A battery and an electrical device

Abstract

This invention provides a battery and an electrical device, comprising a positive electrode sheet including a positive active material, the positive active material being doped with and / or coated with aluminum; a negative electrode sheet including a negative active material, the negative active material including silicon particles; and an electrolyte including a first solvent, a second solvent, a first additive, and a second additive; the first solvent including ethyl 2,2-difluoroacetate, the second solvent including a chain-like fluorosulfonamide compound, the first additive including mannitol carbonate sulfate, and the second additive including fluoroethylene carbonate. This invention, through the introduction of aluminum into the positive active material, the use of silicon particles in the negative active material, and the synergistic design with the multi-component solvent and additives in the electrolyte, achieves a comprehensive improvement in the battery's cycle performance, interface stability, and safety, making it particularly suitable for high-energy-density lithium-ion battery applications.

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, fluoroethylene carbonate (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, and a second additive; the first solvent comprising ethyl 2,2-difluoroacetate, the second solvent comprising a chain-like fluorosulfonamide compound, the first additive comprising mannitol sulfate, and the second additive comprising fluoroethylene carbonate.

[0007] Optionally, the mass content Q of aluminum in the positive electrode active material layer is expressed as a percentage, 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, in μm, and the value of W ranges from 2 to 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 30; 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 1 to 20.

[0010] Optionally, the A value, the B value, the X value, the Y value, the Q value, and the W value satisfy the following conditions: Equation 1: 0.32 ≤ B / A ≤ 3.13; Equation 2: 0.02≤X / (B+Y)≤0.36; Equation 3: 0.67≤(B+X+Y) / Q≤7.67; Formula 4: 0.67≤(A+X+Y) / W≤15.33.

[0011] Optionally, the A value, the B value, the X value, the Y value, the Q value, and the W value satisfy the following conditions: Equation 5: 0.33 ≤ B / A ≤ 2; Equation 6: 0.03 ≤ X / (B+Y) ≤ 0.25; Equation 7: 1.1≤(B+X+Y) / Q≤5.5; Formula 8: 1.35≤(A+X+Y) / W≤13.5.

[0012] Optionally, the structural formula of the chain-like fluorosulfonamide compound is Rf−SO2−NR′R′′; Wherein, Rf is a straight-chain or branched perfluoroalkyl group, and its general structural formula is Cf. n F 2n+1 n is an integer and 0≤n≤8; R′ and R′′ are independently selected from one or more of hydrogen atoms, C1-C6 alkyl groups or hydroxyethyl groups; and R′ and R′′ are not both hydrogen atoms.

[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, by introducing silicon particles into the negative electrode active material, the present invention fully utilizes the high theoretical specific capacity of silicon to significantly improve the battery energy density. At the same time, through precise formulation of electrolyte components and modification design of positive and negative electrodes, the core problem of volume expansion of silicon-based negative electrodes is effectively solved: the ester groups (-COO-) of the first solvent of the electrolyte (ethyl 2,2-difluoroacetate) can polymerize to form a flexible SEI network, which can buffer the volume strain during the charging and discharging process of silicon negative electrodes. Its α-position difluoromethyl group (-CF2H) lowers the molecular LUMO energy level, so that the solvent preferentially reduces to generate a high ionic conductivity SEI film, ensuring the interface ion transport efficiency; the second additive (fluoroethylene carbonate) further forms a dense SEI bottom layer rich in LiF on the surface of the negative electrode, which works synergistically with the flexible SEI network to construct a "flexible + dense" double-layer negative electrode interface protection structure, suppressing silicon negative electrode pulverization, shedding and continuous side reactions with electrolyte. The positive electrode side is stabilized by aluminum doping and / or coating to suppress the dissolution of transition metals. Combined with the first additive (mannitol carbonate sulfate) to form a dense CEI film on the positive electrode through oxidation, in which the sulfate groups cross-link to generate Li2SO4 nanocrystals to enhance the mechanical strength of the CEI film. The polyol skeleton anchors the CEI layer through hydrogen bonds, effectively blocking the interfacial reaction between the electrolyte and the positive electrode active material, and preventing the positive electrode structure from collapsing. The synergistic effect of the above-mentioned positive and negative electrode modifications and electrolyte components significantly extends the cycle life of the battery, resolving the technical contradiction of balancing high energy density and long-term cycle stability. Moreover, the first solvent (ethyl 2,2-difluoroacetate) of the electrolyte of this invention has the characteristics of low viscosity and high dielectric constant, which can improve the bulk ionic conductivity of the electrolyte. The high ionic conductivity SEI film induced by its α-position difluoromethyl group reduces the interfacial ion transport impedance. The sulfonamide group (-SO2N-) of the second solvent (chain-like fluorosulfonamide compound) can optimize the lithium-ion solvation structure and improve the lithium-ion migration rate. Together with the first solvent, it improves the ion transport efficiency and kinetic response of the battery under low-temperature conditions. Meanwhile, the chain structure and fluorine atom substitution characteristics of the second solvent endow the electrolyte with good low-temperature fluidity and chemical stability. Combined with the optimized design of the SEI / CEI film, it effectively broadens the battery's operating temperature range and ensures charge-discharge performance and capacity retention under low-temperature conditions. In addition, this invention improves battery safety through multi-component synergistic design: the aluminum element doping / coating layer of the positive electrode inhibits the dissolution of transition metals, avoids transition metal ions catalyzing electrolyte decomposition, and improves the thermal stability of the positive electrode material; the fluorine atoms of the second solvent (chain-like fluorosulfonamide compounds) can form a stable interface layer containing LiF; the dense CEI film formed by the first additive (mannitol carbonate sulfate) works synergistically with the SEI film to reduce interfacial side reactions between the electrolyte and the electrode and reduce the heat generation rate; at the same time, the fluorinated structure of the first and second solvents endows the electrolyte with good chemical stability and inhibits high-temperature decomposition and gas generation of the electrolyte.The above design effectively improves the battery's thermal shock resistance and high-temperature cycling stability, reduces the risk of thermal runaway, and solves the technical problem of insufficient safety of high-energy-density batteries. 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, and a second additive; the first solvent comprises ethyl 2,2-difluoroacetate, the second solvent comprises a chain-like fluorosulfonamide compound, the first additive comprises mannitol carbonate sulfate, and the second additive comprises fluoroethylene carbonate.

[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 one embodiment, a separator is also included, which is located between the positive electrode and the negative electrode.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] This invention significantly improves battery energy density by introducing silicon particles into the negative electrode active material, fully utilizing silicon's high theoretical specific capacity. Simultaneously, through precise electrolyte component formulation and positive / negative electrode modification design, it effectively solves the core problem of volume expansion in silicon-based negative electrodes: the ester groups (-COO-) of the first electrolyte solvent (ethyl 2,2-difluoroacetate) can polymerize to form a flexible SEI network, which can buffer the volume strain during the charging and discharging process of the silicon negative electrode. Its α-position difluoromethyl group (-CF2H) lowers the molecular LUMO energy level, allowing the solvent to preferentially reduce and generate a high-ionic-conductivity SEI film, ensuring efficient interfacial ion transport. The second additive (ethylene fluorocarbonate) further forms a dense, LiF-rich SEI layer on the negative electrode surface, synergistically constructing a "flexible + dense" bilayer negative electrode interface protection structure with the flexible SEI network, suppressing silicon negative electrode pulverization, detachment, and continuous side reactions with the electrolyte. The positive electrode side is stabilized by aluminum doping and / or coating to suppress the dissolution of transition metals. Combined with the first additive (mannitol carbonate sulfate) to form a dense CEI film on the positive electrode through oxidation, in which the sulfate groups cross-link to generate Li2SO4 nanocrystals to enhance the mechanical strength of the CEI film. The polyol skeleton anchors the CEI layer through hydrogen bonds, effectively blocking the interfacial reaction between the electrolyte and the positive electrode active material, and preventing the positive electrode structure from collapsing. The synergistic effect of the above-mentioned positive and negative electrode modifications and electrolyte components significantly extends the cycle life of the battery, resolving the technical contradiction of balancing high energy density and long-term cycle stability. Moreover, the first solvent (ethyl 2,2-difluoroacetate) of the electrolyte of this invention has the characteristics of low viscosity and high dielectric constant, which can improve the bulk ionic conductivity of the electrolyte. The high ionic conductivity SEI film induced by its α-position difluoromethyl group reduces the interfacial ion transport impedance. The sulfonamide group (-SO2N-) of the second solvent (chain-like fluorosulfonamide compound) can optimize the lithium-ion solvation structure and improve the lithium-ion migration rate. Together with the first solvent, it improves the ion transport efficiency and kinetic response of the battery under low-temperature conditions. Meanwhile, the chain structure and fluorine atom substitution characteristics of the second solvent endow the electrolyte with good low-temperature fluidity and chemical stability. Combined with the optimized design of the SEI / CEI film, it effectively broadens the battery's operating temperature range and ensures charge-discharge performance and capacity retention under low-temperature conditions. In addition, this invention improves battery safety through multi-component synergistic design: the aluminum element doping / coating layer of the positive electrode inhibits the dissolution of transition metals, avoids transition metal ions catalyzing electrolyte decomposition, and improves the thermal stability of the positive electrode material; the fluorine atoms of the second solvent (chain-like fluorosulfonamide compounds) can form a stable interface layer containing LiF; the dense CEI film formed by the first additive (mannitol carbonate sulfate) works synergistically with the SEI film to reduce interfacial side reactions between the electrolyte and the electrode and reduce the heat generation rate; at the same time, the fluorinated structure of the first and second solvents endows the electrolyte with good chemical stability and inhibits high-temperature decomposition and gas generation of the electrolyte.The above design effectively improves the battery's thermal shock resistance and high-temperature cycling stability, reduces the risk of thermal runaway, and solves the technical problem of insufficient safety of high-energy-density batteries. In one embodiment, the mass content Q of aluminum in the positive electrode active material layer is expressed as a percentage, and the value of Q ranges from 0.4 to 2.

[0037] Specifically, the mass content 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 content of aluminum in the positive electrode active material layer is 0.6%-1.8%.

[0038] When the mass content of aluminum in the positive electrode active material layer is 0.4%-2%, aluminum can be fully incorporated into the crystal structure of the positive electrode active material, forming a continuous and dense aluminum-containing coating phase (such as Al2O3, LiAlO2, or aluminum-doped spinel phase) on the particle surface. This structure effectively suppresses oxygen evolution and transition metal ion (such as Ni) precipitation under high voltage. 4+ Co 4+ The dissolution of aluminum significantly improves the structural thermal stability and cycle durability of the cathode material. Simultaneously, appropriate aluminum doping can broaden lithium-ion diffusion channels and maintain a low interfacial impedance. When the mass content of aluminum in the cathode active material layer is less than 0.4%, the amount of aluminum doping or coating is insufficient to effectively stabilize the cathode crystal structure, leading to phase transitions and transition metal dissolution during high-voltage cycling. Furthermore, due to insufficient cathode interfacial stability, film-forming additives in the electrolyte (such as mannitol sulfate and fluoroethylene carbonate) are forced to be excessively consumed on the cathode surface to compensate for interfacial protection, resulting in a relatively excessive allocation of interfacial protection resources to the cathode side, weakening its effectiveness in the construction of the negative electrode SEI, and thus affecting the overall interfacial stability of the entire battery. When the mass content of aluminum in the cathode active material layer is greater than 2%, excessive aluminum easily forms an inactive insulating phase (such as Al2O3) on the cathode particle surface or occupies lithium layer sites, blocking lithium-ion diffusion channels, significantly increasing the electrode / electrolyte interfacial impedance, leading to decreased battery rate performance, deteriorated low-temperature output capability, and potentially reduced reversible specific capacity.

[0039] 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 20.

[0040] 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.

[0041] When the D50 particle size of silicon particles in the negative electrode active material layer is 2μm-20μm, the silicon particles maintain a high specific capacity while achieving a good balance between volume expansion and interfacial side reactions: this suppresses both initial irreversible capacity loss and ongoing side reactions; simultaneously, it effectively mitigates structural damage caused by volume changes (>300%), maintaining electrode integrity and cycle stability. However, when the D50 particle size of silicon particles in the negative electrode active material layer is less than 2μm, the specific surface area increases significantly, leading to a substantial increase in the interfacial reaction area between silicon and the electrolyte, triggering severe side reactions. Repeated rupture and regeneration of the SEI film leads to an excessively thick and unstable interface layer, significantly reducing the initial coulombic efficiency and long-cycle performance. When the D50 particle size of silicon particles in the negative electrode active material layer is greater than 20 μm, although the specific surface area decreases and side reactions are somewhat suppressed, the absolute volume change of a single particle during charging and discharging increases significantly, intensifying internal stress concentration and easily causing particle cracking and pulverization. When the SEI film ruptures, it exposes a fresh silicon surface and triggers a new round of side reactions, forming a vicious cycle that ultimately causes electrode structure collapse, contact failure, and rapid capacity decay.

[0042] 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 30. 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 1 to 20.

[0043] Specifically, the mass percentage of the first solvent in the electrolyte is any one value or a range of any two values ​​from 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 mass percentage of the first solvent in the electrolyte is 10%-25%.

[0044] When the first solvent accounts for 5%-30% of the electrolyte by mass, the α-difluoromethyl (-CF2H) in its molecule can be preferentially reduced on the negative electrode surface compared to conventional carbonate solvents, generating a composite SEI film rich in inorganic lithium salts (such as LiF) and moderately polymerized organic components. This SEI possesses high ionic conductivity, good flexibility, and thermal stability, effectively buffering the volume expansion of the silicon-based negative electrode and significantly improving the battery's kinetic performance at low temperatures. When the first solvent accounts for less than 5% of the electrolyte by mass, its concentration in the electrolyte is insufficient. The dominant process of SEI formation leads to a low content of high ionic conductivity components (such as fluorinated organic lithium salts) in the SEI, resulting in increased interfacial impedance, hindered lithium-ion migration, and significant deterioration in low-temperature discharge capacity and rate performance. When the first solvent accounts for more than 30% of the electrolyte by mass, the density of the SEI film decreases and its thermal stability weakens. Under high-temperature cycling or thermal shock conditions, it is prone to local rupture or thickening, resulting in a slight decrease in high-temperature cycling retention rate. The high viscosity hinders the transport of lithium ions in the bulk electrolyte, further aggravating the deterioration of low-temperature performance.

[0045] 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.

[0046] When the second solvent accounts for 5%-30% of the electrolyte by mass, its highly polar sulfonamide groups (-SO2N-) can effectively participate in the solvation sheath reconstruction of lithium ions, weakening the interaction between anions and Li. + The binding strength of the second solvent promotes the dissociation of lithium salts. At the same time, fluorine atoms are preferentially reduced at the electrode interface to generate a stable solid electrolyte interface (SEI) and positive electrode electrolyte interface (CEI) rich in LiF, which significantly improves the interfacial chemical stability and ion migration rate, thereby improving the cycle performance and wide temperature range adaptability of the battery. When the mass percentage of the second solvent in the electrolyte is less than 5%, its concentration in the electrolyte is insufficient, and the amount of fluorine reduction products (such as LiF) generated at the interface is insufficient, making it difficult to form a dense and stable SEI / CEI layer. The interfacial side reactions are aggravated, the impedance increases, and the cycle stability and storage performance decrease significantly. When the mass percentage of the second solvent in the electrolyte is greater than 30%, it significantly increases the overall viscosity of the electrolyte, hindering the diffusion and migration of lithium ions in the bulk electrolyte. Especially under low temperature conditions, the ionic conductivity drops sharply, leading to increased battery polarization, decreased discharge capacity, and significantly deteriorated low-temperature rate performance.

[0047] 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.

[0048] When the first additive accounts for 0.5%-5% of the electrolyte by mass, the carbonate groups, sulfate groups and polyol structures in its molecule can undergo a synergistic oxidation reaction on the surface of the high-voltage positive electrode: the carbonate groups participate in the formation of the basic CEI film, the sulfate groups crosslink to generate nanoscale Li2SO4 crystals to enhance the mechanical strength of the interface, and the polyol skeleton anchors the CEI layer through hydrogen bonding, improving its density and adhesion. The resulting CEI is thin and stable, effectively suppressing transition metal dissolution and electrolyte oxidation and decomposition, significantly improving battery safety and cycle stability under high voltage and thermal shock conditions. When the first additive accounts for less than 0.5% of the electrolyte by mass, its film formation on the positive electrode surface is insufficient, making it difficult to form a continuous and dense CEI protective layer. This leads to continuous side reactions at the positive electrode / electrolyte interface and intensified dissolution of transition metal ions. Under high temperature or thermal shock conditions, the positive electrode structure is prone to instability, and the battery's thermal safety is significantly reduced. When the first additive accounts for more than 5% of the electrolyte by mass, excessive additives polymerize excessively on the positive electrode surface, forming an excessively thick and highly resistive CEI layer. This significantly increases the energy barrier for lithium ions to cross the interface, resulting in a substantial increase in interface impedance, accelerated capacity decay, decreased rate performance, and a significantly shortened cycle life.

[0049] Specifically, the second additive accounts for a mass percentage of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% of the electrolyte, or a range of any two of these values; in a preferred embodiment, the second additive accounts for a mass percentage of 5%-15% of the electrolyte.

[0050] When the second additive accounts for 1%-20% of the electrolyte by mass, its molecules preferentially undergo reduction and decomposition on the negative electrode surface during the first charge-discharge process, compared to conventional carbonate solvents, generating an inorganic-organic composite solid electrolyte interphase (SEI) film rich in lithium fluoride (LiF). This SEI possesses high interfacial energy, excellent chemical / electrochemical stability, and good lithium-ion conductivity, effectively suppressing continuous side reactions between the silicon-based negative electrode and the electrolyte, and adapting to the large volume changes of silicon particles during lithiation / delithiation processes, thereby significantly improving the battery's cycle life, coulombic efficiency, and interfacial stability. When the second additive accounts for less than 1% of the electrolyte by mass, the amount of LiF generated by its reduction is insufficient to construct a continuous and dense SEI layer, resulting in a low proportion of inorganic components and insufficient mechanical strength in the SEI; during cycling, the SEI is prone to rupture and... Repeated repairs lead to the continuous consumption of active lithium and electrolyte, a rapid increase in interfacial impedance, and a significant deterioration in battery cycle stability and storage performance. When the second additive accounts for more than 20% of the electrolyte by mass, excessive FEC is over-reduced on the negative electrode surface, forming an excessively thick and dense SEI layer. Although it has good chemical stability, it significantly increases the diffusion resistance of lithium ions across the interface, resulting in a substantial increase in interfacial impedance (Rct). At the same time, the thick SEI is prone to internal stress concentration under the effect of silicon volume expansion, increasing the risk of local peeling and inducing new side reactions. All of these factors together lead to increased battery polarization, decreased reversible capacity, and deterioration in long-cycle performance.

[0051] This invention avoids performance degradation caused by excessive amounts of a single component by precisely controlling the dosage of each component in the electrolyte (first solvent A, second solvent B, first additive X, and second additive Y), as well as the aluminum content (Q) of the positive electrode and the particle size (W) of the silicon particles in the negative electrode. Specifically, it avoids the drawbacks of excessive organic components and decreased density in the SEI film caused by excessive first solvent, increased electrolyte viscosity and impeded ion transport caused by excessive second solvent, excessive CEI / SEI film thickness and increased impedance caused by excessive first / second additives, and excessive aluminum content in the positive electrode blocking lithium-ion pathways, as well as volume effects or excessive side reactions caused by unreasonable silicon particle size in the negative electrode. Through synergistic optimization of various parameters, a precise balance is achieved between battery interface impedance, ion transport efficiency, structural stability, and cycle performance, ensuring optimal overall battery performance under all operating conditions.

[0052] In one embodiment, the values ​​of A, B, X, Y, Q, and W satisfy the following condition: Equation 1: 0.32 ≤ B / A ≤ 3.13; Equation 2: 0.02≤X / (B+Y)≤0.36; Equation 3: 0.67≤(B+X+Y) / Q≤7.67; Formula 4: 0.67≤(A+X+Y) / W≤15.33.

[0053] Specifically, the value of B / A is any one point value or any two point values ​​from 0.32, 0.72, 1.12, 1.52, 1.92, 2.32, 2.72 or 3.13.

[0054] When the B / A ratio ranges from 0.32 to 3.13, the solvent system achieves synergistic optimization of multi-dimensional performance: On the one hand, the second solvent B, with its strong polar sulfonamide group (-SO2N-) and high fluorine content, effectively regulates the lithium-ion solvation sheath structure, promotes lithium salt dissociation, and preferentially reduces it at the electrode interface to form a dense protective layer rich in LiF and sulfur-containing inorganic substances, significantly improving interfacial thermal stability and antioxidant capacity; on the other hand, the first solvent A, through the low LUMO energy level characteristics of its α-difluoromethyl group (–CF2H), preferentially reduces it to form an organic-inorganic composite SEI film with high ionic conductivity and excellent ductility, effectively buffering the drastic volume changes of the silicon anode during cycling; the two complement each other and are dynamically balanced within this ratio window, enabling the electrolyte to simultaneously possess high interfacial stability, excellent ion transport kinetics, and wide temperature range adaptability; when the B / A ratio ranges from 0.32 to 3.13... When the ratio is less than 0.32, the relative content of the second solvent B is insufficient, resulting in insufficient formation of fluorinated reduction products at the interface, making it difficult to construct a complete and continuous SEI / CEI film. Under these conditions, the battery is prone to interfacial decomposition, transition metal dissolution, and local overheating during thermal shock or high-voltage cycling, significantly deteriorating its thermal stability and safety performance. When the B / A ratio is greater than 3.13, the second solvent B is relatively excessive, leading to a significant increase in electrolyte viscosity, a decrease in lithium-ion migration rate, and a reduction in bulk conductivity. Simultaneously, the excessively thick fluorinated interfacial film and high interfacial impedance exacerbate battery polarization, resulting in a significant decrease in low-temperature discharge capacity retention and severe degradation of cycle performance. During long-term cycling at high temperatures or high voltages, the excessive sulfonamide structure may undergo slow oxidation or hydrolysis side reactions, destroying the integrity of the CEI and catalyzing further decomposition of the electrolyte, leading to accelerated high-temperature cycle capacity decay and shortened cycle life.

[0055] Specifically, the value of X / (B+Y) is any one point value or any two point values ​​from 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, or 0.36.

[0056] When the value of X / (B+Y) ranges from 0.02 to 0.36, the first additive X preferentially oxidizes on the surface of the high-voltage positive electrode, forming a dense CEI film reinforced by Li2SO4 nanocrystals and anchored by a polyol framework, effectively inhibiting the oxidative decomposition of the electrolyte and the reaction of transition metal ions (such as Ni). 2+ Mn2+ The second solvent and the second additive synergistically construct a LiF-rich and flexible composite SEI film on the silicon-based negative electrode surface, adapting to large volume expansion and maintaining interface stability. This ratio window ensures that the protection capabilities of the positive and negative electrodes are matched, avoiding any electrode interface from becoming a performance bottleneck, thereby achieving synergistic stability and efficient operation of the full-cell interface system; when the value of X / (B+Y) is less than 0.02, a continuous and complete CEI protective layer cannot be formed on the positive electrode surface. Under high temperature conditions, oxidation side reactions continue to occur at the positive electrode / electrolyte interface, resulting in a large amount of dissolution of transition metal ions; these dissolved metal ions (such as Mn) 2+ Ni 2+ As the lithium ions migrate with the electrolyte to the negative electrode, they deposit in the SEI film and catalyze its decomposition, destroying the chemical stability and ion conductivity of the SEI, leading to irreversible consumption of active lithium and a rapid increase in interfacial impedance. Under these circumstances, the battery is prone to internal short circuits or severe exothermic reactions during thermal shock tests, significantly deteriorating its thermal safety. When the value of X / (B+Y) is greater than 0.36, it excessively polymerizes on the positive electrode surface, forming an excessively thick and highly cross-linked CEI layer, significantly increasing the charge transfer resistance (Rct) of lithium ions crossing the positive electrode interface, resulting in increased battery polarization voltage and decreased reversible capacity; especially under low-temperature conditions, desolvation and interfacial intercalation kinetics are further restricted, leading to a sharp deterioration in low-temperature discharge capacity and cycle retention.

[0057] Specifically, the value of (B+X+Y) / Q is any one point value or any two points value from 0.67, 1.67, 2.67, 3.67, 4.67, 5.67, 6.67 or 7.67.

[0058] When the value of (B+X+Y) / Q ranges from 0.67 to 7.67, the total interfacial film-forming resources (B+X+Y) in the electrolyte are precisely matched with the intrinsic structural stability of the cathode material (characterized by the amount of aluminum doping / coating, Q): aluminum (Q) effectively suppresses phase transition and oxygen loss of the cathode under high voltage through lattice doping or surface coating, reducing the dependence on interfacial protection; at the same time, appropriate amounts of B, X, and Y synergistically construct stable, thin, and dense CEI / SEI films on both the positive and negative electrodes, compensating for residual interfacial side reactions and forming a dual protection mechanism of "bulk stability + interfacial protection". Within this window, the battery exhibits excellent high-voltage cycle stability, thermal safety, and wide temperature range adaptability; when the value of (B+X+Y) / Q is less than 0.67, the Q value is high while the interfacial film-forming components are too few, failing to effectively passivate residual active sites on the cathode surface; under high voltage or high temperature conditions, the electrolyte will still undergo significant oxidative decomposition, and the dissolution of transition metal ions (such as Ni, Co, Mn) will intensify. After the dissolved metal ions migrate to the negative electrode, they destroy the SEI structure and catalyze its continuous regeneration, consuming active lithium and weakening the secondary protection of the CEI for the positive electrode. This ultimately leads to a sharp increase in internal resistance and significant gas production during thermal shock testing, resulting in a significant decrease in thermal safety. When the value of (B+X+Y) / Q is greater than 7.67, the interface protection resources are relatively excessive. Even with a low aluminum content (Q) in the positive electrode, a large amount of B, X, and Y will still be excessively deposited on the electrode surface, forming an excessively thick and high-resistivity CEI / SEI composite film. This significantly increases the energy barrier for lithium ions to cross the interface, leading to a substantial increase in charge transfer impedance (Rct). Especially in low-temperature environments, ion diffusion kinetics are limited, battery polarization increases sharply, and discharge capacity and cycle retention deteriorate significantly. In addition, excessive additives (especially X and Y) may cause cross-reactions during long-term cycling (such as the condensation or hydrolysis of sulfate esters and fluorocarbonates), generating high-resistance polymers or acidic byproducts. This not only masks the stabilizing effect of aluminum on the cathode structure, but may also corrode the current collector or catalyze the decomposition of the electrolyte, further deteriorating the cycle performance.

[0059] Specifically, the value range of (A+X+Y) / W is any one value or any two values ​​from 0.67, 1.67, 2.67, 3.67, 4.67, 5.67, 6.67, 7.67, 8.67, 9.67, 10.67, 11.67, 12.67, 13.67, 14.67 or 15.33.

[0060] When the value of (A+X+Y) / W ranges from 0.67 to 15.33, the total amount of interfacial film formation and buffering resources (A+X+Y) in the electrolyte dynamically adapts to the physical size characteristics (W) of the silicon particles: smaller silicon particle sizes have higher specific surface areas, requiring more film-forming components to construct a complete SEI; larger silicon particle sizes have higher absolute values ​​of volume expansion, requiring more flexible components (such as A) to buffer stress; within this window, A, X, and Y work synergistically to form a composite SEI film on the silicon surface that combines high ionic conductivity, good flexibility, and self-healing ability, effectively adapting to deformation during lithiation / delithiation processes. Simultaneously suppressing side reactions significantly improves the cycle stability and safety of the battery over a wide temperature range. When the value of (A+X+Y) / W is less than 0.67, the interface protection resources are insufficient relative to the silicon particle size W, which cannot effectively buffer the silicon volume expansion. The SEI repeatedly breaks down and regenerates, continuously consuming active lithium and electrolyte, leading to deterioration in low-temperature cycling and a decrease in high-temperature cycling performance. When the value of (A+X+Y) / W is greater than 15.33, the interface protection resources are excessive, which may form an excessively thick SEI, increasing the lithium-ion transport impedance. Although thermal shock safety may be temporarily improved, low-temperature cycling performance deteriorates.

[0061] The core of this invention lies in the synergistic mechanism of its four key components (two solvents and two additives) and two key electrode parameters (aluminum content Q in the positive electrode and particle size W in the negative electrode). The first solvent, ethyl 2,2-difluoroacetate (A), utilizes its ester group (—COO—) to form a flexible polymer network, effectively buffering the volume expansion of the silicon negative electrode. Simultaneously, its α-position difluoromethyl group (—CF2H), as a strong electron-withdrawing group, significantly lowers the LUMO energy level of the ester group, allowing it to be preferentially reduced at the negative electrode, forming a high-ionic-conductivity, high-amorphous SEI film, significantly improving low-temperature interface kinetics. The second solvent, a fluorosulfonamide solvent (B), utilizes the strong polarity of its sulfonamide group (—SO2N—) to optimize the lithium-ion solvation structure and improve the bulk conductivity of the electrolyte. Its fluorine atoms (—F) provide excellent hydrophobicity and antioxidant properties, enabling it to participate in the formation of a stable interface layer containing lithium fluoride (LiF) or sulfonamide derivatives at the positive and negative electrode interfaces, enhancing overall thermal stability. The first additive, mannitol carbonate sulfate (X), utilizes its multifunctional molecular structure (containing cyclic carbonates, sulfates, and a polyol framework) to preferentially oxidize on the positive electrode surface. The carbonate groups form a polycarbonate-based CEI matrix, while the sulfate groups crosslink to generate lithium sulfate (Li₂SO₄) nanocrystals, jointly constructing a dense and mechanically strong CEI film that effectively blocks the dissolution of transition metal ions. Its polyol framework strongly anchors the CEI layer through hydrogen bonding, enhancing adhesion and thermal stability. The second additive, fluoroethylene carbonate (Y), is a classic film-forming additive. Its fluorocyclic carbonate structure preferentially reduces on the negative electrode, forming a LiF-rich SEI underlayer. LiF possesses high ionic conductivity, high mechanical strength, and thermal stability, effectively suppressing silicon volume expansion and lithium dendrite growth, thus improving interfacial stability.

[0062] This invention achieves comprehensive optimization of the positive electrode structure stability, negative electrode interface adaptability, and electrolyte bulk transport performance through the molecular functional design of multiple components in the electrolyte and the precise control of several key parameter relationships (including but not limited to B / A, X / (B+Y), (B+X+Y)×1 / Q, (A+X+Y) / W, etc.). This results in excellent thermal safety and wide-temperature-range cycling performance in high-energy-density silicon-based lithium-ion batteries. In one embodiment, the values ​​of A, B, X, Y, Q, and W satisfy the following condition: Equation 5: 0.33 ≤ B / A ≤ 2; Equation 6: 0.03 ≤ X / (B+Y) ≤ 0.25; Equation 7: 1.1≤(B+X+Y) / Q≤5.5; Formula 8: 1.35≤(A+X+Y) / W≤13.5.

[0063] 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.

[0064] In one embodiment, the chain-like fluorosulfonamide compound has the structural formula Rf−SO2−NR′R′′; Wherein, Rf is a straight-chain or branched perfluoroalkyl group, and its general structural formula is Cf. n F 2n+1 n is an integer and 0≤n≤8; R′ and R′′ are independently selected from one or more of hydrogen atoms, C1-C6 alkyl groups or hydroxyethyl groups; and R′ and R′′ are not both hydrogen atoms.

[0065] In some embodiments, the second solvent, a fluorosulfonamide solvent, is selected from at least one of N,N-dimethylfluorosulfonamide, N,N-dimethyltrifluoromethanesulfonamide, and N,N-diethylfluorosulfonamide.

[0066] Specifically, the chain-like fluorosulfonamide compounds selected in this invention contain strongly electron-withdrawing sulfonamide groups (-SO2-NR2) and fluorine atoms in their molecules, endowing the compounds with high dipole moments and strong polarity, which can effectively participate in the reconstruction of lithium-ion solvated sheath layers and weaken Li... + The strong binding strength with anions promotes lithium salt dissociation and increases the bulk ionic conductivity of the electrolyte; simultaneously, fluorosulfonamide compounds are preferentially oxidized at the electrode interface (especially the positive electrode surface) or reduced at the negative electrode surface, generating compounds rich in LiF and Li. x SO y F z The composite interface film of nitrogen / sulfur organic polymers possesses high chemical stability, excellent thermal resistance, and good lithium-ion conductivity. Furthermore, its chain-like alkyl substituents (such as methyl and ethyl) can regulate molecular solubility and interfacial adsorption behavior, avoiding impedance increases caused by excessive deposition. Therefore, regardless of which chain-like fluorosulfonamide compound is selected as the second solvent (B), it can reliably provide the strong polarity, excellent thermal stability, and efficient interface modification capability required by this invention. This, in conjunction with the first solvent (A), the first additive (X), and the second additive (Y), constructs a stable, low-impedance, wide-temperature-range adaptable electrode / electrolyte interface system, significantly improving the battery's cycle life, safety performance, and high / low temperature output characteristics.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] Specifically, the positive electrode active material can be one or more of the above-mentioned materials.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] In one embodiment, the present invention provides an electrical device including the battery described above.

[0077] 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.

[0078] The present invention will be further illustrated by the following examples.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] Table 1. Design of battery components for Examples 1-46 and Comparative Examples 1-5; Table 2. Design of electrolyte components for Examples 2 and 47-48 and Comparative Examples 6-9; 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.

[0083] The specific values ​​of aluminum content in the added positive electrode active material are shown in Table 1.

[0084] 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 85:5:5:2:3 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 particle size values ​​of the silicon particles are shown in Table 1.

[0085] Preparation of diaphragm It is a commonly available porous polyethylene membrane.

[0086] 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 the first solvent ethyl 2,2-difluoroacetate, the second solvent N,N-dimethylfluorosulfonamide, the first additive mannitol carbonate sulfate, and the second additive fluoroethylene carbonate to the colorless and transparent liquid obtained in step a (the types and amounts of the first solvent, the second solvent, the first additive, and the second additive are shown in Table 1 and Table 2) to obtain the electrolyte.

[0087] 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.

[0088] Examples 2-48 Examples 2-46 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: In Examples 2-46, the mass percentage of the first solvent is A / %, and the mass percentage of the second solvent is B / %. The mass percentages of the first additive (X / %), the mass percentages of the second additive (Y / %), the aluminum content (Q / %) in the positive electrode active material, and the D50 particle size (W / μm), B / A value, X / (B+Y) value, (B+X+Y) / Q value, and (A+X+Y) / W value of the silicon particles in the negative electrode are all referenced in Table 1.

[0089] Examples 47-48 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: In Examples 47-48, the types of the first solvent, the second solvent, the first additive, and the second additive are all as described in Table 2.

[0090] Comparative Examples 1-9 Comparative Examples 1-5 include most of the operations in Example 1, except that: The mass percentages of the first solvent (A / %), the second solvent (B / %), the first additive (X / %), the second additive (Y / %), the aluminum content (Q / %) in the positive electrode active material, and the D50 particle size (W / μm), B / A, X / (B+Y), (B+X+Y) / Q, and (A+X+Y) / W of the silicon particles in the negative electrode are all referenced in Table 1.

[0091] Comparative Examples 6-9 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: The types of the first solvent, the second solvent, the first additive, and the second additive in Comparative Examples 6-9 are all referenced 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 1-48 and Comparative Examples 1-9 prepared above: 60℃ Storage Performance 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, with a cutoff current of 0.025C, and left to stand for 5 minutes. The thickness H1 of the lithium-ion battery was then measured. After that, the batteries were stored at 60°C for 60 days, and the thickness H2 of the lithium-ion battery was measured after the storage period.

[0094] Thickness expansion rate = [(H2-H1) / H1]×100%.

[0095] 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.

[0096] 0℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 0°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 Y1, and the discharge capacity of the Nth cycle was recorded as Y2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate of the Nth cycle, X2 = Y2 / Y1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate X2 was 80% was recorded.

[0097] The test results are shown in Table 3.

[0098] Table 3 Battery performance test results of Examples 1-33 and Comparative Examples 1-8 Comparing Example 2 and Comparative Example 1, it can be seen that when the electrolyte contains the first solvent, the second solvent, the first additive, and the second additive, aluminum is present in the positive electrode active material, and silicon particles are present in the negative electrode active material, the thermal shock pass rate reaches 16 / 20, the 0°C cycle life reaches 378 cycles, and the 45°C cycle life reaches 356 cycles, showing good overall performance. When the electrolyte does not contain the first solvent, the second solvent, the first additive, and the second additive, the thermal shock pass rate is only 5 / 20, the 0°C cycle life drops to 215 cycles, and the 45°C cycle life is only 195 cycles, the interfacial film formation fails, and the overall performance is severely degraded.

[0099] Comparing Example 2 and Comparative Example 2, it can be seen that when the first solvent is used in this invention, the battery has good low-temperature cycling performance and thermal stability; when the first solvent is not present, the thermal shock pass count drops to 9 / 20, the 0°C cycle is only 223 cycles, the 45°C cycle is 230 cycles, the SEI flexibility is insufficient, and ion transport is hindered.

[0100] Comparing Example 2 and Comparative Example 3, it can be seen that when the second solvent is used in this invention, the high-temperature cycling performance is excellent; when the second solvent is not present, the thermal shock is only 6 / 20, and the 45°C cycle drops sharply to 220 cycles (although the 0°C cycle slightly increases to 282 cycles), indicating that the high-temperature stability of the interface is seriously insufficient.

[0101] Comparing Example 2 and Comparative Example 4, it can be seen that when the first additive is used in this invention, the positive electrode CEI effectively inhibits metal dissolution; when the first additive is not present, the thermal shock is only 4 / 20, the 45°C cycle is only 232 cycles, and the positive electrode structure degradation is accelerated at high temperature.

[0102] Comparing Example 2 and Comparative Example 5, it can be seen that when the second additive is used in this invention, the silicon anode SEI is rich in LiF and the cycle is stable; when the second additive is not present, the thermal shock 12 / 20 and the 0℃ cycle are only 217 cycles, the anode interface is unstable and the low temperature performance is significantly reduced.

[0103] Comparing Examples 2, 47-48 and Comparative Example 6, it can be seen that when the first solvent of the present invention is ethyl 2,2-difluoroacetate, the overall performance is excellent; when the first solvent is ethyl acetate, the thermal shock is only 2 / 20, the cycle is 200 times at 0°C and 185 times at 45°C, and the lack of fluorine atoms leads to poor oxidation stability and non-dense SEI.

[0104] Comparing Examples 2, 47-48, and Comparative Example 7, it can be seen that when the second solvent of the present invention is a chain-like fluorosulfonamide compound (N,N-dimethylfluorosulfonamide, N,N-dimethyltrifluoromethanesulfonamide, N,N-diethylfluorosulfonamide), the performance is balanced and the interface is stable; when the second solvent is cyclopentylfluorosulfonamide, the thermal shock is only 3 / 20, and the cycle life is less than 205 cycles. Due to the lack of fluorinated solvent, the interface is unstable and the performance is poor.

[0105] Comparing Examples 2, 47-48 and Comparative Example 8, it can be seen that when the first additive of the present invention is mannitol sulfate carbonate, the positive electrode protection is effective; when the first additive is polystyrene, the thermal shock is only 4 / 20, and after 195 cycles at 45°C, because polystyrene is an inert polymer, it cannot form an electrochemical film, resulting in insufficient positive electrode protection and poor performance.

[0106] Comparing Examples 2, 47-48 and Comparative Example 9, it can be seen that when the second additive of the present invention is fluoroethylene carbonate, the silicon anode is stable during cycling; when the second additive is vinyl sulfonic anhydride, the thermal shock is only 3 / 20, the cycle is 208 cycles at 0°C and 192 cycles at 45°C, because the LiF content in the SEI generated by vinyl sulfonic anhydride is insufficient, making it difficult to adapt to the volume expansion of silicon.

[0107] Comparing Examples 1-5, it can be seen that when the first solvent accounts for 5%-30% of the electrolyte by mass, the thermal shock rate is ≥15 / 20, and the cycle life is greater than 342 cycles, indicating good overall performance. When the first solvent accounts for less than 5% of the electrolyte by mass, the thermal shock rate is 8 / 20, and both high and low temperature cycles are <265 cycles, indicating poor low-temperature cycling due to excessive solvent viscosity. When the first solvent accounts for more than 30% of the electrolyte by mass, the thermal shock rate is 6 / 20, and the 45°C cycle life is only 221 cycles, indicating decreased thermal stability due to excessive SEI organic components.

[0108] Comparing Examples 2 and 6-10, it can be seen that when the second solvent accounts for 5%-30% of the electrolyte by mass, the thermal shock is ≥15 / 20, and the high and low temperature cycling is greater than 353 cycles, showing balanced performance. When the second solvent accounts for less than 5% of the electrolyte by mass, the thermal shock is 8 / 20, and the cycling performance at 45°C is 240 cycles, indicating poor cycling performance due to insufficient interfacial stability. When the second solvent accounts for more than 30% of the electrolyte by mass, the cycling performance at 0°C is only 233 cycles, indicating deterioration of low-temperature kinetics due to excessive viscosity.

[0109] Comparing Examples 2 and 11-15, it can be seen that when the first additive accounts for 0.5%-5% of the electrolyte by mass, the thermal shock performance is ≥15 / 20, and the high and low temperature cycling performance is greater than 349 cycles, indicating balanced performance. When the first additive accounts for less than 0.5% of the electrolyte by mass, the thermal shock performance is 5 / 20, and the cycling performance at 45℃ is 242 cycles, indicating poor thermal shock performance due to insufficient positive electrode protection. When the first additive accounts for more than 5% of the electrolyte by mass, the cycling performance at 0℃ is only 212 cycles, indicating increased impedance due to excessive CEI thickness.

[0110] Comparing Examples 2 and 16-20, it can be seen that when the second additive accounts for 1%-20% of the electrolyte by mass, the thermal shock is ≥14 / 20, and the high and low temperature cycling is greater than 352 cycles, indicating good overall performance. When the second additive accounts for less than 1% of the electrolyte by mass, the thermal shock is 10 / 20, and the 0℃ cycling is 262 cycles; due to insufficient LiF in the SEI, the interface is unstable, resulting in poor performance. When the second additive accounts for more than 20% of the electrolyte by mass, the thermal shock is 6 / 20, and the high and low temperature cycling is less than 235 cycles; due to the excessively thick SEI hindering Li...+ transmission.

[0111] Comparing Examples 1 and 21-25, it can be seen that when the mass content of aluminum in the positive electrode active material layer is 0.4%-2%, the thermal shock is ≥14 / 20, and the high and low temperature cycles are both greater than 348 cycles, indicating good overall performance. When the mass content of aluminum in the positive electrode active material layer is less than 0.4%, the thermal shock is 4 / 20, and the high and low temperature cycles are both less than 240 cycles, resulting in high impedance and poor performance due to excessive interface protection resources. When the mass content of aluminum in the positive electrode active material layer is greater than 2%, the thermal shock is 3 / 20, and the high and low temperature cycles are both less than 235 cycles, due to excessive Al blocking Li. + path.

[0112] Comparing Examples 1 and 26-30, it can be seen that when the D50 particle size of the silicon particles in the negative electrode active material layer is 2μm-20μm, the thermal shock is ≥14 / 20, and the high and low temperature cycles are both greater than 343 cycles, indicating good overall performance. When the D50 particle size of the silicon particles in the negative electrode active material layer is less than 2μm, the thermal shock is 5 / 20, and the high and low temperature cycles are both less than 250 cycles, resulting in poor performance due to increased side reactions. When the D50 particle size of the silicon particles in the negative electrode active material layer is greater than 20μm, the thermal shock is 4 / 20, and the high and low temperature cycles are both less than 245 cycles, making the SEI prone to breakage and resulting in poor cycle performance.

[0113] Comparing Examples 1 and 31-34, it can be seen that when the B / A value is in the range of 0.32-3.13, the thermal shock is ≥16 / 20, and both high and low temperature cycles are greater than 325 cycles, indicating good overall performance. When the B / A value is less than 0.32, the high temperature cycle is 296 cycles, and the high temperature cycle deteriorates due to insufficient solvent polarity. When the B / A value is greater than 3.13, the low temperature cycle is 288 cycles, and the low temperature cycle deteriorates due to excessive electrolyte viscosity.

[0114] Comparing Examples 1 and 35-38, it can be seen that when the value of X / (B+Y) is in the range of 0.02-0.36, the thermal shock is ≥16 / 20, the high and low temperature cycles are both greater than 320 cycles, and the overall performance is good; when the value of X / (B+Y) is less than 0.02, the thermal shock is 10 / 20, the positive electrode protection is insufficient, and the thermal shock is poor; when the value of X / (B+Y) is greater than 0.36, the low temperature cycle is 282 cycles, the positive electrode CEI is too thick, the impedance is high, and the low temperature cycle performance is poor.

[0115] Comparing Examples 1 and 39-42, it can be seen that when the value of (B+X+Y) / Q is in the range of 0.67-7.67, the thermal shock is ≥16 / 20, and the high and low temperature cycles are both greater than 312 cycles, indicating good overall performance. When the value of (B+X+Y) / Q is less than 0.67, the thermal shock is 10 / 20, and the high and low temperature cycles are both less than 287 cycles, indicating insufficient interface resources, unstable positive electrode, and poor performance. When the value of (B+X+Y) / Q is greater than 7.67, the low temperature cycle is 274 cycles, indicating excessive interface protection resources, high impedance, and poor low temperature cycle performance.

[0116] Comparing Examples 1 and 43-46, it can be seen that when the value of (A+X+Y) / W is in the range of 0.67-15.33, the thermal shock is ≥16 / 20, and both high and low temperature cycles are greater than 325 cycles, indicating good overall performance. When the value of (A+X+Y) / W is less than 0.67, the thermal shock is 10 / 20, the low temperature cycle is 291 cycles, the SEI resource is insufficient, the volume expansion is aggravated, and the low temperature cycle performance is poor. When the value of (A+X+Y) / W is greater than 15.33, the thermal shock is 12 / 20, the low temperature cycle is 292 cycles, the SEI resource is excessive, the impedance is high, and the low temperature cycle performance deteriorates.

[0117] All experimental data fully demonstrate that only when the electrolyte uses specific fluorinated solvents and functional additives, the content and ratio of each component fall within a precise window, and its physicochemical properties are matched with those of the aluminum-containing positive electrode / silicon negative electrode, can a synergistic improvement in high thermal safety and excellent wide-temperature-range cycling performance be achieved. Any missing component, substitution, or parameter deviation will lead to significant performance degradation.

[0118] 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, and a second additive; the first solvent comprising ethyl 2,2-difluoroacetate, the second solvent comprising a chain-like fluorosulfonamide compound, the first additive comprising mannitol sulfate, and the second additive comprising fluoroethylene carbonate.

2. The battery according to claim 1, characterized in that, The mass content Q of aluminum in the positive electrode active material layer is expressed as a percentage (%), 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 ranges from 2 to 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 30. 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 1 to 20.

5. The battery according to claim 4, characterized in that, The values ​​of A, B, X, Y, Q, and W satisfy the following condition: Equation 1: 0.32 ≤ B / A ≤ 3.13; Equation 2: 0.02≤X / (B+Y)≤0.36; Equation 3: 0.67≤(B+X+Y) / Q≤7.67; Formula 4: 0.67≤(A+X+Y) / W≤15.

33.

6. The battery according to claim 5, characterized in that, The values ​​of A, B, X, Y, Q, and W satisfy the following condition: Equation 5: 0.33 ≤ B / A ≤ 2; Equation 6: 0.03 ≤ X / (B+Y) ≤ 0.25; Equation 7: 1.1≤(B+X+Y) / Q≤5.5; Formula 8: 1.35≤(A+X+Y) / W≤13.

5.

7. The battery according to claim 1, characterized in that, The structural formula of the chain-like fluorosulfonamide compound is Rf−SO2−NR′R′′; Wherein, Rf is a straight-chain or branched perfluoroalkyl group, and its general structural formula is Cf. n F 2n+1 n is an integer and 0≤n≤8; R′ and R′′ are independently selected from one or more of hydrogen atoms, C1-C6 alkyl groups or hydroxyethyl groups; and R′ and R′′ are not both hydrogen atoms.

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 device, characterized in that, Includes the battery as described in any one of claims 1 to 9.

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