Battery

Abstract

The invention provides a battery which comprises a battery cell and electrolyte, the battery cell comprises a positive plate, a diaphragm and a negative plate which are sequentially stacked and wound, the negative plate comprises a negative current collector and a negative active layer located on the surface of one side or two sides of the negative current collector, the negative active layer comprises a silicon-based material, the positive plate comprises a bonding piece, and the bonding piece comprises a silicon-based material. The bonding piece comprises a base material layer and an adhesive layer, the base material layer comprises a plurality of fibers and holes formed by the plurality of fibers, the aperture of the base material layer is 0.1-50 microns, and the electrolyte comprises difluoroethylene carbonate, fluoroethylene carbonate and non-fluorocarboxylic ester; the battery meets the following relational expressions: 0.01 < = a < = 3, 5 < = b < = 30, 5 < = d < = 45, and a%, b% and c% are respectively weight ratios of difluoroethylene carbonate, fluoroethylene carbonate and non-fluorocarboxylic ester in the electrolyte. The battery disclosed by the invention has relatively high energy density, good cycle performance and high-temperature cycle stability, and the serious lithium precipitation risk of the battery can be reduced.

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 continue to strive for higher battery life to meet consumers' growing demand for extended battery life in electronic products. Currently, lithium-ion batteries improve energy density by increasing the silicon-based material content of the negative electrode or by using ion-permeable binders in the positive electrode to improve the utilization rate of the positive electrode active material, thereby enhancing the performance and battery life of lithium-ion batteries.

[0003] However, as the silicon-based material content in the negative electrode of lithium-ion batteries increases, the silicon-based material is prone to volume expansion during cycling, which leads to the rupture of the solid electrolyte interphase (SEI) film. The repeated rupture and regeneration of the SEI film can easily increase the interfacial impedance, deteriorate the interfacial performance between the negative electrode and the electrolyte, and reduce the cycle performance of the battery.

[0004] Therefore, it is very important to invent a battery that can meet the demand for high "endurance" and improve the interfacial performance between the negative electrode and the electrolyte. Summary of the Invention

[0005] Studies have found that adding fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC) as film-forming additives to the electrolyte can suppress the volume expansion of silicon-based materials and improve the interfacial performance between the negative electrode and the electrolyte. FEC can be electrochemically reduced to generate an organic phase component mainly composed of fluoropolymers, which gives the SEI film excellent flexibility and can effectively buffer the SEI film rupture caused by the volume expansion of silicon-based materials during charging and discharging. Difluoroethylene carbonate, with its unique difluorinated structure, can provide an abundant fluorine source, promote the formation of inorganic LiF components with high mechanical strength in the SEI film, thereby suppressing the volume expansion effect of silicon-based materials. Therefore, through the synergistic effect of FEC and DFEC, the SEI film can have both flexibility and high mechanical strength, thereby suppressing the volume expansion of silicon-based materials and improving the cycle performance of the battery.

[0006] To improve the utilization rate of active materials, further enhance battery energy density, and meet the demand for high "range," the conventional adhesive components (non-ion-permeable adhesive paper) originally installed on the positive electrode are partially or completely replaced with ion-permeable adhesive components. While difluoroethylene carbonate and fluoroethylene carbonate can suppress the volume expansion of silicon-based materials and improve the interfacial performance of the negative electrode, their high viscosity increases the viscosity of the electrolyte. This weakens the ion-permeable effect of the adhesive components used in the positive electrode. Simultaneously, at high temperatures, the stability of the CF bonds in difluoroethylene carbonate and fluoroethylene carbonate decreases, easily generating more hydrofluoric acid (HF), which corrodes the adhesive components in the positive electrode, further weakening their ion-permeable effect. This reduces the utilization rate of the positive electrode active materials, adversely affecting battery energy density. Furthermore, HF corrosion can even cause the adhesive components to detach, compromising battery structural stability and reducing high-temperature cycle stability.

[0007] To simultaneously address the issues of decreased interfacial performance between the negative electrode and electrolyte due to silicon-based material expansion, reduced utilization of positive electrode active materials due to high hydrofluoric acid concentration in the electrolyte, and battery corrosion, this invention provides a battery. The battery of this invention can form a soft and mechanically strong SEI film on the surface of the silicon-based material, reducing the volume expansion of the silicon-based material. This improves the interfacial performance between the negative electrode and the electrolyte, enhancing the battery's cycle performance. Simultaneously, it reduces the concentration of hydrofluoric acid in the electrolyte, minimizing its corrosion of the bonding components and the battery itself, ensuring ion permeability of the bonding components. Therefore, the battery possesses both high high-temperature cycle performance and high energy density.

[0008] To achieve the above objectives, the present invention provides a battery comprising a cell and an electrolyte. The cell comprises a positive electrode, a separator, and a negative electrode, which are sequentially stacked and wound. The negative electrode comprises a negative current collector and a negative active layer located on one or both surfaces of the negative current collector, the negative active layer comprising a silicon-based material. The positive electrode comprises an adhesive, the adhesive comprising a substrate layer and an adhesive layer, the substrate layer comprising a plurality of fibers and pores formed by the plurality of fibers, the pore size of the substrate layer being 0.1 μm-50 μm. The electrolyte comprises difluoroethylene carbonate, fluoroethylene carbonate, and non-fluorocarboxylic acid esters; the battery satisfies the following relationship: 0.01≤a≤3, 5≤b≤30, 5≤d≤45, where a% is the weight percentage of difluoroethylene carbonate in the electrolyte, b% is the weight percentage of fluoroethylene carbonate in the electrolyte, and d% is the weight percentage of non-fluorocarboxylic acid esters in the electrolyte.

[0009] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The negative electrode of this invention comprises a silicon-based material, which effectively improves the battery's energy density and range. The ion-permeable adhesive in the positive electrode facilitates the lithium-ion insertion / extraction reaction of the positive electrode active material beneath it, thereby improving the utilization rate of the positive electrode active material and further enhancing the battery's energy density and range. Furthermore, the addition of difluoroethylene carbonate and fluoroethylene carbonate to the electrolyte allows them to synergistically form a high-strength and flexible SEI film on the surface of the silicon-based material. This reduces the volume expansion of the silicon-based material, improves the interfacial stability between the negative electrode and the electrolyte, and enhances the battery's cycle performance.

[0010] Meanwhile, a low-viscosity non-fluorinated carboxylic acid ester is added to the electrolyte of the battery of the present invention. This not only reduces the concentration of hydrofluoric acid in the electrolyte and reduces the corrosion of lithium-ion transmission paper by hydrofluoric acid, ensuring the ion transmission effect of the lithium-ion transmission paper and improving the energy density of the battery, but also reduces the viscosity of the electrolyte, improves the overall lithium-ion transport rate, improves the high-temperature cycle performance of the battery, enhances the kinetic performance of the battery, and reduces the risk of severe lithium plating due to insufficient kinetic performance of the negative electrode.

[0011] Simultaneously, by controlling the battery to satisfy the following relationships: 0.01≤a≤3, 5≤b≤30, 5≤d≤45, the matching degree of silicon-based materials, difluoroethylene carbonate, fluoroethylene carbonate, and non-fluorocarboxylic acid esters can be improved. This ensures the presence of appropriate amounts of difluoroethylene carbonate and fluoroethylene carbonate in the electrolyte. With the synergistic effect of difluoroethylene carbonate and fluoroethylene carbonate, a complete SEI film with both mechanical strength and flexibility can be formed in the silicon-based material of the negative electrode active layer. This improves or even avoids repeated rupture and regeneration of the SEI film, thereby improving the interfacial performance of the negative electrode and further enhancing the cycle performance of the battery. Simultaneously, with the synergistic effect of difluoroethylene carbonate, fluoroethylene carbonate, and non-fluorocarboxylic acid esters, the concentration of hydrofluoric acid in the electrolyte can be further reduced, the corrosion of the bonding components by hydrofluoric acid can be further reduced, and the energy density of the battery can be further improved. At the same time, the viscosity of the electrolyte can be reduced, the overall lithium-ion transport rate can be further improved, and the high-temperature cycle performance of the battery can be improved. Moreover, the lower viscosity electrolyte also has better wettability, which is conducive to further improving the kinetic performance of the battery and further reducing the risk of severe lithium plating. Thus, the battery has both high high-temperature cycle performance, high energy density, and reduced risk of severe lithium plating.

[0012] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0013] 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

[0014] Figure 1 The image shown is one of the cross-sectional schematic diagrams of the negative electrode sheet of the present invention.

[0015] Figure 2 The image shown is one of the surface schematic diagrams of the negative electrode sheet of the present invention.

[0016] Figure 3 The image shown is related to Figure 2 A schematic diagram of the opposite side of the surface shown.

[0017] Figure 4 The image shown is a second cross-sectional schematic diagram of the negative electrode sheet of the present invention.

[0018] Figure 5 The third cross-sectional schematic diagram of the negative electrode sheet of the present invention is shown.

[0019] Figure 6 The image shown is a second schematic diagram of the surface of the negative electrode sheet of the present invention.

[0020] Figure 7 The diagram shown is a schematic of the battery cell of the present invention. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] This invention provides a battery comprising a cell and an electrolyte. The cell comprises a positive electrode, a separator, and a negative electrode, which are sequentially stacked and wound. The negative electrode comprises a negative current collector and a negative active layer located on one or both surfaces of the negative current collector, the negative active layer comprising a silicon-based material. The positive electrode comprises an adhesive, the adhesive comprising a substrate layer and an adhesive layer. The substrate layer comprises a plurality of fibers and pores formed by the plurality of fibers, the pore size of the substrate layer being 0.1 μm-50 μm (e.g., 0.1 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm). The electrolyte comprises difluoroethylene carbonate, fluoroethylene carbonate, and non-fluorocarboxylic acid esters; the battery satisfies the following relationship: 0.01≤a≤3 (e.g., 0.01, 0.1, 0.5, 1, 1.5, 2, 2.5, or 3), 5≤b≤30 (e.g., 5, 10, 15, 20, 25, or 30), 5≤d≤45 (e.g., 5, 10, 15, 20, 25, 30, 35, 40, or 45), where a% is the weight percentage of difluoroethylene carbonate in the electrolyte, b% is the weight percentage of fluoroethylene carbonate in the electrolyte, and d% is the weight percentage of non-fluorocarboxylic acid esters in the electrolyte.

[0024] The negative electrode of the battery of this invention comprises silicon-based materials, which can effectively improve the energy density of the battery. However, silicon-based materials are prone to volume expansion during cycling, leading to the rupture of the negative electrode interface film (SEI film), deteriorating the interface performance of the negative electrode, and reducing the cycle performance of the battery. By adding difluoroethylene carbonate and fluoroethylene carbonate to the electrolyte, the fluoroethylene carbonate can participate in the formation of the SEI film, generating an organic phase component mainly composed of fluoropolymers, increasing the flexibility of the SEI film, buffering the volume expansion of the silicon-based material during charging and discharging, and preventing the SEI film from rupturing. The difluorosubstituted structure of the difluoroethylene carbonate can provide an abundant fluorine source, promoting the formation of inorganic LiF components with high mechanical strength in the SEI film. The difluoroethylene carbonate and fluoroethylene carbonate work synergistically to form a flexible and strong SEI film on the surface of the negative electrode, reducing the volume expansion of the silicon-based material while improving the interface stability of the negative electrode and enhancing the cycle performance of the battery.

[0025] To improve the utilization rate of positive electrode active materials and further enhance battery energy density, the conventional adhesives (non-ion-permeable adhesive paper) originally installed on the positive electrode sheet are partially or completely replaced with ion-permeable adhesives. This improves the battery's bonding stability while providing excellent lithium-ion permeability. The positive electrode active materials in the layer beneath the adhesive can undergo lithium-ion deintercalation / intercalation through the adhesive, increasing the utilization rate of the positive electrode active materials. Simultaneously, controlling the pore size of the substrate layer allows the electrolyte to flow and quickly permeate through it, further enhancing the ion permeability of the adhesive, improving its lithium-ion transport performance, and increasing battery energy density. It also reduces or even avoids excessive electrolyte interference affecting the adhesive's bonding strength, thus improving battery cycle stability. Furthermore, for example, the adhesives in the positive electrode sheet corresponding to the edge of the negative electrode sheet have excellent lithium-ion permeability, further improving the ion conductivity of the adhesive, reducing local concentration gradients, and reducing or even avoiding lithium-ion accumulation at the edge or defects of the negative electrode, preventing lithium deposition at the edge of the negative electrode sheet.

[0026] While introducing difluoroethylene carbonate and fluoroethylene carbonate into the electrolyte can suppress the volume expansion of silicon-based materials and improve the interfacial performance of the negative electrode, the high viscosity of difluoroethylene carbonate and fluoroethylene carbonate increases the electrolyte viscosity and weakens the ion permeability of the bonding components, which is not conducive to improving the energy density of the battery. In fact, the bonding components may even fall off under the corrosion of HF, reducing the stability of the battery structure and the high-temperature cycle stability of the battery.

[0027] The addition of non-fluorinated carboxylic acid esters to the electrolyte, with their lower viscosity, can reduce the viscosity of electrolyte systems containing difluoroethylene carbonate and fluoroethylene carbonate, thereby enhancing their ion transport capacity. This prevents the reduced ion permeability of the bonding components due to increased electrolyte viscosity, thus avoiding adverse effects on the battery's energy density. Simultaneously, it dilutes the difluoroethylene carbonate and fluoroethylene carbonate in the electrolyte, as well as the HF generated at high temperatures, preventing high-concentration HF from corroding the bonding components and reducing their ion permeability. Furthermore, it minimizes or even eliminates the stability reduction caused by bonding component detachment, improving the battery's high-temperature cycle stability. In addition, the addition of non-fluorinated carboxylic acid esters to the electrolyte results in lower viscosity, improving wettability and lithium-ion transport capacity, enhancing battery kinetic performance, and effectively preventing lithium plating caused by insufficient negative electrode kinetics.

[0028] Based on this, the battery is controlled to satisfy the following relationships: 0.01≤a≤3, 5≤b≤30, 5≤d≤45. Silicon-based materials, difluoroethylene carbonate, fluoroethylene carbonate, and non-fluorocarboxylic acid esters work synergistically to ensure that the electrolyte in the silicon-based anode system contains appropriate amounts of difluoroethylene carbonate and fluoroethylene carbonate. These difluoroethylene carbonate and fluoroethylene carbonate form a complete SEI film with both mechanical strength and flexibility in the anode active layer, improving or even preventing repeated rupture and regeneration of the SEI film, enhancing the interfacial performance between the anode and the electrolyte, and further improving the battery's cycle performance. Simultaneously, the difluoroethylene carbonate, fluoroethylene carbonate, and... Non-fluorinated carboxylic acid esters enable the electrolyte to have lower viscosity, while also reducing the concentration of hydrofluoric acid generated by difluoroethylene carbonate and fluoroethylene carbonate at high temperatures. This reduces the corrosion of the bonding components by hydrofluoric acid, ensuring good ion permeability of the bonding components, further improving the battery's energy density, enhancing the overall lithium-ion transport rate and battery structural stability, and further improving the battery's high-temperature cycle performance. Moreover, the lower viscosity electrolyte also has better wettability, further improving the battery's kinetic performance and reducing the risk of severe lithium plating on the negative electrode. As a result, the battery has good energy density and cycle performance, mitigating or eliminating lithium plating phenomena inside the battery.

[0029] In this invention, the pore size of the substrate layer in the adhesive is obtained by methods known in the art. One such method is described here: An adhesive sample is taken and immersed in a benzene solution for 4 hours. After drying, the sample is dried, and the pore size of the adhesive tape sample is measured using a pore size analyzer. The pore size with the largest proportion in the pore size distribution diagram is taken as the pore size of the adhesive. Note that the adhesive can also be immersed in organic solvents such as toluene; this application does not limit the type of immersion solvent.

[0030] In this invention, by controlling the battery to satisfy the following relationships: 0.01≤a≤3, 5≤b≤30, 5≤d≤45, compared with the prior art, the battery can achieve both high-temperature cycle performance, high energy density, and reduced risk of severe lithium plating. To further improve the effect, one or more of the technical features can be further optimized.

[0031] In some embodiments, the weight percentage (c%) of silicon in the negative electrode active layer is 2%-45% (e.g., 1%, 10%, 12%, 15%, 20%, 22%, 25%, 28%, 30%, 40%, 43% or 45%).

[0032] In this invention, the weight percentage of silicon in the negative electrode active layer can be measured by the following method: for example, after discharging the battery to 0% SOC, the negative electrode sheet is disassembled and removed. It is then soaked in dimethyl carbonate (DMC) solvent for 12 hours, followed by rinsing with DMC solvent to remove lithium salts adhering to the negative electrode sheet. After drying, the negative electrode sheet is subjected to high-temperature treatment at 400°C in an inert atmosphere for 2 hours (e.g., in a tube furnace under nitrogen or argon atmosphere). The negative electrode active layer can then be peeled off from the negative electrode current collector, and collected as a test sample. Using a thermogravimetric analyzer (e.g., a TGA 550 thermogravimetric analyzer), the sample amount is 5mg-15mg. Under an air or oxygen atmosphere, the temperature is increased from room temperature (25°C) to 900°C at a rate of 10°C / min, and held at 900°C for 40 minutes. This allows the non-silicon components in the negative electrode active layer to volatilize while the silicon is fully oxidized to silicon dioxide. The remaining substance is the ash of the negative electrode active layer. The weight ratio of silicon in the negative electrode active layer can be calculated based on the weight of the ash. The calculation formula is as follows: weight ratio of silicon in the negative electrode active layer = 7 × weight of ash / (15 × weight of test sample).

[0033] In some embodiments, the weight percentage of the silicon-based material in the negative electrode active layer is 3%-80% (e.g., 3%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 42%, 45%, 48%, 50%, 60%, 70% or 80%).

[0034] In some embodiments, the weight percentage of the difluoroethylene carbonate in the electrolyte is 0.05%-2%.

[0035] In some embodiments, the fluoroethylene carbonate accounts for 8%-25% by weight in the electrolyte.

[0036] In some embodiments, the non-fluorinated carboxylic acid ester includes one or more of propyl propionate, propyl acetate, ethyl propionate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate.

[0037] In some embodiments, the battery satisfies the following relationship: 0.2≤(a+b) / c≤10.

[0038] According to one specific implementation, a is 0.01-3, b is 5-30, and c is 2-45, and the battery satisfies the following relationship: 0.2≤(a+b) / c≤10.

[0039] According to one specific implementation, a is 0.05-2, b is 8-25, c is 2-45, and the battery satisfies the following relationship: 0.2≤(a+b) / c≤10.

[0040] In some embodiments, the silicon-based material comprises silicon-carbon particles, wherein the particle size distribution of the silicon-carbon particles satisfies: 0.3 μm ≤ Dv10 ≤ 6 μm (e.g., 0.3 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm).

[0041] In some embodiments, the silicon-based material comprises silicon-carbon particles with a particle size distribution satisfying: 1μm ≤ Dv50 ≤ 15μm (e.g., 1μm, 2μm, 3μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, or 15μm). Controlling the silicon-carbon particles to satisfy the above particle size distribution results in a narrower particle size distribution in the negative electrode, which improves the uniformity of the silicon-carbon particle size, reduces or even avoids the pulverization of silicon-carbon particles in the negative electrode, further reduces or even avoids repeated rupture of the SEI film, further improves the interfacial performance between the negative electrode and the electrolyte, and the densely packed uniform silicon-carbon particles reduce particle breakage and shedding, maintain contact with the negative electrode current collector, stabilize the SEI film, and make the negative electrode more conductive, thereby improving the conductivity and cycle stability of the negative electrode.

[0042] In some embodiments, the silicon-based material comprises silicon-carbon particles, the particle size distribution of which satisfies: 12μm≤Dv90≤25μm (e.g., 12μm, 14μm, 16μm, 18μm, 20μm, 22μm or 25μm).

[0043] In some embodiments, the silicon-based material comprises silicon-carbon particles, wherein the particle size distribution of the silicon-carbon particles satisfies: 0.3μm≤Dv10≤6μm, 1μm≤Dv50≤12μm, and 12μm≤Dv90≤25μm.

[0044] In this invention, the Dv10 particle size of the silicon-based material refers to the particle size corresponding to a cumulative volumetric particle size distribution percentage of 10% when the silicon-based materials are arranged from smallest to largest; the Dv50 particle size of the silicon-based material refers to the particle size corresponding to a cumulative volumetric particle size distribution percentage of 50% when the silicon-based materials are arranged from smallest to largest; and the Dv90 particle size of the silicon-based material refers to the particle size corresponding to a cumulative volumetric particle size distribution percentage of 90% when the silicon-based materials are arranged from smallest to largest. The volumetric particle size distribution of the silicon-based material can be obtained by measuring and statistically processing a 100μm × 100μm region on the surface of the negative electrode using SEM images of the negative electrode sheet, combined with image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv10, Dv50, and Dv90 of the silicon-based material can also be obtained by testing with a laser particle size analyzer.

[0045] In some embodiments, the silicon-based material may further include one or more of silicon-oxygen materials, elemental silicon materials, silicon-oxygen materials, silicon-nitrogen materials, and silicon alloy materials.

[0046] In some embodiments, the negative electrode active layer further includes a carbon-based material, a negative electrode conductive agent, and a negative electrode binder.

[0047] In some embodiments, the carbon-based material further includes at least one of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0048] In some embodiments, the negative electrode conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0049] In some embodiments, the negative electrode active layer comprises polyurethane.

[0050] Adding polyurethane to the negative electrode active layer can enhance the bonding strength of the negative electrode active layer, prevent the negative electrode active layer from falling off during cycling, keep the structure of the negative electrode sheet stable, reduce the side reactions between the negative electrode active layer and the electrolyte, enhance the weather resistance of the negative electrode sheet, reduce or even avoid the aging of the negative electrode sheet, and further improve the cycle performance of the battery.

[0051] In some embodiments, the polyurethane in the negative electrode active layer accounts for 0.2%-5% by weight (e.g., 0.2%, 0.5%, 1%, 2%, 3%, 4% or 5%).

[0052] In some embodiments, in addition to polyurethane, the negative electrode binder also includes one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), polyacrylic acid (PAA), sodium polymethyl cellulose (CMC-NA), and lithium polymethyl cellulose (CMC-Li).

[0053] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), polyacrylic acid (PAA), sodium polymethyl cellulose (CMC-NA), and lithium polymethyl cellulose (CMC-Li).

[0054] In some embodiments, in the negative electrode active layer, the graphite material accounts for 10%-94% by weight, the negative electrode conductive agent accounts for 0.1%-5% by weight, and the negative electrode binder accounts for 0.2%-5% by weight.

[0055] In some embodiments, such as Figure 1 , Figure 2 , Figure 3 As shown, the positive electrode 1 includes a coating area 11 and a tail empty foil area 12. The adhesive 13 is disposed at the junction of the coating area 11 and the tail empty foil area 12 to prevent the burrs in the tail coating area of ​​the positive electrode from piercing the separator. After replacing the conventional non-ion-permeable adhesive paper, it can improve the utilization rate of the positive electrode active material and increase the energy density of the battery.

[0056] In some embodiments, such as Figure 5 and Figure 6 As shown, the positive electrode 1 includes a positive current collector 15 and a positive tab 14. The adhesive 13 is disposed at the connection between the positive tab 14 and the positive current collector 15 to prevent the solder marks generated by welding the positive tab to the positive current collector from piercing the diaphragm. Furthermore, when the ion-permeable adhesive of this application replaces the conventional tab adhesive paper, it can improve the utilization rate of the positive active material originally covered by the tab adhesive paper and increase the energy density.

[0057] In some embodiments, such as Figure 7 As shown, along the winding direction J, the head of the positive electrode sheet includes a first bending region 16. The adhesive is disposed in the first bending region (disposed on at least one side surface of the positive electrode sheet bending region), which can improve the structural strength of the first bending region, make it more resistant to compressive stress, suppress the breakage of the positive electrode current collector caused by the expansion of the silicon-doped negative electrode, and after replacing conventional adhesive paper, can improve the utilization rate of the positive electrode active material in the bending region and increase the energy density.

[0058] In this invention, along the winding direction, the first bending area of ​​the positive electrode head refers to the arc-shaped area formed when the positive electrode is first bent during winding.

[0059] In some embodiments, the pore size of the substrate layer is 0.5 μm-20 μm.

[0060] In some embodiments, the fiber comprises one or more of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, and ethylene-propylene copolymer.

[0061] In some embodiments, the adhesive layer comprises inorganic particles and a binder, wherein the inorganic particles are composed of one or more of the following: alumina, boehmite, lithium aluminum titanium phosphate, lanthanum aluminum zirconate, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, cerium dioxide, nickel oxide, or titanium dioxide.

[0062] In some embodiments, the thickness of the substrate layer is 5μm-25μm; In some embodiments, the thickness of the adhesive layer is 2μm-18μm.

[0063] In some embodiments, the inorganic particles in the adhesive layer account for 30%-80% by weight (e.g., 90%, 91%, 92%, 93%, 94%, 95% or 96%).

[0064] In some embodiments, the adhesive comprises 20%-70% by weight in the adhesive layer (e.g., 4%, 5%, 6%, 7%, 8%, 9% or 10%).

[0065] In some embodiments, the adhesive comprises one or more of polyacrylate, polyacrylic acid, polyacrylate, polyisobutylene, styrene-isoprene copolymer, polyvinylidene fluoride, copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene and styrene-butadiene rubber.

[0066] In this invention, the coating area refers to the area on the surface of the positive current collector where a positive active layer exists, and the empty foil area refers to the area on the surface of the positive current collector where no positive active layer exists. The coating areas on both sides of the positive current collector can be the same or different.

[0067] In some embodiments, the positive electrode active layer further includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0068] In some embodiments, the positive electrode active material includes one or more of lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

[0069] In some embodiments, the positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene.

[0070] In some embodiments, in addition to polyurethane, the positive electrode binder may also include one or more of polyvinylidene fluoride (PVDF), acrylic-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0071] In some embodiments, in the positive electrode active layer, the weight percentage of the positive electrode active material is 80%-99.8%, the weight percentage of the positive electrode conductive agent is 0.1%-10%, and the weight percentage of the positive electrode binder is 0.1%-10%.

[0072] In some embodiments, the electrolyte includes an organic solvent, additives, and a lithium salt.

[0073] In some embodiments, the organic solvent includes at least one of carboxylic acid esters and carbonates.

[0074] In some embodiments, the organic solvent in the electrolyte accounts for less than or equal to 90% by weight (e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%).

[0075] In some embodiments, the carbonate comprises one or more solvents selected from the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0076] In some embodiments, the carboxylic acid ester comprises one or more of the following solvents, either fluorinated or unsubstituted: ethyl acetate, methyl acetate, methyl propionate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, propyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0077] In some embodiments, the carboxylic acid ester includes one or more of propyl propionate, propyl acetate, ethyl propionate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate.

[0078] In some embodiments, the electrolyte further includes ethyl fluoroacetate, which includes 2,2-difluoroethyl acetate and / or ethyl 2,2-difluoroacetate. Adding ethyl fluoroacetate to the electrolyte can reduce the viscosity of the electrolyte in the difluoroethylene carbonate and fluoroethylene carbonate systems, further improving the ion permeability of the bonding elements in the positive electrode and increasing the battery energy density. Furthermore, 2,2-difluoroethyl acetate has a high holo-molar orbital (HOMO) energy and a low LUMO energy, which helps promote the formation of an SEI film on the surface of silicon-carbon particles in the negative electrode, further improving the stability of the negative electrode electrolyte interface and enhancing the battery's cycle performance. Simultaneously, the high HOMO energy and low LUMO energy of 2,2-difluoroethyl acetate also give it strong antioxidant capabilities, making the electrolyte more difficult to oxidize, broadening the electrochemical stability window, improving battery stability at high voltages, and enhancing battery safety.

[0079] In some embodiments, the ethyl fluoroacetate comprises 3%-50% by weight in the electrolyte.

[0080] In some embodiments, the additives include one or more of the following: cyclic carbonate additives, cyclic sulfonyl lactone additives, phosphazene compounds, sulfur compounds, nitrile additives, and lithium salt additives.

[0081] In some embodiments, the additive accounts for less than or equal to 15% by weight in the electrolyte (e.g., 1%, 3%, 5%, 7%, 9%, 11%, 13%, or 15%).

[0082] In some embodiments, the electrolyte further includes a phosphazene compound, wherein the phosphazene compound comprises the structure shown in Formula I and / or Formula II: (Formula I); (Formula II) Among them, R 1 R 2 R 3 R 5 R 6 R 7 Each of the substituents is independently selected from O, substituted or unsubstituted C1-C10 alkyl groups, substituted or unsubstituted C1-C10 alkoxy groups, and the substituted substituent is a halogen.

[0083] In this invention, the alkyl group of C1-C10 is selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, neopentyl, cyclohexyl, n-hexyl, tert-octyl, and decyl.

[0084] In this invention, the alkoxy groups of C1-C10 are selected from at least one of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, tert-butoxy, n-pentoxy, neopentoxy, n-hexoxy, cyclohexoxy, n-heptoxy, n-octoxy, and n-decoxy.

[0085] In this invention, it can be understood that when R 1 R 2 R 3 R 5 R 6 R 7 When selected from one or more of substituted or unsubstituted C1-C10 alkyl or substituted or unsubstituted C1-C10 alkoxy groups, both the substituted or unsubstituted C1-C10 alkyl and the substituted or unsubstituted C1-C10 alkoxy groups can satisfy the structural requirements of Formula I and Formula II, with -CN attached to one side and P attached to the other side. Taking "methyl" as an example, when R 1 R 2 R 3 R 5 R 6 R 7 When methyl is selected, the structure of methyl is -CH2-.

[0086] In some embodiments, R 1 R 2 R 3 same.

[0087] In some embodiments, R 5 R 6 R 7 same.

[0088] Adding a phosphazene compound with the above-mentioned structure to the electrolyte allows the cyano group in the phosphazene compound to interact with protonated hydrogen, while the phosphorus atom interacts with the highly electronegative fluorine atom. This enables the adsorption of HF generated at high temperatures by difluoroethylene carbonate and fluoroethylene carbonate, significantly reducing the concentration of HF in the electrolyte. This reduces the corrosion of the bonding components by high-concentration HF, thereby reducing the decrease in the ion permeability of the bonding components and further reducing or even avoiding its adverse effects on the battery energy density. This ensures the stability of the bonding components and improves the high-temperature cycle stability of the battery.

[0089] In some embodiments, the phosphazene compound comprises one or more of the structures shown in Formulas I-1 to I-4 and II-1 to II-5: (Formula I-1) (Formula I-2) (Formula I-3) (Formula I-4) (Formula II-1) (Formula II-2) (Formula II-3) (Formula II-4) (Formula II-5); In some embodiments, the weight percentage of the phosphazene compound in the electrolyte is 0.1%-5% (0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4% or 5%).

[0090] In some embodiments, the weight percentage of the phosphazene compound in the electrolyte is 0.5%-2.5%.

[0091] In some embodiments, the electrolyte further includes sulfur-containing compounds, including one or more of vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate. Difluoroethylene carbonate and fluoroethylene carbonate in the electrolyte increase the interfacial impedance between the negative electrode and the electrolyte. Adding sulfur-containing compounds can form an SEI film containing sulfonyl groups (S(=O)2) on the surface of the negative electrode. The sulfonyl groups (S(=O)2) have strong polarity and can preferentially coordinate with lithium ions, reducing the activation energy required for lithium ion desolvation, allowing lithium ions to participate in the negative electrode reaction more efficiently, reducing the interfacial impedance between the negative electrode and the electrolyte, improving lithium ion kinetics, and further enhancing the battery's rate performance and cycle performance.

[0092] In some embodiments, the sulfur-containing compound in the electrolyte accounts for 0.1%-5% by weight (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4% or 5%).

[0093] In some embodiments, the sulfur-containing compound comprises 0.5%-3% by weight in the electrolyte.

[0094] In some embodiments, the nitrile additives include one or more of butadionitrile, glutaronitrile, adiponitrile, trans-butenedionitrile, trans-hexenedionitrile, 1,2-bis(cyanoethoxy)ethane, and 1,3,6-hexanetricarbonitrile.

[0095] In some embodiments, the cyclic carbonate additives include vinylene carbonate and / or ethylene ethylene carbonate.

[0096] In some embodiments, the cyclic sulfonyl lactone additives include one or more of 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, 2,4-butanesulfonyl lactone, and 1,4-butanesulfonyl lactone.

[0097] In some embodiments, the lithium salt additive includes one or more of lithium difluorooxalate borate, lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium dioxalate borate.

[0098] In some embodiments, the electrolyte further includes a lithium salt, which includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, and lithium tetrafluoroborate.

[0099] In some embodiments, the lithium salt in the electrolyte accounts for 10%-20% by weight (e.g., 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%).

[0100] In some instances, the battery is a lithium-ion rechargeable battery.

[0101] 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.

[0102] Example 1 (1) Preparation of positive electrode The positive electrode active material (lithium cobalt oxide), positive electrode binder (polyvinylidene fluoride (PVDF)), and positive electrode conductive agent (conductive carbon black (Super P)) 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 uniform positive electrode slurry. Subsequently, the positive electrode slurry was coated onto both sides of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the desired positive electrode sheet was obtained. An adhesive component (such as...) was provided at the junction of the coated area and the empty foil area at the tail of the positive electrode sheet. Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown), the adhesive layer includes a substrate layer and an adhesive layer. The adhesive layer includes inorganic particles and a binder. The pore size of the substrate layer is 7.8 μm. The fiber composition includes polyethylene terephthalate. The inorganic particle composition includes alumina. The binder includes polyisobutylene.

[0103] (2) Preparation of negative electrode Carbon-based materials (artificial graphite), silicon-based materials (spherical silicon carbide particles), negative electrode conductive agent (conductive carbon black (Super P)), and negative electrode binder (sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a weight ratio of 1:4) were mixed in an aqueous solvent at a weight ratio of 87.5:10:1:1.5. The mixture was continuously stirred in a mixer to form a uniform and flowing negative electrode slurry. The negative electrode slurry was coated on both sides of a negative electrode current collector (copper foil) with a thickness of 10 μm. The slurry was then dried in a vacuum oven at 120°C for 6 hours. After rolling and slitting, the required negative electrode sheet was obtained. The negative electrode was then prepared by pressing with a mold. The silicon carbide particle Dv50 was 7.8 μm, and the weight percentage of silicon in the negative active layer was 5% (a = 5).

[0104] (3) Electrolyte preparation In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), ethylene carbonate, propylene carbonate, propyl propionate, and propyl acetate solvents were mixed to form a homogeneous solvent. Then, 16% LiPF6, 3% nitrile additives (1,3,6-hexanetrionitrile (HTCN) and adiponitrile (ADN) in a weight ratio of 2:1), 18.5% fluoroethylene carbonate (FEC, b = 18.5), and 1.2% difluoroethylene carbonate (DFEC, a = 1.2) based on the total weight of the electrolyte were slowly added to the mixed solution. After stirring until homogeneous, the desired electrolyte was obtained. The electrolyte contained 28% non-fluorinated carboxylic esters (propyl propionate and propyl acetate) by weight (d = 28), with the remainder being non-fluorinated carbonates (ethylene carbonate and propylene carbonate in a mass ratio of 1:1).

[0105] (4) Preparation of the diaphragm A diaphragm is obtained by coating a boehmite layer on the side of a polyethylene substrate facing the positive electrode and coating both sides with a polyvinylidene fluoride adhesive layer.

[0106] (5) Preparation of lithium-ion batteries After preparing the above-mentioned positive electrode sheet, separator, and negative electrode sheet into a bare cell by winding, the cells are fixed with adhesive tape. Then, the bare cell is placed in an aluminum-plastic film package, and the prepared electrolyte is injected into the dried bare cell. After vacuum sealing, room temperature standing, and high temperature formation, the desired lithium-ion battery is obtained. The adhesive tape at the connection between the positive electrode tab and the positive current collector is a conventional adhesive tape (not permeable to ions and electrolyte), and the adhesive tape at the first bending area of ​​the positive electrode head is a conventional adhesive tape (not permeable to ions and electrolyte).

[0107] The battery satisfies the following relationship: (a+b) / c=(1.2+18.5) / 5=3.94.

[0108] Example 2 group This set of examples illustrates the effects that occur when (a+b) / c and c change.

[0109] This embodiment group is carried out with reference to Embodiment 1, except that (a+b) / c and c are changed, as detailed in Table 1.

[0110] Table 1 Example 3 Group This set of examples illustrates the effects of adding phosphazene compounds to an electrolyte, and the specific selection of the phosphazene compound and / or the change in the weight percentage of the phosphazene compound.

[0111] This embodiment group is based on Example 1, except that a phosphazene compound is added to the electrolyte. The specific selection of the phosphazene compound is changed and / or the weight ratio of non-fluorinated carbonate in the electrolyte is adjusted, so that the weight ratio of the phosphazene compound is changed. See Table 2 for details.

[0112] Table 2 Example 4 group This set of examples illustrates the effects of adding sulfur-containing compounds to an electrolyte, and the specific selection of the sulfur-containing compound and / or the change in the weight percentage of the sulfur-containing compound in the electrolyte.

[0113] This embodiment group is based on Example 1, except that a sulfur-containing compound is added to the electrolyte. The specific selection of the sulfur-containing compound is changed and / or the weight ratio of non-fluorinated carbonates in the electrolyte is adjusted, so that the weight ratio of sulfur-containing compounds in the electrolyte is changed. See Table 3 for details.

[0114] Table 3 Example 5 group This set of examples illustrates the effects of adding ethyl fluoroacetate to the electrolyte, which alters the weight percentage of ethyl fluoroacetate in the electrolyte.

[0115] This embodiment group is based on Example 1, except that ethyl fluorocarbonate is added to the electrolyte to adjust the weight ratio of non-fluorinated carbonate in the electrolyte, thereby changing the weight ratio of ethyl fluorocarbonate in the electrolyte, as detailed in Table 4.

[0116] Table 4 Example 6 group This set of examples illustrates the effects of changes in the pore size of the substrate layer.

[0117] This embodiment group is based on Embodiment 1, except that the pore size of the substrate layer is changed, as detailed in Table 5.

[0118] Table 5 Example 7 group This set of examples illustrates the effects of changes in the Dv50 of silicon carbide particles.

[0119] Example 7-1 This embodiment group is based on Embodiment 1, except that the silicon-carbon particles Dv50 in the negative electrode are 1.1 μm.

[0120] Example 7-2 This embodiment group is based on Embodiment 1, except that the silicon-carbon particles Dv50 in the negative electrode is 14.9 μm.

[0121] Example 8 group This set of examples illustrates the effects of replacing the negative electrode binder styrene-butadiene rubber (SBR) with polyurethane and changing the weight percentage of polyurethane in the negative electrode active layer.

[0122] Example 8-1 This embodiment group is based on Embodiment 1, except that the negative electrode binder styrene-butadiene rubber (SBR) is replaced with polyurethane, and the weight ratio of carbon-based materials in the negative electrode active layer is adjusted so that the weight ratio of polyurethane in the negative electrode active layer is 0.2%.

[0123] Example 8-2 This embodiment group is based on Embodiment 1, except that the negative electrode binder styrene-butadiene rubber (SBR) is replaced with polyurethane, and the weight ratio of carbon-based materials in the negative electrode active layer is adjusted so that the weight ratio of polyurethane in the negative electrode active layer is 5%.

[0124] Example 8-3 This embodiment group is based on Embodiment 1, except that the negative electrode binder styrene-butadiene rubber (SBR) is replaced with polyurethane, and the weight ratio of carbon-based materials in the negative electrode active layer is adjusted so that the weight ratio of polyurethane in the negative electrode active layer is 0.1%.

[0125] Example 8-4 This embodiment group is based on Embodiment 1, except that the negative electrode binder styrene-butadiene rubber (SBR) is replaced with polyurethane, and the weight ratio of carbon-based materials in the negative electrode active layer is adjusted so that the weight ratio of polyurethane in the negative electrode active layer is 6.2%.

[0126] Example 9 group This set of examples illustrates the effects that occur when the position of the adhesive component changes.

[0127] Example 9-1 This embodiment is based on Embodiment 1, except that it is located in the first bending area at the head of the positive electrode (e.g., Figure 7 The conventional adhesive tape shown is replaced with an adhesive piece (the same adhesive piece set at the junction of the coating area and the empty foil area at the tail of the positive electrode).

[0128] Example 9-2 This embodiment is based on Embodiment 1, except that the adhesive is located at the junction of the positive electrode coating area and the empty foil area at the tail (e.g., Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown), the adhesive component is located at the connection between the positive electrode tab and the positive current collector (e.g. Figure 5 and Figure 6 As shown), the adhesive is located in the first bending area of ​​the positive electrode head (e.g. Figure 7 (As shown).

[0129] Example 10 This embodiment is based on Example 1, except that the weight percentage of difluoroethylene carbonate in the electrolyte is 0.3% (a = 0.3%), the weight percentage of fluoroethylene carbonate in the electrolyte is 10% (b = 10%), the weight percentage of non-fluorocarboxylic acid esters in the electrolyte is 10% (d = 10%), the weight percentage of ethyl fluoroacetate in the electrolyte is 30%, the specific selection of the phosphazene compound is Formula II-5, the weight percentage of the phosphazene compound in the electrolyte is 0.5%, the weight percentage of the nitrile compound in the electrolyte is 2.5%, and the weight percentage of the sulfur-containing compound is... Specifically, mannitol carbonate sulfate was chosen, with sulfur-containing compounds accounting for 3% of the electrolyte by weight, and the remainder being non-fluorinated carbonate accounting for 27.7% by weight. The silicon carbon particles had a Dv50 of 9 μm. The weight ratios of carbon-based materials, silicon-based materials, and negative electrode binders in the negative electrode active layer were adjusted so that the weight ratio of silicon in the negative electrode active layer was 10% (c = 10), (a+b) / c = (0.3+10) / 10 = 1.03, the weight ratio of polyurethane in the negative electrode active layer was 0.3%, and the pore size of the substrate layer in the adhesive was 3.2 μm.

[0130] Example 11 This embodiment is based on Example 1, except that the weight percentage of difluoroethylene carbonate in the electrolyte is 1.5% (a = 1.5%), the weight percentage of fluoroethylene carbonate in the electrolyte is 15% (b = 15%), the weight percentage of non-fluorocarboxylic acid esters in the electrolyte is 35% (d = 35%), the weight percentage of fluoroethyl acetate in the electrolyte is 8%, the specific selection of the phosphazene compound is Formula II-2, the weight percentage of the phosphazene compound in the electrolyte is 2.5%, the weight percentage of the nitrile compound in the electrolyte is 0.5%, and the sulfur-containing compound... The specific choice is vinyl sulfate, the weight percentage of sulfur-containing compounds in the electrolyte is 0.5%, the balance in the electrolyte is non-fluorinated carbonate, the weight percentage is 21%, the silicon carbon particle Dv50 is 13μm, the weight percentage of carbon-based materials, silicon-based materials and negative electrode binder in the negative electrode active layer is adjusted so that the weight percentage of silicon element in the negative electrode active layer is 20% (c is 20), (a+b) / c=(1.5+15) / 20=0.83, the weight percentage of polyurethane in the negative electrode active layer is 0.6%, and the pore size of the substrate layer in the adhesive is 10μm.

[0131] Comparative Example 1 This embodiment is based on Example 1, except that the weight percentage of difluoroethylene carbonate in the electrolyte is 5% (a is 5), the weight percentage of fluoroethylene carbonate in the electrolyte is 18.5% (b is 18.5), and the weight percentage of silicon in the negative electrode active layer is 45% (c is 45). (a+b) / c=(5+18.5) / 45=0.52.

[0132] Comparative Example 2 This embodiment is based on Example 1, except that the weight percentage of difluoroethylene carbonate in the electrolyte is 1.2% (a is 1.2), the weight percentage of fluoroethylene carbonate in the electrolyte is 2% (b is 2), and the weight percentage of silicon in the negative electrode active layer is 5% (c is 5). (a+b) / c=(1.2+2) / 5=0.64.

[0133] Comparative Example 3 This embodiment is based on Example 1, except that the weight percentage of difluoroethylene carbonate in the electrolyte is 1.2% (a is 1.2), the weight percentage of fluoroethylene carbonate in the electrolyte is 35% (b is 35), and the weight percentage of silicon in the negative electrode active layer is 5% (c is 5). (a+b) / c=(1.2+35) / 5=7.24.

[0134] Comparative Example 4 This embodiment is based on Embodiment 1, except that the pore size of the substrate layer is 0.01 μm.

[0135] Comparative Example 5 This embodiment is based on Embodiment 1, except that the pore size of the substrate layer is 55 μm.

[0136] Comparative Example 6 This embodiment is based on Example 1, except that the electrolyte does not contain difluoroethylene carbonate.

[0137] Comparative Example 7 This embodiment is based on Example 1, except that the electrolyte does not contain fluoroethylene carbonate.

[0138] Comparative Example 8 This embodiment is based on Embodiment 1, except that the battery has no adhesive components, and the junction between the positive electrode coating area and the tail empty foil area is a non-porous conventional adhesive paper (which does not allow ions and electrolyte to pass through).

[0139] Test case The batteries prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 6: (1) Cycling capacity retention and lithium plating at 25℃: At 25℃±2℃, the battery was charged at a constant current of 1.2C to 4.25V, then charged at 0.7C to the upper limit voltage of 4.53V, then continued to be charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.7C to 3V, left to stand for 5 minutes. The initial discharge capacity was recorded as C. 0 Cyclic charging method: Charge at a constant current of 1.2C to 4.25V, then switch to 0.7C charging to the upper limit voltage of 4.53V, then continue constant voltage charging to 0.05C, rest for 5 minutes, then discharge at a constant current of 0.7C to 3V. After 800 cycles, record the discharge capacity as C. 1 The capacity retention rate is (C 1 / C 0 )×100%.

[0140] Lithium plating situation: The battery, after being cycled 800T at 25℃, was charged to 4.53V using a constant current and constant voltage of 0.7C, with a cutoff current of 0.05C. It was then allowed to stand for 10 minutes. The battery was then disassembled, and the negative electrode was removed. The criteria for judging the lithium plating on the negative electrode were: no lithium plating < slight lithium plating < lithium plating < severe lithium plating. 1) No lithium plating; 2) Slight lithium plating, with a lithium plating area less than 10%, has a relatively small impact on the battery and can be used normally; 3) Lithium plating, with a lithium plating area of ​​10%-50% on the surface of the negative electrode; 4) Severe lithium plating, with a lithium plating area greater than 50% on the surface of the negative electrode.

[0141] (2) Capacity retention rate during 45℃ cycling: At 45℃±2℃, the battery was charged at a constant current of 1.2C to 4.25V, then charged at 0.7C to the upper limit voltage of 4.53V, then continued to be charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.7C to 3V, left to stand for 5 minutes. The initial discharge capacity was recorded as C. 0 Cyclic charging method: Charge at a constant current of 1.2C to 4.25V, then switch to 0.7C charging to the upper limit voltage of 4.53V, then continue constant voltage charging to 0.05C, rest for 5 minutes, then discharge at a constant current of 0.7C to 3V. After 200 cycles, record the discharge capacity as C. 1 The capacity retention rate is (C 1 / C 0 )×100%.

[0142] (3) Volumetric energy density: The battery was left to stand for 1 hour at (25±2)℃. It was then charged at a constant current of 0.5C to 4.53V, followed by constant voltage charging at 4.53V to a current of 0.05C, and left to stand for 10 minutes. Next, it was discharged at a constant current of 0.2C to 3V and left to stand for 10 minutes. The discharge capacity was recorded as Q, the average discharge plateau voltage as V, and the lithium-ion battery thickness as H, length as Y, width as Z, and volumetric energy density as (Q×V) / (H×Y×Z).

[0143] Table 6 " / " indicates that it has not been tested. As shown in Table 6, by comparing the comparative example and the embodiment, the embodiment shows improved room temperature cycling capacity retention and significantly improved lithium plating. This indicates that by controlling the battery to meet the following relationships: 0.01≤a≤3, 5≤b≤30, 5≤d≤45, good ion permeability of the bonding component is ensured, and the overall lithium ion transport rate and battery structural stability are improved. Furthermore, the wettability of the electrolyte is enhanced, the battery's kinetic performance is improved, and the risk of severe lithium plating on the negative electrode is reduced. Thus, the battery possesses high high-temperature cycling performance, high room temperature cycling performance, and high rate performance.

[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 cell and an electrolyte. The cell includes a positive electrode, a separator, and a negative electrode, which are sequentially stacked and wound. The negative electrode includes a negative current collector and a negative active layer located on one or both surfaces of the negative current collector. The negative active layer includes a silicon-based material. The positive electrode includes an adhesive, which includes a substrate layer and an adhesive layer. The substrate layer includes a plurality of fibers and pores formed by the fibers. The pore size of the substrate layer is 0.1 μm-50 μm. The electrolyte comprises difluoroethylene carbonate, fluoroethylene carbonate, and non-fluorocarboxylic acid esters; the battery satisfies the following relationship: 0.01≤a≤3, 5≤b≤30, 5≤d≤45, where a% is the weight percentage of difluoroethylene carbonate in the electrolyte, b% is the weight percentage of fluoroethylene carbonate in the electrolyte, and d% is the weight percentage of non-fluorocarboxylic acid esters in the electrolyte.

2. The battery according to claim 1, wherein, In the negative electrode active layer, the weight percentage (c%) of silicon is 2%-45%. And / or, in the electrolyte, the weight percentage of the difluoroethylene carbonate is 0.05%-2%; And / or, in the electrolyte, the weight percentage of the fluoroethylene carbonate is 8%-25%; And / or, the non-fluorinated carboxylic acid esters include one or more of propyl propionate, propyl acetate, ethyl propionate, ethyl acetate, methyl acetate, methyl butyrate, ethyl butyrate, and methyl propionate.

3. The battery according to claim 2, wherein, The battery satisfies the following relationship: 0.2≤(a+b) / c≤10.

4. The battery according to claim 1, wherein the pore size of the substrate layer is 0.5 μm-20 μm; And / or, the fiber composition includes one or more of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, and ethylene-propylene copolymer; And / or, the adhesive layer comprises inorganic particles and a binder, wherein the inorganic particles comprise one or more of the following: alumina, boehmite, lithium aluminum titanium phosphate, lanthanum aluminum zirconate, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, cerium dioxide, nickel oxide, or titanium dioxide; and the binder comprises one or more of the following: polyacrylate, polyacrylic acid, polyacrylate, polyisobutylene, styrene-isoprene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber. And / or, the thickness of the substrate layer is 5μm-25μm; And / or, the thickness of the adhesive layer is 2μm-18μm.

5. The battery according to claim 1, wherein, The electrolyte also includes ethyl fluoroacetate, which includes 2,2-difluoroethyl acetate and / or ethyl 2,2-difluoroacetate; Preferably, the weight percentage of the ethyl fluoroacetate in the electrolyte is 3%-50%.

6. The battery according to claim 1, wherein, The electrolyte further includes phosphazene compounds, wherein the phosphazene compounds comprise the structures shown in Formula I and / or Formula II: (Formula I); (Formula II) Among them, R 1 R 2 R 3 R 5 R 6 R 7 Each of the substituents is independently selected from O, substituted or unsubstituted C1-C10 alkyl groups, substituted or unsubstituted C1-C10 alkoxy groups, and the substituted substituents are halogens; Preferably, the phosphazene compound comprises one or more of the structures shown in Formulas I-1 to I-4 and II-1 to II-5: (Equation I-1) (Formula I-2) (Formula I-3) (Formula I-4) (Formula II-1) (Formula II-2) (Formula II-3) (Formula II-4) (Formula II-5); Preferably, the weight percentage of the phosphazene compound in the electrolyte is 0.1%-5%.

7. The battery according to claim 1, wherein, The electrolyte also includes sulfur-containing compounds, which include one or more of vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate. Preferably, the sulfur-containing compound accounts for 0.1%-5% by weight in the electrolyte.

8. The battery according to claim 1, wherein, The positive electrode sheet includes a coated area and a tail empty foil area, and the adhesive is disposed at the junction of the coated area and the tail empty foil area; And / or, the positive electrode sheet includes a positive current collector and a positive electrode tab, and the adhesive is disposed at the connection between the positive electrode tab and the positive current collector; And / or, along the winding direction, the head of the positive electrode includes a first bending region, and the adhesive is disposed in the first bending region.

9. The battery according to claim 1, wherein, The silicon-based material includes silicon-carbon particles, and the particle size distribution of the silicon-carbon particles satisfies: 1μm≤Dv50≤15μm; And / or, the negative electrode active layer comprises polyurethane, preferably, the weight percentage of the polyurethane in the negative electrode active layer is 0.2%-5%.

10. The battery according to claim 1, wherein, The electrolyte also includes lithium salts, which include one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate. Preferably, the lithium salt accounts for 10%-20% by weight in the electrolyte.

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