Cylindrical lithium ion battery with full-tab structure and preparation method of cylindrical lithium ion battery

Abstract

The invention provides a cylindrical lithium ion battery with a full tab structure and a preparation method of the cylindrical lithium ion battery, a positive plate is divided into a positive coating area and a positive reserved area, the positive coating area is coated with positive slurry, a negative plate is divided into a negative coating area and a negative reserved area, the negative coating area is coated with negative slurry, and the negative reserved area is coated with negative slurry. The positive plate and the negative plate are stacked and wound to form a battery cell, the positive coating area is opposite to the negative coating area, the positive reserved area and the negative reserved area are positioned at two ends of the battery cell, the positive reserved area and the negative reserved area are flattened to form a positive full tab and a negative full tab, the positive full tab is connected with a positive collector plate in a welding manner, and the negative collector plate is connected with a negative collector plate in a welding manner. A multi-tab stitch welding mode is replaced by a mode of flattening the positive and negative electrode full tabs and the collector plates, so that the current path is greatly increased, the battery power is greatly improved, modified artificial graphite is adopted as a negative electrode active material, the prepared battery is good in cycling stability, the capacity of the product is improved, and the service life of the product is prolonged.

Description

[Technical field]

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a cylindrical lithium ion battery with a full-tab structure and a preparation method thereof. [Background technology]

[0002] With the rapid development of science and technology, people's dependence on energy is increasing day by day. In the past 20 years, lithium-ion batteries have been widely favored by people for their advantages such as portability, environmental protection, high energy density, and strong cycle stability. At present, the rapid development of the new energy vehicle industry in recent years has driven the rapid growth of lithium-ion batteries, and put forward the demand for higher capacity and high energy density in the lithium battery industry.

[0003] At present, it is difficult for conventional lithium iron phosphate batteries to achieve high-rate charging and discharging, which limits their application and promotion in some scenarios with high-rate charging and discharging requirements. This is mainly because under high-current charging and discharging conditions, the polarization phenomenon of lithium batteries is aggravated, the electrochemical window range of the battery is widened, and the ion diffusion rate and electronic conductivity are reduced, resulting in a decrease in the battery discharge capacity; and under high-current discharge conditions, conventional lithium batteries heat up rapidly inside the battery, which may cause short circuits and safety hazards. The demand for high-current charging and discharging and instantaneous high-power application scenarios for batteries has increasingly higher requirements for high-rate charging and discharging and high-power output lithium iron phosphate battery technology.

[0004] The 46 series (46mm diameter) large cylindrical battery is recognized as an ideal cylindrical lithium-ion battery for future new energy vehicles and large-scale energy storage systems due to its large capacity, high energy density, and convenient grouping. The market conventionally adopts single-pole, double-pole, and multi-pole battery structures. The increase of poles is conducive to reducing the internal resistance and temperature rise of the battery and improving the rate performance. However, when the number of poles is large, due to the superposition of multiple poles, problems such as pole welding or welding penetration will occur, and the welding area cannot be guaranteed, which leads to increased internal resistance and uneven current conduction, and the battery cannot work for a long time with high current. How to improve the energy density, cycle stability and high-rate charge and discharge performance of the 46 series large cylindrical battery has received increasing attention from scientific researchers. Therefore, it is very necessary to develop a 46 large cylindrical battery with high battery capacity, good cycle stability, good safety and high current rate.

[0005] In view of this, it is necessary to provide a new cylindrical lithium-ion battery with a full-tab structure and a preparation method thereof to overcome the above-mentioned defects. [Summary of the invention]

[0006] The object of the present invention is to provide a cylindrical lithium-ion battery with a full-ear structure and a preparation method thereof, which has high battery capacity, good cycle stability, good safety and high current rate.

[0007] In order to achieve the above-mentioned object, in the first aspect, the present invention provides a cylindrical lithium-ion battery with a full-ear structure, comprising a positive electrode sheet, a negative electrode sheet, a positive electrode collector and a negative electrode collector; the positive electrode sheet is divided into a positive electrode coating area and a positive electrode reserved area located on one side of the positive electrode coating area, and the positive electrode coating area is coated with a positive electrode slurry; the negative electrode sheet is divided into a negative electrode coating area and a negative electrode reserved area located on one side of the negative electrode coating area, and the negative electrode coating area is coated with a negative electrode slurry; the positive electrode sheet and the negative electrode sheet are stacked After unwinding, a battery cell is formed, the positive electrode coating area is opposite to the negative electrode coating area, the positive electrode reserved area and the negative electrode reserved area are respectively located at the two ends of the battery cell, and the positive electrode reserved area and the negative electrode reserved area are respectively formed into a positive electrode full pole ear and a negative electrode full pole ear after flattening, the positive electrode full pole ear is welded and connected to the positive electrode collector plate, and the negative electrode full pole ear is welded and connected to the negative electrode collector plate; the negative electrode slurry includes a negative electrode active material, and the negative electrode active material is modified artificial graphite.

[0008] In a preferred embodiment, the positive electrode current collector includes a substrate and a tail handle, the positive electrode full tab is welded to the substrate, the tail handle is connected to the substrate, and the tail handle is located on a side of the substrate away from the positive electrode full tab.

[0009] In a preferred embodiment, the substrate is provided with a plurality of through holes, and the negative electrode current collecting disc is provided with a plurality of through holes.

[0010] In a preferred embodiment, it also includes a shell with an opening at one end and a cover plate, the battery cell is accommodated in the shell, the cover plate is arranged at the end of the shell opening, the negative electrode collector is welded to the bottom surface of the shell, and the end of the tail handle away from the base is welded to the cover plate; the shell is cylindrical, and the diameter of the shell is 46mm.

[0011] In a preferred embodiment, the positive electrode reserved area is coated with a ceramic material near the positive electrode coating area, and the ceramic material is boehmite.

[0012] In a preferred embodiment, the width of the positive electrode reserved area is 8-10 mm, the width of the negative electrode reserved area is 6-8 mm, the height of the positive electrode full tab after flattening is 2-3 mm, and the height of the negative electrode full tab after flattening is 1.5-2.5 mm.

[0013] In a preferred embodiment, the negative electrode active material is single-particle artificial graphite or secondary granulated artificial graphite.

[0014] In a preferred embodiment, the positive electrode slurry includes a positive electrode active material, and the positive electrode active material is nano-sized lithium iron phosphate.

[0015] In a preferred embodiment, the positive electrode slurry further includes a positive electrode conductive agent, and the positive electrode conductive agent is a combination of carbon nanotubes and graphene.

[0016] In a second aspect, the present invention provides a method for preparing a cylindrical lithium-ion battery with a full-tab structure, comprising the following steps:

[0017] Step S10: taking 48-53 parts of nano-lithium iron phosphate, 2-3 parts of PVDF dry powder, 1-2 parts of graphene, 8-10 parts of 10% CNT premix, and 30-38 parts of NMP, and preparing a positive electrode slurry by a semi-dry process to obtain a positive electrode slurry of a PVDF / NMP oily system;

[0018] Step S20: taking 47-52 parts of modified artificial graphite, 38-42 parts of 1.7% CMC glue, 2-5 parts of aqueous conductive agent, 2-4 parts of SBR, 1-3 parts of deionized water, and 1-3 parts of NMP, and preparing negative electrode slurry by semi-dry process to obtain negative electrode slurry of graphite / CMC / SBR aqueous system;

[0019] Step S30: applying the positive electrode slurry to the positive electrode sheet in a continuous and uniform full coating manner, and retaining a positive electrode empty foil area of ​​8-10 mm on one side of the positive electrode sheet, the position coated with the positive electrode slurry forms a positive electrode coating area, and the positive electrode empty foil area not coated with the positive electrode slurry forms a positive electrode reserved area, and the positive electrode reserved area near the positive electrode coating area is coated with a ceramic material, and the ceramic material is boehmite;

[0020] Step S40: applying the negative electrode slurry to the negative electrode sheet in a continuous and uniform full coating manner, and retaining a 6-8 mm negative electrode empty foil area on one side of the negative electrode sheet, the position coated with the negative electrode slurry forms a negative electrode coating area, and the negative electrode empty foil area not coated with the negative electrode slurry forms a negative electrode reserved area;

[0021] Step S50: After coating is completed, the positive electrode sheet and the negative electrode sheet are rolled and cut respectively by controlling the rolling thickness;

[0022] Step S60: adding a separator between the positive electrode sheet and the negative electrode sheet and winding them to form a battery cell, and then using a flattening machine to flatten the exposed positive electrode empty foil area and negative electrode empty foil area at both ends of the battery cell to form a positive electrode full tab and a negative electrode full tab respectively. After flattening, the height of the positive electrode full tab is 2-3 mm, and the height of the negative electrode full tab is 1.5-2.5 mm;

[0023] Step S70: The flattened negative electrode tab is laser welded to the negative electrode collector plate, and then spot welded to the bottom surface of the shell, and the flattened positive electrode tab is laser welded to the base of the positive electrode collector plate, and the tail handle of the positive electrode collector plate is welded to the cover plate;

[0024] Step S80: bake the assembled battery cell, inject electrolyte, seal the shell, and perform chemical separation.

[0025] Compared with the prior art, the cylindrical lithium-ion battery with a full-ear structure provided by the present invention and the preparation method thereof, the positive electrode sheet is divided into a positive electrode coating area and a positive electrode reserved area located on one side of the positive electrode coating area, the positive electrode coating area is coated with a positive electrode slurry, the negative electrode sheet is divided into a negative electrode coating area and a negative electrode reserved area located on one side of the negative electrode coating area, the negative electrode coating area is coated with a negative electrode slurry, the positive electrode sheet and the negative electrode sheet are stacked and wound to form a battery cell, the positive electrode coating area is opposite to the negative electrode coating area, and the positive electrode reserved area and the negative electrode reserved area are respectively located at two ends of the battery cell, and the positive electrode reserved area, The negative electrode reserved area is flattened to form a positive electrode full pole ear and a negative electrode full pole ear respectively. The positive electrode full pole ear is welded and connected to the positive electrode collector plate, and the negative electrode full pole ear is welded and connected to the negative electrode collector plate. The positive and negative electrode full pole ear flattening and current collector plate method are used instead of the multi-pole ear stacking method, which greatly increases the current path and thus greatly improves the battery power. In addition, modified artificial graphite is used as the negative electrode active material. The battery prepared has high capacity, good cycle stability, good safety, and achieves high-rate charge and discharge, while improving the capacity and life of the product.

Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A structural diagram of a positive electrode sheet in a cylindrical lithium-ion battery with a full-tab structure provided by the present invention;

[0028] Figure 2 A structural diagram of a negative electrode sheet in a cylindrical lithium-ion battery with a full-tab structure provided by the present invention;

[0029] Figure 3 A structural diagram of a positive electrode current collecting disk in a cylindrical lithium-ion battery with a full-tab structure provided by the present invention;

[0030] Figure 4 This is a structural diagram of the negative electrode current collecting disk in the cylindrical lithium-ion battery with a full-tab structure provided by the present invention. [Specific implementation method]

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0032] See also Figures 1 to 4 The cylindrical lithium-ion battery with a full-tab structure provided by the present invention includes a positive electrode sheet 10, a negative electrode sheet 20, a positive electrode current collecting plate 30 and a negative electrode current collecting plate 40.

[0033] Specifically, the positive electrode sheet 10 is divided into a positive electrode coating area 101 and a positive electrode reserved area 102 located on one side of the positive electrode coating area 101, and the positive electrode coating area 101 is coated with positive electrode slurry 11. The negative electrode sheet 20 is divided into a negative electrode coating area 201 and a negative electrode reserved area 202 located on one side of the negative electrode coating area 201, and the negative electrode coating area 202 is coated with negative electrode slurry 21. The positive electrode sheet 10 and the negative electrode sheet 20 are stacked and wound to form a battery cell, the positive electrode coating area 101 is opposite to the negative electrode coating area 201, the positive electrode reserved area 102 and the negative electrode reserved area 201 are respectively located at the two ends of the battery cell, the positive electrode reserved area 102 and the negative electrode reserved area 202 are flattened to form a positive electrode full pole ear and a negative electrode full pole ear respectively, the positive electrode full pole ear is welded to the positive electrode collector plate 30, and the negative electrode full pole ear is welded to the negative electrode collector plate 40.

[0034] It can be understood that the positive electrode sheet 10 is provided with a positive electrode reserved area 102, and the positive electrode reserved area 102 is not coated with positive electrode slurry, and the negative electrode sheet 20 is provided with a negative electrode reserved area 202, and the negative electrode reserved area 202 is not coated with negative electrode slurry. After the positive electrode sheet 10 and the negative electrode sheet 20 are stacked, the positive electrode coating area 101 coated with positive electrode slurry and the negative electrode coating area 201 coated with negative electrode slurry are opposite to each other, and the positive electrode reserved area 102 exceeds the edge of the negative electrode sheet 20, and the negative electrode reserved area 202 exceeds the edge of the positive electrode sheet 10. After winding, the positive electrode reserved area 102 and the negative electrode reserved area 202 are respectively located at the two ends of the battery cell, and the positive electrode reserved area 102 and the negative electrode reserved area 202 are respectively formed into a positive electrode full pole ear and a negative electrode full pole ear after flattening, and the positive electrode full pole ear and the positive electrode full pole ear are connected to each other. The current collecting disk 30 is welded and connected, and the negative electrode full pole ear is welded and connected to the negative electrode current collecting disk 40, that is, the positive electrode full pole ear and the negative electrode full pole ear are all led out through the positive electrode current collecting disk 30 and the negative electrode current collecting disk 40 respectively, and the positive electrode full pole ear and the negative electrode full pole ear are welded to the positive electrode current collecting disk 30 and the negative electrode current collecting disk 40 respectively, which can increase the welding surface connection, and the welding points are evenly distributed, which can improve the current flow capacity, shorten the migration path of electrons during the charging and discharging process, improve the charging and discharging efficiency of the battery, and can increase the current conduction area, reduce losses, make the battery heat dissipation better, and improve safety.

[0035] The negative electrode slurry includes a negative electrode active material, and the negative electrode active material is modified artificial graphite. The negative electrode active material mainly selects artificial graphite modified by coating amorphous carbon, and amorphous carbon is divided into soft carbon and hard carbon, among which soft carbon coating is preferred. After modification, structural optimization and process improvement, artificial graphite covers the active sites on the graphite surface, reduces the occurrence of irreversible side reactions, inhibits the formation of SEI film, restricts and buffers the volume expansion of graphite, and increases the stability of the cycle.

[0036] The present invention provides a cylindrical lithium-ion battery with a full-ear structure, wherein the positive electrode sheet 10 is divided into a positive electrode coating area 101 and a positive electrode reserved area 102 located on one side of the positive electrode coating area 101, the positive electrode coating area 101 is coated with a positive electrode slurry 11, the negative electrode sheet 20 is divided into a negative electrode coating area 201 and a negative electrode reserved area 202 located on one side of the negative electrode coating area 201, the negative electrode coating area 202 is coated with a negative electrode slurry 21, the positive electrode sheet 10 and the negative electrode sheet 20 are stacked and wound to form a battery cell, the positive electrode coating area 101 is opposite to the negative electrode coating area 201, and the positive electrode reserved area 102 and the negative electrode reserved area 201 are respectively located at the At both ends of the battery cell, the positive electrode reserved area 102 and the negative electrode reserved area 202 are flattened to form a positive electrode full pole ear and a negative electrode full pole ear respectively. The positive electrode full pole ear is welded to the positive electrode collector plate 30, and the negative electrode full pole ear is welded to the negative electrode collector plate 40. The positive and negative electrode full pole ear flattening and current collector plate method is used instead of the multi-pole ear stacking method, which greatly increases the current path and thus greatly improves the battery power. In addition, modified artificial graphite is used as the negative electrode active material, and the resulting battery has high capacity, good cycle stability, good safety, and achieves high-rate charge and discharge, while improving the capacity and life of the product.

[0037] Please also read Figure 3 and Figure 4 The positive electrode current collector 30 includes a substrate 31 and a tail handle 32. Both the substrate 31 and the tail handle 32 are made of pure aluminum. The positive electrode full tab is welded on the substrate 31. The tail handle 32 is connected to the substrate 31, and the tail handle 32 is located on the side of the substrate 31 away from the positive electrode full tab. The substrate 31 is specifically a circular sheet. The substrate 31 is provided with a plurality of through holes 311. The plurality of through holes 311 can be of different shapes and are provided at different positions. The through hole 311 is provided in the middle of the substrate 31. By increasing the holes of the current collector, the flow rate of liquid and gas is increased, and the liquid is quickly discharged and the gas is exhausted during liquid injection. The entire positive pole ear is laser welded to the collector plate base 31, and then the collector plate tail handle 32 is welded to the cover plate. By adding the collector plate between the ear and the cover plate, it not only increases the current rate during charging and discharging of the battery cell, reduces the heat generated in the process, reduces the internal resistance of the battery, but also effectively prevents the ear from being poorly welded and short-circuited by hitting the wall.

[0038] The negative electrode collector disc 40 is made of pure nickel or nickel-copper material. The negative electrode collector disc 40 is provided with a plurality of through holes 401. The plurality of through holes 401 are of different shapes and are provided at different positions. The through holes are provided in the negative electrode collector disc 40. By increasing the holes of the collector disc, the electrolyte is quickly spread at the bottom when the electrolyte is discharged, the liquid absorption speed is increased, and the production efficiency is improved. The negative electrode full pole ear is laser welded on the negative electrode collector disc, and the negative electrode full pole ear, the negative electrode collector disc, and the steel shell (i.e., the shell) are welded into one by spot welding.

[0039] Furthermore, the cylindrical lithium-ion battery with full-ear structure also includes a shell with an opening at one end and a cover plate, the battery cell is accommodated in the shell, the cover plate is arranged at one end of the shell opening, the negative electrode collector plate 40 is welded on the bottom surface of the shell, and the end of the tail handle 32 away from the base 31 is welded to the cover plate; the shell is cylindrical, and the diameter of the shell is 46mm. It can be understood that the shell has a receiving space, the positive electrode sheet 10, the diaphragm and the negative electrode sheet 30 are stacked and wound to form the battery cell, the battery cell is accommodated in the receiving space, and the positive electrode collector plate 30 and the negative electrode collector plate 40 are respectively located at the two ends of the battery cell 20. The diameter of the shell is 46mm, that is, the battery is a 46 series large cylindrical battery, which has the advantages of large capacity, high energy density, convenient grouping, etc., and has good application prospects.

[0040] Furthermore, the positive electrode reserved area 102 is coated with a ceramic material 12 near the positive electrode coating area 101, and the ceramic material is boehmite. High-purity boehmite is coated on the edge of the positive electrode of the lithium battery, and its particle size D50 is about 2 microns. Compared with traditional alumina, boehmite is slightly softer and has better dispersibility. It can be more effectively and evenly coated on the pole piece during the coating process, and the damage to the cutting tool is less than that of alumina. In addition, it can greatly reduce the risk of cutting burrs, effectively control burrs, and ensure the safety performance of the battery.

[0041] Specifically, the width of the positive electrode reserved area is 8-10mm, the width of the negative electrode reserved area is 6-8mm, the height of the positive electrode full pole ear after flattening is 2-3mm, and the height of the negative electrode full pole ear after flattening is 1.5-2.5mm. The positive electrode sheet is aluminum foil, and the negative electrode sheet is copper foil, that is, after flattening, the height of the positive electrode empty aluminum foil is 2-3mm, and the height of the negative electrode empty copper foil is 1.5-2.5mm. It can be understood that a suitable reserved area width is conducive to the subsequent flattening operation, thereby achieving a moderate height of the pole ear after flattening, which is further conducive to the subsequent welding operation.

[0042] Furthermore, the negative electrode active material is single-particle artificial graphite or secondary granulated artificial graphite. Single-particle artificial graphite is made from coal-based needle coke, and is crushed and graphitized to obtain primary particle negative electrode materials. Primary particle negative electrode materials have high capacity, good structural stability, and are easy to be compacted. However, primary particle negative electrode materials are prone to battery expansion, and the initial coulomb efficiency is low. Secondary granulation is to add coating materials and additives to small-particle petroleum coke, needle coke and other substrates, and then granulate the small-particle substrate under high-temperature stirring conditions to form a larger-particle product. The secondary particle negative electrode material prepared by the granulation process has the advantages of large compaction density of large particles and large specific surface area of ​​small particles. It has many lithium ion migration channels, short paths, and good rate performance, which can improve the charge and discharge rate, high and low temperature performance, and cycle performance of the negative electrode material.

[0043] The positive electrode slurry includes a positive electrode active material, and the positive electrode active material is any one or more combinations of lithium iron phosphate, lithium iron manganese phosphate and nickel cobalt manganese oxide ternary materials, preferably nano-lithium iron phosphate, with a general structural formula of LiFePO4. Nano-lithium iron phosphate with smaller particles than conventional lithium iron phosphate is used. Nano-lithium iron phosphate has high rate performance and can greatly improve the ion diffusion rate of lithium iron phosphate. At the same time, the lithium iron phosphate material is nano-granulated to reduce the diffusion distance of lithium ions in the grains and improve the diffusion rate of lithium ions.

[0044] The positive electrode slurry also includes a positive electrode conductive agent, which includes a combination of one or more of carbon nanotubes, conductive carbon black and graphene, preferably a combination of carbon nanotubes and graphene. Graphene has a unique two-dimensional layered nanostructure and a huge specific surface area. The mixture of graphene and small-diameter carbon nanotubes can construct an efficient conductive network, which can effectively wrap lithium iron phosphate particles and other auxiliary materials, and its conductive performance is greatly improved.

[0045] The present invention also provides a method for preparing a cylindrical lithium-ion battery with a full-tab structure, comprising the following steps:

[0046] Step S10: Take 48-53 parts of nano-lithium iron phosphate, 2-3 parts of PVDF dry powder, 1-2 parts of graphene, 8-10 parts of 10% CNT premix, and 30-38 parts of NMP, and prepare positive electrode slurry by semi-dry process to obtain positive electrode slurry of PVDF / NMP oily system; specifically, the positive electrode slurry is prepared by semi-dry process, and the basic process is mixing active material, conductive agent and binder dry powder - adding appropriate amount of solvent to moisten - adding solvent to disperse and crush at high speed - diluting to adjust viscosity, and the prepared positive electrode slurry is a black moist and viscous liquid.

[0047] Step S20: Take 47-52 parts of modified artificial graphite, 38-42 parts of 1.7% CMC glue, 2-5 parts of aqueous conductive agent, 2-4 parts of SBR and 1-3 parts of deionized water, 1-3 parts of NMP, and prepare negative electrode slurry by semi-dry process to obtain negative electrode slurry of graphite / CMC / SBR aqueous system; specifically, the negative electrode slurry is prepared by semi-dry process, and the basic process is mixing active material, conductive agent and binder dry powder - adding appropriate amount of solvent to moisten - adding solvent to disperse and crush at high speed - diluting to adjust viscosity, and the prepared negative electrode slurry is a light gray moist and viscous liquid.

[0048] Step S30: The positive electrode slurry is applied to the positive electrode sheet in a continuous and uniform full-coating manner, and an 8-10 mm positive electrode empty foil area is reserved on one side of the positive electrode sheet, the position coated with the positive electrode slurry forms a positive electrode coating area, and the positive electrode empty foil area not coated with the positive electrode slurry forms a positive electrode reserved area, and the positive electrode reserved area is coated with a ceramic material near the positive electrode coating area, and the ceramic material is boehmite.

[0049] Step S40: applying the negative electrode slurry to the negative electrode sheet in a continuous and uniform full-coating manner, and retaining a 6-8 mm negative electrode empty foil area on one side of the negative electrode sheet. The position coated with the negative electrode slurry forms a negative electrode coating area, and the negative electrode empty foil area not coated with the negative electrode slurry forms a negative electrode reserved area.

[0050] Step S50: After coating is completed, the positive electrode sheet and the negative electrode sheet are rolled and cut respectively by controlling the rolling thickness.

[0051] Step S60: Add a separator between the positive electrode sheet and the negative electrode sheet and wind them to form a battery cell. After winding, use a flattening machine to flatten the exposed positive electrode empty foil area and negative electrode empty foil area at both ends of the battery cell to form a positive electrode full ear and a negative electrode full ear respectively. After flattening, the height of the positive electrode full ear is 2-3mm, and the height of the negative electrode full ear is 1.5-2.5mm.

[0052] Step S70: The flattened negative electrode tab is laser welded to the negative electrode collector plate, and then spot welded to the bottom surface of the shell; the flattened positive electrode tab is laser welded to the base of the positive electrode collector plate, and the tail handle of the positive electrode collector plate is welded to the cover plate.

[0053] Step S80: bake the assembled battery cell, inject electrolyte, seal the shell, and perform chemical separation.

[0054] The cylindrical lithium-ion battery with full-tab structure and the preparation method thereof provided by the present invention are tested through several embodiments.

[0055] Embodiment 1:

[0056] Preparation of positive electrode sheet: 51 parts of nano-lithium iron phosphate, 1.5 parts of graphene, and 2.5 parts of PVDF dry powder are stirred at a speed of 30r / min for 30min, and the dry powders are mixed evenly; 9 parts of 10% CNT premix and 36 parts of NMP solvent are added, and the mixture is stirred slowly at 20r / min for 30min, and then stirred at a high speed of 30r / min for 180min, the powder particles are first wetted, and then the particle agglomerates are crushed and dispersed by high-speed stirring, and the viscosity is adjusted after sufficient mixing to obtain positive electrode slurry. The positive electrode slurry is applied to the aluminum foil by continuous and uniform full coating. When the positive electrode is coated, 8-10mm of empty aluminum foil is retained on one side of the electrode sheet to form a material area, boehmite and empty aluminum foil. The positive electrode is rolled and cut to obtain a positive electrode sheet.

[0057] Preparation of negative electrode sheet: Add 50 parts of single-particle artificial graphite, 40 parts of 1.7% CMC glue, stir at 20r / min for 30min, mix evenly; add 4 parts of aqueous conductive agent, stir at 30r / min for 180min, break and disperse the particle agglomerates, and finally add 2 parts of SBR, 2 parts of NMP, and 2 parts of deionized water, stir at 20r / min for 30min, mix well and adjust the viscosity to obtain negative electrode slurry. Apply the negative electrode slurry to the copper foil by continuous and uniform full coating, leaving 6-8mm of empty copper foil on one side of the electrode sheet to form a material area and empty copper foil. Roll and cut the negative electrode to obtain a negative electrode sheet.

[0058] Winding and flattening: Add a separator between the positive and negative electrodes for winding. After winding, use a flattening machine to flatten the empty aluminum foil and empty copper foil exposed at both ends of the core.

[0059] Foil surface welding: After being flattened, the entire negative electrode tab is laser welded to the negative electrode collector plate, and then spot welded to the bottom of the steel shell. After being flattened, the entire positive electrode tab is laser welded to the positive electrode collector plate, and the lead-out positive electrode collector plate conductive handle can be directly welded to the cover plate.

[0060] Liquid injection: Bake the assembled battery cells, inject electrolyte and seal.

[0061] Composition and capacity division: The finished batteries are subjected to composition and capacity division.

[0062] Embodiment 2:

[0063] Preparation of positive electrode sheet: 51 parts of nano-lithium iron phosphate, 1.5 parts of graphene, and 2.5 parts of PVDF dry powder are stirred at a speed of 30r / min for 30min, and the dry powders are mixed evenly; 9 parts of 10% CNT premix and 36 parts of NMP solvent are added, and the mixture is stirred slowly at 20r / min for 30min, and then stirred at a high speed of 30r / min for 180min, the powder particles are first wetted, and then the particle agglomerates are crushed and dispersed by high-speed stirring, and the viscosity is adjusted after sufficient mixing to obtain positive electrode slurry. The positive electrode slurry is applied to the aluminum foil by continuous and uniform full coating. When the positive electrode is coated, 8-10mm of empty aluminum foil is retained on one side of the electrode sheet to form a material area, boehmite and empty aluminum foil. The positive electrode is rolled and cut to obtain a positive electrode sheet.

[0064] Preparation of negative electrode sheet: Add 50 parts of secondary granulated artificial graphite, 40 parts of 1.7% CMC glue, stir at 20r / min for 30min, mix evenly; add 4 parts of aqueous conductive agent, stir at 30r / min for 180min, break and disperse the particle agglomerates, finally add 2 parts of SBR, 2 parts of NMP, 2 parts of deionized water, stir at 20r / min for 30min, mix well and adjust the viscosity to obtain negative electrode slurry. Apply the negative electrode slurry to the copper foil by continuous and uniform full coating, leaving 6-8mm of empty copper foil on one side of the electrode sheet to form a material area and empty copper foil. Roll and cut the negative electrode to obtain the negative electrode sheet.

[0065] Winding and flattening: Add a separator between the positive and negative electrodes for winding. After winding, use a flattening machine to flatten the empty aluminum foil and empty copper foil exposed at both ends of the core.

[0066] Foil surface welding: After being flattened, the entire negative electrode tab is laser welded to the negative electrode collector plate, and then spot welded to the bottom of the steel shell. After being flattened, the entire positive electrode tab is laser welded to the positive electrode collector plate, and the lead-out positive electrode collector plate conductive handle can be directly welded to the cover plate.

[0067] Liquid injection: Bake the assembled battery cells, inject electrolyte and seal.

[0068] Composition and capacity division: The finished batteries are subjected to composition and capacity division.

[0069] Comparative Example 1:

[0070] Preparation of positive electrode sheet: 51 parts of nano-lithium iron phosphate, 1.5 parts of graphene, and 2.5 parts of PVDF dry powder are stirred at a speed of 30r / min for 30min, and the dry powders are mixed evenly; 9 parts of 10% CNT premix and 36 parts of NMP solvent are added, and the mixture is stirred slowly at 20r / min for 30min, and then stirred at a high speed of 30r / min for 180min, the powder particles are first wetted, and then the particle agglomerates are crushed and dispersed by high-speed stirring, and the viscosity is adjusted after sufficient mixing to obtain positive electrode slurry. The positive electrode slurry is applied to the aluminum foil by continuous and uniform full coating. When the positive electrode is coated, 8-10mm of empty aluminum foil is retained on one side of the electrode sheet to form a material area, boehmite and empty aluminum foil. The positive electrode is rolled and cut to obtain a positive electrode sheet.

[0071] Preparation of negative electrode sheet: add 50 parts of normal artificial graphite, 40 parts of 1.7% CMC glue, stir at 20r / min for 30min, mix evenly; add 4 parts of aqueous conductive agent, stir at 30r / min for 180min, break and disperse the particle agglomerates, finally add 2 parts of SBR, 2 parts of NMP, 2 parts of deionized water, stir at 20r / min for 30min, mix well and adjust the viscosity to obtain negative electrode slurry. Apply the negative electrode slurry to the copper foil by continuous and uniform full coating, leaving 6-8mm of empty copper foil on one side of the electrode sheet to form a material area and empty copper foil. Roll and cut the negative electrode to obtain the negative electrode sheet.

[0072] Winding and flattening: Add a separator between the positive and negative electrodes for winding. After winding, use a flattening machine to flatten the empty aluminum foil and empty copper foil exposed at both ends of the core.

[0073] Foil surface welding: After being flattened, the entire negative electrode tab is laser welded to the negative electrode collector plate, and then spot welded to the bottom of the steel shell. After being flattened, the entire positive electrode tab is laser welded to the positive electrode collector plate, and the lead-out positive electrode collector plate conductive handle can be directly welded to the cover plate.

[0074] Liquid injection: Bake the assembled battery cells, inject electrolyte and seal.

[0075] Composition and capacity division: The finished batteries are subjected to composition and capacity division.

[0076] Please refer to the following Table 1, which is a comparison table of the 1C cycle performance of large cylindrical batteries prepared in Examples 1-2 and Comparative Example 1 at room temperature.

[0077] Table 1

[0078]

[0079] Please refer to the following Table 2, which is a comparison table of the 3C cycle performance of large cylindrical batteries prepared in Examples 1 to 2 and Comparative Example 1 at room temperature.

[0080] Table 2

[0081]

[0082] It can be seen from Table 1 that in Examples 1-2, the capacity retention rate of the prepared large cylindrical battery with full tabs can reach more than 92% after 600 cycles at 1C at room temperature, and the capacity retention rate can reach more than 88% after 1200 cycles, and has excellent performance.

[0083] It can be seen from Table 2 that in Examples 1-2, the capacity retention rate of the prepared large cylindrical battery with full tabs can reach more than 90% after 600 cycles at room temperature 3C, and the capacity retention rate can reach more than 80% after 1200 cycles, and has excellent performance.

[0084] Combining Table 1 and Table 2, it can be seen that in Examples 1-2 and Comparative Example 1, the degree of excellence of battery capacity and internal resistance performance is: secondary granulated artificial graphite modified negative electrode material > single particle artificial graphite modified negative electrode material > normal artificial graphite negative electrode material. The large cylindrical lithium battery prepared with secondary granulated artificial graphite modified negative electrode material has a lower internal resistance and a higher capacity.

[0085] Combining Table 1 and Table 2, it can be seen that in Examples 1-2 and Comparative Example 1, the degree of excellence in cycle performance is: secondary granulated artificial graphite modified negative electrode material > single particle artificial graphite modified negative electrode material > normal artificial graphite negative electrode material. The large cylindrical lithium battery prepared from the secondary granulated artificial graphite modified negative electrode material has better 1C cycle performance at room temperature, and the 3C high rate cycle performance is also better. The secondary particle negative electrode material prepared by the granulation process has many lithium ion migration channels, short paths, and good rate performance, which can achieve the improvement of the charge and discharge rate, high and low temperature performance, and cycle performance of the negative electrode material.

[0086] In summary, the cylindrical lithium-ion battery with full-tab structure and the preparation method thereof provided by the present invention have the following beneficial effects:

[0087] The high-rate large cylindrical lithium-ion battery with a full-ear structure in the present invention is manufactured by optimizing nano-lithium iron phosphate positive electrode materials, modified artificial graphite negative electrode materials, and graphene composite conductive agents to produce a high-rate and long-cycle 46 large cylindrical lithium iron phosphate battery, thereby achieving high-rate charge and discharge, and at the same time improving the capacity and life of the product.

[0088] The semi-dry mixing process is adopted. The basic process is to mix the active material, conductive agent and binder dry powder - add an appropriate amount of solvent to moisten - add solvent to disperse and crush large particles at high speed - and then dilute to adjust the slurry viscosity. When the slurry is stirred at ultra-high viscosity, the large shear force can more fully disperse the large particles, making the particle clusters smaller, allowing the conductive agent to evenly coat the active material, and at the same time it is more conducive to the dissolution and stability of the binder. The slurry produced by this process has excellent viscosity, fineness, solid content consistency and stability, and the resistivity of the battery cell is low, and the battery cell capacity retention rate is higher.

[0089] The 46 series large cylindrical battery adopts the method of flattening the positive and negative poles and collecting plates, which greatly increases the current path and greatly improves the battery power. The positive and negative poles are welded to the collecting plates, and the welding points are evenly distributed, which can increase the welding area, improve the current capacity, shorten the migration path of electrons during the charging and discharging process, and improve the charging and discharging efficiency of the battery; on the other hand, it increases the area of ​​current conduction, reduces losses, makes the battery heat dissipation better, and improves safety.

[0090] The above description is only an implementation mode of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A cylindrical lithium-ion battery with a full-tab structure, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet, a positive electrode collector plate and a negative electrode collector plate; the positive electrode sheet is divided into a positive electrode coating area and a positive electrode reserved area located on one side of the positive electrode coating area, the positive electrode coating area is coated with positive electrode slurry, and the negative electrode sheet is divided into a negative electrode coating area and a negative electrode reserved area located on one side of the negative electrode coating area, the negative electrode coating area is coated with negative electrode slurry; the positive electrode sheet and the negative electrode sheet are stacked and wound to form a battery cell, the positive electrode coating area is opposite to the negative electrode coating area, the positive electrode reserved area and the negative electrode reserved area are respectively located at two ends of the battery cell, the positive electrode reserved area and the negative electrode reserved area are flattened to form a positive electrode full pole ear and a negative electrode full pole ear respectively, the positive electrode full pole ear is welded to the positive current collector plate, and the negative electrode full pole ear is welded to the negative current collector plate; the negative electrode slurry comprises a negative electrode active material, and the negative electrode active material is modified artificial graphite.

2. The cylindrical lithium-ion battery with full tab structure as claimed in claim 1, characterized in that: The positive electrode current collector comprises a base and a tail handle, the positive electrode full tab is welded on the base, the tail handle is connected to the base, and the tail handle is located on a side of the base away from the positive electrode full tab.

3. The cylindrical lithium-ion battery with full tab structure as claimed in claim 2, characterized in that: The substrate is provided with a plurality of through holes, and the negative electrode current collecting plate is provided with a plurality of through holes.

4. The cylindrical lithium-ion battery with full tab structure as claimed in claim 2, characterized in that: It also includes a shell with an opening at one end and a cover plate, the battery cell is accommodated in the shell, the cover plate is arranged at the end of the shell opening, the negative electrode collector is welded to the bottom surface of the shell, and the end of the tail handle away from the base is welded to the cover plate; the shell is cylindrical, and the diameter of the shell is 46mm.

5. The cylindrical lithium-ion battery with full tab structure as claimed in claim 1, characterized in that: The positive electrode reserved area is coated with a ceramic material near the positive electrode coating area, and the ceramic material is boehmite.

6. The cylindrical lithium-ion battery with full tab structure as claimed in claim 1, characterized in that: The width of the positive electrode reserved area is 8-10mm, the width of the negative electrode reserved area is 6-8mm, the height of the positive electrode full tab after flattening is 2-3mm, and the height of the negative electrode full tab after flattening is 1.5-2.5mm.

7. The cylindrical lithium-ion battery with full tab structure as claimed in claim 1, characterized in that: The negative electrode active material is single-particle artificial graphite or secondary granulated artificial graphite.

8. The cylindrical lithium-ion battery with full tab structure as claimed in claim 1, characterized in that: The positive electrode slurry comprises a positive electrode active material, and the positive electrode active material is nano-lithium iron phosphate.

9. The cylindrical lithium-ion battery with full tab structure according to any one of claims 1 to 8, characterized in that: The positive electrode slurry further includes a positive electrode conductive agent, and the positive electrode conductive agent is a combination of carbon nanotubes and graphene.

10. A method for preparing a cylindrical lithium-ion battery with a full-tab structure, characterized in that: The steps include: Step S10: taking 48-53 parts of nano-lithium iron phosphate, 2-3 parts of PVDF dry powder, 1-2 parts of graphene, 8-10 parts of 10% CNT premix, and 30-38 parts of NMP, and preparing a positive electrode slurry by a semi-dry process to obtain a positive electrode slurry of a PVDF / NMP oily system; Step S20: taking 47-52 parts of modified artificial graphite, 38-42 parts of 1.7% CMC glue, 2-5 parts of aqueous conductive agent, 2-4 parts of SBR, 1-3 parts of deionized water, and 1-3 parts of NMP, and preparing negative electrode slurry by semi-dry process to obtain negative electrode slurry of graphite / CMC / SBR aqueous system; Step S30: applying the positive electrode slurry to the positive electrode sheet in a continuous and uniform full coating manner, and retaining a positive electrode empty foil area of ​​8-10 mm on one side of the positive electrode sheet, the position coated with the positive electrode slurry forms a positive electrode coating area, and the positive electrode empty foil area not coated with the positive electrode slurry forms a positive electrode reserved area, and the positive electrode reserved area near the positive electrode coating area is coated with a ceramic material, and the ceramic material is boehmite; Step S40: applying the negative electrode slurry to the negative electrode sheet in a continuous and uniform full coating manner, and retaining a 6-8 mm negative electrode empty foil area on one side of the negative electrode sheet, the position coated with the negative electrode slurry forms a negative electrode coating area, and the negative electrode empty foil area not coated with the negative electrode slurry forms a negative electrode reserved area; Step S50: After coating is completed, the positive electrode sheet and the negative electrode sheet are rolled and cut respectively by controlling the rolling thickness; Step S60: adding a separator between the positive electrode sheet and the negative electrode sheet and winding them to form a battery cell, and then using a flattening machine to flatten the exposed positive electrode empty foil area and negative electrode empty foil area at both ends of the battery cell to form a positive electrode full tab and a negative electrode full tab respectively. After flattening, the height of the positive electrode full tab is 2-3 mm, and the height of the negative electrode full tab is 1.5-2.5 mm; Step S70: The flattened negative electrode tab is laser welded to the negative electrode collector plate, and then spot welded to the bottom surface of the shell, and the flattened positive electrode tab is laser welded to the base of the positive electrode collector plate, and the tail handle of the positive electrode collector plate is welded to the cover plate; Step S80: bake the assembled battery cell, inject electrolyte, seal the shell, and perform chemical separation.

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