluoride-hexafluoropropylene, and polyethylene glycol were added to deionized water at a mass ratio of 94:5:1 and mixed evenly to obtain a coating slurry. The coating slurry was then applied to one side of a substrate layer (polyethylene) using a microgravure plate and dried in a multi-section oven at 60°C to obtain a coating with a thickness of 1.6 μm. The transition metal ion in the coating was titanium.

[0099] Polymer particles (methyl methacrylate-ethylene copolymer, with an average particle size of 0.75 μm) were mixed with water and stirred until uniformly dispersed to obtain a coating slurry with a solid content of 10%. The slurry, with a 100% solids mass ratio, was applied to the other side of the substrate layer and the surface of the coating layer using a gravure roller. After drying in a multi-section oven at 60°C, the coating layer was formed. The puncture strength of the diaphragm was 360 gf.

[0100] (2) Negative electrode plate Graphite, spherical silicon carbide (sphericity 0.96), conductive carbon black (SuperP), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber were mixed in an aqueous solvent at a weight ratio of 91:7:1:0.5:0.5 and continuously stirred under the action of a stirrer to form a homogeneous and fluid negative electrode slurry. Subsequently, the slurry was coated on the surface of a 10 μm thick current collector copper foil and dried in a vacuum oven at 120 °C for 6 hours. After that, it was rolled and slit to obtain the negative electrode sheet.

[0101] (3) Positive electrode plate Lithium cobalt oxide (average particle size 13.2 μm), binder (polyvinylidene fluoride (PVDF500)), and conductive carbon material (Super P: single-walled carbon nanotubes = 2:1, average diameter of single-walled carbon nanotubes 8 nm) were mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 97.5:1:1.5 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 both sides of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120 °C for 6 h. Then, after rolling and slitting, the positive electrode sheet was obtained.

[0102] (4) Electrolyte In an argon-filled glove box (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate, propylene carbonate, propyl propionate, and ethyl propionate solvents were mixed in a volume ratio of 15:15:50:20 to form a homogeneous solvent. This homogeneous solvent was then slowly added to the electrolyte at a mass ratio of 15.5 wt% LiPF6, 2 wt% 1,3-propanesulfonyl lactone, 3 wt% 1,3,6-hexanetrionitrile, and 15 wt% fluoroethylene carbonate. After stirring until homogeneous, the electrolyte was obtained.

[0103] (5) Lithium-ion batteries The positive electrode sheet obtained in step (3), the separator obtained in step (1), and the negative electrode sheet obtained in step (2) are wound together to form a bare battery cell. Then, the bare battery cell is placed in an aluminum-plastic film, and the electrolyte obtained in step (4) is injected into the dried bare battery cell. After vacuum sealing, room temperature standing, and high temperature formation, a lithium-ion battery is obtained. The side of the separator with coating corresponds to the positive electrode sheet, and the other side corresponds to the negative electrode sheet.

[0104] Example 2 The procedure was carried out in accordance with Example 1, except that the coating in the diaphragm was located on both sides of the substrate layer, and the adhesive layer was located on the surface of the coating on both sides.

[0105] Example 3 Group This set of examples is used to illustrate when S 1 / d 1 The impact of changes.

[0106] This embodiment group is carried out with reference to Embodiment 1, except that S is changed. 1 / d 1 For details, please refer to Table 1-1.

[0107] Table 1-1 Example 4 group This set of examples illustrates the effects of changes in coating thickness and diaphragm puncture strength.

[0108] Example 4a The procedure was carried out in accordance with Example 1, except that the coating thickness was 0.5 μm, and the puncture strength of the diaphragm was 510 gf by selecting substrate layers of different materials and preparation processes.

[0109] Example 4b The procedure was carried out in accordance with Example 1, except that the coating thickness was 5 μm, and the puncture strength of the diaphragm was 360 gf by selecting substrate layers of different materials and preparation processes.

[0110] Example 5 group This set of examples illustrates the effects that occur when the composition of the solid electrolyte material and / or coating changes.

[0111] This embodiment group is based on Embodiment 1, except that the composition of the solid electrolyte material and / or coating is changed, as detailed in Tables 1-2.

[0112] Table 1-2 Example 6 group This set of examples illustrates the effects of changes in the particle size and / or coating composition of solid electrolyte materials.

[0113] This embodiment group is based on Example 1, except that the particle size of the solid electrolyte material and / or the composition of the coating are changed, as detailed in Tables 1-3 and 1-4.

[0114] Table 1-3 Table 1-4 Example 7 group This set of examples illustrates the effects of changes in the puncture strength of the diaphragm.

[0115] Example 7a The procedure was carried out in accordance with Example 1, except that the puncture strength of the diaphragm was adjusted to 250 gf by changing the substrate layer.

[0116] Example 7b The procedure was carried out in accordance with Example 1, except that the puncture strength of the diaphragm was adjusted to 600 gf by changing the substrate layer.

[0117] Example 8 group This set of examples illustrates the effects of changes in the particle size distribution of spherical silicon carbide materials.

[0118] This embodiment group is based on Embodiment 1, except that the particle size distribution of the spherical silicon-carbon material is changed, as detailed in Tables 1-5.

[0119] Table 1-5 Example 9 group This set of examples is used to illustrate when D 5 / k 1 The impact of changes.

[0120] This embodiment group is carried out with reference to Embodiment 1, except that D is changed. 5 / k 1 For details, please refer to Table 1-6.

[0121] Table 1-6 Example 10 group Example 10a The procedure was carried out in accordance with Example 1, except that the areal density of the coating was 0.8 g / m³. 2 The average particle size of the positive electrode active layer is 3.2 μm, and the average diameter of the carbon nanotubes in the positive electrode active layer is 11.7 nm.

[0122] Example 10b The procedure was carried out in accordance with Example 1, except that the areal density of the coating was 4 g / m². 2 The average particle size of the positive electrode active layer is 19.6 μm, and the average diameter of the carbon nanotubes in the positive electrode active layer is 5.2 nm.

[0123] Example 10c The procedure was carried out in accordance with Example 1, except that the areal density of the coating was 5.5 g / m². 2 The average particle size of the positive electrode active layer is 2.7 μm, and the average diameter of the carbon nanotubes in the positive electrode active layer is 12.5 nm.

[0124] Example 11 group This set of examples illustrates the effects of changes in the sphericity of spherical silicon carbide materials.

[0125] Example 11a The same procedure was followed as in Example 1, except that the sphericity of the spherical silicon-carbon material was 0.82.

[0126] Example 11b The same procedure was followed as in Example 1, except that the sphericity of the spherical silicon-carbon material was 0.98.

[0127] Comparative Example 1 The procedure was carried out in accordance with Example 1, except that the solid electrolyte material was replaced with the same amount of alumina particles by weight.

[0128] Comparative Example 2 The same procedure was followed as in Example 1, except that the Dv10 of the solid electrolyte material was changed to 0.025 μm.

[0129] Comparative Example 3 The same procedure was followed as in Example 1, except that the Dv10 of the solid electrolyte material was changed to 0.55 μm.

[0130] Comparative Example 4 The same procedure was followed as in Example 1, except that the coating thickness was adjusted to 0.2 μm.

[0131] Comparative Example 5 The same procedure was followed as in Example 1, except that the coating thickness was adjusted to 5.5 μm.

[0132] Comparative Example 6 The procedure was carried out in accordance with Example 1, except that the puncture intensity of the diaphragm was adjusted to 175 gf.

[0133] Comparative Example 7 The same procedure was followed as in Example 1, except that the sphericity of the spherical silicon-carbon material was 0.75.

[0134] Comparative Examples 8-9 The procedure was carried out in accordance with Example 1, except that the particle size distribution of the spherical silicon-carbon particles was changed, as detailed in Tables 1-7.

[0135] Table 1-7 Comparative Examples 10-11 The procedure is carried out in accordance with Example 1, except that S is changed. 1 / d 1 For details, please refer to Table 1-8.

[0136] Table 1-8 Test case The batteries prepared in the examples and comparative examples were subjected to the following tests.

[0137] 1. Low-temperature discharge performance test The obtained battery was placed in a constant temperature environment of 25℃ and discharged to 3.0V at 0.2C, then charged to 4.53V at a constant current and constant voltage of 0.7C with a cutoff current of 0.05C. After the battery was fully charged, it was left to stand for 5 minutes, and then discharged to the cutoff voltage of 3.0V at a constant current of 0.2C. The initial capacity of the battery was recorded as Q1. Subsequently, the battery was charged to 4.53V at a constant current and constant voltage of 0.7C with a cutoff current of 0.05C to fully charge it. The fully charged battery was then placed in an environment of -20℃ and left to stand for 4 hours. When the surface temperature of the battery reached the ambient temperature, it was discharged to 3.0V at 0.2C, and the discharge capacity was recorded as Q2. The low-temperature discharge capacity retention rate is calculated as Q2 / Q1×100%.

[0138] 2. High-temperature storage performance test At 45±2℃, the battery is charged at a constant current of 0.7C to the upper limit voltage of 4.53V, with a cutoff current of 0.05C. After standing for 5 minutes, it is discharged at a constant current of 0.2C to 3V. After standing for 5 minutes, the voltage is tested and recorded as the voltage before storage, U0.

[0139] The battery was stored in a constant temperature chamber at 65℃±2℃ for 28 days. After storage, the sample was removed and allowed to stand at 25℃±2℃ for 2 hours to allow it to return to room temperature. Once the sample had returned to room temperature, the battery was charged at a constant current of 0.7C to the upper limit voltage of 4.53V, with a cutoff current of 0.05C. After standing for 5 minutes, it was discharged at a constant current of 0.2C to 3V. After standing for 5 minutes, the voltage was measured and recorded as the voltage U1 after storage. The voltage drop U = U0 - U1.

[0140] 3. Ratio Performance Test At 25℃±2℃, the capacitor was charged at a constant current and constant voltage of 0.7C to 4.53V, cut off at 0.05C, and then discharged at a constant current of 0.2C to 3.0V. The initial discharge capacity is denoted as Q. 0 Let it stand for 10 minutes, then fully charge it at 0.7C (100% SOC), with a cutoff current of 0.05C, let it stand for 10 minutes, and then discharge it to 3V at a rate of 0.5C, let it stand for 10 minutes. The discharge capacity at this point is recorded as Q. 1 Capacity retention rate at 0.5C discharge rate at room temperature: Q 1 / Q 0 ×100%.

[0141] 4. 130℃ Hot Box Test The lithium-ion batteries were heated in a convection air chamber at an initial temperature of (25±3)℃ with a temperature change rate of (5±2)℃ / min, and then heated to (130±1)℃. The temperature was maintained for 60 minutes before the test was ended. The battery status was recorded. Six battery samples were tested for each example and comparative example. If the battery did not explode and / or catch fire, it was considered "passed". If it exploded or caught fire, it was considered "failed". The result was expressed as "number of passes / 6PASS". For example, "6 / 6PASS" means all passed, and "1 / 6PASS" means one of the six batteries passed.

[0142] The results are recorded in Table 2.

[0143] Table 2 As can be seen from Table 2, the comparative examples and the embodiment examples show that the battery prepared in the embodiment has a significantly improved low-temperature discharge capacity retention rate, a significantly reduced high-temperature storage voltage drop, and a significantly improved rate capacity retention rate. This indicates that by controlling the particle size of silicon-based particles, the Dv10 of the solid electrolyte material, the thickness of the coating, the puncture strength of the separator, and the relationship between fluoroethylene carbonate in the electrolyte and the Dv10 of the solid electrolyte material, the battery can have both high low-temperature performance, high rate performance, and low high-temperature storage voltage drop.

[0144] 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 negative electrode, a positive electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode. The separator includes a carrier layer, which includes a substrate layer and a coating on at least one surface of the substrate layer. The coating includes a solid electrolyte material with a Dv10 of 0.03 μm to 0.5 μm. The coating thickness is 0.3 μm to 5 μm, and the separator has a puncture strength of 200 gf to 700 gf. The negative electrode includes a negative current collector and a negative active layer located on at least one side surface of the negative current collector. The negative active layer includes a silicon-based material, which is a spherical silicon-carbon material with a sphericity of 0.8-1. The battery satisfies the following relationship: 0.75 ≤ (D 9 -D 1 ) / D 5 ≤1.5, where D 1 Dv10 of the spherical silicon-carbon material is expressed in μm. 5 Dv50 of the spherical silicon-carbon material is expressed in μm. 9 Dv90 of the spherical silicon-carbon material, in μm; The electrolyte comprises fluoroethylene carbonate, and the battery satisfies the following relationship: 0.2 ≤ S 1 / d 1 ≤5, where S 1 d represents the weight percentage of the fluoroethylene carbonate in the electrolyte. 1 Dv10 of the solid electrolyte material is expressed in μm.

2. The battery according to claim 1, wherein, The particle size of the spherical silicon-carbon material satisfies the following relationship: 0.8 ≤ (D 9 -D 1 ) / D 5 ≤1.25; And / or, the Dv50 of the spherical silicon carbide material is 5μm-10μm; And / or, the Dv90 of the spherical silicon carbide material is 9.5 μm-18 μm; And / or, the Dv10 of the spherical silicon carbide material is 2.5μm-6μm; And / or, the spherical silicon-carbon material comprises porous carbon and silicon particles at least partially located in the pores of the porous carbon; And / or, the puncture strength of the diaphragm is 250gf-600gf.

3. The battery according to claim 1, wherein, The weight percentage S of the fluoroethylene carbonate in the electrolyte 1 The percentage is 4%-30%, preferably 5%-25%.

4. The battery according to claim 1, wherein, The XRD spectrum of the solid electrolyte material includes a first characteristic peak and a second characteristic peak. The first characteristic peak is located at 20.5°-21.5°, and the second characteristic peak is located at 23.5°-24.5°. The battery satisfies the following relationship: 0.3 ≤ I 1 / I 2 ≤0.7, where I 1 I represents the intensity of the first characteristic peak. 2 The intensity of the second characteristic peak; And / or, the Dv50 of the solid electrolyte material is 0.05μm-5μm, preferably 0.1μm-4μm; And / or, the Dv90 of the solid electrolyte material is 0.1μm-9μm, preferably 0.3μm-6μm.

5. The battery according to claim 1, wherein, The solid electrolyte material includes one or more of the following: lithium lanthanum zirconium oxide solid electrolyte, lithium lanthanum zirconium tantalum oxide solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum titanium oxide solid electrolyte. And / or, the coating comprises a transition metal, which includes one or more of lanthanum, zirconium, and titanium; And / or, based on the total weight of the coating, the solid electrolyte material accounts for 30%-99% of the total weight; And / or, the coating is located on one side surface of the substrate layer, the coating is for the side facing the positive electrode, and the weight percentage of the transition metal in the coating is 2%-15%.

6. The battery according to claim 1, wherein, The coating further includes a second particle, the composition of which includes one or more of the following: alumina, boehmite, magnesium hydroxide, silicon dioxide, magnesium oxide, boron nitride, melamine, melamine cyanurate, melamine polyphosphate, aluminum diethylphosphite, 4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, guanine, 2-mercaptobenzimidazole, and 2-mercaptobenzimidazole derivatives; And / or, the coating further includes a first adhesive, the first adhesive comprising one or more of the following: fluoropolymer, polyimide, polyacrylonitrile, aramid resin, styrene-butadiene rubber, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose, sodium carboxymethyl cellulose, carboxyethyl cellulose, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, acrylic polymer, acrylate polymer, lithium polystyrene sulfonate, silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, and pure styrene latex; And / or, the coating is applied to the side facing the positive electrode; And / or, the diaphragm further includes an adhesive layer located on at least one side surface of the carrier layer, the adhesive layer comprising a first polymer and optionally filler particles, wherein the first polymer accounts for 20%-100% of the total weight of the adhesive layer and the filler particles account for 0%-80% of the total weight of the adhesive layer.

7. The battery according to claim 6, wherein, Based on the total weight of the coating, the weight percentage of the first adhesive is 1%-10%; And / or, based on the total weight of the coating, the weight percentage of the second particles is 0%-60%; And / or, the first polymer comprises one or more of the following: fluoropolymer, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, styrene-butadiene rubber, polyvinyl alcohol, polyimide, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, lithium polystyrene sulfonate, pure styrene latex, polyvinylpyrrolidone, polyethylene oxide, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. And / or, the filler particles are composed of one or more of the following: alumina, boehmite, magnesium oxide, magnesium hydroxide, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, melamine, melamine cyanurate, melamine polyphosphate, aluminum diethylphosphite, 4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, guanine, 2-mercaptobenzimidazole, and 2-mercaptobenzimidazole derivatives.

8. The battery according to claim 1, wherein, The separator further includes a coating layer located on at least one surface of the carrier layer, the coating layer comprising polymer particles, and the battery satisfies the following relationship: 9≤D 5 / k 1 ≤23, where k 1 The average particle size of the polymer particles is expressed in μm. Preferably, the average particle size k of the polymer particles 1 The micrometer size is 0.4μm-0.95μm, preferably 0.65μm-0.85μm; Preferably, the polymer particles comprise a second polymer, which includes one or more of the following: fluoropolymer, polyimide, polyacrylonitrile, polyimide, styrene-butadiene rubber, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, acrylate polymer, lithium polystyrene sulfonate, silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, and pure styrene latex.

9. The battery according to any one of claims 1-8, wherein, The positive electrode sheet includes a positive current collector and a positive active layer located on at least one side surface of the positive current collector. The positive active layer includes a positive active material with an average particle size of 3μm-20μm. And / or, the areal density of the coating is 0.5 g / m³. 2 -5g / m 2 The preferred value is 0.8 g / m 2 -4g / m 2 ; And / or, the positive electrode active layer in the positive electrode sheet further includes carbon nanotubes, the average diameter of which is 5nm-12nm; And / or, the negative electrode active layer includes a negative electrode active material, which includes a silicon-based material and optionally a graphite material, wherein the weight percentage of the silicon-based material is 1%-100% based on the total weight of the negative electrode active material; And / or, the electrolyte further includes an organic solvent and additives, wherein the organic solvent includes one or more of carbonates and carboxylic esters.

10. The battery according to claim 9, wherein, The positive electrode active material includes lithium cobalt oxide and optionally one or more of the following substances: lithium nickel oxide, lithium iron phosphate, lithium manganese oxide, and lithium nickel cobalt manganese oxide; And / or, the carbon nanotubes include one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes; And / or, the graphite material includes one or more of artificial graphite and natural graphite; And / or, the carbonate comprises one or more of the following solvents, either fluorinated or unsubstituted: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. And / or, the carboxylic acid ester includes one or more of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl butyrate, and n-ethyl butyrate. And / or, the additives include one or more of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, succinate, glutaronitrile, adiponitrile, heptonitrile, octanoic acid, sebaconitrile, 1,3,6-hexanetrionitrile, glyceryl trionitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,3-propanesulfonic acid lactone, and propenyl-1,3-sulfonic acid lactone.

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