Battery and electric device

Abstract

The invention provides a battery and a power utilization device, the battery comprises a negative plate, the negative plate comprises a cobalt element, and the mass content of the cobalt element is X; the electrolyte comprises a first additive, a second additive and a third additive, and the percentage content of the first additive is marked as A; the percentage content of the second additive is marked as B; the percentage content of the third additive is recorded as C; the liquid retention coefficient of the electrolyte is recorded as P; the A value, the B value, the C value, the P value and the X value meet the condition that (A + B) / X is more than or equal to 0.002 and less than or equal to 2.05; 0.88 < = (A + B + C) / P < = 18.75; 0.04 < = C / (A + B) < = 0.57; in the application, (A + B) / X ensures the balance between the total amount of the additive for the cobalt impurity interface and the pollution degree; the (A + B + C) / P realizes matching between additive chemical protection and electrolyte infiltration degree; c / (A + B) balances the ratio of basic film formation to interface stability protection; and the problems of interface side reaction and SEI film instability caused by dissolution and migration of cobalt element are effectively inhibited, so that the optimal balance among multiple performances such as thermal shock safety, low-temperature circulation and high-temperature circulation of the battery is realized.

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 (such as VC and PST) are added to the electrolyte to stabilize the SEI film. Some studies have also attempted to coat 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 cobalt accelerates battery performance degradation through multiple chemical mechanisms. Cobalt 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, cobalt catalyzes the oxidative decomposition of ester electrolytes, promoting the formation of gaseous byproducts and causing abnormal thickening of the SEI film. More critically, dissolved cobalt 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 cobalt 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 cobalt into the silicon-based anode battery system in the prior art leads to an increase in the cobalt content of the anode and the dissolution and migration of cobalt 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: This invention provides a battery, comprising: 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 layer comprising a negative electrode active material, the negative electrode active material comprising silicon particles and cobalt element, the mass content X of cobalt element in the negative electrode active material layer, the value of X being in the range of 5ppm-2000ppm; 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(fluorosulfonyl)imide; and the third additive comprising propanesulfonate lactone. The total mass of the electrolyte is denoted as 100%. The percentage of the first additive in the electrolyte is denoted as A, in %, with a value ranging from 1 to 15. The percentage of the second additive in the electrolyte is denoted as B, in %, with a value ranging from 1 to 10. The percentage of the third additive in the electrolyte is denoted as C, in %, with a value ranging from 0.5 to 2.5. The electrolyte retention coefficient is denoted as P, in g / Ah, with a value ranging from 0.7 to 3. The values ​​of A, B, C, P, and X satisfy the following condition: Equation 1: 0.002 ≤ (A+B) / X ≤ 2.05; Equation 2: 0.88≤(A+B+C) / P≤18.75; Equation 3: 0.04≤C / (A+B)≤0.57.

[0009] Optionally, the A value, the B value, and the X value satisfy the following conditions: Equation 4: 0.004≤(A+B) / X≤1.80.

[0010] Optionally, the batteries with the A value, B value, C value, and P value satisfy the following conditions: Equation 5: 3.33≤(A+B+C) / P≤14.33.

[0011] Optionally, the values ​​of A, B, and C satisfy the following conditions: Equation 6: 0.05≤C / (A+B)≤0.28.

[0012] 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.

[0013] Optionally, the cobalt element exists in the form of a dopant within the lattice or at the grain boundaries of the silicon particles.

[0014] Optionally, the cobalt element is introduced into the silicon particles through high-temperature solid-state reaction, chemical vapor deposition, or ion implantation.

[0015] Optionally, the percentage content 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] Another aspect of the present invention provides an electrical device comprising a battery as described above.

[0020] According to the battery provided by the present invention, when vinylene carbonate (first additive), lithium bis(fluorosulfonyl)imide (second additive), and propanesulfonate lactone (third additive) are used as electrolytes and simultaneously applied to a silicon-based negative electrode, vinylene carbonate preferentially reduces at the negative electrode to form an elastic SEI basic framework, effectively adapting to volume changes; lithium bis(fluorosulfonyl)imide enhances the ion transport efficiency of the interfacial film by generating a LiF composite phase with high ionic conductivity and embedding it into the framework; propanesulfonate lactone, by forming a stable sulfonate ester 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 three additives work synergistically to... The SEI film achieves gradient and functionalization in composition and structure, ultimately enabling the battery to maintain excellent cycle stability over a wide temperature range, especially under high-temperature and thermal safety scenarios. Furthermore, this application controls the mass percentage content of the first, second, and third additives, combined with the electrolyte retention coefficient P and the cobalt content X in the negative electrode active material. (A+B) / X ensures a balance between the total amount of additives and the degree of contamination at the cobalt impurity interface; (A+B+C) / P achieves a match between the chemical protection of the additives and the degree of electrolyte wetting; and C / (A+B) balances the ratio of basic film formation to interface stability protection. Through this multi-dimensional regulation, interfacial side reactions and SEI film instability caused by cobalt leaching and migration can be effectively suppressed, achieving an optimal balance between various performance characteristics such as thermal shock safety, low-temperature cycling, and high-temperature cycling. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] In one embodiment, the present invention provides a battery comprising: 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 layer comprising a negative electrode active material, the negative electrode active material comprising silicon particles and cobalt element, the mass content X of cobalt element in the negative electrode active material layer, the value of X being in the range of 5ppm-2000ppm; An electrolyte comprising a first additive, a second additive, and a third additive; the first additive comprising vinylene carbonate (VC), the second additive comprising lithium bis(fluorosulfonyl)imide (LiFSI), and the third additive comprising propanesulfonate lactone (PST); taking the total mass of the electrolyte as 100%, the percentage of the first additive in the electrolyte is denoted as A, in %, with A ranging from 1 to 15; the percentage of the second additive in the electrolyte is denoted as B, in %, with B ranging from 1 to 10; the percentage of the third additive in the electrolyte is denoted as C, in %, with C ranging from 0.5 to 2.5; the electrolyte retention coefficient is denoted as P, in g / Ah, with P ranging from 0.7 to 3. The values ​​of A, B, C, P, and X satisfy the following condition: Equation 1: 0.002 ≤ (A+B) / X ≤ 2.05; Equation 2: 0.88≤(A+B+C) / P≤18.75; Equation 3: 0.04≤C / (A+B)≤0.57.

[0024] 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.

[0025] In some preferred embodiments, the negative current collector comprises copper foil.

[0026] 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.

[0027] 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.

[0028] Negative electrode binders include styrene-butadiene latex, etc. Negative electrode thickeners include CMC, etc. Negative electrode solvents include deionized water, etc.

[0029] Specifically, the cobalt content in the negative electrode active material of this application can be detected by the following methods: 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. Use an ICP (Inductively Coupled Plasma Emission Spectrometer) to test the cobalt content. The main source of cobalt in the negative electrode active layer is the migration and deposition of cobalt impurities during the cell manufacturing process and formation stage. In the comparative examples, a corresponding mass fraction of elemental cobalt can be artificially added to the negative electrode active layer slurry to achieve the cobalt content range set in the experiment.

[0030] Specifically, the mass content of cobalt 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 cobalt in the negative electrode active material layer is 100ppm-1500ppm.

[0031] When the mass content of cobalt in the negative electrode active material layer is 5ppm-2000ppm, it is compatible with the first, second, and third additives in the electrolyte, further exerting a synergistic effect to optimize the performance of lithium-ion batteries. When the mass content of cobalt in the negative electrode active material layer is greater than 2000ppm, the excess cobalt impurities form local catalytic centers in the pure silicon negative electrode. The delocalization effect of the d-orbital electrons of cobalt ions will catalyze the oxidation and decomposition of the electrolyte and generate an unstable CoF2 / Li2O composite phase. The solid solution of cobalt in the silicon lattice will also block the lithium-ion diffusion channels, resulting in an increase in charge transfer impedance. At the same time, the dissolved cobalt ions will migrate to the negative electrode during charging and discharging, destroying the structural stability of the material by embedding into the silicon lattice or surface deposition.

[0032] Specifically, the percentage of the first additive in the electrolyte is any one value or a range of any two values ​​from 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%; in a preferred embodiment, the percentage of the first additive in the electrolyte is 5%-10%.

[0033] When the first additive accounts for 1%-15% of the electrolyte, 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 1% of the electrolyte, 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 15% of the electrolyte, 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.

[0034] Specifically, the percentage of the second additive in the electrolyte is any one value or a range of any two values ​​from 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%; in a preferred embodiment, the percentage of the second additive in the electrolyte is 3%-7%.

[0035] When the second additive accounts for 1%-10% of the electrolyte, it decomposes at the electrode interface through its unique anionic structure to form a stable interface layer rich in LiF. This interface layer has excellent ionic conductivity, which can significantly improve the low-temperature performance and high-temperature cycle life of the battery. When the second additive accounts for less than 1% of the electrolyte, the interface modification effect is insufficient, and a continuous and stable interface layer with high ionic conductivity cannot be formed. The low content of LiF component leads to a decrease in interface stability. When the second additive accounts for more than 10% of the electrolyte, excessive decomposition products are excessively deposited at the interface, forming an interface film with excessively high electronic conductivity, which aggravates the continuous decomposition of the electrolyte. At the same time, incompletely decomposed LiFSI may catalyze side reactions in the electrolyte, which has a negative impact on thermal safety.

[0036] Specifically, the percentage of the third additive in the electrolyte is any one of 0.5%, 1%, 1.5%, 2%, 2.5% or a range of any two of these values; in a preferred embodiment, the percentage of the third additive in the electrolyte is 1%-2%.

[0037] When the third additive accounts for 0.5%-2.5% of the electrolyte, its sulfonate groups form a stable interfacial protective layer at the electrode interface, which effectively inhibits electrolyte decomposition and transition metal dissolution. When the third additive accounts for less than 0.5% of the electrolyte, the interfacial stabilization effect is insufficient, the protective layer coverage is incomplete, and it cannot effectively inhibit the catalytic side reactions initiated by cobalt ions. When the third additive accounts for more than 2.5% of the electrolyte, the excessively dense protective layer leads to a significant increase in interfacial impedance, severely hindering ion transport. At the same time, excessive sulfonate groups may trigger electrolyte side reactions.

[0038] Specifically, the electrolyte retention coefficient is any one value or a range of any two values ​​selected from 0.7 g / Ah, 0.8 g / Ah, 0.9 g / Ah, 1 g / Ah, 1.1 g / Ah, 1.2 g / Ah, 1.3 g / Ah, 1.4 g / Ah, 1.5 g / Ah, 1.6 g / Ah, 1.7 g / Ah, 1.8 g / Ah, 1.9 g / Ah, 2 g / Ah, 2.1 g / Ah, 2.2 g / Ah, 2.3 g / Ah, 2.4 g / Ah, 2.5 g / Ah, 2.6 g / Ah, 2.7 g / Ah, 2.8 g / Ah, 2.9 g / Ah, or 3 g / Ah; in a preferred embodiment, the electrolyte retention coefficient is 1 g / Ah to 2.5 g / Ah.

[0039] When the electrolyte retention coefficient is between 0.7 g / Ah and 3 g / Ah, the three additives in the electrolyte are well-matched and further exert a synergistic effect to optimize the performance of lithium-ion batteries. When the electrolyte retention coefficient is less than 0.7 g / Ah, insufficient electrolyte wetting leads to uneven interfacial reactions, reduced utilization of active materials, and excessively high local current density accelerates interfacial degradation. When the electrolyte retention coefficient is greater than 3 g / Ah, excess electrolyte exacerbates side reactions at high temperatures, increases the risk of thermal runaway, and reduces the thermal safety of the battery.

[0040] Specifically, the range of values ​​for (A+B) / X is 0.002, 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, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1 The value is any one point value or a range of any two point values ​​from 0.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, or 2.05; in a preferred embodiment, the value range of (A+B) / X is 0.05-1.5.

[0041] When the value of (A+B) / X is in the range of 0.002-2.05, a balance between the total amount of additives and the degree of contamination at the cobalt impurity interface is ensured. When the value of (A+B) / X is less than 0.002, the total amount of additives will be severely insufficient relative to the cobalt impurity content. On the one hand, insufficient interface passivation leads to the continuous catalytic decomposition of the electrolyte by cobalt ions, generating unstable SEI components and causing a surge in interfacial impedance. On the other hand, the basic interfacial film synergistically constructed by VC and LiFSI cannot effectively complex free cobalt ions, making it difficult to inhibit the electrolyte oxidation and decomposition catalyzed by cobalt, and also unable to establish a stable ion transport channel, resulting in increased gas production during high-temperature cycling and a sharp decline in low-temperature discharge capacity. When the value of (A+B) / X is greater than 2.05, the total amount of additives will be relatively excessive. Excessive VC polymerization products will form an excessively thick insulating layer, severely hindering lithium-ion migration. Excessive fluoride deposition at the interface, while improving the high-temperature stability of the interfacial film, leads to increased electronic conductivity, exacerbating electrolyte decomposition. Furthermore, excessive additives increase side reactions and generate gaseous byproducts, negatively impacting thermal safety. (g / Ah) Specifically, the range of values ​​for (A+B+C) / P is 0.88, 1.25, 1.75, 2.25, 2.75, 3.25, 3.75, 4.25, 4.75, 5.25, 5.75, 6.25, 6.75, 7.25, 7.75, 8.25, 8.75, 9.25, 9.75, 10.25, 10.75, 11.25, and 11.75. The range of values ​​is any one point or any two points from 12.25, 12.75, 13.25, 13.75, 14.25, 14.75, 15.25, 15.75, 16.25, 16.75, 17.25, 17.75, 18.25, or 18.75; in a preferred embodiment, the value range of (A+B+C) / P is 2.25-16.25.

[0042] When the value of (A+B+C) / P ranges from 0.88 to 18.75, 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) / P is less than 0.88, the additive concentration allocated per unit volume of electrolyte is insufficient. In batteries with a low electrolyte retention coefficient, 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 cobalt ions, leading to uneven internal resistance distribution, rapid capacity decay, and a significant decrease in cycle stability. When the value of (A+B+C) / P is greater than 18.75, the additive concentration allocated per unit volume of electrolyte is excessively high. In batteries with a high liquid retention coefficient, 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.

[0043] Specifically, the value of C / (A+B) is any one value or a range of any two values ​​from 0.04, 0.07, 0.12, 0.17, 0.22, 0.27, 0.32, 0.37, 0.42, 0.47, 0.52, or 0.57; in a preferred embodiment, the value of C / (A+B) is 0.12-0.47.

[0044] When the C / (A+B) value ranges from 0.04 to 0.57, the ratio of basic film formation to interfacial stability protection is balanced. When the C / (A+B) value is less than 0.04, the relative content of the interfacial stabilizer PST is too low. The basic SEI film formed by VC and LiFSI lacks sufficient sulfonate ester stabilization, resulting in insufficient chemical and thermal stability. Under long-term cycling and thermal shock, it is difficult to maintain structural stability, and the interfacial film is easily degraded by the catalytic effect of cobalt ions. Its effect on improving high-temperature cycling performance and thermal safety is weak, failing to exert the expected synergistic protective effect. When the C / (A+B) value is greater than 0.57, the relative content of the interfacial stabilizer PST is too high. Excessive PST forms an overly dense protective layer at the interface. Although thermal stability is improved, this results in an overly rigid interfacial layer lacking toughness. This brittle interfacial layer cannot adapt to the expansion and contraction of the silicon anode, easily generating microcracks during cycling, thus losing its effective protective function. Meanwhile, 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 low-temperature performance and cycle life.

[0045] 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 cobalt, the electronic conductivity of the negative electrode is improved, promoting uniform nucleation and suppressing lithium dendrite growth.

[0046] The electrolyte of this invention employs a first additive, vinylene carbonate (VC), a second additive, lithium bisfluorosulfonyl imide (LiFSI), and a third additive, propanesulfonate lactone (PST). The first additive, vinylene carbonate (VC), 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 VC-formed interfacial film 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 VC may exacerbate interfacial reactions under extreme thermal shock, negatively affecting battery safety.

[0047] The second additive, lithium bisfluorosulfonylimide (LiFSI), is a functional lithium salt and additive. Its unique anionic structure enables the formation of a stable LiF-rich interface layer on the negative electrode surface. This interface layer exhibits excellent ionic conductivity, effectively promoting lithium-ion transport at low temperatures and significantly improving low-temperature cycling performance. It also inhibits the oxidative decomposition of the electrolyte at high voltages, thus having a significant positive impact on high-temperature cycling performance. However, LiFSI may catalyze electrolyte decomposition at high temperatures and participate in exothermic reactions under thermal abuse scenarios, thus posing a certain negative impact on thermal shock safety performance.

[0048] The third additive, propanesulfonate lactone (PST), forms a dense protective layer at the electrode interface through its sulfonate lactone groups. 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, resulting in a slight decrease in low-temperature performance.

[0049] An increase in the electrolyte retention factor (P) signifies an increase in the amount of electrolyte, which effectively improves ion transport performance at low temperatures and significantly enhances low-temperature cycling performance. However, excessive electrolyte can exacerbate side reactions at high temperatures and increase the risk of thermal runaway, thus negatively impacting thermal safety and high-temperature cycling performance.

[0050] The introduction of cobalt (X) into the negative electrode active material can lead to localized side reactions due to its catalytic activity. This can cause the SEI film to become unstable and thicken continuously. Simultaneously, cobalt 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 the volume expansion of silicon, exacerbating the breakage of the active material and negatively impacting thermal safety, low-temperature and high-temperature cycling performance.

[0051] In silicon-based anode battery systems, when the three additives mentioned above act simultaneously on the silicon-based anode, VC preferentially reduces at the anode to form an elastic SEI basic framework, effectively adapting to volume changes; LiFSI, by generating a LiF composite phase with high ionic conductivity, embeds itself in this framework to improve the ion transport efficiency of the interfacial film; and PST, by forming a stable sulfonate-based 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. Specifically, the flexible matrix provided by VC alleviates the brittleness issues that LiFSI and PST may cause; the optimized ion channels of LiFSI partially offset the low-temperature impedance caused by VC and PST; and the stable interfacial layer constructed by PST effectively suppresses catalytic side reactions caused by cobalt. The synergy of these three additives 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.

[0052] Furthermore, this application achieves better synergistic effects by controlling the mass percentage content of the first additive A (VC), the second additive B (LiFSI), and the third additive C (PST), and by combining the electrolyte retention coefficient P and the cobalt content X in the negative electrode active material, satisfying the relationships 0.002 ≤ (A+B) / X ≤ 2.05, 0.88 ≤ (A+B+C) / P ≤ 18.75, and 0.04 ≤ C / (A+B) ≤ 0.57, and when A% is 1%~15%, B% is 1%~10%, C% is 0.5%~2.5%, P is 0.7-3 g / Ah, and X is 5-2000 ppm. (A+B) / X ensures a balance between the total amount of additives and the degree of contamination at the cobalt impurity interface; (A+B+C) / P achieves a match between the chemical protection of additives and the degree of electrolyte wetting; C / (A+B) balances the ratio of basic film formation to interface stability protection. Through this multi-dimensional regulation, interfacial side reactions and SEI film instability caused by cobalt leaching and migration can be effectively suppressed, enabling the battery to achieve an optimal balance among various performance characteristics such as thermal shock safety, low-temperature cycling, and high-temperature cycling.

[0053] In one embodiment, the values ​​of A, B, and X satisfy the following condition: Equation 4: 0.004≤(A+B) / X≤1.80.

[0054] 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.

[0055] In one embodiment, the batteries with values ​​A, B, C, and P satisfy the following conditions: Equation 5: 3.33≤(A+B+C) / P≤14.33.

[0056] 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.

[0057] In one embodiment, the values ​​of A, B, and C satisfy the following condition: Equation 6: 0.05≤C / (A+B)≤0.28.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] In one embodiment, the cobalt 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.

[0063] In one embodiment, the cobalt element is introduced into the silicon particles through high-temperature solid-state reaction, chemical vapor deposition, or ion implantation. Using the above methods to introduce cobalt element into 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.

[0064] In one embodiment, the percentage content 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.

[0065] Specifically, the mass content 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 percentage content of silicon in the negative electrode active material layer is 10≤D≤90.

[0066] When the silicon content 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 silicon content 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 silicon content in the negative electrode active material layer is greater than 90%, it leads to decreased electrode structure stability, intensified volume expansion effect, relative insufficiency of binder and conductive agent, and significantly shortened cycle life.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] Specifically, the aforementioned organic solvents are selected primarily to dissolve the first additive, the second additive, the third additive, and the lithium salt.

[0071] 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.

[0072] 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.

[0073] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent and a positive electrode binder.

[0074] In some embodiments, the type of positive conductive agent mentioned in this invention is not limited, and any known conductive agent can be used.

[0075] 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.

[0076] 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.

[0077] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0078] 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.

[0079] 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.

[0080] In one embodiment, a separator is also included, the separator being located between the positive electrode and the negative electrode.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] In one embodiment, another aspect of the present invention provides an electrical device comprising a battery as described above.

[0085] 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.

[0086] The present invention will be further illustrated by the following examples.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] Table 1. Design of battery components for Examples 1-21 and Comparative Examples 1-23; Example 1 This embodiment illustrates the battery disclosed in this invention and includes the following operational steps: Preparation of positive electrode The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent acetylene black (SuperP) and polyvinylidene fluoride (PVDF) binder are mixed evenly in 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. Preparation of silicon-based anodes Preparation of cobalt-doped pure silicon: Cobalt is introduced into silicon particles by ion implantation; The negative electrode active material containing cobalt nanoparticles, silicon particles, negative electrode conductive agent acetylene black (Super P), thickener CMC and negative electrode binder SBR 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 negative electrode slurry. The mixed slurry is coated on both sides of the copper foil current collector, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet. The specific values ​​of cobalt content in the added negative electrode active material are shown in Table 1.

[0091] Preparation of electrolyte a. Mix ethylene carbonate (EC), propyl propionate (EP), 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. b. Add 1% of the first additive vinylene carbonate, 4% of the second additive lithium difluorosulfonyl imide, and 1% of the third additive propanesulfonate lactone to the colorless and transparent liquid obtained in step a, mix well, and obtain the electrolyte.

[0092] Manufacturing of lithium-ion batteries 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.

[0093] Examples 2-21 Examples 2-21 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: The mass percentages of the first additive in the electrolyte (A%), the second additive in the electrolyte (B%), the third additive in the electrolyte (C%), the electrolyte retention coefficient (Pg / Ah), the cobalt content in the negative electrode active material (X / ppm), the value of (A+B) / X, the value of (A+B+C) / P, and the value of C / (A+B) are all referenced in Table 1.

[0094] Comparative Examples 1-23 Comparative Examples 1-23 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, with the following differences: The mass percentages of the first additive in the electrolyte (A%), the second additive in the electrolyte (B%), the third additive in the electrolyte (C%), the electrolyte retention coefficient (Pg / Ah), the cobalt content in the negative electrode active material (X / ppm), the value of (A+B) / X, the value of (A+B+C) / P, and the value of C / (A+B) are all referenced in Table 1.

[0095] Performance testing The following performance tests were performed on Examples 1-21 and Comparative Examples 1-23 prepared above: 0℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were 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 was denoted as Y1, and the discharge capacity measured in the Nth cycle was denoted as Y2; the capacity in the Nth week was divided by the capacity in the first week to obtain the cycle capacity retention rate W2 = Y2 / Y1 in the Nth week. The cycle number of the lithium-ion battery when the cycle capacity retention rate W2 was 70% was recorded.

[0096] 45 °C Cycle Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were 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 was denoted as C1, and the discharge capacity measured in the Nth cycle was denoted as C2; the capacity in the Nth week was divided by the capacity in the first week to obtain the cycle capacity retention rate R2 = C2 / C1 in the Nth week. The cycle number of the lithium-ion battery when the cycle capacity retention rate R2 was 70% was recorded.

[0097] Thermal Shock Test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged at a rate of 0.2C to the cut-off voltage at 25 °C, and the cut-off current was 0.025C. The fully charged batteries were placed in an oven, and the oven was heated to 150 °C at a rate of 5 °C / min. After heating to 150 °C, it was kept warm for 60 min. If the battery did not catch fire or explode, it passed the test. The total number of batteries tested was 20.

[0098] The above test results are shown in Table 2.

[0099] Table 2 Comparing Example 2 with Comparative Examples 1, 3-4, and 7, it can be seen that when the electrolyte includes the first additive, the probability that the battery does not catch fire or explode during the thermal shock test is relatively high, and the cycle number when the cycle capacity retention rate of the battery reaches 70% in the 0 °C and 45 °C tests is relatively large; when the electrolyte does not include the first additive, the probability that the battery does not catch fire or explode during the thermal shock test is relatively low; and the cycle number when the cycle capacity retention rate of the battery reaches 70% in the 0 °C and 45 °C tests is relatively small, and the cycle capacity retention rate is relatively poor.

[0100] Comparing Example 2 with Comparative Examples 1, 2, 4, and 6, it can be seen that when the electrolyte includes the second additive, the probability of the battery not catching fire or exploding during the thermal shock test is higher, and the battery retains 70% of its cycle capacity for a greater number of cycles at 0°C and 45°C. When the electrolyte does not contain the second additive, the probability of the battery not catching fire or exploding during the thermal shock test is lower; and the battery retains 70% of its cycle capacity for a smaller number of cycles at 0°C and 45°C, indicating a poorer cycle capacity retention rate.

[0101] Comparing Example 2 with Comparative Example 1, Comparative Examples 2-3 and Comparative Example 5, it can be seen that when the electrolyte includes the third additive, the probability of the battery not catching fire or exploding during the thermal shock test is relatively high, and the battery retains 70% of its cycle capacity for a relatively long period of time when tested at 0°C and 45°C. When the electrolyte does not contain the third additive, the probability of the battery not catching fire or exploding during the thermal shock test is relatively low, and the battery retains 70% of its cycle capacity for a relatively short period of time when tested at 0°C and 45°C, indicating a poor cycle capacity retention rate.

[0102] Comparing Examples 1-3 and Comparative Examples 8-9, it can be seen that when the first additive accounts for 1%-15% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test exceeds 60%; and the battery retains 70% of its capacity for more than 350 cycles in both 0℃ and 45℃ tests. When the first additive accounts for less than 1% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is 40%, indicating lower safety; the battery retains 70% of its capacity for more than 300 cycles in both 0℃ and 45℃ tests, indicating poor capacity retention. When the first additive accounts for more than 15% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is 30%, indicating lower safety; the battery retains 70% of its capacity for more than 200 cycles in both 0℃ and 45℃ tests, indicating poor capacity retention.

[0103] Comparing Examples 4-6 and Comparative Examples 10-11, it can be seen that when the second additive accounts for 1%-10% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is 55%-70%; the battery retains 70% of its capacity after 340 cycles at 0℃ and 45℃. When the second additive accounts for less than 1% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is 40%, indicating lower safety; the battery retains 70% of its capacity after 0℃ and 45℃ tests for a relatively small number of cycles, indicating poor capacity retention. When the second additive accounts for more than 10% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is less than 30%, indicating lower safety; the battery retains 70% of its capacity after 0℃ and 45℃ tests for a relatively small number of cycles.

[0104] Comparing Examples 7-9 and Comparative Examples 12-13, it can be seen that when the third additive accounts for 0.5%-2.5% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test exceeds 60%; and the battery retains 70% of its cycle capacity for more than 330 cycles in both 0°C and 45°C tests. When the third additive accounts for less than 0.5% of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is 20%, indicating lower safety. When the third additive accounts for more than 2.5% of the electrolyte, the battery retains 70% of its cycle capacity for less than 300 cycles in both 0°C and 45°C tests, indicating poor cycle capacity retention.

[0105] Comparative Examples 10-12 and 14-15 show that when the liquid retention coefficient accounts for 0.7%-3% of the electrolyte content, the probability of the battery not catching fire or exploding during thermal shock testing is 45%-75%; and the battery retains 70% of its capacity for more than 350 cycles at both 0°C and 45°C. When the liquid retention coefficient accounts for less than 0.7% of the electrolyte content, the probability of the battery not catching fire or exploding during thermal shock testing is 20%, indicating lower safety; the battery retains 70% of its capacity for more than 300 cycles at both 0°C and 45°C, indicating poor capacity retention. When the liquid retention coefficient accounts for more than 3% of the electrolyte content, the probability of the battery not catching fire or exploding during thermal shock testing is 20%, indicating lower safety; the battery retains 70% of its capacity for more than 300 cycles at both 0°C and 45°C, indicating poor capacity retention.

[0106] Comparing Examples 13-15 and Comparative Examples 16-17, it can be seen that when the content of cobalt in the negative electrode active layer accounts for 5ppm-2000ppm of the electrolyte content, the probability of the battery not catching fire or exploding during thermal shock testing is 45%-70%; and the battery retains 70% of its capacity after cycles at 0℃ and 45℃ for more than 330 cycles. When the content of cobalt in the negative electrode active layer accounts for less than 5ppm of the electrolyte content, the battery does not ignite or explode during thermal shock testing. The probability of the battery not catching fire or exploding is 5%, indicating low safety. The battery's cycle capacity retention rate to 70% is less than 300 cycles in both 0℃ and 45℃ tests, indicating poor cycle capacity retention. When the first additive accounts for more than 2000 ppm of the electrolyte, the probability of the battery not catching fire or exploding in the thermal shock test is 40%, indicating low safety. The battery's cycle capacity retention rate to 70% is less than 300 cycles in both 0℃ tests, indicating poor cycle capacity retention.

[0107] Comparing Examples 16-17 and Comparative Examples 18-19, it can be seen that when the value of (A + B) / X is in the range of 0.002-2.05, the probability of the battery not catching fire or exploding in the thermal shock test is 50%-70%; and the battery retains 70% of its capacity after cycles at 0℃ and 45℃ for more than 270 cycles. When the value of (A + B) / X is less than 0.002, the battery retains 70% of its capacity after cycles at 0℃ and 45℃ for less than 230 cycles, indicating poor capacity retention. When the value of (A + B) / X is greater than 2.05, the probability of the battery not catching fire or exploding in the thermal shock test is 30%, indicating low safety.

[0108] Comparing Examples 18-19 and Comparative Examples 20-21, it can be seen that when the value of (A+B+C) / P is in the range of 0.88-18.75, the probability of the battery not catching fire or exploding during thermal shock testing is 45%-70%; and the battery retains 70% of its capacity for more than 310 cycles at both 0℃ and 45℃. When the value of (A+B+C) / P is less than 0.88, the battery retains 70% of its capacity for less than 300 cycles at both 0℃ and 45℃, indicating poor capacity retention. When the value of (A+B+C) / P is greater than 18.75, the battery retains 70% of its capacity for less than 300 cycles at both 0℃ and 45℃, indicating poor capacity retention.

[0109] Comparing Examples 20-21 and Comparative Examples 22-23, it can be seen that when the value of C / (A+B) is in the range of 0.04-0.57, the probability that the battery will not catch fire or explode during the thermal shock test is 45%-85%; and the battery retains 70% of its capacity after cycles at 0℃ and 45℃ for more than 340 cycles. When the value of C / (A+B) is less than 0.04, the battery retains 70% of its capacity after cycles at 0℃ and 45℃ for less than 300 cycles, indicating poor capacity retention. When the value of C / (A+B) is greater than 0.57, the probability that the battery will not catch fire or explode during the thermal shock test is 30%.

[0110] This application achieves better synergistic effects by controlling the mass percentages of the first additive A (VC), the second additive B (LiFSI), and the third additive C (PST), and combining this with the electrolyte retention coefficient P and the cobalt content X in the negative electrode active material, satisfying the relationships 0.002 ≤ (A+B) / X ≤ 2.05, 0.88 ≤ (A+B+C) / P ≤ 18.75, and 0.04 ≤ C / (A+B) ≤ 0.57. Furthermore, when A% is 1%~15%, B% is 1%~10%, C% is 0.5%~2.5%, P is 0.7-3 g / Ah, and X is 5-2000 ppm, this approach ensures a balance between the total amount of additives and the degree of contamination at the cobalt impurity interface; (A+B+C) / P achieves a match between the chemical protection of the additives and the degree of electrolyte wetting; 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 the dissolution and migration of cobalt 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.

[0111] 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 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 layer comprising a negative electrode active material, the negative electrode active material comprising silicon particles and cobalt element, the mass content X of cobalt element in the negative electrode active material layer, the value of X being in the range of 5ppm-2000ppm; 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(fluorosulfonyl)imide; and the third additive comprising propanesulfonate lactone. The total mass of the electrolyte is denoted as 100%. The percentage of the first additive in the electrolyte is denoted as A, in %, with a value ranging from 1 to 15. The percentage of the second additive in the electrolyte is denoted as B, in %, with a value ranging from 1 to 10. The percentage of the third additive in the electrolyte is denoted as C, in %, with a value ranging from 0.5 to 2.

5. The electrolyte retention coefficient is denoted as P, in g / Ah, with a value ranging from 0.7 to 3. The values ​​of A, B, C, P, and X satisfy the following condition: Equation 1: 0.002 ≤ (A+B) / X ≤ 2.05; Equation 2: 0.88≤(A+B+C) / P≤18.75; Equation 3: 0.04≤C / (A+B)≤0.

57.

2. The battery according to claim 1, characterized in that, The values ​​of A, B, and X satisfy the following conditions: Equation 4: 0.004≤(A+B) / X≤1.

80.

3. The battery according to claim 1, characterized in that, The batteries with values ​​A, B, C, and P satisfy the following conditions: Equation 5: 3.33≤(A+B+C) / P≤14.

33.

4. The battery according to claim 1, characterized in that, The values ​​A, B, and C satisfy the following conditions: Equation 6: 0.05≤C / (A+B)≤0.

28.

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

6. The battery according to claim 5, characterized in that, The cobalt element exists in the form of a dopant within the crystal lattice or at the grain boundaries of the silicon particles.

7. The battery according to any one of claims 5 or 6, characterized in that, The cobalt element is introduced into the silicon particles through high-temperature solid-state reaction, chemical vapor deposition, or ion implantation.

8. The battery according to claim 1, characterized in that, The percentage content of silicon in the negative electrode active material layer is denoted as D, and the unit is %. The value of D is in the range of 10≤D≤90.

9. The battery according to claim 1, characterized in that, The electrolyte further includes lithium salts and organic solvents. The lithium salts include 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 solvents include one or more of ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, methyl acetate, 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.

10. The battery according to claim 1, characterized in that, It also 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.

11. The battery according to claim 10, 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.

12. An electrical appliance, characterized in that, The battery includes any one of claims 1 to 11.

Images