Ultra-fast charging pole piece, battery cell, lithium ion battery and preparation method

Abstract

The invention provides an ultrafast charging pole piece, a battery cell, a lithium ion battery and a preparation method, and relates to the technical field of new energy batteries, the pole piece comprises a current collector and coating layers on two sides of the current collector; the coating layer is provided with a straight hole, and the straight hole is formed by spraying a pore-forming agent when the current collector is unwound and / or spraying the pore-forming agent before the current collector coated with slurry enters a drying oven; and the addition amount of the pore-forming agent on the single-side current collector is 0.001-0.01% of the total mass of the coating slurry on the single-side current collector. The porosity of the pole piece can be increased, the electrolyte absorption capability of the pole piece can be greatly improved, the infiltration performance is improved, the compactness of a formed film is improved, the side reaction of the negative electrode LiCx and the electrolyte in the charging process is inhibited, and the charging rate capability is improved. Meanwhile, the surface density and infiltration of the pole piece and the impedance of the battery cell can be considered, so that the energy density and power density of the battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy batteries, and in particular to an ultra-fast charging negative electrode sheet, a battery cell, a lithium-ion battery and a preparation method thereof. Background Art

[0002] With the development of new energy industry, people's demand for lithium-ion batteries is increasing, and the performance requirements for lithium batteries are becoming increasingly stringent. In order to meet people's needs, the battery cell must increase the charging speed, improve the low-temperature charging and discharging performance, and reduce the impedance of the battery cell. At present, researchers mainly focus on material modification research, development of new materials, and optimization of battery structure.

[0003] Current research and industry experience show that the main constraint on battery charging speed is the negative terminal, which is currently mainly improved through research on negative electrode material modification and development of new materials to increase the material's gram capacity and charging capacity; and by optimizing the battery core structure, such as the welding cross-sectional area of ​​the pole ear, the thickness of the core, etc., but the cost is high and there are few actual applications, especially the time cycle from the development of new materials to their large-scale application in lithium-ion batteries in service is long and difficult; and optimizing the battery structure will result in a lower process yield and high cost.

[0004] In addition, in the existing research on the modification of electrode plates, it is impossible to take into account the surface density, wetting and impedance of the battery cell at the same time, and it is impossible to effectively improve the cycle life, rate performance and stability of the battery.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide an ultra-fast charging electrode sheet, a battery cell, a lithium-ion battery and a preparation method. The present invention can increase the porosity of the electrode sheet, greatly improve the ability of the electrode sheet to absorb electrolyte, improve the wetting performance, improve the density of the chemical film, inhibit the side reaction between the negative electrode LiCx and the electrolyte during the charging process, and improve the charging rate capability. At the same time, the electrode sheet surface density, wetting and the impedance of the battery cell can be taken into account, so the energy density and power density of the battery can be improved.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides an ultra-fast charging pole piece, the pole piece comprising a current collector and coating layers on both sides of the current collector;

[0009] The coating layer is provided with straight holes, and the straight holes are formed by spraying a pore-forming agent when the current collector is unrolled and / or spraying a pore-forming agent before the current collector coated with the slurry enters the oven;

[0010] The added amount of the pore-forming agent on the single-side current collector is 0.001% to 0.01% of the total mass of the slurry coated on the single-side current collector.

[0011] Further, based on the above technical solution, the volume of the straight hole accounts for 1 / 100000 to 1 / 10000 of the coating volume;

[0012] And / or, the straight hole has a depth of 4-50 μm;

[0013] And / or, the straight hole has an aperture of 0.1-500 nm.

[0014] Further, based on the above technical solution, the pore-forming agent includes one or more of lithium chloride, ammonium bicarbonate, elemental iodine, ferric chloride or methyl methacrylate;

[0015] And / or, the particle size of the pore former is 2-50 μm.

[0016] Further, based on the above technical solution, the current collector includes copper foil;

[0017] And / or, the coating layers on both sides of the current collector have a thickness of 10-100 μm.

[0018] Further, based on the above technical solution, the coating slurry of the coating layer includes: a conductive agent, a binder and an active material.

[0019] Further, based on the above technical solution, the conductive agent includes one or more of conductive carbon black SP, carbon nanotubes CNT or acetylene black;

[0020] and / or, the active material comprises one or more of artificial graphite, natural graphite, silicon-oxygen or silicon-carbon materials;

[0021] And / or, the binder includes at least one of polyacrylic acid, sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0022] The present invention also provides a method for preparing the ultra-fast charging electrode sheet as described above, comprising the following steps:

[0023] S1: mixing active materials, conductive agents and binders to obtain active slurry;

[0024] S2: coating the active slurry on the current collector, spraying a pore-forming agent on the current collector coated with the slurry, and then performing air drying to form straight holes in the coating layer formed by the active slurry;

[0025] Alternatively, a pore-forming agent is sprayed on the current collector, and then the active slurry is coated on the current collector, and air-dried, so that the coating layer formed by the active slurry forms straight pores;

[0026] S3: The electrode with straight holes is rolled, die-cut and slit to obtain an ultra-fast charging electrode.

[0027] Further, based on the above technical solution, the mass ratio of the active material, the conductive agent, and the binder is (94-96): (0.5-1.5): (2-4.5);

[0028] and / or, the viscosity of the active slurry is 2000 to 15000 cps;

[0029] And / or, the solid content of the active slurry is 48%-54%;

[0030] And / or, the surface density of the slurry coated on the current collector is 170-200 g / m 2 ;

[0031] and / or, the coating speed of the active slurry on the current collector is ≤20 m / min;

[0032] And / or, the temperature of the blast drying is 50-110° C., and the wind frequency of the blast drying is 15-45 Hz;

[0033] And / or, the compaction density of the roller is 0.5 to 1.8 g / cm 3 ;

[0034] And / or, in step S2, the pore-forming agent is sprayed by a dry powder spraying device.

[0035] The present invention also provides a battery core, including an ultra-fast charging pole piece made by the method for making the ultra-fast charging pole piece as described above or an ultra-fast charging pole piece as described above.

[0036] The present invention also provides a lithium-ion battery, which contains the ultra-fast charging pole piece prepared by the method for preparing the ultra-fast charging pole piece as described above or the ultra-fast charging pole piece as described above or contains the battery cell as described above.

[0037] The present invention provides an ultra-fast charging electrode sheet, a battery cell, a lithium-ion battery and a preparation method, and the beneficial effects are as follows:

[0038] 1. The present invention does not increase the process by adding a pore-forming agent that is easy to sublimate when coating the pole piece, and is simple to operate and low in cost. The present invention can reduce the tortuosity (τ) or McMullin number (Nm) of the pole piece by providing a straight hole on the pole piece, which can greatly improve the embedding of lithium ions on the pole piece surface into the pole piece, avoid the precipitation of lithium ions on the pole piece surface, reduce the uneven polarization of the electrode, and improve the charging rate capability of the battery. The hole on the pole piece can be used as a release point when the pole piece expands during the battery charging process without deformation, reducing the deformation of the battery core, and improving the cycle life, rate performance and stability of the battery.

[0039] 2. The present invention can increase the porosity of the pole piece, greatly improve the ability of the pole piece to absorb electrolyte, improve the wetting performance, improve the density of the film formation, inhibit the side reaction between the negative electrode LiCx and the electrolyte during the charging process, and improve the charging rate capability. At the same time, the pole piece surface density, wetting and the impedance of the battery cell can be taken into account, so the energy density and power density of the battery can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 The overall structure diagram of the negative electrode sheet provided by the present invention;

[0042] Figure 2 A schematic diagram of a straight hole on a coating layer provided by the present invention;

[0043] Figure 3 It is a comparison chart of the charging rates of Examples 1-3 and Comparative Example 1;

[0044] icon:

[0045] 1. Front coating layer; 2. Current collector; 3. Back coating layer; 4. Straight hole. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0047] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0048] According to a first aspect of the present invention, there is provided an ultrafast charging electrode sheet, the electrode sheet comprising a current collector and coating layers on both sides of the current collector;

[0049] The coating layer is provided with straight holes, and the straight holes are formed by spraying a pore-forming agent when the current collector is unrolled and / or spraying a pore-forming agent before the current collector coated with the slurry enters the oven;

[0050] The amount of porogen added to the single-sided current collector is 0.001% to 0.01% (for example, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, etc.) of the total mass of the coating slurry on the single-sided current collector.

[0051] Specifically, Figure 1-2 As shown, the current collector 2 of the pole piece has a front coating layer 1 and a back coating layer 2 on both sides, and the coating layer is provided with straight holes 4; if the slurry is only coated on one side of the current collector 2, the two sides of the current collector 2 will be greatly different, which will have an adverse effect on the battery performance.

[0052] Specifically, placing the pore former directly on the current collector (foil) or spraying the pore former before the current collector coated with the slurry enters the oven can effectively ensure the pore forming effect, so by adding a small amount of pore former, a certain proportion of pore defects can be left on the surface of the current collector. Compared with the prior art of directly dissolving and dispersing the pore former in the positive or negative electrode slurry, the ultra-fast charging sheet provided by the present invention not only adds less pore former, but also ensures the pore forming effect of the pore former and the uniformity of the pores.

[0053] Furthermore, if the amount of pore former added is greater than 0.01% of the total mass of the slurry coated on the electrode, the electrode coating surface density will be low, thereby causing the risk of lithium plating.

[0054] As an optional embodiment of the present invention, the volume of the straight holes accounts for 1 / 100000 to 1 / 10000 (such as 1 / 20000, 1 / 30000, 1 / 40000, 1 / 50000, 1 / 60000, 1 / 70000, 1 / 80000, 1 / 90000, etc.) of the coating volume.

[0055] As an optional embodiment of the present invention, the straight hole has a depth of 4-50 μm (for example, 10 μm, 20 μm, 30 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, etc.), and a straight hole diameter of 0.1-500 nm (for example, 50 nm, 100 nm, 200 nm, 300 nm, 450 nm, 480 nm, etc.).

[0056] Specifically, by leaving a certain proportion of hole defects on the surface of the pole piece, the hole is a straight hole, which can be used as a channel for the deintercalation of some lithium ions. The straight hole with a hole depth of 4-50μm and a hole diameter of 0.1-500nm can reduce the tortuosity (τ) or McMullin number (Nm) of the pole piece, and at the same time can increase the porosity (ξ) of the pole piece to a certain extent. The three satisfy the formula Nm=τ / ξ. When any value of the McMullin number or tortuosity remains unchanged, reducing the pole piece tortuosity or McMullin number can reduce the actual migration path of lithium ions or sodium ions inside the pole piece, and reduce the complexity and difficulty of ion migration inside the pole piece; at the same time, increasing the porosity of the pole piece can increase the liquid absorption of the pole piece, increase the reaction points of lithium ions or sodium ions on the surface of the pole piece, thereby increasing the battery charging speed, reducing the polarization of the battery, and reducing the charging temperature rise, which can achieve the effect of improving the charging and discharging energy efficiency and extending the cycle life of the battery.

[0057] Furthermore, if the diameter of the straight hole is greater than 500 nm, other substances may enter during the baking process, resulting in hole blockage.

[0058] As an optional embodiment of the present invention, the pore former includes one or more of lithium chloride, ammonium bicarbonate, elemental iodine, ferric chloride or methyl methacrylate.

[0059] As an optional embodiment of the present invention, the particle size of the pore former is 2-50 μm (such as 10 μm, 20 μm, 30 μm, 40 μm, 45 μm, 48 μm, etc.).

[0060] As an optional embodiment of the present invention, the current collector includes copper foil;

[0061] And / or, the coating layers on both sides of the current collector have a thickness of 10-100 μm.

[0062] Specifically, if the thickness of the coating layer increases, the surface density of the coating slurry on the corresponding current collector will also increase, thereby affecting the fast charging effect.

[0063] Furthermore, in the present invention, the thickness of the coating layer on both sides of the current collector is greater than the depth of the straight hole, thereby avoiding the phenomenon that the pore-forming agent penetrates the coating layer and causes leakage of the foil.

[0064] As an optional embodiment of the present invention, the coating slurry of the coating layer includes: a conductive agent, a binder and an active material.

[0065] As an optional embodiment of the present invention, the conductive agent includes one or more of conductive carbon black SP, carbon nanotubes CNT or acetylene black.

[0066] As an optional embodiment of the present invention, the active material includes one or more of artificial graphite, natural graphite, silicon-oxygen or silicon-carbon materials.

[0067] As an optional embodiment of the present invention, the binder includes at least one of polyacrylic acid PAA, sodium carboxymethyl cellulose CMC and styrene-butadiene rubber SBR.

[0068] According to a second aspect of the present invention, there is provided a method for preparing the ultra-fast charging electrode sheet as described above, comprising the following steps:

[0069] S1: mixing active materials, conductive agents and binders to obtain active slurry;

[0070] S2: coating the active slurry on the current collector, spraying a pore-forming agent on the current collector coated with the slurry, and then performing air drying to form straight holes in the coating layer formed by the active slurry;

[0071] Alternatively, a pore-forming agent is sprayed on the current collector, and then the active slurry is coated on the current collector, and air-dried, so that the coating layer formed by the active slurry forms straight pores;

[0072] S3: The electrode with straight holes is rolled, die-cut and slit to obtain an ultra-fast charging electrode.

[0073] Specifically, in step S2, the active slurry is preferably coated on the current collector, and the pore-forming agent is sprayed on the current collector coated with the slurry.

[0074] Furthermore, the method for preparing the ultrafast charging electrode sheet provided by the present invention can also be applied to the preparation of positive electrode sheets, wherein the active slurry is a positive electrode active slurry conventionally used in the art containing lithium iron phosphate LFP, lithium cobalt oxide LCO, lithium manganese oxide LMO, lithium manganese iron phosphate LMFP or nickel cobalt lithium manganese oxide ternary materials;

[0075] The current collector is a common current collector for positive electrode sheets in the art, such as aluminum foil.

[0076] As an optional embodiment of the present invention, the mass ratio of the active material, the conductive agent, and the binder is (94-96): (0.5-1.5): (2-4.5), such as 95:1:4, 96:0.7:3.3, 96:1.3:2.7, 95:1.5:3.5, and the like.

[0077] As an optional embodiment of the present invention, at a temperature of 22-30° C., the viscosity of the active slurry is 2000-15000 cps (e.g., 3000 cps, 5000 cps, 7000 cps, 9000 cps, 11000 cps, 13000 cps, etc.); the surface density of the slurry coated on the current collector is 170-200 g / m 2 (For example 175g / m 2 , 180g / m 2 , 185g / m2 , 190g / m 2 , 195g / m 2 wait).

[0078] As an optional embodiment of the present invention, the solid content of the active slurry is 48%-54% (such as 49%, 50%, 51%, 52%, 53%, etc.).

[0079] As an optional embodiment of the present invention, the coating speed of the active slurry on the current collector is ≤20 m / min.

[0080] As an optional embodiment of the present invention, the temperature of the blast drying is 50-110°C (for example, 60°C, 70°C, 80°C, 90°C, 100°C, etc.), and the wind frequency of the blast drying is 15-45Hz (for example, 20Hz, 25Hz, 30Hz, 35Hz, 40Hz, etc.).

[0081] Specifically, if the drying temperature is less than 50°C, it will affect the negative electrode coating efficiency and prolong the drying time; if the drying temperature is greater than 110°C, it may cause the electrode to crack due to excessive temperature.

[0082] As an optional embodiment of the present invention, the compaction density of the roller is 0.5 to 1.8 g / cm 3 (For example, 0.7g / cm 3 , 0.9g / cm 3 , 1g / cm 3 , 1.3g / cm 3 , 1.5g / cm 3 wait).

[0083] As an optional embodiment of the present invention, in step S2, the pore-forming agent is sprayed by a dry powder spraying device;

[0084] The dry powder spraying equipment typically but not limitedly includes a dry powder spraying machine, a dry powder spraying gun, a fully automatic powder spraying equipment, an electrostatic powder spraying equipment, etc.

[0085] According to a third aspect of the present invention, a battery cell is provided, wherein the battery cell comprises the ultra-fast charging electrode as described above.

[0086] According to a fourth aspect of the present invention, there is provided a method for preparing a battery cell as described above, comprising the following steps: winding or stacking the ultrafast charging electrode sheets as described above to obtain a bare battery cell, and then subjecting the bare battery cell to baking, liquid injection, chemical formation, aging and capacity separation to obtain a finished battery cell.

[0087] According to a fifth aspect of the present invention, a lithium-ion battery is provided, wherein the lithium-ion battery comprises the above-mentioned ultra-fast charging electrode sheet or the above-mentioned battery cell.

[0088] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0089] Example 1

[0090] S1: dissolving artificial graphite, SP, CMC and SBR in deionized water and mixing them to obtain negative electrode active slurry;

[0091] Among them, the mass ratio of artificial graphite, SP, CMC and SBR is 96.0:1.0:1.6:1.4;

[0092] At a temperature of 25°C, the viscosity of the negative electrode active slurry is 6000cps;

[0093] The solid content of the negative electrode active slurry is 52%;

[0094] S2: spraying the pore-forming agent ammonium bicarbonate (particle size of 35 μm) on the front and back of the copper foil, and then evenly coating the negative electrode active slurry on the front and back of the copper foil at a coating speed of ≤20 m / min, and performing air drying;

[0095] Among them, the amount of ammonium bicarbonate added as a pore-forming agent on the single-sided copper foil accounts for 0.005% of the total mass of the coating slurry on the single-sided copper foil;

[0096] The temperature of blast drying is 90°C and the wind frequency is 25Hz;

[0097] The volume of straight holes accounts for 1 / 50000 to 1 / 20000 of the coating volume;

[0098] The average hole depth of the straight holes is 30 μm;

[0099] The average pore diameter of the straight pores is 350 nm;

[0100] The coating layer has a thickness of 65 μm;

[0101] S3: rolling, die-cutting and slitting the electrode sheet with pores to obtain a negative electrode sheet;

[0102] Among them, the compaction density of roller pressing is 1.58g / cm 3 .

[0103] Example 2

[0104] S1: dissolving artificial graphite, SP, CMC and SBR in deionized water and mixing them to obtain negative electrode active slurry;

[0105] Among them, the mass ratio of artificial graphite, SP, CMC and SBR is 96.0:1.0:1.6:1.4;

[0106] The solid content of the negative electrode active slurry is 53%;

[0107] At a temperature of 25°C, the viscosity of the active slurry is 7000cps;

[0108] S2: The negative electrode active slurry is uniformly coated on the front and back sides of the copper foil at a coating speed of ≤20 m / min, and lithium chloride (particle size of 35 μm) is sprayed on the front and back sides of the copper foil coated with the slurry, and then air-dried;

[0109] The amount of lithium chloride as a pore-forming agent added to the single-sided copper foil accounts for 0.005% of the total mass of the coating slurry on the single-sided copper foil;

[0110] The temperature of blast drying is 100°C and the wind frequency is 30Hz;

[0111] The volume of straight holes accounts for 1 / 50000 to 1 / 20000 of the coating volume;

[0112] The average hole depth of the straight holes is 31 μm;

[0113] The average pore diameter of the straight pores is 355 nm;

[0114] The coating layer has a thickness of 65 μm;

[0115] S3: rolling, die-cutting and slitting the electrode sheet with pores to obtain a negative electrode sheet;

[0116] Among them, the compaction density of roller pressing is 1.58g / cm 3 .

[0117] Example 3

[0118] S1: dissolving artificial graphite, SP, CMC and SBR in deionized water and mixing them to obtain negative electrode active slurry;

[0119] Among them, the mass ratio of artificial graphite, SP, CMC and SBR is 96.0:1.0:1.6:1.4;

[0120] At a temperature of 25°C, the viscosity of the negative electrode active slurry is 6000cps;

[0121] The solid content of the negative electrode active slurry is 52%;

[0122] S2: spraying ammonium bicarbonate (with a particle size of 40 μm) on the front and back of the copper foil, and then uniformly coating the negative electrode active slurry on the front and back of the copper foil at a coating speed of ≤20 m / min, and then spraying ammonium bicarbonate (with a particle size of 40 μm) on the copper foil coated with the slurry, and finally performing air drying;

[0123] Wherein, the ammonium bicarbonate sprayed on the single-side copper foil coated with the slurry accounts for 0.005% of the total mass of the slurry coated on the single-side copper foil;

[0124] The total amount of ammonium bicarbonate added is 0.01% of the total mass of the slurry coated on the front and back sides of the copper foil;

[0125] The temperature of blast drying is 90°C and the wind frequency is 25Hz;

[0126] The volume of the straight hole accounts for 1 / 12500 to 1 / 10000 of the coating volume;

[0127] The average hole depth of the straight holes is 35 μm;

[0128] The average pore diameter of the straight pores is 300 nm;

[0129] The coating layer has a thickness of 70 μm;

[0130] S3: rolling, die-cutting and slitting the electrode sheet with pores to obtain a negative electrode sheet;

[0131] Among them, the compaction density of roller pressing is 1.58g / cm 3 .

[0132] Example 4

[0133] S1: dissolving silicon-carbon material, acetylene black, PAA and SBR in deionized water and mixing them to obtain a negative electrode active slurry;

[0134] Among them, the mass ratio of silicon carbon material, acetylene black, PAA and SBR is 95:1:3.0:1.0;

[0135] At a temperature of 25°C, the viscosity of the negative electrode active slurry is 3500cps;

[0136] The solid content of the negative electrode active slurry is 52%;

[0137] S2: The negative electrode active slurry is uniformly coated on the front and back sides of the copper foil at a coating speed of ≤20 m / min, and methyl methacrylate (crystalline methyl methacrylate with a particle size of 40 μm) is sprayed on the front and back sides of the copper foil coated with the slurry, and then air-dried;

[0138] The amount of methyl methacrylate as a pore-forming agent added to the single-sided copper foil accounts for 0.001% of the total mass of the coating slurry on the single-sided copper foil;

[0139] The temperature of blast drying is 90°C and the wind frequency is 25Hz;

[0140] The volume of straight holes accounts for 1 / 100000 to 1 / 20000 of the coating volume;

[0141] The average hole depth of the straight holes is 35 μm;

[0142] The average pore diameter of the straight pores is 500 nm;

[0143] The coating layer has a thickness of 70 μm;

[0144] S3: rolling, die-cutting and slitting the electrode sheet with pores to obtain a negative electrode sheet;

[0145] Among them, the compaction density of roller pressing is 1.55g / cm 3 .

[0146] Example 5

[0147] S1: dissolving artificial graphite, acetylene black, CMC and SBR in deionized water and mixing them to obtain a negative electrode active slurry;

[0148] Among them, the mass ratio of artificial graphite, acetylene black, CMC and SBR is 96.0:1.0:1.6:1.4;

[0149] At a temperature of 25°C, the viscosity of the negative electrode active slurry is 4000cps;

[0150] The solid content of the negative electrode active slurry is 50%;

[0151] S2: Spray lithium chloride (particle size 30 μm) on the front and back of the copper foil, then evenly coat the negative electrode active slurry on the front and back of the copper foil, and dry it with air blast;

[0152] The amount of lithium chloride as a pore-forming agent added to the single-sided copper foil accounts for 0.001% of the total mass of the coating slurry on the single-sided copper foil;

[0153] The temperature of blast drying is 90°C and the wind frequency is 25Hz;

[0154] The volume of straight holes accounts for 1 / 100000 to 1 / 20000 of the coating volume;

[0155] The average hole depth of the straight holes is 25 μm;

[0156] The average pore diameter of the straight pores is 300 nm;

[0157] The coating layer has a thickness of 65 μm;

[0158] S3: rolling, die-cutting and slitting the electrode sheet with pores to obtain a negative electrode sheet;

[0159] Among them, the compaction density of roller pressing is 1.58g / cm 3 .

[0160] Comparative Example 1

[0161] The main difference between this comparative example and Example 1 is that no pore-forming agent is added, that is, in step S2, after the negative electrode slurry is evenly coated on the front and back surfaces of the copper foil, it is directly blown dried, and the remaining steps and technical parameters are the same as those in Example 1.

[0162] Comparative Example 2

[0163] The main difference between this comparative example and Example 1 is that the amount of ammonium bicarbonate added as a pore-forming agent on the single-sided copper foil accounts for 0.05% of the total coating mass on the single-sided copper foil, and the remaining steps and technical parameters are the same as those in Example 1.

[0164] Comparative Example 3

[0165] The main difference between this comparative example and Example 1 is that the pore-forming agent is dissolved in the negative electrode active slurry, and then coated on the copper foil, which specifically includes the following steps:

[0166] S1: dissolving artificial graphite, SP, CMC and SBR in deionized water, adding a pore-forming agent and mixing to obtain a negative electrode active slurry;

[0167] Among them, the mass ratio of artificial graphite, SP, CMC, SBR and ammonium bicarbonate is 95.95:1.0:1.6:1.4:0.05.

[0168] At a temperature of 25°C, the viscosity of the negative electrode active slurry is 6000cps;

[0169] The solid content of the active slurry is 52%;

[0170] S2: Coat evenly on the front and back sides of the copper foil at a coating speed of ≤20m / min, and perform air drying;

[0171] The temperature of blast drying is 90°C and the wind frequency is 25Hz;

[0172] S3: rolling, die-cutting and slitting the electrode sheet with pores to obtain a negative electrode sheet;

[0173] Among them, the compaction density of roller pressing is 1.58g / cm 3 .

[0174] Performance Testing

[0175] The preparation method of the positive electrode sheet includes: dissolving lithium iron phosphate: SP: PVDF in NMP in a ratio of 96.6:1.4:2, stirring and mixing to obtain a positive electrode slurry, and coating, rolling, die-cutting, and cutting to obtain a positive electrode sheet;

[0176] The positive electrode sheets prepared above and the negative electrode sheets prepared in Examples 1-5 and Comparative Examples 1-3 are wound or stacked to obtain bare cells. For bare cells that need to be made into three electrodes, the treated copper wire is buried inside the cell before hot pressing and led out from the injection hole. Before hot pressing, the treated copper wire is placed between the positive and negative electrode sheets, separated by a diaphragm in the middle, led out from the explosion-proof valve, and welded on the pole ears. The bare cells without buried copper wire and buried copper wire are all subjected to shell welding, baking, liquid injection (the electrolyte is an electrolyte with a lithium salt concentration in the range of 1 to 1.2 mol / L, where EC:EMC:DMC=1:1.3:1), formation and capacity separation to obtain conventional finished batteries and three-electrode batteries. The conventional batteries of each implementation case were subjected to cycle and rate charge and discharge tests, and the results are shown in Table 1.

[0177] The test method is as follows:

[0178] Cyclic performance test: calculate the capacity retention rate of 1C / 1C cycle for 1000 cycles at 25°C;

[0179] Rate performance test: Calculate the ratio of the capacity of 1C charging and 2.5C discharging to the capacity of 1C charging and 1C discharging.

[0180] Performance data

[0181] Table 1

[0182] Serial number Capacity retention rate after 1000 cycles 2.5C / 1C discharge capacity retention rate Example 1 95.5％ 94.6％ Example 2 95.7％ 94.7％ Example 3 95.8％ 94.8％ Example 4 89.5％ 94.8％ Example 5 87.0％ 93.0％ Comparative Example 1 86.1％ 84.8％ Comparative Example 2 79.5％ 82.5％ Comparative Example 3 95.1％ 94.5％

[0183] It can be seen from the data in Table 1 that the battery in the embodiment of the present invention has good cycle performance and rate performance. By comparing Examples 1-5 with Example 1, it can be seen that when the pore former is added, the porosity on the negative electrode plate increases, more electrolyte can be absorbed, the infiltration effect of the electrolyte is improved, the capacity retention rate of the battery for 1000 weeks is significantly improved, and the discharge capacity retention rate of 2.5C is significantly improved compared to 1C. By comparing Examples 1-5 with Example 2, it can be seen that when there are more pore formers and more pores are left on the pole piece, the performance improvement is not obvious. This is because the more pores lead to a reduction in active substances and the overall liquid absorption capacity becomes worse, thereby affecting the performance. By comparing Examples 1-5 with Example 3, it can be seen that since Example 3 directly dissolves the pore former in the negative electrode active slurry and then coats it on the copper foil, since the coating slurry needs to be stirred and dispersed at high speed, it is difficult to ensure that the pore former in the coating slurry can form straight holes after coating, thereby affecting the performance of the battery.

[0184] After lithium plating, the three-electrode battery is subjected to lithium deposition window test, such as Figure 3As shown in the figure, it can be seen that under the same SOC state, Example 3 can support the largest charging rate, which is significantly better than Comparative Example 1 without adding pore former; the difference between Example 1 and Example 2 is whether the pore former is sprayed on the copper foil or on the copper foil coated with the negative electrode slurry. Because it is directly coated on the copper foil, during the tape running process, the position of the pore former may cause the uniformity to be relatively reduced as the copper foil migrates, while spraying it on the copper foil coated with the negative electrode slurry can reduce the risk of migration, and the slurry can have a certain adsorption capacity for the pore former, which can ensure the uniformity of the dispersion of the pore former. Therefore, the charging rate that Example 2 can support under the same SOC is higher than that of Example 1.

[0185] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultra-fast charging plate, characterized in that: The pole piece includes a current collector and coating layers on both sides of the current collector; The coating layer is provided with straight holes, and the straight holes are formed by spraying a pore-forming agent when the current collector is unrolled and / or spraying a pore-forming agent before the current collector coated with the slurry enters the oven; The added amount of the pore-forming agent on the single-side current collector is 0.001% to 0.01% of the total mass of the slurry coated on the single-side current collector.

2. The ultra-fast charging plate according to claim 1, characterized in that: The volume of the straight holes accounts for 1 / 100000 to 1 / 10000 of the coating volume; And / or, the straight hole has a depth of 4-50 μm; And / or, the straight hole has an aperture of 0.1-500 nm.

3. The ultra-fast charging plate according to claim 1, characterized in that: The pore-forming agent includes one or more of lithium chloride, ammonium bicarbonate, elemental iodine, ferric chloride or methyl methacrylate; And / or, the particle size of the pore former is 2-50 μm.

4. The ultra-fast charging plate according to claim 1, characterized in that: The current collector is copper foil; And / or, the coating layers on both sides of the current collector have a thickness of 10-100 μm.

5. The ultra-fast charging plate according to claim 1, characterized in that: The coating slurry of the coating layer includes: a conductive agent, a binder and an active material.

6. The ultra-fast charging plate according to claim 5, characterized in that: The conductive agent includes one or more of conductive carbon black SP, carbon nanotubes CNT or acetylene black; and / or, the active material comprises one or more of artificial graphite, natural graphite, silicon-oxygen or silicon-carbon materials; And / or, the binder includes at least one of polyacrylic acid, sodium carboxymethyl cellulose and styrene-butadiene rubber.

7. A method for preparing an ultra-fast charging plate according to any one of claims 1 to 6, characterized in that: The steps include: S1: mixing active materials, conductive agents and binders to obtain active slurry; S2: coating the active slurry on the current collector, spraying a pore-forming agent on the current collector coated with the slurry, and then performing air drying to form straight holes in the coating layer formed by the active slurry; Alternatively, a pore-forming agent is sprayed on the current collector, and then the active slurry is coated on the current collector, and air-dried, so that the coating layer formed by the active slurry forms straight pores; S3: The electrode with straight holes is rolled, die-cut and slit to obtain an ultra-fast charging electrode.

8. The method for preparing the ultra-fast charging plate according to claim 7, characterized in that: The mass ratio of the active material, the conductive agent and the binder is (94-96): (0.5-1.5): (2-4.5); and / or, the viscosity of the active slurry is 2000 to 15000 cps; And / or, the solid content of the active slurry is 48%-54%; And / or, the surface density of the slurry coated on the current collector is 170-200 g / m 2 ; and / or, the coating speed of the active slurry on the current collector is ≤20 m / min; And / or, the temperature of the blast drying is 50-110° C., and the wind frequency of the blast drying is 15-45 Hz; And / or, the compaction density of the roller is 0.5 to 1.8 g / cm 3 ; And / or, in step S2, the pore-forming agent is sprayed by a dry powder spraying device.

9. A battery cell, characterized in that: It includes an ultra-fast charging pole piece made by the method for preparing an ultra-fast charging pole piece as described in any one of claims 7-8 or an ultra-fast charging pole piece as described in any one of claims 1-6.

10. A lithium ion battery, characterized in that: The lithium-ion battery contains an ultra-fast charging electrode sheet prepared by the method for preparing an ultra-fast charging electrode sheet as described in any one of claims 7-8 or an ultra-fast charging electrode sheet as described in any one of claims 1-6 or a battery cell as described in claim 9.

Images