A battery and an electric device

Abstract

This invention provides a battery and an electrical device, including a positive electrode sheet comprising a positive electrode active material, the positive electrode active material being doped with and / or coated with aluminum; a negative electrode sheet comprising a negative electrode active material, the negative electrode active material comprising silicon particles; an electrolyte comprising a first solvent, a second solvent, a first additive, a second additive, and a third additive; the first solvent comprising ethyl 2,2-difluoroacetate, the second solvent comprising propylene carbonate, the first additive comprising 1,3-propanesulfonate lactone, the second additive comprising vinyl sulfate, and the third additive comprising succinate; this invention, through the synergistic design of a full battery system of "aluminum-modified positive electrode + silicon-based negative electrode + multifunctional composite electrolyte," achieves excellent low-temperature discharge performance, ultra-long cycle life, high interface stability, and outstanding thermal safety characteristics while maintaining high energy density.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a battery and an electrical device. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and low self-discharge rate, have been widely used in consumer electronics such as smartphones and laptops, as well as in new energy fields such as electric vehicles and energy storage systems. To meet the ever-increasing demand for energy density, silicon-based anode materials, with their advantages of high theoretical specific capacity (~4200 mAh / g) and abundant resources, have become an important direction for replacing traditional graphite anodes. However, when the mass fraction of silicon in the anode reaches 5% or higher, it undergoes a dramatic volume expansion and contraction of over 300% during lithiation / delithiation, leading to electrode particle pulverization, conductive network breakage, and repeated rupture and regeneration of the solid electrolyte interphase (SEI) film. This process continuously consumes electrolyte and active lithium ions, causing not only irreversible capacity loss and a decrease in coulombic efficiency, but also generating a large amount of gas, increasing the internal pressure of the battery, and in severe cases inducing thermal runaway, significantly restricting the safety and cycle life of the battery.

[0003] Meanwhile, under high-voltage charging conditions, the surface of the cathode material (such as high-nickel ternary or lithium-rich manganese-based oxides) is prone to oxidative decomposition of the electrolyte, accompanied by the reaction of transition metal ions (such as Ni). 2+ Co 3+ Mn 4+ The dissolved metal ions can migrate to the negative electrode and embed themselves in the SEI layer, catalyzing its further decomposition and forming a vicious cycle of "positive electrode instability - negative electrode poisoning". This leads to accelerated capacity decay and a sharp increase in impedance during battery storage or cycling at high temperatures (such as 45–60°C).

[0004] To alleviate the aforementioned problems, existing technologies mainly rely on electrolyte additives to modify the electrode interface. For example, ethylene sulfate (FEC) can be preferentially reduced on the surface of silicon-based anodes to generate a lithium fluoride (LiF)-rich SEI layer, effectively improving the interfacial mechanical strength and chemical stability. However, excessive FEC addition (typically >10 wt%) leads to an overly thick SEI and a significant increase in interfacial impedance, which in turn deteriorates rate performance and low-temperature output capability. Therefore, overcoming the aforementioned technical problems and defects has become a key issue that needs to be addressed. Summary of the Invention

[0005] In view of the problem that the cycle performance of lithium-ion batteries deteriorates significantly under high and low temperature environments in the prior art, the present invention provides a battery and an electrical device.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: This invention provides a battery, comprising: A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on the positive current collector, the positive active material comprising a positive active material, the positive active material being doped with and / or coated with aluminum. A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material comprising a negative electrode active material comprising silicon particles; An electrolyte comprising a first solvent, a second solvent, a first additive, a second additive, and a third additive; the first solvent comprising ethyl propionate, the second solvent comprising propylene carbonate, the first additive comprising 1,3-propanesulfonate lactone, the second additive comprising vinyl sulfate, and the third additive comprising succinate.

[0007] Optionally, the mass percentage Q of aluminum in the positive electrode active material layer is expressed as %, and the value of Q ranges from 0.4 to 2.

[0008] Optionally, the D50 particle size of the silicon particles in the negative electrode active material layer is W, with the unit being μm, and the value of W is in the range of 2≤W≤20.

[0009] Optionally, taking the total mass of the electrolyte as 100%, the mass percentage of the first solvent in the electrolyte is denoted as A, in %, and the value of A ranges from 5 to 40; the mass percentage of the second solvent in the electrolyte is denoted as B, in %, and the value of B ranges from 5 to 30; the mass percentage of the first additive in the electrolyte is denoted as X, in %, and the value of X ranges from 0.5 to 5; the mass percentage of the second additive in the electrolyte is denoted as Y, in %, and the value of Y ranges from 0.2 to 2; and the mass percentage of the third additive in the electrolyte is denoted as Z, in %, and the value of Z ranges from 0.5 to 5.

[0010] Optionally, it also includes a diaphragm, the porosity of which is P, in the unit of %, and the value of P ranges from 20 to 70.

[0011] Optionally, the A value, the B value, the X value, the Y value, the Z value, the Q value, the W value, and the P value satisfy the following conditions: Equation 1: 0.23 ≤ B / A ≤ 3.38; Equation 2: 2.13 ≤ (P+A) / W ≤ 33.33; Equation 3: 0.04≤Y / (X+Z)≤0.75; Formula 4: 0.11≤(X+Y+Z) / Q≤1.90.

[0012] Optionally, the A value, the B value, the X value, the Y value, the Z value, the Q value, the W value, and the P value satisfy the following conditions: Equation 5: 0.25 ≤ B / A ≤ 2.00; Equation 6: 3.00 ≤ (P+A) / W ≤ 30.00; Equation 7: 0.05≤Y / (X+Z)≤0.50; Formula 8: 0.23≤(X+Y+Z) / Q≤1.18.

[0013] Optionally, the positive electrode active material may further include one or more of the following: transition metal lithium oxides, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate, which are doped with and / or coated with aluminum.

[0014] Optionally, the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0015] One aspect of the present invention provides an electrical device, including the battery described above.

[0016] According to the battery provided by the present invention, the present invention significantly improves the low-temperature performance, cycle stability, interface stability, and thermal safety of the battery while ensuring high energy density through the synergistic optimization design of the positive electrode, negative electrode, and electrolyte. Firstly, the electrolyte of the present invention uses ethyl propionate (EP) as the first solvent, which is a low-viscosity, low-melting-point linear ester solvent. This effectively reduces the overall viscosity of the electrolyte and optimizes the solvation structure of lithium ions at low temperatures, thereby significantly improving ionic conductivity. Therefore, even in low-temperature environments such as 0°C, the battery can still maintain good lithium-ion diffusion kinetics and rapid charge transfer capability, effectively mitigating capacity loss and power decay caused by low temperatures. Secondly, the negative electrode active material of the present invention contains silicon particles, which, although possessing high specific capacity, are prone to SEI film rupture and continuous side reactions due to volume expansion. This invention uses propylene carbonate (PC) as a second solvent, which utilizes its high dielectric constant to promote the dissociation of lithium salt and preferentially reduce it on the surface of silicon-carbon anode to form a dense SEI layer rich in inorganic components such as Li2CO3; at the same time, 1,3-propanesulfonate lactone (PS) is introduced as a first additive, which preferentially reduces and undergoes ring-opening polymerization during the first charge and discharge process to generate a flexible SEI film rich in alkyl sulfonate lithium with high ionic conductivity. This composite SEI structure effectively adapts to the significant volume changes of silicon particles during cycling and significantly inhibits the continuous decomposition of the electrolyte and the irreversible consumption of active lithium, thereby greatly extending the battery cycle life. Thirdly, the electrolyte further includes vinyl sulfate (DTD) as a second additive, which has both positive and negative electrode film-forming functions: on the positive electrode surface, it oxidizes to form a dense CEI film rich in Li2SO4, effectively inhibiting electrolyte oxidation and transition metal dissolution under high voltage; on the negative electrode side, it works synergistically with PS to introduce Li2SO4 components into the SEI, improving the mechanical strength, density, and lithium-ion migration ability of the SEI, achieving simultaneous strengthening of the positive and negative electrode interfaces. Fourthly, the electrolyte also contains succinate (SN) as a third additive, whose molecule contains a strongly coordinating cyano (-CN) functional group, which can efficiently chelate harmful impurities such as residual water, HF, and transition metal ions in the electrolyte, blocking their corrosive effect and catalytic decomposition pathway on the SEI / CEI film, thereby effectively suppressing gas generation, impedance growth, and thermal runaway risks, and significantly improving the safety performance of the battery under high-temperature storage or abuse conditions; fifthly, the positive electrode active material is modified by aluminum doping and / or coating, which not only improves the crystal structure stability of the material and suppresses phase transition and oxygen evolution during charging and discharging, but also improves the electron and ion transport channels. Combined with the above-mentioned stabilized electrolyte system, the degradation of the positive electrode interface can be effectively delayed, and the capacity retention rate under high voltage and long cycle conditions can be improved. Detailed Implementation

[0017] To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0018] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0019] In one embodiment, the present invention provides a battery comprising: The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive active material layer includes a positive active material, which is doped with and / or coated with aluminum. A negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector. The negative active material layer includes a negative active material, which includes silicon particles. The electrolyte comprises a first solvent, a second solvent, a first additive, a second additive, and a third additive; the first solvent comprises ethyl propionate (EP), the second solvent comprises propylene carbonate (PC), the first additive comprises 1,3-propanesulfonyl lactone (PS), the second additive comprises vinyl sulfate (DTD), and the third additive comprises succinate (SN).

[0020] In some embodiments, the type of positive electrode current collector is not particularly limited, and it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, aluminum plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metallic material.

[0021] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent and a positive electrode binder.

[0022] In some embodiments, the type of positive conductive agent mentioned in this invention is not limited, and any known conductive agent can be used.

[0023] In some embodiments, the positive electrode conductive agent mentioned in this invention includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.

[0024] In one embodiment, the type of positive electrode binder mentioned in this invention is not limited, and any known positive electrode binder can be used.

[0025] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0026] In some embodiments, the silicon particles include carbon-coated silicon particles and silicon oxide (SiO2). x One or more of the following particles; in a preferred embodiment, the silicon particles are selected from carbon-coated silicon particles; In one embodiment, the negative electrode active material includes, but is not limited to, one or more combinations of graphite, hard carbon, silicon, silicon suboxide, silicon-carbon composite material, and lithium titanate, preferably designed in conjunction with the positive electrode and functionalized electrolyte to maximize the overall performance of the battery.

[0027] In some embodiments, there are no particular limitations on the negative current collector, as long as it can achieve the purpose of this application. For example, it can be copper foil, copper alloy foil, aluminum foil, stainless steel foil, titanium foil, aluminum foam, copper foam, or composite current collector, etc.

[0028] In some preferred embodiments, the negative current collector comprises copper foil.

[0029] In some embodiments, the negative electrode active material layer is disposed on at least one side surface of the negative electrode current collector, and the negative electrode active material layer further includes a negative electrode conductive agent, a negative electrode binder, a negative electrode thickener, and a negative electrode solvent.

[0030] The negative electrode conductive agent includes at least one of the following carbon materials: natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.

[0031] Negative electrode binders include styrene-butadiene latex, etc. Negative electrode thickeners include CMC, etc. Negative electrode solvents include deionized water, etc.

[0032] In some embodiments, the lithium-ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte described above.

[0033] This invention provides a lithium-ion battery that, through the synergistic optimization design of the positive electrode, negative electrode, and electrolyte, significantly improves the battery's low-temperature performance, cycle stability, interface stability, and thermal safety while ensuring high energy density. Firstly, the electrolyte of this invention uses ethyl propionate (EP) as the first solvent, which is a low-viscosity, low-melting-point linear ester solvent. This effectively reduces the overall viscosity of the electrolyte and optimizes the solvation structure of lithium ions at low temperatures, thereby significantly improving ionic conductivity. Therefore, even in low-temperature environments such as 0°C, the battery can still maintain good lithium-ion diffusion kinetics and rapid charge transfer capability, effectively mitigating capacity loss and power decay caused by low temperatures. Secondly, the negative electrode active material of this invention contains silicon particles, which, although possessing high specific capacity, are prone to SEI film rupture and continuous side reactions due to volume expansion. This invention uses propylene carbonate (PC) as a second solvent, which utilizes its high dielectric constant to promote the dissociation of lithium salt and preferentially reduce it on the surface of silicon-carbon anode to form a dense SEI layer rich in inorganic components such as Li2CO3; at the same time, 1,3-propanesulfonate lactone (PS) is introduced as a first additive, which preferentially reduces and undergoes ring-opening polymerization during the first charge and discharge process to generate a flexible SEI film rich in alkyl sulfonate lithium with high ionic conductivity. This composite SEI structure effectively adapts to the significant volume changes of silicon particles during cycling and significantly inhibits the continuous decomposition of the electrolyte and the irreversible consumption of active lithium, thereby greatly extending the battery cycle life. Thirdly, the electrolyte further includes vinyl sulfate (DTD) as a second additive, which has both positive and negative electrode film-forming functions: on the positive electrode surface, it oxidizes to form a dense CEI film rich in Li2SO4, effectively inhibiting electrolyte oxidation and transition metal dissolution under high voltage; on the negative electrode side, it works synergistically with PS to introduce Li2SO4 components into the SEI, improving the mechanical strength, density, and lithium-ion migration ability of the SEI, achieving simultaneous strengthening of the positive and negative electrode interfaces. Fourthly, the electrolyte also contains succinate (SN) as a third additive, whose molecule contains a strongly coordinating cyano (-CN) functional group, which can efficiently chelate harmful impurities such as residual water, HF, and transition metal ions in the electrolyte, blocking their corrosive effect and catalytic decomposition pathway on the SEI / CEI film, thereby effectively suppressing gas generation, impedance growth, and thermal runaway risks, and significantly improving the safety performance of the battery under high-temperature storage or abuse conditions; fifthly, the positive electrode active material is modified by aluminum doping and / or coating, which not only improves the crystal structure stability of the material and suppresses phase transition and oxygen evolution during charging and discharging, but also improves the electron and ion transport channels. Combined with the above-mentioned stabilized electrolyte system, the degradation of the positive electrode interface can be effectively delayed, and the capacity retention rate under high voltage and long cycle conditions can be improved.

[0034] In summary, this invention, through the synergistic design of a full battery system consisting of an aluminum-modified cathode, a silicon-based anode, and a multifunctional composite electrolyte, achieves excellent low-temperature discharge performance, ultra-long cycle life, high interface stability, and outstanding thermal safety characteristics while maintaining high energy density. It is particularly suitable for applications with stringent requirements for comprehensive electrochemical performance and safety, such as electric vehicles, power tools, and large-scale energy storage systems. In one embodiment, the mass percentage of aluminum in the positive electrode active material layer is Q, expressed as %, and the value of Q ranges from 0.4 to 2.

[0035] Specifically, the mass percentage of aluminum in the positive electrode active material layer is any one value or a range of any two values ​​from 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%; in a preferred embodiment, the mass percentage of aluminum in the positive electrode active material layer is 0.6%-1.8%.

[0036] When the mass percentage of aluminum in the positive electrode active material layer is 0.4%-2%, aluminum acts as a structural stabilizer and / or surface coating layer, effectively suppressing lattice distortion and transition metal dissolution during charging and discharging, improving cycle stability, high-temperature storage performance, and rate performance, without significantly reducing the specific capacity or electronic / ionic conductivity of the material. When the mass percentage of aluminum in the positive electrode active material layer is less than 0.4%, insufficient aluminum doping or coating cannot effectively stabilize the crystal structure of the positive electrode material, making it prone to phase transitions, oxygen release, or interfacial side reactions under high voltage or high temperature conditions, leading to shortened cycle life, accelerated capacity decay, and even increased safety risks. When the mass percentage of aluminum in the positive electrode active material layer is greater than 2%, excess aluminum may form an insulating alumina phase covering the particle surface, hindering lithium-ion diffusion paths and increasing interfacial impedance, resulting in decreased rate performance and reduced initial capacity, and potentially damaging the layered or spinel structure of the positive electrode material, thus reducing structural stability.

[0037] In one embodiment, the D50 particle size of the silicon particles in the negative electrode active material layer is W, in μm, and the value of W ranges from 2 to W to 20.

[0038] Specifically, the D50 particle size of the silicon particles in the negative electrode active material layer is any one value or a range of any two values ​​from 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm; in a preferred embodiment, the D50 particle size of the silicon particles in the negative electrode active material layer is 5μm-17μm.

[0039] When the D50 particle size of silicon particles in the negative electrode active material layer is 2μm-20μm, although the absolute volume change of silicon particles during charge and discharge is large, the particles are not prone to agglomeration, have good fluidity, and are easier to mix uniformly with conductive agents and binders; the stability of the SEI film is improved: the surface area is moderate, avoiding excessive decomposition of electrolyte and formation of thick SEI film due to excessively high specific surface area; while maintaining a high reversible capacity, the electrolyte of this invention (containing additives such as PS, VS, and SN) synergistically constructs a stable interface, effectively alleviating the cracking problem; when the D50 particle size of silicon particles in the negative electrode active material layer is less than 2μm, the specific surface area is too large, leading to an initial coulombic efficiency (IC) of less than 2μm. E) Significantly reduced, with a large amount of lithium consumed in SEI film formation; continuous reaction with electrolyte, severe gas generation, and high risk of battery swelling; silicon particles are prone to agglomeration and difficult to disperse, requiring a large amount of dispersant, affecting electrode uniformity; when the D50 particle size of silicon particles in the negative electrode active material layer is greater than 20μm, the lithium-ion diffusion path is too long, resulting in a sharp decline in rate performance and weak high-current charge and discharge capability; larger silicon particles cannot effectively release internal stress during lithium intercalation, easily causing crushing and pulverization, resulting in disconnection of active material; repeated expansion / contraction of silicon particles leads to electrode cracking, peeling off current collectors, and severe degradation of cycle life; reduced contact points between silicon particles, resulting in discontinuous electron conduction network.

[0040] In one embodiment, the total mass of the electrolyte is denoted as 100%. The mass percentage of the first solvent in the electrolyte is denoted as A, with the unit being %, and the value of A ranges from 5 to 40. The mass percentage of the second solvent in the electrolyte is denoted as B, with the unit being %, and the value of B ranges from 5 to 30. The mass percentage of the first additive in the electrolyte is denoted as X, with the unit being %, and the value of X ranges from 0.5 to 5. The mass percentage of the second additive in the electrolyte is denoted as Y, with the unit being %, and the value of Y ranges from 0.2 to 2. The mass percentage of the third additive in the electrolyte is denoted as Z, with the unit being %, and the value of Z ranges from 0.5 to 5.

[0041] Specifically, the mass percentage of the first solvent in the electrolyte is any one value or a range of any two values ​​from 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40%; in a preferred embodiment, the mass percentage of the first solvent in the electrolyte is 10%-35%.

[0042] When the first solvent accounts for 5%-40% of the electrolyte by mass, the overall viscosity of the electrolyte is effectively reduced, and the ion migration rate is improved, exhibiting excellent discharge capability, especially at low temperatures. Simultaneously, under the synergistic effect of the second solvent (propylene carbonate) and various additives (1,3-propanesulfonyl lactone, vinyl sulfate, succinic acid), lithium salt dissociation is complete, and a dense and flexible solid electrolyte interphase (SEI) film can be formed on the silicon anode surface, thus balancing kinetic performance and cycle stability. When the first solvent accounts for less than 5% of the electrolyte by mass, its effect on improving electrolyte viscosity and ionic conductivity is limited, and the battery exhibits poor performance at low temperatures or high discharge rates. Under high-rate charge and discharge conditions, polarization increases significantly, leading to a decrease in capacity utilization and making it difficult to meet the needs of fast charging or cold-region applications. When the first solvent accounts for more than 40% of the electrolyte by mass, although the low-temperature performance is further enhanced, the low dielectric constant of ethyl propionate means that excessive addition will weaken the electrolyte's ability to dissociate lithium salts (such as LiPF6), resulting in a decrease in the concentration of free lithium ions. At the same time, its reduction side reaction on the silicon anode surface is intensified, and in the absence of sufficient film protection, it is easy to form an unstable SEI layer, which leads to continuous electrolyte decomposition, gas generation, and loss of active lithium, ultimately resulting in a shortened cycle life at room temperature and deterioration of high-temperature storage performance.

[0043] Specifically, the second solvent accounts for any one or a range of any two of the following mass percentages of the electrolyte: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%; in a preferred embodiment, the second solvent accounts for 10%-25% of the electrolyte mass percentage.

[0044] When the second solvent accounts for 5%-30% of the electrolyte by mass, PC, with its high dielectric constant, effectively promotes the dissociation of lithium salts (such as LiPF6) and increases the concentration of free lithium ions. Simultaneously, with the synergistic effect of the low viscosity of the first solvent (ethyl propionate), the electrolyte exhibits both good ionic conductivity and solvation capability. Moreover, under the action of the specific additive combination of this invention (1,3-propanesulfonyl lactone, vinyl sulfate, and succinic acid), the co-intercalation and reductive decomposition of PC on the silicon anode surface are effectively suppressed, enabling the formation of a stable and dense SEI film, thereby significantly improving the battery's cycle life, high-temperature storage performance, and coulombic efficiency. When the second solvent accounts for less than 5% of the electrolyte by mass, the overall dielectric constant of the electrolyte is insufficient, and the lithium salt dissociation is incomplete, leading to a decrease in ionic conductivity and an increase in battery internal resistance. Especially under high-rate charge / discharge or high-temperature conditions, polarization intensifies, and the capacity retention rate decreases significantly. Furthermore, excessively low PC content weakens its ability to synergistically construct a high-quality SEI film with additives, making it difficult to effectively passivate the surface of highly active silicon particles, resulting in continuous side reactions and lithium loss. When the second solvent accounts for more than 30% of the electrolyte by mass, although the lithium salt dissociation capability is further enhanced, PC itself is prone to uncontrollable reduction and co-intercalation on the graphite or silicon anode surface, triggering solvent molecule decomposition, gas generation, and SEI film rupture. Even with film-forming additives, excessive PC will still competitively participate in the interface reaction, leading to excessive SEI film thickness, increased impedance, and decreased flexibility. During the repeated volume expansion / contraction of the silicon anode, such brittle interfaces are more prone to cracking, exposing fresh silicon surfaces, triggering a new round of electrolyte decomposition, ultimately manifesting as reduced initial efficiency, rapid decay of cycle capacity, and increased risk of battery swelling.

[0045] Specifically, the first additive accounts for a mass percentage of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% of the electrolyte, or a range of any two of these values; in a preferred embodiment, the first additive accounts for a mass percentage of 1.5%-4% of the electrolyte.

[0046] When the first additive accounts for 0.5%-5% of the electrolyte by mass, PS can preferentially decompose on the silicon anode surface during the first charge, generating an SEI film rich in sulfonic acid groups and inorganic lithium salts (such as Li2SO3, Li2S, etc.). This film has high ion conductivity, good flexibility, and excellent volume strain adaptability, which can effectively buffer the huge volume changes (>300%) of silicon particles during charge and discharge, and inhibit the pulverization of active materials and electrical contact failure. At the same time, this SEI film significantly reduces the continuous side reactions of the electrolyte, improving the initial coulombic efficiency and long-term cycle stability. Within this content range, PS can also produce a synergistic effect with the second additive (ethylene sulfate) and the third additive (butadiene nitrile), further strengthening interface protection and improving high-temperature storage performance. When the first additive accounts for less than 0.5% of the electrolyte by mass, its coverage on the negative electrode surface is insufficient, and it cannot form a continuous and complete SEI protective layer. The exposed area on the surface of silicon particles is large, resulting in a large amount of electrolyte decomposition and severe gas generation, and a significant increase in the first irreversible capacity loss. During cycling, the SEI film repeatedly breaks and regenerates, consuming active lithium and increasing interfacial impedance, ultimately causing rapid capacity decay and battery expansion. When the first additive accounts for more than 5% of the electrolyte by mass, excessive PS will form an excessively thick and highly impedance SEI film on the negative electrode surface, hindering lithium-ion transport and causing a decrease in rate performance. At the same time, PS itself may polymerize or undergo side reactions at high concentrations, increasing electrolyte viscosity and reducing ionic conductivity. In addition, excessive sulfur-containing decomposition products may migrate to the positive electrode, oxidize and produce acid under high voltage, accelerate the dissolution of the positive electrode transition metal and corrosion of the aluminum current collector, thereby damaging the overall stability and lifespan of the battery.

[0047] Specifically, the second additive accounts for a mass percentage of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2% of the electrolyte, or a range of any two values; in a preferred embodiment, the second additive accounts for a mass percentage of 0.5%-1.5% of the electrolyte.

[0048] When the second additive accounts for 0.2%-2% of the electrolyte by mass, VS can preferentially oxidize / reduce in the early stage of charging and discharging, forming a sulfur-containing polymer protective film on the positive electrode surface, and synergistically constructing a composite SEI film rich in Li2SO4, organic sulfuric acid esters and other components on the silicon negative electrode surface with the first additive (PS). This dual-interface protection mechanism effectively suppresses transition metal dissolution, electrolyte oxidation and decomposition, and silicon anode pulverization, significantly improving the battery's high-temperature storage performance, cycle stability, and safety. When the second additive accounts for less than 0.2% of the electrolyte by mass, its film-forming ability is insufficient, failing to form a continuous and effective protective layer on the electrode surface. This leads to intensified side reactions at the cathode-electrolyte interface under high voltage, while the silicon anode's SEI film repair capability is weak, resulting in continuous impedance growth and accelerated capacity decay during cycling. When the second additive accounts for more than 20% of the electrolyte by mass, excessive VS is prone to over-polymerization, forming a high-resistivity interface layer that hinders lithium-ion transport, leading to a decrease in rate performance. Simultaneously, its decomposition products may increase electrolyte acidity, accelerating LiPF6 hydrolysis, generating HF that corrodes the cathode material, and exacerbating the damage to the aluminum current collector passivation film, thus reducing the battery's long-term reliability.

[0049] Specifically, the third additive accounts for a mass percentage of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% of the electrolyte, or a range of any two of these values; in a preferred embodiment, the third additive accounts for a mass percentage of 1%-4.5% of the electrolyte.

[0050] When the third additive accounts for 0.5%-5% of the electrolyte by mass, SN can be effectively adsorbed on the surface of high-voltage positive electrode (such as aluminum-doped nickel-cobalt-manganese ternary materials) to form a thin and dense protective interface, inhibiting the oxidative decomposition of the electrolyte at voltages above 4.4V; at the same time, its strong polarity can partially replace solvent molecules in coordination with Li⁺, weakening the adverse reduction of PC or EP on the silicon negative electrode surface, and working synergistically with the first additive (PS) and the second additive (VS) to construct a more stable SEI / CEI dual interface. Within this content range, the battery exhibits excellent high-temperature storage performance, low gas generation rate, and good cycle retention, making it particularly suitable for high-energy-density silicon-carbon systems. When the third additive accounts for less than 0.5% of the electrolyte by mass, its coverage at the positive electrode interface is insufficient, failing to effectively block the continuous oxidation reaction of the solvent under high voltage, leading to intensified electrolyte decomposition and increased impedance. Simultaneously, its regulatory effect on the lithium-ion solvation sheath is weak, making it difficult to alleviate the co-intercalation tendency of PC on the silicon anode, resulting in low initial efficiency, continuous gas generation during cycling, and easy battery swelling. When the third additive accounts for more than 5% of the electrolyte by mass, due to the high viscosity of SN (solid at room temperature, usually used in a molten state or mixed with other solvents), excessive addition will significantly increase the overall viscosity of the electrolyte, reduce ionic conductivity, and deteriorate rate performance. In addition, high concentrations of SN may excessively complex Li⁺, thereby reducing the lithium-ion transference number and precipitating or crystallizing at low temperatures, affecting the battery's low-temperature discharge capability. During long-term cycling, its decomposition byproducts may also accumulate, increasing interfacial impedance and offsetting its initial stabilization advantage.

[0051] In one embodiment, the system further includes a diaphragm with a porosity of P, expressed as a percentage, where P ranges from 20 to 70.

[0052] Specifically, the porosity of the diaphragm is any one value or a range of any two values ​​from 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%; in a preferred embodiment, the porosity of the diaphragm is 30%-60%.

[0053] When the porosity of the separator is 20%-70%, the separator has good electrolyte absorption and retention capabilities, ensuring efficient and uniform migration of lithium ions during charging and discharging. Simultaneously, the uniform pore structure distribution maintains sufficient mechanical strength to prevent dendrite penetration and provides excellent thermal pore-closing safety. Within this porosity range, functional additives in the electrolyte (such as 1,3-propanesulfonate lactone, vinyl sulfate, etc.) can fully penetrate to the electrode / separator interface, effectively participating in the construction of the SEI / CEI membrane, thereby improving the battery's cycle stability, rate performance, and high-temperature storage reliability. When the separator porosity is less than 20%, the pores are too dense, leading to difficulty in electrolyte wetting, a significant increase in ion transport resistance, and an increase in battery internal resistance. Especially under high-rate charging and discharging or low-temperature conditions, severe polarization occurs, and capacity utilization decreases significantly. Furthermore, low porosity limits the diffusion rate of functional additives to the electrode surface, weakening their interface modification effect and making it difficult to effectively suppress the volume expansion side reaction of the silicon anode and the oxidative decomposition of the high-voltage cathode, ultimately leading to a shortened cycle life. When the porosity of the separator is greater than 70%, although the ionic conductivity is further improved, the mechanical strength of the separator decreases significantly, and the puncture resistance is weakened, making it prone to local short circuits during repeated expansion / contraction of the silicon anode or lithium dendrite growth. At the same time, excessively high porosity is often accompanied by uneven pore size distribution or an increase in macropores, reducing the thermal stability of the separator (such as a decrease in melt shrinkage temperature) and increasing the risk of thermal runaway. In addition, excessive open structure may lead to an increased probability of "electron tunneling" between the positive and negative electrodes, exacerbating self-discharge, and excessive retention of electrolyte in the separator, which in turn reduces the concentration of free lithium ions that can effectively participate in the electrode reaction.

[0054] In one embodiment, the separator is located between the positive electrode and the negative electrode.

[0055] This application does not impose any particular restrictions on the material and shape of the diaphragm, as long as it does not significantly impair the effectiveness of this application.

[0056] In some embodiments, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, including but not limited to polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.

[0057] In one embodiment, the values ​​of A, B, X, Y, Z, Q, W, and P satisfy the following condition: Equation 1: 0.23 ≤ B / A ≤ 3.38; Equation 2: 2.13 ≤ (P+A) / W ≤ 33.33; Equation 3: 0.04≤Y / (X+Z)≤0.75; Formula 4: 0.11≤(X+Y+Z) / Q≤1.90.

[0058] Specifically, the value of B / A is any one value or a range of any two values ​​from 0.23, 0.38, 0.53, 0.68, 0.83, 0.98, 1.13, 1.28, 1.43, 1.58, 1.73, 1.88, 2.03, 2.18, 2.33, 2.48, 2.63, 2.78, 2.93, 3.08, 3.23, or 3.38.

[0059] When the B / A ratio is between 0.23 and 3.38, the electrolyte exhibits both high lithium salt dissociation capability and low viscosity, and is highly compatible with the silicon anode and additive system. When the B / A ratio is less than 0.23, the PC content is relatively insufficient, making it difficult for the electrolyte to form a stable and dense initial protective layer on the silicon anode surface. This leads to continuous unstable growth of the SEI and insufficient oxidation resistance of the electrolyte, resulting in a significant deterioration in thermal shock performance and a decrease in high-temperature cycling performance. When the B / A ratio is greater than 3.38, the PC content is relatively excessive, resulting in excessively high electrolyte viscosity and a sharp increase in lithium-ion migration resistance, severely deteriorating the low-temperature cycling performance at 0°C. At the same time, excessive PC may continuously reduce and generate gas at the anode and form an excessively thick impedance layer, negatively impacting the stability of long-term cycling at 45°C and the safety during thermal shock.

[0060] Specifically, the value range of (P+A) / W is any one point value or any two point values ​​from 2.13, 5.25, 8.37, 11.49, 14.61, 17.73, 20.85, 23.97, 27.09, 30.21 or 33.33.

[0061] When the (P+A) / W ratio is between 2.13 and 33.33, the pore structure of the membrane and the content of low-viscosity solvent (ethyl propionate) in the electrolyte provide sufficient and continuous electrolyte supply, enough to cover the silicon particle surface and support the dynamic repair of the SEI film by functional additives (such as PS, VS, SN) during charge and discharge. Simultaneously, this ratio avoids excessive electrolyte retention or insufficient supply, ensuring uniform lithium-ion flux distribution and effectively mitigating localized stress concentration and electrical contact failure caused by silicon particle volume expansion. When the (P+A) / W ratio is less than 2.13, ion transport resources are severely insufficient relative to the silicon particle size. Under high current or low temperature conditions, lithium ions cannot be replenished in time, leading to a sharp increase in polarization and deterioration of 0℃ cycling performance. Simultaneously, localized electrolyte drying accelerates SEI rupture, reducing thermal shock and high-temperature cycling stability. When the (P+A) / W ratio is greater than 33.33, ion transport resources are excessive, usually indicating excessively high membrane porosity (P) or excessive solvent (A). This can lead to insufficient mechanical strength of the diaphragm (deterioration of thermal shock performance) and / or decreased thermal stability due to an excessively high EP ratio in the electrolyte. Although the low-temperature performance may be excellent, the overall safety and high-temperature lifespan are compromised.

[0062] Specifically, the value of Y / (X+Z) is any one point value or any two point values ​​from 0.04, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7 or 0.75.

[0063] When the value of Y / (X+Z) is in the range of 0.04-0.75, the second additive DTD, the first additive PS, and the third additive SN jointly participate in the construction of a dual-interface protective layer between the silicon-based negative electrode and the high-voltage positive electrode. DTD preferentially oxidizes / reduces on the electrode surface to generate an inorganic-polymer composite phase rich in Li2SO4, polysulfate, etc., which has high modulus and high ionic conductivity, and plays a skeletal reinforcement role similar to "steel bars", effectively resisting the membrane rupture caused by the volume expansion of silicon particles. PS forms a flexible polymer network mainly composed of lithium sulfonate and organic sulfides, which constitutes the "concrete" matrix of the interface membrane, providing good ductility and self-healing ability. SN, with its strong complexing ability, can capture trace water, HF and transition metal ions in the electrolyte, and plays the role of "corrosion inhibitor", inhibiting interfacial side reactions and membrane aging. When the value of Y / (X+Z) is in the range of 0.04–0.75, the ratio of "steel bars" (Y) to "concrete + corrosion inhibitor" (X+Z) reaches an ideal balance. The interface film combines high strength and high flexibility, which can withstand repeated volume changes of more than 300% on the silicon anode without breaking, and also has sufficient ion channel density and chemical inertness; at the same time, harmful impurities are effectively removed, and the SEI / CEI film is stable in the long term. Within this range, the battery exhibits excellent cycle life, low gas production rate, and high initial coulombic efficiency. When the value of Y / (X+Z) is less than 0.04, the DTD is relatively insufficient. Although the interface film has a certain foundation, it lacks the reinforcement of high-strength inorganic components. The mechanical strength of the interface film is insufficient under long-term cycling or high temperature, making it prone to damage. This leads to accelerated degradation of the cathode structure and intensified dissolution of transition metals, thereby deteriorating thermal shock and 45℃ cycling performance. When the value of Y / (X+Z) is greater than 0.75, the DTD is relatively excessive. Excessive "reinforcement" in the interface film results in an excessively thick, brittle, and high-impedance interface film. This increases the difficulty for lithium ions to pass through this high-impedance film, seriously affecting the kinetic performance at 0℃. At the same time, excessive decomposition of DTD may produce other byproducts, affecting the interface stability at high temperatures.

[0064] Specifically, the value range of (X+Y+Z) / Q is any one point value or any two point values ​​from 0.11, 0.29, 0.47, 0.65, 0.83, 1.01, 1.19, 1.37, 1.55, 1.73 or 1.9.

[0065] When the value of (X+Y+Z) / Q ranges from 0.11 to 1.9, aluminum doping effectively stabilizes the cathode phase structure and reduces the release of active oxygen and metal ions. Appropriate amounts of functional additives form a thin, dense composite CEI film on the cathode surface, rich in Li2SO4, lithium sulfonate, and nitrile polymers, further blocking electrolyte oxidation and synergistically removing residual HF and dissolved metal ions via SN. Simultaneously, on the silicon anode side, PS and DTD synergistically construct a flexible and robust SEI film, while SN suppresses the migration effect of side reactions. Under this equilibrium state, the battery exhibits high cycle capacity retention and low high-temperature storage gas generation rate under harsh conditions such as high voltage, high temperature, and low temperature. When the value of (X+Y+Z) / Q is less than 0.11, the total amount of additives is insufficient relative to a highly stable cathode (high Q) or for an unstable cathode (low Q but even less additives). The inability to form a sufficiently effective electrolyte interphase (CEI) to suppress electrolyte oxidation and metal dissolution leads to poor thermal shock safety. The migration of dissolved metals to the negative electrode also damages the electrolyte interphase (SEI), worsening high-temperature cycling. When the value of (X+Y+Z) / Q exceeds 1.9, the total amount of additives is excessive, resulting in an excessively thick and potentially uneven interfacial film regardless of the stability of the positive electrode itself. This causes significant interfacial impedance, severely degrading low-temperature performance at 0°C. Simultaneously, side reactions from excessive additives may generate gases or increase internal resistance, negatively impacting capacity retention and thermal stability during long-term cycling at 45°C.

[0066] In one embodiment, the values ​​of A, B, X, Y, Z, Q, W, and P satisfy the following condition: Equation 5: 0.25 ≤ B / A ≤ 2.00; Equation 6: 3.00 ≤ (P+A) / W ≤ 30.00; Equation 7: 0.05≤Y / (X+Z)≤0.50; Formula 8: 0.23≤(X+Y+Z) / Q≤1.18.

[0067] Specifically, when the battery satisfies Equations 5, 6, 7, and 8, the synergistic effect of each component is better, which can significantly improve the battery's thermal shock safety performance, low-temperature cycle performance, and high-temperature cycle performance.

[0068] In some embodiments, the electrolyte further includes a lithium salt, which includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium difluorodi(oxalate)borate. Using the above-mentioned lithium salt has the effects of providing a stable lithium ion source, promoting the formation of a dense SEI film, and improving the ionic conductivity and thermal stability of the electrolyte.

[0069] In some embodiments, the electrolyte further includes a base solvent, which includes one or more of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, and ethylene glycol dimethyl ether.

[0070] Specifically, the above-mentioned basic solvents are selected mainly to dissolve the first solvent, the second solvent, the first additive, the second additive, and the lithium salt.

[0071] It should be noted that this application does not impose any particular limitation on the preparation method of the electrolyte. Those skilled in the art can prepare the electrolyte using conventional technical means, such as mixing the raw materials evenly according to the specified ratio.

[0072] In one embodiment, the positive electrode active material further includes one or more of the following: transition metal lithium oxides doped with and / or coated with aluminum, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate.

[0073] Specifically, the positive electrode active material can be one or more of the above-mentioned materials.

[0074] The above-mentioned positive electrode active material has the advantages of high specific capacity, high operating voltage and structural stability, and can be matched with high-capacity silicon-based negative electrode to achieve high energy density of battery.

[0075] In one embodiment, the chemical formula of the transition metal lithium oxide is Li. 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0076] Using the aforementioned transition metal lithium oxides as positive electrode active materials has the advantages of high specific capacity, high operating voltage, and structural stability. It can be matched with high-capacity silicon-based negative electrodes to jointly achieve high energy density of the battery.

[0077] In one embodiment, the present invention provides an electrical device including the battery described above.

[0078] Specifically, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

[0079] The present invention will be further illustrated by the following examples.

[0080] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Materials not specified in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0081] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0082] In the following embodiments, the reagents, materials and instruments used, unless otherwise specified, are commercially available or can be obtained through synthesis methods known in the art.

[0083] Table 1. Design of battery components for Examples 1-72 and Comparative Examples 1-6; Table 2. Design of electrolyte components for Comparative Example 7-11; Example 1 This embodiment illustrates the lithium-ion battery disclosed in this invention, and includes the following operational steps: Preparation of positive electrode sheet Lithium cobalt oxide doped with aluminum, acetylene black (SuperP) as the positive electrode active material, and polyvinylidene fluoride (PVDF) binder are mixed evenly at a mass ratio of 97:1.5:1.5 and then uniformly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform positive electrode slurry. The mixed slurry is coated on both sides of an aluminum foil current collector, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0084] The specific values ​​of aluminum content in the added positive electrode active material are shown in Table 1 (Q value).

[0085] Preparation of negative electrode sheet The negative electrode active material artificial graphite, silicon-carbon composite, negative electrode conductive agent acetylene black (Super P), thickener CMC and negative electrode binder SBR are mixed evenly in a mass ratio of 80:10:5:2:3 and then evenly dispersed with deionized water to form a uniform negative electrode slurry. The mixed slurry is coated on both sides of a copper foil current collector, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet. The specific values ​​of the silicon particle size are shown in Table 1 (W value).

[0086] Preparation of diaphragm The membrane is a commonly available polyethylene porous membrane, and the porosity of the membrane is shown in Table 1 (P value).

[0087] Preparation of electrolyte a. Mix ethylene carbonate (EC) and diethyl carbonate (DEC) at a mass ratio of 3:7, remove water using a molecular sieve, set aside, and add 1M LiPF6 and mix thoroughly. b. Add ethyl propionate as the first solvent, propylene carbonate as the second solvent, 1,3-propanesulfonate lactone as the first additive, vinyl sulfate as the second additive, and succinic acid as the second additive to the colorless and transparent liquid obtained in step a (the amounts of the first solvent A, the second solvent B, the first additive X, the second additive Y, and the third additive Z are shown in Table 1) to obtain the electrolyte.

[0088] Manufacturing of lithium-ion batteries The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator in the middle of the positive and negative electrode sheets. After winding and welding the tabs, a bare cell is obtained. The bare cell is placed in an aluminum-plastic film for liquid injection, encapsulation, and high-temperature curing at 60°C for 8 hours to obtain a lithium-ion battery.

[0089] Examples 2-33 Examples 2-72 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 3, except that: In Examples 2-72, the mass percentages of the first solvent (A / %), the second solvent (B / %), the first additive (X / %), the second additive (Y / %), the third additive (Z / %), the aluminum content (Q / ppm) in the positive electrode active material, the D50 particle size (W / μm) of the silicon particles in the negative electrode, the porosity (P / %) of the separator, the values ​​of B / A, (P+A) / W, Y / (X+Z), and (X+Y+Z) / Q are all referenced in Table 1.

[0090] Comparative Examples 1-11 Comparative Examples 1-6 include most of the operations in Example 3, except that: The mass percentages of the first solvent (A / %), the second solvent (B / %), the first additive (X / %), the second additive (Y / %), the third additive (Z / %), the aluminum content in the positive electrode active material (Q / %), the D50 particle size (W / μm) of silicon particles in the negative electrode, the porosity (P / %) of the separator, the values ​​of B / A, (P+A) / W, Y / (X+Z), and (X+Y+Z) / Q are all referenced in Table 1.

[0091] Comparative Examples 7-11 include most of the operations in Example 3, except that: The components of the first solvent, second solvent, first additive, second additive, and third additive in Comparative Examples 7-11 are shown in Table 2.

[0092] The method for testing the aluminum content in the positive electrode active material layer is as follows: After the battery is manufactured and discharged, it is disassembled. 5mg of the positive electrode active material layer is added to 3mL of concentrated sulfuric acid and 3mL of concentrated nitric acid in sequence, heated to 180℃ until the solution is clear and transparent, cooled, and then water is added to make up to 50mL. The sample is sent for testing, and the aluminum content is tested using an ICP (Inductively Coupled Plasma Emission Spectrometer).

[0093] Performance testing The following performance tests were performed on Examples 1-72 and Comparative Examples 1-11 prepared above: Thermal shock test: The lithium-ion batteries prepared in the above embodiments and comparative examples were charged at 25°C at a rate of 1C to the cutoff voltage and the cutoff current was 0.025C. They were then transferred to an oven and heated to 150°C at a rate of 5°C / min and kept constant for 60 minutes. The batteries were considered to have passed the test if they did not catch fire or explode. The number of cells tested was 20.

[0094] 45℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 45°C at a rate of 1C / 1C within the charge and discharge cutoff voltage range. The discharge capacity of the first cycle was recorded as C1, and the discharge capacity of the Nth cycle was recorded as C2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R2 = C2 / C1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate R2 was 70% was recorded.

[0095] 0℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to charge-discharge cycles at 0°C within the charge-discharge cutoff voltage range at a rate of 1C / 1C. The discharge capacity of the first cycle was recorded as C1, and the discharge capacity of the Nth cycle was recorded as C2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R2 = C2 / C1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate R2 was 70% was recorded.

[0096] The test results are shown in Table 2.

[0097] Table 2 Battery performance test results of Examples 1-72 and Comparative Examples 1-11 Comparing Example 3 and Comparative Example 1, it can be seen that when the electrolyte contains the first solvent, the second solvent, the first additive, the second additive, and the third additive, and aluminum is present in the positive electrode active material and silicon particles are present in the negative electrode active material, the battery exhibits outstanding low-temperature performance and balanced thermal shock and high-temperature cycle performance. When the electrolyte does not contain the first solvent, the second solvent, the first additive, the second additive, and the third additive, and aluminum is absent in the positive electrode active material and silicon particles are absent in the negative electrode active material, the battery cannot form an effective interface, side reactions are severe, and overall performance is extremely poor.

[0098] Comparing Example 3 and Comparative Example 2, it can be seen that when the first solvent is used in this invention, the battery exhibits outstanding low-temperature performance and a balanced performance in thermal shock and high-temperature cycling; when the first solvent is absent, the battery exhibits poor low-temperature performance. Comparing Example 3 and Comparative Example 3, it can be seen that when the second solvent is used in this invention, the battery exhibits outstanding low-temperature performance and a balanced performance in thermal shock and high-temperature cycling; when the second solvent is absent, the battery's high-temperature stability is compromised.

[0099] Comparing Example 3 and Comparative Example 4, it can be seen that when the first additive is used in this invention, the battery has outstanding low-temperature performance and balanced thermal shock and high-temperature cycle performance; when the first additive is not present, the battery has insufficient SEI flexibility and short cycle life.

[0100] Comparing Example 3 and Comparative Example 5, it can be seen that when the second additive is used in this invention, the battery exhibits outstanding low-temperature performance and balanced thermal shock and high-temperature cycle performance; when the second additive is absent, the battery's high-temperature cycle stability is insufficient.

[0101] Comparing Example 3 and Comparative Example 6, it can be seen that when the present invention uses the third additive, the battery exhibits outstanding low-temperature performance and balanced thermal shock and high-temperature cycle performance; when the third additive is absent, the accumulation of impurities affects long-term thermal stability and cycle performance.

[0102] Comparing Example 3 and Comparative Example 7, it can be seen that when the first solvent is polypropylene, its low-temperature performance and contribution to SEI are not as good as those of ethyl propionate, resulting in a decrease in overall performance.

[0103] Comparing Example 3 and Comparative Example 8, it can be seen that when the second solvent is ethylene carbonate, its ability to form a film on the silicon anode surface is worse than that of propylene carbonate, and its high-temperature cycling stability is insufficient.

[0104] Comparing Example 3 and Comparative Example 9, it can be seen that when the first additive is methylmethoxydiethoxysilane, it has poor adaptability to silicon volume expansion.

[0105] Comparing Example 3 and Comparative Example 10, it can be seen that when the second additive is vinylene carbonate, it mainly forms a polymeric organic SEI, lacks the Li2SO4 strengthening phase introduced by DTD, and has insufficient high-temperature cycling stability.

[0106] Comparing Example 3 and Comparative Example 11, it can be seen that when the third additive is D-isocyanate, it may not be able to effectively chelate transition metal ions, and the improvement in thermal stability is limited.

[0107] Comparing Examples 1-7, it can be seen that when the first solvent accounts for 5%-40% of the electrolyte by mass, the battery's thermal shock performance, low-temperature performance, and high-temperature performance are balanced; when the first solvent accounts for less than 5% of the electrolyte by mass, the electrolyte viscosity is extremely high, the low-temperature performance is extremely poor, there are many side reactions, and the overall performance collapses; when the first solvent accounts for more than 40% of the electrolyte by mass, the thermal stability is poor, the high-temperature cycling deteriorates, and although the low-temperature performance is excellent, the safety is unqualified.

[0108] Comparing Examples 3 and 8-14, it can be seen that when the second solvent accounts for 5%-30% of the electrolyte by mass, the battery's thermal shock performance, low-temperature performance, and high-temperature performance are balanced. When the second solvent accounts for less than 5% of the electrolyte by mass, a stable SEI cannot be formed, resulting in poor thermal shock and high-temperature cycling performance. When the second solvent accounts for more than 30% of the electrolyte by mass, the excessive viscosity leads to poor low-temperature performance of the battery and may generate gas, affecting battery safety.

[0109] Comparing Examples 3 and 15-21, it can be seen that when the first additive accounts for 0.5%-5% of the electrolyte by mass, the battery's thermal shock performance, low-temperature performance, and high-temperature performance are balanced. When the first additive accounts for less than 0.5% of the electrolyte by mass, the SEI film cannot effectively suppress the volume expansion of silicon particles, resulting in a short cycle life at high temperatures. When the first additive accounts for more than 5% of the electrolyte by mass, the SEI film is too thick, resulting in extremely high impedance, poor low-temperature performance, and deterioration of thermal shock performance due to the instability of the SEI film.

[0110] Comparing Examples 3 and 22-28, it can be seen that when the second additive accounts for 0.2%-2% of the electrolyte by mass, the battery's thermal shock performance, low-temperature performance, and high-temperature performance are balanced. When the second additive accounts for less than 0.2% of the electrolyte by mass, the DTD is severely insufficient, the interface lacks reinforcement, and the high-temperature cycling stability is poor. When the second additive accounts for more than 2% of the electrolyte by mass, the DTD is severely excessive, the interface film is too thick and brittle, the low-temperature performance is poor, and it may catalyze side reactions.

[0111] Comparing Examples 3 and 29-35, it can be seen that when the third additive accounts for 0.5%-5% of the electrolyte by mass, the battery's thermal shock performance, low-temperature performance, and high-temperature performance are balanced. When the third additive accounts for less than 0.5% of the electrolyte by mass, the electrolyte separation (SN) is severely insufficient, the electrolyte's ability to purify impurities is weak, and the battery's thermal stability and high-temperature cycle performance are affected. When the third additive accounts for more than 5% of the electrolyte by mass, the SN is severely excessive, the electrolyte viscosity is too high, the risk of side reactions is high, and all performance aspects, especially low-temperature performance, deteriorate.

[0112] Comparing Examples 3 and 36-42, it can be seen that when the mass percentage of aluminum in the positive electrode active material layer is 0.4%-2%, the battery exhibits outstanding low-temperature performance and balanced thermal shock and high-temperature cycle performance; it can significantly improve the battery's cycle stability and high and low temperature storage performance. When the mass percentage of aluminum in the positive electrode active material layer is less than 0.4%, the positive electrode is extremely unstable, the total amount of additives is relatively too high, resulting in an excessively thick CEI, high impedance, poor battery cycle performance, and safety. When the mass percentage of aluminum in the positive electrode active material layer is greater than 2%, the aluminum content of the positive electrode is too high, the additives are relatively insufficient, the positive electrode interface protection is inadequate, and the overall performance declines.

[0113] Comparing Examples 3 and 43-49, it can be seen that when the D50 particle size of silicon particles in the negative electrode active material layer is 2μm-20μm, the battery exhibits outstanding low-temperature performance and a balanced thermal shock and high-temperature cycle performance; it can significantly improve the battery's cycle stability and high and low temperature storage performance. When the D50 particle size of silicon particles in the negative electrode active material layer is less than 2μm, the silicon particle size is extremely small, the side reaction surface area is huge, the active lithium is consumed quickly, and the high-temperature cycle performance is extremely poor. When the D50 particle size of silicon particles in the negative electrode active material layer is greater than 20μm, the silicon particle size is extremely large, the volume expansion is severe, the SEI film is repeatedly ruptured, and the cycle performance is extremely poor.

[0114] Comparing Examples 3 and 50-56, it can be seen that when the porosity of the separator is 20%-70%, the battery exhibits outstanding low-temperature performance and a balanced thermal shock and high-temperature cycle performance; it can significantly improve the battery's cycle stability and high and low temperature storage performance. When the porosity of the separator is less than 20%, the porosity is low, ion transport is severely hindered, the battery's low-temperature performance is poor, internal heat generation is high, and thermal shock performance is affected. When the porosity of the separator is greater than 70%, the porosity is extremely high, the separator strength is poor, thermal shock safety is poor, and high-temperature side reactions increase.

[0115] Comparing Examples 1, 3, 5, 57-58, and 65-66, it can be seen that when the value of B / A is in the range of 0.23-3.38, especially when the value of B / A is in the range of 0.25-2, the battery exhibits outstanding low-temperature performance and a balanced performance in thermal shock and high-temperature cycling. When the value of B / A is less than 0.23, EP is extremely excessive, resulting in significant thermal safety issues. When the value of B / A is greater than 3.38, PC is extremely excessive, leading to severe performance degradation.

[0116] Comparing Examples 3, 43, 47, 56-60, and 67-68, it can be seen that when the value of (P+A) / W is in the range of 2.13-33.33, especially when the value of (P+A) / W is in the range of 3-30, the battery exhibits outstanding low-temperature performance and a balanced performance in thermal shock and high-temperature cycling. When the value of (P+A) / W is less than 2.13, the transmission resources are severely insufficient, and the overall performance is limited. When the value of (P+A) / W is greater than 33.33, the transmission resources are severely excessive, and the problems of the separator and solvent are superimposed, resulting in poor battery safety.

[0117] Comparing Examples 3, 22, 26, 61-62, and 69-70, it can be seen that when the value of Y / (X+Z) is in the range of 0.04-0.75, especially when the value of Y / (X+Z) is in the range of 0.05-0.5, the battery exhibits outstanding low-temperature performance and balanced thermal shock and high-temperature cycling performance; when the value of Y / (X+Z) is less than 0.04, the DTD ratio is extremely low, and interface reinforcement is almost ineffective; when the value of Y / (X+Z) is greater than 0.75, the DTD ratio is abnormally high, the interface film is unbalanced, and the performance is poor.

[0118] Comparing Examples 3, 40, 62-64, and 70-72, it can be seen that when the value of (X+Y+Z) / Q is in the range of 0.11-1.9, especially when the value of (X+Y+Z) / Q is in the range of 0.23-1.18, the battery exhibits outstanding low-temperature performance and balanced thermal shock and high-temperature cycling performance. When the value of (X+Y+Z) / Q is less than 0.11, the total amount of additives is severely insufficient, failing to protect the high-stability cathode (high Q), resulting in poor overall performance. When the value of (X+Y+Z) / Q is greater than 1.9, the total amount of additives far exceeds the cathode (low Q) requirement, forming an excessively thick high-resistivity interface film, resulting in poor overall performance.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery, characterized in that, include A positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on the positive current collector, the positive active material comprising a positive active material, the positive active material being doped with and / or coated with aluminum. A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material comprising a negative electrode active material comprising silicon particles; An electrolyte comprising a first solvent, a second solvent, a first additive, a second additive, and a third additive; the first solvent comprising ethyl propionate, the second solvent comprising propylene carbonate, the first additive comprising 1,3-propanesulfonate lactone, the second additive comprising vinyl sulfate, and the third additive comprising succinate.

2. The battery according to claim 1, characterized in that, The mass percentage Q of aluminum in the positive electrode active material layer is expressed as %, and the value of Q ranges from 0.4 to 2.

3. The battery according to claim 2, characterized in that, The D50 particle size of the silicon particles in the negative electrode active material layer is W, with the unit being μm, and the value of W is in the range of 2≤W≤20.

4. The battery according to claim 3, characterized in that, Let the total mass of the electrolyte be denoted as 100%. The mass percentage of the first solvent in the electrolyte is denoted as A, in %, and the value of A ranges from 5 to 40. The mass percentage of the second solvent in the electrolyte is denoted as B, in %, and the value of B ranges from 5 to 30. The mass percentage of the first additive in the electrolyte is denoted as X, in %, and the value of X ranges from 0.5 to 5. The mass percentage of the second additive in the electrolyte is denoted as Y, in %, and the value of Y ranges from 0.2 to 2. The mass percentage of the third additive in the electrolyte is denoted as Z, in %, and the value of Z ranges from 0.5 to 5.

5. The battery according to claim 4, characterized in that, It also includes a diaphragm, the porosity of which is P, in %, and the value of P ranges from 20 to 70.

6. The battery according to claim 5, characterized in that, The values ​​of A, B, X, Y, Z, Q, W, and P satisfy the following condition: Equation 1: 0.23 ≤ B / A ≤ 3.38; Equation 2: 2.13 ≤ (P+A) / W ≤ 33.33; Equation 3: 0.04≤Y / (X+Z)≤0.75; Formula 4: 0.11≤(X+Y+Z) / Q≤1.

90.

7. The battery according to claim 6, characterized in that, The values ​​of A, B, X, Y, Z, Q, W, and P satisfy the following condition: Equation 5: 0.25 ≤ B / A ≤ 2.00; Equation 6: 3.00 ≤ (P+A) / W ≤ 30.00; Equation 7: 0.05≤Y / (X+Z)≤0.50; Formula 8: 0.23≤(X+Y+Z) / Q≤1.

18.

8. The battery according to claim 1, characterized in that, The positive electrode active material also includes one or more of the following: transition metal lithium oxides doped with and / or coated with aluminum, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate.

9. The battery according to claim 8, characterized in that, The chemical formula of the transition metal lithium oxide is Li 1+ x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

10. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1 to 9.

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