A lithium-ion battery

Abstract

The present application relates to the field of battery, specifically relates to a kind of lithium ion battery, including negative pole piece, positive pole piece, negative pole piece includes negative pole current collector and is located the negative pole active coating of at least one side surface of negative pole current collector;Positive pole piece includes positive pole current collector and is located the positive pole active coating of at least one side surface of positive pole current collector;Negative pole piece includes overhang region, refers to the non-overlapping area corresponding to the part of negative pole piece of the projection of negative pole active coating and positive pole active coating along the thickness direction of negative pole piece, the area percentage value of overhang region in total area of negative pole piece is recorded as A;Negative pole active coating includes negative pole active material, and negative pole active material includes hard carbon, and the mass percentage content of hard carbon in negative pole active material is recorded as B;A and B, meet the relationship formula: 0.003≤A×B≤0.036.The negative pole piece of the present application can make the lithium ion battery including the negative pole piece to exert better power performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a lithium ion battery. BACKGROUND

[0002] With the wide application of lithium ion battery, more stringent requirements are put forward for the performance of the product. Many application occasions, such as hybrid electric vehicles, have both internal combustion engine and power battery as driving system. When the vehicle starts, a large starting current is required, and when the vehicle brakes, the energy needs to be recovered in a very short time. Therefore, the power requirement of lithium ion battery is higher. Therefore, exploring more advanced high-power lithium ion battery technology has become a key problem in the field. SUMMARY

[0003] The present application aims to overcome the above problems in the prior art and provides a lithium ion battery. The lithium ion battery of the present application can exhibit good power performance.

[0004] The present application provides a lithium ion battery in the first aspect, the lithium ion battery comprises a negative electrode sheet and a positive electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active coating layer located on at least one side surface of the negative electrode current collector; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active coating layer located on at least one side surface of the positive electrode current collector; the lithium ion battery is a laminated battery; in the thickness direction of the negative electrode sheet, the negative electrode active coating layer at least partially covers the positive electrode active coating layer; the negative electrode sheet comprises a negative electrode tab, and the positive electrode sheet comprises a positive electrode tab;

[0005] The lithium ion battery comprises a negative electrode tab and a positive electrode tab, and along the first direction, the negative electrode sheet is connected with the negative electrode tab, and the positive electrode sheet is connected with the positive electrode tab;

[0006] The negative electrode sheet comprises an overhang region, the overhang region refers to the part of the negative electrode sheet corresponding to the non-overlapping region of the projection of the negative electrode active coating layer and the positive electrode active coating layer in the thickness direction of the negative electrode sheet, and the percentage value of the area of the overhang region to the total area of the negative electrode sheet is denoted as A;

[0007] The negative electrode active coating layer comprises a negative electrode active material, and the negative electrode active material comprises hard carbon, and the mass percentage content of the hard carbon in the negative electrode active material is denoted as B;

[0008] The A and the B satisfy the relationship: 0.003≤A×B≤0.036.

[0009] Compared with the prior art, the present application has at least the following advantages:

[0010] (1) The negative active material of the present application uses hard carbon with a large negative electrode layer spacing, which can effectively improve the power performance of the lithium ion battery;

[0011] (2) The present application adjusts the relationship between the mass percentage content of hard carbon in the negative active material and the area ratio of the overhang region to satisfy the relationship formula: 0.003≤A×B≤0.036, which can shorten the overall transmission path of lithium ions between the positive and negative electrodes while ensuring safety, thereby enabling the lithium ion battery including the negative electrode sheet to exhibit better power performance.

[0012] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the present application. Any numerical values not specifically disclosed herein are intended to represent approximate values. For values having a range, the endpoints of the ranges are not to be understood as limited to the exact values. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 Fig. 1 shows a cross-sectional structure schematic diagram of the positive electrode sheet and the negative electrode sheet along the first direction in an example of the present application;

[0014] Figure 2 Fig. 2 shows a top view structure schematic diagram of the positive electrode sheet and the negative electrode sheet in an example of the present application;

[0015] Figure 3 Fig. 3 shows a front SEM schematic diagram of the negative electrode sheet in an example of the present application.

[0016] BRIEF DESCRIPTION OF DRAWINGS

[0017] Negative electrode sheet 100, negative current collector 110, negative active coating 120, positive electrode sheet 200, positive current collector 210, positive active coating 220, insulation layer 230. DETAILED DESCRIPTION

[0018] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0019] Lithium-ion batteries possess advantages such as high energy density, low self-discharge, long lifespan, near-zero memory effect, light weight, and environmental friendliness. They are widely used in portable devices, electric vehicles, and aerospace, and have gained commercial acceptance. Many applications, such as hybrid vehicles that utilize both internal combustion engines and batteries as drive systems, require significant starting currents during vehicle startup and rapid energy recovery during braking, placing high demands on battery power. Therefore, the development of high-output lithium-ion batteries is eagerly anticipated.

[0020] Therefore, based on the above problems, the present invention provides a lithium-ion battery that can achieve better power performance.

[0021] The first aspect of this invention provides a lithium-ion battery, the lithium-ion battery comprising a negative electrode and a positive electrode, such as... Figure 1 The diagram shows a cross-sectional view of the positive and negative electrode sheets along a first direction, according to an example of the present invention. The negative electrode sheet 100 includes a negative current collector 110 and a negative active coating 120 located on at least one side of the negative current collector 110. The positive electrode sheet 200 includes a positive current collector 210 and a positive active coating 220 located on at least one side of the positive current collector 210. The lithium-ion battery is a stacked battery. In the thickness direction of the negative electrode sheet 100, the negative active coating 120 at least partially covers the positive active coating 220. A stacked battery refers to a battery structure in which positive electrode sheets, negative electrode sheets, and separator materials are assembled in a stacked manner to form a battery cell. It is understood that the lithium-ion battery also includes a positive tab and a negative tab, which are respectively connected to the edges of the positive and negative electrode sheets in the first direction. Depending on the actual shape of the electrode sheet, the first direction can be the width direction of the electrode sheet or the length direction of the electrode sheet.

[0022] The negative electrode sheet includes an overhang region, which refers to the portion of the negative electrode sheet corresponding to the non-overlapping area of ​​the projections of the negative electrode active coating 120 and the positive electrode active coating 220 along the thickness direction of the negative electrode sheet. The percentage of the area of ​​the overhang region to the total area of ​​the negative electrode sheet is denoted as A.

[0023] The negative electrode active coating includes a negative electrode active material, which includes hard carbon, and the mass percentage content of hard carbon in the negative electrode active material is denoted as B.

[0024] The A and the B satisfy a relationship: 0.003 ≤ A x B ≤ 0.036, for example, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.027, 0.028, 0.029, 0.03, 0.031, 0.032, 0.033, 0.034, 0.035, or 0.036.

[0025] In one example, 0.008 ≤ A x B ≤ 0.028.

[0026] In yet another example, 0.011 ≤ A x B ≤ 0.022.

[0027] Currently, the commercial lithium-ion battery negative electrode mainly uses graphite-based materials. According to the lithium storage mechanism of LiC6 between graphite layers, the theoretical specific capacity is only 365-382 mAh / g, and the space for improvement is very limited. The lithium diffusion between the graphite layers also restricts its rate performance. Hard carbon, as a new type of negative electrode material, has similar lithium potential and higher specific capacity than graphite. By adding hard carbon to the negative electrode active material, the gram capacity of the negative electrode sheet can be significantly improved. Generally, the gram capacity of the negative electrode sheet containing hard carbon is 20%-35% higher than that of the graphite negative electrode sheet. The high gram capacity of the negative electrode sheet helps the battery to release more electric energy in a short time, providing a power output basis for the improvement of the power performance of the lithium-ion battery, meeting the current demand for high power. More importantly, hard carbon is composed of graphite-like microcrystalline structures and open angular microcrystalline structures. This unique microcrystalline structure not only provides more lithium storage sites, but also has a large interlayer spacing, which is beneficial to the deintercalation of lithium ions between the layers, thereby improving the charge and discharge capacity and rate performance of the negative electrode active material, and effectively improving the output power of the lithium-ion battery, making it have excellent power performance.

[0028] Further, when the ratio of the negative electrode capacity to the positive electrode capacity is greater than 1, that is, the N / P ratio is greater than 1.0, the negative electrode capacity can have a certain redundancy compared with the positive electrode capacity, which can avoid the precipitation of lithium dendrites, is conducive to the development of the positive electrode capacity of the lithium ion battery, improves the initial discharge capacity of the battery, and thus helps to improve the power performance of the lithium ion battery. By adding hard carbon in the negative electrode active material, the present application significantly improves the gram capacity of the negative electrode sheet, and as the gram capacity of the negative electrode sheet increases, the N / P ratio of the positive and negative electrode sheets also increases, satisfying the condition that the ratio of the negative electrode capacity to the positive electrode capacity is greater than 1. However, when the capacity difference between the positive and negative electrode sheets is too large, it may cause uneven lithium ion transmission between the positive and negative electrode sheets, affecting the charge and discharge efficiency and kinetic performance of the battery. Therefore, it is necessary to reduce the capacity difference between the positive and negative electrode sheets to avoid the adverse effects caused by the increase in the gram capacity of the negative electrode sheet. Specifically, the present application finds that the area percentage A of the overhang region can be reduced, but as the area percentage A of the overhang region decreases, the area of the negative electrode active material beyond the positive electrode sheet is too small, affecting the safety performance of the lithium ion battery.

[0029] In summary, in order to better control the N / P ratio of the negative electrode sheet within a suitable range (greater than 1.0, generally about 1.06-1.10, but the range will vary depending on the specific selection of different positive and negative electrode materials, the coating precision of the equipment, etc.), and to ensure the safety performance of the lithium ion battery, the present application adjusts the relationship between the mass percentage content B of hard carbon in the negative electrode active material and the area percentage A of the overhang region, so that they satisfy the relationship: 0.003≤A×B≤0.036. When the area percentage A of the overhang region decreases and the N / P ratio decreases too much, the mass percentage content B of hard carbon in the negative electrode active material can be increased to match the positive and negative electrode capacities, preventing the power performance of the battery from deteriorating. When more hard carbon is added to the negative electrode active material and the N / P ratio of the positive and negative electrode sheets is too large, the matching of the positive and negative electrode capacities can be achieved by correspondingly reducing the area of the overhang region. Moreover, by controlling the N / P ratio within a suitable range, the lithium precipitation of the negative electrode sheet can also be alleviated, thereby avoiding the damage of lithium dendrite precipitation to the SEI film and the battery separator, significantly improving the safety performance of the lithium ion battery; in addition, the utilization rate of the negative electrode active material can be greatly increased, the consumption of the overhang region of the negative electrode sheet can be reduced, and the generation of dead lithium can be avoided, thereby ensuring the deintercalation of lithium ions at the edge position of the electrode sheet, so that the lithium ion battery including the negative electrode sheet can exhibit better power performance.

[0030] In the present application, A is 6%-12%, for example, 6%, 7%, 8%, 9%, 10%, 11% or 12%. When A is greater than 12%, it will cause the capacity difference between the positive and negative electrode sheets to be too large, the migration path of lithium ions as a whole will increase, affecting the charge and discharge efficiency and kinetic performance of the battery, and will cause the waste of the current collector, reducing the overall energy density of the battery; and when A is less than 6%, it is likely to cause short circuit of the electrode sheet during the charge and discharge cycle; therefore, it is necessary to reasonably control the area ratio A of the overhang region to be within a suitable range, so as to ensure that the lithium ion battery has good power performance and excellent safety and economy.

[0031] In an example, A is 8%-10%.

[0032] In the present application, B is 5%-30%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%. The hard carbon negative electrode material has a highly disordered carbon layer structure inside, which produces a large number of defects inside, providing a large number of embedding points for Li + , which can achieve fast embedding of Li + , and the hard carbon layer spacing is large, which will not cause deposition of lithium ions, and is conducive to the de-embedding of high-power lithium ions, so as to improve the charge and discharge capacity and rate performance of the negative electrode active material, and effectively improve the power performance of the lithium ion battery. In addition, due to the large spacing of the hard carbon layer, the embedding and de-embedding of lithium ions hardly shrinks or expands, which will not cause changes in the crystal structure of lithium nickel cobalt manganese oxide, avoiding the problem of damage to the electrode structure due to volume strain of the battery material, and can improve the high-temperature cycle capability of the lithium ion battery. However, when the mass percentage content B of hard carbon in the negative electrode active material is greater than 30%, due to the problems of small density, large voltage curve slope and low coulomb efficiency of hard carbon material, it is easy to cause a large irreversible capacity during the first charge of the lithium ion battery, which seriously affects the improvement of the energy density of the lithium ion battery, in addition, the low compaction density of the hard carbon material is also not conducive to the improvement of the volume energy density of the lithium ion battery, therefore, hard carbon is not suitable for excessive use in the negative electrode active material; and when the mass percentage content B of hard carbon in the negative electrode active material is less than 5%, it will cause the improvement effect of the charge and discharge capacity and rate performance of the negative electrode active material to weaken, which is not conducive to improving the power performance of the lithium ion battery. Therefore, the doping mass percentage content of hard carbon in the negative electrode active material needs to be controlled within a suitable range, so that the lithium ion battery including the negative electrode sheet of the present application has excellent power performance.

[0033] In an example, B is 10%-30%.

[0034] In the present application, the negative active material further comprises other negative active materials, which can include artificial graphite, soft carbon and other carbon-based negative materials.

[0035] In the present application, the mass percentage content of the other negative active material in the negative active material is 70%-95%.

[0036] In an example, the mass percentage content of the other negative active material in the negative active material is 75%-90%.

[0037] In the present application, the width of the overhang area of any one side edge of the negative tab in the first direction is 0.1mm-5mm, for example, 0.1mm, 0.5mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.5mm, 4mm, 4.5mm or 5mm.

[0038] In an example, the width of the overhang area of any one side edge of the negative tab in the first direction is 1mm-3mm.

[0039] In the present application, as shown in Figure 1 On the positive tab 200 in the first direction, the positive current collector 210 includes a positive active area and a positive inactive area, the positive inactive area is located at one side edge of the positive tab 200 in the first direction, the positive active area is connected with the positive inactive area, the positive active area is provided with the positive active coating 220, and the positive inactive area is provided with an insulating layer 230.

[0040] As shown in Figure 1 and Figure 2 As shown in Figure 2 is a top view structural schematic diagram of the positive tab and the negative tab in an example of the present application, the negative tab 100 is closer to one side edge of the positive inactive area and the other side edge of the positive inactive area away from the positive active area, compared with the first direction, the one side edge of the negative tab closer to the positive inactive area does not exceed the other side edge of the positive inactive area away from the positive active area, that is, one side edge of the negative tab 100 falls within the positive inactive area where the insulating layer 230 is located.

[0041] The short circuit between the positive current collector and the negative active coating is the most dangerous short circuit mode, which greatly limits the power output of the lithium ion battery and affects the power performance of the lithium ion battery once it occurs. Moreover, the excessive current generated by the short circuit can cause the temperature inside the battery to rise, which can easily lead to safety accidents such as overheating, fire, and even explosion, thereby affecting the stability and reliability of the lithium ion battery in high-power applications.

[0042] The present application can effectively avoid the short circuit between the positive current collector and the negative active coating by providing a positive non-active area containing an insulating layer on one side edge of the positive current collector and allowing one side edge of the negative sheet to fall within the positive non-active area containing the insulating layer, thereby significantly reducing the risk of internal short circuit of the battery and improving the safety of the lithium ion battery, providing a stable and reliable application basis for high-power lithium ion batteries, and further improving the high-power characteristics of the lithium ion battery of the present application.

[0043] However, compared to die cutting of the positive active coating area, die cutting of the insulating layer is more likely to produce burrs and may also have the risk of piercing the separator and causing short circuit. Therefore, in the present application, along the first direction, the side edge of the positive non-active area away from the positive active area exceeds the side edge of the negative sheet close to the positive non-active area by 0.5-3 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, or 3 mm. By making the positive sheet non-active area closer to the side edge of the negative sheet by a distance, i.e., making the side edge of the insulating layer with die cutting burrs exceed the side edge of the negative sheet by 0.5-3 mm, the problem of piercing the separator caused by die cutting burrs in the ceramic adhesive of the insulating layer can be avoided, and the ceramic adhesive can also play a good insulating role, thereby ensuring the safety of the battery. In an example, the side edge of the positive non-active area away from the positive active area along the first direction of the positive sheet exceeds the same side edge of the negative sheet by 0.8-2.8 mm.

[0044] In summary, the design of the positions of the positive and negative sheets and the insulating layer in the present application effectively improves the safety of the lithium ion battery, provides a stable and reliable application basis for high-power lithium ion batteries, and enables them to exhibit superior power performance.

[0045] Further, in the present application, the width ratio of the negative electrode sheet to the positive electrode active area in the first direction is (1.03-1.08):1, for example, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1 or 1.08:1.

[0046] In the present application, the area ratio of the negative electrode sheet to the positive electrode active area is (1-1.1):1, for example, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1 or 1.1:1.

[0047] By further adjusting the width ratio of the negative electrode sheet to the positive electrode active area in the first direction of the positive electrode sheet and the area ratio corresponding thereto respectively, the size of the area of the part of the negative electrode sheet in the first direction beyond the positive electrode sheet, i.e. the size of the area of the overhang region, can be further adjusted, so as to reduce the formation of lithium dendrites and further improve the safety of the lithium ion battery. However, the overhang region itself does not participate in the electrochemical reaction, which means that the total energy output of the negative electrode sheet relative to its volume or mass will be reduced, thereby causing the energy density of the battery to decrease. By adjusting the width ratio of the negative electrode sheet to the positive electrode active area and the area ratio corresponding thereto respectively, the overall energy density of the battery can be optimized through reasonable design, so as to have excellent overall energy density while ensuring high safety.

[0048] In the present application, the positive electrode active coating layer comprises a positive electrode active material, and the positive electrode active material comprises Li (1+x) Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is at least one of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr, and the positive electrode active material comprises secondary particles formed by primary particles. The secondary particles of the positive electrode active material of the present application can be formed by aggregation of the primary particles of the positive electrode active material.

[0049] The charging and discharging mechanism of the lithium ion battery is realized through positive and negative electrode reactions. For high-power type battery cells, the specific material selection and particle size matching of the positive and negative electrodes are particularly important for high-rate charging and discharging. The positive electrode active material in the application adopts the ternary material as described in the above chemical formula, and is matched with a negative electrode active material system containing hard carbon, which can effectively improve the lithium ion diffusion coefficient of the positive electrode active material, and improve the charging and discharging capacity and rate performance of the lithium ion battery. This is because the negative electrode active material system containing hard carbon has a larger interlayer spacing than the pure graphite negative electrode active material system, and when used together with the positive electrode active material, it is more conducive to the deintercalation of high-power lithium ions, improves the lithium ion diffusion coefficient, and thus can further improve the rate performance of the lithium ion battery.

[0050] In an example, the ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon is 1:(1-2.1), for example 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2 or 1:2.1. The ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon is 1:(1-2.1).

[0051] The particle size Dv50 of each of the above particles can be obtained by testing with a particle size tester and then taking the average value. The test method is as follows: using a Malvern MS3000, setting the test conditions as follows: refractive index 2.1, absorption rate 1.0, shading degree 8-12%, dispersing agent water (or ethanol), stirring rate 2500 rpm, testing 3 times respectively, and then taking the average value to obtain the particle size Dv50 value of each of the above particles.

[0052] In another example, the ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon is 1:(1.2-2).

[0053] Further, since the matching of the particle sizes of the positive and negative electrodes has a greater impact on the high-rate charging and discharging of the lithium ion battery, the large-rate discharging capacity of the lithium ion battery can be improved by adjusting the ratio range between the particle size Dv50 of the positive electrode active material and the particle size Dv50 of the hard carbon, thereby further improving the power performance of the lithium ion battery.

[0054] In the application, the particle size Dv50 of the positive electrode active material is 3.5-4.5 μm, for example 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm or 4.5 μm.

[0055] In an example, the particle size Dv50 of the positive electrode active material is 3.6-4.2 μm.

[0056] In the present application, the particle size Dv50 of the hard carbon is 2 μm-3.5 μm, for example 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm or 3.5 μm.

[0057] In an example, the particle size Dv50 of the hard carbon is 2.5 μm-3.2 μm.

[0058] In the present application, the lithium ion battery further comprises an electrolyte, the electrolyte comprises 1,3-propane sultone, the mass percentage content of 1,3-propane sultone in the electrolyte is C based on the total mass of the electrolyte; the mass percentage content of element Co in the positive electrode active material is D based on the total mass of the positive electrode active material;

[0059] The C and the D satisfy the relationship: 0.05≤C / D≤0.12, for example 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11 or 0.12. In an example, 0.06≤C / D≤0.10.

[0060] The positive electrode active material has the problems of water absorption and side reactions at high voltage, the 1,3-propane sultone (PS) additive added in the electrolyte can improve the high temperature performance of the electrolyte, inhibit the occurrence of side reactions, thereby relieving the gas production problem and reducing the internal resistance of the battery; element Co can inhibit the phase change of the battery during charging and discharging, but too high content will oxidize the electrolyte, causing the high temperature cycle / storage performance of the lithium ion battery to deteriorate, PS is beneficial to the high temperature cycle / storage performance of the lithium ion battery, but too much PS will damage the rate performance of the battery, so the amount of the two needs to be controlled to ensure that the battery has good high temperature cycle and storage capacity. Therefore, by further controlling the ratio range between the mass percentage content C of 1,3-propane sultone in the electrolyte and the mass percentage content D of element Co in the positive electrode active material, the storage gas production of the lithium ion battery can be significantly improved, the cycle life of the lithium ion battery is greatly improved, thereby avoiding the adverse effects of selecting the positive electrode active material as the positive electrode material matched with the hard carbon negative electrode active material system, and further helping to stabilize the high power performance of the lithium ion battery of the present application.

[0061] In the present application, the C is 0.6%-1.5%, for example, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%. When the mass percentage content C of 1,3-propane sultone is greater than 1.5%, it may cause the viscosity of the electrolyte to increase, and cause the internal resistance of the battery to increase; when the mass percentage content C of 1,3-propane sultone is less than 0.6%, the occurrence of side reactions in the electrolyte cannot be well inhibited, especially the lithium ion battery under high power may have a gas swelling problem due to the intensification of side reactions, affecting the cycle performance and power performance of the lithium ion battery. Therefore, it is necessary to control the mass percentage content C of 1,3-propane sultone within a suitable range.

[0062] In an example, the C is 0.8%-1.3%.

[0063] In the present application, the D is 11%-13%, for example, 11%, 11.1%, 11.2%, 11.3%, 11.4%, 11.5%, 11.6%, 11.7%, 11.8%, 11.9%, 12%, 12.1%, 12.2%, 12.3%, 12.4%, 12.5%, 12.6%, 12.7%, 12.8%, 12.9%, or 13%. The element Co can inhibit the phase change of the battery cell charging and discharging process, stabilize the layered structure of the positive active material, reduce the impedance value of the positive plate, and improve the electrical conductivity of the positive plate, thereby effectively improving the cycle performance and power performance of the lithium ion battery. However, when the mass percentage content D of the element Co in the positive active material is less than 11%, Li-Ni mixing may occur in the material, and the synthesis of the positive active material may be difficult; when the mass percentage content D of the element Co in the positive active material is greater than 13%, the electrolyte may be oxidized, causing the high-temperature performance of the lithium ion battery to decrease; therefore, it is necessary to control the mass percentage content D of the element Co in the positive active material within a suitable range, thereby helping to improve the adverse effects of adjusting the mass percentage content D of the element Co in the positive active material.

[0064] In an example, the D is 11.3%-12.8%.

[0065] In the present application, the insulating layer includes a ceramic glue, and the ceramic glue includes a polymer resin and a filler. The ceramic glue can also include a curing agent, a diluent, a toughening agent, or other additives such as a coupling agent, and other additives that can be selected from conventional additives used in the art.

[0066] In an example, the polymer resin includes at least one of a polyester, an epoxy resin, a polyurethane, a polybutadiene acid, a silicone, a polyester imine, and a polyimide.

[0067] In an example, the filler comprises at least one of boehmite, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, Al(OH)3, Mg(OH)2, and SiC.

[0068] In an example, the ceramic adhesive is AT9 ceramic adhesive.

[0069] In the present application, the negative electrode active coating of the negative electrode sheet can further comprise a binder and a conductive agent; in the present application, the positive electrode active material of the positive electrode sheet can also comprise a binder and a conductive agent. The binder and the conductive agent can be prepared by conventional methods in the art or obtained by commercial purchase.

[0070] In the present application, the lithium ion secondary battery further comprises a separator, which can be prepared by conventional methods in the art or obtained by commercial purchase.

[0071] In the present application, the electrolyte further comprises an organic solvent, an additive, and an electrolyte lithium salt, the electrolyte lithium salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide salt, lithium tetrafluoroborate, and lithium difluoro(oxalato)borate; the organic solvent comprises at least one of N-methylpyrrolidone (NMP), carbonates, ethers, and amides, and the additive can comprise various types of additives commonly used in the art.

[0072] In the present application, the lithium ion battery can be a Z-type stacked battery comprising a continuous separator, or an E-type stacked battery comprising multiple separators.

[0073] The present application will be described in detail below through examples. The examples described in the present application are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0074] In the following examples, the materials used are commercially available analytical pure unless otherwise specified.

[0075] Example 1

[0076] (1) Preparation of the positive electrode sheet

[0077] The ternary material 613NCM (LiNi 0.6 Co 0.1 Mn 0.3O2) as the positive active material, positive active material, conductive carbon black, PVDF, in a ratio of 95.5%:3.5%:1%, and high-speed stirring to obtain a mixture containing a positive active material, wherein the particle size Dv50 of the positive active material is 4 μm. The mixture is used to prepare a positive active material slurry using NMP (N-methyl pyrrolidone) as a solvent, and the solid content in the slurry is 60%. The slurry is uniformly coated on both sides of the aluminum foil to form a positive active coating, and 4 mm of AT9 ceramic adhesive is coated on the edge of the side of the slurry to form an insulating layer. After drying and rolling, a positive electrode sheet is obtained.

[0078] (2) Preparation of negative electrode sheet

[0079] The active material artificial graphite, hard carbon, binder (SBR, styrene-butadiene rubber), and conductive agent (conductive carbon black) are mixed and high-speed stirred to obtain a mixture containing a negative active material. In the mixture, the solid content includes 80% artificial graphite, 15% hard carbon, 2% conductive agent, and 3% binder SBR, wherein the particle size Dv50 of the hard carbon is 2.5 μm, and the ratio of the particle size Dv50 of the positive active material to the particle size Dv50 of the hard carbon is 1.6:1 according to step (1). A negative active material slurry is prepared using water as a solvent, and the solid content in the slurry is 45%. The slurry is uniformly coated on both sides of the copper foil, and after drying and rolling, a negative electrode sheet is obtained. The SEM diagram of the negative electrode sheet is shown in FIG. 2. Figure 3

[0080] (3) Die cutting of electrode sheet

[0081] The positive electrode sheet obtained in step (1) is punched to 67 (63 mm of paste + 4 mm of insulating adhesive) mm*45 mm; the negative electrode sheet obtained in step (2) is punched to 66 mm*47 mm; the percentage value A of the overhang area to the total area of the negative electrode sheet is 8.6%, wherein the width of the overhang area of the negative electrode sheet near the edge of the insulating layer of the positive electrode sheet is 2 mm, the width of the overhang area of the other edge is 1 mm, the width ratio of the negative electrode sheet to the positive active area in the first direction of the positive electrode sheet is 1.05:1, and the area ratio of the negative electrode sheet to the positive active area is 1.09:1.

[0082] (4) Battery assembly

[0083] A bare cell is formed by using Z-type stacking, wherein as shown in FIG. 3, Figure 2 Figure 2 ​​The top view structure of the positive electrode sheet and the negative electrode sheet is shown in the figure. The positive electrode active coating (active area) of the positive electrode sheet is 2 mm lower than the same side edge of the negative electrode sheet along the first direction. The insulating layer (non-active area) of the positive electrode sheet is 2 mm beyond the same side edge of the negative electrode sheet along the first direction. The aluminum tab and the copper-nickel plated tab are respectively turned out. The bare battery is clamped using a glass clamp, and the force of the glass clamp is 100 MPa / m 2 The battery is then baked at 85°C for 24 hours in a vacuum oven and packaged with an aluminum plastic film. The electrolyte is a lithium hexafluorophosphate electrolyte containing 1M, and the solvent is a mixed solvent of ethylene carbonate / dimethyl carbonate / 1,2 propylene carbonate in a volume ratio of 1:1:1. 1% of 1,3-propane sulfone (PS) is used as an additive. After packaging, the battery is formed and aged to obtain a square soft package battery with a length of 7.8 mm, a width of 50 mm, and a thickness of 75 mm.

[0084] The other settings of Example 1 can be specifically referred to Tables 1 and 2.

[0085] Example 2 group

[0086] Example 2 group refers to Example 1, the only difference is that the mass percentage content B of hard carbon in the negative electrode active material in the negative electrode active material is changed. See Tables 1 and 2 for details:

[0087] Example 2-1: (2) Preparation of negative electrode sheet: active material contains 65% artificial graphite, 30% hard carbon, 2% conductive agent, and 3% binder SBR;

[0088] Example 2-2: (2) Preparation of negative electrode sheet: active material contains 90% artificial graphite, 5% hard carbon, 2% conductive agent, and 3% binder SBR;

[0089] Example 2-3: (2) Preparation of negative electrode sheet: active material contains 91% artificial graphite, 4% hard carbon, 2% conductive agent, and 3% binder SBR;

[0090] Example 2-4: (2) Preparation of negative electrode sheet: active material contains 53% artificial graphite, 42% hard carbon, 2% conductive agent, and 3% binder SBR.

[0091] Example 3 group

[0092] Example 3 group refers to Example 1, the only difference is that the width of the insulating layer coating insulating glue of the positive electrode sheet is changed, and the width value of the insulating layer (non-active area) of the positive electrode sheet beyond the same side edge of the negative electrode sheet along the first direction (referred to as the insulating layer beyond the negative electrode sheet in Table 1). See Tables 1 and 2 for details:

[0093] Example 3-1: (4) Cell assembly: the insulating layer (non-active area) of the positive electrode sheet exceeds the same side edge of the negative electrode sheet along the first direction of the sheet by 0.5 mm along one side edge of the first direction of the sheet, and the insulating layer has a width of 2.5 mm;

[0094] Example 3-2: (4) Cell assembly: the insulating layer (non-active area) of the positive electrode sheet exceeds the same side edge of the negative electrode sheet along the first direction of the sheet by 3 mm along one side edge of the first direction of the sheet, and the insulating layer has a width of 5 mm;

[0095] Example 3-3: (4) Cell assembly: the insulating layer (non-active area) of the positive electrode sheet exceeds the same side edge of the negative electrode sheet along the first direction of the sheet by 5 mm along one side edge of the first direction of the sheet, and the insulating layer has a width of 7 mm.

[0096] Example 3-4: (4) Cell assembly: the insulating layer (non-active area) of the positive electrode sheet exceeds the same side edge of the negative electrode sheet along the first direction of the sheet by 0.1 mm along one side edge of the first direction of the sheet, and the insulating layer has a width of 2.1 mm.

[0097] Example 4 group

[0098] Example 4 group refers to Example 1, the only difference is that the size of the electrode sheet die cutting punch is changed, so as to change the percentage value A of the overhang area to the total area of the negative electrode sheet, see Table 1 and Table 2 for details:

[0099] Example 4-1: (3) Electrode sheet die cutting: the positive electrode sheet is punched to 64.6 mm (60.6 mm paste + 4 mm insulating glue) mm * 45 mm; the negative electrode sheet is punched to 66 mm * 47 mm; the percentage value A of the overhang area to the total area of the negative electrode sheet is 12%, wherein the width of the overhang area of the negative electrode sheet near one side edge of the insulating layer of the positive electrode sheet is 2 mm, and the width of the overhang area of the negative electrode sheet near the other side edge is 3.4 mm, the width ratio of the negative electrode sheet to the positive active area in the first direction of the positive electrode sheet is 1.09:1, and the area ratio of the negative electrode sheet to the positive active area is 1.14:1;

[0100] Example 4-2: (3) Electrode sheet die cutting: the positive electrode sheet is punched to 68.8 mm (64.8 mm paste + 4 mm insulating glue) mm * 45 mm; the negative electrode sheet is punched to 66 mm * 47 mm; the percentage value A of the overhang area to the total area of the negative electrode sheet is 6%, wherein the width of the overhang area of the negative electrode sheet near one side edge of the insulating layer of the positive electrode sheet is 1 mm, and the width of the overhang area of the negative electrode sheet near the other side edge is 0.2 mm, the width ratio of the negative electrode sheet to the positive active area in the first direction of the positive electrode sheet is 1.02:1, and the area ratio of the negative electrode sheet to the positive active area is 1.06:1;

[0101] Example 4-3: (3) Tab die-cutting: the positive electrode tab is punched to 62.5 mm (58.5 mm paste + 4 mm insulation) * 45 mm; the negative electrode tab is punched to 66 mm * 47 mm; the overhang area percentage value A of the negative electrode tab is 15%, wherein the width of the overhang area of the negative electrode tab near the edge of the positive electrode tab insulation layer is 2 mm, the width of the overhang area of the negative electrode tab on the other side edge is 5.5 mm, the width ratio of the negative electrode tab to the positive active area in the first direction of the positive electrode tab is 1.12:1, and the area ratio of the negative electrode tab to the positive active area is 1.19:1.

[0102] Example 5 group

[0103] Example 5 group is based on Example 1, the only difference is that the particle size Dv50 of hard carbon is changed, see Table 1 and Table 2 for details:

[0104] Example 5-1: (2) Preparation of negative electrode tab: the particle size Dv50 of hard carbon is 3.5 μm, according to step (1), the ratio of the particle size Dv50 of positive active material to the particle size Dv50 of hard carbon is 1.1:1;

[0105] Example 5-2: (2) Preparation of negative electrode tab: the particle size Dv50 of hard carbon is 1.5 μm, according to step (1), the ratio of the particle size Dv50 of positive active material to the particle size Dv50 of hard carbon is 2.7:1;

[0106] Example 5-3: (2) Preparation of negative electrode tab: the particle size Dv50 of hard carbon is 4.8 μm, according to step (1), the ratio of the particle size Dv50 of positive active material to the particle size Dv50 of hard carbon is 0.8:1.

[0107] Example 6 group

[0108] Example 6 group is based on Example 1, the only difference is that the amount of 1,3-propane sultone (PS) additive in the electrolyte is changed, see Table 1 for details:

[0109] Example 6-1: (4) Battery assembly: 0.6% PS is used as electrolyte additive;

[0110] Example 6-2: (4) Battery assembly: 1.5% PS is used as electrolyte additive;

[0111] Example 6-3: (4) Battery assembly: 0% PS is used as electrolyte additive (no PS additive is used).

[0112] Example 7 group

[0113] Example 7 group was conducted according to Example 1, the only difference being that the particle size Dv50 of the positive electrode active material was changed, see Table 1 and Table 2 for details:

[0114] Example 7-1: (1) Preparation of the positive electrode sheet: the particle size Dv50 of the positive electrode active material was 3.5 pm, the ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon was 1.4:1;

[0115] Example 7-2: (1) Preparation of the positive electrode sheet: the particle size Dv50 of the positive electrode active material was 4.5 pm, the ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon was 1.8:1;

[0116] Example 7-3: (1) Preparation of the positive electrode sheet: the particle size Dv50 of the positive electrode active material was 3 pm, the ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon was 1.2:1;

[0117] Example 7-4: (1) Preparation of the positive electrode sheet: the particle size Dv50 of the positive electrode active material was 5 pm, the ratio of the particle size Dv50 of the positive electrode active material to the particle size Dv50 of the hard carbon was 2:1.

[0118] Example 8 group

[0119] Example 8 group was conducted according to Example 1, the only difference being that the mass percentage content D of the element Co in the positive electrode active material was changed, see Table 1 and Table 2 for details:

[0120] Example 8-1: LiNi 0.6 Co 0.085 Mn 0.315 O2, D was 11%;

[0121] Example 8-2: LiNi 0.6 Co 0.115 Mn 0.285 O2, D was 13%.

[0122] Example 9 group

[0123] Example 9 group was conducted according to Example 1, the only difference being that the amount of the 1,3-propane sultone (PS) additive added in the electrolyte was changed, the mass percentage content D of the element Co in the positive electrode active material was changed, see Table 1 and Table 2 for details:

[0124] Example 9-1: LiNi 0.6 Co 0.125 Mn 0.275 O2, D was 15%, (4) Battery assembly: 0.5% PS was used as the electrolyte additive;

[0125] Example 9-2: LiNi 0.6 Co 0.075 Mn 0.325 O2, D is 10%, (4) battery assembly: 2% PS is used as electrolyte additive.

[0126] Example 10

[0127] Example 10 is carried out according to Example 1, with the only difference being that during the process of battery assembly, E-shaped laminations are used to form the bare battery cell, see Table 1 and Table 2 for details.

[0128] Comparative Example 1

[0129] Comparative Example 1 is carried out according to Example 1, with the only difference being that the mass percentage content B of hard carbon in the negative active material is changed, see Table 1 and Table 2 for details:

[0130] (2) Preparation of negative electrode sheet: the active material contains 95% artificial graphite, 2% conductive agent, and 3% binder SBR (without hard carbon).

[0131] Comparative Example 2

[0132] Comparative Example 2 is carried out according to Example 1, with the only difference being that the size of the electrode sheet die-cutting punch is changed, thereby changing the percentage value A of the overhang area to the total area of the negative electrode sheet, and changing the mass percentage content B of hard carbon in the negative active material, see Table 1 and Table 2 for details:

[0133] (3) Die-cutting of electrode sheet: the positive electrode sheet is punched to 62.5 mm (58.5 mm paste + 4 mm insulation glue) mm * 45 mm; the negative electrode sheet is punched to 66 mm * 47 mm; the percentage value A of the overhang area to the total area of the negative electrode sheet is 15%, wherein the width of the overhang area of one side edge is 2 mm, and the width of the overhang area of the other side edge is 5.5 mm, the width ratio of the negative electrode sheet to the positive active area in the first direction of the positive electrode sheet is 1.12:1, and the area ratio of the negative electrode sheet to the positive active area is 1.19:1;

[0134] (2) Preparation of negative electrode sheet: the active material contains 65% artificial graphite, 30% hard carbon, 2% conductive agent, and 3% binder SBR.

[0135] Comparative Example 3

[0136] Comparative Example 3 was performed according to Example 1, with the only difference being that the overhang area percentage value A of the total area of the negative electrode tab was changed by changing the size of the tab die-cutting punch, and the mass percentage content B of the hard carbon in the negative electrode active material was changed by changing the mass percentage content of the hard carbon in the negative electrode active material, as shown in Table 1 and Table 2:

[0137] (3) Tab die-cutting: the positive electrode tab was punched to 68.8 mm (64.8 mm paste + 4 mm insulating glue) mm * 45 mm; the negative electrode tab was punched to 66 mm * 47 mm; the overhang area percentage value A of the total area of the negative electrode tab was 6%, wherein the width of the overhang area of the negative electrode tab near the edge of the positive electrode tab insulating layer was 1 mm, and the width of the overhang area of the other edge was 0.2 mm, the width ratio of the negative electrode tab to the positive active area in the first direction of the positive electrode tab was 1.02:1, and the area ratio of the negative electrode tab to the positive active area was 1.06:1;

[0138] (2) Preparation of the negative electrode tab: the active material contained 91% artificial graphite, 4% hard carbon, 2% conductive agent, and 3% binder SBR.

[0139] Comparative Example 4

[0140] Comparative Example 4 was performed according to Example 1, with the only difference being that the width of the insulating layer (non-active area) of the positive electrode tab along the first direction of the same side edge of the negative electrode tab along the first direction (referred to as the insulating layer overhangs the negative electrode tab in Table 1) was changed by changing the width of the insulating glue coated on the insulating layer of the positive electrode tab, as shown in Table 1 and Table 2:

[0141] (4) Battery assembly: the insulating layer (non-active area) of the positive electrode tab along the first direction of the same side edge of the negative electrode tab along the first direction was 0 mm (not overhanging the negative electrode), and the insulating layer width was 2 mm.

[0142] Table 1

[0143]

[0144] Table 2

[0145]

[0146]

[0147] Lithium ion battery test example

[0148] (1) Power performance test:

[0149] The lithium ion batteries prepared in the above examples and comparative examples were discharged at 25°C, 50% SOC constant current 10C for 3s;

[0150] a. At 25°C, the lithium ion battery prepared in the above examples and comparative examples was subjected to capacity setting: 1C discharge to the lower limit voltage, 1C charge to the upper limit voltage, and 1C discharge to the lower limit voltage again, and the capacity discharged was recorded as Co (initial capacity);

[0151] b. 1C charge to the upper limit voltage, 1C discharge for 30 min, and the cell was adjusted to a state of 50% SOC;

[0152] c. 10C0 constant current discharge was used for 3 s, and the final voltage (V) after the power test discharge of the lithium ion battery was recorded, as shown in Table 3.

[0153] (2) Capacity retention rate of lithium ion battery 60°C calendar life:

[0154] a. At 25°C, the lithium ion battery prepared in the above examples and comparative examples was subjected to capacity setting: 1C discharge to the lower limit voltage, 1C charge to the upper limit voltage, and 1C discharge to the lower limit voltage again, and the capacity discharged was recorded as Co (initial capacity); 1C charge to the upper limit voltage (full charge storage);

[0155] b. Storage at 60°C environment for 45 days;

[0156] c. After storage, the cell was discharged at 1C to the lower limit voltage, charged at 1C to the upper limit voltage, and discharged at 1C to the lower limit voltage again at 25°C, and the capacity discharged was recorded as C1 (capacity after storage); C1 / C0 was recorded as the storage capacity retention rate (%) of the lithium ion battery 60°C calendar life, as shown in Table 3.

[0157] The specific method was to record the capacity retention rate of the cell after 60 days of storage.

[0158] (3) Needle puncture passing rate test:

[0159] 1C / 1C was made to Co, and after 1C full charge, 1C discharge was performed to 80% SOC (20% Co capacity was cut off); a high-temperature resistant steel needle with a diameter of ф3.00 mm (the conical angle of the needle tip was 45°-60°, and the surface of the needle was smooth without rust, oxidation layer and oil stains) was used to penetrate from the direction perpendicular to the battery plate at a speed of (80 mm±5 mm / s), and the puncture position was preferably close to the geometric center of the punctured surface (the steel needle was left in the battery). Observe for 1 h. Determine whether the cell will catch fire, if it catches fire, the cell does not pass the needle puncture, and if it does not catch fire, it is determined that the cell can pass the needle puncture; repeat the above test several times, calculate the needle puncture passing rate (%) of the needle puncture test, as shown in Table 3.

[0160] Table 3

[0161]

[0162]

[0163] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A lithium-ion battery, characterized by, The lithium ion battery comprises a negative electrode sheet and a positive electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active coating layer located on at least one side surface of the negative electrode current collector; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active coating layer located on at least one side surface of the positive electrode current collector; the lithium ion battery is a laminated battery; in the thickness direction of the negative electrode sheet, the negative electrode active coating layer at least covers the positive electrode active coating layer; The lithium ion battery comprises a negative electrode tab and a positive electrode tab, along a first direction, the negative electrode sheet is connected with the negative electrode tab, and the positive electrode sheet is connected with the positive electrode tab; The negative electrode sheet comprises an overhang region, the overhang region refers to a part of the negative electrode sheet corresponding to a non-overlapping region of projections of the negative electrode active coating layer and the positive electrode active coating layer in the thickness direction of the negative electrode sheet, and a percentage value of an area of the overhang region to a total area of the negative electrode sheet is denoted as A; The negative electrode active coating layer comprises a negative electrode active material, and the negative electrode active material comprises hard carbon, and a mass percentage content of the hard carbon in the negative electrode active material is denoted as B; The A and the B satisfy a relationship formula: 0.003≤A×B≤0.036, wherein the A is 6%-12%, and the B is 5%-30%. The positive electrode current collector comprises a positive electrode active region and a positive electrode inactive region, the positive electrode inactive region is located at an edge in the first direction, the positive electrode active region is connected with the positive electrode inactive region, the positive electrode active region is provided with the positive electrode active coating layer, and the positive electrode inactive region is provided with an insulating layer; Along the first direction, a side edge of the negative electrode sheet close to the positive electrode inactive region does not exceed a side edge of the positive electrode inactive region away from the positive electrode active region.

2. The lithium-ion battery of claim 1, wherein, A width of the overhang region of the negative electrode sheet at any one side edge of the negative electrode sheet in the first direction is 0.1mm-5mm.

3. The lithium-ion battery of claim 1, wherein, Along the first direction, a side edge of the positive electrode inactive region away from the positive electrode active region exceeds a side edge of the negative electrode sheet close to the positive electrode inactive region by 0.5mm-3mm.

4. The lithium-ion battery of claim 1, wherein, A width ratio of the negative electrode sheet to the positive electrode active region in the first direction is (1.03-1.08):1; And / or, an area ratio of the negative electrode sheet to the positive electrode active region is (1-1.1):

1.

5. The lithium-ion battery of claim 1, wherein, The positive electrode active coating includes a positive electrode active material including Li (1+x) Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is at least one of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr, and the positive electrode active material includes secondary particles formed of primary particles.

6. The lithium-ion battery of claim 5, wherein, A ratio of a particle size Dv50 of the positive electrode active material to a particle size Dv50 of the hard carbon is (1-2.1):

1.

7. The lithium-ion battery of claim 5, wherein, The particle size Dv50 of the positive electrode active material is 3.5µm-4.5µm.

8. The lithium-ion battery of claim 5, wherein, The particle size Dv50 of the hard carbon is 2µm-3.5µm.

9. The lithium-ion battery of claim 5, wherein, The lithium ion battery further comprises an electrolyte, the electrolyte comprises 1,3-propane sultone, a mass percentage content of the 1,3-propane sultone based on a total mass of the electrolyte is C, and a mass percentage content of an element Co based on a total mass of the positive electrode active material is D; The C and the D satisfy a relationship formula: 0.05≤C / D≤0.

12.

10. The lithium-ion battery of claim 9, wherein, The C is 0.6%-1.5%; and / or, the D is 11%-13%.

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