High-capacity 21700 lithium ion battery, preparation method thereof and electric equipment

Abstract

The invention provides a high-capacity 21700 lithium ion battery, a preparation method of the high-capacity 21700 lithium ion battery and power-related equipment, and relates to the field of lithium ion batteries. The 21700 lithium ion battery provided by the invention comprises a positive pole piece and a negative pole piece, 6-25 positive pole lugs are arranged at one end of an empty foil of the positive pole piece, and 6-25 negative pole lugs are arranged at one end of an empty foil of the negative pole piece. According to the high-capacity 21700 lithium ion battery provided by the invention, the current flow capacity can be enhanced, the current flow capacity in the charging and discharging processes can be remarkably enhanced, the safety and the stability can be improved, local overheating and potential safety risks are reduced, the battery can still keep stable performance output under the high-load condition, and the service life of the battery is prolonged. And the requirements of various complex application scenes are met.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion batteries, and in particular to a high-capacity 21700 lithium-ion battery and a preparation method thereof and electrical equipment. Background Art

[0002] As the popularity of electric vehicles, wearable smart devices and various portable electronic products has risen sharply, consumers' expectations for the battery life, safety performance and service life of these devices have also increased. As a key component of these devices, the urgency of optimizing the performance of lithium-ion batteries has become increasingly prominent. At present, although everyone is committed to balancing battery capacity and safety through material optimization, the development progress is very slow, causing the performance improvement of lithium-ion batteries to stagnate.

[0003] What is more serious is that in the frequent charge and discharge cycles, traditional lithium-ion batteries are prone to overheating in local areas due to the uneven internal current distribution, which not only accelerates the aging process of the battery, but also may induce safety hazards such as short circuit and thermal runaway. At the same time, the volume expansion of battery materials brought by the high-capacity system is particularly obvious during the charge and discharge process, especially at the connection of the pole ear. This expansion may cause light transmission, thereby affecting the safety and service life of the battery. Therefore, exploring and developing a new lithium-ion battery technology that takes into account both high battery capacity and safety performance has become the focus of attention inside and outside the industry. Summary of the invention

[0004] The purpose of the present application is to provide a method for preparing a high-capacity 21700 lithium-ion battery and a 21700 lithium-ion battery to solve the above problems.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] A high-capacity 21700 lithium-ion battery comprises a positive electrode sheet and a negative electrode sheet, wherein one end of the hollow foil of the positive electrode sheet is provided with 6-25 positive electrode tabs, and one end of the hollow foil of the negative electrode sheet is provided with 6-25 negative electrode tabs.

[0007] Optionally, the positive electrode tab has a length of 10-20 mm and a width of 4-8 mm; the negative electrode tab has a length of 5-15 mm and a width of 4-8 mm.

[0008] Optionally, the positive electrode plate includes a positive electrode current collector and a positive electrode active layer disposed on the surface of the positive electrode current collector, and raw materials of the positive electrode active layer include a positive electrode active material, a first conductive agent, a first binder and a first solvent.

[0009] Optionally, the positive electrode active layer satisfies at least one of the following conditions:

[0010] a. The positive electrode active material includes a nickel-cobalt-manganese ternary material Li (Ni x Co y Mn 1-x-y ) 2 , where 0.7<X<0.95;

[0011] b. The first conductive agent includes one or more of carbon black, multi-walled carbon tubes, and single-walled carbon tubes;

[0012] c. The first binder comprises one or more of carboxymethyl cellulose, polymethyl methacrylate, and polyvinylidene fluoride;

[0013] d. the first solvent comprises methyl pyrrolidone;

[0014] e. The mass ratio of the positive electrode active material, the first conductive agent, and the first binder is 93-97: 1-5: 2-4.

[0015] Optionally, the negative electrode plate includes a negative electrode current collector and a negative electrode active layer disposed on the surface of the negative electrode current collector, and raw materials of the negative electrode active layer include negative electrode active material, a second conductive agent, a second binder, a dispersant and a second solvent.

[0016] Optionally, the negative electrode active layer satisfies at least one of the following conditions:

[0017] f. The negative electrode active material comprises a silicon-carbon composite material and graphite, wherein the gram capacity of the silicon-carbon composite material is 1500-2000mAh / g, and the gram capacity of the graphite is 340-360mAh / g;

[0018] g. The second conductive agent includes one or more of carbon black, multi-walled carbon tubes, and single-walled carbon tubes;

[0019] h. The second binder comprises carboxymethyl cellulose;

[0020] i. The dispersant comprises styrene-butadiene rubber;

[0021] j. The mass ratio of the negative electrode active material, the second conductive agent, the second binder, and the dispersant is 93-96: 1.5-2.5: 1-1.5: 1.5-3.

[0022] Optionally, the positive and negative electrode sheets satisfy at least one of the following conditions:

[0023] k. The positive electrode current collector comprises an aluminum foil having a thickness of 12-15 μm;

[0024] l. The negative electrode current collector comprises copper foil having a thickness of 8-10 μm;

[0025] m. The compaction density of the positive electrode active layer is 3.4-3.6 mg / cm 3 The compaction density of the negative electrode active layer is 1.3-1.6 mg / cm 3 .

[0026] The present application also provides a method for preparing a high-capacity 21700 lithium-ion battery, comprising:

[0027] The positive electrode slurry is coated on the positive electrode current collector, and after drying, a positive electrode sheet is obtained; the negative electrode slurry is coated on the negative electrode current collector, and after drying, a negative electrode sheet is obtained; 6-25 positive electrode tabs are arranged at one end of the positive electrode sheet, and 6-25 negative electrode tabs are arranged at one end of the negative electrode sheet;

[0028] The positive electrode sheet and the negative electrode sheet are rolled and then wound with a separator to form a battery core, and the negative electrode multi-pole tab is welded to the inner bottom surface of the battery shell.

[0029] Optionally, the positive electrode tab and the negative electrode tab are formed at both ends of the battery cell by laser cutting.

[0030] The present application also provides an electrical device comprising the high-capacity 21700 lithium-ion battery.

[0031] Compared with the prior art, the beneficial effects of this application include:

[0032] This application uses a pole piece design with 6-25 pole ears. On the one hand, it can enhance the current flow capacity, and the current flow capacity during charging and discharging is significantly enhanced, which can not only improve the working efficiency of the battery, but also reduce the heat loss of the battery during long-term use and extend the service life of the battery; on the other hand, it can improve safety and stability. Such a design makes the current distribution inside the battery more uniform, reduces local overheating and potential safety risks, and ensures that the battery can operate reliably under various working conditions; and it can also reduce battery impedance and improve the high-rate charge and discharge performance of the battery. This allows the battery to maintain stable performance output under high load conditions and meet the needs of various complex application scenarios.

[0033] In addition, the selection of positive and negative electrode active materials can further reduce the internal resistance of the battery and make the battery current density distribution more uniform. The capacity is higher than that of batteries with traditional tabs and poles. It can also extend the cycle life of the battery, so that the battery can still maintain a high performance level after multiple charge and discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0035] Figure 1 It is a schematic diagram of a multi-electrode pole piece in this application;

[0036] Figure 2 A schematic diagram of the preparation process of a high-capacity 21700 battery provided in an embodiment;

[0037] Figure 3 Schematic diagram for comparing the internal resistance distribution of Example 1 and Comparative Example 1;

[0038] Figure 4 Schematic diagram showing the comparison of the cycle performance of Example 1 and Comparative Example 1 at 0.5C;

[0039] Figure 5 Schematic diagram comparing the cycle performance of Example 1 and Comparative Example 1 at 1.0C. DETAILED DESCRIPTION

[0040] As used herein:

[0041] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0042] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0043] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0044] In these examples, parts and percentages are by mass unless otherwise indicated.

[0045] "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass of all components is not limited to 100 parts.

[0046] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0047] In order to better explain the technical solution provided by this application, before the embodiments, the technical solution is first described as a whole, as follows:

[0048] In a first aspect, the present application provides a high-capacity 21700 lithium-ion battery, comprising a positive electrode sheet and a negative electrode sheet, wherein one end of the empty foil of the positive electrode sheet is provided with 6-25 positive electrode tabs, and one end of the empty foil of the negative electrode sheet is provided with 6-25 negative electrode tabs.

[0049] The positive and negative electrodes of the present application are provided with 6-25 tabs, such as Figure 1As shown in the figure (12 tabs), the current flow capacity is significantly enhanced during the charging and discharging process, which not only improves the working efficiency of the battery, but also reduces the heat loss of the battery during long-term use and prolongs the service life of the battery; it can also improve safety and stability. This design makes the current distribution inside the battery more uniform, reduces local overheating and potential safety risks, and ensures that the battery can operate reliably under various working conditions; and it can also reduce battery impedance and improve the high-rate charge and discharge performance of the battery. This allows the battery to maintain stable performance output under high load conditions and meet the needs of various complex application scenarios.

[0050] In an optional embodiment, the length of the positive electrode tab is 10-20 mm and the width is 4-8 mm; the length of the negative electrode tab is 5-15 mm and the width is 4-8 mm. The tab is a connecting component between the internal and external circuits of the battery, and its conductivity directly affects the internal resistance and energy loss of the battery. By precisely controlling the length and width of the tab, it can be ensured that the tab has a sufficient cross-sectional area, thereby reducing the resistance when the current passes through, reducing the loss of energy during the transmission process, and improving the overall efficiency of the battery.

[0051] Optionally, the length of the positive electrode tab may be 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any value between 10 and 20 mm; the width of the positive electrode tab may be 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, or any value between 4 and 8 mm.

[0052] Optionally, the length of the negative electrode tab may be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, or any value between 5 and 15 mm; the width of the negative electrode tab may be 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, or any value between 4 and 8 mm.

[0053] In an optional embodiment, the positive electrode plate includes a positive electrode current collector and a positive electrode active layer disposed on the surface of the positive electrode current collector, and the raw materials of the positive electrode active layer include a positive electrode active material, a first conductive agent, a first binder and a first solvent.

[0054] In an optional embodiment, the positive electrode active material includes a nickel-cobalt-manganese ternary material Li (Ni x Co y Mn 1-x-y ) 2 , where 0.7<X<0.95.

[0055] In an optional embodiment, the first conductive agent includes one or more of carbon black, multi-walled carbon tubes, and single-walled carbon tubes; the first binder includes one or more of carboxymethyl cellulose, polymethyl methacrylate, and polyvinylidene fluoride; and the first solvent includes methyl pyrrolidone.

[0056] In an optional embodiment, the mass ratio of the positive electrode active material, the first conductive agent, and the first binder is 93-97: 1-5: 2-4. By precisely controlling the mass ratio of the positive electrode active material, the first conductive agent, and the first binder, the energy density of the lithium-ion battery can be increased and the conductivity can be improved.

[0057] In an optional embodiment, the negative electrode plate includes a negative electrode current collector and a negative electrode active layer disposed on the surface of the negative electrode current collector, and the raw materials of the negative electrode active layer include negative electrode active material, a second conductive agent, a second binder, a dispersant and a second solvent.

[0058] In an optional embodiment, the negative electrode active material includes a silicon-carbon composite material and graphite, the gram capacity of the silicon-carbon composite material is 1500-2000mAh / g, and the gram capacity of the graphite is 340-360mAh / g; the second conductive agent includes one or more of carbon black, multi-walled carbon tubes, and single-walled carbon tubes; the second binder includes carboxymethyl cellulose; and the dispersant includes styrene-butadiene rubber. By controlling the gram capacity of the negative electrode material, the energy density of the battery can be improved. Negative electrode active materials with high gram capacity can store more electrical energy at the same mass, thereby improving the energy density of the battery and extending the battery life of the device. However, too high or too low gram capacity of the negative electrode active material may pose a threat to the safety of the battery. The gram capacity of the carbon-silicon composite material in this application is 1500-2000mAh / g, which is a very high level among negative electrode active materials and is significantly higher than the prior art. This application controls the number of pole ears and the length, width and other parameters of the pole ears, which can be coordinated with the high gram capacity of the carbon-silicon composite material, thereby ensuring the safety of the battery, cycle stability, that is, rate performance, while obtaining high energy density and greatly extending the battery life.

[0059] Optionally, the gram capacity of the carbon silicon composite material may be 1500mAh / g, 1600mAh / g, 1700mAh / g, 1800mAh / g, 1900mAh / g, 2000mAh / g, or any value between 1500-2000mAh / g. The gram capacity of the graphite may be 340mAh / g, 345mAh / g, 350mAh / g, 355mAh / g, 360mAh / g, or any value between 340-360mAh / g.

[0060] In an optional embodiment, the mass ratio of the negative electrode active material, the second conductive agent, and the second binder is 93-96:2-4:2-5.

[0061] In an optional embodiment, the positive electrode current collector comprises aluminum foil with a thickness of 12-15 μm, and the negative electrode current collector comprises copper foil with a thickness of 8-10 μm.

[0062] Optionally, the thickness of the positive electrode current collector may be 12 μm, 13 μm, 14 μm, 15 μm, or any value between 12 and 15 μm. The thickness of the negative electrode current collector may be 8 μm, 9 μm, 10 μm, or any value between 8 and 10 μm.

[0063] In an optional embodiment, the compaction density of the positive electrode active layer is 3.4-3.6 mg / cm 3 The compaction density of the negative electrode active layer is 1.3-1.6 mg / cm 3 .

[0064] Optionally, the compaction density of the positive electrode active layer can be 3.4 mg / cm 3 、3.5mg / cm 3 、3.6mg / cm 3 , or 3.4-3.6 mg / cm 3 The compaction density of the negative electrode active layer can be 1.3 mg / cm 3 , 1.4mg / cm 3 , 1.5mg / cm 3 、1.6mg / cm 3 , or 1.3-1.6 mg / cm 3 Any value in between.

[0065] In a second aspect, the present application also provides a method for preparing a high-capacity 21700 lithium-ion battery, comprising:

[0066] The positive electrode slurry is coated on the positive electrode current collector, and after drying, a positive electrode sheet is obtained; the negative electrode slurry is coated on the negative electrode current collector, and after drying, a negative electrode sheet is obtained; 6-25 positive electrode tabs are arranged at one end of the positive electrode sheet, and 6-25 negative electrode tabs are arranged at one end of the negative electrode sheet;

[0067] The positive electrode sheet and the negative electrode sheet are rolled and then wound with the separator to form a battery core, and the negative electrode multi-pole tab is welded to the inner bottom surface of the battery shell.

[0068] Optionally, the positive electrode tab and the negative electrode tab are formed at both ends of the battery cell by laser cutting, and the length and width of the positive electrode tab and the negative electrode tab are optimized according to the size of the battery cell.

[0069] In a third aspect, the present application also provides an electrical device comprising the high-capacity multi-pole 21700 lithium-ion battery.

[0070] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0071] Example 1

[0072] This embodiment provides a high-capacity 21700 lithium-ion battery, such as Figure 2 The preparation method thereof is as follows:

[0073] 1.1 Slurry preparation

[0074] Preparation of positive electrode slurry: select high nickel ternary material NMC 811 (nickel, manganese, cobalt ratio of 8:1:1) with a mass fraction of 96%, the positive electrode conductor is conductive carbon black with a mass fraction of 2.3%, the positive electrode binder is polyvinylidene fluoride with a mass fraction of 1.7%, and the solvent for preparing the positive electrode slurry is methyl pyrrolidone, which is stirred evenly.

[0075] Preparation of negative electrode slurry: Graphite mixed with silicon and carbon (74:26) was selected as the negative electrode active material with a mass fraction of 94.6% (the gram capacity of graphite was 354 mAh / g and the gram capacity of silicon and carbon was 1800 mAh / g), and 1.9% of conductive carbon black, 1.1% of carboxymethyl cellulose and 2.4% of styrene-butadiene rubber were added and mixed.

[0076] 1.2 Pole preparation

[0077] The positive electrode current collector is aluminum foil with a thickness of 12 μm. The positive electrode slurry is stirred evenly and then coated on both surfaces of the aluminum foil. The surface density of the aluminum foil coating on both sides is 50 mg / cm 2 Then, the aluminum foil coated with the positive electrode slurry is dried, slitting, rolling and slitting in sequence according to the conventional process to prepare the positive electrode sheet. The compaction density of the positive electrode sheet is 3.57g / cm 3 .

[0078] The negative electrode current collector is copper foil with a thickness of 8 μm. The negative electrode slurry is stirred evenly and then coated on both surfaces of the copper foil. The surface density of the copper foil coating on both sides is 16.25 mg / cm2 Then, the aluminum foil coated with the negative electrode slurry is dried, slitting, die-cutting, rolling and slitting in sequence according to the conventional process to prepare the negative electrode sheet. The compaction density of the negative electrode sheet is 1.5g / cm 3 .

[0079] In the die-cutting process, during the preparation of the pole piece, by precisely controlling the coating process, uncoated areas are left at both ends of the pole piece as the pole ear area (22mm for the positive pole piece and 17mm for the negative pole piece). Using laser cutting equipment, 14 pole ears are cut out in the uncoated area, each with a width of 4mm, a positive pole ear length of 20mm, and a negative pole ear length of 15mm. The spacing between adjacent pole ears is calculated (keeping only one per circle), so that the pole ears at both ends are in the same straight line when winding.

[0080] 1.3 Cell Preparation

[0081] The coated positive and negative electrodes and separators are precisely aligned in the order of positive-separator-negative (the separator thickness is 11um), and then wound using an automatic winding machine. During the winding process, the winding speed and tension are strictly controlled to ensure that there are no bubbles or misalignment between the positive and negative electrodes and the separator. After winding, the battery cell is fixed with high-temperature tape to prevent deformation or loosening of the battery cell in subsequent processes.

[0082] 1.4 Battery Assembly

[0083] The wound battery cell is subjected to joint welding of the positive electrode tab and spot welding of the negative electrode tab; then the battery cell is assembled, and an electrolyte solvent is an electrolyte having a mass ratio of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate of 11:34:55 and liquid is injected to obtain a 21700 lithium-ion battery.

[0084] Example 2

[0085] This embodiment provides a high-capacity 21700 lithium-ion battery, and the preparation method is as follows:

[0086] 2.1 Slurry preparation

[0087] Preparation of positive electrode slurry: select high nickel ternary material NMC 811 (nickel, manganese, cobalt ratio of 9:0.68:0.32) with a mass fraction of 97%, the positive electrode conductor is conductive carbon black with a mass fraction of 1.75%, the positive electrode binder is polyvinylidene fluoride with a mass fraction of 1.25%, and the solvent for preparing the positive electrode slurry is methyl pyrrolidone, which is stirred evenly.

[0088] Preparation of negative electrode slurry: Graphite mixed with silicon and carbon (74:26) was selected as the negative electrode active material with a mass fraction of 94.6% (the gram capacity of graphite was 354 mAh / g, and the gram capacity of silicon and carbon was 1600 mAh / g), and 1.9% of conductive carbon black, 1.1% of carboxymethyl cellulose and 2.4% of styrene-butadiene rubber were added for mixing.

[0089] 2.2 Pole piece preparation

[0090] The positive electrode current collector is aluminum foil with a thickness of 12 μm. The positive electrode slurry is stirred evenly and then coated on both surfaces of the aluminum foil. The surface density of the aluminum foil coating on both sides is 48 mg / cm 2 Then, the aluminum foil coated with the positive electrode slurry is dried, rolled and cut in sequence according to the conventional process to prepare the positive electrode sheet. The compaction density of the positive electrode sheet is 3.55g / cm 3 .

[0091] The negative electrode current collector is copper foil with a thickness of 8 μm. The negative electrode slurry is stirred evenly and then coated on both surfaces of the copper foil. The surface density of the copper foil coating on both sides is 15.51 mg / cm 2 Then, the aluminum foil coated with the negative electrode slurry is dried, slitting, die-cutting, rolling and slitting in sequence according to the conventional process to prepare the negative electrode sheet. The compaction density of the negative electrode sheet is 1.5g / cm 3 .

[0092] In the die-cutting process mentioned above, during the preparation of the pole piece, by precisely controlling the coating process, uncoated areas are left at both ends of the pole piece as the lug area (22mm for the positive pole piece and 13mm for the negative pole piece). Using laser cutting equipment, 9 lugs are cut out of the positive pole and 24 lugs are cut out of the negative pole in the uncoated area. The width of each lug is 4mm, and the distance between adjacent lugs is calculated (only one lug is kept in one circle). The length of the positive lug is 20mm and the length of the negative lug is 10mm, so that the lugs at both ends are in the same straight line when winding. This design ensures that the battery has lower internal resistance and higher energy density during the charging and discharging process.

[0093] 2.3 Cell Preparation

[0094] The coated positive and negative electrodes and separators are precisely aligned in the order of positive-separator-negative (the separator thickness is 11um), and then wound using an automatic winding machine. During the winding process, the winding speed and tension are strictly controlled to ensure that there are no bubbles or misalignment between the positive and negative electrodes and the separator. After winding, the battery cell is fixed with high-temperature tape to prevent deformation or loosening of the battery cell in subsequent processes.

[0095] 2.4 Battery Assembly

[0096] The wound battery cell is subjected to joint welding of the positive electrode tab and spot welding of the negative electrode tab; then the battery cell is assembled, and an electrolyte solvent is an electrolyte having a mass ratio of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate of 11:34:55 and liquid is injected to obtain a 21700 lithium-ion battery.

[0097] Example 3

[0098] This embodiment provides a high-capacity 21700 lithium-ion battery, and the preparation method is as follows:

[0099] 3.1 Slurry preparation

[0100] Preparation of positive electrode slurry: select high nickel ternary material NMC 811 (nickel, manganese, cobalt ratio of 8:1:1) with a mass fraction of 96%, the positive electrode conductor is conductive carbon black with a mass fraction of 2.3%, the positive electrode binder is polyvinylidene fluoride with a mass fraction of 1.7%, and the solvent for preparing the positive electrode slurry is methyl pyrrolidone, which is stirred evenly.

[0101] Preparation of negative electrode slurry: Graphite mixed with silicon and carbon (74:26) was selected as the negative electrode active material with a mass fraction of 94.6% (the gram capacity of graphite was 354 mAh / g and the gram capacity of silicon and carbon was 1800 mAh / g), and 1.9% of conductive carbon black, 1.1% of carboxymethyl cellulose and 2.4% of styrene-butadiene rubber were added and mixed.

[0102] 3.2 Pole piece preparation

[0103] The positive electrode current collector is aluminum foil with a thickness of 12 μm. The positive electrode slurry is stirred evenly and then coated on both surfaces of the aluminum foil. The surface density of the aluminum foil coating on both sides is 50 mg / cm 2 Then, the aluminum foil coated with the positive electrode slurry is dried, rolled and cut in sequence according to the conventional process to prepare the positive electrode sheet. The compaction density of the positive electrode sheet is 3.57 g / cm 3 .

[0104] The negative electrode current collector is copper foil with a thickness of 8 μm. The negative electrode slurry is stirred evenly and then coated on both surfaces of the copper foil. The surface density of the copper foil coating on both sides is 16.25 mg / cm 2 Then, the aluminum foil coated with the negative electrode slurry is dried, slitting, die-cutting, rolling and slitting in sequence according to the conventional process to prepare the negative electrode sheet. The compaction density of the negative electrode sheet is 1.5g / cm 3 .

[0105] In the die-cutting process, during the preparation of the pole piece, by precisely controlling the coating process, uncoated areas are left at both ends of the pole piece as the pole ear area (22mm for the positive pole piece and 17mm for the negative pole piece). Using laser cutting equipment, 24 pole ears are cut out in the uncoated area, each with a width of 4mm, a positive pole ear length of 20mm, and a negative pole ear length of 15mm. The spacing between adjacent pole ears is calculated (keeping only one per turn), so that the pole ears at both ends are in the same straight line when winding.

[0106] 3.3 Cell Preparation

[0107] The coated positive and negative electrodes and separators are precisely aligned in the order of positive-separator-negative (the separator thickness is 11um), and then wound using an automatic winding machine. During the winding process, the winding speed and tension are strictly controlled to ensure that there are no bubbles or misalignment between the positive and negative electrodes and the separator. After winding, the battery cell is fixed with high-temperature tape to prevent deformation or loosening of the battery cell in subsequent processes.

[0108] 3.4 Battery Assembly

[0109] The wound battery cell is subjected to joint welding of the positive electrode tab and spot welding of the negative electrode tab; then the battery cell is assembled, and an electrolyte solvent is an electrolyte having a mass ratio of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate of 11:34:55 and liquid is injected to obtain a 21700 lithium-ion battery.

[0110] Example 4

[0111] This embodiment provides a high-capacity 21700 lithium-ion battery, and the preparation method is as follows:

[0112] 4.1 Slurry preparation

[0113] Preparation of positive electrode slurry: select high nickel ternary material NMC 811 (nickel, manganese, cobalt ratio of 9:0.68:0.32) with a mass fraction of 97%, the positive electrode conductor is conductive carbon black with a mass fraction of 1.75%, the positive electrode binder is polyvinylidene fluoride with a mass fraction of 1.25%, and the solvent for preparing the positive electrode slurry is methyl pyrrolidone, which is stirred evenly.

[0114] Preparation of negative electrode slurry: Graphite mixed with silicon and carbon (74:26) was selected as the negative electrode active material with a mass fraction of 94.6% (the gram capacity of graphite was 354 mAh / g and the gram capacity of silicon and carbon was 1800 mAh / g), and 1.9% of conductive carbon black, 1.1% of carboxymethyl cellulose and 2.4% of styrene-butadiene rubber were added and mixed.

[0115] 4.2 Pole piece preparation

[0116] The positive electrode current collector is aluminum foil with a thickness of 12 μm. The positive electrode slurry is stirred evenly and then coated on both surfaces of the aluminum foil. The surface density of the aluminum foil coating on both sides is 48 mg / cm 2 Then, the aluminum foil coated with the positive electrode slurry is dried, rolled and cut in sequence according to the conventional process to prepare the positive electrode sheet. The compaction density of the positive electrode sheet is 3.55g / cm 3 .

[0117] The negative electrode current collector is copper foil with a thickness of 8 μm. The negative electrode slurry is stirred evenly and then coated on both surfaces of the copper foil. The surface density of the copper foil coating on both sides is 15.51 mg / cm 2 Then, the aluminum foil coated with the negative electrode slurry is dried, slitting, die-cutting, rolling and slitting in sequence according to the conventional process to prepare the negative electrode sheet. The compaction density of the negative electrode sheet is 1.5g / cm 3 .

[0118] In the die-cutting process mentioned above, during the preparation of the pole piece, by precisely controlling the coating process, uncoated areas are left at both ends of the pole piece as the lug area (22mm for the positive pole piece and 13mm for the negative pole piece). Using laser cutting equipment, 9 lugs are cut out of the positive pole and 24 lugs are cut out of the negative pole in the uncoated area. The width of each lug is 4mm, and the distance between adjacent lugs is calculated (only one lug is kept in one circle). The length of the positive lug is 20mm and the length of the negative lug is 10mm, so that the lugs at both ends are in the same straight line when winding. This design ensures that the battery has lower internal resistance and higher energy density during the charging and discharging process.

[0119] 4.3 Cell Preparation

[0120] The coated positive and negative electrodes and separators are precisely aligned in the order of positive-separator-negative (the separator thickness is 11um), and then wound using an automatic winding machine. During the winding process, the winding speed and tension are strictly controlled to ensure that there are no bubbles or misalignment between the positive and negative electrodes and the separator. After winding, the battery cell is fixed with high-temperature tape to prevent deformation or loosening of the battery cell in subsequent processes.

[0121] 4.4 Battery Assembly

[0122] The wound battery cell is subjected to joint welding of the positive electrode tab and spot welding of the negative electrode tab; then the battery cell is assembled, and an electrolyte solvent is an electrolyte having a mass ratio of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate of 11:34:55 and liquid is injected to obtain a 21700 lithium-ion battery.

[0123] Example 5

[0124] This embodiment provides a high-capacity 21700 lithium-ion battery, and the preparation method is as follows:

[0125] 5.1 Slurry preparation

[0126] Preparation of positive electrode slurry: select high nickel ternary material (nickel, manganese, cobalt ratio of 9:0.68:0.32) with a mass fraction of 97%, the positive electrode conductor is conductive carbon black with a mass fraction of 1.75%, the positive electrode binder is polyvinylidene fluoride with a mass fraction of 1.25%, and the solvent for preparing the positive electrode slurry is methyl pyrrolidone, which is stirred evenly.

[0127] Preparation of negative electrode slurry: Graphite mixed with silicon and carbon (72:28) was selected as the negative electrode active material with a mass fraction of 94.6% (the gram capacity of graphite was 344 mAh / g and the gram capacity of silicon and carbon was 1800 mAh / g), and 2.2% of conductive carbon black, 1.1% of carboxymethyl cellulose and 2.1% of styrene-butadiene rubber were added for mixing.

[0128] 5.2 Pole preparation

[0129] The positive electrode current collector is aluminum foil with a thickness of 12 μm. The positive electrode slurry is stirred evenly and then coated on both surfaces of the aluminum foil. The surface density of the aluminum foil coating on both sides is 50 mg / cm 2 Then, the aluminum foil coated with the positive electrode slurry is dried, slitting, rolling and slitting in sequence according to the conventional process to prepare the positive electrode sheet. The compaction density of the positive electrode sheet is 3.55g / cm 3 .

[0130] The negative electrode current collector is copper foil with a thickness of 8 μm. The negative electrode slurry is stirred evenly and then coated on both surfaces of the copper foil. The surface density of the copper foil coating on both sides is 15.96 mg / cm 2 Then, the aluminum foil coated with the negative electrode slurry is dried, slitting, die-cutting, rolling and slitting in sequence according to the conventional process to prepare the negative electrode sheet. The compaction density of the negative electrode sheet is 1.4g / cm 3 .

[0131] In the die-cutting process mentioned above, during the preparation of the pole piece, by precisely controlling the coating process, uncoated areas are left at both ends of the pole piece as the lug area (22mm for the positive pole piece and 13mm for the negative pole piece). Using laser cutting equipment, 22 lugs are cut out of the positive pole and 24 lugs are cut out of the negative pole in the uncoated area. The width of each lug is 4mm, and the distance between adjacent lugs is calculated (only one lug is kept in one circle). The height of the positive lug is 20mm and the height of the negative lug is 10mm, so that the lugs at both ends are in the same straight line when winding. This design ensures that the battery has lower internal resistance and higher energy density during the charging and discharging process.

[0132] 5.3 Cell Preparation

[0133] The coated positive and negative electrodes and separators are precisely aligned in the order of positive-separator-negative (the separator thickness is 14um), and then wound using an automatic winding machine. During the winding process, the winding speed and tension are strictly controlled to ensure that there are no bubbles or misalignment between the positive and negative electrodes and the separator. After winding, the battery cell is fixed with high-temperature tape to prevent deformation or loosening of the battery cell in subsequent processes.

[0134] 5.4 Battery Assembly

[0135] The wound battery cell is subjected to joint welding of the positive electrode tab and spot welding of the negative electrode tab; then the battery cell is assembled, and an electrolyte solvent is an electrolyte having a mass ratio of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate of 11:34:55 and liquid is injected to obtain a 21700 lithium-ion battery.

[0136] Comparative Example 1

[0137] Compared with Example 1, the difference is that the tab is a traditional positive electrode single tab (the tab is at 1 / 3) and the negative electrode has two tabs inside and outside.

[0138] Experimental example

[0139] The electrical properties of the 21700 lithium-ion batteries prepared according to Examples 1-5 and Comparative Example 1 are shown in Table 1:

[0140] Table 1 Electrical properties of lithium-ion batteries

[0141]

[0142] Figure 3 This is a schematic diagram comparing the internal resistance distribution of Example 1 and Comparative Example 1. It can be seen that the internal resistance of the multi-electrode tab battery cell is much lower than that of the traditional tab; Figure 4 , Figure 5 These are schematic diagrams comparing the cycle performance of Example 1 and Comparative Example 1. It can be seen that: Figure 4 The 0.5C slow charge cycle performance of Zhongduo tab battery cells is better than that of traditional tabs; Figure 5 The 1C fast charging cycle performance of multi-pole batteries is also better than that of traditional poles, reflecting the advantage of uniform current distribution of multi-pole batteries.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0144] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A high capacity 21700 lithium ion battery, characterized in that: It comprises a positive electrode sheet and a negative electrode sheet, wherein one end of the empty foil of the positive electrode sheet is provided with 6-25 positive electrode tabs, and one end of the empty foil of the negative electrode sheet is provided with 6-25 negative electrode tabs.

2. The high capacity 21700 lithium ion battery according to claim 1, characterized in that: The length of the positive electrode tab is 10-20 mm, and the width is 4-8 mm; the length of the negative electrode tab is 5-15 mm, and the width is 4-8 mm.

3. The high capacity 21700 lithium ion battery according to claim 1, characterized in that: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer arranged on the surface of the positive electrode current collector. The raw materials of the positive electrode active layer comprise a positive electrode active material, a first conductive agent, a first binder and a first solvent.

4. The high capacity 21700 lithium ion battery according to claim 3, characterized in that: At least one of the following conditions is met: a. The positive electrode active material includes a nickel-cobalt-manganese ternary material Li (Ni x Co y Mn 1-x-y )O2, where 0.7<X<0.95; b. The first conductive agent includes one or more of carbon black, multi-walled carbon tubes, and single-walled carbon tubes; c. The first binder comprises one or more of carboxymethyl cellulose, polymethyl methacrylate, and polyvinylidene fluoride; d. the first solvent comprises methyl pyrrolidone; e. The mass ratio of the positive electrode active material, the first conductive agent, and the first binder is 93-97: 1-5: 2-4.

5. The high capacity 21700 lithium ion battery according to claim 1, characterized in that: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on the surface of the negative electrode current collector. The raw materials of the negative electrode active layer comprise a negative electrode active material, a second conductive agent, a second binder, a dispersant and a second solvent.

6. The high capacity 21700 lithium ion battery according to claim 5, characterized in that: At least one of the following conditions is met: f. The negative electrode active material comprises a silicon-carbon composite material and graphite, wherein the gram capacity of the silicon-carbon composite material is 1500-2000mAh / g, and the gram capacity of the graphite is 340-360mAh / g; g. The second conductive agent includes one or more of carbon black, multi-walled carbon tubes, and single-walled carbon tubes; h. The second binder comprises carboxymethyl cellulose; i. The dispersant comprises styrene-butadiene rubber; j. The mass ratio of the negative electrode active material, the second conductive agent, the second binder, and the dispersant is 93-96: 1.5-2.5：1-1.5：1.5-3。 7. The high capacity 21700 lithium ion battery according to any one of claims 3 to 6, characterized in that: At least one of the following conditions is met: k. The positive electrode current collector comprises an aluminum foil having a thickness of 12-15 μm; l. The negative electrode current collector comprises copper foil having a thickness of 8-10 μm; m. The compaction density of the positive electrode active layer is 3.4-3.6 mg / cm 3 The compaction density of the negative electrode active layer is 1.3-1.6 mg / cm 3 .

8. A method for preparing a high-capacity 21700 lithium-ion battery, characterized in that: include: The positive electrode slurry is coated on the positive electrode current collector, and after drying, a positive electrode sheet is obtained; the negative electrode slurry is coated on the negative electrode current collector, and after drying, a negative electrode sheet is obtained; 6-25 positive electrode tabs are arranged at one end of the positive electrode sheet, and 6-25 negative electrode tabs are arranged at one end of the negative electrode sheet; The positive electrode sheet and the negative electrode sheet are rolled and then wound with a separator to form a battery core, and the negative electrode multi-pole tab is welded to the inner bottom surface of the battery shell.

9. The method for preparing a high-capacity 21700 lithium-ion battery according to claim 8, characterized in that: The positive electrode tab and the negative electrode tab are formed at two ends of the battery cell by laser cutting.

10. An electrical equipment, characterized in that: A high-capacity 21700 lithium-ion battery comprising any one of claims 1-7.

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