Lithium ion battery

Abstract

The lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, the electrolyte comprises an organic solvent, a lithium salt and an additive, and a positive electrode active material in the positive electrode comprises a ternary positive electrode material; the organic solvent comprises propylene carbonate, ethyl methyl carbonate and ethyl acetate, the volume ratio of the ethyl methyl carbonate is V1%, and the volume ratio of the ethyl acetate is V2%; the additive comprises 1, 3-propene sultone and acesulfamic acid lithium, the content of the 1, 3-propene sultone is a%, and the content of the acesulfamic acid lithium is b%; a negative electrode active substance in the negative electrode comprises graphite and a silicon-based material, and the surface density of the negative electrode is A mg / cm < 2 >; the electrolyte and the negative electrode meet the following conditions: 0 lt; and V1 / 5 + 0.8 * V2-3a-0.5 b-A-29 is less than or equal to 13.25. The lithium ion battery provided by the invention can give consideration to both high energy density and good power performance.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a lithium-ion battery. Background Technology

[0002] Electric vertical takeoff and landing (eVTOL) aircraft, with their quiet, efficient, and flexible characteristics, offer a new possibility for solving urban traffic congestion. Helicopters can generate noise levels exceeding 85 decibels, often causing people to cover their ears when they fly by. Electric flying cars, through small-diameter propellers and optimized aerodynamic design, reduce noise levels to near those of ordinary road vehicles. Furthermore, compared to the high operating costs of aircraft, electric flying cars are electrically powered, have a simpler structure, and are easier to maintain, significantly reducing operating costs. In the future, riding in electric flying cars is expected to become widespread, allowing them to take off and land flexibly on rooftops, parking lots, and even small airports, truly integrating into urban spaces.

[0003] However, compared to electric vehicles, eVTOL operates in far more extreme flight scenarios: the discharge rate during vertical takeoff and landing reaches 4C-6C (far exceeding the 0.1-1C of electric vehicles), placing higher demands on the electrochemical system of lithium-ion batteries, especially the electrolyte. Furthermore, eVTOL flight scenarios are more complex, involving maneuvering through skyscrapers while simultaneously requiring higher power performance during takeoff and landing, particularly when carrying passengers or cargo, to meet operational demands. At the same time, safety issues arising from high gas production in the battery must be avoided.

[0004] Therefore, how to balance high energy density, high power performance, and low gas production is a pressing problem to be solved in the development of lithium-ion batteries. Summary of the Invention

[0005] In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a lithium-ion battery.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte comprises an organic solvent, a lithium salt, and an additive, and the positive electrode active material in the positive electrode comprises a ternary positive electrode material.

[0008] The organic solvent in the electrolyte includes propylene carbonate, ethyl methyl carbonate, and ethyl acetate, wherein the volume percentage of ethyl methyl carbonate in the organic solvent is V1%, and the volume percentage of ethyl acetate in the organic solvent is V2%.

[0009] The additives in the electrolyte include fluoroethylene carbonate, 1,3 - propylene sultone, and lithium saccharin. The mass percentage of 1,3 - propylene sultone in the electrolyte is a %, and the mass percentage of lithium saccharin in the electrolyte is b %;

[0010] The negative electrode active material in the negative electrode includes graphite and a silicon - based material. The areal density of the negative electrode (referring to the mass of the negative electrode material layer loaded per unit area on one side surface of the negative electrode current collector) is A mg / cm 2 ;

[0011] The electrolyte and the negative electrode satisfy the following relationship: 0 < V1 / 5 + 0.8×V2 - 3a - 0.5b - A - 29 ≤ 13.25, 0 < V1 ≤ 80, 0 < V2 ≤ 80, 0.3 ≤ a ≤ 2, b > 0.

[0012] In the present invention, V1 / 5 + 0.8×V2 - 3a - 0.5a - A - 29 is obtained by calculation, and the values can be 0.01, 0.03, 0.05, 0.08, 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, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13 or 13.25, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0013] In the present invention, 0 < V1 < 80, for example, it can be 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] In the present invention, 0 < V2 ≤ 80, for example, it can be 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] In the present invention, 0.3 ≤ a ≤ 2, for example, it can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] In this invention, b > 0, and can be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, or 3.5, etc. However, it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] For the lithium-ion battery eVTOL system, in order to pursue higher endurance, ternary cathode materials (such as nickel cobalt manganese layered oxides and / or nickel cobalt aluminum layered oxides) and silicon-doped graphite systems are used. By taking advantage of the higher voltage platform and capacity of ternary cathode materials as well as the higher capacity and good stability of silicon-doped graphite systems, the energy density is improved. In ternary cathode materials, nickel has a relatively high redox potential and a large capacity contribution. However, nickel is prone to lithium-nickel mixing, and Ni catalyzes the oxidation of electrolyte solvents, resulting in a decrease in the stability of the cathode interface and an increase in side reactions, thus causing capacity loss. Especially for high-nickel ternary cathode materials (nickel molar content ≥ 80%), the above problems are more serious, which will lead to deterioration of the cycle performance and storage performance of lithium-ion batteries, and the impact is more serious under high-temperature (such as above 40 °C) conditions and high-rate discharge conditions. To address this problem, the present invention strictly limits the components of organic solvents and additives in the electrolyte, and limits the electrolyte and the negative electrode to satisfy the relationship: 0 < V1 / 5 + 0.8×V2 - 3a - 0.5b - A - 29 ≤ 13.25, so that the lithium-ion battery can balance high energy density and high power performance, and has excellent normal-temperature cycle performance and high-temperature cycle performance under high-rate conditions. At the same time, it has good high-temperature storage performance, low gas generation, and good safety performance. The technical principle is as follows: First, in the design of the solvent system of the electrolyte, propylene carbonate (PC) has a relatively high dielectric constant, which can effectively dissociate lithium salts, enabling the separation of cation-anion pairs of lithium salts at a relatively high concentration. However, its viscosity is relatively large. By using it in combination with ethyl methyl carbonate (EMC) and ethyl acetate (EA), the viscosity of the solvent can be reduced, effectively improving ion mobility and increasing conductivity. Second, in the design of the additive system of the electrolyte, 1,3-propylene sultone is a cyclic sulfonate with relatively high reactivity (such as improving cycle stability or forming a more stable solid electrolyte interface film), and can generate a stable SEI interface film rich in substances such as Li2SO3 and Li2SO4, which can reduce side reactions of the electrolyte at the positive and negative electrode interfaces, reduce gas generation, and improve cycle stability under high-temperature storage and high-rate conditions; the sulfamic acid group in lithium sulfamate can react with the exposed positive and negative electrode materials after the existing solid electrolyte films at the positive and negative electrodes are damaged in the later stage of cycling and storage, repairing the original protective layer, playing a role in extending the cycle and storage of the battery cell, and can also participate in the formation of an inorganic CEI film containing S and N, which has the characteristics of rich lithium, low impedance, and high ion diffusion coefficient, can effectively protect the ternary cathode interface structure, facilitate ion transport and inhibit the growth of DCR, and contribute to improving the power performance of the battery cell and reducing temperature rise. Fluoroethylene carbonate can act synergistically with other additives to significantly improve the performance of the battery, especially improving the quality of the SEI film and the cycle stability of the silicon-doped graphite negative electrode.As can be seen from above, 1,3 - propylene sulfonic acid lactone, lithium saccharin, and fluoroethylene carbonate can form a stable and dense SEI film and an inorganic CEI film rich in lithium, with low impedance and high ion diffusion coefficient through synergistic cooperation. The interface regulation effect is good, reducing the catalytic oxidation of the electrolyte solvent by the positive electrode, reducing gas generation, and being beneficial to improving the performance of the battery. It should be noted that since the negative electrode uses a graphite - doped silicon negative electrode, and the silicon - based material in it has a large volume expansion. Therefore, the surface density design of the negative electrode active layer and the organic solvents and additives in the electrolyte should satisfy the relational expression: 0 < V1 / 5 + 0.8×V2 - 3a - 0.5b - A - 29 ≤ 13.25, so as to ensure the high - capacity performance of the ternary positive electrode material and the graphite - doped silicon negative electrode while taking into account good power performance. The cycle performance of the battery during high - rate discharge is effectively improved, and the gas generation under high - temperature storage conditions decreases.

[0018] Preferably, 20 ≤ V1 ≤ 50. For example, it can be 20, 22, 25, 27, 30, 33, 35, 37, 40, 42, 45, 48, or 50, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0019] Preferably, 30 ≤ V2 ≤ 60. For example, it can be 30, 32, 34, 36, 38, 40, 43, 45, 46, 48, 50, 52, 55, 57, or 60, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0020] Preferably, 0.3 ≤ b ≤ 2. For example, it can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2, etc. But not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0021] Preferably, 7 ≤ A ≤ 9. For example, it can be 7, 7.2, 7.3, 7.5, 7.7, 7.8, 8, 8.2, 8.5, 8.6, 8.8, or 9, etc. But not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0022] As a preferred embodiment of the lithium-ion battery of the present invention, with the total mass of the negative electrode active layer as 100%, the mass percentage of graphite is 70% to 80%, for example, it can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The mass percentage of silicon-based material is 20% to 25%, for example, it can be 20%, 21%, 22%, 23%, 24%, or 25%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] Preferably, the lithium salt comprises LiPF6.

[0024] Preferably, the concentration of LiPF6 in the electrolyte is 1 mol / L to 2 mol / L, for example, it can be 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2 mol / L, etc. However, it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] As a preferred embodiment of the lithium-ion battery of the present invention, the fluoroethylene carbonate in the electrolyte has a mass percentage of 6% to 12%, for example, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, or 12%, etc. However, it is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] Preferably, the negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer includes the negative electrode active material.

[0028] Preferably, the negative electrode material layer further includes at least one of a first conductive agent and a first binder.

[0029] Preferably, the positive electrode includes a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active layer includes the positive electrode active material.

[0030] Preferably, the ternary cathode material comprises nickel-cobalt-manganese base oxide and / or nickel-cobalt-aluminum base oxide.

[0031] Preferably, the positive electrode active layer further includes at least one of a second conductive agent and a second binder.

[0032] The present invention does not specifically limit the preparation method of the lithium-ion battery. Those skilled in the art can prepare it according to the methods disclosed in the prior art. Exemplarily, the preparation method of the lithium-ion battery includes the following steps:

[0033] Prepare the positive electrode sheet, negative electrode sheet and electrolyte respectively;

[0034] Make the positive electrode sheet, separator and negative electrode sheet into an electrode core in a winding or laminating manner. The separator in the electrode core is located between the positive electrode sheet and the negative electrode sheet to prevent short circuit caused by contact between the positive and negative electrodes. Inject the electrolyte into the electrode core and package it to obtain the lithium-ion battery.

[0035] In one embodiment, the preparation method of the negative electrode sheet includes: uniformly mixing the negative electrode active material, optional first conductive agent, optional first binder and solvent to obtain a negative electrode slurry, and coating the negative electrode slurry on at least one side surface of the negative electrode current collector and drying to obtain the negative electrode sheet.

[0036] In one embodiment, the preparation method of the positive electrode sheet includes: uniformly mixing the positive electrode active material, optional second conductive agent, optional second binder and solvent to obtain a positive electrode slurry, and coating the positive electrode slurry on at least one side surface of the positive electrode current collector and drying to obtain the positive electrode sheet.

[0037] In one embodiment, the preparation method of the electrolyte includes: adding the formulated amount of lithium salt and additives to an organic solvent and mixing uniformly to obtain the electrolyte.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The lithium-ion battery of the present invention uses a ternary positive electrode material and a graphite doped with silicon system. By strictly limiting the components of the organic solvent and additives in the electrolyte and limiting that the electrolyte and the negative electrode satisfy the relationship: 0<V1 / 5 + 0.8×V2 - 3a - 0.5b - A - 29≤13.25, the lithium-ion battery can take into account high energy density and good power performance. Its normal temperature cycle performance and high temperature cycle performance under high rate conditions are greatly improved, it has good high temperature storage performance, reduced gas production, and the impedance of the lithium-ion battery is low. [[ID=2:4]]

[0040] (2) The impedance DCR of the lithium-ion battery of the present invention is below 13.43 mΩ; the retention rate after 500 cycles at normal temperature is below 91.10%, and the retention rate after 500 cycles at high temperature is below 83.77%; the capacity retention rate after storage at 60°C for 2 months is below 92.5%, the capacity recovery rate after storage at 60°C for 2 months is below 94.60%, and the gas production amount during storage at 60°C is below 2.10 mL / Ah. ]>Specific Embodiments

[0041] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0042] The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0043] In this embodiment of the invention, all raw materials in the electrolyte are obtained through purchase. Other raw materials in the lithium-ion battery, unless otherwise specified, are also obtained through purchase.

[0044] Preparation Example 1

[0045] An electrolyte is provided, comprising an organic solvent, a lithium salt, a first additive, and a second additive. The organic solvent includes propylene carbonate (PC), ethyl methyl carbonate (EMC), and ethyl acetate (EA). The lithium salt is LiPF6. The first additive is 1,3-propenesulfonate lactone and lithium acesulfame potassium. The second additive is fluoroethylene carbonate (FEC).

[0046] The composition of the electrolyte is shown in Table 1. All "content" values ​​are by mass percentage, based on the total mass of the electrolyte. The content of 1,3-propenylsulfonate lactone is a%, and the content of lithium acesulfame potassium is b%.

[0047] The above-mentioned method for preparing the electrolyte includes the following steps: PC, EMC, and EA are mixed evenly at a volume ratio of 20:40:40 to obtain an organic solvent. 1.2 mol / L LiPF6, FEC, 1,3-propenesulfonate lactone, and lithium acesulfame potassium are dissolved in the above organic solvent and mixed evenly to obtain the electrolyte.

[0048] Example 1

[0049] This embodiment provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte (Preparation Example 1). The negative electrode includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer includes a negative electrode active material, a conductive agent (Super-P), a thickener (CMC), and a binder (SBR). The negative electrode active material includes artificial graphite and silicon-carbon materials, wherein the mass ratio of artificial graphite, silicon-carbon materials, Super-P, CMC, and SBR is 75:20:2:1:1. The positive electrode includes a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector. The positive electrode active layer includes a positive electrode active material, a conductive agent (Super-P and single-walled carbon nanotubes), and a binder (PVDF). The positive electrode active material includes a ternary positive electrode material (chemical formula LiNi). 0.8 Co 0.1 Mn 0.1 The weight ratio of the positive electrode active material, Super-P, single-walled carbon nanotubes and binder PVDF is 96:1:1:2 (O2).

[0050] The above-mentioned method for preparing lithium-ion batteries includes the following steps:

[0051] Positive electrode preparation: The positive electrode active material, Super-P and binder PVDF are dispersed in the solvent NMP and mixed evenly to form a positive electrode slurry. The positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil. After drying, cold pressing, slitting and cutting, the positive electrode sheet is obtained.

[0052] Negative electrode preparation: The negative electrode active materials, artificial graphite, silicon carbide, Super-P, CMC, and SBR are dissolved in deionized water and mixed evenly to form a negative electrode slurry. The negative electrode slurry is then uniformly coated on both sides of the current collector copper foil, with a coating amount of 8.0 mg / cm² on each side. 2 (That is, the negative electrode surface density A = 8.0 mg / cm³) 2 After drying at 85℃, the material is cold-pressed, trimmed, cut into pieces, and slit. Then, it is dried under vacuum at 110℃ for 4 hours before welding the tabs and negative electrode sheet.

[0053] Fabrication of lithium-ion batteries: The above-mentioned positive electrode, negative electrode, and separator (PE film) are stacked to form a cell with a thickness of 8 mm, a width of 60 mm, and a length of 130 mm. The cell is then vacuum baked at 85°C for 10 h, injected with 12 g of electrolyte (Preparation Example 1), sealed, and left to stand at 45°C for 24 h. After that, pre-charge formation is performed. The pre-charge formation method is as follows: charge at a constant current and constant voltage of 0.1 C to 4.25 V, then discharge at a constant current of 0.1 C to 2.8 V, repeat one charge-discharge cycle, and then charge at 0.1 C to 3.8 V to obtain a lithium-ion battery.

[0054] In this embodiment, the content of 1,3-propenesulfonyl lactone is a%, the content of lithium acesulfame potassium is b%, the volume percentage of EMA in the organic solvent is V1%, and the volume percentage of EA in the organic solvent is V2%. The negative electrode surface density is A mg / cm2. Based on the above data, C is calculated as C = V1 / 5 + 0.8 × V2 - 3a - 0.5bA - 29, and the results are shown in Table 1.

[0055] Examples 2-12 and Comparative Examples 1-3

[0056] The difference from Example 1 is that the composition of the electrolyte and the negative electrode areal density were calculated using the same method as in Example 1, and the results are shown in Table 1.

[0057]

[0058]

[0059] The lithium-ion batteries prepared in Examples 1-12 and Comparative Examples 1-3 were subjected to performance testing. The specific testing methods are as follows:

[0060] Cell capacity calibration: C nominal capacity = 4Ah, charged to 4.25V with constant current and constant voltage at 0.33C, and discharged to 2.8V with constant current at 0.33C. The discharge capacity is taken as the initial cell capacity C0.

[0061] Battery impedance test: At room temperature (25℃), the battery cell was subjected to three 0.33C cycles, followed by constant current and constant voltage charging at 0.33C to 4.25V. The capacity of the last discharge was taken as C1, and 1C' indicates that the battery with capacity C1 was discharged in one hour. The battery was then discharged at 0.33C' for 90 minutes to 50% SOC, allowed to rest for 15 minutes, and then discharged at a constant current of 5C for 10 seconds. The battery impedance is the voltage difference divided by the current during this test. The lower the battery impedance, the better the battery's power performance.

[0062] Room temperature cycle test: In a constant temperature room of 25℃, discharge at a constant current of 4C to 2.8V, let stand for 10 minutes, then charge at a constant current and constant voltage of 1C to 4.25V, let stand for 10 minutes, and repeat this charge and discharge cycle 500 times. The ratio of the discharge capacity after 500 cycles to the initial discharge capacity is taken as the battery's capacity retention rate after 500 cycles at room temperature.

[0063] High-temperature cycle test: In a constant temperature room of 45℃, discharge at a constant current of 4C to 2.8V, let stand for 10 minutes, then charge at a constant current and constant voltage of 1C to 4.25V, let stand for 10 minutes, and repeat this charge and discharge cycle 500 times. The ratio of the discharge capacity after 500 cycles to the initial discharge capacity is used as the 500-cycle capacity retention rate of the cell.

[0064] Storage Test: At 25℃, the battery was discharged at a constant current of 1C to 2.8V, allowed to stand for 10 minutes, and then charged at a constant current and constant voltage of 1C to 4.25V. The battery volume V0 was measured using the water displacement method. The battery was then transferred to a 60℃ oven and stored for 2 months. After storage, the battery was discharged at a constant current of 1C to 2.8V. The ratio of this discharge capacity to the initial capacity is the capacity retention rate after 2 months of storage at 60℃. The battery was charged at a constant current and constant voltage of 1C to 4.25V. The ratio of this charge capacity to the initial capacity is the capacity recovery rate after 2 months of storage at 60℃. The battery volume V1 was measured again using the water displacement method. The gas production at 60℃ was calculated as (V1-V0) / C0, where C0 is the initial capacity.

[0065] The test results are shown in Table 2.

[0066]

[0067] As can be seen from Table 2, the lithium-ion battery of the present invention uses a ternary cathode material and a graphite doped with silicon system. By strictly limiting the components of the organic solvent and additives in the electrolyte, and limiting that the electrolyte and the negative electrode satisfy the relational expression: 0 < V1 / 5 + 0.8×V2 - 3a - 0.5b - A - 29 ≤ 13.25, the lithium-ion battery has good high-temperature (60°C) storage performance, high capacity retention rate and capacity recovery rate during high-temperature storage, and less gas generation. Moreover, the lithium-ion battery has good cycling performance under high-rate (4C) conditions and also has high-rate (5C) power performance. It can meet the usage scenario requirements of high energy density and strong burst for the eVTOL system battery.

[0068] It can be seen from Comparative Example 1 that its C value is negative and does not meet the requirement of the formula 0 < C ≤ 13.25. This is because the content of its high-impedance additive is relatively high, the film-forming impedance is large, R sei is relatively large, and the viscosity of the electrolyte solvent is relatively large, R ohm has a high impedance, its power performance is poor, the DCR reaches 18.30 mΩ, and there is a problem of diving during normal-temperature cycling.

[0069] It can be seen from Comparative Example 2 that the C value is as high as 15.50 and does not meet the requirement of the formula 0 < C ≤ 13.25. Although its power and cycling meet the high-burst requirements, its storage gas generation content is too high at 6.7 mL / Ah. This is because the content of EA is relatively high, its reaction activity at high temperature is high, the α-H is relatively active, and it undergoes reductive decomposition at the negative electrode side, resulting in a serious gas generation problem.

[0070] It can be seen from Comparative Example 3 that its C value is negative and does not meet the requirement of the formula 0 < C ≤ 13.25. Although its high-temperature storage performance is relatively good, this is because too much sulfur-containing SEI generated by 1,3-propylene sulfonate leads to a relatively large film-forming impedance, resulting in a loss of power performance.

[0071] The applicant declares that the present invention uses the above embodiments to illustrate the detailed method of the present invention, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A lithium ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, the electrolyte comprising an organic solvent, a lithium salt, and an additive, characterized in that, The positive electrode active material in the positive electrode comprises a ternary positive electrode material; The organic solvent in the electrolyte comprises propylene carbonate, methyl ethyl carbonate and ethyl acetate, the volume percentage of the methyl ethyl carbonate in the organic solvent is V1%, and the volume percentage of the ethyl acetate in the organic solvent is V2%; The additive in the electrolyte comprises fluoroethylene carbonate, 1,3-propylene sulfite and lithium acetylsulfamate, the mass percentage of the 1,3-propylene sulfite in the electrolyte is a%, and the mass percentage of the lithium acetylsulfamate in the electrolyte is b%; The negative electrode active material in the negative electrode includes graphite and a silicon-based material, and the areal density of the negative electrode is A mg / cm 2 ; The electrolyte and the negative electrode satisfy the following relationship: 0 < V1 / 5 + 0.8 × V2 - 3a - 0.5b - A - 29 ≤ 13.25, 0 < V1 ≤ 80, 0 < V2 ≤ 80, 0.3 ≤ a ≤ 2, and b > 0.

2. The lithium-ion battery of claim 1, wherein, 20≤V1≤50。 3. The lithium-ion battery according to claim 1 or 2, characterized in that 30≤V2≤60。 4. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, 0.3≤b≤2。 5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, 7≤A≤9。 6. The lithium-ion battery according to any one of claims 1 to 5, characterized in that, The mass percentage of the graphite is 70% to 80% and the mass percentage of the silicon-based material is 20% to 25% based on the total mass of the negative electrode active layer being 100%.

7. The lithium-ion battery according to any one of claims 1 to 6, characterized in that, The lithium salt comprises LiPF6; Preferably, the concentration of LiPF6 in the electrolyte is 1 mol / L to 2 mol / L.

8. The lithium-ion battery according to any one of claims 1 to 7, characterized in that, The mass percentage of the fluoroethylene carbonate in the electrolyte is 6% to 12%.

9. The lithium-ion battery according to any one of claims 1 to 8, characterized in that, The negative electrode comprises a negative electrode current collector and a negative electrode material layer arranged on at least one side of the negative electrode current collector, and the negative electrode active material is included in the negative electrode material layer. Preferably, at least one of a first conductive agent and a first binder is further included in the negative electrode material layer.

10. The lithium-ion battery of any one of claims 1-9, wherein, The positive electrode comprises a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, and the positive electrode active material is included in the positive electrode active layer. Preferably, the ternary positive electrode material comprises a nickel-cobalt-manganese-based layered oxide and / or a nickel-cobalt-aluminum-based layered oxide. Preferably, at least one of a second conductive agent and a second binder is further included in the positive electrode active layer.

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