CN111697270A - Method for forming negative electrode protection layer through in-situ transfer - Google Patents

Abstract

The present invention provides a method for forming a negative electrode protective layer by in-situ transfer. The method can coat the initial raw material of the negative electrode protective layer as a coating on a separator, and after the battery is assembled, the coating on the separator is transferred by reaction to the surface of the negative electrode of the lithium ion battery to form a protective layer. The initial raw material forms a coating on the separator, the preparation process is simple, and the preparation conditions are relaxed. The reaction occurs inside the cell and is transferred to the surface of the negative electrode through the reaction, without additional control of water and oxygen conditions. The protective layer and the surface of the negative electrode form a whole due to the reaction, and the interface impedance between the protective layer and the negative electrode decreases, which is beneficial to improve the cycle life of the corresponding battery. The protective layer on the surface of the negative electrode can effectively affect the lithium deposition behavior during the cycle process, which is beneficial to improve the stability of the corresponding negative electrode and the safety of the battery.

Description

A method of forming a negative electrode protective layer by in-situ transfer

technical field

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for forming a negative electrode protective layer by in-situ transfer.

Background technique

Lithium-ion batteries have many advantages such as high specific capacity, long cycle life, and environmental protection. They are one of the main representatives of high-performance secondary batteries. Now they have been widely used in various electronic devices, electric or hybrid vehicles, aerospace, etc. different area. Among them, lithium-ion batteries are mainly composed of four parts: positive electrode, negative electrode, separator and electrolyte. At present, carbon negative electrode is mostly used as negative electrode material, and its theoretical specific capacity is relatively low (372mAh/g), which is difficult to meet the growing demand. Therefore, new anode materials such as silicon carbon electrodes and lithium metal electrodes need to replace carbon materials as new anodes. Among them, the theoretical specific capacity of lithium metal is 3860mAh/g, which is the anode material with the highest specific capacity currently known, so it is expected to become the best anode material for the next generation of lithium batteries. However, the lithium metal anode is prone to form dendritic lithium deposits during cycling, which will pierce the separator and cause a short circuit in the battery, which in turn leads to thermal runaway, and eventually fires or even explodes, posing a safety hazard. In addition, the irregular deposition of lithium ions during the cycling process can easily fall off the surface of the lithium metal electrode and be scattered on the surface of the electrode. The gain and loss of electrons cannot continue to participate in the reaction, becoming dead lithium, and it will also increase the interfacial resistance inside the battery. This will lead to a decrease in the coulombic efficiency of the battery, a decline in the specific capacity, and a reduction in the lifespan. Similarly, silicon carbon anodes also face similar problems. Therefore, how to effectively solve the two major problems of safety, cycle capacity and life of the above-mentioned anodes has become the research object of current researchers.

At present, the research on the negative electrode of lithium ion battery mainly focuses on the following aspects: first, adding effective additives to the battery electrolyte to reasonably improve the deposition behavior of lithium ions on the surface of the negative electrode and assist in the formation of a stable interface layer; second , is to add a coating on the battery separator to increase the resistance of the separator to dendrites and improve the overall safety performance of the battery; the third is to improve the surface or structure of the negative electrode to induce uniform deposition of lithium ions or restrict lithium ions in specific areas. Internal deposition, reducing the generation of dendritic lithium crystals. Among them, since the negative pole piece, especially the lithium metal pole piece is very active and easy to react with water and oxygen, the experimental conditions need to be strictly controlled in the process of modifying the negative pole, which will increase the difficulty of wide application of the corresponding method. In addition, the increased interfacial resistance between the protective layer and the negative electrode is usually a concern of researchers. If the two cannot be effectively contacted, the influence of the protective layer on the lithium ion deposition behavior may be reduced, and the additional interfacial resistance will be increased. It also reduces the cycle performance of the battery.

In addition, the technical means of modifying the separator is relatively mature at present. There are a large number of ceramic-coated polyolefin separators on the market. The main function of the ceramic layer is to improve the thermal shrinkage performance of the separator, thereby improving the safety performance of the battery. When the coating on the separator is assembled in the battery, it is usually in macroscopic contact with the negative electrode, and there is an interface problem between the two, so the coating has relatively little effect on the deposition behavior of lithium ions on the negative electrode.

SUMMARY OF THE INVENTION

In order to improve the deficiencies of the prior art, a first aspect of the present invention is to provide a method for preparing a lithium ion battery negative electrode protective layer by in-situ transfer, the method comprising:

Contact the separator coated with the coating with the negative electrode of the lithium ion battery, and react to obtain a protective layer on the surface of the negative electrode of the lithium ion battery; the reaction includes but is not limited to an intercalation reaction and a redox reaction; the reaction is under a certain applied voltage condition. The raw materials for forming the coating include at least one of the following coating materials: phosphates, manganates, carbonates, metal hydroxides, inorganic solid electrolyte materials, inorganic semiconductor materials and materials that can interact with lithium Reacted transition metal oxides.

A second aspect of the present invention is to provide a method for preparing a lithium ion battery, the method comprising the above-mentioned method for preparing a negative electrode protective layer of a lithium ion battery by in-situ transfer.

A third aspect of the present invention is to provide a lithium ion battery prepared by the above-mentioned method for preparing a lithium ion battery.

Beneficial effects of the present invention:

The invention provides a method for preparing a negative electrode protective layer of a lithium ion battery by in-situ transfer. The method can coat the initial raw material of the negative electrode protective layer as a coating on the separator. After the battery is assembled, the protective layer on the separator The coating is transferred to the surface of the negative electrode of the lithium-ion battery through the reaction to form a protective layer. The initial raw material forms a coating on the separator, the preparation process is simple, and the preparation conditions are relaxed. The reaction occurs inside the cell and is transferred to the surface of the negative electrode through the reaction, without additional control of water and oxygen conditions. The protective layer and the surface of the negative electrode form a whole due to the reaction, and the interface impedance between the protective layer and the negative electrode decreases, which is beneficial to improve the cycle life of the corresponding battery. The protective layer on the surface of the negative electrode can effectively affect the lithium deposition behavior during the cycle process, which is beneficial to improve the stability of the corresponding negative electrode and the safety of the battery.

Compared with the modification of the negative electrode in the prior art before the negative electrode is assembled into a battery, the present application completes the modification and modification of the negative electrode after the battery is assembled into a battery. The method of the present application does not need to consider the impact on the negative electrode during the modification process, especially for lithium metal negative electrodes, there is no need to strictly control the water and oxygen content in the preparation process, which greatly reduces the preparation cost and difficulty of preparation.

Description of drawings

FIG. 1 is a scanning electron microscope picture of the coating transfer compound obtained in Example 1 on the surface of the negative electrode.

Detailed ways

As mentioned above, the first aspect of the present invention is to provide a method for preparing a lithium ion battery negative electrode protective layer by in-situ transfer, the method comprising:

Contact the separator coated with the coating with the negative electrode of the lithium ion battery, and react to obtain a protective layer on the surface of the negative electrode of the lithium ion battery; the reaction includes but is not limited to an intercalation reaction and a redox reaction; the reaction is under a certain applied voltage condition. The raw materials for forming the coating include at least one of the following coating materials: phosphates, manganates, carbonates, metal hydroxides, inorganic solid electrolyte materials, inorganic semiconductor materials and materials that can interact with lithium Reacted transition metal oxides.

Taking the intercalation reaction as an example, lithium is intercalated into the coating material in the form of ions to generate a lithium-containing compound, which can form a uniform protective layer on the surface of the negative electrode during the reaction. Exemplarily, lithium in the negative electrode is embedded in the lattice of the coating material in the form of ions to generate a lithium-containing compound, and the compound can form a uniform protective layer on the surface of the negative electrode during the reaction.

Taking the redox reaction as an example, elemental lithium reacts with the coating material to form a corresponding reduction product and a lithium-containing compound. The reduction product and the lithium-containing compound are integrated with the negative electrode and become the protective layer of the negative electrode. Exemplarily, the lithium negative electrode reacts with the coating material to generate a corresponding metal element and a lithium-containing compound, and the metal element and the lithium-containing compound are integrated with the negative electrode to become a protective layer of the negative electrode.

Wherein, the negative electrode is a conventional lithium-ion battery negative electrode known in the art, for example, at least one selected from a carbon negative electrode, a silicon carbon negative electrode, a lithium metal negative electrode, a lithium titanate negative electrode, and the like.

In a specific embodiment, the applied voltage is greater than 0 and less than or equal to 5V, preferably greater than 0 and less than or equal to 3V; the pressing time of the applied voltage is greater than 0 hours, wherein preferably greater than 0 hours and less than or equal to 24 hours. For example, the applied voltage is 0.5V, 1.0V, 1.5V, 2.0V or 2.5V, and the pressing time is 1h, 3h, 5h, 10h, 12h, 18h or 24h.

In a specific embodiment, the transition metal oxide that can react with lithium is selected from one or more of nickel oxide, lead oxide, etc.; the phosphate is selected from one or more of iron phosphate, nickel phosphate, etc. one or more; the manganate is selected from one or more of cobalt manganate, zinc manganate, etc.; the carbonate is selected from one or more of iron carbonate, zinc carbonate, etc.; the The metal hydroxide is selected from one or more of nickel hydroxide, magnesium hydroxide, etc.; the inorganic solid electrolyte material is selected from one or more of lithium fast ion conductor, perovskite, etc.; the The inorganic semiconductor material is selected from one or more of tin oxide, silver sulfide and the like.

Specifically, the coating material is selected from one or more of cobalt manganate, nickel oxide, lead zirconate titanate, zinc carbonate, nickel hydroxide, tin oxide and iron phosphate.

In a specific embodiment, the raw material of the coating further includes a dispersant. The dispersing agent is selected from water and organic agents. The organic reagent is selected from conventional organic solvents known in the art, for example, at least one selected from ethanol, acetone, isopropanol, chloroform and the like.

In a specific embodiment, the raw material of the coating further includes an auxiliary agent. Specifically, the auxiliary agent is selected from at least one of surfactants and dispersing auxiliary agents. Wherein, the surfactant includes dodecylbenzene sulfonate (such as sodium dodecylbenzenesulfonate), dioctyl succinate sulfonate, fatty alcohol polyoxyethylene ether, oleyl alcohol polyoxyethylene ether , one or more of polyoxyethylene fatty acid ester, oleate and stearate. The dispersing aids include polyacrylic acid and its salts, copolymerized poly(acrylic acid-methacrylic acid) and its salts, castor oil, lauryl sulfate, triethylhexylphosphoric acid, methyl amyl alcohol, polyacrylamide , one or more of polyoxyethylene ether and oleic acid amide.

In a specific embodiment, the raw material of the coating further includes a binder. Specifically, the binder includes styrene-butadiene rubber, fluorinated rubber, polyvinyl alcohol, hydroxymethyl cellulose salt, polyacrylic acid, polyacrylate and its derivatives, polyacrylonitrile, acrylate-acrylonitrile copolymer , one or more of polymethyl methacrylate, dimethyldipropenyl ammonium chloride, alginate, pectate, carrageenan and polyvinylidene fluoride.

In a specific embodiment, the method further includes the preparation of the membrane coated with the coating, and the preparation of the membrane includes the steps of:

(1) Dispersing the coating material in a dispersant, optionally adding an auxiliary agent and/or a binder and mixing uniformly, to prepare a mixed slurry of the coating material;

(2) coating the mixed slurry of step (1) on one side surface of the diaphragm base layer;

(3) drying the diaphragm base layer coated with the mixed slurry in step (2), that is, to prepare the coated diaphragm.

In step (1), the mass ratio of the coating material to the dispersant is (0.1-50):100, preferably (0.5-33):100, and also preferably (1-15):100.

In step (1), the mass ratio of the amount of the auxiliary agent to the dispersant is (0.001-20):100, preferably (0.001-10):100, and preferably (0.005-5):100.

In step (1), the mass ratio of the amount of the binder to the dispersant is (0.001-20):100, preferably (0.001-15):100, and preferably (0.005-10):100.

In step (2), the coating is selected from at least one of spray coating, blade coating, coating roller, coating brush and the like.

In step (3), the drying time is 0.01-24h; the drying temperature is 30-80°C.

Wherein, the thickness of the coating is 0.1-10 μm.

Wherein, the coating areal density of the coating is 0.2-5 g/m ² .

As mentioned above, the second aspect of the present invention is to provide a method for preparing a lithium ion battery, the method includes the above-mentioned method for preparing a negative electrode protective layer of a lithium ion battery by in-situ transfer.

In a specific embodiment, the method further includes contacting the positive electrode and the coated separator with the negative electrode of the lithium ion battery, and reacting to obtain a protective layer on the surface of the negative electrode of the lithium ion battery; the reaction includes but is not limited to intercalation. reaction and/or redox reaction; the reaction is carried out under a certain applied voltage condition; the raw material for forming the coating comprises at least one of the following coating materials: phosphate, manganate, carbonate, Metal hydroxides, inorganic solid-state electrolyte materials, inorganic semiconductor materials, and transition metal oxides that can react with lithium.

As mentioned above, the third aspect of the present invention is to provide a lithium ion battery, the lithium ion battery is prepared by the above-mentioned preparation method of a lithium ion battery.

Preferably, the lithium ion battery is at least one of a button battery, a stacked battery, and a wound battery.

Preferably, the outer packaging of the lithium ion battery is a soft plastic packaging or a steel case packaging.

The preparation method of the present invention will be described in further detail below with reference to specific examples. It should be understood that the following examples are only for illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the intended protection scope of the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

In this example, when the prepared lithium-ion battery is subjected to a cyclic charge-discharge test, the lithium-ion battery is subjected to a charge-discharge cycle test at 0.5C, and the 10th cycle, the 100th cycle, the 200th cycle, and the 10th cycle are recorded respectively. Discharge specific capacity at 500 cycles.

In this example, when the appearance of the in-situ transfer of the protective layer of the prepared lithium ion battery was observed, the lithium ion battery was disassembled in a glove box in an argon atmosphere, rinsed with an electrolyte solvent, and dried in the air. , observed with a scanning electron microscope.

Preparation of positive electrode sheet: fully mix 85 parts of positive electrode active material lithium iron phosphate, 5 parts of acetylene black, 5 parts of conductive graphite, and 5 parts of PVDF with N-methylpyrrolidone to obtain a positive electrode slurry, which is uniformly coated on the surface of the aluminum foil current collector to complete Preparation of positive plates.

Preparation of negative electrode sheet: Lithium metal electrode is selected.

Example 1

Step 1) Dissolve 25 g of sodium dodecyl benzene sulfonate in 460 mL of water to obtain a mixed system, then disperse 160 g of nickel oxide in the above mixed system, add 5 g of styrene-butadiene rubber binder, and fully stir to prepare a mixed slurry ;

Step 2) applying the mixed slurry blade of step 1) to one side of the polypropylene diaphragm base layer;

Step 3) Dry the diaphragm base layer coated with the mixed slurry in step 2) in a vacuum drying oven at 40° C. for 2 hours to prepare the diaphragm with the nickel oxide coating; the thickness of the coating is 4 μm.

Step 4) Assemble the Li-ion battery:

Put the nickel oxide diaphragm obtained in step 3) between the positive electrode and the negative electrode plate, orient the coating direction toward the negative electrode side, add 100 μL of commercial lithium-ion battery electrolyte, put in the reed, and seal it with a hydraulic sealer to prepare a button-type 2032 Lithium Ion Battery.

Step 5) Coating in-situ transfer process: energize for 10 hours at a constant voltage of 1.5V, during the energization process, lithium ions are embedded in the nickel oxide lattice in the coating and form a uniform layer, and are in close contact with the negative electrode, that is, in the A protective layer is formed on the surface of the negative electrode.

The prepared lithium-ion batteries were subjected to cyclic charge-discharge tests (see Table 1) and the morphology characterization of the in-situ transfer protective layer (see Figure 1).

FIG. 1 is the characterization of the morphology of the in-situ transfer protective layer in Example 1. It can be seen from the figure that the coating on the separator has been successfully transferred to the lithium metal anode, and the lithium deposition is promoted to be smoother during the cycle.

Example 2

Other steps are the same as in Example 1, the difference is only:

Step 1) Dissolving 15 g of methyl amyl alcohol in 1500 mL of water to obtain a mixed system, then dissolving 145 g of iron phosphate in the above mixed system, adding 14 g of a polyacrylic acid binder and fully stirring to prepare a composite slurry;

Step 5) Coating in-situ transfer process: power on for 10h under a constant voltage of 1.5V, during the power-on process, lithium ions are embedded in the iron phosphate lattice and form compounds such as lithium iron phosphate, which can form a uniform layer and be closely connected to the negative electrode Combined, that is, a protective layer is formed on the surface of the negative electrode.

Example 3

Other steps are the same as in Example 1, the difference is only:

Step 1) Dissolve 15 g of methyl amyl alcohol in 1500 mL of acetone to obtain a mixed system, then disperse 200 g of cobalt manganate in the above mixed system, add 30 g of polyvinylidene fluoride binder and stir to obtain a composite slurry;

Step 5) Coating in-situ transfer process: energize for 5 hours at a constant voltage of 2.5V, during the energization process, the cobalt manganate in the coating undergoes a redox reaction with lithium metal to generate manganese, cobalt metal elemental substance and a small amount of low-valent compounds, It can form a uniform layer and be closely combined with the negative electrode, that is, a protective layer is formed on the surface of the negative electrode.

Example 4

Other steps are the same as in Example 1, the difference is only:

Step 1) Dissolving 35 g of castor oil in 1500 mL of water to obtain a mixed system, then dissolving 300 g of zinc carbonate in the above mixed system, adding 100 g of polyacrylonitrile binder and fully stirring to prepare a composite slurry;

Step 5) In-situ transfer process of the coating: electrify for 10 hours at a constant voltage of 0.5V, during the electrification process, the zinc carbonate in the coating undergoes a redox reaction with lithium to generate lithium carbonate and a mixture of metallic zinc and zinc-lithium alloy, which forms A uniform layer and closely combined with the negative electrode, that is, a protective layer is formed on the surface of the negative electrode.

Example 5

Other steps are the same as in Example 1, the difference is only:

Step 1) dissolving 5 g of sodium oleate in 1500 mL of water to obtain a mixed system, then dissolving 145 g of nickel hydroxide in the above mixed system, adding 15 g of a polyacrylic acid binder and fully stirring to prepare a composite slurry;

Step 5) Coating in-situ transfer process: energize for 5 hours at a constant voltage of 1.5V, during the energization process, the nickel hydroxide in the coating undergoes a redox reaction with lithium ions to generate elemental nickel and a lithium-containing compound, and the two form A uniform layer and closely combined with the negative electrode, that is, a protective layer is formed on the surface of the negative electrode.

Example 6

Other steps are the same as in Example 1, the difference is only:

Step 1) Dissolve 5 g of castor oil in 1500 mL of water to obtain a mixed system, then dissolve 200 g of lead zirconate titanate in the above mixed system, add 20 g of sodium hydroxymethyl cellulose as a binder and fully stir to prepare a composite slurry; step 5) Coating in-situ transfer process: power on for 1 h under a constant voltage of 1.5V, during the power-on process, the lead zirconate titanate in the coating undergoes a redox reaction with lithium metal to generate elemental lead and lithium-containing compounds, and the two form A uniform layer and closely combined with the negative electrode, that is, a protective layer is formed on the surface of the negative electrode.

Example 7

Other steps are the same as in Example 1, the difference is only:

Step 1) Dissolving 15 g of sodium oleate in 1500 mL of water to obtain a mixed system, then dissolving 145 g of tin oxide in the above mixed system, adding 10 g of sodium acrylate binder and fully stirring to prepare a composite slurry;

Step 5) Coating in-situ transfer process: power on for 18h under a constant voltage of 1.5V, during the power-on process, the tin oxide in the coating undergoes a redox reaction with lithium metal to generate tin metal element and lithium oxide, and the two form A uniform layer and closely combined with the negative electrode, that is, a protective layer is formed on the surface of the negative electrode.

Comparative Example 1

Other steps are the same as in Example 1, the difference is:

Step 1) Dissolve 25 g of sodium dodecyl benzene sulfonate in 460 mL of water to obtain a mixed system, then disperse 160 g of alumina in the above mixed system, add 1 g of styrene-butadiene rubber binder, and fully stir to prepare a mixed slurry ;

Step 5) Coating in-situ transfer process: electrify for 10h under a constant voltage of 1.5V, during the electrification process, no in-situ transfer occurs.

Comparative Example 2

An uncoated polypropylene separator (commercial polypropylene separator) was placed between the positive and negative pole pieces, 100 μL of a commercial lithium-ion battery electrolyte was added, and the reeds were put in and sealed with a hydraulic sealer to prepare a button-type 2032 lithium-ion battery. And energized at 1.5V constant voltage for 10h, no in-situ transfer occurred during the energization process. Then a cyclic charge-discharge test was performed.

Comparative Example 3

The other steps are the same as those in Example 1, except that step 5) is omitted. The button-type 2032 lithium ion battery to be prepared is not subjected to the electrification step, but is directly subjected to the cyclic charge-discharge test.

The above-mentioned test methods were used to test Examples 1-7 and Comparative Examples 1-3, and the battery performance parameters were obtained as shown in Table 1.

Table 1 shows the performance parameters of lithium ion batteries prepared in Examples 1-7 and Comparative Examples 1-3

It can be seen from the data in Table 1 that the cycle stability of the lithium ion battery of the present invention is obviously better than that of the comparative example, especially the performance after 500 cycles is at least 20% higher than that of the comparative example, which has great application prospects.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for preparing a lithium ion battery negative electrode protection layer in an in-situ transfer manner, wherein the method comprises the following steps:

contacting the diaphragm coated with the coating with the lithium ion battery cathode, reacting, and obtaining a protective layer on the surface of the lithium ion battery cathode; the reactions include, but are not limited to, intercalation reactions and redox reactions; the reaction is carried out under the condition of certain external voltage; the raw material for forming the coating comprises at least one of the following coating materials: phosphates, manganates, carbonates, metal hydroxides, inorganic solid electrolyte materials, inorganic semiconductor materials and transition metal oxides that can react with lithium.

2. The method of claim 1, wherein lithium is ionically intercalated into the coating material for the intercalation reaction to produce a lithium-containing compound that forms a uniform protective layer on the surface of the negative electrode during the reaction.

3. The method of claim 1, wherein for the redox reaction, elemental lithium reacts with the coating material to produce a corresponding reduction product and a lithium-containing compound, and the reduction product and the lithium-containing compound are fused with the negative electrode as a whole to form a protective layer for the negative electrode.

4. A method according to any one of claims 1 to 3, wherein the applied voltage is greater than 0 and equal to or less than 5V, preferably greater than 0 and equal to or less than 3V; the applied voltage is applied for a period of time greater than 0 hour, preferably greater than 0 hour and not more than 24 hours.

5. The process according to any one of claims 1 to 4, wherein the transition metal oxide which can react with lithium is selected from one or more of nickel oxide, lead oxide, etc.; the phosphate is selected from one or more of ferric phosphate, nickel phosphate and the like; the manganate is selected from one or more of cobalt manganate, zinc manganate and the like; the carbonate is selected from one or more of iron carbonate, zinc carbonate and the like; the metal hydroxide is selected from one or more of nickel hydroxide, magnesium hydroxide and the like; the inorganic solid electrolyte material is selected from one or more of a lithium fast ion conductor, perovskite and the like; the inorganic semiconductor material is selected from one or more of tin oxide, silver sulfide and the like.

Preferably, the coating material is selected from one or more of cobalt manganate, nickel oxide, lead zirconate titanate, zinc carbonate, nickel hydroxide, tin oxide and iron phosphate.

6. The method of any of claims 1-5, wherein the feedstock of the coating further comprises a dispersant. The dispersant is selected from water and organic agents.

Preferably, the raw materials of the coating also comprise an auxiliary agent. Specifically, the auxiliary agent is at least one selected from a surfactant and a dispersing auxiliary agent. The surfactant comprises one or more of dodecyl benzene sulfonate, dioctyl succinate sulfonate, fatty alcohol-polyoxyethylene ether, oleyl alcohol-polyoxyethylene ether, polyoxyethylene fatty acid ester, oleate and stearate. The dispersing aid comprises one or more of polyacrylic acid and salts thereof, copolymerized poly (acrylic acid-methacrylic acid) and salts thereof, castor oil, dodecyl sulfate, triethylhexyl phosphoric acid, methyl amyl alcohol, polyacrylamide, polyoxyethylene ether, oleamide and the like.

Preferably, the raw material of the coating also comprises a binder. Specifically, the binder comprises one or more of styrene-butadiene rubber, fluorinated rubber, polyvinyl alcohol, hydroxymethyl cellulose salt, polyacrylic acid, polyacrylate and derivatives thereof, polyacrylonitrile, acrylate-acrylonitrile copolymer, polymethyl methacrylate, dimethyl diallyl ammonium chloride, alginate, pectate, deerhorn glue salt and polyvinylidene fluoride.

7. A method according to any one of claims 1-6, wherein the method further comprises the preparation of a membrane coated with a coating, the preparation of the membrane comprising the steps of:

(1) dispersing a coating material in a dispersing agent, optionally adding an auxiliary agent and/or a binder, and uniformly mixing to prepare mixed slurry of the coating material;

(2) coating the mixed slurry of the step (1) on one side surface of a diaphragm base layer;

(3) and (3) drying the diaphragm base layer coated with the mixed slurry in the step (2), thus preparing the diaphragm coated with the coating.

Preferably, in the step (1), the mass ratio of the coating material to the dispersant is (0.1-50):100, the mass ratio of the amount of the auxiliary agent to the dispersant is (0.001-20):100, and the mass ratio of the amount of the binder to the dispersant is (0.001-20): 100.

Preferably, the thickness of the coating is 0.1-10 μm.

Preferably, the coating has a coating areal density of 0.2 to 5g/m²。

8. A method for preparing a lithium ion battery, comprising the method for preparing a lithium ion battery negative electrode protective layer in an in-situ transfer manner according to any one of claims 1 to 7.

9. The preparation method according to claim 8, wherein the method further comprises the steps of contacting the positive electrode and the separator coated with the coating with the negative electrode of the lithium ion battery, and reacting to obtain a protective layer on the surface of the negative electrode of the lithium ion battery; the reactions include, but are not limited to, intercalation reactions and redox reactions; the reaction is carried out under the condition of certain external voltage; the raw material for forming the coating comprises at least one of the following coating materials: phosphates, manganates, carbonates, metal hydroxides, inorganic solid electrolyte materials, inorganic semiconductor materials and transition metal oxides that can react with lithium.

10. A lithium ion battery produced by the production method according to claim 8 or 9.

Preferably, the lithium ion battery is at least one of a button battery, a stacked battery and a wound battery.

Preferably, the outer package of the lithium ion battery is a soft plastic package or a steel shell package.

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