A Lithium-Ion Battery Separator with a Lithium-Complementary Coating and Its Preparation Method

Abstract

The present invention discloses a lithium-ion battery separator with a lithium supplement coating and a preparation method thereof. The separator includes a base film, and a lithium supplement layer with a lithium supplement material is coated on the base film. The lithium supplement layer consists of halloysite nanotubes with adsorption properties and shear isotropy and a metal compound lithium salt. In the present invention, the lithium supplement layer can slowly release lithium ions in the lithium salt through the halloysite nanotubes, improve the specific capacity of the cathode material, increase the lithium ion transmission rate, improve the initial efficiency and cycle performance of the battery, effectively improve the film-forming quality of the SEI film. On the other hand, the excellent physical properties of the halloysite coating can enhance the mechanical properties of the separator, improve the heat resistance of the separator, effectively enhance the safety performance of the lithium battery, and at the same time improve the cycle life of the battery.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery separator materials, and particularly relates to a lithium-ion battery separator with a lithium compensation coating and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, high rated voltage, long cycle life, etc., and are widely used in fields such as portable electronic products, new energy vehicles, and power communication energy storage.

[0003] The initial Coulombic efficiency of a lithium-ion battery is an important factor affecting battery performance. During the first charge and discharge process of a lithium-ion battery, as Li + is deintercalated, a passivation layer of a solid electrolyte interface membrane (SEI film) is formed by the reaction of the negative electrode sheet and the electrolyte at the solid-liquid interface. This passivation layer has the characteristics of a solid electrolyte, is an insulating layer for electrons, and at the same time is a good conductor for lithium ions. Since the formation of the SEI film consumes some lithium from the positive electrode, resulting in the loss of lithium in the positive electrode material, the battery capacity is reduced, and the initial efficiency is decreased. At the same time, as the lithium-ion battery cycles, the SEI film will repeat the consumption and repair process, and there will be irreversible lithium consumption to varying degrees inside the positive and negative electrodes, resulting in capacity loss and reducing the cycle life of the battery.

[0004] Secondly, in a lithium-ion battery, the separator mainly plays a role in preventing the positive and negative electrodes from contacting and allowing lithium ions to conduct. Currently, commonly used polyolefin separators will exhibit thermal shrinkage at high temperatures, resulting in deformation of the separator and contact between the positive and negative electrodes, thereby triggering a short circuit and causing an explosion.

[0005] Therefore, providing a lithium-ion separator that can not only improve the initial charge and discharge efficiency of a lithium-ion battery, extend the charge and discharge cycle life of the battery, but also reduce the thermal shrinkage rate of the separator and improve the safety of the battery is a problem to be solved in this technical field.

[0006] A preparation method of a lithium compensation composite separator disclosed in CN110571391A is to place the coating layer facing the positive electrode sheet and the lithium compensation layer facing the negative electrode sheet. During the first charge, lithium ions of the inorganic lithium salt in the lithium compensation layer are deposited on the surface of the negative electrode to form an SEI film. The coating layer and the electrode sheet are in close contact under the shaping action, which can effectively improve the stability of the SEI film, the initial charge and discharge efficiency, and the cycle performance of the battery cell. However, the coating layer will increase the internal resistance of the battery, and at the same time, as the battery cycles, the dissolution of lithium in the lithium coating layer and the heat resistance of the separator are not improved, which will cause safety problems.

[0007] A lithium-rich lithium-ion battery separator disclosed in CN209515825U mentions that a lithium compound and ceramic powder are mixed in an organic solvent and then coated on a base film to prepare a lithium-rich separator, and the lithium compensation amount is adjusted by changing the coating thickness to achieve the lithium compensation effect.

[0008] A lithium battery separator with a lithium supplement coating and its preparation method provided by CN109755448A, which includes coating a lithium compound, nano-inert inorganic particles, a binder, and an organic solvent on the separator, can not only achieve the effect of lithium supplementation but also improve the battery safety.

[0009] Although the above two patent methods can play a role in lithium supplementation, the use of organic solvents is not environmentally friendly. At the same time, when an inorganic lithium compound is mixed and coated with ceramic powder on the base film, the ceramic powder will fall off as the lithium compound dissolves, and safety problems are likely to occur in subsequent cycles. Summary of the Invention

[0010] In order to solve the problems existing in the prior art, the present invention provides a lithium-ion battery separator with a lithium supplement coating and its preparation method.

[0011] The lithium-ion battery separator with a lithium supplement coating provided by the present invention includes a separator base film and a lithium supplement coating provided on at least one side of the separator base film; the composition raw materials of the lithium supplement coating include: an inorganic lithium-containing compound and halloysite nanotube powder; wherein, the inorganic lithium-containing compound serves as a lithium ion source and can provide lithium ions, and the halloysite nanotube powder serves as an inorganic filler.

[0012] Further, the inorganic lithium-containing compound is one or a mixture of two of lithium borate, lithium metaborate, lithium tetraborate, lithium bis(oxalato)borate, lithium carbonate, and lithium bicarbonate, preferably lithium tetraborate;

[0013] Further, the D50 particle size of the halloysite nanotube powder is 0.5 - 40 μm; preferably 1 - 10 μm.

[0014] The lithium supplement coating can be designed as single-sided or double-sided. Among them, the thickness of the single-sided coating can be 0.5 - 5 μm (specifically, such as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm), and the thickness of the double-sided coating can be 1 - 10 μm. The coating thickness is limited here considering the lithium supplementation effect and that the separator thickness does not affect the cell thickness and thus does not affect the normal cell capacity.

[0015] The material of the separator base film is one or a mixture of two or more of polyethylene, polypropylene, non-woven fabric, polyimide, and aramid; preferably, the separator base film is selected from any one of polyethylene (PE) separators and polypropylene (PP) separators;

[0016] The thickness of the separator base film is 5 - 20 μm, preferably 10 - 16 μm;

[0017] The porosity range of the separator base film is 30% - 70%, preferably 40% - 60%;

[0018] The pore size range of the diaphragm base film is 0.005 - 0.2 μm, preferably 0.01 - 0.15 μm.

[0019] Furthermore, the composition raw materials of the lithium supplement coating further include a binder.

[0020] The binder is selected from at least one of polyacrylic acid, polyacrylamide, styrene-butadiene copolymer, ethylene oxide, propylene oxide, sodium carboxymethyl cellulose, sodium carboxyethyl cellulose, nitrile rubber, styrene-butadiene rubber, and polyvinyl alcohol; preferably, the binder is selected from one or more of polyacrylic acid, ethylene oxide, nitrile rubber, styrene-butadiene rubber, and polyvinyl alcohol; more preferably, the binder is composed of polyacrylic acid and ethylene oxide, and the mass ratio of the two is 3:2.

[0021] Furthermore, the mass percentages of each raw material in the preparation slurry of the lithium supplement coating are as follows: 5% - 10% of inorganic lithium-containing compound, 5% - 10% of halloysite nanotube powder, 5% - 10% of binder, and the balance is deionized water.

[0022] The halloysite nanotube powder described in the present invention is halloysite nanotubes after high-speed dispersion and shearing treatment.

[0023] The specific preparation method is as follows: Halloysite nanotube raw powder with 1 μm ≤ D50 ≤ 10 μm (purchased from Jiangsu Xianfeng Nano, brand XFI50, pipe diameter: 50 - 300 nm) is added with deionized water to prepare a slurry with a solid content of 50%, and is sheared and dispersed by a high-speed dispersion shearing machine. The dispersed slurry is passed through a 280-mesh sieve to remove the remaining materials in the sieve. The filtered slurry is allowed to stand for 4 h, and then the upper suspension is taken for centrifugal separation. The precipitate is dried at 80° for 12 h, taken out, and dispersed by a pulverizer for standby;

[0024] Weigh 100 g of the dispersed powder, add 500 g of deionized water and stir into a suspension, add 0.5% of sodium hexametaphosphate (relative to the mass of the halloysite solid powder), adjust the pH value to 8 - 9, and mechanically stir for 2 h. Centrifuge at a speed of 1000 r / min for 5 min, take the upper suspension and centrifuge at a speed of 3000 r / min for 5 min. The obtained precipitate is baked at 80°C for 12 h, taken out, and dispersed by a pulverizer for standby.

[0025] The present invention also provides a preparation method of the above lithium-ion battery separator with a lithium supplement coating, including the following steps:

[0026] Preparation of halloysite nanotube coating slurry

[0027] (1) Preparation of lithium supplement coating slurry: Mix the inorganic lithium-containing compound, halloysite nanotube powder, binder, and solvent in proportion to obtain the lithium supplement coating slurry;

[0028] (2) Coating the lithium supplement coating slurry on one or both sides of the base film and drying it can obtain the lithium-ion battery separator with the lithium supplement coating.

[0029] Aiming at the deficiencies of the prior art, the present invention provides a lithium supplement coating with a slow-release effect on at least one side of the separator. The lithium source is an inorganic lithium-containing compound, and halloysite nanotube powder is used to adsorb the inorganic lithium-containing compound to provide a stable lithium source for the battery during use. During the first charge and discharge process, the inorganic lithium-containing compound gradually dissolves in the electrolyte in the halloysite nanotubes in the coating to release lithium ions, supplementing the consumption of lithium ions during the formation of the SEI film; at the same time, the SEI film on the negative electrode surface is quickly formed and reaches a stable state, improving the quality of the SEI film, maintaining the concentration of lithium salt in the electrolyte, and increasing the cycle life of the battery.

[0030] The halloysite nanotube powder used in the present invention has good physical and mechanical properties and heat resistance, with a decomposition temperature higher than 200°C. Halloysite nanotubes can reduce the thermal shrinkage of the separator, effectively reduce the internal short circuit of the lithium-ion battery, prevent the thermal runaway of the battery caused by the internal short circuit triggered by lithium dendrites, improve the safety of the battery, and slowly release and supplement lithium ions to extend the battery cycle life.

[0031] In the lithium compound coating of the present invention, the carrier of the inorganic lithium-containing compound is halloysite nanotube powder, which has hydroxyl and siloxane groups on the surface, has good hydrophilicity, can use deionized water as the slurry solvent, is safe, environmentally friendly and energy-saving, avoids the influence of the harsh production conditions of traditional lithium supplement methods on large-scale production, has a simple and convenient process, is friendly to the production environment, and is easy to achieve mass production.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] 1) The halloysite nanotube powder added to the lithium supplement coating of the present invention is a natural nano-tubular structure silicate. Structurally composed of a dioctahedral type of 1:1 unit layer, it has a large number of pores and a large specific surface area. The inner diameter of the tube is 15 - 300 nm, and the tube length is generally 0.5 - 40 μm. Its chemical formula is AL2SiO5(OH)4. The inner wall is an Al2O3 structure, the outer wall is SiO2, and the surface contains a large number of hydroxyl and siloxy groups, with a highly negatively charged outer surface, making it a good natural adsorption material. It can be evenly dispersed in deionized water, and at the same time adsorb inorganic lithium compounds in the halloysite nanotubes. During the first charge and discharge process of the lithium battery, the halloysite nanotubes have a slow-release effect, and the inorganic lithium compounds adsorbed in the halloysite nanotubes gradually dissolve and release lithium ions, supplementing the lithium ions lost in the formation of the SEI film on the negative electrode and improving the first charge and discharge efficiency of the lithium-ion battery.

[0034] 2) The halloysite nanotube powder added in the lithium supplementing coating of the present invention has anisotropy. When the coating is applied to the separator, the halloysite nanotubes will be arranged in the same direction as the coating direction, improving the coating uniformity. At the same time, the halloysite nanotubes have ceramic properties, which can enhance the heat resistance of the lithium-ion battery and reduce the thermal shrinkage of the separator, thereby effectively reducing the thermal runaway of the battery caused by internal short circuit. In addition, the coating has strong physical mechanical properties, which can prevent the piercing of the separator by metallic lithium dendrites and improve the puncture resistance safety of the battery. Description of the Drawings

[0035] Figure 1 Schematic diagram of halloysite nanotubes;

[0036] Figure 2 SEM and TEM images of halloysite nanotubes;

[0037] Figure 3 Schematic diagram of the double-sided coating of the lithium-ion separator with the lithium supplementing coating;

[0038] Figure 4 Schematic diagram of the single-sided coating of the lithium-ion separator with the lithium supplementing coating;

[0039] Figure 5 SEM images of the halloysite nanotube lithium supplementing coating prepared with sheared halloysite nanotubes and the halloysite nanotube lithium supplementing coating prepared with unsheared halloysite nanotubes;

[0040] Among them, A is the separator base film, B is the lithium supplementing coating, C is the halloysite nanotube powder, and D is the binder. Detailed Embodiments

[0041] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. The methods are all conventional methods unless otherwise specified. The raw materials can all be obtained from public commercial channels unless otherwise specified.

[0042] The preparation method of the halloysite nanotubes used in the following embodiments is as follows:

[0043] Purification of halloysite nanotubes: Halloysite nanotube raw powder with 1μm ≤ D50 ≤ 10μm (purchased from Jiangsu Xianfeng Nano, brand XFI50, tube diameter: 50 - 300nm) is mixed with deionized water to prepare a slurry with a solid content of 50%. It is sheared and dispersed with a high-speed dispersion shear machine. The dispersed slurry is passed through a 280-mesh sieve to remove the remaining materials in the sieve. The filtered slurry is left standing for 4h, and then the upper suspension is taken for centrifugal separation. The precipitate is dried at 80° for 12h, taken out and dispersed with a pulverizer for standby.

[0044] Weigh 100 g of the pulverized powder after dispersion, add 500 g of deionized water, stir to form a suspension, add 0.5% of sodium hexametaphosphate (relative to the mass of halloysite solid powder), adjust the pH value to 8 - 9, and mechanically stir for 2 h. Centrifuge at a speed of 1000 r / min for 5 min, take the upper suspension, and then centrifuge at a speed of 3000 r / min for 5 min. Take out the obtained precipitate after baking at 80 °C for 12 h, disperse it, and set it aside for use. The particle size length observed by SEM is 8 μm.

[0045] Example 1

[0046] A lithium-ion separator slurry with a lithium supplementing coating, the ratio according to mass ratio includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 10:10:5:75 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0047] The base film uses a 12-μm polyethylene (PE) film, the porosity is 50%, and the pore size range is 0.005 - 0.2 μm. Among them, the coating thickness of the lithium supplementing coating on one side of the base film is 3 μm.

[0048] The specific preparation method of the lithium-ion separator with a lithium supplementing coating is as follows:

[0049] (1) First, stir and blend 10 parts of halloysite nanotube powder and 10 parts of lithium tetraborate powder for 30 min, add 2 parts of ethylene oxide and 60 parts of deionized water, stir and mix well for 90 min, then add 3 parts of polyacrylic acid and continue to stir for 30 min. Finally, add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplementing coating slurry.

[0050] (2) Uniformly coat the prepared lithium supplementing slurry on the surface of the PE base film by the microgravure coating method. After coating, perform drying treatment to prepare a lithium-ion separator with a lithium supplementing coating, and the coating thickness is 3 μm.

[0051] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium supplementing separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0052] Example 2

[0053] A lithium-ion separator slurry with a lithium supplementing coating, the ratio according to mass ratio includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 8:10:5:77 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0054] The base film uses a 12-μm polyethylene (PE) film, the porosity is 50%, and the pore size range is 0.005 - 0.2 μm. Among them, the coating thickness of the lithium supplementing coating on one side of the base film is 3 μm.

[0055] The specific preparation method of the lithium - supplemented coating lithium - ion separator is as follows:

[0056] (1) First, 8 parts of halloysite nanotube powder and 10 parts of lithium tetraborate powder are stirred and blended for 30 min. Then, 2 parts of ethylene oxide and 62 parts of deionized water are added and stirred and mixed thoroughly for 90 min. Next, 3 parts of polyacrylic acid are added and stirred for another 30 min. Finally, 15 parts of deionized water are added and stirred for 30 min to obtain a uniform lithium - supplemented coating slurry.

[0057] (2) The prepared lithium - supplemented slurry is evenly coated on the surface of the PE base film by micro - gravure coating. After coating, drying treatment is carried out to prepare a lithium - ion separator with a lithium - supplemented coating, and the coating thickness is 3 μm.

[0058] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium - supplemented separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0059] Example 3

[0060] A lithium - ion separator slurry with a lithium - supplemented coating, the ratio by mass includes halloysite nanotube: lithium tetraborate powder: adhesive: deionized water = 6:10:5:79 (the adhesive is polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0061] The base film uses a 12 - μm polyethylene (PE) film, the porosity is 50%, the pore size range is 0.005 - 0.2 μm, and the coating thickness of the lithium - supplemented coating on one side of the base film is 3 μm.

[0062] The specific preparation method of the lithium - supplemented coating lithium - ion separator is as follows:

[0063] (1) First, 6 parts of halloysite nanotube powder and 10 parts of lithium tetraborate powder are stirred and blended for 30 min. Then, 2 parts of ethylene oxide and 64 parts of deionized water are added and stirred and mixed thoroughly for 90 min. Next, 3 parts of polyacrylic acid are added and stirred for another 30 min. Finally, 15 parts of deionized water are added and stirred for 30 min to obtain a uniform lithium - supplemented coating slurry.

[0064] (2) The prepared lithium - supplemented slurry is evenly coated on the surface of the PE base film by micro - gravure coating. After coating, drying treatment is carried out to prepare a lithium - ion separator with a lithium - supplemented coating, and the coating thickness is 3 μm.

[0065] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium - supplemented separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0066] Example 4

[0067] A lithium-ion separator slurry with a lithium supplement coating, the proportion by mass ratio includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:8:5:81 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2).

[0068] The base film uses a 12μm polyethylene (PE) film, with a porosity of 50%, and the pore size range is 0.005 - 0.2μm. Among them, the coating thickness of the lithium supplement coating on one side of the base film is 3μm.

[0069] The specific preparation method of the lithium-ion separator with a lithium supplement coating is as follows:

[0070] (1) First, stir and blend 6 parts of halloysite nanotube powder and 8 parts of lithium tetraborate powder for 30 min, add 2 parts of ethylene oxide and 66 parts of deionized water, stir and mix well for 90 min, then add 3 parts of polyacrylic acid and continue to stir for 30 min. Finally, add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplement coating slurry.

[0071] (2) Uniformly coat the prepared lithium supplement slurry on the surface of the PE base film by the microgravure coating method. After coating, perform a drying treatment to prepare a lithium-ion separator with a lithium supplement coating, and the coating thickness is 3μm.

[0072] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium supplement separator prepared by the above method. Among them, the positive electrode is lithium nickel cobalt manganate, the negative electrode is graphite, and the electrolyte is LiPF6.

[0073] Example 5

[0074] A lithium-ion separator slurry with a lithium supplement coating, the proportion by mass ratio includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:6:5:83 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2).

[0075] The base film uses a 12μm polyethylene (PE) film, with a porosity of 50%, and the pore size range is 0.005 - 0.2μm. Among them, the coating thickness of the lithium supplement coating on one side of the base film is 3μm.

[0076] The specific preparation method of the lithium-ion separator with a lithium supplement coating is as follows:

[0077] (1) First, stir and blend 6 parts of halloysite nanotube powder and 6 parts of lithium tetraborate powder for 30 min, add 2 parts of ethylene oxide and 68 parts of deionized water, stir and mix well for 90 min, then add 3 parts of polyacrylic acid and continue to stir for 30 min. Finally, add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplement coating slurry.

[0078] (2) The prepared lithium - supplement slurry is evenly coated on the surface of the PE base film by micro - concave coating. After coating, it is dried to prepare a lithium - ion separator with a lithium - supplement coating, and the coating thickness is 3 μm.

[0079] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium - supplement separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0080] Example 6

[0081] A lithium - ion separator slurry with a lithium - supplement coating, the ratio by mass includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:5:5:84 (the adhesive is polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0082] The base film uses a 12 - μm polyethylene (PE) film, with a porosity of 50%, and the pore size range is 0.005 - 0.2 μm. Among them, the coating thickness of the lithium - supplement coating on one side of the base film is 3 μm.

[0083] The specific preparation method of the lithium - ion separator with a lithium - supplement coating is as follows:

[0084] (1) First, 6 parts of halloysite nanotube powder and 5 parts of lithium tetraborate powder are stirred and blended for 30 min, 2 parts of ethylene oxide and 69 parts of deionized water are added and stirred and mixed thoroughly for 90 min, then 3 parts of polyacrylic acid are added and stirred for 30 min, and finally 15 parts of deionized water are added and stirred for 30 min to obtain a uniform lithium - supplement coating slurry;

[0085] (2) The prepared lithium - supplement slurry is evenly coated on the surface of the PE base film by micro - concave coating. After coating, it is dried to prepare a lithium - ion separator with a lithium - supplement coating, and the coating thickness is 3 μm.

[0086] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium - supplement separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0087] Example 7

[0088] A lithium - ion separator slurry with a lithium - supplement coating, the ratio by mass includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:8:5:81 (the adhesive is polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0089] The base film uses a 12-μm polyethylene (PE) film with a porosity of 50% and a pore size range of 0.005 - 0.2 μm. Among them, the coating thickness of the lithium supplement coating on one side of the base film is 2 μm.

[0090] The specific preparation method of the lithium-ion separator with a lithium supplement coating is as follows:

[0091] (1) First, stir and blend 6 parts of halloysite nanotube powder and 8 parts of lithium tetraborate powder for 30 min, add 2 parts of ethylene oxide and 66 parts of deionized water, stir and mix well for 90 min, then add 3 parts of polyacrylic acid and continue to stir for 30 min. Finally, add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplement coating slurry.

[0092] (2) Uniformly coat the prepared lithium supplement slurry on the surface of the PE base film by the microgravure coating method. After coating, perform a drying treatment to prepare a lithium-ion separator with a lithium supplement coating, and the coating thickness is 2 μm.

[0093] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium supplement separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0094] Example 8

[0095] A lithium-ion separator slurry with a lithium supplement coating, the ratio according to the mass ratio includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:8:5:81 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0096] The base film uses a 12-μm polyethylene (PE) film with a porosity of 50% and a coating porosity of 40%, and the pore size range is 0.005 - 0.2 μm. Among them, the coating thickness of the lithium supplement coating on one side of the base film is 4 μm.

[0097] The specific preparation method of the lithium-ion separator with a lithium supplement coating is as follows:

[0098] (1) First, stir and blend 6 parts of halloysite nanotube powder and 8 parts of lithium tetraborate powder for 30 min, add 2 parts of ethylene oxide and 66 parts of deionized water, stir and mix well for 90 min, then add 3 parts of polyacrylic acid and continue to stir for 30 min. Finally, add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplement coating slurry.

[0099] (2) Uniformly coat the prepared lithium supplement slurry on the surface of the PE base film by the microgravure coating method. After coating, perform a drying treatment to prepare a lithium-ion separator with a lithium supplement coating, and the coating thickness is 4 μm.

[0100] A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and a lithium supplement diaphragm prepared by the above method. The positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0101] Example 9

[0102] A lithium-ion diaphragm slurry with a lithium supplement coating, the ratio by mass includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:8:5:81 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0103] The base film uses a 12μm polyethylene (PE) film, the porosity is 50%, the porosity of the coating is 40%, and the pore size range is 0.005 - 0.2μm. Among them, the coating thickness of the lithium supplement coating on one side of the base film is 1.5μm.

[0104] The specific preparation method is as follows:

[0105] (1) First, stir and blend halloysite nanotube powder and lithium tetraborate powder for 30 min, add ethylene oxide and 66 parts of deionized water, stir and mix well for 90 min, then add polyacrylic acid and continue to stir for 30 min, and finally add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplement coating slurry.

[0106] (2) Uniformly coat the prepared lithium supplement slurry on the surface of the PE base film by the microgravure coating method. After coating, perform a drying treatment to prepare a lithium-ion diaphragm with a lithium supplement coating, and the coating thickness is 1.5μm.

[0107] (3) A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and a lithium supplement diaphragm prepared by the above method. The positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0108] Example 10

[0109] A lithium-ion diaphragm slurry with a lithium supplement coating, the ratio by mass includes halloysite nanotubes: lithium tetraborate powder: adhesive: deionized water = 6:8:5:81 (the adhesive is selected from polyacrylic acid and ethylene oxide, and the mass ratio of polyacrylic acid to ethylene oxide is 3:2)

[0110] The base film uses a 12μm polyethylene (PE) film, the porosity is 50%, the pore size range is 0.005 - 0.2μm. Among them, the coating thickness of the lithium supplement coating on both sides of the base film is 6μm.

[0111] The specific preparation method is as follows:

[0112] (1) First, stir and blend halloysite nanotube powder and lithium tetraborate powder for 30 min, add ethylene oxide and 66 parts of deionized water, stir and mix well for 90 min, then add polyacrylic acid and continue to stir for 30 min. Finally, add 15 parts of deionized water and stir for 30 min to obtain a uniform lithium supplement coating slurry.

[0113] (2) Uniformly coat the prepared lithium supplement slurry on the surface of the PE base film by microgravure coating method. After coating, perform drying treatment to prepare a lithium-ion separator with a lithium supplement coating, and the double-sided coating thickness is 6 μm.

[0114] (3) A lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the lithium supplement separator prepared by the above method, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0115] Comparative Example 1

[0116] This comparative example is an experimental control group. A lithium battery is assembled with a PE base film with a thickness of 14 μm, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0117] Comparative Example 2

[0118] This comparative example is an experimental control group. A single-sided ceramic separator is selected, where the PE base film has a thickness of 12 μm and the ceramic layer has a thickness of 3 μm to assemble a lithium battery, where the positive electrode is lithium nickel cobalt manganese oxide, the negative electrode is graphite, and the electrolyte is LiPF6.

[0119] The high-temperature resistance performance of the lithium supplement separators prepared in Examples 1-10 and Comparative Examples 1-2 and the corresponding battery performances are shown in the following table.

[0120]

[0121]

[0122] As can be seen from the above table, the lithium supplement separator has a small thermal shrinkage rate at 130 °C / 1 h and has good heat resistance. The initial efficiency of the lithium battery prepared with this lithium supplement separator is greater than 92%, and the capacity retention rate can be maintained above 98% after 200-250 cycles, showing good cycling performance.

Claims

1. A lithium - supplementing coating - provided lithium - ion battery separator, comprising a separator base film and a lithium - supplementing coating provided on at least one side of the separator base film; the composition raw materials of the lithium - supplementing coating include: Inorganic lithium-containing compound and halloysite nanotube powder; The composition raw materials of the lithium supplement coating further include a binder; The mass percentages of the raw materials in the preparation slurry of the lithium supplement coating are as follows: inorganic lithium-containing compound 5%-10%, halloysite nanotube powder 5%-10%, binder 5%-10%, and the balance is deionized water; The inorganic lithium-containing compound is one or a mixture of two of lithium borate, lithium metaborate, lithium tetraborate, lithium bis(oxalato)borate, lithium carbonate, and lithium bicarbonate; The D50 particle size of the halloysite nanotube powder is 0.5 - 40 ; Or, the halloysite nanotube powder is halloysite nanotubes after high-speed dispersion and shearing treatment.

2. The lithium-ion battery separator with a lithium compensation coating according to claim 1, characterized in that: The lithium supplementing coating is single-sided or double-sided. Among them, the thickness of the single-sided coating is 0.5 - 5 , and the thickness of the double-sided coating is 1 - 10 .

3. The lithium-ion battery separator with a lithium compensation coating according to claim 1, characterized in that: The material of the separator base film is one or a mixture of two or more of polyethylene, polypropylene, non-woven fabric, polyimide, and aramid.

4. The lithium-ion battery separator with a lithium compensation coating according to claim 3, wherein: The thickness of the diaphragm base film is 5-20 , the porosity range of the diaphragm base film is 30%-70%, and the pore size range of the diaphragm base film is 0.005-0.2 .

5. The lithium-ion battery separator with a lithium compensation coating according to claim 1, characterized in that: The binder is selected from at least one of polyacrylonitrile, polyacrylamide, styrene-butadiene copolymer, ethylene oxide, propylene oxide, carboxymethyl cellulose, carboxyethyl cellulose, nitrile rubber, styrene-butadiene rubber, and polyvinyl alcohol.

6. The method for preparing a lithium-ion battery separator with a lithium supplement coating according to claim 1, comprising the following steps: (1) Mix an inorganic lithium-containing compound, halloysite nanotube powder, binder, and solvent in proportion to obtain a lithium supplement coating slurry; (2) Coat the lithium supplement coating slurry on one or both sides of the separator base film, and after drying, the lithium-ion battery separator with a lithium supplement coating is obtained.

Images