Negative electrode sheet, cylindrical battery, battery pack, and electric tool

Abstract

The present invention provides a negative electrode plate, a cylindrical battery and a battery pack, and an electric tool. The negative electrode plate provided by the present invention controls the thickness of the negative electrode silicon-based active material on the negative electrode current collector by controlling the surface density and compaction density of the negative electrode plate, thereby improving the conductivity of the negative electrode plate while ensuring the lithium storage capacity of the negative electrode plate. Based on the large market demand for cylindrical steel shell batteries, which are limited by size, safety and cost considerations, the cylindrical battery provided by the present invention adopts the above-mentioned negative electrode plate. Taking the 18650 cylindrical battery as an example, by optimizing the structure, improving the system and the manufacturing process, the high capacity and high rate of the battery can be achieved at the same time. The battery energy density and power output capacity can be significantly improved, providing the market with a more efficient and reliable energy solution, which has broad application prospects and market value.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative electrode sheet, a cylindrical battery and a battery pack, and an electric tool. Background Art

[0002] Lithium-ion batteries have become the preferred power source in the current energy storage electronics industry due to their advantages of high capacity and high energy density. With the continuous development of science and technology in recent years, all walks of life have put forward higher requirements for the capacity, energy density, and safety performance of lithium-ion batteries. The performance of lithium-ion batteries depends on factors such as positive electrode materials, negative electrode materials, diaphragms, electrolytes, and battery structure design. Among them, the performance improvement of negative electrode materials is the key factor in improving the performance of the entire battery. At present, lithium-ion batteries on the market generally use graphite negative electrode materials, and the theoretical lithium storage capacity of graphite negative electrode materials is low, which can no longer meet the demand for comprehensive battery improvement of lithium-ion batteries.

[0003] In this context, the use of silicon-based materials as negative electrode materials can theoretically increase the lithium storage capacity and significantly improve the energy density of lithium-ion batteries, which is currently the best choice. However, although the use of silicon-based materials as negative electrode materials can theoretically improve the lithium storage capacity, there are also the following problems: First, the huge volume expansion effect of silicon-based materials causes silicon particles to easily break and fall off from the current collector during the cycle, which shortens the cycle life of the battery; second, the conductivity of silicon-based materials is poor. During the charge and discharge cycle of the battery, the negative electrode active material is powdered and cracked, and the negative electrode active material and the conductive agent fall off together. At the same time, SEI is repeatedly generated, which continuously consumes lithium ions, resulting in an increase in the internal resistance of the battery, a large amount of heat, a rapid decrease in battery capacity, and poor rapid charge and discharge capabilities, which cannot increase the charge and discharge rate of the battery. Currently, the more mature cylindrical lithium-ion batteries on the market are 18650 batteries, which either have a capacity between 1200mAh-3000mAh, and a maximum continuous cycle discharge rate of 6C, but have a small capacity and a short single discharge time, which cannot meet customers' long-term power needs; or have a capacity between 3000mAh-4000mAh, but a maximum continuous cycle discharge rate of only 3C. When used in many power tools, the 3C discharge rate cannot meet power needs.

[0004] In the Chinese patent publication number CN108258236B, a high specific capacity and high cycle life 18650 cylindrical lithium battery is provided, wherein the positive electrode is made of NCA material, and the thickness of the positive electrode sheet is 142μm-146μm; the negative electrode is made of SiC material, and the thickness of the negative electrode sheet is 145μm-152μm. It provides nickel-cobalt-aluminum NCA with a high nickel content as the positive electrode material and silicon-carbon SiC as the negative electrode material, thereby improving the battery capacity of the 18650 battery; although the discharge capacity of the single cell of the battery is ≥3400mAh, the battery can only achieve 0.2C, 0.5C, and 1C discharge rates, that is, the discharge performance of the battery cannot meet the high rate requirements.

[0005] A high-capacity and high-rate cylindrical lithium-ion battery is also provided in the Chinese patent publication number CN113659218B, whose positive electrode adopts ternary material with a thickness of 118±2μm; the negative electrode adopts silicon oxide / graphite composite with a thickness of (90-94)±2μm. However, its specification points out that the cylindrical lithium-ion battery provided by it reduces the thickness of the positive and negative electrodes by reducing the surface density of the positive and negative electrodes while ensuring the high capacity unchanged, so as to achieve a high-rate 8C discharge. However, in this embodiment, on the basis of achieving a high-rate discharge, its battery capacity is only 2600mAh, and it cannot reach a high capacity of more than 3500mAh.

[0006] In Japanese patent publication No. JP2701347B2, a non-aqueous electrolyte secondary battery is provided. The secondary battery is wound with a positive electrode, a separator, and a negative electrode. The thickness of the double-sided active material layer in the positive electrode is A, which is 80μm-250μm; the thickness of the double-sided active material in the negative electrode is B, which is 80μm-250μm; A / B is between 0.6-1.5, and (A+B) is between 250μm-500μm. The secondary battery provided is suitable for lithium-ion batteries with graphite negative electrodes, but for silicon-based negative electrode batteries, due to the huge expansion of the material, the excessive thickness of the negative electrode sheet is easy to cause the sheet to crack, thereby causing battery failure.

[0007] Therefore, when the positive electrode plate adopts ternary materials as the active material and the negative electrode plate adopts silicon-based materials as the active material, how to improve the battery capacity of the lithium-ion battery and how to achieve high-rate discharge performance (3C discharge / 6C discharge) so that the capacity and rate performance can reach a relatively balanced state are technical problems that technical personnel in this field urgently need to solve. Summary of the invention

[0008] The purpose of the present invention is to solve the shortcomings that when the existing lithium-ion batteries use ternary materials as the active materials of the positive electrode plates and silicon-based materials as the active materials of the negative electrode plates, the battery capacity and discharge rate performance cannot achieve both high capacity (above 3.5Ah) and high rate (6C discharge). A negative electrode plate, a cylindrical battery and a battery pack, and an electric tool are provided to alleviate the problems of expansion, poor conductivity and inability to achieve high-rate discharge of silicon-based negative electrode materials.

[0009] In a first aspect, the present invention provides a negative electrode sheet, comprising a negative electrode current collector, a negative electrode tab disposed on the negative electrode current collector, and a negative electrode silicon-based active material;

[0010] The negative electrode current collector comprises a first surface and a second surface arranged along the thickness direction of the negative electrode current collector;

[0011] The negative electrode silicon-based active material is coated on the first surface of the negative electrode current collector to form a first coating surface and a first non-coating surface, and the thickness of the first coating surface is 20 μm-35 μm;

[0012] The negative electrode silicon-based active material is coated on the second surface of the negative electrode current collector to form a second coated surface and a second non-coated surface, and the thickness of the second coated surface is 20 μm-35 μm.

[0013] In one of the embodiments, the negative electrode silicon-based active material contains silicon element, and the mass percentage of the silicon element in the negative electrode silicon-based active material is 40-65%.

[0014] In one embodiment, the gram capacity of the negative electrode silicon-based active material is ≥1200 mAh / g.

[0015] In one embodiment, the unit area density of the negative electrode sheet is 4.0-4.5 mg / cm 2 .

[0016] In one embodiment, the compaction density of the negative electrode plate is 0.6-1.0 g / cm 3 .

[0017] In one embodiment, the compaction density of the negative electrode plate is 0.8 g / cm 3 .

[0018] In one embodiment, the area of ​​the first coating surface is larger than the area of ​​the second coating surface.

[0019] In one embodiment, the area of ​​the first coating surface is 1.05-1.1 of the area of ​​the second coating surface.

[0020] In one of the embodiments, the negative electrode tab includes a first tab and a second tab, the first tab and the second tab are spaced apart in the length direction of the negative electrode current collector and are located on a first non-coated surface and a second non-coated surface, respectively.

[0021] In one embodiment, the negative electrode current collector has two first and second sides parallel to each other along the width direction;

[0022] The first electrode tab includes a first conductive sheet welded to the second non-coated surface and extending outward from the first side, and two first insulating sheets respectively attached to the first non-coated surface and the second non-coated surface and extending outward from the first side; the projection surfaces of the two first insulating sheets on the negative electrode current collector overlap with each other, and the first conductive sheet is located between the two first insulating sheets.

[0023] In one embodiment, the distance between the first conductive sheet and the side edge of the second coating surface is 45 mm-65 mm.

[0024] In one embodiment, the width of the first insulating sheet is 1.5-2.5 times the width of the first conductive sheet.

[0025] In one embodiment, the length of the first insulating sheet extending outward along the first side edge is 0.5 mm-3 mm.

[0026] In one embodiment, the second electrode tab is a second conductive sheet welded to the first coating surface and extending outward from the second side.

[0027] In one embodiment, the distance between the second conductive sheet and the side edge of the first coating surface is 15 mm-20 mm.

[0028] In one embodiment, the length of the first conductive sheet extending outward along the first side is A, and the length of the second conductive sheet extending outward along the first side is B. The length relationship between the two should satisfy the following conditions: A>B and AB>8mm.

[0029] In one embodiment, the width of the second conductive sheet is 0.5-1 of the width of the first conductive sheet.

[0030] In one embodiment, the negative electrode tab includes a main tab arranged on the first uncoated surface or the second uncoated surface and a plurality of auxiliary tabs arranged on the first uncoated surface and / or the second uncoated surface, and the plurality of auxiliary tabs are arranged at intervals along the length direction of the negative electrode current collector.

[0031] In one of the embodiments, the main electrode tab and the plurality of the secondary electrode tabs all extend outward based on the negative electrode current collector, and the main electrode tab and the plurality of the secondary electrode tabs extend outward in the same direction based on the negative electrode current collector.

[0032] In one embodiment, the length of the main electrode tab extending outward based on the negative electrode current collector is greater than the length of the secondary electrode tab extending outward based on the negative electrode current collector.

[0033] The beneficial effect of the negative electrode plate provided by the present invention is that the thickness of the negative electrode silicon-based active material on the negative electrode current collector is controlled by controlling the surface density and compaction density of the negative electrode plate, thereby reducing the adverse effects of the negative electrode silicon-based active material caused by the expansion of the charge and discharge, and reducing the thickness of the dressing as much as possible while ensuring the lithium storage capacity of the negative electrode plate, so as to reduce the migration distance of lithium ions during the charge and discharge process, improve the migration resistance of lithium ions during the charge and discharge process, reduce the internal resistance of the negative electrode plate, achieve the purpose of increasing the current, and improve the conductive performance of the negative electrode plate.

[0034] In a second aspect, the present invention further provides a cylindrical battery, comprising a shell, a cap, an electrolyte disposed in the shell, and a cylindrical winding core, wherein the cylindrical winding core comprises a positive electrode sheet, a separator, and the above-mentioned negative electrode sheet.

[0035] In one embodiment, the positive electrode plate includes a positive electrode current collector, a positive electrode tab disposed on the positive electrode current collector, and a positive electrode active material; the positive electrode active material is a LiNi x Co y Mn 1-x-y O2 material (where x and y values ​​range from 0 to 1).

[0036] In one embodiment, the unit area density of the positive electrode sheet is 28-33 mg / cm 2 .

[0037] In one embodiment, the compaction density of the positive electrode sheet is 3.2-3.8 g / cm 3 .

[0038] In one embodiment, the positive electrode current collector includes a third surface and a fourth surface arranged along the thickness direction of the positive electrode current collector;

[0039] The positive electrode active material is coated on the third surface of the positive electrode current collector to form a plurality of third coating surfaces, a first blank area is formed between two adjacent third coating surfaces, and the thickness of the third coating surface is 35 μm-55 μm;

[0040] The positive electrode active material is coated on the fourth surface of the positive electrode current collector to form a plurality of fourth coating surfaces, a second blank area is formed between two adjacent fourth coating surfaces, and the thickness of the fourth coating surface is 35 μm-55 μm.

[0041] In one embodiment, the positive electrode current collector has two third sides and a fourth side parallel to each other along the width direction;

[0042] The positive electrode tab includes a plurality of third conductive sheets welded to the first blank area and extending outward from the third side, and a plurality of pairs of second insulating sheets respectively attached to the first blank area and the second blank area and extending outward from the third side;

[0043] The projection surfaces of each pair of the second insulating sheets on the positive electrode current collector overlap with each other, and the third conductive sheet is located between two of the second insulating sheets.

[0044] In one embodiment, the third surface of the positive electrode collector is provided with two third coating surfaces and one first blank area, and the two third coating surfaces are symmetrically arranged on both sides of the first blank area, and the fourth surface of the positive electrode collector is provided with two fourth coating surfaces and one second blank area; the positive electrode tab includes a third conductive sheet welded to the first blank area and a pair of the second insulating sheets.

[0045] In one embodiment, the width of the positive electrode tab of the positive electrode plate is the same as the width of the negative electrode tab.

[0046] In one embodiment, the width of the first blank area and the second blank area is at least 2 mm greater than the width of the positive electrode tab.

[0047] In one embodiment, the area of ​​the second insulating sheet is larger than the area of ​​the first blank area or the second blank area of ​​the positive electrode current collector.

[0048] In one embodiment, when winding, the first coated surface of the negative electrode sheet faces the third coated surface of the positive electrode sheet, and the length of the first coated surface is greater than the length of the positive current collector of the positive electrode sheet.

[0049] In one embodiment, the length of the second insulating sheet extending outward along the third side is 2 mm-4 mm, and the length of the second insulating sheet extending outward along the fourth side is 0.2 mm-1.0 mm.

[0050] In one of the embodiments, the cylindrical winding core is assembled in the shell, and the diameter of the cylindrical winding core is 0.96-0.99 of the inner diameter of the shell.

[0051] In one embodiment, the length of the negative electrode plate is 1190mm-1205mm; the length of the positive electrode plate is 1081mm-1091mm.

[0052] In one embodiment, the injection amount of the electrolyte is 5.6g-6.2g.

[0053] In one embodiment, when the cylindrical battery is charged at 0.2C and discharged at 3C, the discharge capacity retention rate is greater than 97% and the temperature rise is 20-35°C.

[0054] In one embodiment, when the cylindrical battery is charged at 0.2C and discharged at 6C, the discharge capacity retention rate is greater than 95% and the temperature rise is 45-65°C.

[0055] In one embodiment, the capacity of the cylindrical battery is greater than 3500 mAh.

[0056] The beneficial effect of a cylindrical battery provided by the present invention is that: by adopting the above-mentioned negative electrode plate, taking the 18650 cylindrical battery as an example, by optimizing the structure, improving the system and the manufacturing process, the high capacity and high rate of the battery can be achieved at the same time to achieve an ideal state, and the battery energy density and power output capacity can be significantly improved, providing the market with a more efficient and reliable energy solution, with broad application prospects and market value; by adopting the above-mentioned negative electrode plate, the lithium ion capacity of the negative electrode plate is increased, and the migration distance of lithium ions during the battery charge and discharge cycle is shortened, so that the cylindrical battery maintains a capacity of more than 3500mAh, and when charged at 0.2C and discharged at 3C, the discharge capacity retention rate is greater than 97%, and the temperature rise is controlled at 20-35°C, and when charged at 0.2C and discharged at 6C, the discharge capacity retention rate is greater than 95%, and the temperature rise is controlled at 45-65°C.

[0057] In a third aspect, the present invention further provides a battery pack, comprising two or more of the above cylindrical batteries, wherein the two or more cylindrical batteries are electrically connected in series or in parallel.

[0058] The beneficial effect of a battery pack provided by the present invention is that by adopting the above-mentioned high-capacity, high-rate cylindrical battery, the overall electrical performance of the battery pack is improved, thereby realizing a high-capacity and high-rate battery pack.

[0059] In a fourth aspect, the present invention further provides an electric tool comprising the above-mentioned battery pack.

[0060] The beneficial effect of the electric tool provided by the present invention is that the working stability of the electric tool is improved by adopting the above-mentioned high-capacity and high-rate battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a structural schematic diagram of a first surface of a negative electrode current collector of a negative electrode plate provided by the present invention;

[0062] Figure 2 It is a structural schematic diagram of the second surface of a negative electrode current collector of a negative electrode plate provided by the present invention;

[0063] Figure 3 is a cross-sectional view of a negative electrode current collector of a negative electrode sheet provided by the present invention;

[0064] Figure 4 It is a schematic diagram of the three-dimensional structure of a cylindrical battery provided by the present invention;

[0065] Figure 5 It is a structural schematic diagram of the third surface of a positive electrode sheet in a cylindrical battery provided by the present invention;

[0066] Figure 6 It is a cross-sectional view of a positive electrode collector of a positive electrode sheet in a cylindrical battery provided by the present invention;

[0067] Figure 7 This is a battery performance test diagram of Example 1 of a cylindrical battery provided by the present invention.

[0068] Description of reference numerals:

[0069] 100-cylindrical battery, 30-diaphragm, 40-cap, 50-shell;

[0070] 10-negative electrode sheet, 11-negative electrode current collector;

[0071] 111-first surface, 111A-first coated surface, 111B-first non-coated surface;

[0072] 112-second surface, 112A-second coated surface, 112B-second non-coated surface;

[0073] 113-first side, 114-second side;

[0074] 12-first pole ear, 121-first conductive sheet, 121A-first ultrasonic weld print, 122-first insulating sheet;

[0075] 13-second pole ear, 131-second conductive sheet, 131A-second ultrasonic welding mark;

[0076] 20-positive electrode plate, 21-positive electrode current collector, 211-third surface, 211A-third coated surface, 211B-first blank area, 212-fourth surface, 212A-fourth coated surface, 212B-second blank area, 213-third side, 214-fourth side, 22-positive electrode ear, 221-third conductive sheet, 221A-third ultrasonic weld mark, 222-second insulating sheet. DETAILED DESCRIPTION

[0077] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0078] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0079] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way is inclusive and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range.

[0080] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0081] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0082] If not specifically stated, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.

[0083] Silicon-based materials are currently commonly used negative electrode active materials in the field of lithium battery technology. Due to their own characteristics, they have obvious volume expansion problems during the full charge and discharge process. During the research and development process, the inventors of this application found that the silicon-based materials have insufficient conductivity due to volume expansion. Therefore, when the inventors of this application use silicon-based materials as negative electrode active materials, they control the surface density and compaction density of the active material on the current collector to achieve the purpose of controlling the thickness of the negative electrode active material layer, and by reducing the migration distance of lithium ions during the charge and discharge process, improving the migration resistance of lithium ions during the charge and discharge process, and improving the conductivity of the negative electrode plate 10 by reducing the internal resistance, thereby ensuring the battery capacity. Under the premise of increasing the discharge rate of the battery as much as possible, the balance between the high capacity and high rate of the battery is achieved.

[0084] like Figure 1-Figure 3 As shown, it is a schematic diagram of the structure of a negative electrode sheet 10 provided by the present invention. In the present invention, the length direction of the negative electrode sheet 10 itself is defined as X, the width direction is defined as Y, and the thickness direction is defined as Z. It should be understood that the above definition of the direction is for the purpose of convenient description of the present invention, and the direction defined in the present invention can be understood according to the relative position of the attached figure and the actual product. It can be understood that the length direction, width direction and thickness direction of the negative electrode current collector 11 and the negative electrode silicon-based active material itself are the same as those of the negative electrode sheet 10. Figure 1 and Figure 2 The negative electrode sheet 10 in one embodiment of the present invention is shown along its length direction X. Figure 3 The figure shows the negative electrode sheet 10 along its thickness direction Z in one embodiment of the present invention.

[0085] like Figure 1 As shown, the negative electrode plate 10 provided by the present invention includes a negative electrode current collector 11, a negative electrode tab disposed on the negative electrode current collector 11, and a negative electrode silicon-based active material. The negative electrode current collector 11 includes a first surface 111 and a second surface 112 disposed along its thickness direction Z. The negative electrode silicon-based active material provided by the present invention is disposed on both the first surface 111 and the second surface 112 of the negative electrode current collector 11.

[0086] Among them, Figure 1As shown, the negative electrode silicon-based active material is coated on the first surface 111 of the negative electrode current collector 11 to form a first coated surface 111A and a first non-coated surface 111B. The first coated surface 111A with the negative electrode silicon-based active material is formed on the first surface 111, and the thickness D1 of the first coated surface 111A is the thickness of the active material formed after the negative electrode silicon-based active material is coated and rolled on the surface of the negative electrode current collector 11. The first non-coated surface 111B is also provided on the first surface 111. In the first non-coated surface 111B region of the first surface 111, there is no negative electrode silicon-based active material, and the first non-coated surface 111B is the surface of the negative electrode current collector 11 itself.

[0087] At the same time, if Figure 2 As shown, the negative electrode silicon-based active material is coated on the second surface 112 of the negative electrode current collector 11 to form a second coated surface 112A and a second non-coated surface 112B. A second coated surface 112A having a negative electrode silicon-based active material is formed on the second surface 112, and the thickness D2 of the second coated surface 112A is the thickness of the active material formed after the negative electrode silicon-based active material is coated and rolled on the surface of the negative electrode current collector 11. A second non-coated surface 112B is also provided on the second surface 112. In the second non-coated surface 112B region of the second surface 112, there is no negative electrode silicon-based active material. The second non-coated surface 112B is the surface of the negative electrode current collector 11 itself.

[0088] In order to better control the stability of the negative electrode silicon-based active material on the negative electrode current collector 11 during the battery cycle and improve the conductivity of the negative electrode silicon-based active material, the thickness D1 of the first coating surface 111A of the negative electrode plate 10 in the present invention is 20μm-35μm; the thickness D2 of the second coating surface 112A is 20μm-35μm. The thickness D1 (thickness D2) of the active material on the negative electrode plate 10 is controlled at 20μm-35μm, so that the thickness of the entire negative electrode plate 10 is greatly reduced compared with the thickness of the traditional negative electrode plate. The thickness of the negative silicon-based active material of the negative electrode plate 10 provided by the present invention disposed on the first surface 111 and the second surface 112 of the negative current collector 11 can be the same or different, that is, the thickness D1 of the first coating surface 111A and the thickness D2 of the second coating surface 112A can be the same, or the thickness D1 of the first coating surface 111A is greater than the thickness D2 of the second coating surface 112A, or the thickness D1 of the first coating surface 111A is smaller than the thickness D2 of the second coating surface 112A. The thickness D1 of the negative silicon-based active material on the first surface 111 or the thickness D2 of the negative silicon-based active material on the second surface 112 can be adjusted separately as needed, and the thickness of the negative silicon-based active material on the two surfaces can be adjusted separately, but the thickness of each single surface of the negative current collector 11 is still controlled between 20μm-35μm.

[0089] The thickness of the negative electrode plate 10 provided by the present invention is the sum of the thickness D1 of the first coating surface 111A, the thickness of the negative electrode collector 11 and the thickness D2 of the second coating surface 112A. In this embodiment, the negative electrode collector 11 adopts a copper foil with a thickness of 8μm. Therefore, the thickness of the negative electrode plate 10 provided by the present invention is between 48μm and 78μm. Compared with the thickness of the negative electrode plate made of the negative electrode active material used in the prior art, the overall thickness of the negative electrode plate 10 is reduced by 50%-70%. The negative electrode collector 11 can also use copper foil with a thickness of 10μm, 12μm, and 15μm. The thickness of the negative electrode collector 11 is not limited here and can be adjusted according to actual needs. The thickness of the negative electrode plate 10 provided by the present invention varies adaptively according to the different materials selected for the negative electrode collector 11.

[0090] If the thickness D1 or D2 of the single layer of the negative silicon-based active material on the first surface 111 or the second surface 112 of the negative current collector 11 is less than 20 μm, the single cell using the negative electrode plate 10 will not be able to meet the high capacity requirements of the battery, and the capacity of the single cell will be less than 3500 mAh. If the thickness D1 or D2 of the single layer of the negative silicon-based active material on the first surface 111 or the second surface 112 of the negative current collector 11 is higher than 35 μm, the resistance of the single cell using the negative electrode plate 10 is too large, and 6C rate discharge cannot be achieved. Therefore, by controlling the thickness D1 (thickness D2) of the negative silicon-based active material on both sides of the negative current collector 11 of the negative electrode plate 10, it is possible to achieve balanced control of the capacity and battery rate of the battery cell using the negative electrode plate 10.

[0091] In one embodiment, the gram capacity of the negative silicon-based active material in the negative electrode plate 10 provided by the present invention is ≥1200mAh / g. By selecting materials, material ratios, and controlling the processing technology, the gram capacity of the negative silicon-based active material is ≥1200mAh / g to ensure the energy density of the negative silicon-based active material. The negative silicon-based active material in the negative electrode plate 10 provided by the present invention serves as the main body of lithium storage in the battery, and realizes the embedding and de-embedding of lithium ions during the charging and discharging process. Therefore, the different selection of the negative silicon-based active material will directly affect the lithium storage capacity of the entire lithium-ion battery, that is, affect the capacity of the single cell. The single cell using the negative electrode plate 10 provided by the present invention increases the capacity of the single cell by controlling the gram capacity of the negative silicon-based active material in the single cell, and makes it reach a capacity greater than 3500mAh.

[0092] In one embodiment, in the negative electrode plate 10 provided by the present invention, the negative electrode silicon-based active material contains silicon element, which provides more lithium storage capacity for the negative electrode plate 10. The mass percentage of silicon element in the negative electrode silicon-based active material is 40-65%, for example, the mass percentage of silicon element in the negative electrode silicon-based active material is 40%, 45%, 50%, 55%, 60%, 65% or any value between any two of the above numerical ranges. The negative electrode silicon-based active material provided by the present invention can be selected from silicon-carbon materials, silicon oxide materials, or a composite material of silicon-carbon and graphite or a composite material of silicon oxide and graphite. When the negative electrode silicon-based active material is selected from silicon-carbon or silicon oxide, the mass percentage of silicon element in the negative electrode silicon-based active material is 50-65%. When the negative electrode silicon-based active material is selected from a silicon-based material (silicon-carbon or silicon oxide) and a graphite composite material, the mass percentage of silicon element in the negative electrode silicon-based active material is 40-55%.

[0093] In one embodiment, the unit area density of the negative electrode sheet 10 is 4.0-4.5 mg / cm 2 For example, the unit area density of the negative electrode sheet 10 is 4.0 mg / cm 2 , 4.1mg / cm 2 4.2mg / cm 2 , 4.3mg / cm 2 4.4mg / cm 2 , 4.5mg / cm 2 Or any value between any two of the above numerical ranges. By controlling the unit surface density of the negative electrode plate 10, the lithium storage capacity of the negative silicon-based active material is regulated, so that the negative electrode plate 10 using the negative silicon-based active material can have a higher active material content, and the single battery using the negative electrode plate 10 can have a higher battery capacity.

[0094] The unit area density of the negative electrode plate 10 mentioned in the present invention refers to the mass of a certain thickness of negative electrode silicon-based active material per unit area (the ratio of the mass and area of ​​the negative electrode silicon-based active material). The method for measuring the unit area density of the negative electrode plate 10 is as follows: Step 1. Use a sampler to take a circular foil of a preset area on an empty foil and weigh it to obtain the weight of the foil; Step 2. Use a sampler to take a circular electrode of the same size on a double-sided coated electrode and weigh it, and subtract the foil weight in step 1 and divide it by the circular area to obtain the double-sided area density; Steps 1-2 can be repeated to obtain the actual area density at different positions of the negative electrode plate 10 and then take the average value.

[0095] When the unit area density of the negative electrode sheet 10 is greater than 4.5 mg / cm 2When the unit surface density of the negative electrode silicon-based active material is greater, the material processing is more difficult, and the internal resistance of the negative electrode plate 10 is increased, and the rate performance is reduced. When the unit surface density of the negative electrode plate 10 is less than 4.0 mg / cm 2 When the negative electrode silicon-based active material has a small surface density, the material's lithium storage capacity is insufficient, the energy density is reduced, and it cannot meet the needs of batteries with high capacity requirements. In this embodiment, the unit surface density of the negative electrode plate 10 is 4.2 mg / cm 2 .

[0096] In one embodiment, the compaction density of the negative electrode sheet 10 is 0.6-1.0 g / cm 3 For example, the compaction density of the negative electrode sheet 10 is 0.6 g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 Or any value between any two of the above numerical ranges. By controlling the compaction density of the negative electrode plate 10, the porosity, effective pore size and other parameters of the negative electrode plate 10 can be controlled to improve the electronic and ion conductivity of the negative electrode plate 10. If the compaction density of the negative electrode plate 10 is too large, it is easy to cause excessive stress in the negative electrode plate 10, and the internal particles of the negative silicon-based material are broken, affecting the performance of the plate; if the compaction density of the negative electrode plate 10 is too small, the gap inside the active material is too large, which increases the resistance and affects the ion transmission rate. The compaction density is adaptively adjusted according to the different selection of silicon-based materials in the negative silicon-based active material. When the negative silicon-based active material of the negative electrode plate 10 uses silicon-carbon material as the main negative electrode material, the compaction density of the negative electrode plate 10 is controlled at 0.8g / cm 3 It is relatively ideal, so that the thickness D1 of the negative electrode silicon-based active material on the first coating surface 111A and the thickness D2 of the second coating surface 112A can be effectively controlled, so that the thickness can be controlled within the designed size range and can meet the battery requirements of high capacity and high rate; when the negative electrode silicon-based active material of the negative electrode plate 10 is selected to use silicon oxide as the main negative electrode material, the compaction density of the negative electrode plate 10 is controlled to be 1.0 / cm 3 It is ideal to control the thickness within the designed size range and meet the battery requirements of high capacity and high rate.

[0097] The inventors of the present application utilize the principle of interaction between the compaction density and unit area density of the negative electrode plate 10, and control the thickness of the negative electrode silicon-based active material on the negative electrode current collector 11 by regulating the compaction density and unit area density of the negative electrode plate 10, so as to achieve balanced regulation of the conductivity, lithium storage performance and rate performance of the negative electrode plate 10. In this embodiment, the compaction density of the negative electrode plate 10 is 0.8 g / cm 3 At the same time, the unit area density of the negative electrode sheet 10 is 4.2 mg / cm 2 , so that the thickness D1 of the first coating surface 111A of the first surface 111 of the negative electrode collector 11 and the thickness D2 of the second coating surface 112A of the second surface 112 of the negative electrode plate 10 provided by the present invention can be controlled between 20μm-35μm, which can meet the energy density and rate performance, that is, meet the high-capacity battery requirements and achieve high-rate charge and discharge performance, so that the negative electrode plate 10 using the above-mentioned negative silicon-based active material can achieve a relative balance in battery capacity and battery rate. Under the premise that the unit surface density of the negative electrode plate 10 remains unchanged, the greater the compaction density, the smaller the thickness D1 of the first coating surface 111A (the thickness D2 of the second coating surface 112A), and conversely, the smaller the compaction density, the greater the thickness D1 of the first coating surface 111A (the thickness D2 of the second coating surface 112A).

[0098] When the compaction density of the negative electrode sheet 10 is greater than 1.0 g / cm 3 When the compaction density of the negative electrode sheet 10 is less than 0.6 g / cm 3 When the negative electrode silicon-based active material is loosely stacked, the layer thickness increases, which is not conducive to the cyclic migration of lithium ions during battery charging and discharging, the internal resistance of the negative electrode plate 10 increases, and the conductive performance decreases.

[0099] In the negative electrode plate 10 provided by the present invention, the area of ​​the first coated surface 111A of the first surface 111 of the negative electrode plate 10 is greater than the area of ​​the second coated surface 112A of the second surface 112. During the winding process of the battery cell, the second surface 112 is located on the outside of the winding, and the first surface 111 is located on the inside of the winding, that is, the first coated surface 111A faces the side of the positive electrode plate 20, and the second coated surface 112A faces the side of the shell 50. Therefore, in order to ensure that the active material layer between the positive electrode sheet 20 and the negative electrode sheet 10 can fully utilize the spatial interaction when they are wound, the surface area of ​​the active material layer on the first surface 111 located on the inner side of the winding (the first coating surface 111A) should be fully utilized, and the active material layer on the second surface 112 located on the outer side of the winding, when winding, the circle located at the end of the winding is opposite to the steel shell. For cost saving and other considerations, the second surface 112 near the end of the winding does not need to be coated with active material, so the area of ​​the first coating surface 111A is larger than the area of ​​the second coating surface 112A.

[0100] In one embodiment, the area of ​​the first coating surface 111A is 1.05-1.1 of the area of ​​the second coating surface 112A. For example, in the negative electrode plate 10, the area of ​​the first coating surface 111A is 1.05, 1.06, 1.07, 1.08, 1.09, 1.1 or any value between any two of the above numerical ranges of the area of ​​the second coating surface 112A. Figure 1 and Figure 2 As shown, the negative electrode silicon-based active material coated on the first surface 111 and the second surface 112 of the negative electrode plate 10 has the same size in the width direction Y, and both completely coat the width direction of the negative electrode current collector 11. The size of the negative electrode silicon-based active material in the length direction X on the first surface 111 is different from the size of the negative electrode silicon-based active material in the length direction X on the second surface 112. The size coated on the first surface 111 is larger than the size coated on the second surface 112, and the area of ​​the first coating surface 111A is controlled to be between 1.05-1.1 of the area of ​​the second coating surface 112A. By controlling the difference in the coating area of ​​the negative electrode plate 10 on the first surface 111 and the second surface 112, on the one hand, the negative electrode silicon-based active material can be saved, and on the other hand, the assembly ratio can be regulated by adjusting the two coating areas. If the ratio of the area of ​​the first coating surface 111A to the area of ​​the second coating surface 112A exceeds 1.1, the coating area of ​​the first coating surface 111A increases, and the area of ​​the coating edge will be opposite to the steel shell at the shelling location after shelling, and will not interact with the positive electrode plate 20, resulting in excessive coating material, which is not conducive to cost control. If the ratio of the area of ​​the first coating surface 111A to the area of ​​the second coating surface 112A is lower than 1.05, the purpose of regulating the assembly ratio cannot be achieved.

[0101] At the same time, in order to improve the conductivity of the negative electrode plate 10 provided by the present invention, the negative electrode plate 10 provided by the present invention can adopt a double-ear structure design or a multi-ear structure design to improve the conductivity of the negative electrode plate 10.

[0102] In one embodiment, if Figure 1-Figure 3 As shown, in this embodiment, the negative electrode plate 10 adopts a bipolar ear structure design. The negative electrode ear on the negative electrode plate 10 includes a first ear 12 and a second ear 13. The bipolar ear structure design can further improve the discharge rate of the battery cell using the negative electrode plate 10, thereby meeting the requirements of high rate (3C / 6C discharge).

[0103] like Figure 1 and Figure 2 As shown, in this embodiment, the first pole tab 12 and the second pole tab 13 of the negative electrode plate 10 are arranged at intervals in the length direction X of the negative electrode current collector 11 and are respectively located on the first non-coated surface 111B and the second non-coated surface 112B. That is, the first pole tab 12 and the second pole tab 13 are located on different surfaces in the thickness direction Z of the negative electrode current collector 11, and during the winding process of the negative electrode plate 10, the second pole tab 13 is located at the front end of the winding, and the first pole tab 12 is located at the rear end of the winding. When the winding is completed, the second pole tab 13 is located at the center of the winding core, and the first pole tab 12 is located at the periphery of the winding core. The negative electrode plate 10 adopts a double-pole ear design and controls the thickness of the negative electrode silicon-based active material coated on both sides of the negative electrode current collector 11, which can reduce the path of lithium ion migration inside the negative electrode plate 10 and reduce the internal resistance of the negative electrode plate 10, thereby achieving the purpose of increasing the current of the negative electrode plate 10, and further improving the conductive performance of the negative electrode plate 10, so that the single cell using the negative electrode plate 10 of the present invention can achieve high rate (3C / 6C) discharge.

[0104] like Figure 1 and Figure 2 As shown, the negative electrode current collector 11 provided by the present invention has two first side edges 113 and a second side edge 114 arranged parallel to each other along the width direction Y. The first pole tab 12 and the second pole tab 13 in the negative electrode electrode sheet 10 provided by the present invention are arranged perpendicular to the first side edge 113 of the negative electrode current collector 11. The first pole tab 12 is arranged on the second surface 112, and the second pole tab 13 is arranged on the first surface 111. The first pole tab 12 and the second pole tab 13 are respectively located on different surfaces of the negative electrode current collector 11.

[0105] Specifically, the first pole tab 12 includes a first conductive sheet 121 welded to the second non-coated surface 112B and extending outward from the first side 113. The first conductive sheet 121 is fixed to the second non-coated surface 112B of the second surface 112 of the negative electrode current collector 11 by ultrasonic welding, and is fixedly connected and electrically connected to the negative electrode current collector 11 by welding to form a first ultrasonic weld mark 121A. The first pole tab 12 is the main current passage on the negative electrode pole sheet 10 provided by the present invention. The first pole tab 12 is located at the end of the winding of the negative electrode pole sheet 10. When winding, the first pole tab 12 is located at the outer end of the winding core.

[0106] The first electrode tab 12 in the negative electrode plate 10 provided by the present invention further includes two first insulating sheets 122 respectively attached to the first non-coated surface 111B and the second non-coated surface 112B and extending outward from the first side 113. The two first insulating sheets 122 are respectively located on the first surface 111 and the second surface 112 of the negative electrode current collector 11, and the two first insulating sheets 122 are both located on the blank area not coated by the negative electrode silicon-based active material, and the two first insulating sheets 122 completely cover all areas of the first conductive sheet 121 on the negative electrode current collector 11. Figure 1 and Figure 2 As shown, the projection surfaces of the two first insulating sheets 122 on the negative electrode current collector 11 overlap with each other, and the first conductive sheet 121 is located between the two first insulating sheets 122. The first insulating sheet 122 is made of polyimide (PI) material, and the first conductive sheet 121 is completely covered in the area of ​​the negative electrode current collector 11 by pasting, so as to prevent the first conductive sheet 121 from contacting and short-circuiting with the positive electrode sheet 20 during the winding process. To ensure that the two pasted first insulating sheets 122 can completely cover the first conductive sheet 121, the width A2 of the first insulating sheet 122 is 1.5-2.5 times the width A1 of the first conductive sheet 121. Generally speaking, in order to meet the overcurrent requirements of the tab, the width A1 of the first conductive sheet 121 is 3mm-6mm, and correspondingly, the width A2 of the first insulating sheet 122 is between 4.5mm-15mm. In this embodiment, the first conductive sheet 121 uses a copper-plated nickel tab with a width of 4mm. The first insulating sheet 122 is made of PI electrode protection tape with a width of 8 mm.

[0107] In one embodiment, in order to ensure that the first conductive sheet 121 will not short-circuit when the first pole tab 12 is wound on the negative electrode sheet 10, the length H1 of the first insulating sheet 122 extending outward along the first side 113 is 0.5mm-3mm. If the length H1 is less than 0.5mm, the first conductive sheet 121 is likely to touch the positive electrode collector 21 or the negative electrode collector 11 during winding and cause a short circuit. If the length H1 is greater than 3mm, it is not conducive to the electrical connection between the first pole tab 12 and the second pole tab 13. In this embodiment, the length H1 of the first insulating sheet 122 extending outward is 1mm, which can ensure that the first conductive sheet 121 is insulated from the current collector when winding, and will not hinder the electrical connection between the first conductive sheet 121 and the second pole tab 13.

[0108] In the negative electrode plate 10 provided by the present invention, the first conductive sheet 121 is located at the end of the winding of the negative electrode plate 10, so the distance L1 between the first conductive sheet 121 and the side of the second coating surface 112A is 45mm-65mm. The distance L1 between the first conductive sheet 121 and the side of the second coating surface 112A is roughly the outer diameter of the outermost circle when the battery cell is wound, which defines the distance L1 between the first conductive sheet 121 and the second coating surface 112A. The distance L1 is related to the thickness (D1 and / or D2) of the active material layer on the negative electrode plate 10. The greater the thickness (D1 and / or D2) of the active material layer of the negative electrode plate 10, the greater the distance L1, and conversely, the smaller the thickness (D1 and / or D2) of the active material layer of the negative electrode plate 10, the smaller the distance L1. By controlling the distance L1, the first pole tab 12 is located at the end of the negative electrode sheet 10, and the edge of the coating area of ​​the second coating surface 112A is determined, so as to ensure that the second surface 112 of the last circle is as close to the second non-coating surface 112B as possible when the negative electrode sheet 10 is wound in the last circle. In this embodiment, the distance L1 between the first conductive sheet 121 and the side of the second coating surface 112A is 55 mm.

[0109] In one embodiment, if Figure 1 As shown, the second pole tab 13 is a second conductive sheet 131 welded on the first coating surface 111A and extending outward from the first side 113. The second conductive sheet 131 is welded and fixed to the negative electrode current collector 11 to form a second ultrasonic weld mark 131A. The second pole tab 13 is located at the front end of the negative electrode plate 10 when it is wound. The second pole tab 13 is an auxiliary pole tab added to the negative electrode plate 10 provided by the present invention to increase the overcurrent. After winding, the second conductive sheet 131 will be directly fixedly connected to the first conductive sheet 121 by welding to achieve electrical connection.

[0110] In one embodiment, the width A3 of the second conductive sheet 131 in the negative electrode plate 10 provided by the present invention is 0.5-1 of the width A1 of the first conductive sheet 121. If the width A3 of the second conductive sheet 131 is too small, the overcurrent requirement of the discharge rate cannot be met, and the sum of the current between the first conductive sheet 121 and the second conductive sheet 131 cannot meet the high-rate charge and discharge requirements of the negative electrode plate 10. If the width A3 of the second conductive sheet 131 is too large, it exceeds the rate requirement and is not conducive to cost control. In this embodiment, the first conductive sheet 121 uses a copper-plated nickel tab with a width of 4 mm. The second conductive sheet 131 uses a copper-plated nickel tab with a width of 3 mm. The width A3 of the second conductive sheet 131 is 0.75 of the width A1 of the first conductive sheet 121.

[0111] In order to ensure the stability of the electrical connection of the bipolar ear structure in the negative electrode plate 10, the length of the first conductive sheet 121 extending outward along the first side 113 in the negative electrode plate 10 provided by the present invention is A, and the length of the second conductive sheet 131 extending outward along the first side 113 is B. The length relationship between the two should meet the following conditions: A>B and AB>8mm. The first conductive sheet 121 is located outside the winding core after winding, and the second conductive sheet 131 is located in the center of the winding core. It is necessary to weld the second conductive sheet 131 to the first conductive sheet 121 first, and then weld and fix the first conductive sheet 121 to the shell 50 to achieve electrical connection. Therefore, in order to ensure the stability of the welding between the first conductive sheet 121 and the second conductive sheet 131. The length of the first conductive sheet 121 extending out of the negative electrode current collector 11 is A. In this embodiment, A is 16mm. The length of the second conductive sheet 131 extending out of the negative electrode current collector 11 is B. In this embodiment, B is 6mm. The extended length A of the first conductive sheet 121 is greater than the extended length B of the second conductive sheet 131, and the difference in the extended distance between the two is 10 mm, so as to ensure that the first pole tab 12 and the second pole tab 13 have enough overlapping space for welding and fixing.

[0112] like Figure 1 As shown, the distance L2 between the second conductive sheet 131 and the side of the first coated surface 111A is 15 mm-20 mm. The distance L2 is used to determine the starting position of the first coated surface 111A located on the first surface 111, and to reserve enough space for the first insulating sheet 122 of the first tab 12 to be attached. In this embodiment, the distance L2 between the second conductive sheet 131 and the side of the first coated surface 111A is 17 mm.

[0113] In one embodiment, the negative electrode plate 10 provided by the present invention can also adopt a multi-pole ear structure design. The negative electrode ear on the negative electrode plate 10 includes a main pole ear (not shown in the figure) arranged on the first non-coated surface 111B or the second non-coated surface 112B and a plurality of auxiliary pole ears (not shown in the figure) arranged on the first non-coated surface 111B and / or the second non-coated surface 112B, and the plurality of auxiliary pole ears are arranged at intervals along the length direction Y of the negative electrode collector 11. The multi-pole ear structure design of the negative electrode plate 10 provided by the present invention can further improve the discharge rate of the battery cell using the negative electrode plate 10, thereby meeting the requirements of high rate (3C / 6C discharge) or even ultra-high rate (9C).

[0114] In one embodiment, when the negative electrode sheet 10 provided by the present invention adopts a multi-electrode tab structure design, the main electrode tab and the plurality of auxiliary electrode tabs all extend outward based on the negative electrode current collector 11, and the main electrode tab and the plurality of auxiliary electrode tabs extend outward based on the negative electrode current collector 11 in the same direction, that is, the main electrode tab and the plurality of auxiliary electrode tabs all extend toward one side of the width direction of the negative electrode current collector 11. When the negative electrode sheet 10 provided by the present invention is wound into a cylindrical winding core, the plurality of auxiliary electrode tabs and the main electrode tab are located on the same side of the negative electrode current collector 11.

[0115] In one embodiment, the negative electrode plate 10 provided by the present invention adopts a multi-pole ear structure design, in which the length of the main pole ear extending outward based on the negative electrode current collector 11 is greater than the length of the secondary pole ear extending outward based on the negative electrode current collector 11, that is, the length of the main pole ear outside the negative electrode current collector 11 is greater than the length of the secondary pole ear outside the negative electrode current collector 11. After the negative electrode plate 10 is wound, all the secondary pole ears are stacked on each other and then aligned with the main pole ears, and are fixed together by ultrasonic welding to form a negative electrode ear, and then fixedly connected to the battery shell 50 through the negative electrode ear.

[0116] A negative electrode plate 10 provided by the present invention controls the thickness of the negative electrode silicon-based active material on the negative electrode current collector 11 by controlling the surface density and compaction density of the negative electrode plate 10, thereby reducing the adverse effects of the negative electrode silicon-based active material due to expansion during charging and discharging, and reducing the thickness of the dressing as much as possible while ensuring the lithium storage capacity of the negative electrode plate 10, so as to reduce the migration distance of lithium ions during charging and discharging, improve the migration resistance of lithium ions during charging and discharging, reduce the internal resistance of the negative electrode plate 10, and achieve the purpose of increasing the current. Combined with the structural design of the negative electrode bipolar ear or multi-polar ear, the conductive performance of the negative electrode plate 10 is improved.

[0117] In a second aspect, the present invention also provides a cylindrical battery 100. Figure 4As shown, it is a schematic diagram of the three-dimensional structure of the cylindrical battery 100 provided by the present invention. The cylindrical battery 100 provided by the present invention includes a shell 50, a cap 40, an electrolyte and a cylindrical winding core arranged in the shell 50. The shell 50 is a steel shell with a cylindrical structure that passes through from top to bottom, and the cylindrical winding core and the electrolyte are both arranged inside the shell 50. The cap 40 is located at the top of the shell 50 in the length direction, and is used to seal the upper and lower openings of the shell 50. Among them, the cap 40 is electrically connected to the positive electrode tab 22 of the positive electrode sheet 20, and the negative electrode tab of the negative electrode sheet 10 is electrically connected to the end of the shell 50.

[0118] Furthermore, if Figure 4 As shown, the cylindrical winding core includes a positive electrode sheet 20, a separator 30 and the above-mentioned negative electrode sheet 10. The cylindrical battery 100 provided by the present invention adopts the above-mentioned negative electrode sheet 10. In this embodiment, the negative electrode sheet 10 adopts a bipolar ear structure design, and the second pole ear 13 of the wound negative electrode sheet 10 is welded to the first pole ear 12, and is welded and fixed to the shell 50 through the first pole ear 12. Before the first pole ear 12 and the second pole ear 13 on the negative electrode sheet 10 are fixed to the shell 50, the two are first fixed by ultrasonic welding to form a negative pole ear, and then welded and fixed to the shell 50 by resistance welding.

[0119] The cylindrical core of the cylindrical battery 100 provided by the present invention is assembled in the shell 50, and the diameter of the cylindrical core is 0.96-0.99 of the inner diameter of the shell 50. The larger the ratio of the diameter of the core to the inner diameter of the shell 50, the larger the assembly ratio of the cylindrical battery 100. The structural strength of the cylindrical core can be improved by increasing the assembly ratio, thereby improving the mechanical properties of the negative electrode sheet 10 and the positive electrode sheet 20 in the cylindrical core during formation and battery charge and discharge cycles. In the cylindrical battery 100 provided by the present invention, the ratio between the diameter of the cylindrical core and the inner diameter of the shell 50 is the ratio between the cylindrical core and the shell 50 that has not been formed. During the battery processing, after the cylindrical core is loaded into the shell 50, the cylindrical battery 100 is sealed and formed, and the negative electrode sheet 10 and the positive electrode sheet 20 of the cylindrical core will expand.

[0120] In one embodiment, the cylindrical battery 100 provided by the present invention further includes a positive electrode sheet 20. Figure 5 , which is a schematic structural diagram of the positive electrode sheet 20 provided in the cylindrical battery 100 provided by the present invention. The positive electrode sheet 20 includes a positive electrode current collector 21, a positive electrode tab 22 disposed on the positive electrode current collector 21, and a positive electrode active material.

[0121] The positive electrode current collector 21 in the positive electrode plate 20 provided by the present invention includes a third surface 211 and a fourth surface 212 arranged along its thickness direction Z; the positive electrode active material is arranged on the third surface 211 and the fourth surface 212, that is, the positive electrode active material is respectively located on two opposite surfaces of the positive electrode current collector 21. The positive electrode active material in the positive electrode plate 20 provided by the present invention is a LiNi x Co y Mn 1-x-y O2 material (where x,y values ​​range from 0-1).

[0122] In one embodiment, the unit area density of the positive electrode sheet 20 is 28-33 mg / cm 2 For example, the unit area density of the positive electrode sheet 20 is 28 mg / cm 2 , 29mg / cm 2 、30mg / cm 2 、31mg / cm 2 、32mg / cm 2 、33mg / cm 2 Or any value between any two of the above numerical ranges. By controlling the unit area density of the positive electrode sheet 20, the battery capacity of the single battery can be regulated. When the unit area density of the positive electrode sheet 20 is greater than 33 mg / cm 2 When the unit surface density of the positive electrode sheet 20 is too large, the assembly ratio is greater than 1, making the designed battery size larger than the size of the cylindrical battery 100 steel shell. 2 When the assembly ratio is too low, the utilization rate of the internal space of the steel shell of the cylindrical battery 100 is insufficient. In this embodiment, the unit area density of the positive electrode sheet 20 is 30 mg / cm 2 , so that the positive electrode sheet 20 using the above-mentioned positive electrode active material and the cylindrical battery 100 provided by the present invention have a larger capacity.

[0123] In one embodiment, the compaction density of the positive electrode sheet 20 is 3.2-3.8 g / cm 3 For example, the compaction density of the positive electrode sheet 20 is 3.2 g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 、3.5g / cm 3 、3.6g / cm 3 、3.7g / cm 3 、3.8g / cm 3Or any value between any two of the above numerical ranges. By controlling the compaction density of the positive electrode sheet 20, the thickness of the active material layer on the positive electrode sheet 20 can be controlled. If the compaction density of the positive electrode sheet 20 is too large, on the one hand, it will reduce the absorption capacity of the electrolyte, thereby affecting the capacity of the battery, and on the other hand, it will limit the rapid transmission capacity of lithium ions. If the compaction density of the positive electrode sheet 20 is too small, it will reduce the overall energy density of the single cell and cannot meet the demand for high capacity.

[0124] In one embodiment, the positive electrode active material of the cylindrical battery 100 provided by the present invention is coated on the third surface 211 of the positive current collector 21 to form a plurality of third coating surfaces 211A, and a first blank area 211B is formed between two adjacent third coating surfaces 211A. The positive electrode active material is coated on the fourth surface 212 of the positive current collector 21 to form a plurality of fourth coating surfaces 212A, and a second blank area 212B is formed between two adjacent fourth coating surfaces 212A. The number of the third coating surfaces 211A and the fourth coating surfaces 212A on the positive current collector 21 is related to the arrangement of the positive electrode tab 22, that is, the first blank area 211B formed between two adjacent third coating surfaces 211A and the second blank area 212B formed between two adjacent fourth coating surfaces 212A are both used to arrange the positive electrode tab 22. The positive electrode tab 22 adopts a single-pole tab, a bipolar tab or a multi-pole tab structure design, which is determined by the actual needs of the cylindrical battery 100 provided by the present invention.

[0125] In one embodiment, the thickness D3 of the third coating surface 211A in the positive electrode sheet 20 of the cylindrical battery 100 provided by the present invention is the thickness formed on the positive current collector 21 after the positive active material is coated and rolled. The thickness of the third coating surface 211A on the positive electrode sheet 20 is 35μm-55μm. The first blank area 211B is a non-coated area, that is, the surface of the positive current collector 21 itself. In addition, the positive active material is coated on the fourth surface 212 of the positive current collector 21 to form two fourth coating surfaces 212A, and a second blank area 212B is formed between the two fourth coating surfaces 212A. The two fourth coating surfaces 212A are symmetrically arranged on both sides of the second blank area 212B, and the thickness D4 of the fourth coating surface 212A is 35μm-55μm. The structures on the third surface 211 and the fourth surface 212 of the positive electrode sheet 20 are the same. The thickness D4 of the fourth coating surface 212A is the thickness formed on the positive electrode current collector 21 after the positive electrode active material is coated and rolled. The thickness D3 of the third coating surface 211A and the thickness D4 of the fourth coating surface 212A may be the same or different, and the thickness may be adjusted according to actual needs, but the thickness D3 of the third coating surface 211A and the thickness D4 of the fourth coating surface 212A are both controlled within a range of 35 μm to 55 μm.

[0126] In the cylindrical battery 100 provided by the present invention, the thickness of the positive electrode plate 20 is the sum of the thickness D3 of the third coating surface 211A and the thickness D4 of the fourth coating surface 212A, and the thickness of the positive electrode collector 21. In this embodiment, the positive electrode collector 21 adopts an aluminum foil with a thickness of 15μm. Therefore, in the cylindrical battery 100 provided by the present invention, the thickness of the positive electrode plate 20 is between 85μm and 125μm. The positive electrode collector 21 can also use aluminum foil with a thickness of 10μm, 12μm, or 20μm. The thickness of the positive electrode collector 21 is not limited here and can be adjusted according to actual needs. The thickness of the positive electrode plate 20 provided by the present invention varies according to the different material selection of the positive electrode collector 21.

[0127] If the thickness D3 (thickness D4) of the positive electrode active material on the positive electrode current collector 21 is less than 35 μm, the high capacity requirement of the battery cannot be met. If the thickness D3 (thickness D4) of the positive electrode active material on the positive electrode current collector 21 is greater than 55 μm, the positive electrode plate 20 will reduce the effective utilization rate of the positive electrode active material, affecting the charge and discharge efficiency of the battery, and the electrolyte cannot penetrate into the plate, causing the electrochemical reaction rate to decrease, thereby reducing the actual capacity of the single battery.

[0128] In one embodiment, if Figure 5 As shown, in the cylindrical battery 100 provided by the present invention, the positive electrode current collector 21 has two third sides 213 and a fourth side 214 arranged parallel to each other along the width direction Y. When winding, the third side 213 of the positive electrode current collector 21 and the second side 114 of the negative electrode current collector 11 are located on the same side, and the fourth side 214 of the positive electrode current collector 21 and the first side 113 of the negative electrode current collector 11 are located on the same side.

[0129] In one embodiment, the positive electrode tab 22 of the positive electrode tab 20 in the cylindrical battery 100 provided by the present invention includes a plurality of third conductive sheets 221 welded on the first blank area 211B and extending outward from the third side 213. The number of third conductive sheets 221 in the positive electrode tab 22 is determined according to the actual current over-current requirement of the cylindrical battery 100. The positive electrode tab 20 provided by the present invention also includes a plurality of pairs of second insulating sheets 222 respectively attached to the first blank area 211B and the second blank area 212B and extending outward from the third side. The second insulating sheets 222 appear in pairs, and the projection surfaces of each pair of second insulating sheets 222 on the positive current collector 21 overlap with each other, and the third conductive sheet 221 is located between a pair of second insulating sheets 222. A pair of second insulating sheets 222 are respectively arranged on the third surface 211 and the fourth surface 212 of the positive current collector 21, and the second insulating sheets 222 completely cover the first blank area 211B or the second blank area 212B. The number of second insulating sheets 222 on the positive electrode sheet 20 is related to the number of third conductive sheets 221, and a pair of second insulating sheets 222 cooperates with one third conductive sheet 221. Each pair of second insulating sheets 222 is attached to one third conductive sheet 221, and the connection between the third conductive sheet 221 and the positive current collector 21 is covered from both side surfaces of the positive current collector 21.

[0130] In this embodiment, if Figure 5 As shown, the third surface 211 is provided with two third coating surfaces 211A and a first blank area 211B; the two third coating surfaces 211A are symmetrically arranged on both sides of the first blank area 211B. That is, the first blank area 211B is located between the two third coating surfaces 211A, and the two third coating surfaces 211A have the same structure. Correspondingly, in this embodiment, the fourth surface 212 is provided with two fourth coating surfaces 212 A and a second blank area 212B, and the two fourth coating surfaces 212 A are symmetrically arranged on both sides of the second blank area 212B. That is, the first blank area 211B is located between the two fourth coating surfaces 212 A, and the two second blank areas 212B have the same structure.

[0131] In this embodiment, the third conductive sheet 221 of the positive electrode sheet 20 in the cylindrical battery 100 is first welded and fixed to the positive current collector 21 by ultrasonic welding to form a third ultrasonic weld mark 221A, and then a pair of second insulating sheets 222 are attached from the two sides of the positive current collector 21 to the blank area of ​​the positive current collector 21, and the two uncoated areas of the positive current collector 21 are completely covered by the pair of second insulating sheets 222. In this embodiment, the second insulating sheet 222 is selected from an insulating tape with a width of 10 mm. And, as Figure 5As shown, in the present embodiment, the positive electrode plate 20 adopts a single-ear structure, and the ear in the positive electrode plate 20 is centrally located, that is, the positive electrode ear 22 on the positive electrode plate 20 is located at the center of the positive electrode collector 21. After winding, the positive electrode ear 22 of the positive electrode plate 20 is welded and fixed to the cap 40. The positive electrode plate 20 is only provided with one ear, and the ear is directly fixedly connected to the cap 40 by laser welding.

[0132] The width of the positive electrode tab 22 of the positive electrode sheet 20 provided by the present invention is the same as the width of the negative electrode tab of the negative electrode sheet 10. That is, the width A4 of the third conductive sheet 221 in the positive electrode sheet 20 is the same as the width A1 of the first conductive sheet 121 in the negative electrode sheet 10. In this embodiment, the third conductive sheet 221 in the positive electrode sheet 20 uses an aluminum tab with a width of 4 mm. The tab width A4 of the third conductive sheet 221 of the positive electrode sheet 20 is the same as the tab width A1 of the first conductive sheet 121 of the negative electrode tab to meet the high battery current requirements of the cylindrical battery 100.

[0133] In order to meet the requirement of welding and fixing the positive electrode tab 22 and the positive electrode current collector 21, the width of the first blank area 211B and the second blank area 212B is at least 2 mm larger than the width of the positive electrode tab 22. The width A5 of the first blank area 211B and the second blank area 212B of the positive electrode sheet 20 is 7 mm, which is 3 mm larger than the third conductive sheet 221, and 1.5 mm is reserved on both sides of the positive electrode tab 22.

[0134] In one of the embodiments, in order to ensure that the positive electrode tab 22 does not contact the negative electrode tab 10 and cause problems such as short circuit when the positive electrode tab 20 is wound, the area of ​​the second insulating sheet 222 is larger than the area of ​​the first blank area 211B or the second blank area 212B of the positive electrode collector 21. That is, the width A6 of the second insulating sheet 222 is larger than the width A5 of the first blank area 211B. In addition, the width A6 of the second insulating sheet 222 should be larger than the width of the second blank area 212B. Specifically, the width A6 of the second insulating sheet 222 is 2mm-5mm larger than the width A5 of the first blank area 211B. In this embodiment, the width A6 of the second insulating sheet 222 is 10mm, and the width A5 of the first blank area 211B is 7mm.

[0135] In one embodiment, the second insulating sheet 222 in the positive electrode sheet 20 extends from the third side 213 and the fourth side 214 of the positive electrode current collector 21, respectively, wherein the length C of the second insulating sheet 222 extending outward along the third side 213 is 2 mm-4 mm. Figure 5As shown, in this embodiment, the length C of the second insulating sheet 222 extending along the third side 213 is 2.5 mm. The length D of the second insulating sheet 222 extending outward along the fourth side 214 is 0.2 mm-1.0 mm. Figure 5 As shown, in this embodiment, the length D of the second insulating sheet 222 extending along the fourth side 214 is 0.5 mm.

[0136] In one embodiment, the first coated surface 111A of the negative electrode sheet 10 faces one side of the positive electrode sheet 20 during winding, and the length L3 of the first coated surface 111A is greater than the length L4 of the positive electrode collector 21 of the positive electrode sheet 20, so that the active material layer on the negative electrode sheet 10 can completely cover the active material layer of the positive electrode sheet 20 during winding.

[0137] In one embodiment, the length of the negative electrode sheet 10 in the cylindrical battery 100 provided by the present invention is 1190mm-1205mm; for example, the length of the negative electrode sheet 10 of the cylindrical battery 100 provided by the present invention is 1190mm, 1193mm, 1195mm, 1196mm, 1198mm, 1200mm, 1202mm, 1204mm, 1105mm, or any value between any two of the above numerical ranges. In one embodiment, the length of the positive electrode sheet 20 in the cylindrical battery 100 provided by the present invention is 1081mm-1091mm; for example, the length of the positive electrode sheet 20 of the cylindrical battery 100 provided by the present invention is 1181mm, 1183mm, 1185mm, 1186mm, 1188mm, 1190mm, 1191mm, or any value between any two of the above numerical ranges. The capacity ratio (N / P ratio) of the positive electrode sheet 20 and the negative electrode sheet 10 in the cylindrical battery 100 provided by the present invention is 1.03-1.05. The lengths of the negative electrode sheet 10 and the positive electrode sheet 20 in the cylindrical battery 100 provided by the present invention meet the casing size of the 18650 battery and can be applied to the requirements of the 18650 cylindrical battery 100.

[0138] In one embodiment, the amount of electrolyte injected is 5.6g-6.2g. For example, the amount of electrolyte injected in the cylindrical battery 100 provided by the present invention is 5.6g, 5.7g, 5.8g, 5.9g, 6.0g, 6.1g, 6.2g or any value between any two of the above numerical ranges. The amount of electrolyte injected is related to the assembly ratio of the cylindrical battery 100. The assembly ratio of the cylindrical battery 100 provided by the present invention is 0.96-0.99. The higher the assembly ratio, the smaller the corresponding injection amount, and the lower the assembly ratio, the larger the corresponding injection amount. When the injection amount is less than 5.6g, the capacity of the cylindrical battery 100 will decrease. This is because insufficient electrolyte will cause the active material inside the battery to be unable to be fully utilized, the positive electrode capacity cannot be fully utilized, and lithium precipitation may occur at the negative electrode, thereby reducing the available capacity of the battery. When the injection amount is higher than 6.2g, during the charging and discharging process, the cap 40 will be flipped.

[0139] like Figure 7 As shown, the cylindrical battery 100 provided by the present invention is charged at 0.2C and discharged at 3C, with a discharge capacity retention rate greater than 97% and a temperature rise of 20-35°C. It is charged at 0.2C and discharged at 6C, with a discharge capacity retention rate greater than 95% and a temperature rise of 45-65°C.

[0140] A cylindrical battery 100 provided by the present invention adopts the above-mentioned negative electrode plate 10. Taking the 18650 cylindrical battery 100 as an example, by optimizing the structure, improving the system and the manufacturing process, the high capacity and high rate of the battery can be achieved at the same time to achieve an ideal state, and the battery energy density and power output capacity are significantly improved, providing the market with a more efficient and reliable energy solution, which has broad application prospects and market value; by adopting the above-mentioned negative electrode plate 10, the lithium ion capacity of the negative electrode plate 10 is increased, and the migration distance of lithium ions during the battery charge and discharge cycle is shortened, so that the cylindrical battery 100 maintains a capacity of more than 3500mAh, and when charged at 0.2C and discharged at 3C, the discharge capacity retention rate is greater than 97%, and the temperature rise is controlled at 20-35°C; when charged at 0.2C and discharged at 6C, the discharge capacity retention rate is greater than 95%, and the temperature rise is controlled at 45-65°C.

[0141] In addition, the present invention also provides a battery pack, comprising two or more of the above cylindrical batteries 100, wherein the two or more cylindrical batteries 100 are electrically connected in series or in parallel. The specific number of cylindrical batteries 100 included in the battery pack can be adaptively selected by those skilled in the art according to the actual application of the battery pack and the capacity of the battery.

[0142] A battery pack provided by the present invention adopts the above-mentioned high-capacity, high-rate cylindrical battery 100, so that the overall electrical performance of the battery pack is improved, and a high-capacity, high-rate battery pack is realized.

[0143] In addition, the present invention also provides an electric tool, including the above-mentioned battery pack. The electric tool includes at least one of the cylindrical battery 100 or battery pack provided by the present invention. The cylindrical battery 100 or battery pack can be used as a power source for the electric tool, and can also be used as an energy storage unit for the electric tool. The electric tool includes but is not limited to: mobile devices (such as mobile phones, tablet terminals, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric trucks, electric golf carts, electric scooters, etc.), electric ships, electric equipment (lighting tools, electric shavers, electric repair tools, electric screwdrivers, electric lawn mowers, etc.).

[0144] The present invention provides an electric tool which adopts the high-capacity, high-rate battery pack, thereby improving the working stability of the electric tool.

[0145] The present invention is further described in detail below with reference to the embodiments and comparative examples.

[0146] Below, the embodiment of the application is described. The facts described below are exemplary and are only used to explain the application, and cannot be construed as limiting the application. In the embodiment, no specific technology or conditions are indicated, and the technology or conditions described in the literature in this area or the product instructions are carried out. The reagents used or the unindicated manufacturers are all conventional products that can be obtained commercially.

[0147] 1. Cylindrical battery 100

[0148] Example 1

[0149] (1) Preparation of negative electrode sheet 10:

[0150] Silicon carbon was used as the negative electrode silicon-based active material, and the binder PAA, CNT and graphene were mixed and stirred in deionized water at a mass ratio of 91.27:1:2:2 to prepare the negative electrode slurry. 2The surface density is double-sidedly coated on the first surface 111 and the second surface 112 of the copper foil with a thickness of 8μm and a length of 1190mm. The coated length of the first surface 111 is 1145mm, the blank length at one end is 10mm, and the blank length at the other end is 35mm; the coated length of the second surface 112 is 1091mm, the blank length at one end is 64mm, and the blank length at the other end is 35mm. After cold pressing, it is cut into a pole piece with a width of 59mm, a thickness of 60μm, and a length of 1090mm. The second pole ear 13 is welded on the first non-coated surface 111B of 35mm on the first surface 111 of the negative electrode pole piece 10. After welding the first pole ear 12 on the second non-coated surface 112B of 10mm on the second surface 112 of the negative electrode pole piece 10, a negative electrode pole piece 10 with a negative electrode silicon-based active material attached to the surface is obtained, and the gram capacity of the negative electrode silicon-based active material in the negative electrode pole piece 10 is 1280mAh / g.

[0151] (2) Preparation of positive electrode sheet 20:

[0152] NCM811 was used as the positive electrode active material, and the binder PVDF and the conductive agent SP, conductive agent SWCNT, and conductive agent MWCNT were mixed and stirred in NMP at a mass ratio of 96:1.14:1.5:0.06:0.8 to prepare a positive electrode slurry. 2 The positive electrode slurry is coated on both sides of an aluminum foil with a thickness of 15 μm and a length of 1082 mm, leaving a 7 mm blank area in the middle of the length direction of the front side of the positive electrode sheet, and cold-pressed to cut it into positive electrode sheets with a width of 57±1 mm, a thickness of 103 μm, and a length of 1082 mm. The positive electrode tab 22 is welded in the blank area to obtain a positive electrode sheet 20 with a positive electrode active material attached to the surface.

[0153] (3) Preparation of diaphragm 30

[0154] The selected diaphragm 30 has a thickness of 16 μm, is made of a three-layer isolation film of polypropylene / polyethylene / polypropylene (PP / PE / PP), has a length of 265 mm and a width of 61 mm.

[0155] (4) Preparation of electrolyte

[0156] In a glove box filled with argon (water content <10ppm, oxygen content <10ppm), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and fluoroethylene carbonate (FEC) were mixed at a mass ratio of DEC:EMC:EC:FEC=40:30:15:15 to obtain an organic solvent. Then, lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare a solution with a lithium salt (LiPF6) concentration of 1.0 mol / L, and then triphenyl phosphate (TPP) and 2,6-di-tert-butyl-p-cresol (BHT) were added and mixed to obtain an electrolyte.

[0157] (5) Assembly of cylindrical battery 100

[0158] (a): placing the prepared negative electrode sheet 10 and positive electrode sheet 20 into a vacuum oven to bake and remove water;

[0159] (b): The baked negative electrode sheet 10 and the positive electrode sheet 20 and the separator 30 are stacked in the order of "separator / negative electrode sheet / separator / positive electrode sheet" and then wound into a cylindrical winding core. When winding, one end of the second electrode tab 13 connected to the negative electrode sheet 10 is first wound, while ensuring that the first coating surface 111A of the negative electrode sheet 10 completely covers the third coating surface 211A of the positive electrode sheet 20;

[0160] (c): Assemble according to the ratio of the diameter of the cylindrical winding core to the inner diameter of the shell 50 being 0.98, and insert the cylindrical winding core into the shell 50;

[0161] (d): First, the second electrode tab 13 of the negative electrode is welded to the first electrode tab 12 to form a negative electrode tab, and then the negative electrode tab is welded to the bottom of the steel shell;

[0162] (e): welding the positive electrode tab 22 to the cap 40 to form a semi-finished battery cell;

[0163] (f): Bake the semi-finished battery cell, inject 6.0g of electrolyte according to the injection process, seal and soak it, then charge and form it, and assemble it into a 18650 battery.

[0164] Embodiment 2-4:

[0165] Examples 2-4 are used to illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the assembly ratios of the cylindrical batteries 100 in Examples 2-4 are different, that is, the ratios between the diameter of the winding core and the inner diameter of the shell 50 in the cylindrical battery 100 are different, wherein the assembly ratio in Example 2 is 0.96, the assembly ratio in Example 3 is 0.97, and the assembly ratio in Example 4 is 0.99. The specific parameters are subject to the data shown in Table 1 corresponding to each embodiment.

[0166] Embodiment 5-9:

[0167] Examples 5-9 are used to illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the different selections of materials in the negative electrode silicon-based active materials in Examples 5-9 result in different corresponding silicon element mass percentage contents, wherein, when the same silicon carbon and graphite materials are selected as the negative electrode silicon-based active materials, the silicon element mass percentage contents in the negative electrode silicon-based active materials are different due to the different contents of silicon carbon in the negative electrode silicon-based active materials, or, when silicon monoxide is used as the negative electrode silicon-based active material, the silicon element mass percentage contents are also different. The specific parameters shall be subject to the data shown in Table 1 corresponding to each embodiment.

[0168] Embodiment 10-12:

[0169] Examples 10-12 are used to illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the compaction density of the negative electrode silicon-based active material in Examples 10-12 is different, resulting in different thicknesses of the negative electrode plate 10. The specific parameters are subject to the data shown in Table 1 corresponding to each embodiment.

[0170] Embodiment 13-14:

[0171] Examples 13-14 are used to illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the compaction density of the positive electrode plate 20 in Examples 13-14 is different, resulting in different layer thicknesses of the positive electrode plate 20. The specific parameters are subject to the data shown in Table 1 corresponding to each embodiment.

[0172] Comparative Example 1-2:

[0173] Comparative Examples 1-2 are used to compare and illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the selection of materials in the negative electrode silicon-based active material in Comparative Examples 1-2 is different, resulting in different mass percentages of silicon elements in the negative electrode silicon-based active material. The specific parameters are subject to the data shown in Table 1 corresponding to each embodiment.

[0174] Comparative Examples 3-4:

[0175] Comparative Examples 3-4 are used to compare and illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the compaction density of the negative electrode silicon-based active material in Comparative Examples 3-4 is different, so that the thickness of the negative electrode plate 10 varies. The specific parameters are based on the data shown in Table 1 corresponding to each embodiment.

[0176] Comparative Examples 5-6:

[0177] Comparative Examples 5-6 are used to compare and illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the compaction density of the positive electrode active material in Comparative Examples 5-6 is different, so that the thickness of the positive electrode sheet 20 varies. The specific parameters are based on the data shown in Table 1 corresponding to each embodiment.

[0178] Comparative Example 7:

[0179] This comparative example 7 is used to compare and illustrate a cylindrical battery 100 disclosed in the present invention, including most of the operations in Example 1, except that: the assembly ratio of the cylindrical battery 100 in Comparative Example 7 is adjusted, and the specific parameters are based on the data shown in Table 1 corresponding to each embodiment.

[0180] 2. Performance test of the cylindrical battery 100 prepared in the above manner

[0181] (1) 0.2C discharge test method and battery capacity test

[0182] At an ambient temperature of 25°C, charge to 4.25V at a rate of 0.2C, then charge at a constant voltage until the battery is fully charged. After standing for 30 minutes, discharge to 2.3V at a rate of 0.2C, record the discharge temperature rise and capacity, and record the discharge capacity as the nominal capacity of the battery cell.

[0183] (2) 3C discharge test method

[0184] At an ambient temperature of 25°C, charge the battery to 4.25V at a rate of 0.2C, then charge at a constant voltage until the battery is fully charged. After standing for 30 minutes, discharge the battery to 2.3V at a rate of 3C, and record the discharge temperature rise and capacity.

[0185] (3) 6C discharge test method

[0186] At an ambient temperature of 25°C, charge the battery to 4.25V at a rate of 0.2C, then charge at a constant voltage until the battery is fully charged. After standing for 30 minutes, discharge the battery to 2.3V at a rate of 6C, and record the discharge temperature rise and capacity.

[0187] III. Analysis of test results of various embodiments and comparative examples

[0188] According to the above method, cylindrical batteries 100 of various embodiments and comparative examples were prepared respectively, and various performance parameters were measured. The results are shown in Table 1 below.

[0189] Table 1:

[0190]

[0191] Figure 7 1 is a graph showing the electrical performance parameters of the cylindrical battery 100 prepared in Example 1 of the present invention. Figure 7 A comprehensive analysis of the results of Example 1 in Table 1 shows that the cylindrical battery 100 prepared in Example 1 of the present invention has the best comprehensive performance. In Example 1, the silicon content in the negative electrode silicon-based active material accounts for 65%, and the compaction density of the negative electrode sheet 10 is controlled at 0.8 g / cm 3 When the negative electrode sheet 10 is coated with the negative silicon-based active material layer, the coating thickness is about 26 μm, so that the single-layer coating thickness of the negative electrode sheet 10 is controlled between 20 μm and 35 μm. At the same time, the compaction density of the positive electrode sheet 20 is 3.4 g / cm 3 When the positive electrode active material coating thickness on the positive electrode plate 20 is about 44μm, the single-layer coating thickness of the positive electrode plate 20 is controlled between 35μm and 55μm. Moreover, under the above parameters, the cylindrical battery 100 prepared at an assembly ratio of 0.98 can not only meet the demand for high capacity (battery capacity exceeds 3.5Ah), the battery capacity reaches 3.66Ah, but also meet the demand for high rate, and has good electrical performance in both 3C discharge and 6C discharge tests. Among them, when charging at 0.2C and discharging at 3C, the discharge capacity retention rate is 98%, and the temperature rise is 22.4°C. When charging at 0.2C and discharging at 6C, the discharge capacity retention rate is 96%, and the temperature rise is 45.6°C.

[0192] In Examples 2-14 of the present invention, the negative electrode silicon-based active material is selected differently, and different adjustments to parameters such as the silicon element content ratio, the negative electrode compaction density, and the positive electrode compaction density can all ensure the high rate and high capacity requirements of the cylindrical battery 100. From the test results of Table 1, it can be seen that compared with Comparative Examples 1-7, the cylindrical battery 100 in Example 2-14 has better performance in performance tests (0.2C discharge, 3C discharge, 6C discharge) and battery capacity. The cylindrical battery 100 in Comparative Examples 1-7 either cannot meet the high capacity requirements or cannot meet the high rate requirements.

[0193] In the test results of Comparative Example 1, since the negative electrode silicon-based active material uses a composite material of silicon-carbon and graphite, and the graphite content is relatively high, the content of silicon element in the negative electrode silicon-based active material is less than 40%, resulting in a decrease in the negative electrode lithium storage capacity of the cylindrical battery 100 in Comparative Example 1. In Comparative Example 1, not only is the battery capacity unable to meet the high capacity requirements (the battery capacity exceeds 3.5Ah), the layer thickness of the negative electrode plate 10 is 83μm, and the thickness of the single-layer negative electrode active material is also greater than 35μm.

[0194] In the test results of Comparative Example 2, since silicon particles are used in the negative electrode silicon-based active material, the content of silicon element in the negative electrode active material is 92%. Although the battery capacity reaches 4.41Ah to meet the high capacity demand of the battery, it cannot meet the high rate demand during the electrical performance parameter test. During the 3C discharge test, the temperature rise reaches 54.7°C, and the 6C discharge test cannot be completed.

[0195] In the test results of Comparative Example 3, since the compaction density of the negative electrode plate 10 is too large, although the battery capacity is greatly improved, the layer thickness of the negative electrode plate 10 is 46μm, and the thickness of the single-layer negative electrode active material is less than 20μm, which cannot meet the high rate requirements. Specifically, its electrical performance test results are not good, among which the temperature rise of 3C discharge is 38.3℃, and the temperature rise of 6C discharge is 67.2℃, and the discharge temperature rise is too high.

[0196] In the test results of Comparative Example 4, due to the low compaction density of the negative electrode plate 10, the battery capacity is only 3.08Ah, which cannot meet the high capacity requirements (battery capacity exceeds 3.5Ah), and the layer thickness of the negative electrode plate 10 is 92μm, and the thickness of the single-layer negative active material is also greater than 35μm.

[0197] In the test results of Comparative Example 5, due to the low compaction density of the positive electrode plate 20, the battery capacity is only 3.39 Ah, and the battery capacity cannot meet the demand for high capacity (the battery capacity exceeds 3.5 Ah).

[0198] In the test results of Comparative Example 6, since the compaction density of the positive electrode plate 20 is too large, although the battery capacity meets the high capacity requirement, it cannot meet the high rate requirement, which is specifically manifested in the poor electrical performance test results. The temperature rise of 3C discharge is 45.2°C, and the temperature rise of 6C discharge is 68.4°C, and the discharge temperature rise is too high.

[0199] In the test results of Comparative Example 7, due to the reduced assembly ratio of the cylindrical battery 100, the battery capacity decreased, and the battery capacity was only 3.37 Ah, which could not meet the demand for high capacity (the battery capacity exceeded 3.5 Ah).

[0200] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A negative electrode plate, characterized in that: It includes a negative electrode current collector, a negative electrode tab arranged on the negative electrode current collector, and a negative electrode silicon-based active material; The negative electrode current collector comprises a first surface and a second surface arranged along the thickness direction of the negative electrode current collector; The negative electrode silicon-based active material is coated on the first surface of the negative electrode current collector to form a first coating surface and a first non-coating surface, and the thickness of the first coating surface is 20 μm-35 μm; The negative electrode silicon-based active material is coated on the second surface of the negative electrode current collector to form a second coated surface and a second non-coated surface, and the thickness of the second coated surface is 20 μm-35 μm; The negative electrode silicon-based active material contains silicon element, and the mass percentage of the silicon element in the negative electrode silicon-based active material is 40-65%; The unit area density of the negative electrode plate is 4.0-4.5 mg / cm 2 ; The compaction density of the negative electrode plate is 0.6-1.0 g / cm 3 .

2. A negative electrode sheet according to claim 1, characterized in that: The gram capacity of the negative electrode silicon-based active material is ≥1200 mAh / g.

3. A negative electrode sheet according to claim 1, characterized in that: The compaction density of the negative electrode plate is 0.8 g / cm 3 .

4. A negative electrode sheet according to claim 1, characterized in that: The area of ​​the first coating surface is greater than the area of ​​the second coating surface.

5. A negative electrode sheet as claimed in claim 4, characterized in that: The area of ​​the first coating surface is 1.05-1.1 times the area of ​​the second coating surface.

6. A negative electrode sheet according to claim 1, characterized in that: The negative electrode tab includes a first tab and a second tab. The first tab and the second tab are spaced apart in the length direction of the negative electrode current collector and are located on a first non-coating surface and a second non-coating surface, respectively.

7. A negative electrode sheet as claimed in claim 6, characterized in that: The negative electrode current collector has two first and second sides parallel to each other along the width direction; The first electrode tab includes a first conductive sheet welded to the second non-coated surface and extending outward from the first side, and two first insulating sheets respectively attached to the first non-coated surface and the second non-coated surface and extending outward from the first side; the projection surfaces of the two first insulating sheets on the negative electrode current collector overlap with each other, and the first conductive sheet is located between the two first insulating sheets.

8. A negative electrode sheet as claimed in claim 7, characterized in that: The distance between the first conductive sheet and the side edge of the second coating surface is 45 mm-65 mm.

9. A negative electrode sheet as claimed in claim 7, characterized in that: The width of the first insulating sheet is 1.5-2.5 times the width of the first conductive sheet.

10. A negative electrode sheet according to claim 7, characterized in that: The first insulating sheet extends outward along the first side edge by a length of 0.5 mm to 3 mm.

11. A negative electrode sheet according to claim 7, characterized in that: The second electrode tab is a second conductive sheet welded to the first coating surface and extending outward from the second side.

12. A negative electrode sheet according to claim 11, characterized in that: The distance between the second conductive sheet and the side edge of the first coating surface is 15 mm-20 mm.

13. A negative electrode sheet according to claim 11, characterized in that: The length of the first conductive sheet extending outward along the first side is A, and the length of the second conductive sheet extending outward along the first side is B. The length relationship between the two should satisfy the following conditions: A>B and AB>8mm.

14. A negative electrode sheet according to claim 11, characterized in that: The width of the second conductive sheet is 0.5-1 times the width of the first conductive sheet.

15. The negative electrode sheet according to claim 1, characterized in that: The negative electrode tab includes a main tab arranged on the first non-coated surface or the second non-coated surface and a plurality of auxiliary tabs arranged on the first non-coated surface and / or the second non-coated surface, and the plurality of auxiliary tabs are arranged at intervals along the length direction of the negative electrode current collector.

16. A negative electrode sheet according to claim 15, characterized in that: The main electrode tab and the plurality of the auxiliary electrode tabs all extend outward based on the negative electrode current collector, and the main electrode tab and the plurality of the auxiliary electrode tabs extend outward in the same direction based on the negative electrode current collector.

17. A negative electrode sheet according to claim 16, characterized in that: The length of the main electrode tab extending outward based on the negative electrode current collector is greater than the length of the secondary electrode tab extending outward based on the negative electrode current collector.

18. A cylindrical battery, characterized in that: It comprises a shell, a cap, an electrolyte arranged in the shell and a cylindrical winding core, wherein the cylindrical winding core comprises a positive electrode sheet, a separator and a negative electrode sheet as described in any one of claims 1 to 17.

19. A cylindrical battery as claimed in claim 18, characterized in that: The positive electrode sheet includes a positive electrode current collector, a positive electrode tab disposed on the positive electrode current collector, and a positive electrode active material; the positive electrode active material is a LiNi x Co y Mn 1-x-y O2 material, where the value range of x and y is 0-1.

20. A cylindrical battery as claimed in claim 19, characterized in that: The unit area density of the positive electrode sheet is 28-33 mg / cm 2 .

21. A cylindrical battery as claimed in claim 19, characterized in that: The compaction density of the positive electrode sheet is 3.2-3.8 g / cm 3 .

22. A cylindrical battery as claimed in claim 19, characterized in that: The positive electrode current collector includes a third surface and a fourth surface arranged along the thickness direction of the positive electrode current collector; The positive electrode active material is coated on the third surface of the positive electrode current collector to form a plurality of third coating surfaces, a first blank area is formed between two adjacent third coating surfaces, and the thickness of the third coating surface is 35 μm-55 μm; The positive electrode active material is coated on the fourth surface of the positive electrode current collector to form a plurality of fourth coating surfaces, a second blank area is formed between two adjacent fourth coating surfaces, and the thickness of the fourth coating surface is 35 μm-55 μm.

23. A cylindrical battery as claimed in claim 22, characterized in that: The positive electrode current collector has two third sides and a fourth side that are arranged parallel to each other along the width direction; The positive electrode tab includes a plurality of third conductive sheets welded to the first blank area and extending outward from the third side, and a plurality of pairs of second insulating sheets respectively attached to the first blank area and the second blank area and extending outward from the third side; The projection surfaces of each pair of the second insulating sheets on the positive electrode current collector overlap with each other, and the third conductive sheet is located between two of the second insulating sheets.

24. A cylindrical battery as claimed in claim 23, characterized in that: The third surface of the positive electrode collector is provided with two third coated surfaces and one first blank area, and the two third coated surfaces are symmetrically arranged on both sides of the first blank area. The fourth surface of the positive electrode collector is provided with two fourth coated surfaces and one second blank area; the positive electrode tab includes a third conductive sheet welded to the first blank area and a pair of second insulating sheets.

25. A cylindrical battery as claimed in claim 22, characterized in that: The width of the positive electrode tab of the positive electrode plate is the same as the width of the negative electrode tab.

26. A cylindrical battery as claimed in claim 22, characterized in that: The widths of the first blank area and the second blank area are at least 2 mm greater than the width of the positive electrode tab.

27. A cylindrical battery as claimed in claim 23, characterized in that: The area of ​​the second insulating sheet is larger than the area of ​​the first blank area or the second blank area of ​​the positive electrode current collector.

28. A cylindrical battery as claimed in claim 22, characterized in that: When winding, the first coated surface of the negative electrode sheet faces the third coated surface of the positive electrode sheet, and the length of the first coated surface is greater than the length of the positive electrode collector of the positive electrode sheet.

29. A cylindrical battery as claimed in claim 23, characterized in that: The length of the second insulating sheet extending outward along the third side is 2 mm-4 mm, and the length of the second insulating sheet extending outward along the fourth side is 0.2 mm-1.0 mm.

30. A cylindrical battery as claimed in claim 18, characterized in that: The cylindrical winding core is assembled in the shell, and the diameter of the cylindrical winding core is 0.96-0.99 times the inner diameter of the shell.

31. A cylindrical battery as claimed in claim 18, characterized in that: The length of the negative electrode plate is 1190mm-1205mm; the length of the positive electrode plate is 1081mm-1091mm.

32. A cylindrical battery as claimed in claim 31, characterized in that: The injection amount of the electrolyte is 5.6g-6.2g.

33. A cylindrical battery as claimed in claim 18, characterized in that: When the cylindrical battery is charged at 0.2C and discharged at 3C, the discharge capacity retention rate is greater than 97% and the temperature rise is 20-35°C.

34. A cylindrical battery as claimed in claim 18, characterized in that: When the cylindrical battery is charged at 0.2C and discharged at 6C, the discharge capacity retention rate is greater than 95% and the temperature rise is 45-65°C.

35. A cylindrical battery as claimed in claim 18, characterized in that: The capacity of the cylindrical battery is greater than 3500 mAh.

36. A battery pack, characterized in that: The method comprises two or more cylindrical batteries according to any one of claims 18 to 35, wherein the two or more cylindrical batteries are electrically connected in series or in parallel.

37. An electric tool, characterized in that: Comprising a battery pack as claimed in claim 36.

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