Lithium ion battery and electric device

Abstract

The invention provides a lithium ion battery and a power utilization device, the lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte, the negative electrode comprises a negative electrode active layer, the negative electrode active layer comprises a negative electrode active material, the positive electrode comprises a positive electrode active layer, the positive electrode active layer comprises a carbon nanotube and a positive electrode active material, and the positive electrode active material is doped with lanthanum element; the electrolyte comprises a solvent, an additive and an electrolyte salt, the first solvent comprises a fluoro-amide solvent, the second solvent comprises a fluoro-linear carbonate solvent, the first additive comprises mannitol carbonate sulfate, and the second additive comprises a lithium salt additive; the lithium ion battery satisfies the following conditions: (A + C + D) * 10000 / X is greater than or equal to 1.23 and less than or equal to 21; 0.05 < = (C + D) * 100 / (B + W) < = 3.16; 3.23 < = (C + H) / B < = 97.30; 5 < = A < = 30, 5 < = B < = 30, 0.5 < = C < = 4, 0.3 < = D < = 3, 0.5 < = H < = 6, 100 < = X < = 800, and 1 < = W < = 30; according to the lithium ion battery provided by the invention, the thermal shock safety and the high-low temperature cycle performance of the lithium ion battery are improved through cooperation of the multiple components and a relational expression met by the multiple components.

Description

A lithium-ion battery and power device Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a lithium-ion battery and an electrical device thereof. Background Technology

[0002] With the increasing demands for energy density, power density, and safety from electric vehicles and energy storage systems, there is an urgent need to develop a high-performance lithium-ion battery that can operate stably in harsh environments. At the same time, this lithium-ion battery is required to achieve excellent low-temperature (e.g., 0°C) cycle performance, good high-temperature (e.g., 45°C) cycle stability, and high thermal shock safety. However, there are often inherent contradictions between these performance indicators that are difficult to reconcile.

[0003] Specifically, to improve low-temperature performance, it is generally necessary to reduce the viscosity and melting point of the electrolyte. Fluorinated linear carbonate solvents are considered promising low-temperature functional solvents due to their low viscosity and the antioxidant properties provided by moderate fluorination. However, their linear ester bond structure has limited chemical stability under severe thermal shock, posing a high risk of thermal runaway. To improve safety, carbon nanotubes (CNTs) can be introduced into the cathode to construct a thermally conductive network, or highly stable additives that preferentially form films on the cathode (such as mannitol carbonate sulfate containing sulfate groups, CBS) can be used. However, excessive CNTs can clog electrode pores, while excessive CBS may form a high-resistance interfacial film, both of which can impair the rate performance and cycle life of the battery. Similarly, using highly stable solvents such as fluoroamides can improve overall oxidation stability, but their high viscosity may be detrimental to low-temperature ion conduction. In addition, while doping with rare earth elements such as lanthanum (La) can effectively stabilize the crystal structure of cathode materials, the doping amount needs to be precisely controlled, otherwise it will be difficult to achieve the desired effect.

[0004] Furthermore, existing technologies often focus on optimizing a single component (such as a novel solvent or additive) or a single performance, lacking a systematic and quantitative synergistic approach that integrates electrolyte chemistry (solvents, additives), electrode material bulk modification (elemental doping), electrode microstructure (conductive / thermal network), and negative electrode physical properties (specific surface area). While each component can leverage its own advantages, its potential negative effects may be amplified, making it impossible to achieve the optimal balance of overall performance. Summary of the Invention

[0005] To address the technical problem of the difficulty in synergistically optimizing thermal shock safety and high and low temperature cycling performance in existing lithium-ion batteries, a lithium-ion battery and power device are provided.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode comprises a negative electrode active layer, the negative electrode active layer comprising a negative electrode active material. The positive electrode comprises a positive electrode active layer, the positive electrode active layer comprising carbon nanotubes and a positive electrode active material, the positive electrode active material being doped with lanthanum. The electrolyte comprises a solvent, an additive, and an electrolyte salt. The solvent comprises a first solvent and a second solvent. The additive comprises a first additive and a second additive. The first solvent comprises a fluoroamide solvent, the second solvent comprises a fluorolinear carbonate solvent, the first additive comprises mannitol sulfate carbonate, and the second additive comprises a lithium salt additive. The lithium-ion battery satisfies the following condition: 1.23 ≤ (A+C+D)*10000 / X≤21; 0.05≤(C+D)*100 / (B+W)≤3.16; 3.23≤(C+H) / B≤97.30; and, 5≤A≤30, 5≤B≤30, 0.5≤C≤4, 0.3≤D≤3, 0.5≤H≤6, 100≤X≤800, 1≤W≤30; where A% is the mass percentage of the first solvent in the electrolyte; B% is the mass percentage of the second solvent in the electrolyte; C% is the mass percentage of the first additive in the electrolyte; D% is the mass percentage of the second additive in the electrolyte; H% is the mass percentage of carbon nanotubes in the positive electrode active layer; X is the content of lanthanum in the positive electrode active material, in ppm; W is the specific surface area of ​​the negative electrode active material, in m². 2 / g.

[0007] Optionally, the lithium-ion battery satisfies the following condition: 2.00≤(A+C+D)*10000 / X≤18.00.

[0008] Optionally, the lithium-ion battery satisfies the following condition: 0.10≤(C+D)*100 / (B+W)≤2.61.

[0009] Optionally, the lithium-ion battery satisfies the following condition: 3.47≤(C+H) / B≤40.40.

[0010] Optionally, the lithium-ion battery satisfies one of the following conditions: (1) 10≤A≤25; (2) 10≤B≤25; (3) 1≤C≤3; (4) 0.5≤D≤2; (5) 1≤H≤5; (6) 200≤X≤600; (7) 4≤W≤20.

[0011] Optionally, the first solvent comprises one or more of dimethylaminosulfonyl fluoride, 1,1,1-trifluoro-N,N-dimethylformamide, and N,N-diethylaminosulfonyl fluoride; and / or, the second solvent comprises one or more of methyltrifluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, ethyl (2,2,2-trifluoroethyl) carbonate, and di(monofluoromethyl) carbonate.

[0012] Optionally, the electrolyte salt includes one or more of lithium difluoroimide, lithium bis(trifluoroimide), lithium dioxaborate, lithium difluorophosphate, lithium difluorooxaborate, and lithium tetrafluoroborate.

[0013] Optionally, the positive electrode active material includes a transition metal lithium oxide; 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; where M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0014] Optionally, the negative electrode active material includes one or more of graphite, silicon-carbon composite materials, and lithium metal materials.

[0015] On the other hand, the present invention provides an electrical device including the aforementioned lithium-ion battery.

[0016] The beneficial effects of this application are as follows: The lithium-ion battery provided by this application utilizes a fluoroamide-based first solvent, which, due to its high dielectric constant and good thermal stability, facilitates the formation of a stable negative electrode SEI film and improves the high-voltage stability of the battery. A fluorolinear carbonate-based second solvent possesses low viscosity characteristics to optimize low-temperature ion conduction. The two solvents work synergistically to form an electrolyte solvent system with stability and excellent kinetic performance. Mannitol carbonate sulfate, as the first additive, preferentially forms a dense and stable CEI film on the positive electrode surface, inhibiting electrolyte decomposition and transition metal dissolution. The inorganic components generated from the decomposition of the lithium salt-based second additive can synergistically optimize the ionic conductivity and mechanical strength of the positive and negative electrode interface film. The combination of these two types of additives and the solvent system achieves precise reinforcement of interface protection. Furthermore, the lanthanum doped in the positive electrode active material stabilizes the crystal structure, inhibiting lattice oxygen loss and structural collapse. Carbon nanotubes can form a three-dimensional conductive and thermally conductive network, promoting heat diffusion and electrical conductivity. The lanthanum doping in the positive electrode active material, along with the synergistic effect of carbon nanotubes with both positive and negative electrode active materials, enables the battery to simultaneously achieve excellent low-temperature cycling performance. Furthermore, preliminary experiments have verified that when the mass percentages of the first solvent in the electrolyte (A%), the second solvent (B%), the first additive (C%), the second additive (D%), the carbon nanotubes in the positive electrode active layer (H%), the lanthanum content in the positive electrode active material (X%), and the specific surface area W of the negative electrode active material satisfy the following relationships: 1.23 ≤ (A+C+D)*10000 / X ≤ 21, 0.05 ≤ (C+D)*100 / (B+W) ≤ 3.16, and 3.23 ≤ (C+H) / B ≤ 97.30, the lithium-ion battery can simultaneously achieve excellent low-temperature cycling performance, high-temperature cycling stability, and thermal shock safety. Detailed Implementation

[0017] To make the technical problems solved, the technical solutions, and the 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.

[0018] This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode active layer comprising a negative electrode active material. The positive electrode includes a positive electrode active layer comprising carbon nanotubes and a positive electrode active material, wherein the positive electrode active material is doped with lanthanum. The electrolyte comprises a solvent, an additive, and an electrolyte salt. The solvent comprises a first solvent and a second solvent. The additive comprises a first additive and a second additive. The first solvent comprises a fluoroamide solvent, and the second solvent comprises a fluorolinear carbonate solvent. The first additive comprises mannitol sulfate carbonate (CBS, compound c), and the second additive comprises a lithium salt additive. The lithium-ion battery satisfies the following condition: 1.23 ≤ (A+C+D)* 10000 / X≤21; 0.05≤(C+D)*100 / (B+W)≤3.16; 3.23≤(C+H) / B≤97.30; and, 5≤A≤30, 5≤B≤30, 0.5≤C≤4, 0.3≤D≤3, 0.5≤H≤6, 100≤X≤800, 1≤W≤30; where A% is the mass percentage of the first solvent in the electrolyte; B% is the mass percentage of the second solvent in the electrolyte; C% is the mass percentage of the first additive in the electrolyte; D% is the mass percentage of the second additive in the electrolyte; H% is the mass percentage of carbon nanotubes in the positive electrode active layer; X is the content of lanthanum in the positive electrode active material, in ppm; W is the specific surface area of ​​the negative electrode active material, in m². 2 / g.

[0019] It should be noted that the first solvent (fluoroamide solvent), such as dimethylamino fluoride, with its highly polar amide groups and fluorine atoms, endows the electrolyte with a high dielectric constant and excellent oxidation / thermal stability, and can participate in the formation of a stable negative electrode SEI film, which is the basis for improving the battery's high-voltage cycle and overall thermal stability.

[0020] The second solvent (fluorinated linear carbonate solvent), such as methyl trifluoroethyl carbonate, retains the low viscosity advantage of linear carbonates while improving oxidation resistance through fluorination. It is a core kinetic component that significantly improves the low-temperature performance (0°C cycling) of batteries.

[0021] The first additive, such as mannitol carbonate sulfate (CBS), is a multifunctional additive containing sulfate groups. Its high reactivity allows it to preferentially oxidize on the positive electrode surface to form a dense positive electrode electrolyte interface (CEI) film rich in inorganic lithium salts (such as Li2SO3 / Li2SO4). This film strongly inhibits electrolyte decomposition and transition metal dissolution, thereby significantly improving the thermal shock safety of the battery.

[0022] Secondary additives (lithium salt additives): such as LiPO2F2 and LiDFOB. These additives can decompose to produce LiF and Li3PO4 components, which synergistically participate in the construction of the positive and negative electrode interface films, optimize the ionic conductivity and mechanical strength of the interface films, slightly improve thermal stability and affect cycle performance.

[0023] Lanthanum (La) in the positive electrode active material enters the lattice of the positive electrode material (such as high-nickel ternary material) in the form of doping. With its large ionic radius and strong La-O bond, it plays a pillar effect, stabilizes the layered structure, and inhibits the loss of lattice oxygen and structural collapse under high temperature / high pressure, thereby improving the intrinsic thermal and cycling stability of the material from the bulk phase level.

[0024] A carbon nanotube (CNT) network, uniformly dispersed within the cathode active material layer, constructs a three-dimensional electronic and thermal conductivity network. This network not only improves the uniformity of electronic conductivity in the electrode but also rapidly dissipates localized heat, significantly enhancing the overall thermal safety of the electrode from a structural perspective.

[0025] The specific surface area (W) of the negative electrode active material directly affects the number of reactive sites for lithium-ion insertion / extraction. A larger specific surface area is beneficial for improving low-temperature reaction kinetics (improving 0°C cycling), but it also increases the side reaction interface with the electrolyte, which has a complex impact on thermal stability and long-term cycling.

[0026] Specifically, the lithium-ion battery provided in this application utilizes a fluoroamide-based first solvent, which, due to its high dielectric constant and good thermal stability, facilitates the formation of a stable negative electrode SEI film and improves the battery's high-voltage stability. A fluorolinear carbonate-based second solvent, with its low viscosity, optimizes low-temperature ion conduction. Together, they form a stable electrolyte solvent system with excellent kinetic performance. Mannitol carbonate sulfate, as the first additive, preferentially forms a dense and stable CEI film on the positive electrode surface, inhibiting electrolyte decomposition and transition metal dissolution. The inorganic components generated from the decomposition of the lithium salt-based second additive synergistically optimize the ionic conductivity and mechanical strength of the positive and negative electrode interface film. The combination of these two types of additives and the solvent system achieves precise reinforcement of interface protection. Furthermore, the lanthanum doped in the positive electrode active material stabilizes the crystal structure, inhibiting lattice oxygen loss and structural collapse, while carbon nanotubes form a three-dimensional conductive and thermally conductive network, promoting heat diffusion and electron exchange. The transmission of lanthanum doped in the positive electrode active material, along with carbon nanotubes, works synergistically with both positive and negative electrode active materials to simultaneously ensure battery stability and high / low temperature cycling performance. Preliminary experiments have verified that when the mass percentages of the first solvent in the electrolyte (A%), the second solvent (B%), the first additive (C%), the second additive (D%), the carbon nanotubes in the positive electrode active layer (H%), the lanthanum content in the positive electrode active material (X%), and the specific surface area W of the negative electrode active material satisfy the following relationships: 1.23 ≤ (A+C+D)*10000 / X ≤ 21, 0.05 ≤ (C+D)*100 / (B+W) ≤ 3.16, and 3.23 ≤ (C+H) / B ≤ 97.30, lithium-ion batteries can simultaneously achieve excellent low-temperature cycling performance, high-temperature cycling stability, and thermal shock safety.

[0027] The relationship 1.23≤(A+C+D)*10000 / X≤21 represents the total amount of active components in the electrolyte that participate in constructing and strengthening the electrode interface (SEI / CEI). Fluoroamide solvents (A) contribute to the stable negative electrode SEI and overall oxidation stability, mannitol carbonate sulfate (C) focuses on the high stability of the positive electrode CEI, and lithium salt additives (D) synergistically optimize the inorganic components of the interface. Lanthanum (X) plays a role in strengthening the intrinsic structural stability of the positive electrode material. If the ratio of this relationship is too small (<1.23), the interface protection is relatively insufficient, and it cannot effectively suppress side reactions, thus failing to achieve optimal thermal shock and cycling performance. If the ratio is too large (>21), it means that the interface film may be too thick, increasing resistance, and the stability of the cathode phase is insufficient, leading to a simultaneous deterioration of thermal shock and cycling performance. That is, controlling the ratio of the relationship (A+C+D)*10000 / X between 1.23 and 21 ensures that the external interface protection and the internal phase stability achieve a good synergistic state.

[0028] In the formula (0.05≤(C+D)*100 / (B+W)≤3.16), (C+D) represents the total amount of core additives for constructing a stable interfacial film. In (B+W), the fluorinated linear carbonate solvent (B) directly determines the low-temperature ionic conductivity, and the specific surface area of ​​the negative electrode (W) quantifies the reaction interface size. Together, they determine the battery's reaction kinetic potential. If this ratio is too small (<0.05), it indicates a severe deficiency of film-forming agent in systems with high kinetic requirements, resulting in interface protection failure and poor thermal shock performance. If the ratio is too large (>3.16), it indicates an excess of film-forming agent, where the formed interfacial film severely hinders ion transport, significantly shortening the low-temperature and high-temperature cycle life. Maintaining this ratio between 0.05 and 3.16 ensures excellent low-temperature ion transport and rapid interfacial reaction while constructing a stable interface to withstand harsh operating conditions.

[0029] (3.23≤(C+H) / B≤97.30), where mannitol carbonate sulfate (C) suppresses the exothermic reaction at the positive electrode through chemical film formation, and CNTs (H) promote uniform heat diffusion through a physical thermally conductive network. Fluorinated linear carbonate solvents (B) have relatively poor thermal stability. If the ratio is too small (<3.23), it indicates insufficient thermal stability to control the thermal decomposition of the fluorinated linear carbonate solvent, resulting in extremely poor thermal shock safety. If the ratio is too large (>97.30), although thermal safety is high, excessive CNTs and fluorinated amide solvents will severely impair ion transport, leading to deterioration in cycle performance. Therefore, controlling the (C+H) / B ratio between 3.23 and 97.30 can achieve excellent thermal safety while maintaining good electrochemical performance of the battery to the greatest extent.

[0030] Furthermore, through verification using relevant embodiments and comparative examples, when the mass percentage A% of the first solvent in the electrolyte is 5-30%, it ensures that the content of the fluoroamide-based first solvent is sufficient to form a stable negative electrode SEI film and improve the battery's high voltage and thermal stability. If it is less than 5%, the highly stable solvent is insufficient, affecting the negative electrode film formation and high voltage stability. If it is greater than 30%, the electrolyte viscosity is too high, damaging the ionic conductivity. When the mass percentage B% of the second solvent in the electrolyte is 5-30%, it is beneficial for the fluorolinear carbonate-based second solvent to fully utilize its low viscosity advantage and optimize low-temperature ion conduction. If it is less than 5%, the improvement on low-temperature performance is limited. If it is greater than 30%, the thermal stability is severely degraded, and the risk increases dramatically. When the mass percentage C% of the first additive in the electrolyte is 0.5-4%, it ensures that the mannitol carbonate sulfate first additive can form a dense and stable CEI at the positive electrode. The membrane inhibits electrolyte decomposition and transition metal dissolution. If the content is below 0.5%, the positive electrode CEI protection is insufficient and the thermal stability is poor. If it is above 4%, the CEI membrane impedance is too high, affecting cycle performance. When the mass percentage D% of the second additive in the electrolyte is 0.3%~3%, the lithium salt second additive can effectively decompose into inorganic components to synergistically optimize the performance of the positive and negative electrode interface membrane. If it is below 0.3%, the synergistic optimization effect on the interface is weak. If it is above 3%, it may increase viscosity and lead to interface inhomogeneity. When the mass percentage H% of the carbon nanotubes in the positive electrode active layer is 0.5%~6%, it is beneficial for the carbon nanotubes to form a membrane. The active material forms an effective three-dimensional conductive and thermally conductive network, promoting heat diffusion and electron transport, while avoiding excessive clogging of electrode pores and increased electrode impedance. If the content is below 0.5%, an effective network cannot be formed; if it is above 6%, pores are severely clogged, increasing impedance. When the lanthanum content X in the positive electrode active material is 100~800ppm, it ensures that lanthanum doping effectively stabilizes the positive electrode crystal structure and inhibits lattice oxygen loss and structural collapse. If it is below 100ppm, the bulk stability effect is weak; if it is above 800ppm, defects may be introduced, reducing capacity and diffusion coefficient. The specific surface area W of the negative electrode active material is 1~30m². 2 / g, ensuring sufficient reaction interface for the negative electrode active material to improve low-temperature kinetic performance; if below 1m 2 / g, slow kinetics at low temperatures, above 30m 2 / g, severe side reactions, deteriorated thermal stability and cycling performance; furthermore, the mass percentage of the first solvent in the electrolyte is, but not limited to, 5%, 8%, 10%, 15%, 20%, 25% or 30%; the mass percentage of the second solvent in the electrolyte is, but not limited to, 5%, 6%, 8%, 10%, 15%, 17%, 20%, 25% or 30%; the mass percentage of the first additive in the electrolyte is, but not limited to, 0.5%, 0.8%, 1%, 2%, 2.5%, 3%, 3.8% or 4%; the mass percentage of the second additive in the electrolyte is, but not limited to, 0.3%, 0.4%, 0.5%, 1%, 1.3%. The percentage of carbon nanotubes in the positive electrode active layer is, but is not limited to, 0.5%, 0.8%, 1%, 2%, 2.5%, 3%, 4%, 5%, 5.8%, or 6%. The content of lanthanum in the positive electrode active material is, but is not limited to, 100ppm, 150ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 750ppm, or 800ppm. The specific surface area of ​​the negative electrode active material is, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 15%, 20%, 25%, 28%, or 30%.

[0031] The method for determining the carbon nanotube content in the positive electrode active layer includes: scraping material from the positive electrode active layer, grinding it to obtain a uniform powder, and accurately weighing it. Thermogravimetric analysis (TGA) is used for testing. In a dry air atmosphere, the temperature is increased from room temperature to 900℃ at a rate of 10℃ / min. Carbon nanotubes (CNTs) undergo oxidative decomposition within a characteristic temperature range of 500-800℃. By analyzing the thermogravimetric (TG) curve, the percentage of weight loss due to CNT oxidation within this characteristic weight loss range is accurately calculated. After deducting the background weight loss from other components such as binders and conductive carbon black, the mass percentage H of CNTs in the positive electrode active layer can be calculated.

[0032] The method for determining the lanthanum content in the positive electrode active material includes: accurately scraping an appropriate amount of powder from the prepared positive electrode active layer, pretreating the sample using a microwave digestion method with concentrated acid (a mixture of nitric acid, hydrochloric acid, and hydrofluoric acid), testing the lanthanum (La) content in the digestion solution using inductively coupled plasma optical emission spectrometry (ICP-OES), and calculating the mass content of lanthanum in the positive electrode active material, in ppm.

[0033] Determination of the specific surface area of ​​the negative electrode active material: The static volumetric method using nitrogen adsorption (BET) principle was employed, and a fully automated specific surface area and porosity analyzer was used to test the negative electrode active material (such as graphite) powder. The sample required thorough vacuum degassing before testing to obtain an accurate specific surface area value, expressed in m². 2 / g.

[0034] In some embodiments, the lithium-ion battery satisfies the following condition: 2.00≤(A+C+D)*10000 / X≤18.00.

[0035] Specifically, further limiting the above relationship to 2.00≤(A+C+D)*10000 / X≤18.00 is beneficial to further optimize the matching between the total strength of the interface protection and the stability of the positive electrode phase structure, thereby improving the high-temperature cycle stability and thermal shock safety of lithium-ion batteries.

[0036] In some embodiments, the lithium-ion battery satisfies the following condition: 0.10≤(C+D)*100 / (B+W)≤2.61.

[0037] Specifically, by further limiting the above relationship to 0.10≤(C+D)*100 / (B+W)≤2.61, the amount of film-forming additives and low-temperature kinetic requirements can be more accurately matched, avoiding the problem of insufficient interface protection due to slightly less additives at the boundary of the basic range, or slight obstruction of ion transport due to slightly more additives, and further extending the low-temperature cycle life.

[0038] In some embodiments, the lithium-ion battery satisfies the following condition: 3.47 ≤ (C+H) / B ≤ 40.40.

[0039] Specifically, the above relationship is further limited to 3.47≤(C+H) / B≤40.40, and the ratio of thermally stable component to thermally unstable solvent is further optimized to achieve a higher thermal shock pass rate while maintaining better electrochemical kinetic performance.

[0040] In some embodiments, the lithium-ion battery satisfies one of the following conditions: (1) 10≤A≤25; (2) 10≤B≤25; (3) 1≤C≤3; (4) 0.5≤D≤2; (5) 1≤H≤5; (6) 200≤X≤600; (7) 4≤W≤20.

[0041] Specifically, the optimal ranges for the above parameters are based on the optimal value intervals obtained from previous experimental verification. For example, further limiting the range of A to 10≤A≤25 ensures that the content of the fluoroamide primary solvent is sufficient to form a stable negative electrode SEI film and improve the high-voltage stability of the battery, while avoiding excessive amounts that would lead to excessive electrolyte viscosity and impair ion conduction. Narrowing the range of W to 4≤W≤20 ensures that the negative electrode active material has sufficient reaction interface to improve low-temperature kinetic performance, while avoiding excessive specific surface area that would exacerbate side reactions with the electrolyte and worsen thermal stability. Parameters within their optimal ranges allow the function of each component to reach its best state, while minimizing the negative effects of any single component. This provides a better single-material basis for the global synergy of all components from a mechanistic perspective, further enhancing the synergistic effect of battery thermal shock safety and high / low temperature cycling performance.

[0042] In some embodiments, the first solvent comprises one or more of dimethylaminosulfonyl fluoride (compound a-1), 1,1,1-trifluoro-N,N-dimethylformamide (compound a-2), and N,N-diethylaminosulfonyl fluoride (compound a-3); and / or, the second solvent comprises one or more of methyltrifluoroethyl carbonate (compound b-1), bis(2,2,2-trifluoroethyl) carbonate (compound b-2), ethyl (2,2,2-trifluoroethyl) carbonate (compound b-3), and di(monofluoromethyl) carbonate (compound b-4).

[0043] Specifically, the aforementioned first solvents, such as dimethylaminosulfonyl fluoride, all share the common characteristics of high dielectric constant and excellent oxidation and thermal stability, enabling them to stably participate in the formation of the negative electrode SEI film and improve the battery's high voltage and thermal stability. The second solvents, such as methyltrifluoroethyl carbonate, retain the low viscosity characteristics of linear carbonates and, through fluorination modification, enhance oxidation resistance, effectively optimizing low-temperature ion conduction. These specific compounds in the first and second solvents mechanistically ensure the synergistic effect of the electrolyte solvent system's thermal stability and low-temperature kinetics, providing a stable electrolyte foundation for the overall thermal shock safety and high- and low-temperature cycling performance of lithium-ion batteries.

[0044] In some embodiments, the electrolyte salt includes one or more of lithium difluoroimide, lithium bis(trifluoroimide), lithium dioxaborate, lithium difluorophosphate, lithium difluorooxaborate, and lithium tetrafluoroborate.

[0045] The use of any one or more of the aforementioned lithium salt additives as the second additive is beneficial for optimizing battery performance. Specifically, such electrolyte salts are functional lithium salts with excellent compatibility in the field of lithium-ion batteries. They can effectively participate in the formation process of the positive and negative electrode interface film, optimize the inorganic composition of the interface film, improve the ionic conductivity, mechanical strength and thermal stability of the interface film, ensure the chemical stability of the electrolyte system, and avoid electrolyte performance degradation due to component incompatibility.

[0046] In some embodiments, the positive electrode active material comprises a transition metal lithium oxide; 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; where M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0047] Specifically, the transition metal lithium oxide Li 1+x Ni y Co z M (1-y-z) The layered crystal structure of O2 provides a smooth transport channel for lithium-ion insertion and extraction. Furthermore, the various choices of transition metal lithium oxide M elements can form a dual doping modification effect with lanthanum elements doped in the cathode active material, further enhancing the thermal and electrochemical stability of the cathode phase structure. This avoids phase transitions and oxygen loss in the cathode material under high voltage and high and low temperature cycling, improving the cycle life and thermal safety of the cathode active material. At the same time, this type of transition metal lithium oxide has excellent compatibility with the carbon nanotube conductive network in the cathode, which can give full play to the electron transport advantages of the three-dimensional conductive network, reduce the internal resistance of the electrode, and thus form a performance synergy with the interface protection and low temperature transport characteristics of the electrolyte system, promoting the simultaneous improvement of the thermal shock safety and high and low temperature cycling performance of lithium-ion batteries.

[0048] The positive electrode includes a positive current collector. In this application, there is no particular limitation on the type of positive current collector, which can be any known material suitable for use as a positive current collector, including aluminum, stainless steel, nickel plating, titanium, tantalum metal materials, as well as carbon cloth and carbon paper.

[0049] The positive electrode active layer also includes a positive electrode conductive agent, a positive electrode binder, and a solvent.

[0050] In some embodiments, the present invention does not limit the type of positive conductive agent mentioned, and any known conductive agent may be used.

[0051] 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.

[0052] In some embodiments, the present invention does not limit the type of positive electrode binder, and any known positive electrode binder may be used.

[0053] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0054] In some embodiments, the negative electrode active material includes one or more of graphite, silicon-carbon composite materials, and lithium metal materials.

[0055] The negative electrode active layer also includes a negative electrode conductive agent, a negative electrode binder, a thickener, and a solvent. The negative electrode conductive agent includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The negative electrode binder includes styrene-butadiene latex, the thickener includes CMC, and the solvent includes deionized water.

[0056] The application does not impose any particular restrictions 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, foamed nickel, foamed copper, or composite current collector, etc.

[0057] In some preferred embodiments, the negative current collector comprises copper foil.

[0058] In the lithium-ion battery mentioned in this application, a separator is usually provided between the positive and negative electrodes to prevent short circuits. This application does not impose any particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application.

[0059] In some embodiments, the diaphragm comprises a porous sheet-like or non-woven material with excellent liquid retention properties, and the diaphragm comprises a resin or glass fiber diaphragm material, which includes, but is not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and polyethylene.

[0060] In some embodiments, the outer packaging of a lithium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.

[0061] The outer packaging of lithium-ion batteries can also be a soft pack, such as a pouch-type soft pack.

[0062] The material for flexible packaging can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0063] This application does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.

[0064] Another embodiment of the present invention provides an electrical device including the aforementioned lithium-ion battery.

[0065] The lithium-ion battery provided in this application utilizes a fluoroamide-based first solvent, which, due to its high dielectric constant and good thermal stability, facilitates the formation of a stable negative electrode SEI film and improves the battery's high-voltage stability. A fluorolinear carbonate-based second solvent, with its low viscosity, optimizes low-temperature ion conduction. Together, they form a stable electrolyte solvent system with excellent kinetic performance. Mannitol carbonate sulfate, as the first additive, preferentially forms a dense and stable CEI film on the positive electrode surface, inhibiting electrolyte decomposition and transition metal dissolution. The inorganic components generated from the decomposition of the lithium salt-based second additive synergistically optimize the ionic conductivity and mechanical strength of the positive and negative electrode interface film. The combination of these two additives and the solvent system achieves precise reinforcement of interface protection. Furthermore, the lanthanum doping in the positive electrode active material stabilizes the crystal structure, inhibiting lattice oxygen loss and structural collapse. Carbon nanotubes form a three-dimensional conductive and thermally conductive network, promoting heat diffusion and electron transport. The lanthanum doping in the active material, along with carbon nanotubes, works synergistically with the positive and negative electrode active materials to simultaneously ensure battery stability and high and low temperature cycling performance. Furthermore, preliminary experiments have verified that when the mass percentages of the first solvent in the electrolyte (A%), the second solvent (B%), the first additive (C%), the second additive (D%), the carbon nanotubes in the positive electrode active layer (H%), the lanthanum content in the positive electrode active material (X%), and the specific surface area W of the negative electrode active material satisfy the following relationships: 1.23 ≤ (A+C+D)*10000 / X ≤ 21, 0.05 ≤ (C+D)*100 / (B+W) ≤ 3.16, and 3.23 ≤ (C+H) / B ≤ 97.30, the lithium-ion battery can simultaneously achieve excellent low-temperature cycling performance, high-temperature cycling stability, and thermal shock safety.

[0066] Specifically, the 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.

[0067] The present invention will be further illustrated by the following examples.

[0068] Table 1 Continued from Table 1 Continued from Table 1 Table 2 Continued from Table 2 Continued from Table 2 Example 1 This example illustrates the lithium-ion battery disclosed in this invention. The preparation of the lithium-ion battery includes the following steps: Preparation of the positive electrode The positive electrode current collector is a 12μm thick aluminum foil, and the positive electrode active material (LiNi) is... 0.8 Co 0.1 Mn 0.1 O2, prepared by co-precipitation-sintering process, with lanthanum doping content of 400ppm, conductive agent acetylene black (Super P), carbon nanotubes (CNTs) and binder polyvinylidene fluoride (PVDF) are mixed at a mass ratio (active material):(Super P):(CNT):(PVDF)=94.0:2.0:2.0:2.0, wherein the mass percentage of CNTs in the positive electrode active layer is 2%; the above substances are then thoroughly mixed with N-methyl-2-pyrrolidone (NMP) solvent in a vacuum planetary mixer until a uniform positive electrode slurry with suitable viscosity is formed. The positive electrode slurry is uniformly coated on both sides of an aluminum foil current collector, dried at 120℃, and rolled and punched to obtain the positive electrode.

[0069] The negative electrode is prepared by using an 8μm thick copper foil as the current collector, and then layering artificial graphite (with a specific surface area W of 6m²) onto it. 2 The following ingredients are mixed in a mass ratio of 96.0:1.0:1.5:1.5:deionized water is added as a solvent and stirred to prepare a uniform negative electrode slurry. The slurry is then coated on both sides of a copper foil, dried, cold-pressed, and die-cut to obtain the negative electrode.

[0070] The electrolyte was prepared in a glove box filled with argon gas, where the water and oxygen content were both below 0.1 ppm. First, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a mass ratio of 3:7 to form a basic solvent system. Lithium salt LiPF6 was then added to this basic solvent to achieve a concentration of 1.0%. The solution was stirred until completely dissolved to obtain the basic electrolyte. Then, the first solvent compound a-1 (dimethylaminosulfonyl fluoride), the second solvent compound b-1 (methyltrifluoroethyl carbonate), the first additive mannitol carbonate sulfate (CBS), and the second additive lithium difluoroimide (LiFSI) were added to the basic electrolyte in sequence. By precise weighing, the mass percentages of the above four components in the final electrolyte were A=5%, B=15%, C=2%, and D=1%, respectively. After all components were added, they were stirred and mixed thoroughly to obtain the final electrolyte. The content of each component in the electrolyte was determined by qualitative and quantitative analysis of the prepared electrolyte using gas chromatography-mass spectrometry (GC-MS) to confirm the mass percentage content of each solvent and additive.

[0071] The preparation of lithium-ion batteries involves stacking the prepared positive electrode, negative electrode, and separator in sequence, with the separator positioned between the positive and negative electrodes. The bare cell is then produced through processes such as winding, welding tabs, inserting into an aluminum-plastic film shell, and baking and dehumidifying. The prepared electrolyte is then injected into a glove box, and after standard processes such as vacuum sealing, standing, pre-charging, formation, and aging, a lithium-ion soft-pack battery with a rated capacity of 5Ah is obtained.

[0072] Examples 2-51 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: in Examples 2-51, the mass percentage of the first solvent is A%, the type of the first solvent is B%, the type of the second solvent is C%, the mass percentage of the first additive is D%, the type of the second additive is H%, the mass percentage of carbon nanotubes is H / %, the content of lanthanum in the positive electrode active material is X / ppm, and the specific surface area of ​​the negative electrode active material is Wm². 2 / g, (A+C+D)*10000 / X, (C+D)*100 / (B+W), and (C+H) / B are all recorded in Table 1 or Table 2.

[0073] Comparative Examples 1-56 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: in Comparative Examples 1-56, the mass percentage of the first solvent is A%, the type of the first solvent is B%, the type of the second solvent is C%, the mass percentage of the first additive is D%, the type of the second additive is H%, the mass percentage of carbon nanotubes is H / %, the content of lanthanum in the positive electrode active material is X / ppm, and the specific surface area of ​​the negative electrode active material is Wm². 2 / g, (A+C+D)*10000 / X, (C+D)*100 / (B+W) and (C+H) / B are all recorded in Table 1 and Table 2.

[0074] The performance tests were conducted on Examples 1-51 and Comparative Examples 1-56 prepared above as follows: Thermal shock test: The lithium-ion batteries prepared in the above examples and comparative examples were charged at 25°C at a rate of 1C to the cutoff voltage and the cutoff current was 0.025C. They were then transferred to an oven and heated to 150°C at a rate of 5°C / min and kept constant for 60 minutes. The batteries were considered to have passed the test if they did not catch fire or explode. The number of cells tested was 20.

[0075] The lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to charge-discharge cycles at 45°C within the charge-discharge cutoff voltage range at a rate of 1C / 1C. The discharge capacity of the first cycle was recorded as C1, and the discharge capacity of the Nth cycle was recorded as C2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R2 = C2 / C1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate R2 was 80% was recorded.

[0076] The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 0°C within the charge and discharge cutoff voltage range at a rate of 1C / 1C. The discharge capacity of the first cycle was recorded as Y1, and the discharge capacity of the Nth cycle was recorded as Y2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate X2 = Y2 / Y1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate X2 was 80% was recorded.

[0077] The test results are entered into Table 3.

[0078] Table 3 Continued from Table 3 Continued from Table 3 As can be seen from the test results in Table 3, among the overall test results of thermal shock, 0°C and 45°C cycle performance of Examples 1-51 and Comparative Examples 1-56 of this application, the test results of Examples 1-51 are significantly better than those of Comparative Examples 1-56. Examples 1-51 all meet the limitations of component selection, parameter range and relationship formula of this application, and have superior comprehensive performance compared with the comparative examples.

[0079] Specifically, in Examples 1-5, the mass percentage A% of the first solvent increased from 5% to 30%, and the corresponding test data were 16 to 11 particles passing through the thermal shock, 575 to 577 cycles at 0°C, and 533 to 523 cycles at 45°C. It is speculated that the reason is that the first solvent is a fluoroamide solvent with high dielectric constant and high thermal stability, which can form a stable negative electrode SEI film to improve high voltage / thermal stability. However, excessive amount will increase the viscosity of the electrolyte. When A% increases from 5% to 30%, the stability of the negative electrode SEI film first improves, but then the ion conduction is blocked due to the increase in viscosity. Therefore, the thermal shock pass rate decreases slightly, the low temperature cycle is basically stable, and the high temperature cycle slowly decays. If Example 3 (A=15%) is the middle value, the viscosity and stability are optimally balanced, and the 45°C cycle reaches 602 cycles, which is the best overall performance among Examples 1-5.

[0080] In Examples 6-10, the mass percentage of the second solvent, B%, increased from 5% to 30%. The test data were 16 to 12 particles passing through the thermal shock, 578 to 645 cycles at 0°C, and 609 to 527 cycles at 45°C. The reason for this is that the second solvent is a fluorinated linear carbonate solvent. Low viscosity is the core of low-temperature ion conduction, but its linear ester bond has poor thermal stability. As B% increases from 5% to 30%, the resistance to low-temperature ion transport continues to decrease, and the number of cycles at 0°C increases significantly. However, an excessively high B% will lead to a decrease in the overall thermal stability of the electrolyte, and the thermal shock pass rate and 45°C cycle life will continue to decline. For example, Example 6 (B=5%) has the best thermal stability and reaches 609 cycles at 45°C, which is the best among Examples 6-10.

[0081] In Examples 11-15, the mass percentage (C%) of the first additive increased from 0.5% to 4%. The test data were 13 to 17 particles passing the thermal shock test, 633 to 564 cycles at 0°C, and 556 to 553 cycles at 45°C. This is because the first additive, mannitol carbonate sulfate, preferentially forms a dense CEI film at the positive electrode, inhibiting electrolyte decomposition and transition metal dissolution, thus improving thermal safety. However, excessive amounts can lead to excessively high CEI film impedance. As C% increased from 0.5% to 4%, the protective capability of the positive electrode CEI film continued to improve, and the thermal shock pass rate significantly increased. However, the film impedance increased with increasing content, hindering ion transport and causing a continuous decrease in the number of cycles at 0°C. For example, Example 15 (C=4%) showed the best thermal safety, with 17 particles passing the thermal shock test, and the overall performance was the best among Examples 11-15.

[0082] In Examples 16-20, the mass percentage (D%) of the second additive increased from 0.3% to 3%. The test data were 13 to 15 particles passing through the thermal shock, 593 to 587 cycles at 0°C, and 580 to 546 cycles at 45°C. The reason for this is that the second additive is a lithium salt additive, which decomposes to produce LiF / Li3PO4, which optimizes the ionic conductivity and mechanical strength of the positive and negative electrode interface film. A small amount can play a synergistic role, while an excessive amount will increase the viscosity of the electrolyte. When D% increases from 0.3% to 3%, the interface film performance is first optimized and then damaged due to the increased viscosity. Therefore, the thermal shock pass rate increases slightly, and the high and low temperature cycling slowly declines. For example, Example 17 (D=0.5%) is an intermediate value, with the optimal balance between interface and kinetics, and 613 cycles at 0°C.

[0083] In Examples 26-30, the lanthanum X content varied in a gradient (100ppm→800ppm). The test data were 13 to 16 particles passing the thermal shock test, 593 to 554 cycles at 0℃, and 541 to 520 cycles at 45℃. The reason for this is that lanthanum stabilizes the cathode lattice structure through the pillar effect, inhibiting oxygen loss and structural collapse. Excessive lanthanum will introduce lattice defects and reduce the lithium-ion diffusion coefficient. As X increases from 100ppm to 800ppm, the cathode bulk phase stability first improves and then is damaged due to the increase in defects. Therefore, the thermal shock pass rate increases slightly and the high and low temperature cycling rate decreases slowly. Example 27 (X=200ppm) is an intermediate value, with the optimal balance between bulk phase stability and diffusion coefficient, and 610 cycles at 0℃.

[0084] In Examples 36-45, the solvents or additives used were other specific types as defined in this application. According to the corresponding test data, the number of particles passing the thermal shock test was 14, the cycle time was 619-624 cycles at 0°C, and the cycle time was 600-605 cycles at 45°C. Compared with other examples, there was no significant difference in performance, which shows that the solvents or additives defined in this application can effectively play their corresponding roles, and thus the performance remains stable and balanced.

[0085] Example 46: (A+C+D)×10000 / X=1.23 (lower limit). The total amount of interface protection component is too low, resulting in insufficient phase stability matching with the lanthanum dopant and weak side reaction suppression effect. Therefore, the cycling performance at 0℃ is 532 cycles and at 45℃ is 482 cycles, which is a relatively low level in the examples. Example 47: (A+C+D)×10000 / X=21.00 (upper limit). The interface protection component is excessive, resulting in an overly thick interface film that increases resistance, and insufficient phase stability support for the cathode. Therefore, the cycling performance at 0℃ is 521 cycles and at 45℃ is 484 cycles, which is a relatively low level in the examples. Example 48: (C+D)×100 / (B+W)=0.05 (lower limit). The total amount of film-forming additive is too low, resulting in a relatively low level in the high B+W... In the high-kinetic system, the interface protection failed, so only 8 particles passed the thermal shock test, which is worse than other examples. In Example 49, (C+D)×100 / (B+W)=3.16 (upper limit), the film-forming additive was excessive, and the interface film impedance was too high, which hindered ion transport. Therefore, the performance was worse than other examples, with 515 cycles at 0°C and 464 cycles at 45°C. In Example 50, (C+H) / B=3.23 (lower limit), the thermally stable component (C+H) was too low, which could not effectively restrict the thermal decomposition of B. Therefore, the thermal stability decreased slightly after 464 cycles at 45°C. In Example 51, (C+H) / B=97.30 (upper limit), the thermally stable component was excessive, the carbon nanotubes blocked the pores and the viscosity of the fluoroamide increased, which hindered ion transport. Therefore, the performance was the lowest among the examples, with 514 cycles at 0°C and 460 cycles at 45°C.

[0086] Furthermore, in the comparative examples, Comparative Examples 2, 7, 9-10, and 21-23 lacked the first solvent, thus failing to form a stable negative electrode SEI film. Under high temperatures, the SEI film repeatedly ruptured / regenerated, the electrolyte decomposed in large quantities, and the number of thermal shocks passed was 0-8. The cycle time at 45℃ was ≤361 cycles.

[0087] Comparative Examples 2, 8-9, 21-23, and 28 lacked a second solvent, resulting in a dramatic increase in electrolyte viscosity, uncontrolled ion transport resistance at 0°C, complete failure of low-temperature kinetics, and a cycle life of ≤434 cycles at 0°C.

[0088] Comparative Examples 1, 4-5, 7, and 24 lacked the first and second additives, and had no effective CEI / SEI film protection at the positive and negative electrodes. The electrolyte and electrodes directly underwent side reactions, resulting in severe exothermic reactions under thermal shock and significant lithium loss during cycling. The number of thermal shock passes was 1-9, and the cycle life was ≤421 cycles.

[0089] Comparative Examples 11, 20, 26, and 31 lacked carbon nanotubes (H), resulting in no thermally conductive network at the positive electrode. Under thermal shock, local heat could not be dissipated, significantly increasing the risk of thermal runaway. Furthermore, the resistance to electron transport increased, with 5-8 nanotubes passing through the thermal shock and ≤397 cycles at 45°C.

[0090] Comparative Examples 3, 13, and 18 lacked lanthanum element X, resulting in no pillar effect in the cathode lattice. Oxygen was lost and the structure collapsed at high temperatures, leading to a sharp decline in cycling performance at 45°C, with a cycle life of ≤302 cycles at 45°C.

[0091] In Comparative Examples 32-45, the content of a single component (A / B / C / D / H / X / W) exceeded the limits specified in this application. The content of a single component was below the lower limit (e.g., A=1%, C=0.1%) or above the upper limit (e.g., A=40%, C=8%), leading to insufficient performance of the core functional mechanism or increased negative reactions, which is also detrimental to the optimization of overall performance. Specifically, in Comparative Example 32, when A=1%, the SEI film stability was insufficient; it passed thermal shock testing on 17 samples but only 383 cycles at 45°C. In Comparative Example 33, when A=40%, the electrolyte viscosity was too high; it only circulated at 0°C for 422 cycles and only 6 samples passed thermal shock testing. In Comparative Example 34, when B=1%, low-temperature kinetics failed; it only circulated at 0°C for 447 cycles but passed thermal shock testing on 17 samples. In Comparative Example 35, when B=40%, thermal stability dropped sharply; it circulated at 0°C for 684 cycles but only 4 samples passed thermal shock testing. In Comparative Example 36, with C=0.1%, the CEI membrane provided insufficient protection, with only 7 particles passing the thermal shock test, but achieving 638 cycles at 0℃. In Comparative Example 37, with C=8%, the CEI membrane impedance was too high, with 17 particles passing the thermal shock test, but only 323 / 284 cycles at 0℃ / 45℃. In Comparative Example 38, with D=0.05%, the interface optimization effect was weak, with only 7 particles passing the thermal shock test. In Comparative Example 39, with D=4%, the electrolyte viscosity increased, resulting in interface inhomogeneity, with 16 particles passing the thermal shock test, but... The thermal shock cycle at 45℃ lasted only 329 cycles; in Comparative Example 40, with H=0.1%, a thermally conductive network could not be formed, and only 7 particles passed through the thermal shock; in Comparative Example 41, with H=8%, the electrode pores were blocked, and 17 particles passed through the thermal shock, but the cycle at 0℃ lasted only 354 cycles; in Comparative Example 42, with X=50ppm, bulk stability failed, and only 4 particles passed through the thermal shock; in Comparative Example 43, with X=1000ppm, lattice defects were introduced, and the cycle at 0℃ lasted only 315 cycles; in Comparative Example 44, with W=0.1m... 2 At / g, the reaction sites were insufficient, and the cycle at 0℃ was only 327 times; in Comparative Example 45, W=50m 2 At / g, the side reaction interface increases dramatically, and thermal shock only passes through 1 particle, resulting in poor thermal safety.

[0092] Comparative Examples 46-50 replaced the first solvent, second solvent, first additive, second additive, and carbon nanotubes as defined in this application with other substances (the first solvent was changed to PC, the second solvent to FEC, the first additive to PS, the second additive to DTD, and CNTs to ceramics). Specifically, in Comparative Example 46, after changing the first solvent to PC, a stable SEI film could not be formed, resulting in poor high-temperature oxidation stability; only 10 nanotubes passed the thermal shock test, and the cycle life at 45°C was only 356 cycles. In Comparative Example 47, after changing the second solvent to FEC, the viscosity increased, low-temperature ion conduction was hindered, and the cycle life at 0°C was only 442 cycles. In Comparative Example 48, after changing the first additive to P, a dense CEI film could not be formed, electrolyte decomposition and metal dissolution could not be suppressed, and only 6 nanotubes passed the thermal shock test. In Comparative Example 49, after changing the second additive to DTD, it could not decompose to produce LiF / Li3PO4, the interface film optimization failed, and only 6 nanotubes passed the thermal shock test. In Comparative Example 50, after changing CNTs to ceramics, a three-dimensional thermally / conductively conductive network could not be formed, heat dissipation and electron transport were hindered, and only 10 nanotubes passed the thermal shock test, with a cycle life of ≤410 cycles.

[0093] For Comparative Example 51, 0.73(A+C+D)×10000 / X=0.73; for Comparative Example 52, 0.73(A+C+D)×10000 / X=37.00. Therefore, neither Comparative Example 51 nor Comparative Example 52 meets the requirement of 1.23≤(A+C+D)*10000 / X≤21 as specified in this application. The corresponding test results show that Comparative Example 51 has insufficient interface protection, cycling at 45℃ for only 392 cycles, while Comparative Example 52 has excessive interface protection, cycling at 0℃ for only 428 cycles and passing only 6 thermal shock tests. For Comparative Example 53, (C+D)×100 / (B+W)=0.03; for Comparative Example 54, (C+D)×100 / (B+W)=6.67. Therefore, neither Comparative Example 53 nor Comparative Example 54 meets the requirement of 1.23≤(A+C+D)*10000 / X≤21 as specified in this application. The test results show that Comparative Example 53 had insufficient film-forming agent, resulting in interface protection failure and only 6 particles passing the thermal shock test. Comparative Example 54 had excessive film-forming agent, resulting in excessively high film impedance and only 393 cycles at 0℃. Comparative Example 55 had (C+H) / B=1.68, and Comparative Example 56 had (C+H) / B=120.80. Both Comparative Examples 55 and 56 do not meet the requirement of 3.23≤(C+H) / B≤97.30 specified in this application. Therefore, Comparative Example 55 had insufficient thermally stabilizing components, failing to control the thermal decomposition of the second solvent, and only 6 particles passed the thermal shock test. Comparative Example 56 had excessive thermally stabilizing components, hindering ion transport and only 392 cycles at 0℃.

[0094] 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 lithium-ion battery, characterized in that, The battery comprises a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode active layer comprising a negative electrode active material. The positive electrode includes a positive electrode active layer comprising carbon nanotubes and a positive electrode active material, wherein the positive electrode active material is doped with lanthanum. The electrolyte comprises a solvent, additives, and an electrolyte salt. The solvent comprises a first solvent and a second solvent. The additives comprise a first additive and a second additive. The first solvent comprises a fluoroamide solvent, and the second solvent comprises a fluorolinear carbonate solvent. The first additive comprises mannitol sulfate, and the second additive comprises a lithium salt additive. The lithium-ion battery satisfies the following condition: 1.23 ≤ (A+C+D)*10000 / X ≤ 21; 0 0.05≤(C+D)*100 / (B+W)≤3.16; 3.23≤(C+H) / B≤97.30; and, 5≤A≤30, 5≤B≤30, 0.5≤C≤4, 0.3≤D≤3, 0.5≤H≤6, 100≤X≤800, 1≤W≤30; where A% is the mass percentage of the first solvent in the electrolyte; B% is the mass percentage of the second solvent in the electrolyte; C% is the mass percentage of the first additive in the electrolyte; D% is the mass percentage of the second additive in the electrolyte; H% is the mass percentage of carbon nanotubes in the positive electrode active layer; X is the content of lanthanum in the positive electrode active material, in ppm; W is the specific surface area of ​​the negative electrode active material, in m². 2 / g.

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies the following condition: 2.00≤(A+C+D)*10000 / X≤18.

00.

3. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies the following condition: 0.10≤(C+D)*100 / (B+W)≤2.

61.

4. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery meets the following condition: 3.47≤(C+H) / B≤40.

40.

5. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies one of the following conditions: (1) 10≤A≤25; (2) 10≤B≤25; (3) 1≤C≤3; (4) 0.5≤D≤2; (5) 1≤H≤5; (6) 200≤X≤600; (7) 4≤W≤20.

6. The lithium-ion battery according to claim 1, characterized in that, The first solvent includes one or more of dimethylaminosulfonyl fluoride, 1,1,1-trifluoro-N,N-dimethylformamide, and N,N-diethylaminosulfonyl fluoride; and / or, the second solvent includes one or more of methyltrifluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate, ethyl (2,2,2-trifluoroethyl) carbonate, and di(monofluoromethyl) carbonate.

7. The lithium-ion battery according to claim 1, characterized in that, The electrolyte salt includes one or more of lithium difluoroimide, lithium bis(trifluoroimide), lithium dioxaborate, lithium difluorophosphate, lithium difluorooxaborate, and lithium tetrafluoroborate.

8. The lithium-ion battery according to claim 1, characterized in that, The positive electrode active material includes a transition metal lithium oxide; 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; where M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

9. The lithium-ion battery according to claim 1, characterized in that, The negative electrode active material includes one or more of graphite, silicon-carbon composite materials, and lithium metal materials.

10. An electrical device, characterized in that, The lithium-ion battery includes any one of claims 1 to 9.

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