A battery and an electric device

Abstract

The application provides a battery and a power utilization device, which comprise a negative electrode sheet, the negative electrode sheet comprises a nickel element, the mass content of the nickel element is X, and the volume median particle size of the negative electrode active material is H; an electrolyte comprises a first additive, a second additive and a third additive, the mass percentage content of the first additive is A, the mass percentage content of the second additive is B, and the mass percentage content of the third additive is C; the values of A, B, C, H and X satisfy the following conditions: 0.001 <= (A+B) / X <= 0.83; 0.2 <= (A+B+C) / H <= 3.06; 0.18 <= C / (A+B) <= 3.2; in the application, (A+B) / X ensures the balance between the total amount of the additive and the pollution degree for the nickel impurity interface; (A+B+C) / H realizes the matching between the chemical protection of the additive and the negative electrode particle size; C / (A+B) balances the proportion of the basic film forming and the interface stable protection; the interface side reaction and the SEI film instability problem caused by the migration of the nickel element dissolution are effectively inhibited, so that the battery realizes the optimal balance between the thermal shock safety, the low-temperature cycle and the high-temperature cycle performance.

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, as a representative of modern electrochemical energy storage technology, have been widely used in portable electronic devices and new energy vehicle power systems due to their excellent energy density and excellent cycle durability.

[0003] With the development of electric vehicles and portable electronic devices, higher demands are being placed on the energy density of lithium-ion batteries. Silicon, with its theoretical specific capacity of up to 4200 mAh / g, is considered an ideal choice for next-generation anode materials. However, silicon exhibits severe volume expansion (approximately 300%) during charge and discharge, leading to electrode pulverization, repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, resulting in poor cycle performance and low initial coulombic efficiency.

[0004] In existing technologies, silicon-carbon composite materials, nano-sizing, and pre-lithiation are commonly used to improve the performance of silicon anodes. Furthermore, film-forming additives are added to the electrolyte to stabilize the SEI film. Some studies have also explored coating the silicon surface with metal oxides to improve conductivity and structural stability.

[0005] However, existing technologies still have the following shortcomings: most use silicon-oxygen or silicon-carbon materials, which sacrifices some specific capacity; the coating structure is difficult to cover evenly and is prone to falling off at high temperatures; the additive combination lacks systematic optimization and fails to achieve the synergistic effect of multiple components; and there is a lack of research on the quantitative relationship between negative electrode modification and electrolyte formulation, resulting in limited performance improvement.

[0006] In pure silicon anode battery systems, the introduction of nickel accelerates battery performance degradation through multiple chemical mechanisms. Nickel ions exhibit high migration activity in the electrolyte, readily forming coordination structures with solvent molecules at low temperatures, leading to increased electrolyte viscosity and hindered interfacial charge transport. At high temperatures, nickel catalyzes the oxidative decomposition of ester electrolytes, promoting the formation of gaseous byproducts and causing abnormal thickening of the SEI film. More critically, dissolved nickel ions migrate towards the anode during charge and discharge, disrupting the material's structural stability through embedding in the silicon lattice or surface deposition. This heterogeneous deposition not only hinders the normal insertion and extraction of lithium ions but also exacerbates stress concentration during the volume expansion of silicon materials, ultimately leading to active particle breakage and interfacial contact failure. These chemical behaviors of nickel result in more severe capacity decay problems for silicon-based anodes under high and low temperature cycling conditions; therefore, overcoming these technical problems and defects is a key issue that needs to be addressed. Summary of the Invention

[0007] In view of the problem that the introduction of nickel in the silicon-based anode battery system in the prior art leads to an increase in the nickel content of the anode, and the dissolution and migration of nickel causes an imbalance in the high and low temperature performance of lithium-ion batteries, the present invention provides a battery and an electrical device.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0009] This invention provides a battery, comprising:

[0010] A 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 layer comprising a negative electrode active material comprising silicon particles and nickel element, wherein the mass content X of the nickel element in the negative electrode active material layer is in ppm and the value of X ranges from 5 to 2000; the volume median particle size of the negative electrode active material is H in μm and the value of H ranges from 2 to 20;

[0011] An electrolyte comprising a first additive, a second additive, and a third additive; the first additive comprising ethylene ethylene carbonate; the second additive comprising lithium bis(trimethylsilylamino)amine; and the third additive comprising lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile. The total mass of the electrolyte is denoted as 100%. The mass percentage of the first additive in the electrolyte is denoted as A, in %, with a value ranging from 0.5 to 7.5%. The mass percentage of the second additive in the electrolyte is denoted as B, in %, with a value ranging from 0.25 to 2.5%. The mass percentage of the third additive in the electrolyte is denoted as C, in %, with a value ranging from 1 to 5. The electrolyte retention coefficient is denoted as P, in g / Ah, with a value ranging from 0.7 to 3.

[0012] The values ​​of A, B, C, H, and X satisfy the following condition:

[0013] Equation 1: 0.001≤(A+B) / X≤0.83;

[0014] Equation 2: 0.2≤(A+B+C) / H≤3.06;

[0015] Equation 3: 0.18≤C / (A+B)≤3.2.

[0016] Optionally, the A value, the B value, and the X value satisfy the following conditions:

[0017] Equation 4: 0.002≤(A+B) / X≤0.7.

[0018] Optionally, the batteries with the A value, B value, C value, and H value satisfy the following conditions:

[0019] Equation 5: 0.27≤(A+B+C) / H≤2.75.

[0020] Optionally, the values ​​of A, B, and C satisfy the following conditions:

[0021] Equation 6: 0.24≤C / (A+B)≤1.43.

[0022] Optionally, the average particle size of the silicon particles is 50 nm to 800 nm, and the silicon particles have a porous structure or a core-shell structure.

[0023] Optionally, the nickel element exists in a doped form within the lattice or at the grain boundaries of the silicon particles.

[0024] Optionally, the nickel element is attached to the surface of the silicon particles by surface deposition, surface coating, or chemical vapor deposition.

[0025] Optionally, the mass percentage of silicon in the negative electrode active material layer is denoted as D, with the unit being %, and the value of D is in the range of 10≤D≤90.

[0026] Optionally, the electrolyte further includes a lithium salt and an organic solvent. The lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium difluorodi(oxalato)borate. The organic solvent includes one or more of ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0027] Optionally, it also includes a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on the surface of the positive current collector, the positive active material layer comprising a positive active material, the positive active material comprising one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate.

[0028] 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;

[0029] M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0030] Another aspect of the present invention provides an electrical device comprising a battery as described above.

[0031] According to the battery provided by the present invention, ethylene carbonate preferentially reduces at the negative electrode to form an elastic SEI basic framework, effectively adapting to volume changes; bis(trimethylsilyl)aminolithium, through the synergistic effect of the two functional groups of trimethylsilyl and aminolithium with ethylene carbonate, generates a nitrogen-containing composite phase with high ionic conductivity, which is embedded in the framework to improve the ion transport efficiency of the interface film, while enhancing the thermomechanical stability of the interface film through silane crosslinking; 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt, by forming a stable three-dimensional crosslinked protective layer, constructs a robust top-layer protective network on the existing SEI film, significantly enhancing the mechanical integrity and thermal stability of the interface. Among these, the flexible matrix provided by ethylene carbonate alleviates the potential brittleness issues caused by bis(trimethyl)silaneamino lithium and 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxylonite lithium salt; the optimized ion channels and cross-linking network of bis(trimethyl)silaneamino lithium partially offset the low-temperature impedance caused by ethylene carbonate and 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxylonite lithium salt; and the stable interface layer constructed by 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxylonite lithium salt effectively suppresses catalytic side reactions caused by nickel. The synergistic effect of these three components enables the SEI film to achieve gradient and functionalization in composition and structure, ultimately allowing the battery to maintain excellent cycle stability over a wide temperature range, especially under high-temperature and thermal safety conditions. Detailed Implementation

[0032] 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.

[0033] 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.

[0034] In one embodiment, the present invention provides a battery comprising:

[0035] A 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 layer comprising a negative electrode active material comprising silicon particles and nickel element, wherein the mass content X of the nickel element in the negative electrode active material layer is in ppm and the value of X ranges from 5 to 2000; the volume median particle size of the negative electrode active material is H in μm and the value of H ranges from 2 to 20;

[0036] An electrolyte comprising a first additive, a second additive, and a third additive; the first additive comprising ethylene ethylene carbonate (VC); the second additive comprising lithium bis(trimethylsilylamine)amine (LiFSI); and the third additive comprising lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile (PST). The total mass of the electrolyte is denoted as 100%. The mass percentage of the first additive in the electrolyte is denoted as A, in %, and the value of A ranges from 0.5 to 7.5%. The mass percentage of the second additive in the electrolyte is denoted as B, in %, and the value of B ranges from 0.25 to 2.5%. The mass percentage of the third additive in the electrolyte is denoted as C, in %, and the value of C ranges from 1 to 5.

[0037] The values ​​of A, B, C, H, and X satisfy the following condition:

[0038] Equation 1: 0.001≤(A+B) / X≤0.83;

[0039] Equation 2: 0.2≤(A+B+C) / H≤3.06;

[0040] Equation 3: 0.18≤C / (A+B)≤3.2.

[0041] In this invention, there are no particular limitations on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector, etc.

[0042] In some preferred embodiments, the negative current collector comprises copper foil.

[0043] 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.

[0044] 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.

[0045] Negative electrode binders include styrene-butadiene latex, etc.

[0046] Negative electrode thickeners include CMC, etc.

[0047] Negative electrode solvents include deionized water, etc.

[0048] Specifically, the nickel content in the negative electrode active material of this application can be detected by the following methods:

[0049] Take 5 mg of the negative electrode active material and add it sequentially to 3 mL of concentrated sulfuric acid and 3 mL of concentrated nitric acid. Heat to 180°C until the solution is clear and transparent. After cooling, add water to make up to 50 mL and send the sample for analysis. The nickel content is determined using an ICP (Inductively Coupled Plasma Emission Spectrometer). The nickel in the negative electrode active layer mainly originates from nickel impurities migrating and depositing onto the negative electrode active layer during the cell manufacturing process and formation stage. In the comparative examples, a corresponding mass fraction of elemental nickel can be artificially added to the negative electrode active layer slurry to achieve the nickel content range set in the experiment.

[0050] Specifically, the mass content of nickel in the negative electrode active material layer is any one value or a range of any two values ​​from 5ppm, 10ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, or 2000ppm; in a preferred embodiment, the mass content of nickel in the negative electrode active material layer is 100ppm-1500ppm.

[0051] When the nickel content in the negative electrode active material layer is 5ppm-2000ppm, it is compatible with the first, second, and third additives in the electrolyte, further enhancing the synergistic effect to optimize lithium-ion battery performance. When the nickel content in the negative electrode active material layer is greater than 2000ppm, excess nickel impurities form localized catalytic centers in the pure silicon negative electrode. The delocalization effect of nickel ions' d-orbital electrons catalyzes the oxidative decomposition of the electrolyte, generating an unstable CoF2 / Li2O composite phase. The solid solution of nickel in the silicon lattice also blocks the lithium-ion diffusion channels, causing an increase in charge transfer impedance. At the same time, dissolved nickel ions migrate towards the negative electrode during charging and discharging, destroying the structural stability of the material by embedding into the silicon lattice or surface deposition. In summary, when the nickel content in the negative electrode active material is 5-2000ppm, the synergistic mechanism can better enhance the improvement effect on high-temperature cycle stability and storage performance.

[0052] Specifically, the first additive accounts for a mass percentage of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, or 7.5% of the electrolyte, or a range of any two values; in a preferred embodiment, the first additive accounts for a mass percentage of 2.5%-5% of the electrolyte.

[0053] When the first additive accounts for 0.5% to 7.5% of the electrolyte by mass, its vinyl groups undergo a polymerization reaction at the electrode interface to form an elastic SEI film rich in polycarbonate. This film can effectively adapt to the volume changes of the silicon anode, improve interface stability, and achieve optimal performance balance. When the first additive accounts for less than 0.5% of the electrolyte by mass, the polymerization reaction is insufficient, and the formed SEI film is too thin and incomplete, failing to effectively buffer volume expansion. When the first additive accounts for more than 7.5% of the electrolyte by mass, excessive polymerization products form an excessively thick insulating layer, severely hindering lithium-ion migration. At the same time, the increased interfacial impedance will significantly deteriorate low-temperature performance.

[0054] Specifically, the second additive accounts for a mass percentage of 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, or 2.5% 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 1%-2% of the electrolyte.

[0055] When the second additive accounts for 0.25%-2.5% of the electrolyte by mass, its trimethylsilyl and lithium amino groups synergistically interact with ethylene carbonate to form a cross-linked siloxane network and a high ionic conductivity interface layer at the electrode interface, significantly improving the battery's low-temperature performance and high-temperature cycle life. The interface modification and ion transport enhancement properties of bis(trimethylsilyl)amine lithium synergistically contribute to both constructing a high ionic conductivity interface layer and improving interface stability. When the second additive accounts for less than 0.25% of the electrolyte by mass, the interface modification effect is insufficient, failing to form a continuous and stable high ionic conductivity interface layer, and the low nitrogen content leads to decreased interface stability. When the second additive accounts for more than 2.5% of the electrolyte by mass, excessive decomposition products are over-deposited at the interface, forming an interface film with excessively high electronic conductivity, exacerbating the continuous decomposition of the electrolyte. At the same time, incompletely decomposed bis(trimethylsilyl)amine lithium may catalyze side reactions in the electrolyte, negatively impacting thermal safety.

[0056] Specifically, the third additive accounts for a mass percentage of 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 2%-4% of the electrolyte.

[0057] When the third additive accounts for 1% to 5% of the electrolyte by mass, it forms a stable three-dimensional cross-linked protective layer at the electrode interface through its cyano and fluoroimidazole structures. This protective layer can effectively inhibit electrolyte decomposition and transition metal dissolution. When the third additive accounts for less than 1% of the electrolyte by mass, the interface stabilization effect is insufficient, the protective layer coverage is incomplete, and it cannot effectively inhibit the catalytic side reactions initiated by nickel ions. When the third additive accounts for more than 5% of the electrolyte by mass, the excessively dense protective layer leads to a significant increase in interfacial impedance, which seriously hinders ion transport. At the same time, excessive cross-linking reaction may trigger electrolyte side reactions.

[0058] Specifically, the median volumetric particle size of the negative electrode active material is any one value or a range of any two values ​​selected from 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm or 20μm; in a preferred embodiment, the median volumetric particle size of the negative electrode active material is 6-16μm.

[0059] When the median volumetric particle size of the negative electrode active material is 2-20 μm, the negative electrode active material is compatible with the three additives in the electrolyte, which can better balance the interface stability and transport performance of the battery, enhance the adaptability of the synergistic mechanism to all-weather application scenarios, and further exert the synergistic effect to optimize the performance of lithium-ion batteries. When the median volumetric particle size of the negative electrode active material is less than 2 μm, the electrode specific surface area is too large, the interface reaction is violent, the additive concentration is relatively high, and it is easy to form an excessively thick SEI film, increasing the interface impedance. When the median volumetric particle size of the negative electrode active material is greater than 20 μm, the ion transport path within the particles is too long, especially at low temperatures, ion migration is hindered, resulting in insufficient capacity utilization and decreased cycle performance.

[0060] Specifically, the value range of (A+B) / X is any one point value or any two point values ​​from 0.001, 0.005, 0.01, 0.05, 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, 0.75, 0.8, or 0.83.

[0061] When the value of (A+B) / X is in the range of 0.001-0.83, a balance between the total amount of additives and the degree of contamination at the nickel impurity interface is ensured. When the value of (A+B) / X is less than 0.001, the total amount of additives is severely insufficient relative to the nickel impurity content. On the one hand, insufficient interface passivation leads to the continuous catalytic decomposition of the electrolyte by nickel ions, generating unstable SEI components and causing a surge in interfacial impedance. On the other hand, the basic interfacial film synergistically constructed by ethylene carbonate and bis(trimethylsilylamine) lithium cannot effectively complex free nickel ions, making it difficult to inhibit the oxidative decomposition of the electrolyte catalyzed by nickel, and also unable to establish a stable ion transport channel, resulting in increased gas production during high-temperature cycling and a sharp decrease in low-temperature discharge capacity. When the value of (A+B) / X is greater than 0.83, the total amount of additives is relatively excessive. Excessive ethylene carbonate polymerization products will form an excessively thick insulating layer, severely hindering lithium-ion migration. Excessive siloxanes and nitrogen-containing compounds produced by the decomposition of bis(trimethylsilylamine) lithium will be excessively deposited at the interface. Although this improves the high-temperature stability of the interfacial film, it increases the electronic conductivity of the film layer, exacerbates the continuous decomposition of the electrolyte, and increases side reactions of excessive additives, producing gaseous byproducts, which have additional negative impacts on thermal safety.

[0062] Specifically, the value of (A+B+C) / H is any one value or any two values ​​from 0.2, 0.5, 0.8, 1.1, 1.4, 1.7, 2, 2.3, 2.6, 2.9 or 3.06.

[0063] When the value of (A+B+C) / H ranges from 0.2 to 3.06, a balance is achieved between the chemical protection of the additive and the wetting degree of the electrolyte. When the value of (A+B+C) / H is less than 0.2, the additive concentration allocated per unit volume of median particle size is insufficient. In batteries with a large median particle size of the negative electrode active material, the additive cannot fully wet and modify the entire electrode interface, resulting in a large number of unprotected active sites inside the electrode. These areas exhibit uneven SEI film growth and are highly susceptible to local decomposition induced by nickel ions, leading to uneven internal resistance distribution, rapid capacity decay, and a significant decrease in cycle stability. When the value of (A+B+C) / H is greater than 3.06, the additive concentration allocated per unit volume of median particle size is excessively high. In batteries with small particle size in the negative electrode active material volume, excessively high concentrations of additives can cause violent reduction reactions on the electrode surface, forming an excessively thick and dense initial SEI film. Although this film can effectively block side reactions, its huge ion migration impedance severely limits the rate performance of the battery. Especially under low temperature conditions, lithium ion transport is hindered, resulting in a significant reduction in charging capacity.

[0064] Specifically, the value of C / (A+B) is any one point value or any two point values ​​from 0.18, 0.5, 0.8, 1.1, 1.4, 1.7, 2, 2.3, 2.6, 2.9 or 3.2.

[0065] When the value of C / (A+B) is in the range of 0.18-3.2, the ratio of basic film formation to interfacial stability protection is balanced. When the value of C / (A+B) is less than 0.18, the relative content of the interfacial stabilizer 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt is too low. The basic SEI film formed by ethylene carbonate and bis(trimethylsilylamine) lithium lacks sufficient three-dimensional cross-linking stabilization, and its chemical and thermal stability are insufficient. It is difficult to maintain structural stability under long-term cycling and thermal shock, and the interfacial film is easily degraded by the catalytic effect of nickel ions. The effect on improving high-temperature cycling performance and thermal safety is weak, and it cannot play the expected synergistic protective role. When the value of C / (A+B) is greater than 3.20, the relative content of the interfacial stabilizer 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt is too high. Excessive 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt forms an overly dense three-dimensional network protective layer at the interface. While this improves thermal stability, it results in an excessively rigid interface layer lacking toughness. This brittle interface layer cannot adapt to the expansion and contraction of the silicon anode, and is prone to microcracks during cycling, thus losing its effective protective function. Simultaneously, the excessively dense interface layer severely blocks ion transport channels, leading to a sharp increase in interface impedance, which has a serious negative impact on both low-temperature performance and cycle life.

[0066] This invention uses silicon particles instead of composite materials to maximize the high capacity advantage of silicon, making it suitable for high energy density batteries. By doping pure silicon with nickel, the electronic conductivity of the negative electrode is improved, promoting uniform nucleation and suppressing lithium dendrite growth.

[0067] The electrolyte of this invention employs ethylene ethylene carbonate as a first additive, lithium bis(trimethylsilylamine) as a second additive, and lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile as a third additive. The first additive, ethylene ethylene carbonate, undergoes a polymerization reaction at the electrode interface through its vinyl groups to form a polycarbonate-rich solid electrolyte interphase (SEI) film. This SEI film exhibits good elasticity and can effectively buffer the volume changes of the silicon anode during cycling, thereby significantly improving high-temperature (45°C) cycling performance. However, the interfacial film formed by ethylene ethylene carbonate increases the migration resistance of lithium ions to some extent, especially at low temperatures, leading to a significant increase in interfacial impedance and a noticeable negative impact on low-temperature (0°C) cycling performance. Furthermore, the decomposition products of ethylene ethylene carbonate may exacerbate interfacial reactions under extreme thermal shock, negatively affecting the battery's safety performance.

[0068] The second additive, bis(trimethylsilyl)amine lithium, is a multifunctional additive whose molecular structure contains both trimethylsilyl and lithium amino groups. These two functional groups synergistically interact with the vinyl groups of ethylene carbonate. The trimethylsilyl group of bis(trimethylsilyl)amine lithium can undergo a cross-linking reaction with the vinyl groups of ethylene carbonate to form a siloxane network, significantly enhancing the mechanical strength and thermal stability of the SEI film. Simultaneously, the lithium amino group of bis(trimethylsilyl)amine lithium decomposes to generate nitrogen-containing compounds (such as lithium amino derivatives). These compounds have high ionic conductivity and can effectively embed into the SEI framework formed by ethylene carbonate, constructing efficient ion transport channels. This synergistic effect of functional groups gives the SEI film good toughness, thermal stability, and high ionic conductivity, thereby synergistically improving the low-temperature and high-temperature cycling performance of the battery. However, bis(trimethylsilyl)amine lithium may participate in exothermic reactions at high temperatures, thus having a certain negative impact on thermal shock safety performance.

[0069] The third additive, 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt, undergoes a cross-linking reaction at the electrode interface through its cyano and fluorinated imidazolium structures, forming a dense three-dimensional network protective layer. This protective layer effectively prevents direct contact between the electrolyte and the highly active surface, inhibiting the thermal decomposition and oxidation of the electrolyte, thus having a strong positive impact on thermal shock safety and high-temperature cycling performance. However, this dense structure also limits the migration rate of lithium ions at low temperatures, leading to a slight decrease in low-temperature performance.

[0070] For the median volumetric particle size (H) of the negative electrode active material, an increase in H means a longer transport path for ions within the particles, which leads to a deterioration in ion transport performance at low temperatures and a significant reduction in low-temperature cycling performance. However, the median volumetric particle size has a positive impact on thermal shock safety because larger particles typically have a lower specific surface area, reducing side reaction sites; its impact on high-temperature cycling performance is relatively small.

[0071] The introduction of nickel (X) into the negative electrode active material can lead to electrolyte decomposition during cycling due to its catalytic activity, inducing localized side reactions and causing SEI film instability and continuous thickening. Simultaneously, nickel impurities disrupt the uniformity of the SEI film, promoting the formation of an unstable interface layer. This interface layer lacks sufficient mechanical strength to effectively constrain silicon volume expansion, exacerbating active material breakage and negatively impacting thermal safety, low-temperature and high-temperature cycling performance.

[0072] In silicon-based anode battery systems, when the above three additives act simultaneously on the silicon-based anode, ethylene carbonate preferentially reduces at the anode to form an elastic SEI basic framework, effectively adapting to volume changes; bis(trimethylsilane)amine lithium, through its two functional groups, synergistically with ethylene carbonate to generate a nitrogen-containing composite phase with high ionic conductivity, which is embedded in the framework to improve the ion transport efficiency of the interfacial film, while enhancing the thermomechanical stability of the interfacial film through silane crosslinking; 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt, by forming a stable three-dimensional crosslinked protective layer, constructs a robust top-layer protective network on top of the existing SEI film, significantly enhancing the mechanical integrity and thermal stability of the interface. The flexible matrix provided by ethylene carbonate alleviates the potential brittleness issues associated with lithium bis(trimethylsilylamine) and lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxylonite. The optimized ion channels and cross-linking network of lithium bis(trimethylsilylamine) partially offset the low-temperature impedance caused by ethylene carbonate and lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxylonite. The stable interface layer constructed by lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxylonite effectively suppresses catalytic side reactions induced by nickel. The synergistic effect of these three components enables the SEI film to achieve gradient and functionalization in composition and structure, ultimately allowing the battery to maintain excellent cycle stability over a wide temperature range, especially under high-temperature and thermal safety conditions. In particular, this invention shows a significant improvement effect on pure silicon anodes, while the improvement effect is not as good for graphite or silicon-carbon composite anodes due to differences in material properties.

[0073] Furthermore, this application controls the mass percentage content of the first, second, and third additives, and combines this with the median particle size H of the negative electrode active material and the nickel content X in the negative electrode active material, satisfying the relationships 0.001 ≤ (A+B) / X ≤ 0.83, 0.20 ≤ (A+B+C) / H ≤ 3.06, and 0.18 ≤ C / (A+B) ≤ 3.20, and when A% is 0.5%~7.5%, B% is 0.25%~2.5%, C% is 1%~5%, H is 2-20 μm, and X is 5-2000 ppm, a better synergistic effect can be achieved. (A+B) / X ensures a balance between the total amount of additives and the degree of contamination at the nickel impurity interface; (A+B+C) / H achieves a match between the chemical protection of the additives and the size of the negative electrode particles; and C / (A+B) balances the ratio of basic film formation to interface stability protection. Through this multi-dimensional regulation, the interfacial side reactions and SEI film instability caused by nickel leaching and migration can be effectively suppressed, enabling the battery to achieve the optimal balance among multiple performance aspects such as thermal shock safety, low-temperature cycling, and high-temperature cycling.

[0074] In one embodiment, the A value, the B value, and the X value satisfy the following condition:

[0075] Equation 4: 0.002≤(A+B) / X≤0.7.

[0076] When the lithium-ion battery satisfies Formula 4, the first additive, the second additive, and the third additive work synergistically to better exert their synergistic effect and improve the battery's high-temperature cycle and thermal shock performance, as well as its low-temperature cycle performance.

[0077] In one embodiment, the batteries with values ​​A, B, C, and H satisfy the following conditions:

[0078] Equation 5: 0.27≤(A+B+C) / H≤2.75.

[0079] When the lithium-ion battery satisfies Formula 5, the first additive, the second additive, and the third additive work synergistically to better exert their synergistic effect and improve the battery's high-temperature cycle and thermal shock performance, as well as its low-temperature cycle performance.

[0080] In one embodiment, the values ​​of A, B, and C satisfy the following condition:

[0081] Equation 6: 0.24≤C / (A+B)≤1.43.

[0082] When the lithium-ion battery satisfies Formula 6, the first additive, the second additive, and the third additive work synergistically to better exert their synergistic effect and improve the battery's high-temperature cycling and thermal shock performance, as well as its low-temperature cycling performance.

[0083] In one embodiment, the average particle size of the silicon particles is 50 nm to 800 nm, and the silicon particles have a porous structure or a core-shell structure.

[0084] Specifically, the average particle size of the silicon particles is any one value or a range of any two values ​​selected from 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, or 800nm; in a preferred embodiment, the average particle size of the silicon particles is 200nm to 600nm.

[0085] When the average particle size of the silicon particles is 50 nm to 800 nm, the lithium-ion diffusion path and the buffering effect of volume expansion can be optimized, thereby improving cycle stability and rate performance. When the average particle size of the silicon particles is less than 50 nm, the surface energy of the silicon particles will be too high, making them prone to agglomeration. The excessive specific surface area will also lead to excessive SEI film formation, increasing irreversible capacity loss and interfacial impedance. When the average particle size of the silicon particles is greater than 800 nm, the lithium-ion diffusion path will be too long, and the volume expansion stress will be concentrated, which will easily cause particle breakage and active material pulverization, resulting in a significant deterioration in cycle performance.

[0086] In one embodiment, the nickel element exists in the form of a dopant within the lattice or at the grain boundaries of the silicon particles, which enhances the electronic conductivity of the silicon particles, promotes uniform lithium ion insertion / extraction, and suppresses the structural pulverization of silicon particles during cycling.

[0087] In one embodiment, the nickel element is attached to the surface of the silicon particles by surface deposition, surface coating, or chemical vapor deposition. Using the above methods to attach the nickel element to the surface of the silicon particles has the advantages of uniform doping, strong bonding, and no damage to the bulk structure of the silicon particles, which helps to form a stable conductive network, improves electronic conductivity, catalyzes the formation of SEI film, and inhibits pulverization caused by the volume expansion of silicon particles.

[0088] In one embodiment, the mass percentage of silicon in the negative electrode active material layer is denoted as D, with the unit being %, and the value of D is in the range of 10≤D≤90.

[0089] Specifically, the mass percentage of silicon in the negative electrode active material layer is any one value or a range of any two values ​​from 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%; in a preferred embodiment, the mass percentage of silicon in the negative electrode active material layer is 10≤D≤90.

[0090] When the mass percentage of silicon in the negative electrode active material layer is 10% to 90%, it exhibits high specific capacity and good cycle performance, fully leveraging the capacity advantages of silicon materials. When the mass percentage of silicon in the negative electrode active material layer is less than 10%, the capacity contribution is insufficient, failing to reflect the high capacity characteristics of silicon. When the mass percentage of silicon in the negative electrode active material layer is greater than 90%, it leads to decreased electrode structural stability, intensified volume expansion effect, relative insufficiency of binder and conductive agent, and significantly shortened cycle life.

[0091] In one embodiment, 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 difluorooxalate-borate, 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.

[0092] 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.

[0093] In one embodiment, the electrolyte further includes an organic solvent, which includes one or more of the following: ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0094] Specifically, the aforementioned organic solvents are selected primarily to dissolve the first additive, the second additive, the third additive, and the lithium salt.

[0095] In one embodiment, the device further includes a positive electrode sheet, which includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The positive active material layer includes a positive active material, which includes one or more of lithium transition metal oxides, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate.

[0096] In this application, there is no particular limitation on the type of positive electrode current collector; 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, nickel 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.

[0097] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent and a positive electrode binder.

[0098] In some embodiments, the type of positive conductive agent mentioned in this invention is not limited, and any known conductive agent can be used.

[0099] 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.

[0100] 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.

[0101] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0102] 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;

[0103] M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0104] 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.

[0105] In one embodiment, a separator is also included, the separator being located between the positive electrode and the negative electrode.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] In one embodiment, another aspect of the present invention provides an electrical device comprising a battery as described above.

[0110] 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.

[0111] The present invention will be further illustrated by the following examples.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] Table 1. Design of battery components for Examples 1-21 and Comparative Examples 1-27;

[0116]

[0117]

[0118] Example 1

[0119] This embodiment illustrates the lithium-ion battery disclosed in this invention, and includes the following operational steps:

[0120] Preparation of positive electrode

[0121] LiNi, the positive electrode active material 0.6 Mn 0.2 Co 0.2 The positive electrode conductive agent acetylene black (SuperP) and polyvinylidene fluoride (PVDF) binder are mixed evenly at a mass ratio of 97:1.5:1.5, and then evenly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform positive electrode slurry. The mixed slurry is coated on both sides of the aluminum foil current collector, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0122] Preparation of silicon-based anodes

[0123] Pure silicon particles (anode active material), acetylene black (Super P) (anode conductive agent), CMC (thickener), and SBR (anode binder) (anode binder) are mixed evenly in a mass ratio of 94:2:1.2:2.8 and then evenly dispersed with deionized water to form a uniform anode 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 anode sheet.

[0124] The specific values ​​of nickel content in the added negative electrode active material, pure silicon, are shown in Table 1.

[0125] Preparation of electrolyte

[0126] a. Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 30:40:30 to form a mixed solvent. Remove water using a molecular sieve and set aside. Add 1M LiPF6 and mix thoroughly.

[0127] b. Add additives (the types and amounts of additives are shown in Table 1) to the colorless and transparent liquid obtained in step a to obtain the electrolyte.

[0128] Manufacturing of lithium-ion batteries

[0129] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator in the middle of the positive and negative electrode. After winding and welding the tabs, a bare cell is obtained. The bare cell is placed in an aluminum-plastic film for liquid injection and encapsulation to obtain a lithium-ion battery.

[0130] Examples 2-21

[0131] Examples 2-21 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that:

[0132] In Examples 2-21, the first additive, the mass percentage of the first additive A / %, the second additive, the mass percentage of the second additive B / %, the type of the third additive, the mass percentage of the third additive C / %, the content of nickel in the negative electrode active material X / ppm, the median particle size of the negative electrode active material H / μm, the value of (A+B) / X, the value of (A+B+C) / H, and the value of C / (A+B) are all referred to Table 1.

[0133] Comparative Examples 1-22

[0134] Comparative Examples 1-22 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, with the following differences:

[0135] For Comparative Examples 1 to 22, the first additive, the mass percentage of the first additive A / %, the second additive, the mass percentage of the second additive B / %, the type of the third additive, the mass percentage of the third additive C / %, the content of nickel in the negative electrode active material X / ppm, H / μm, the value of (A+B) / X, the value of (A+B+C) / H, and the value of C / (A+B) are all referred to Table 1.

[0136] Comparative Example 23

[0137] Comparative Example 23 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 2, except that:

[0138] The negative electrode active material is a graphite + silicon composite material (silicon content is 50%).

[0139] Comparative Example 24

[0140] Comparative Example 24 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 2, except that:

[0141] The second additive is trimethylsilane (replacing bistrimethylsilylaminolithium).

[0142] Comparative Example 25

[0143] Comparative Example 25 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 2, except that:

[0144] The second additive is lithium bis(fluorosulfonyl)imide (LiFSI) (instead of lithium bis(trimethylsilyl)amine).

[0145] Comparative Example 26

[0146] Comparative Example 26 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 2, except that:

[0147] The third additive is adiponitrile (replacing lithium 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile).

[0148] Comparative Example 27

[0149] Comparative Example 27 is used to comparatively illustrate the lithium-ion battery disclosed in the present invention, including most of the operations in Example 2, and the differences are as follows:

[0150] The third additive is imidazole (replacing lithium 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile).

[0151] Performance test

[0152] The following performance tests are carried out on Examples 1-21 and Comparative Examples 1-27 prepared above: [[ID=

[19] ]

[0153] 0 °C cycle performance test

[0154] The lithium-ion batteries prepared in the above examples and comparative examples are charged and discharged cyclically at a rate of 1C / 1C within the charge-discharge cut-off voltage range at 0 °C. The discharge capacity measured in the first week is denoted as Y1, and the discharge capacity measured in the Nth cycle is denoted as Y2; the capacity of the Nth week is divided by the capacity of the first week to obtain the cycle capacity retention rate W2 = Y2 / Y1 of the Nth week, and the cycle number of the lithium-ion battery when the cycle capacity retention rate W2 is 70% is recorded.

[0155] 45 °C cycle performance test

[0156] The lithium-ion batteries prepared in the above examples and comparative examples are charged and discharged cyclically at a rate of 1C / 1C within the charge-discharge cut-off voltage range at 45 °C. The discharge capacity measured in the first week is denoted as C1, and the discharge capacity measured in the Nth cycle is denoted as C2; the capacity of the Nth week is divided by the capacity of the first week to obtain the cycle capacity retention rate R2 = C2 / C1 of the Nth week, and the cycle number of the lithium-ion battery when the cycle capacity retention rate R2 is 70% is recorded.

[0157] Thermal shock test

[0158] The lithium-ion batteries prepared in the above examples and comparative examples are charged at a rate of 0.2C to the cut-off voltage at 25 °C, and the cut-off current is 0.025C. The fully charged battery is placed in an oven, and the oven is heated to 150 °C at a rate of 5 °C / min. After heating to 150 °C, it is kept warm for 60 min. If the battery does not catch fire or explode, it passes. The total number of batteries tested is 20.

[0159] The above test results are shown in Table 2.

[0160] Table 2 Battery performance test results of Examples 1-21 and Comparative Examples 1-27

[0161]

[0162]

[0163] Comparing Example 2 with Comparative Examples 1, 3-4, and 7, it can be seen that when the electrolyte includes the first additive, the number of cells passing the thermal shock test is 12, the number of cycles at 0°C is 311, and the number of cycles at 45°C is 399. When the electrolyte does not include the first additive, the number of cells passing the thermal shock test is 7, 6, 11, and 8, respectively; the number of cycles at 0°C is 141, 158, 131, and 154, respectively; and the number of cycles at 45°C is 172, 211, 191, and 238, respectively. This indicates that the absence of the first additive, ethylene ethylene carbonate, in the electrolyte leads to a decrease in the battery's heat resistance and cycle performance.

[0164] Comparing Example 2 with Comparative Examples 1, 2, 4, and 6, it can be seen that when the electrolyte includes the second additive, the number of cells passing the thermal shock test is 12, the number of cycles at 0°C is 311, and the number of cycles at 45°C is 399. When the electrolyte does not include the second additive, the number of cells passing the thermal shock test is 7, 6, 11, and 8, respectively; the number of cycles at 0°C is 141, 134, 131, and 139, respectively; and the number of cycles at 45°C is 172, 203, 191, and 232, respectively. This indicates that the absence of the second additive, bis(trimethylsilylamine) lithium, in the electrolyte leads to a decrease in the battery's heat resistance and cycle performance.

[0165] Comparing Example 2 with Comparative Examples 1, 2-3, and 5, it can be seen that when the electrolyte includes a third additive and when the electrolyte includes a first additive, the number of cells passing the thermal shock test is 12, the number of cycles at 0°C is 311, and the number of cycles at 45°C is 399. When the electrolyte does not include the first additive, the number of cells passing the thermal shock test is 7, 6, 6, and 5, respectively; the number of cycles at 0°C is 141, 134, 158, and 152, respectively; and the number of cycles at 45°C is 172, 203, 211, and 231, respectively. This indicates that the absence of the third additive, 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt, in the electrolyte leads to a decrease in the battery's heat resistance and cycle performance.

[0166] Comparing Examples 1-3 and Comparative Examples 8-9, it can be seen that when the first additive accounts for 0.5%-7.5% of the mass percentage of the electrolyte, as the first additive increases from 0.5% to 7.5%, the number of thermal shock passes decreases from 13 to 11, and the number of cycles for 0°C capacity retention decreases from 338 cycles to 292 cycles. This indicates that excessive ethylene ethylene carbonate increases interfacial impedance and deteriorates low-temperature performance. However, the number of cycles for 45°C capacity retention increases from 339 cycles to 436 cycles. It is speculated that this is because the SEI film formed by ethylene ethylene carbonate can buffer silicon volume changes and improve high-temperature stability. However, in Comparative Example 8, when the mass percentage of the first additive was 0.3%, only 8 particles passed the thermal shock test, with 178 cycles at 0°C and 210 cycles at 45°C, showing a significant decrease in performance. The presumed reason is that the formed SEI film was too thin and incomplete, failing to effectively buffer volume expansion. In Comparative Example 9, when the mass percentage of the first additive was 10% (out of range), only 6 particles passed the thermal shock test, with 151 cycles at 0°C and 171 cycles at 45°C, showing a significant decrease in performance. The presumed reason is that the excessive ethylene ethylene carbonate formed an excessively thick SEI film, hindering ion migration and triggering side reactions.

[0167] Comparing Examples 4-6 and Comparative Examples 10-11, it can be seen that when the mass percentage of the second additive increases from 0.25% to 2.5%, the number of cycles for capacity retention at 0°C increases from 282 to 385, and the number of cycles for capacity retention at 45°C increases from 360 to 459. This indicates that adding bis(trimethylsilylamine) lithium can synergistically enhance the interfacial film ionic conductivity and thermomechanical stability through its two functional groups in conjunction with ethylene carbonate, thereby improving high and low temperature cycling performance. However, the number of thermal shock passes decreased from 13 to 11, presumably because bis(trimethylsilylamine) lithium may participate in an exothermic reaction at high temperatures. In Comparative Example 10, when the mass percentage of B was 0.1% (too low), only 8 particles passed the thermal shock test, with 168 cycles at 0℃ and 200 cycles at 45℃, indicating poor performance. This suggests that insufficient bis(trimethylsilyl)amine lithium content leads to inadequate interface protection. In Comparative Example 11, when the mass percentage of B was 5% (too high), only 6 particles passed the thermal shock test, with 234 cycles at 0℃ and 219 cycles at 45℃. Although the low-temperature performance was good, the thermal safety was poor. This is presumably because excessive bis(trimethylsilyl)amine lithium forms an unstable interface layer.

[0168] Comparing Examples 7-9 and Comparative Examples 12-13, it can be seen that when the mass percentage of the third additive increases from 1% to 5%, the number of thermal shock passes increases from 11 to 16, and the number of cycles with capacity retention at 45°C increases from 391 to 422, indicating that lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile can enhance interfacial thermal stability and high-temperature cycling performance; however, the number of cycles with capacity retention at 0°C decreases from 327 to 277, presumably because the dense three-dimensional network protective layer formed by lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile hinders low-temperature ion migration. In Comparative Example 12, when the mass percentage of C was 0.1% (too low), only 5 particles passed the thermal shock test, and the number of cycles at 0℃ was 270 (high), but the number of cycles at 45℃ was only 199. This indicates that the thermal safety and high-temperature performance are poor when the 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt is insufficient. In Comparative Example 13, when the mass percentage of C was 10% (too high), 14 particles passed the thermal shock test, but the number of cycles at 0℃ was 188 and the number of cycles at 45℃ was 232, indicating a deterioration in low-temperature performance. The reason is speculated to be that the excessive 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt forms a rigid interface layer, which is prone to cracking.

[0169] Comparing Examples 10-12 and Comparative Examples 14-15, it can be seen that when the median particle size H of the negative electrode active material increases from 2 μm to 20 μm, the cycle capacity retention at 0°C decreases from 386 cycles to 268 cycles, indicating that increasing H prolongs the ion transport path within the particles and deteriorates low-temperature performance; however, it has little impact on the cycle performance at 45°C, and the number of particles passing through thermal shock increases from 9 to 14, presumably because larger particles reduce side reaction sites. In Comparative Example 14, when H is 0.5 μm (too small), the number of particles passing through thermal shock is 5, resulting in poor cycle performance; in Comparative Example 15, when H is 40 μm (too large), the number of particles passing through thermal shock is also 5, resulting in poor cycle performance, indicating that H needs to be in the range of 2-20 μm.

[0170] Comparing Examples 13-15 and Comparative Example 16, it can be seen that when the nickel content X increases from 5 ppm to 2000 ppm, the number of thermal shock passes decreases from 14 to 9, the 0°C cycle capacity retention cycles decrease from 354 to 278, and the 45°C cycle capacity retention cycles decrease from 419 to 334. This indicates that excessive X catalyzes electrolyte decomposition and damages SEI membrane stability. In Comparative Example 16, when the X content is 5000 ppm (too high), only 3 thermal shock passes, further deteriorating the cycle performance.

[0171] Comparing Examples 16-17 and Comparative Examples 17-18, it can be seen that when the value of (A + B) / X increases from 0.001 to 0.83, the number of thermal shock passes decreases from 10 to 8, the number of cycles with capacity retention at 0°C decreases from 226 to 215, and the number of cycles with capacity retention at 45°C decreases from 437 to 232. This indicates that excessively high X will catalyze the decomposition of the electrolyte and damage the stability of the SEI membrane. In Comparative Example 17, the value of (A + B) / X is 2; the number of thermal shock passes is 8, the cycle capacity retention rate at 0℃ is 208 cycles, and the cycle capacity retention rate at 45℃ is 406 cycles. The basic interface film co-constructed by ethylene carbonate and bis(trimethylsilylamine)-lithium cannot effectively complex free nickel ions, resulting in a sharp decrease in low-temperature discharge capacity. In Comparative Example 18, the value of (A + B) / X is 0.0004; the number of thermal shock passes is only 7, the cycle capacity retention rate at 0℃ is 198 cycles, and the cycle capacity retention rate at 45℃ is 216 cycles. Excessive ethylene carbonate polymerization products will form an excessively thick insulating layer, resulting in increased electronic conductivity of the film layer and poor thermal safety and low-temperature and high-temperature performance.

[0172] Comparing Examples 18-19 and Comparative Examples 19-20, it can be seen that when the value of (A+B+C) / H is in the range of 0.2-3.06, the number of particles passing through the thermal shock is 9, the number of cycles for capacity retention at 0°C decreases from 394 cycles to 266 cycles, and the number of cycles for capacity retention at 45°C increases from 272 cycles to 277 cycles, achieving a synergistic improvement in thermal shock safety, low-temperature cycling, and high-temperature cycling. When the value of (A+B+C) / H is less than 0.2, the number of particles passing through the thermal shock is only 7, the number of cycles for capacity retention at 45°C is 253 cycles, the additive concentration distributed per unit volume median particle size is insufficient, resulting in uneven internal resistance distribution, rapid capacity decay, and a significant decrease in high-temperature cycling stability. When the value of (A+B+C) / H is less than 0.2, the number of particles passing through the thermal shock is only 7, the number of cycles for capacity retention at 45°C is 253, the additive concentration distributed per unit volume median particle size is insufficient, resulting in uneven internal resistance distribution, rapid capacity decay, and a significant decrease in high-temperature cycling stability. When the value of (+B+C) / H is greater than 3.06, only 7 particles pass the thermal shock test, and the 0℃ cycle capacity retention rate is 244 cycles. The additive concentration allocated to the median particle size per unit volume is too high, forming an excessively thick and dense initial SEI film. However, its huge ion migration resistance severely limits the rate performance of the battery, resulting in poor low-temperature performance of the film layer.

[0173] Comparing Examples 20-21 and Comparative Examples 21-22, it can be seen that when the value of C / (A+B) is in the range of 0.18-3.2, the number of thermal shock passes decreases from 16 to 9, balancing the ratio of basic film formation to interface stability protection; when the value of C / (A+B) is less than 0.18, the number of thermal shock passes is 7, the 0°C cycle capacity retention period is 288 weeks, the 45°C cycle capacity retention period is 281 weeks, and the interface stabilizer 2-(trifluoromethyl)-1H-imidazol- The relatively low content of lithium 4,5-dicarboxynitrile salt resulted in insufficient chemical and thermal stability, offering only a weak improvement in high-temperature cycling performance and thermal safety, failing to achieve the expected synergistic protective effect. When the value of C / (A+B) was greater than 3.2, the number of thermal shock passes was 15, the 0°C cycle capacity retention was 287 cycles, and the 45°C cycle capacity retention was 295 cycles, indicating an excessively high relative content of the interface stabilizer, lithium 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile salt. Excessive 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt formed an overly dense three-dimensional network protective layer at the interface. Although this improved thermal stability, the excessively dense interface layer severely blocked ion transport channels, negatively impacting both low-temperature performance and cycle life.

[0174] The overall performance of Examples 16-21 was worse than that of Examples 1-15, proving that when the ratio parameters are within a better range (satisfying 0.002≤(A+B) / X≤0.7; 0.27≤(A+B+C) / H≤2.75; 0.24≤C / (A+B)≤1.43), the synergistic effect of the battery can be better exerted.

[0175] To further clarify, when all three additives are present and satisfy the following conditions are met: 0.001 ≤ (A+B) / X ≤ 0.83, 0.20 ≤ (A+B+C) / H ≤ 3.06, and 0.18 ≤ C / (A+B) ≤ At 3.20, the battery exhibits excellent performance over a wide temperature range. Specifically, ethylene ethylene carbonate preferentially forms the elastic SEI basic framework, and bis(trimethylsilyl)amine lithium, through its two functional groups (trimethylsilyl and amine lithium), synergistically forms a cross-linked network and a high ionic conductivity interface layer with ethylene ethylene carbonate. 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt, through its two functional groups (cyano and fluorinated imidazolium structure), constructs a robust top-layer protective network. The synergy of these three components enables the SEI film to achieve gradient and functionalization in composition and structure, effectively suppressing catalytic side reactions initiated by nickel, and achieving a synergistic improvement in thermal shock safety, low-temperature cycling, and high-temperature cycling. In particular, this invention has a significant improvement effect on pure silicon anodes. For example, Comparative Example 23, which uses a graphite + silicon composite anode, has significantly lower performance than the examples.

[0176] Comparing Example 2 with Comparative Examples 23-27, Comparative Example 23 used a graphite + silicon composite anode, and its thermal shock pass count was 7, with 259 cycles at 0°C and 312 cycles at 45°C, both lower than Example 2 (pure silicon anode, 12 thermal shock passes, 311 cycles at 0°C, and 399 cycles at 45°C). This indicates that the present invention has a significant improvement effect on pure silicon anodes, but a poor improvement effect on composite anodes.

[0177] In Comparative Example 24, the second additive was trimethylsilane (with only one functional group); in Comparative Example 25, the second additive was LiFSI (with only one functional group); in Comparative Example 26, the third additive was adiponitrile (with only one functional group); and in Comparative Example 27, the third additive was imidazole (with only one functional group). The thermal shock pass numbers were 5, 6, 5, and 4, respectively; the cycle times at 0°C were 250, 253, 248, and 239, respectively; and the cycle times at 45°C were 295, 298, 276, and 291, respectively, all lower than the test structure in Example 2. This indicates that only when the second additive has two functional groups (trimethylsilane and lithium amino) can it effectively synergize with ethylene carbonate to form a cross-linked network and a high ionic conductivity interface layer, thereby comprehensively improving battery performance. Additives with a single functional group cannot achieve this synergistic effect. Similarly, the two functional groups (cyano and fluorinated imidazole structures) of the third additive 2-(trifluoromethyl)-1H-imidazolium-4,5-dicarboxynitrile lithium salt also synergize with ethylene carbonate and bis(trimethylsilyl)amine lithium to enhance interfacial stability and thermal safety.

[0178] 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 by, Comprising A negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising silicon particles and a nickel element, a mass content X of the nickel element in the negative electrode active material layer being in a range of 5-2000 ppm; a volume median particle size H of the negative electrode active material being in a range of 2-20 μm; An electrolyte comprising a first additive, a second additive and a third additive, the first additive comprising vinylene carbonate, the second additive comprising lithium bis(trimethylsilyl)amide, and the third additive comprising 2-(trifluoromethyl)-1H-imidazole-4,5-dicarbonitrile lithium salt; Taking a total mass of the electrolyte as 100%, A mass percentage of the first additive in the electrolyte is denoted as A, and A is in a range of 0.5-7.5%; a mass percentage of the second additive in the electrolyte is denoted as B, and B is in a range of 0.25-2.5%; a mass percentage of the third additive in the electrolyte is denoted as C, and C is in a range of 1-5%; The A value, the B value, the C value, the H value and the X value satisfy the following conditions: Formula 1: 0.001≤(A+B) / X≤0.83; Formula 2: 0.2≤(A+B+C) / H≤3.06; Formula 3: 0.18≤C / (A+B)≤3.

2.

2. The battery of claim 1, wherein, The A value, the B value and the X value satisfy the following condition: Formula 4: 0.002≤(A+B) / X≤0.

7.

3. The battery of claim 1, wherein, The A value, the B value, the C value and the H value satisfy the following condition: Formula 5: 0.27≤(A+B+C) / H≤2.

75.

4. The battery of claim 1, wherein, The A value, the B value and the C value satisfy the following condition: Formula 6: 0.24≤C / (A+B)≤1.

43.

5. The battery of claim 1, wherein, The silicon particles have an average particle size of 50 nm-800 nm, and have a porous structure or a core-shell structure.

6. The battery of claim 5, wherein, The nickel element exists in a doped form inside a crystal lattice or at a grain boundary of the silicon particles.

7. The battery according to claim 5 or 6, characterized in that, The nickel element is attached to a surface of the silicon particles by surface deposition, surface coating or chemical vapor deposition.

8. The battery of claim 1, wherein, A mass percentage of silicon in the negative electrode active material layer is denoted as D, and D is in a range of 10≤D≤90.

9. The battery of claim 1, wherein, The electrolyte further comprises a lithium salt and an organic solvent, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium perchlorate, lithium difluorophosphate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium tetrafluoroborate, lithium difluoro di-oxalate borate; the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, gamma-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

10. The battery of claim 1, wherein, Also included is a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, the positive electrode active material comprising one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate.

11. The battery of claim 10, wherein, The transition metal lithium oxide has a chemical formula of Li 1+ x Ni y Co z M (1-y-z) O2, wherein -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, Zr.

12. An electrical device, characterized by The battery comprises the battery as claimed in any one of claims 1-11.

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