A winding type battery pole group and a lithium ion battery

Abstract

The application discloses a winding type battery pole group, which comprises a positive pole sheet, a negative pole sheet and a diaphragm between the positive pole sheet and the negative pole sheet; the winding type battery pole group comprises a winding corner area part of the pole group and a winding straight area part of the pole group; the winding corner area part of the pole group is located at two ends of the winding straight area part of the pole group; the diaphragm, the negative pole sheet and the positive pole sheet all comprise a first area part and a second area part; the first area part of the diaphragm, the negative pole sheet and the positive pole sheet is in the winding corner area part of the pole group, and the second area part of the diaphragm, the negative pole sheet and the positive pole sheet is in the winding straight area part of the pole group. In addition, the application further discloses a lithium ion battery. The application is scientific in design, and through the novel structural design of the positive pole sheet, the negative pole sheet and the diaphragm in the pole group and the structural innovation of the battery shell, the winding corner lithium precipitation problem of the winding type battery can be effectively solved, so that the cycle performance and the safety performance of the battery are improved.

Description

TECHNICAL FIELD

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

[0002] At present, the demand for power batteries of electric vehicle enterprises is increasing, at the same time, the energy density and cycle life of power batteries of electric vehicles are put forward higher requirements, therefore, developing high specific energy, long cycle life power battery is one of the important directions of future development.

[0003] Power batteries can be divided into soft package batteries, cylindrical batteries and square aluminum shell batteries, among which, square aluminum shell batteries can be divided into wound type and wound type according to the assembly process. The wound battery is the mainstream type of power battery at present because of high production efficiency and convenient preparation.

[0004] For the wound battery, due to the existence of the winding corner, the outer side of the negative pole corner is covered by the inner side of the positive pole corner, so that the ratio of the negative active material capacity to the positive active material capacity at this place is small (compared with the large surface of the pole group), thereby lithium precipitation is easily generated, which reduces the cycle life and safety performance of the battery.

[0005] In addition, for the wound battery, during the long-term charging and discharging process, the positive and negative pole breathing type expansion and contraction exert pressure on the corner, so that the current density of the pole at the corner is higher than that of the pole at the large surface of the pole group, thereby there is also a risk of lithium precipitation, which reduces the cycle life and safety performance of the battery. SUMMARY

[0006] The purpose of the present application is to provide a wound battery pole group and a lithium ion battery to solve the technical defects in the prior art.

[0007] To this end, the present application provides a wound battery pole group, comprising a positive pole, a negative pole and a separator between the positive pole and the negative pole;

[0008] The wound battery pole group comprises a winding corner area part of the pole group and a winding straight area part of the pole group;

[0009] The winding corner area part of the pole group is located at both ends of the winding straight area part of the pole group;

[0010] Among them, the separator, the positive pole and the negative pole all contain a first area part and a second area part;

[0011] The first area part of the separator, the positive pole and the negative pole is in the winding corner area part of the pole group, and the second area part of the separator, the positive pole and the negative pole is in the winding straight area part of the pole group;

[0012] The content of the conductive agent in the first area part of the positive electrode sheet is higher than the content of the conductive agent in the second area part of the positive electrode sheet;

[0013] The particle size of the positive electrode active material particles in the first area part of the positive electrode sheet is smaller than the particle size of the positive electrode active material particles in the second area part of the positive electrode sheet;

[0014] The content of the conductive agent in the first area part of the negative electrode sheet is higher than the content of the conductive agent in the second area part of the negative electrode sheet;

[0015] The particle size of the negative electrode active material particles in the first area part of the negative electrode sheet is smaller than the particle size of the negative electrode active material particles in the second area part of the negative electrode sheet;

[0016] The graphitization degree of the negative electrode active material particles in the first area part of the negative electrode sheet is lower than the content of the conductive agent in the second area part of the negative electrode sheet;

[0017] The impedance of the binder in the first area part of the negative electrode sheet is lower than the impedance of the binder in the second area part of the negative electrode sheet.

[0018] In addition, the present application also provides a lithium ion battery comprising the wound battery pole group according to any one of the claims;

[0019] The wound battery pole group is located in the inner cavity of the hollow, top-opened square battery aluminum shell;

[0020] The top of the square battery aluminum shell is sealed with the battery cover plate;

[0021] The square battery aluminum shell is filled with electrolyte.

[0022] As can be seen from the technical solutions provided by the present application, compared with the prior art, the present application provides a wound battery pole group and a lithium ion battery, which are designed scientifically, and through the novel structural design of the positive electrode sheet, the negative electrode sheet and the separator in the pole group and the structural innovation of the battery shell, the problem of lithium precipitation at the winding corner of the wound battery can be effectively solved, thereby improving the cycle performance and safety performance of the battery, and having great production practical significance. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application provides a structural schematic diagram of a wound battery pole group;

[0024] Figure 2 The present application provides a schematic diagram of the overall appearance structure of a lithium ion battery;

[0025] Figure 3 The present application provides a schematic diagram of the internal structure of a lithium ion battery. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0028] The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] Referring to Figure 1 The present application provides a wound battery pole group, comprising a positive pole sheet 1001, a negative pole sheet, and a separator 1003 between the positive pole sheet 1001 and the negative pole sheet 1002;

[0030] The wound battery pole group comprises a wound corner area portion 101 of the pole group and a wound flat area portion 102 of the pole group;

[0031] The wound corner area portion 101 of the pole group is located at both ends of the wound flat area portion 102 of the pole group;

[0032] The positive pole sheet, the negative pole sheet, and the separator in the wound battery pole group each comprise a wound corner area portion and a wound flat area portion;

[0033] It should be noted that the wound battery pole group is divided into a wound corner area portion of the pole group and a wound flat area portion of the pole group along the winding direction.

[0034] In the present application, the winding flat area part of the winding type battery pole group, the positive electrode sheet, the negative electrode sheet and the separator is respectively the part having a linear distribution state in the winding type battery pole group, the positive electrode sheet, the negative electrode sheet and the separator. And the winding corner area part of the winding type battery pole group, the positive electrode sheet, the negative electrode sheet and the separator is the part (i.e. the remaining part) other than the "winding flat area part" in the winding type battery pole group, the positive electrode sheet, the negative electrode sheet and the separator.

[0035] It should be noted that in the present application, compared with the winding flat area part 102 of the pole group, the active material, the conductive agent and the binder of the positive electrode sheet and the negative electrode sheet in the winding corner area part 101 of the pole group are different, and the porosity and the functional coating of the separator are also different.

[0036] Among them, the separator includes a first area part and a second area part, that is, the winding corner area part and the winding flat area part of the separator;

[0037] The first area part of the separator is in the winding corner area part 101 of the pole group, and the second area part of the separator is in the winding flat area part 102 of the pole group.

[0038] It should be noted that the first area part and the second area part of the separator are different in structure or type; the first area part of the separator has one or more properties such as good liquid retention, low impedance and slowing down the expansion of the electrode sheet.

[0039] It should be noted that in Figure 1 , the negative electrode sheet 1002 is a thin solid line in the figure, the positive electrode sheet 1001 is a thick solid line in the figure, and the separator 1003 is a dashed line.

[0040] In the present application, specifically, the first area part of the separator includes any one of the following: a base film (i.e. a pure base film), a base film with an insulating layer on one side surface, a base film with insulating layers on both upper and lower side surfaces, a base film with a bonding layer on one side surface, a base film with bonding layers on both upper and lower side surfaces, and a base film with an insulating layer and a bonding layer on one side and an insulating layer on the other side.

[0041] The second area part of the separator includes any one of the following: a base film (i.e. a pure base film), a base film with an insulating layer on one side surface, a base film with insulating layers on both upper and lower side surfaces, a base film with a bonding layer on one side surface, a base film with bonding layers on both upper and lower side surfaces, and a base film with an insulating layer and a bonding layer on one side and an insulating layer on the other side, and a base film with an insulating layer and a bonding layer on both upper and lower sides.

[0042] Among them, the bonding layer of the separator only contains (i.e. only contains) a component of the binder;

[0043] The binder of the diaphragm can be any one of water-soluble binder, solvent type binder and emulsion type binder, for example, specifically including polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, polyacrylate, sodium polyacrylate and styrene butadiene rubber.

[0044] The material of the base film includes any one of polyethylene, polypropylene and polyimide, but is not limited to polyethylene, polypropylene and polyimide;

[0045] The insulating layer includes insulating components, binder and dispersant, but is not limited to insulating components, binder and dispersant; wherein the insulating components include at least one of hydrated aluminum oxide and hydrated boehmite; the binder includes any one of water-soluble binder, solvent type binder and emulsion type binder, for example, including polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, polyacrylate, sodium polyacrylate and styrene butadiene rubber. The dispersant is used to promote uniform dispersion of the slurry, and specifically includes any one of polyoxyethylene diester, polytetraethylene glycol monostearate, polyvinylpyrrolidone, polyethylene oxide and methyl cellulose.

[0046] In the present application, specifically, in the insulating layer of the diaphragm, the mass percentage of the insulating components is 78.0% to 94.9%, the mass percentage of the binder is 5% to 20%, and the mass percentage of the dispersant is 0.1% to 1%.

[0047] In the present application, specifically, the first area part of the diaphragm uses a high porosity (for example, porosity greater than 35% or more) or super high porosity (for example, porosity greater than 45% or more) diaphragm, and the porosity of the second area part of the diaphragm is lower than that of the first area part. This case only involves the problem of porosity when the first area part and the second area part of the diaphragm are both simple base films.

[0048] In the present application, specifically, the positive electrode sheet includes a first area part and a second area part, i.e., the winding corner area part and the winding flat area part of the positive electrode sheet;

[0049] The first area part of the positive electrode sheet is in the winding corner area part 101 of the winding type battery pole group, and the second area part is in the winding flat area part 102 of the winding type battery pole group;

[0050] The content of the conductive agent in the first area part of the positive electrode sheet is higher than that in the second area part of the positive electrode sheet;

[0051] The particle size of the positive electrode active material particles in the first area part of the positive electrode sheet is smaller than that in the second area part of the positive electrode sheet;

[0052] It should be noted that the first area part of the positive electrode sheet is different from the second area part in composition. The first area part of the positive electrode sheet has a high content of conductive agent, small active particle size, and low binder impedance, and has a preset shape of concave-convex mark structure disposed thereon.

[0053] The first area part of the positive electrode sheet has a preset shape of concave-convex mark structure disposed thereon;

[0054] The first area part of the positive electrode sheet includes a positive electrode current collector (such as an aluminum foil) and a positive electrode active material layer, and in the positive electrode active material layer, the conductive agent accounts for 1-4% (preferably 1-2%) by mass, the positive electrode active material particles account for 92-98% by mass, and the binder accounts for 1-4% by mass.

[0055] It should be noted that the first area part of the positive electrode sheet contains positive electrode active material particles, conductive agent, and binder; wherein the positive electrode active material particles include any one of lithium iron phosphate particles, ternary positive electrode particles, lithium cobaltate particles, and lithium manganate particles, and the mass fraction is 92-98%; the conductive agent includes at least one of carbon nanotubes, carbon black, and graphene, and the mass fraction is 1-4%; and the binder specifically includes any one of polyvinylidene fluoride, polyvinylidene fluoride and polyhexafluoropropylene copolymer poly (vinylidene fluoride-hexafluoropropylene), and poly (acrylonitrile-sodium acrylate), and the mass fraction is 1-4%.

[0056] The second area part of the positive electrode sheet has no concave-convex mark structure;

[0057] The second area part of the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and in the positive electrode active material layer, the conductive agent accounts for 0.3-2% (preferably 0.5-1%) by mass, the positive electrode active material particles account for 94-98.7% by mass, and the binder accounts for 1-4% by mass.

[0058] It should be noted that the second area part of the positive electrode sheet contains positive electrode active material particles, conductive agent, and binder; wherein the positive electrode active material particles include any one of lithium iron phosphate particles, ternary positive electrode material, lithium cobaltate particles, and lithium manganate particles, and the mass fraction is 94-98.7%; the conductive agent specifically includes at least one of carbon nanotubes, carbon black, and graphene, and the mass fraction is 0.3-2% (preferably 0.5-1%); and the binder specifically includes any one of polyvinylidene fluoride, polyvinylidene fluoride and polyhexafluoropropylene copolymer poly (vinylidene fluoride-hexafluoropropylene), and poly (acrylonitrile-sodium acrylate), and the mass fraction is 1-4%.

[0059] In the present application, in particular, for the positive electrode sheet, the positive electrode current collector has any one of an aluminum foil, a carbon-coated aluminum foil, and a composite aluminum foil. The three kinds of aluminum foils are all conventional copper foils, which will not be described here.

[0060] In the present application, in particular, the concave-convex mark structure of the preset shape includes, but is not limited to, a rhombic grid, a dot, and a net structure, and all non-flat structures.

[0061] It should be noted that the second area part of the positive electrode sheet has a low content of the conductive agent, a large particle size of the active particles, a high impedance of the binder, and a flat electrode sheet without the concave-convex mark structure.

[0062] In particular, in the first area part of the positive electrode sheet, the median particle size D50 of the positive electrode active material particles is 0.5-1.3 μm, and preferably 0.8-1.1 μm.

[0063] In the second area part of the positive electrode sheet, the median particle size D50 of the positive electrode active material particles is 0.8-3.0 μm, and preferably 1.1-1.5 μm.

[0064] In particular, in the first area part of the positive electrode sheet, the binder has a low impedance, and the binder includes polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0065] In the second area part of the positive electrode sheet, the binder has a high impedance, and the binder includes any one of polyvinylidene fluoride, polyvinylidene fluoride and polyhexafluoropropylene copolymer poly(vinylidene fluoride-hexafluoropropylene), and poly(acrylonitrile-sodium acrylate).

[0066] In the present application, in particular, the negative electrode sheet includes a first area part and a second area part, i.e., a winding corner area part and a winding flat area part of the negative electrode sheet.

[0067] The first area part of the negative electrode sheet is in the winding corner area part 101 of the winding type battery pole group, and the second area part is in the winding flat area part 102 of the winding type battery pole group.

[0068] The content of the conductive agent in the first area part of the negative electrode sheet is higher than that in the second area part of the negative electrode sheet.

[0069] The particle size of the negative electrode active material particles in the first area part of the negative electrode sheet is smaller than that in the second area part of the negative electrode sheet.

[0070] The first area part of the negative electrode sheet includes a negative electrode current collector (for example, a copper foil) and a negative electrode active material layer, and in the negative electrode active material layer, a conductive agent with a mass percentage of 1-2% (preferably 1-1.2%), negative electrode active material particles with a mass percentage of 94-97%, and a binder with a mass percentage of 2-4% are included.

[0071] It should be noted that the first area part of the negative electrode sheet contains negative electrode active material particles, a conductive agent, and a binder; the negative electrode active material particles include at least one of natural graphite particles, artificial graphite particles, silicon-oxygen particles, and lithium titanate particles, and the mass fraction of the negative electrode active material particles is 94-97%; the conductive agent specifically includes at least one of carbon nanotubes, carbon black, and graphene, and the mass percentage of the conductive agent is 1-2% (preferably 1-1.2%); and the binder specifically includes at least one of styrene-butadiene rubber, styrene-acrylate, carboxymethyl cellulose, and acrylic multi-component copolymer, and the mass percentage of the binder is 2-4%.

[0072] The second area part of the negative electrode sheet includes a negative electrode current collector (a copper foil) and a negative electrode active material layer, and in the negative electrode active material layer, a conductive agent with a mass percentage of 0.3-1.2% (preferably 0.5-0.7%), negative electrode active material particles with a mass percentage of 94.8-97.7%, and a binder with a mass percentage of 2-4% are included.

[0073] It should be noted that the second area part of the negative electrode sheet contains negative electrode active material particles, a conductive agent, and a binder; the negative electrode active material particles include at least one of natural graphite particles, artificial graphite particles, silicon-oxygen particles, and lithium titanate particles, and the mass fraction of the negative electrode active material particles is 94.8-97.7%; the conductive agent specifically includes at least one of carbon nanotubes, carbon black, and graphene, and the mass percentage of the conductive agent is 0.3-1.2% (preferably 0.5-0.7%); and the binder specifically includes at least one of styrene-butadiene rubber, styrene-acrylate, carboxymethyl cellulose, and acrylic multi-component copolymer, and the mass percentage of the binder is 2-4%.

[0074] In the present application, specifically, for the negative electrode sheet, the negative electrode current collector can be selected from any one of a copper foil, a carbon-coated copper foil, and a composite copper foil. The three kinds of copper foils are all conventional copper foils, and will not be described here.

[0075] In the first area part of the negative electrode sheet and the second area part of the negative electrode sheet, the negative electrode active material particles include at least one of graphite particles, silicon-oxygen particles, and lithium titanate particles.

[0076] It should be noted that the first area part of the negative plate is different from the second area part in composition. The first area part of the negative plate has high content of conductive agent, small particle size of active particles, low graphitization degree, and low impedance of binder. The second area part of the negative plate has low content of conductive agent, large particle size of active particles, high graphitization degree, and high impedance of binder.

[0077] In the first area part of the negative plate, the median particle size D50 of the negative active material particles is 11-15 μm, preferably 12-13 μm.

[0078] In the second area part of the negative plate, the median particle size D50 of the negative active material particles is 14-20 μm, preferably 15-17 μm.

[0079] In the present application, the graphitization degree of the negative active material particles in the first area part of the negative plate is lower than the content of conductive agent in the second area part of the negative plate.

[0080] The impedance of the binder in the first area part of the negative plate is lower than the impedance of the binder in the second area part of the negative plate.

[0081] In the first area part of the negative plate, the graphitization degree of the negative active material particles is low, and the graphitization degree of the negative active material particles is 91-94%, preferably 92-93%.

[0082] In the second area part of the negative plate, the graphitization degree of the negative active material particles is high, and the graphitization degree of the negative active material particles is 93-96%, preferably 94-95%.

[0083] In the first area part of the negative plate, the impedance of the binder is low, and the binder includes at least one of styrene-butadiene latex, styrene-acrylate, carboxymethyl cellulose, and acrylic multi-copolymer.

[0084] In the second area part of the negative plate, the impedance of the binder is high, and the binder includes at least one of styrene-butadiene latex, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polynicotinamide imine, carboxymethyl cellulose, and acrylic multi-copolymer.

[0085] Compared with the prior art, the winding type battery pole group provided by the present application has the following beneficial effects:

[0086] 1. The outer shape structure of the winding type battery pole group of the present application is beneficial to improve the space utilization and reduce the compaction and surface density design of the pole piece.

[0087] 2. The lithium precipitation problem at the corner of the existing winding type battery pole group is improved, and the cycle performance is improved.

[0088] It should be noted that the present application improves the lithium precipitation by changing the structure or material of the diaphragm, the positive electrode and the negative electrode, increasing the liquid retention of the corner, reducing the impedance and accelerating the ion transmission.

[0089] 3. The ion transmission rate is increased, the active metal deposition caused by the expansion and deintercalation of the pole piece is reduced, the active metal precipitation and capacity loss of the pole piece are avoided, thereby improving the performance of the battery cell. For example, the present application increases the type or content of the conductive agent at the corner, reduces the impedance, increases the ion transmission capacity, can ensure that the corner avoids active metal deposition during the charging and discharging process, thereby avoiding the lithium precipitation problem.

[0090] 4. The winding type battery pole group of the present application can provide space for the charging and discharging expansion of the pole piece, and reduce the deformation of the pole group. It should be noted that the positive pole piece of the present application can adopt a "embossing" design, and the positive pole piece has a concave-convex form on the surface, which reserves space for the pole piece expansion during the later charging and discharging process, reduces the deformation of the pole group, and improves the lithium precipitation problem.

[0091] 5. It can be designed as needed to save the cost of the battery cell.

[0092] Based on the winding type battery pole group provided by the present application, as shown in Figure 2 、 Figure 3 The present application also discloses a lithium ion battery comprising the winding type battery pole group described above.

[0093] The winding type battery pole group 100 is located in the inner cavity of the hollow and top-open square battery aluminum shell 1.

[0094] The top of the square battery aluminum shell 1 is sealingly provided with a battery cover plate 4.

[0095] The square battery aluminum shell 1 is injected with electrolyte 3.

[0096] It should be noted that the square battery aluminum shell 1 and the battery cover plate 4 connected to the top end of the square battery aluminum shell 1 are laser welded to form a sealed cavity. The sealed cavity contains the winding type battery pole group 100, the electrolyte 3, the positive electrode lug of the winding type battery pole group, the positive electrode adapter piece 5, the negative electrode lug of the winding type battery pole group, the negative electrode adapter piece 6, the pole group protection sleeve 7 and the lower gasket 8. The sealed cavity contains the outer gasket 9 and the outer insulation film 10. The winding type battery pole group 100 has a pole group packing tape 2;

[0097] In the present application, specifically, the positive electrode lug of the winding type battery pole group 100 is connected to the bottom end of the positive electrode pole 401 vertically penetrating the battery cover plate 4 through the positive electrode adapter piece 5;

[0098] The negative tab of the winding type battery pole group 100 is connected with the bottom end of the negative pole post 402 vertically and penetratingly arranged on the battery cover plate 4 through the negative adapter piece 6;

[0099] In the present application, the winding type battery pole group 100 is arranged between the inner side of the square type battery aluminum shell 1 and the pole group protection sleeve 7;

[0100] The pole group protection sleeve 7 is wrapped on the outer surface of the winding type battery pole group 100, and is used for insulating and isolating the winding type battery pole group 100 from the square type battery aluminum shell 1.

[0101] In the present application, the bottom inner side of the square type battery aluminum shell 1 is arranged with the lower gasket 8;

[0102] The top of the square type battery aluminum shell 1 is arranged with the insulating outer gasket 9;

[0103] The outer surface of the square type battery aluminum shell 1 is wrapped with the outer wrapping insulation film 10.

[0104] In the present application, the battery cover plate 4 is arranged with the shell protruding part 11 protruding upward between the positive pole post 401 and the negative pole post 402, and the shape of the shell protruding part 11 is isosceles trapezoidal. It should be noted that the top of the existing battery shell is a flat top.

[0105] Compared with the prior art, the lithium ion battery provided by the present application has the following beneficial effects:

[0106] 1. The internal space of the battery is increased, the pole group shell ratio of the battery is ensured unchanged, the pole piece compaction density is reduced, the pole piece porosity is increased, and the pole piece liquid retention property is increased.

[0107] It should be noted that in the present application, the height of the battery is the height from the pole post to the bottom of the battery shell, and the pole post serves as the lower limit point of the battery pack (i.e. the assembled battery), so the position between the two pole posts is empty. The aluminum shell of the present application fully utilizes the space between the two pole posts to increase the space inside the battery shell. If other designs remain unchanged, the extra space (i.e. the shell protruding part 11) can be used to increase the storage of electrolyte. In this way, under the same capacity, the area of the pole piece can be increased, the coating amount and the compaction density are reduced accordingly, the porosity of the pole piece is increased, the electrolyte injection amount is increased, the liquid retention capacity is improved, and the liquid retention property is increased.

[0108] 2. The compaction density of the pole piece is reduced, the types of optional materials are increased, the binary of the battery is increased, the cost is saved, the mechanical processing difficulty index is reduced, the production process difficulty is reduced, and the product direct pass rate and the good product rate are increased.

[0109] 3. If the structure of the pole group in the battery is kept unchanged, the pole group shell ratio of the battery body (i.e. the ratio between the volume of the pole group of the battery and the volume of the shell of the battery) is reduced, more space is provided for the electrolyte, the injection amount of the electrolyte of the battery cell is increased, more power is provided for the later stage of the cycle, and thus the performance of the battery cell is improved.

[0110] 4. The space in the shell of the battery is increased, the net liquid amount and the liquid retaining capacity of the battery cell are increased, the materials that can be used are increased, the cost is saved, the best use range of the materials is ensured, and the performance of the battery is improved.

[0111] In order to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described below through specific examples.

[0112] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0113] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0114] Comparative example.

[0115] The preparation method of the existing wound type battery pole group and the wound type lithium ion battery is specifically described as follows:

[0116] I. Preparation of positive electrode sheet, according to the weight ratio (parts) :

[0117] 1. Slurry preparation: 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, N-methyl pyrrolidone (NMP) is used as the solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 57.0%, and then the material is discharged.

[0118] 2. Coating: the positive electrode slurry prepared in the above step is coated on the carbon-coated aluminum foil current collector. The specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon-coated layer on the upper and lower sides of the aluminum foil is 1 μm each, and the double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0119] 3. Rolling: the thickness of the positive electrode sheet after rolling is 181 μm at room temperature.

[0120] 4. Laser cutting: the positive electrode sheet is cut into the required size of the pole sheet for the battery using the existing laser cutting equipment.

[0121] II. Preparation of negative electrode sheet, according to the weight ratio (parts) :

[0122] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with effective solid content of 1.5%, and 5 parts of butadiene-styrene rubber (SBR) binder glue with effective solid content of 40% are mixed uniformly in a slurry tank, deionized water is used as the solvent, the solid content of the slurry in the slurry tank is adjusted to 48.0%, and then the slurry is discharged;

[0123] 2. Coating: the negative electrode slurry prepared in the above step is coated on a double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 ;

[0124] 3. Rolling: after rolling, the thickness of the positive electrode sheet is 119 μm at room temperature;

[0125] 4. Laser cutting: the negative electrode sheet is cut into the required size of the electrode sheet for the battery using existing laser cutting equipment.

[0126] III. Preparation of a wound-type battery electrode group

[0127] 1. Winding: the positive electrode sheet prepared in the above step, the negative electrode sheet, and the separator (the separator used in the existing wound-type battery electrode group is a base film) are wound and assembled into an electrode group.

[0128] 2. Hot pressing: the electrode group is subjected to hot pressing, and the hot pressing conditions are: temperature 90°C, pressure 4 t, and time 60 s.

[0129] IV. Battery preparation

[0130] 1. Assembly: the wound electrode group, a jumper, a battery cover, etc. are welded, a protective sleeve for the electrode group is coated, and assembly is performed.

[0131] 2. Perimeter welding of the shell: the assembly and a gasket are placed in a battery shell, the battery cover and the battery shell are perimetrically welded, and a semi-finished battery is prepared.

[0132] 3. Drying: the semi-finished battery is placed in an oven, and dried at a temperature of 90°C and a pressure of -80 kPa for 24 h.

[0133] 4. Liquid injection: electrolyte is injected into the semi-finished battery.

[0134] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0135] 6. Liquid supplementing and sealing: the semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0136] 7. Capacity grading: the battery after sealing is subjected to capacity grading.

[0137] 8. Aging, and finally a wound-type lithium ion battery is obtained.

[0138] Example 1.

[0139] The present application provides a winding type battery pole group and a preparation method of winding type lithium ion battery, which improves the lithium precipitation problem at the corner of winding type battery through the improvement of the separator, and the specific description is as follows:

[0140] I. Preparation of positive electrode sheet, according to the weight ratio (parts) :

[0141] 1. Slurry preparation: 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry tank is adjusted to 57.0%, and then the material is discharged.

[0142] 2. Coating: the positive electrode slurry prepared in the above step is coated on the carbon-coated aluminum foil current collector. The specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon-coated layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0143] 3. Rolling: the thickness of the positive electrode sheet after rolling is 181 μm at room temperature.

[0144] 3. Laser cutting: the positive electrode sheet is cut into the required size of the electrode sheet for the battery by using the existing laser cutting equipment.

[0145] II. Preparation of negative electrode sheet, according to the weight ratio (parts) :

[0146] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with effective solid content of 1.5% and 5 parts of styrene-butadiene rubber (SBR) binder glue with effective solid content of 40% are uniformly mixed in a slurry tank, the solvent is deionized water, the solid content of the slurry in the slurry tank is adjusted to 48.0%, and then the material is discharged.

[0147] 2. Coating: the negative electrode slurry prepared in the above step is coated on the double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0148] 3. Rolling: the thickness of the negative electrode sheet after rolling is 119 μm at room temperature.

[0149] 3. Laser cutting: the negative electrode sheet is cut into the required size of the electrode sheet for the battery by using the existing laser cutting equipment.

[0150] III. Preparation of winding type battery pole group

[0151] 1. Diaphragm: The diaphragm comprises a first area portion and a second area portion. The first area portion is in the winding corner area portion, and the second area is in the winding flat area portion. The first area portion and the second area portion of the diaphragm are different in structure or type. The first area portion of the diaphragm adopts a base film + boehmite layer (i.e. a base film coated with an insulating layer, the insulating component in the insulating layer is a boehmite layer, the dispersant in the insulating layer is polyvinylpyrrolidone, and the binder is polyvinylidene fluoride), and the second area portion of the diaphragm adopts a base film.

[0152] 2. Winding: winding the positive electrode sheet and the negative electrode sheet prepared in the above step, and the diaphragm to form a pole group.

[0153] 3. Hot pressing: hot pressing the pole group, and the hot pressing conditions are: temperature 90℃, pressure 4t, and time 60S.

[0154] Four, battery preparation

[0155] 1. Assembly: welding the winding type battery pole group and the adapter piece, the battery cover, etc. using the above, and coating the pole group protective sleeve to perform assembly.

[0156] 2. Shell periphery welding: placing the above assembly and the gasket into the battery shell, and peripherally welding the battery cover and the battery shell to form a semi-finished battery.

[0157] 3. Drying: placing the above semi-finished battery into an oven, and drying for 24h under the conditions of temperature 90℃ and pressure -80kPa.

[0158] 4. Liquid injection: injecting electrolyte into the above semi-finished battery.

[0159] 5. Formation: charging and forming the semi-finished battery after liquid injection.

[0160] 6. Liquid supplementing and sealing: standing the semi-finished battery after formation, supplementing liquid, and sealing.

[0161] 7. Capacity distribution: distributing the capacity of the battery after sealing.

[0162] 8. Aging, and finally obtaining a winding type lithium ion battery.

[0163] Example 2.

[0164] The winding type battery pole group and the preparation method of the winding type lithium ion battery provided by the application improve the lithium precipitation problem at the corner of the winding type battery through the improvement of the diaphragm, and the specific description is as follows:

[0165] I. Positive electrode sheet preparation, according to the weight ratio (parts):

[0166] 1. Slurry preparation: 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are mixed uniformly in a slurry tank. The solvent is N-methyl pyrrolidone (NMP). The solid content of the slurry in the slurry tank is adjusted to 57.0%, and then the slurry is discharged.

[0167] 2. Coating: The positive electrode slurry prepared in the above step is coated on a carbon-coated aluminum foil current collector. The specification of the carbon-coated aluminum foil is (13+1+1) μm, with the thickness of the aluminum foil being 13 μm and the thickness of the carbon-coated layer on both sides of the aluminum foil being 1 μm each. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0168] 3. Rolling: The thickness of the positive electrode sheet after rolling is 181 μm at room temperature.

[0169] 3. Laser cutting: The positive electrode sheet is cut into the required size of the electrode sheet for the battery using existing laser cutting equipment.

[0170] II. Preparation of negative electrode sheet, by weight ratio (parts):

[0171] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder solution with an effective solid content of 1.5%, and 5 parts of styrene-butadiene rubber (SBR) binder solution with an effective solid content of 40% are mixed uniformly in a slurry tank. The solvent is deionized water. The solid content of the slurry in the slurry tank is adjusted to 48.0%, and then the slurry is discharged.

[0172] 2. Coating: The negative electrode slurry prepared in the above step is coated on a double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0173] 3. Rolling: The thickness of the negative electrode sheet after rolling is 119 μm at room temperature.

[0174] 3. Laser cutting: The negative electrode sheet is cut into the required size of the electrode sheet for the battery using existing laser cutting equipment.

[0175] III. Preparation of wound-type battery electrode group

[0176] 1. Separator: The separator includes a first region portion and a second region portion. The first region portion is in the winding corner region portion, and the second region portion is in the winding flat region portion. The first region portion and the second region portion are different in structure or type. The first region portion of the separator uses a base film coated with an adhesive layer (the adhesive layer uses polyvinylidene fluoride material), and the second region portion of the separator uses a base film.

[0177] 2. Winding: The positive electrode sheet and the negative electrode sheet prepared in the above step, and the separator, are wound and assembled into an electrode group.

[0178] 3. Hot pressing: the above polar group is hot pressed, and the hot pressing conditions are: temperature 90℃, pressure 4t, and time 60s.

[0179] Four, battery preparation

[0180] 1. Assembly: the above winding type battery polar group is welded with the adapter piece, the battery cover, etc., the polar group protective sleeve is covered, and assembly is performed.

[0181] 2. Shell entry periphery welding: the above assembly and the bottom gasket are placed in the battery shell, the battery cover and the battery shell are peripherally welded, and a semi-finished battery is prepared.

[0182] 3. Drying: the above semi-finished battery is placed in an oven, and dried at a temperature of 90℃ and a pressure of -80kPa for 24h.

[0183] 4. Liquid injection: electrolyte is injected into the above semi-finished battery.

[0184] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0185] 6. Liquid supplementing and sealing: the semi-finished battery after formation is left to stand, liquid is supplemented, and sealed.

[0186] 7. Capacity distribution: the sealed battery is subjected to capacity distribution.

[0187] 8. Aging, and finally a winding type lithium ion battery is obtained.

[0188] Example 3.

[0189] The winding type battery polar group and the preparation method of the winding type lithium ion battery provided by the application improve the lithium precipitation problem at the corner of the winding type battery through improvement of the separator, and specific explanations are as follows:

[0190] I. Positive sheet preparation, according to the weight ratio (parts):

[0191] 1. Slurry preparation: 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, N-methyl pyrrolidone (NMP) is used as the solvent, the slurry solid content in the slurry preparation cylinder is adjusted to 57.0%, and then the material is discharged.

[0192] 2. Coating: the positive electrode slurry prepared in the above step is coated on a carbon-coated aluminum foil current collector. The specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon-coated layer on the upper and lower sides of the aluminum foil is 1 μm each. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0193] 3. Rolling: the thickness of the positive electrode sheet after rolling is 181 μm at room temperature.

[0194] 3. Laser cutting: the positive electrode sheet is cut into the size required by the battery using existing laser cutting equipment.

[0195] II. Preparation of the negative electrode sheet, according to the weight ratio (parts):

[0196] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with an effective solid content of 1.5%, and 5 parts of butadiene-styrene rubber (SBR) binder glue with an effective solid content of 40% are mixed uniformly in a slurry preparation tank, deionized water is used as the solvent, the solid content of the slurry in the slurry cylinder is adjusted to 48.0%, and then the slurry is discharged.

[0197] 2. Coating: the negative electrode slurry prepared in the above step is coated on a double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0198] 3. Rolling: the thickness of the negative electrode sheet after rolling is 119 μm at room temperature.

[0199] 3. Laser cutting: the negative electrode sheet is cut into the size required by the battery using existing laser cutting equipment.

[0200] III. Preparation of the wound battery electrode group

[0201] 1. The separator comprises a first area portion and a second area portion. The first area portion is in the winding corner area portion, and the second area portion is in the winding flat area portion. The first area portion and the second area portion are different in structure or type. The first area portion of the separator uses a base film with a porosity of 48%, and the second area portion of the separator uses a base film with a porosity of 38%.

[0202] 2. Winding: the positive electrode sheet and the negative electrode sheet prepared in the above step, and the separator are wound and assembled into an electrode group.

[0203] 3. Hot pressing: the electrode group is hot pressed, and the hot pressing conditions are: temperature 90°C, pressure 4t, and time 60s.

[0204] IV. Battery preparation

[0205] 1. Assembly: the wound battery electrode group is welded with a connecting piece, a battery cover, etc., a protective sleeve is wrapped around the electrode group, and assembly is performed.

[0206] 2. Perimeter welding into the shell: the assembly and a gasket are placed into a battery shell, the battery cover and the battery shell are perimetrically welded, and a semi-finished battery is prepared.

[0207] 3. Drying: the above-mentioned semi-finished battery is put into an oven, and dried at a temperature of 90℃ and a pressure of -80kPa for 24h.

[0208] 4. Liquid injection: electrolyte is injected into the above-mentioned semi-finished battery.

[0209] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0210] 6. Standing, liquid supplementing and sealing: the semi-finished battery after formation is allowed to stand, supplemented with liquid, and sealed.

[0211] 7. Capacity grading: the sealed battery is subjected to capacity grading.

[0212] 8. Aging, and finally obtaining a wound lithium ion battery.

[0213] Example 4.

[0214] The wound battery pole group and the preparation method of the wound lithium ion battery provided by the present application improve the lithium precipitation problem at the corner of the wound battery through improvement of the positive electrode sheet, and the specific description is as follows:

[0215] I. Preparation of the positive electrode sheet, according to the weight ratio (parts):

[0216] 1. Slurry preparation: positive electrode slurry 1: 91 parts of lithium iron phosphate positive electrode A powder, 5 parts of lithium iron phosphate positive electrode B powder, 2 parts of conductive carbon black powder, and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry cylinder is adjusted to 57.0%, and then the material is discharged;

[0217] Positive electrode slurry 2: 96 parts of lithium iron phosphate positive electrode A powder, 2 parts of conductive carbon black powder, and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry cylinder is adjusted to 57.0%, and then the material is discharged;

[0218] Among them, the lithium iron phosphate positive electrode A powder is a lithium iron phosphate particle with a particle size D50 of 1.2-1.5μm, and the lithium iron phosphate positive electrode B powder is a lithium iron phosphate particle with a particle size D50 of 0.8-1.0μm.

[0219] 2. Coating: The positive electrode sheet comprises a first area portion and a second area portion. The first area portion is at the winding corner area portion, and the second area portion is at the winding flat area portion. Coating is performed according to the coating process, and the positive electrode slurry prepared in the above step is coated on the carbon-coated aluminum foil current collector. The positive electrode slurry 1 is coated at the position of the first area portion of the electrode sheet, and the positive electrode slurry 2 is coated at the position of the second area portion of the electrode sheet. The specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon-coated layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0220] 3. Rolling: After rolling, the thickness of the positive electrode sheet is 181 μm at room temperature.

[0221] 4. Laser cutting: The positive electrode sheet is cut into the size required by the battery using the existing laser cutting equipment.

[0222] II. Preparation of negative electrode sheet, according to the weight ratio (parts):

[0223] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, and 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with an effective solid content of 1.5% and 5 parts of styrene-butadiene rubber (SBR) binder glue with an effective solid content of 40% are uniformly mixed in a slurry preparation tank, deionized water is used as the solvent, the solid content of the slurry in the slurry cylinder is adjusted to 48.0%, and then the slurry is discharged.

[0224] 2. Coating: The negative electrode slurry prepared in the above step is coated on the double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0225] 3. Rolling: After rolling, the thickness of the negative electrode sheet is 119 μm at room temperature.

[0226] 4. Laser cutting: The negative electrode sheet is cut into the size required by the battery using the existing laser cutting equipment.

[0227] III. Preparation of wound battery electrode group

[0228] 1. Winding: The positive electrode sheet prepared in the above step and the negative electrode sheet, and the separator are wound and assembled into an electrode group.

[0229] 2. Hot pressing: The above electrode group is hot pressed, and the hot pressing conditions are: temperature 90°C, pressure 4t, and time 60s.

[0230] IV. Battery preparation

[0231] 1. Assembly: The wound battery electrode group, adapter piece, battery cover, etc. are welded, and the electrode group protective sleeve is coated for assembly.

[0232] 2. Shell entry peripheral welding: the above assembly and the bottom gasket are put into the battery shell, the battery cover is peripherally welded with the battery shell, and a semi-finished battery is prepared.

[0233] 3. Drying: the above semi-finished battery is put into an oven, dried at a temperature of 90℃ and a pressure of-80kPa for 24h.

[0234] 4. Liquid injection: electrolyte is injected into the above semi-finished battery.

[0235] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0236] 6. Liquid supplementing and sealing: the semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0237] 7. Capacity grading: the sealed battery is graded.

[0238] 8. Aging, and finally obtaining a wound lithium ion battery.

[0239] Example 5.

[0240] The wound battery pole group and the preparation method of the wound lithium ion battery provided by the application improve the lithium precipitation problem at the corner of the wound battery through improvement of the positive electrode sheet, and the specific description is as follows:

[0241] I. Preparation of the positive electrode sheet, according to the weight ratio (parts):

[0242] 1. Slurry preparation: positive electrode slurry 1: 96 parts of lithium iron phosphate positive electrode powder, 1 part of conductive carbon black powder, 25 parts of effective solid content 4% carbon nanotube and graphene composite conductive agent, and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry cylinder is adjusted to 57.0%, and then the material is discharged;

[0243] Positive electrode slurry 2: 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder, and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry cylinder is adjusted to 57.0%, and then the material is discharged;

[0244] 2. Coating: The positive electrode sheet comprises a first area portion and a second area portion. The first area portion is at the winding corner area portion, and the second area portion is at the winding flat area portion. Coating is performed according to a coating process. The positive electrode slurry prepared in the above step is coated on the carbon-coated aluminum foil current collector. The positive electrode slurry 1 is coated at the position of the first area portion of the electrode sheet, and the positive electrode slurry 2 is coated at the position of the second area portion of the electrode sheet. The specification of the carbon-coated aluminum foil is (13+1+1) μm. The thickness of the aluminum foil is 13 μm, and the thickness of the carbon coating on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0245] 3. Rolling: The thickness of the positive electrode sheet after rolling is 181 μm at room temperature.

[0246] 4. Laser cutting: The positive electrode sheet is cut into the size required by the battery using the existing laser cutting equipment.

[0247] II. Preparation of the negative electrode sheet, according to the weight ratio (parts):

[0248] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethylcellulose sodium (CMC) binder glue solution with an effective solid content of 1.5%, and 5 parts of butadiene-styrene rubber (SBR) binder glue solution with an effective solid content of 40% are uniformly mixed in a slurry preparation tank. Deionized water is used as the solvent. The solid content of the slurry in the slurry cylinder is adjusted to 48.0%, and then the slurry is discharged.

[0249] 2. Coating: The negative electrode slurry prepared in the above step is coated on the double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0250] 3. Rolling: The thickness of the negative electrode sheet after rolling is 119 μm at room temperature.

[0251] 4. Laser cutting: The negative electrode sheet is cut into the size required by the battery using the existing laser cutting equipment.

[0252] III. Preparation of the wound battery electrode group

[0253] 1. Winding: The positive electrode sheet prepared in the above step and the negative electrode sheet, and the separator are wound and assembled into an electrode group.

[0254] 2. Hot pressing: The electrode group is hot pressed. The hot pressing conditions are: temperature 90°C, pressure 4t, and time 60s.

[0255] IV. Battery preparation

[0256] 1. Assembly: The wound battery electrode group is welded with the adapter piece, the battery cover, etc., and the electrode group protective sleeve is coated, and then assembled.

[0257] 2. Shell entry peripheral welding: the above assembly and the bottom gasket are put into the battery shell, and the battery cover is peripherally welded with the battery shell to make a semi-finished battery.

[0258] 3. Drying: the above semi-finished battery is put into an oven and dried at a temperature of 90℃ and a pressure of -80kPa for 24h.

[0259] 4. Liquid injection: electrolyte is injected into the above semi-finished battery.

[0260] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0261] 6. Liquid supplementing and sealing: the semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0262] 7. Capacity grading: the sealed battery is subjected to capacity grading.

[0263] 8. Aging, and finally a wound lithium ion battery is obtained.

[0264] Example 6.

[0265] The wound battery pole group and the preparation method of the wound lithium ion battery provided by the application improve the lithium precipitation problem at the corner of the wound battery through improvement of the positive electrode sheet, and the specific description is as follows:

[0266] I. Preparation of the positive electrode sheet, according to the weight ratio (parts):

[0267] 1. Slurry preparation: positive electrode slurry 1: 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder, and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry tank, N-methyl pyrrolidone (NMP) is used as the solvent, the solid content of the slurry in the slurry cylinder is adjusted to 57.0%, and then the slurry is discharged.

[0268] 2. Coating: the specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon-coated layer on the upper and lower sides of the aluminum foil is 1 μm each. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0269] 3. Rolling: at room temperature, the pole piece is subjected to different area rolling treatment according to the process design parameters. The positive electrode sheet includes a first area part and a second area part. The first area part is embossed by rolling, and the rolling is a diamond grid structure, which ensures that the surface of the pole piece has a concave-convex shape, and the second area part is normally rolled to ensure the flatness of the pole piece, and the thickness is 181 μm. The first area part is in the winding corner area, and the second area part is in the winding straight area.

[0270] 4. Laser cutting: the positive electrode sheet is cut into the required size of the pole piece by using the existing laser cutting equipment.

[0271] II. Preparation of negative electrode sheet, in terms of weight ratio (parts) :

[0272] 1. Pulping: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue solution with effective solid content of 1.5%, and 5 parts of butadiene-styrene rubber (SBR) binder glue solution with effective solid content of 40% are mixed uniformly in a pulping tank, deionized water is used as solvent, the solid content of the slurry in the pulping cylinder is adjusted to 48.0%, and then the material is discharged;

[0273] 2. Coating: the negative electrode slurry prepared in the above step is coated on a double-side copper foil current collector. The specification of the copper foil is 6μm. The double-sided area density of the electrode material is 18.6mg / cm 2 .

[0274] 3. Rolling: after rolling, the thickness of the negative electrode sheet is 119μm at room temperature.

[0275] 4. Laser cutting: the negative electrode sheet is cut into the required size of the electrode sheet for the battery using the existing laser cutting equipment.

[0276] III. Preparation of wound battery electrode group

[0277] 1. Winding: the positive electrode sheet prepared in the above step and the negative electrode sheet, and the separator are wound and assembled into an electrode group.

[0278] 2. Hot pressing: the electrode group is hot pressed, and the hot pressing conditions are: temperature 90℃, pressure 4t, and time 60S.

[0279] IV. Preparation of battery

[0280] 1. Assembly: the wound battery electrode group is welded with a connecting sheet, a battery cover, etc., a protective sleeve is wrapped around the electrode group, and the assembly is performed.

[0281] 2. Perimeter welding of the shell: the assembly and a gasket are placed in a battery shell, the battery cover and the battery shell are perimetrically welded, and a semi-finished battery is prepared.

[0282] 3. Drying: the semi-finished battery is placed in an oven, and dried at a temperature of 90℃ and a pressure of -80kPa for 24h.

[0283] 4. Liquid injection: electrolyte is injected into the semi-finished battery.

[0284] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0285] 6. Liquid supplementing and sealing: the semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0286] 7. Capacity grading: the battery after sealing is subjected to capacity grading.

[0287] 8. aging, to obtain a wound lithium ion battery.

[0288] Example 7.

[0289] The present application provides a preparation method of a wound battery pole group and a wound lithium ion battery. The lithium precipitation problem at the corner of the wound battery is improved by improving the positive pole sheet and the negative pole sheet. The specific description is as follows:

[0290] I. Preparation of the positive pole sheet, according to the weight ratio (parts) :

[0291] 1. Slurry preparation: the positive pole slurry 1: 96 parts of lithium iron phosphate positive pole powder, 2 parts of conductive carbon black powder, 0.5 parts of polyacrylonitrile-sodium acrylate binder and 1.5 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry preparation cylinder is adjusted to 57.0%, and then the material is discharged;

[0292] The positive pole slurry 2: 96 parts of lithium iron phosphate positive pole powder, 2 parts of conductive carbon black powder, and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, the solvent is N-methyl pyrrolidone (NMP), the solid content of the slurry in the slurry preparation cylinder is adjusted to 57.0%, and then the material is discharged;

[0293] 2. Coating: the positive pole sheet includes a first area part and a second area part. The first area part is in the winding corner area, and the second area part is in the winding straight area. According to the coating process, the positive pole slurry prepared in the above step is coated on the carbon-coated aluminum foil current collector. The positive pole slurry 1 is coated on the first area part of the pole sheet, and the positive pole slurry 2 is coated on the second area part of the pole sheet. The specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon-coated layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0294] 3. Rolling: the thickness of the positive pole sheet after rolling is 181 μm at room temperature.

[0295] 3. Laser cutting: the positive pole sheet is cut into the required size of the pole sheet for the battery by using the existing laser cutting equipment.

[0296] II. Preparation of the negative pole sheet, according to the weight ratio (parts) :

[0297] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with effective solid content of 1.5%, and 5 parts of butadiene-styrene rubber (SBR) binder glue with effective solid content of 40% are mixed uniformly in a slurry tank, deionized water is used as the solvent, the solid content of the slurry in the slurry tank is adjusted to 48.0%, and then the slurry is discharged.

[0298] 2. Coating: the negative electrode slurry prepared in the above step is coated on a double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0299] 3. Milling: at room temperature, the electrode sheet is subjected to milling treatment in different regions according to the process design parameters. The negative electrode sheet includes a first region and a second region. The first region is subjected to embossing treatment to ensure that the surface of the electrode sheet has a concave-convex shape, and the second region is subjected to normal milling to ensure the flatness of the electrode sheet, and the thickness is 119 μm. The first region is in the winding corner area, and the second region is in the winding straight area.

[0300] 3. Laser cutting: the negative electrode sheet is cut into the required size of the electrode sheet for the battery using the existing laser cutting equipment.

[0301] Three, preparation of a wound-type battery electrode group

[0302] 1. Winding: the positive electrode sheet prepared in the above step is wound and assembled with the negative electrode sheet and the separator to form an electrode group.

[0303] 2. Hot pressing: the electrode group is subjected to hot pressing, and the hot pressing conditions are: temperature 90°C, pressure 4 t, and time 60 s.

[0304] Four, battery preparation

[0305] 1. Assembly: the wound-type battery electrode group is welded with a connecting piece, a battery cover, etc., a protective sleeve is wrapped around the electrode group, and assembly is performed.

[0306] 2. Perimeter welding of the shell: the assembled product and a gasket are placed in a battery shell, the battery cover and the battery shell are perimetrically welded, and a semi-finished battery is prepared.

[0307] 3. Drying: the semi-finished battery is placed in an oven and dried at a temperature of 90°C and a pressure of -80 kPa for 24 h.

[0308] 4. Liquid injection: electrolyte is injected into the semi-finished battery.

[0309] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0310] 6. Liquid supplementing and sealing: the semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0311] 7. Capacity distribution: distribute the sealed batteries.

[0312] 8. Aging, finally obtaining the wound lithium ion battery.

[0313] Example 8.

[0314] The present application provides a preparation method of a wound battery pole group and a wound lithium ion battery. The lithium precipitation problem at the corner of the wound battery is improved by improving the negative electrode sheet, and the specific description is as follows:

[0315] I. Preparation of positive electrode sheet, according to the weight ratio (parts) :

[0316] 1. Slurry preparation: mix 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) uniformly in a slurry preparation tank, use N-methyl pyrrolidone (NMP) as the solvent, adjust the solid content of the slurry in the slurry preparation cylinder to 57.0%, and then discharge;

[0317] 2. Coating: the specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon coating layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0318] 3. Rolling: at room temperature, the thickness of the rolled positive electrode sheet is 181 μm.

[0319] 4. Laser cutting: use the existing laser cutting equipment to cut the positive electrode sheet into the required size of the pole sheet of the battery.

[0320] II. Preparation of negative electrode sheet, according to the weight ratio (parts) :

[0321] 1. Slurry preparation: mix 58 parts of graphite negative electrode C powder, 38 parts of graphite negative electrode D powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with an effective solid content of 1.5%, and 5 parts of styrene-butadiene rubber (SBR) binder glue with an effective solid content of 40% uniformly in a slurry preparation tank, use deionized water as the solvent, adjust the solid content of the slurry in the slurry preparation cylinder to 48.0%, and then discharge;

[0322] 2. Slurry preparation: mix 96 parts of graphite negative electrode C powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with an effective solid content of 1.5%, and 5 parts of styrene-butadiene rubber (SBR) binder glue with an effective solid content of 40% uniformly in a slurry preparation tank, use deionized water as the solvent, adjust the solid content of the slurry in the slurry preparation cylinder to 48.0%, and then discharge;

[0323] Wherein, the graphite negative electrode C powder is graphite particles with a particle size D50 of 15-17 μm, and the graphite negative electrode D powder is graphite particles with a particle size D50 of 12-13 μm.

[0324] 2. Coating: The pole piece comprises a first area part and a second area part. The first area part is in the winding corner area, and the second area part is in the winding flat area. Coating is performed according to a coating process, and the negative electrode slurry prepared in the above step is coated on the double-side copper foil current collector. The negative electrode slurry 1 is coated on the first area part of the pole piece, and the negative electrode slurry 2 is coated on the second area part of the pole piece. The specification of the copper foil is 6 μm. The double-side area density of the electrode material is 18.6 mg / cm 2 .

[0325] 3. Rolling: After rolling, the thickness of the negative pole piece is 119 μm at room temperature.

[0326] 4. Laser cutting: The negative pole piece is cut into the required size of the pole piece of the battery by using the existing laser cutting equipment.

[0327] Three, preparation of the winding type battery pole group

[0328] 1. Winding: The negative pole piece prepared in the above step is wound and assembled with the positive pole piece and the separator to form a pole group.

[0329] 2. Hot pressing: The pole group is hot pressed, and the hot pressing conditions are as follows: temperature 90 ℃, pressure 4 t, and time 60 s.

[0330] Four, battery preparation

[0331] 1. Assembly: The winding type battery pole group is welded with the adapter piece, the battery cover, and the like, a protective sleeve of the pole group is coated, and assembly is performed.

[0332] 2. Perimeter welding of the shell: The assembly and the gasket are placed in the battery shell, the battery cover and the battery shell are perimetrically welded, and a semi-finished battery is prepared.

[0333] 3. Drying: The semi-finished battery is placed in an oven, and dried at a temperature of 90 ℃ and a pressure of -80 kPa for 24 h.

[0334] 4. Liquid injection: Electrolyte is injected into the semi-finished battery.

[0335] 5. Formation: The semi-finished battery after liquid injection is charged and formed.

[0336] 6. Liquid supplementing and sealing: The semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0337] 7. Capacity grading: The battery after sealing is subjected to capacity grading.

[0338] 8. Aging, and finally a winding type lithium ion battery is obtained.

[0339] Example 9.

[0340] The application provides a winding type battery pole group and a preparation method of the winding type lithium ion battery.

[0341] I. Preparation of the positive pole sheet, according to the weight ratio (parts) :

[0342] 1. Slurry preparation: 96 parts of lithium iron phosphate positive pole powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, N-methyl pyrrolidone (NMP) is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 57.0%, and then the slurry is discharged.

[0343] 2. Coating: the specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon coating layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0344] 3. Rolling: the thickness of the positive pole sheet after rolling is 181 μm at room temperature.

[0345] 4. Laser cutting: the positive pole sheet is cut into the required size of the pole sheet of the battery by using the existing laser cutting equipment.

[0346] II. Preparation of the negative pole sheet, according to the weight ratio (parts) :

[0347] 1. Slurry preparation: 96 parts of graphite negative pole powder, 0.8 parts of conductive carbon black powder, 50 parts of single-walled carbon nanotube powder with an effective solid content of 0.4%, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with an effective solid content of 1.5% and 5 parts of styrene-butadiene rubber (SBR) binder glue with an effective solid content of 40% are uniformly mixed in a slurry preparation tank, deionized water is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 48.0%, and then the slurry is discharged.

[0348] 2. Slurry preparation: 96 parts of lithium iron phosphate negative pole powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue with an effective solid content of 1.5% and 5 parts of styrene-butadiene rubber (SBR) binder glue with an effective solid content of 40% are uniformly mixed in a slurry preparation tank, deionized water is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 48.0%, and then the slurry is discharged.

[0349] 2. Coating: The pole piece comprises a first area part and a second area part. The first area part is in the winding corner area, and the second area part is in the winding flat area. Coating is performed according to the coating process. The negative electrode slurry prepared in the above step is coated on the double-sided copper foil current collector. The negative electrode slurry 1 is coated on the first area part of the pole piece, and the negative electrode slurry 2 is coated on the second area part of the pole piece. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0350] 3. Rolling: After rolling, the thickness of the negative pole piece is 119 μm at room temperature.

[0351] 4. Laser cutting: The negative pole piece is cut into the required size of the pole piece for the battery using the existing laser cutting equipment.

[0352] III. Preparation of the winding type battery pole group

[0353] 1. Winding: The negative pole piece prepared in the above step is wound and assembled with the positive pole piece and the separator to form a pole group.

[0354] 2. Hot pressing: The pole group is hot pressed. The hot pressing conditions are: temperature 90°C, pressure 4t, and time 60s.

[0355] IV. Battery preparation

[0356] 1. Assembly: The pole group is welded with the adapter piece, the battery cover, etc., and the pole group protective sleeve is coated, and then assembled.

[0357] 2. Perimeter welding of the shell: The assembly and the gasket are placed in the battery shell, and the battery cover and the battery shell are perimetrically welded to form a semi-finished battery.

[0358] 3. Drying: The semi-finished battery is placed in an oven and dried at a temperature of 90°C and a pressure of -80 kPa for 24 hours.

[0359] 4. Liquid injection: The electrolyte is injected into the semi-finished battery.

[0360] 5. Formation: The semi-finished battery after liquid injection is charged and formed.

[0361] 6. Liquid supplementing and sealing: The semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0362] 7. Capacity grading: The battery after sealing is capacity graded.

[0363] 8. Aging, to finally obtain a winding type lithium ion battery.

[0364] Example 10.

[0365] The application provides a winding type battery pole group and a preparation method of a winding type lithium ion battery.

[0366] I. Preparation of the positive pole sheet, according to the weight ratio (parts) :

[0367] 1. Slurry preparation: 96 parts of lithium iron phosphate positive pole powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, N-methyl pyrrolidone (NMP) is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 57.0%, and then the slurry is discharged;

[0368] 2. Coating: the specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon coating layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0369] 3. Rolling: the thickness of the positive pole sheet after rolling is 181 μm at room temperature.

[0370] 4. Laser cutting: the positive pole sheet is cut into the required size of the pole sheet of the battery by using the existing laser cutting equipment.

[0371] II. Preparation of the negative pole sheet, according to the weight ratio (parts) :

[0372] 1. Slurry preparation: 96 parts of graphite negative pole powder, 1 part of conductive carbon black powder, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue solution with an effective solid content of 1.5%, 16.6 parts of acrylate binder glue solution with an effective solid content of 6%, and 2.5 parts of styrene-butadiene rubber (SBR) binder glue solution with an effective solid content of 40% are uniformly mixed in a slurry preparation tank, deionized water is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 48.0%, and then the slurry is discharged;

[0373] 2. Slurry preparation: 96 parts of graphite negative pole powder, 0.8 parts of conductive carbon black powder, 50 parts of single-walled carbon nanotube powder with an effective solid content of 0.4%, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue solution with an effective solid content of 1.5%, and 5 parts of styrene-butadiene rubber (SBR) binder glue solution with an effective solid content of 40% are uniformly mixed in a slurry preparation tank, deionized water is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 48.0%, and then the slurry is discharged;

[0374] 2. Coating: The pole piece comprises a first area part and a second area part. The first area part is in the winding corner area, and the second area part is in the winding flat area. Coating is performed according to the coating process. The negative electrode slurry prepared in the above step is coated on the double-sided copper foil current collector. The negative electrode slurry 1 is coated on the first area part of the pole piece, and the negative electrode slurry 2 is coated on the second area part of the pole piece. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0375] 3. Rolling: After rolling, the thickness of the negative pole piece is 119 μm at room temperature.

[0376] 4. Laser cutting: The negative pole piece is cut into the required size of the pole piece for the battery using the existing laser cutting equipment.

[0377] Three, preparation of the winding type battery pole group

[0378] 1. Winding: The negative pole piece prepared in the above step is wound and assembled with the positive pole piece and the separator to form a pole group.

[0379] 2. Hot pressing: The pole group is hot pressed. The hot pressing conditions are: temperature 90°C, pressure 4t, and time 60s.

[0380] Four, battery preparation

[0381] 1. Assembly: The winding type battery pole group is welded with the adapter piece, the battery cover, etc., and the pole group protective sleeve is coated for assembly.

[0382] 2. Perimeter welding of the shell: The assembly and the gasket are placed in the battery shell, and the battery cover and the battery shell are perimetrically welded to form a semi-finished battery.

[0383] 3. Drying: The semi-finished battery is placed in an oven and dried at a temperature of 90°C and a pressure of -80 kPa for 24 hours.

[0384] 4. Liquid injection: The electrolyte is injected into the semi-finished battery.

[0385] 5. Formation: The semi-finished battery after liquid injection is charged and formed.

[0386] 6. Liquid supplementing and sealing: The semi-finished battery after formation is left to stand, supplemented with liquid, and sealed.

[0387] 7. Capacity grading: The battery after sealing is capacity graded.

[0388] 8. Aging, and finally obtaining the winding type lithium ion battery.

[0389] Example 10.

[0390] The application provides a winding type battery pole group and a preparation method of a winding type lithium ion battery.

[0391] I. Preparation of a positive pole piece, according to the weight ratio (parts) :

[0392] 1. Slurry preparation: 96 parts of lithium iron phosphate positive pole powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) are uniformly mixed in a slurry preparation tank, N-methyl pyrrolidone (NMP) is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 57.0%, and then the slurry is discharged.

[0393] 2. Coating: the specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the thickness of the carbon coating layer on the upper and lower sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm 2 .

[0394] 3. Rolling: the thickness of the positive pole piece after rolling is 185 μm at room temperature.

[0395] 4. Laser cutting: the positive pole piece is cut into the pole piece size required by the battery by using the existing laser cutting equipment.

[0396] II. Preparation of a negative pole piece, according to the weight ratio (parts) :

[0397] 1. Slurry preparation: 96 parts of graphite negative pole powder, 0.8 parts of conductive carbon black powder, 50 parts of single-walled carbon nanotube powder with an effective solid content of 0.4%, 66.6 parts of carboxymethyl cellulose sodium (CMC) binder glue solution with an effective solid content of 1.5% and 5 parts of styrene-butadiene rubber (SBR) binder glue solution with an effective solid content of 40% are uniformly mixed in a slurry preparation tank, deionized water is used as a solvent, the solid content of the slurry in the slurry preparation cylinder is adjusted to 48.0%, and then the slurry is discharged.

[0398] 2. Coating: the negative pole slurry prepared in the above step is coated on a double-light copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm 2 .

[0399] 3. Rolling: the thickness of the negative pole piece after rolling is 121 μm at room temperature.

[0400] 4. Laser cutting: the negative pole piece is cut into the pole piece size required by the battery by using the existing laser cutting equipment.

[0401] III. Preparation of a winding type battery pole group

[0402] 1. Winding: winding and assembling the positive electrode sheet, the negative electrode sheet and the separator prepared in the above steps into an electrode group.

[0403] 2. Hot pressing: hot pressing the electrode group, hot pressing conditions: temperature 90°C, pressure 4t, time 60s.

[0404] Four, battery preparation

[0405] 1. Assembly: welding the above electrode group with the adapter piece, the battery cover and the like, covering the electrode group protective sleeve, and assembling.

[0406] 2. Shell entry periphery welding: placing the above assembly and the bottom gasket into the battery shell, peripherally welding the battery cover and the battery shell to make a semi-finished battery.

[0407] 3. Drying: placing the above semi-finished battery into an oven, drying for 24h at a temperature of 90°C and a pressure of -80kPa.

[0408] 4. Liquid injection: injecting electrolyte into the above semi-finished battery.

[0409] 5. Formation: charging and forming the semi-finished battery after liquid injection.

[0410] 6. Liquid supplementing and sealing: standing the semi-finished battery after formation, supplementing liquid and sealing.

[0411] 7. Separation: separating the battery after sealing.

[0412] 8. Aging, finally obtaining a wound lithium ion battery.

[0413] Example 11.

[0414] Through this example, it is illustrated that by changing the battery shape structure and increasing the size of the electrode sheet, the electrode sheet compaction or coating amount can be reduced under the same capacity design, so as to slow down the corner lithium precipitation and improve the overall performance of the battery. This example refers to the implementation of the electrode group for the special-shaped battery structure design.

[0415] I. Preparation of positive electrode sheet, according to the weight ratio (parts):

[0416] 1. Slurry preparation: mixing 96 parts of lithium iron phosphate positive electrode powder, 2 parts of conductive carbon black powder and 2 parts of polyvinylidene fluoride binder (PVDF) uniformly in a slurry tank, using N-methyl pyrrolidone (NMP) as the solvent, adjusting the slurry solid content in the slurry cylinder to 57.0% dispersion, and then discharging.

[0417] 2. Coating: the specification of the carbon-coated aluminum foil is (13+1+1) μm, 13 μm is the thickness of the aluminum foil, and the carbon-coated layer on both sides of the aluminum foil is 1 μm. The double-sided area density of the electrode material is 40.0 mg / cm2.

[0418] 3. Rolling: the thickness of the positive electrode sheet after rolling is 185 μm at room temperature.

[0419] 4. Laser cutting: the positive electrode sheet is cut into the electrode sheet required for manufacturing the battery using the existing laser cutting equipment according to certain parameters.

[0420] II. Preparation of the negative electrode sheet, according to the weight ratio (parts):

[0421] 1. Slurry preparation: 96 parts of graphite negative electrode powder, 0.8 parts of conductive carbon black powder, 50 parts of single-walled carbon nanotube powder with an effective solid content of 0.4%, 66.6 parts of sodium carboxymethyl cellulose (CMC) binder glue solution with an effective solid content of 1.5%, and 5 parts of butadiene-styrene rubber (SBR) binder glue solution with an effective solid content of 40% are mixed uniformly in a slurry preparation tank, the solvent is deionized water, the slurry solid content in the slurry tank is adjusted to 48.0% for dispersion, and then the slurry is discharged.

[0422] 2. Coating: the negative electrode slurry prepared in the above step is coated on the double-sided copper foil current collector. The specification of the copper foil is 6 μm. The double-sided area density of the electrode material is 18.6 mg / cm2.

[0423] 3. Rolling: the thickness of the negative electrode sheet after rolling is 121 μm at room temperature.

[0424] 4. Laser cutting: the negative electrode sheet is cut into the electrode sheet required for manufacturing the battery using the existing laser cutting equipment.

[0425] III. Preparation of the wound electrode group

[0426] 1. Winding: the positive electrode sheet, the negative electrode sheet, and the separator prepared in the above steps are wound and assembled into an electrode group.

[0427] (2) Hot pressing: the electrode group is subjected to hot pressing, and the hot pressing conditions are: temperature 90℃, pressure 4t, and time 60S.

[0428] IV. Battery preparation

[0429] 1. Assembly: the electrode group is welded with the adapter sheet, the battery cover, etc., a protective sleeve is wrapped around the electrode group, and assembly is performed.

[0430] 2. Perimeter welding into the shell: the assembly and the gasket are placed into the battery shell, the battery cover is perimetrically welded to the battery shell, and a semi-finished battery is prepared.

[0431] 3. Drying: the semi-finished battery is placed in an oven and dried at a temperature of 90℃ and a pressure of -80kPa for 24h.

[0432] 4. Liquid injection: electrolyte is injected into the semi-finished battery.

[0433] 5. Formation: the semi-finished battery after liquid injection is charged and formed.

[0434] 6. Static liquid supplement sealing: after the formation of the semi-finished battery, the liquid is supplemented and sealed.

[0435] 7. Capacity distribution: the sealed battery is distributed.

[0436] 8. Aging: the final winding lithium ion battery is obtained.

[0437] The key parameters and the improvement of the corner of the electrode tab of the comparative example and the above-mentioned multiple embodiments are shown in Tables 1, 2 and 3.

[0438] Table 1 is different in design of the separator, the separator at the corner is different from the separator at the large surface, and the separator at the corner has one or more properties such as good liquid retention, low impedance, and slowing down the expansion of the electrode tab.

[0439] Table 1, the key parameters and the improvement of the corner of the electrode tab of the comparative example and the embodiments 1-3.

[0440]

[0441] As shown in Table 1, the corner of the separator of Example 1 is coated with a ceramic layer, which has a pore structure, can store more electrolyte compared with the comparative example, and improve the lithium ion transmission capacity of the corner, and the insulating layer can enhance the strength of the separator and improve the safety performance of the battery. The corner of the separator of Example 2 is coated with a bonding coating, which has a certain liquid retention capacity. Under temperature and pressure, it can be bonded with the positive and negative electrode tabs in the battery. Compared with the comparative example, this structure can ensure the electrode tab spacing and ion transmission speed during the charging and discharging process of the winding corner, reduce the active metal deposition during the expansion and deintercalation process of the electrode tab, avoid the active metal deposition and capacity loss of the electrode tab, and improve the performance of the battery. The porosity of the corner of the separator of Example 3 is super high. Compared with the comparative example, this structure can improve the ion deintercalation speed at the winding corner, avoid the active metal deposition and capacity loss of the electrode tab, and improve the performance of the battery.

[0442] Table 2 is different in design of the positive electrode tab, the positive electrode tab at the corner is different from the positive electrode tab at the large surface, and the positive electrode tab at the corner has one or more properties such as good liquid retention, low impedance, and slowing down the expansion of the electrode tab.

[0443] Table 2, the key parameters and the improvement of the corner of the electrode tab of the comparative example and the embodiments 4-7.

[0444]

[0445] As shown in Table 2, the corner of the positive electrode of Example 4 uses a mixed lithium iron phosphate positive electrode layer prepared by doping small particle size nano lithium iron phosphate with ordinary lithium iron phosphate. Compared with the comparative example, this structure improves the rate performance and ion transmission capacity of the corner, thereby improving the performance of the battery.

[0446] The corner of the positive electrode of Example 5 is prepared by using a composite conductive agent. Compared with the comparative example, the kinetic performance is higher, the ion transmission capacity of the corner is improved, and the safety performance of the battery is improved.

[0447] The corner of Example 6 is designed as a diamond grid structure. Compared with the comparative example, this structure can provide space for the expansion of the electrode sheet during charging and discharging. The ion transmission rate is ensured, the active metal deposition caused by the expansion and deintercalation of the electrode sheet is reduced, the active metal precipitation and capacity loss of the electrode sheet are avoided, and the performance of the battery is improved.

[0448] The corner of Example 7 is prepared by using a polyacrylonitrile-sodium acrylate and polyvinylidene fluoride composite binder. Compared with the comparative example, the electrolyte swelling resistance of the electrode sheet can provide space for the expansion of the electrode sheet during charging and discharging. The impedance is low, the ion transmission capacity of the corner is improved, and the cycle performance of the battery is improved.

[0449] Table 3 is different in the design of the negative electrode sheet, the corner of the negative electrode sheet is different from the negative electrode sheet of the large area, and the corner of the negative electrode sheet has one or more properties such as good liquid retention, low impedance, and reducing the expansion of the electrode sheet.

[0450] Table 3, the key parameters of the comparative example and Examples 8-10, and the improvement of the corner of the electrode sheet.

[0451]

[0452] As can be seen from Table 3, the corner of the negative electrode of Example 8 is prepared by using a mixed graphite layer of graphite doped with small particle size graphite. Compared with the comparative example, the structure improves the rate performance and ion transmission capacity of the corner, thereby improving the performance of the battery. The corner of the negative electrode of Example 9 is prepared by using a graphite layer composed of carbon black and single-walled carbon nanotubes. Compared with the comparative example, the kinetic performance is higher, the ion transmission capacity of the corner is improved, and the safety performance of the battery is improved. The corner of Example 10 is prepared by using a graphite layer prepared by using a polyacrylate and butyl benzene latex composite binder. Compared with the comparative example, the electrolyte swelling resistance of the electrode sheet is strong, which can provide space for the expansion of the electrode sheet during charging and discharging. The impedance is low, the ion transmission capacity of the corner is improved, and the cycle performance of the battery is improved.

[0453] Example 11 is to change the battery shape structure to improve the lithium precipitation at the corner: by increasing the size of the electrode sheet, under the same capacity design, the electrode sheet compaction or coating amount can be reduced, and the battery liquid injection amount can also be increased, thereby reducing the lithium precipitation at the corner and improving the overall performance of the battery. Compared with the ordinary battery structure, this structure can increase the liquid injection amount or increase the electrode sheet size while reducing the electrode sheet compaction or coating amount on the basis of ensuring the shell ratio, thereby improving the processing performance and electrical performance of the battery. At the same time, this structure also provides space to increase the electrode sheet area, thereby increasing the capacity of the battery and improving the energy density of the battery.

[0454] In summary, compared with the prior art, the winding type battery pole group and the lithium ion battery provided by the application have the advantages of scientific design, and the winding corner lithium precipitation problem of the winding type battery can be effectively solved through the new structure design of the positive plate, the negative plate and the separator in the pole group and the structural innovation of the battery shell, so that the cycle performance and the safety performance of the battery are improved, and the application has great production practical significance.

[0455] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A wound battery pole pack, characterized by, The positive electrode sheet (1001), the negative electrode sheet, and the separator (1003) located between the positive electrode sheet (1001) and the negative electrode sheet (1002); The winding type battery pole group includes a winding corner area part (101) of the pole group and a winding flat area part (102) of the pole group; The winding corner area part (101) of the pole group is located at both ends of the winding flat area part (102) of the pole group; The separator, the positive electrode sheet, and the negative electrode sheet each include a first area part and a second area part; The first area part of the separator, the positive electrode sheet, and the negative electrode sheet is in the winding corner area part (101) of the pole group, and the second area part of the separator, the positive electrode sheet, and the negative electrode sheet is in the winding flat area part (102) of the pole group; The content of the conductive agent in the first area part of the positive electrode sheet is higher than that in the second area part of the positive electrode sheet; The particle size of the positive electrode active material particles in the first area part of the positive electrode sheet is smaller than that in the second area part of the positive electrode sheet; The content of the conductive agent in the first area part of the negative electrode sheet is higher than that in the second area part of the negative electrode sheet; The particle size of the negative electrode active material particles in the first area part of the negative electrode sheet is smaller than that in the second area part of the negative electrode sheet; The graphitization degree of the negative electrode active material particles in the first area part of the negative electrode sheet is lower than the content of the conductive agent in the second area part of the negative electrode sheet; The impedance of the binder in the first area part of the negative electrode sheet is lower than that in the second area part of the negative electrode sheet.

2. The wound battery pole pack of claim 1, wherein, The first area part of the separator includes any one of a base film, a base film with an insulating layer coated on one side surface, a base film with insulating layers coated on both upper and lower side surfaces, a base film with a bonding layer coated on one side surface, a base film with bonding layers coated on both upper and lower side surfaces, and a base film with an insulating layer and a bonding layer coated on one side in sequence and an insulating layer coated on the other side; The second area part of the separator includes any one of a base film, a base film with an insulating layer coated on one side surface, a base film with insulating layers coated on both upper and lower side surfaces, a base film with a bonding layer coated on one side surface, a base film with bonding layers coated on both upper and lower side surfaces, a base film with an insulating layer and a bonding layer coated on one side in sequence and an insulating layer coated on the other side, and a base film with an insulating layer and a bonding layer coated on both upper and lower side surfaces in sequence; The bonding layer of the separator only contains a component of the binder; The binder of the separator specifically includes any one of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, polyacrylate, sodium polyacrylate, and styrene butadiene rubber; The material of the base film is selected from any one of polyethylene, polypropylene, and polyimide; The insulating layer is selected from an insulating component, a binder and a dispersant; wherein the insulating component includes at least one of hydrated aluminum oxide and hydrated boehmite; the binder includes a water-soluble binder, a solvent-type binder and an emulsion-type binder, and is selected from any one of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, polyacrylate, sodium polyacrylate and styrene butadiene rubber; wherein the dispersant is used to promote uniform dispersion of the slurry, and specifically includes any one of polyoxyethylene diester, polytetramethylene glycol monostearate, polyvinylpyrrolidone, polyethylene oxide and methyl cellulose; In the insulating layer of the diaphragm, the mass percentage of the insulating component is 78.0% to 94.9%, the mass percentage of the binder is 5% to 20%, and the mass percentage of the dispersant is 0.1% to 1%.

3. The wound battery pole pack of claim 1, wherein The first area part of the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and in the positive electrode active material layer, a conductive agent with a mass percentage of 1% to 4%, positive electrode active material particles with a mass percentage of 92% to 98%, and a binder with a mass percentage of 1% to 4% are included; The positive electrode active material particles are selected from any one of lithium iron phosphate particles, ternary positive electrode particles, lithium cobaltate particles and lithium manganate particles; The conductive agent is selected from at least one of carbon nanotubes, carbon black and graphene; The binder is selected from any one of polyvinylidene fluoride, polyvinylidene fluoride and polyhexafluoropropylene copolymer poly(vinylidene fluoride-hexafluoropropylene) and poly(acrylonitrile-sodium acrylate); In the first area part of the positive electrode sheet, the median particle size D50 of the positive electrode active material particles is 0.5 to 1.3 μm.

4. The wound battery pole pack of claim 1, wherein, A pre-designed concave-convex mark structure is arranged on the first area part of the positive electrode sheet; The second area part of the positive electrode sheet is not provided with the concave-convex mark structure.

5. The wound battery pole pack of claim 1, wherein, The second area part of the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and in the positive electrode active material layer, a conductive agent with a mass percentage of 0.3% to 2%, positive electrode active material particles with a mass percentage of 94% to 98.7%, and a binder with a mass percentage of 1% to 4% are included; The positive electrode active material particles are selected from any one of lithium iron phosphate particles, ternary positive electrode material, lithium cobaltate particles and lithium manganate particles; The conductive agent is selected from at least one of carbon nanotubes, carbon black and graphene; The binder is selected from any one of polyvinylidene fluoride, polyvinylidene fluoride and polyhexafluoropropylene copolymer poly(vinylidene fluoride-hexafluoropropylene) and poly(acrylonitrile-sodium acrylate); In the second area part of the positive electrode sheet, the median particle size D50 of the positive electrode active material particles is 0.8 to 3.0 μm.

6. The wound battery pole pack of claim 1, wherein, The first area part of the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and in the negative electrode active material layer, a conductive agent with a mass percentage of 1% to 2%, negative electrode active material particles with a mass percentage of 94% to 97%, and a binder with a mass percentage of 2% to 4% are included; The negative electrode active material particles are selected from at least one of natural graphite particles and artificial graphite particles; The conductive agent is selected from at least one of carbon nanotubes, carbon black and graphene; The binder is selected from at least one of a styrene-butadiene latex, a styrene-acrylate, a carboxymethyl cellulose, and an acrylic multi-copolymer; In the first region portion of the negative electrode sheet, the median particle size D50 of the negative electrode active material particles is 11 to 15 μm; In the first region portion of the negative electrode sheet, the graphitization degree of the negative electrode active material particles is 91 to 94%.

7. The wound battery pole pack of claim 1, wherein, The second region portion of the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, in which the negative electrode active material layer includes 0.3 to 1.2% by mass of a conductive agent, 94.8 to 97.7% by mass of negative electrode active material particles, and 2 to 4% by mass of a binder; The negative electrode active material particles are selected from at least one of natural graphite particles and artificial stone particles; The conductive agent is selected from at least one of carbon nanotubes, carbon black, and graphene; The binder is selected from at least one of a styrene-butadiene latex, a styrene-acrylate, a carboxymethyl cellulose, and an acrylic multi-copolymer; In the second region portion of the negative electrode sheet, the median particle size D50 of the negative electrode active material particles is 14 to 20 μm; In the second region portion of the negative electrode sheet, the graphitization degree of the negative electrode active material particles is 93 to 96%.

8. A lithium-ion battery, characterized by The wound battery pole group includes the wound battery pole group according to any one of claims 1 to 7; The wound battery pole group (100) is located in the inner cavity of the hollow, top-opened square battery aluminum shell (1); The top of the square battery aluminum shell (1) is sealingly provided with a battery cover plate (4); The square battery aluminum shell (1) is filled with an electrolyte (3).

9. The lithium-ion battery of claim 8, wherein, The positive electrode tab of the wound battery pole group (100) is connected to the bottom end of the vertical through positive electrode pole of the battery cover plate (4) through a positive electrode adapter piece (5); The negative electrode tab of the wound battery pole group (100) is connected to the bottom end of the vertical through negative electrode pole of the battery cover plate (4) through a negative electrode adapter piece (6); The wound battery pole group (100) is provided between the inner side of the square battery aluminum shell (1) and the pole group protection sleeve (7); The pole group protection sleeve (7) is wrapped on the outer surface of the wound battery pole group (100) and is used to insulate and isolate the wound battery pole group (100) from the square battery aluminum shell (1); The bottom inner side of the square battery aluminum shell (1) is provided with a lower gasket (8); The top of the square battery aluminum shell (1) is provided with an insulating outer gasket (9); The outer surface of the square battery aluminum shell (1) is wrapped with an outer wrapping insulation film (10).

10. The lithium-ion battery of claim 8, wherein the lithium-ion battery is a lithium-ion battery having a capacity of at least 1 Ah. The battery cover plate (4) has a housing protrusion (11) protruding upward in the region between the positive electrode pole (401) and the negative electrode pole (402); The housing protrusion (11) is in the shape of an isosceles trapezoid.

Images