Preparation method of composite negative electrode and battery

Abstract

The invention discloses a preparation method of a composite negative electrode and a battery. The preparation method comprises the following steps: respectively heating a lithium metal sheet, lithium tert-butoxide and glycerol to a first preset temperature, a second preset temperature and a third preset temperature; the method comprises the following steps: reacting lithium tert-butoxide at a first preset temperature and glycerol at a second preset temperature on the surface of a lithium metal sheet at a third preset temperature through an atomic layer deposition method in an inert gas atmosphere to form a pre-coating layer; mixing lithium chloride, indium chloride tetrahydrate and deionized water to obtain a mixed solution; and placing the pre-coating layer in the mixed solution, and carrying out vacuum baking to obtain the lithium metal sheet composite negative electrode. Through an atomic layer deposition method, the polymer coating is accurately controlled in a layer-by-layer growth mode, the growth process, thickness and other parameters of the coating can be accurately adjusted, the stability and consistency of the coating quality are ensured, and the battery performance is improved.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to a method for preparing a composite negative electrode and a battery. Background Art

[0002] In the field of battery technology, lithium metal has great potential in realizing high energy density batteries due to its high theoretical specific capacity of 3860mAhg-1 and low electrochemical reduction potential of -3.040V relative to the standard hydrogen electrode. However, lithium metal has not been able to become a commercial anode for rechargeable batteries, mainly due to two key problems. On the one hand, lithium metal is highly reactive with the electrolyte, and an inhomogeneous solid electrolyte interphase is formed during battery operation, which leads to a large consumption of cyclable lithium and electrolyte. On the other hand, the formation of lithium dendrites poses serious safety risks, especially when cycling at high current density, where this risk is more prominent and may cause dangerous situations such as battery short circuit or even thermal runaway.

[0003] In order to solve these problems, researchers have tried a variety of strategies. In terms of solid electrolytes, they are used to construct all-solid-state lithium metal batteries in order to inhibit dendrite formation and reduce safety risks. However, solid electrolytes have many disadvantages, such as low ionic conductivity, which limits the ion transfer rate during battery charging and discharging, affecting the battery's rate performance; its mechanical properties are easily degraded, and it may crack or deform during the battery cycle, which in turn affects the structural stability of the battery; the electrode-electrolyte compatibility is poor, and side reactions are prone to occur at the interface, increasing the internal resistance of the battery; and there are interface contact problems, resulting in reduced charge transfer efficiency. Therefore, there are still major problems with the solid electrolyte-negative electrode interface in practical applications.

[0004] In contrast, surface coating technology is achieved through methods such as physical vapor deposition, wet chemistry, atomic and molecular layer deposition, etc., which has the advantage of simple operation and has become a promising technical route. In symmetric Li||Li batteries, these methods have improved the electrochemical cycle performance of lithium metal anodes to a certain extent. However, in practical lithium metal full batteries, when under high current density, batteries using surface-modified lithium anodes still experience rapid capacity decay. The root cause is that the ion conductivity of the coating material is low and cannot meet the requirements of rapid ion transport under high current density; the chemical and electrochemical stability is not ideal, and it is easy to decompose or react in the complex chemical environment of the battery, losing the protective effect on the anode; and the mechanical properties are poor, and it is difficult to withstand the volume change of lithium metal during charging and discharging, and it is easy to crack or peel off. Therefore, there is an urgent need for a new technical solution to protect the lithium metal anode, improve the performance and safety of the battery, and then promote the commercial application of lithium metal batteries. Summary of the invention

[0005] In order to overcome the defects in the prior art, the first purpose of the present invention is to provide a method for preparing a composite negative electrode, and the second purpose of the present invention is to provide a battery comprising a lithium metal composite negative electrode containing polymethylsiloxane prepared by the method for preparing the composite negative electrode.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, a method for preparing a composite negative electrode comprises the following steps:

[0008] The lithium metal sheet, lithium tert-butoxide and glycerol are heated to a first preset temperature, a second preset temperature and a third preset temperature respectively;

[0009] In an inert gas atmosphere, lithium tert-butoxide at a first preset temperature and glycerol at a second preset temperature are reacted on a surface of a lithium metal sheet at a third preset temperature by an atomic layer deposition method to form a pre-coating layer;

[0010] Mixing lithium chloride, indium chloride tetrahydrate, and deionized water to obtain a mixed solution;

[0011] A lithium metal sheet with a pre-coating layer is placed in a mixed solution and vacuum-baked to obtain a lithium metal composite negative electrode containing polymethylsiloxane.

[0012] Through the atomic layer deposition method, the polymer coating can be precisely controlled in a layer-by-layer growth mode. The growth process and thickness of the coating and other parameters can be accurately adjusted to ensure the stability and consistency of the coating quality, laying the foundation for improving battery performance.

[0013] Moreover, this method can achieve a highly conformable and uniform coating on substrates of any shape, that is, a thin film coverage. This enables the coating to fully exert its protective function, ensuring uniform protection and performance improvement of the lithium metal negative electrode regardless of the complexity of the substrate shape, effectively avoiding local performance differences and safety hazards caused by uneven coating.

[0014] The uniformly deposited coating makes the lithium deposition morphology more uniform and denser, effectively inhibiting the parasitic side reactions between lithium metal and electrolyte. This not only reduces the loss of lithium metal and the decomposition of the electrolyte, improves the coulombic efficiency of the battery, but also reduces the internal resistance of the battery, and improves the battery's charge and discharge performance and cycle stability.

[0015] The coating and lithium metal are in close contact through chemical bonding. The chemical bonding method enhances the bonding force between the coating and the lithium metal negative electrode, making the coating less likely to fall off or fail during the battery charging and discharging process, ensuring the stability of the battery during long-term cycling and helping to extend the battery life.

[0016] The coating on the surface of the lithium metal sheet reduces the formation and transmission of "free radicals" to the positive electrode through crosstalk, thereby forming a thin cathode electrolyte interface (CEI) rich in inorganic lithium fluoride on the positive electrode surface. This effect helps to protect the positive electrode material, maintain the structural and performance stability of the positive electrode, further improve the overall performance and cycle life of the battery, and enhance the reliability of the battery in high energy density application scenarios.

[0017] Preferably, the lithium metal sheet, lithium tert-butoxide and glycerol are heated to a first preset temperature, a second preset temperature and a third preset temperature respectively, including heating the lithium metal sheet to 150-180°C; heating the lithium tert-butoxide to 135-145°C and placing it in a bubbler; heating the glycerol to 150-160°C and placing it in a stainless steel cylinder. Further preferably, the lithium metal sheet is heated to 150°C; the lithium tert-butoxide is heated to 140°C and placed in a bubbler; the glycerol is heated to 150°C and placed in a stainless steel cylinder. Depending on the processing conditions, the bubbler may also be a pulse injection system. The stainless steel cylinder may also be a ceramic crucible.

[0018] Heating the lithium metal sheet, lithium tert-butoxide, and glycerol to specific temperatures separately helps ensure that each substance is in a suitable reactive state, allowing subsequent reactions to proceed smoothly, and is conducive to the formation of a uniform and high-performance pre-coating layer and the final composite negative electrode. Among them, the temperature of the lithium metal sheet can be set to ≤150°C. Its lower reaction temperature can reduce energy consumption in the production process, which is conducive to reducing the adverse effects of high temperature on the performance of lithium metal sheets and other materials, and expands the feasibility and applicability of this technology in actual production.

[0019] Preferably, the content of water and oxygen in the inert gas atmosphere is less than 1ppm. Lithium metal is highly reactive, and water and oxygen will react violently with lithium metal, destroying the surface structure of the lithium metal sheet and consuming lithium, affecting battery performance and safety. Maintaining a low water and oxygen content can effectively prevent unnecessary oxidation and side reactions of lithium metal during the preparation process, ensure the chemical purity and structural stability of the lithium metal composite negative electrode, thereby improving the cycle life and safety performance of the battery, enabling the battery to work stably during the charge and discharge process, and reducing capacity attenuation and safety hazards. Further preferably, the inert gas is argon or krypton.

[0020] Preferably, the atomic layer deposition method comprises at least five cyclic reactions, each cyclic reaction comprising the following steps:

[0021] In the first step, lithium tert-butoxide at a first preset temperature is introduced into a reaction chamber filled with argon gas in a pulsed manner to react with a lithium metal sheet at a second preset temperature;

[0022] The second step is to introduce argon gas for purging;

[0023] The third step is to introduce glycerol at a second preset temperature into a reaction chamber filled with argon gas in a pulsed manner to react with the lithium metal sheet;

[0024] The fourth step is to introduce argon gas for purging.

[0025] Lithium tert-butoxide and glycerol are used as precursors to react with the surface of lithium metal sheets within a specific time. Argon gas is purged to remove excess precursors and byproducts to ensure the consistency of each cycle. Through cyclic chemical adsorption and reaction, a uniform coating with controllable thickness is built layer by layer on the surface of the lithium metal sheet, ensuring the stability and consistency of the coating quality and improving battery performance.

[0026] Further preferably, the atomic layer deposition method comprises at least five cyclic reactions, each cyclic reaction comprising the following steps:

[0027] In the first step, lithium tert-butoxide at 140°C was pulsed into a reaction chamber filled with argon gas to react with a lithium metal sheet at 150°C for 10 seconds.

[0028] In the second step, argon gas was introduced for purging for 60 s;

[0029] In the third step, glycerol at 150°C was pulsed into a reaction chamber filled with argon gas to react with the lithium metal sheet for 10 seconds.

[0030] The fourth step is to introduce argon gas for purging for 60 seconds.

[0031] When the reaction time is short, the atomic layer cannot be deposited uniformly and subsequent reactions cannot proceed. If the reaction time is long, inert gas will be wasted, resulting in an increase in production costs.

[0032] Preferably, the atomic layer deposition method includes greater than or equal to 5 cycle reactions. Further preferably, the atomic layer deposition method includes 5 to 10 cycle reactions. In actual production, the number of cycles can be determined according to the thickness of the target coating. Generally, the number of cycle reactions is set to 5 to 10, which is within the tolerance range of the equipment and can also meet the requirements for the thickness of the negative electrode sheet. If the number of cycle reactions is set to less than 5 times, the hardness of the negative electrode sheet is small and may not meet the use requirements.

[0033] Preferably, the molar ratio of the lithium tert-butoxide to the glycerol is 1:(2-10). Different ratios of lithium tert-butoxide to glycerol can adjust the structure and functional group distribution of the coating, and can affect the properties of the coating such as lithium affinity and ion conduction channels. The present application sets the molar ratio of lithium tert-butoxide to glycerol within the range of 1:(2-10), which can form a pre-coating with good performance, so that it can play the best effect in inhibiting the reaction of lithium metal and electrolyte, guiding the uniform deposition of lithium, etc., thereby improving the electrochemical performance and cycle stability of the lithium metal composite negative electrode, and reducing the capacity decay and safety risks of the battery during the charge and discharge process.

[0034] Preferably, the mixing of lithium chloride, indium chloride tetrahydrate and deionized water to obtain a mixed solution comprises:

[0035] Weigh lithium chloride and indium chloride tetrahydrate, add them to deionized water, and stir to obtain a mixed solution; lithium chloride and indium chloride tetrahydrate are mixed in a mass ratio of (1-2): 1. The volume of the deionized water is sufficient to completely dissolve the added lithium chloride and indium chloride tetrahydrate, and ensure that the solution is clear.

[0036] Preferably, the pre-coating layer is placed in a mixed solution and vacuum-baked to obtain a lithium metal sheet composite negative electrode.

[0037] The pre-coating layer is immersed in the mixed solution for 5 to 10 hours, and baked in a vacuum oven at 60° C. for 6 to 12 hours to obtain a lithium metal sheet composite negative electrode.

[0038] In a second aspect, a battery includes a lithium metal composite negative electrode containing polymethylsiloxane prepared by the above-mentioned method for preparing a composite negative electrode.

[0039] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0040] 1. Through the atomic layer deposition method, the polymer coating can be precisely controlled in a layer-by-layer growth mode, and the growth process and thickness of the coating and other parameters can be accurately adjusted to ensure the stability and consistency of the coating quality, laying the foundation for improving battery performance. This method can achieve a very close and uniform coating on a substrate of any shape, that is, forming a thin film coverage. This enables the coating to fully exert its protective function, and no matter how complex the shape of the substrate is, it can ensure that the lithium metal negative electrode is uniformly protected and the performance is improved, effectively avoiding local performance differences and safety hazards caused by uneven coating.

[0041] 2. The uniformly deposited coating makes the lithium deposition morphology more uniform and denser, effectively inhibiting the parasitic side reactions between lithium metal and electrolyte. This not only reduces the loss of lithium metal and the decomposition of the electrolyte, improves the coulombic efficiency of the battery, but also reduces the internal resistance of the battery, and improves the battery's charge and discharge performance and cycle stability.

[0042] 3. The coating and lithium metal are in close contact through chemical bonding. The chemical bonding method enhances the bonding force between the coating and the lithium metal negative electrode, making the coating less likely to fall off or fail during the battery charging and discharging process, ensuring the stability of the battery during long-term cycle use and helping to extend the battery life.

[0043] 4. The coating on the surface of lithium metal reduces the formation and transmission of "free radicals" to the positive electrode through crosstalk, thereby forming a thin cathode electrolyte interface (CEI) rich in inorganic lithium fluoride on the surface of the positive electrode. This effect helps to protect the positive electrode material, maintain the structural and performance stability of the positive electrode, further improve the overall performance and cycle life of the battery, and enhance the reliability of the battery in high energy density application scenarios.

[0044] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail as follows. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Embodiment 1:

[0047] A method for preparing a composite negative electrode comprises the following steps:

[0048] Heat the lithium metal sheet to 150°C; heat lithium tert-butoxide to 140°C and place it in a bubbler; heat glycerol to 150°C and place it in a stainless steel cylinder.

[0049] In an argon atmosphere (water and oxygen content <1 ppm), lithium tert-butoxide at 140° C. and glycerol at 150° C. are reacted on the surface of a lithium metal sheet at 150° C. by an atomic layer deposition method to form a pre-coating layer. The atomic layer deposition method includes five cycle reactions, each of which includes:

[0050] In the first step, lithium tert-butoxide at 140°C was pulsed into a reaction chamber filled with argon gas to react with a lithium metal sheet at 150°C for 10 seconds.

[0051] In the second step, argon gas was introduced for purging for 60 s;

[0052] In the third step, glycerol at 150°C was pulsed into a reaction chamber filled with argon gas to react with the lithium metal sheet for 10 seconds.

[0053] Step 4: introduce argon gas for purging for 60 seconds;

[0054] The molar ratio of lithium tert-butoxide to glycerol is 1:1.

[0055] Lithium chloride and indium chloride tetrahydrate were weighed in a mass ratio of 1:1, added into deionized water, and stirred to obtain a mixed solution.

[0056] The lithium metal sheet with the pre-coating layer was immersed in the mixed solution for 5 hours, and baked in a vacuum oven at 60° C. for 6 hours to obtain a lithium metal sheet composite negative electrode.

[0057] This embodiment also provides a lithium-ion battery assembled using the lithium metal sheet composite negative electrode, as follows:

[0058] (1) Positive electrode (16.0 mg / cm on each side) 2 ): It is composed of lithium nickel cobalt manganese oxide (NCM811), conductive carbon black (SuperP), polyvinylidene fluoride (PVDF5130) and carbon nanotubes (CNT) in a weight ratio of 96:1.8:1.7:0.5, and the current collector is made of aluminum foil.

[0059] (2) Negative electrode: the above-mentioned lithium metal sheet composite negative electrode.

[0060] (3) Diaphragm: Polyethylene (PE) diaphragm, thickness 20 μm.

[0061] (4) Electrolyte: lithium bis(fluorosulfonyl)imide: dimethyl ether: triethylene glycol dimethyl ether = 1:1.2:3 (molar ratio).

[0062] The battery is assembled according to the conventional assembly method of lithium-ion batteries.

[0063] Embodiment 2:

[0064] A method for preparing a composite negative electrode comprises the following steps:

[0065] Heat the lithium metal sheet to 150°C; heat lithium tert-butoxide to 140°C and place it in a bubbler; heat glycerol to 150°C and place it in a stainless steel cylinder.

[0066] In an argon atmosphere (water and oxygen content <1 ppm), lithium tert-butoxide at 140° C. and glycerol at 150° C. are reacted on the surface of a lithium metal sheet at 150° C. by an atomic layer deposition method to form a pre-coating layer. The atomic layer deposition method includes five cycle reactions, each of which includes:

[0067] In the first step, lithium tert-butoxide at 140°C was pulsed into a reaction chamber filled with argon gas to react with a lithium metal sheet at 150°C for 10 seconds.

[0068] In the second step, argon gas was introduced for purging for 60 s;

[0069] In the third step, glycerol at 150°C was pulsed into a reaction chamber filled with argon gas to react with the lithium metal sheet for 10 seconds.

[0070] Step 4: introduce argon gas for purging for 60 seconds;

[0071] The molar ratio of lithium tert-butoxide to glycerol is 1:2.

[0072] Lithium chloride and indium chloride tetrahydrate were weighed in a mass ratio of 1:1, added into deionized water, and stirred to obtain a mixed solution.

[0073] The lithium metal sheet with the pre-coating layer was immersed in the mixed solution for 5 hours, and baked in a vacuum oven at 60° C. for 6 hours to obtain a lithium metal sheet composite negative electrode.

[0074] This embodiment also provides a lithium-ion battery assembled using the lithium metal sheet composite negative electrode, as follows:

[0075] (1) Positive electrode (16.0 mg / cm2 per side): composed of lithium nickel cobalt manganese oxide (NCM811), conductive carbon black (SuperP), polyvinylidene fluoride (PVDF5130) and carbon nanotubes (CNT) in a weight ratio of 96:1.8:1.7:0.5.

[0076] (2) Negative electrode: the above-mentioned lithium metal sheet composite negative electrode.

[0077] (3) Diaphragm: Polyethylene (PE) diaphragm, thickness 20 μm.

[0078] (4) Electrolyte: lithium bis(fluorosulfonyl)imide: dimethyl ether: triethylene glycol dimethyl ether = 1:1.2:3 (molar ratio).

[0079] The battery is assembled according to the conventional assembly method of lithium-ion batteries.

[0080] Embodiment 3:

[0081] A method for preparing a lithium metal sheet composite negative electrode comprises the following steps:

[0082] Heat the lithium metal sheet to 150°C; heat lithium tert-butoxide to 140°C and place it in a bubbler; heat glycerol to 150°C and place it in a stainless steel cylinder.

[0083] In an argon atmosphere (water and oxygen content <1 ppm), lithium tert-butoxide at 140° C. and glycerol at 150° C. are reacted on the surface of a lithium metal sheet at 150° C. by an atomic layer deposition method to form a pre-coating layer. The atomic layer deposition method includes eight cycle reactions, each of which includes:

[0084] In the first step, lithium tert-butoxide at 140°C was pulsed into a reaction chamber filled with argon gas to react with a lithium metal sheet at 150°C for 10 seconds.

[0085] In the second step, argon gas was introduced for purging for 60 s;

[0086] In the third step, glycerol at 150°C was pulsed into a reaction chamber filled with argon gas to react with the lithium metal sheet for 10 seconds.

[0087] Step 4: introduce argon gas for purging for 60 seconds;

[0088] The molar ratio of lithium tert-butoxide to glycerol is 1:1.

[0089] Lithium chloride and indium chloride tetrahydrate were weighed in a mass ratio of 1:1, added into deionized water, and stirred to obtain a mixed solution.

[0090] The lithium metal sheet with the pre-coating layer was immersed in the mixed solution for 5 hours, and baked in a vacuum oven at 60° C. for 6 hours to obtain a lithium metal sheet composite negative electrode.

[0091] This embodiment also provides a lithium-ion battery assembled using the lithium metal sheet composite negative electrode, as follows:

[0092] (1) Positive electrode (16.0 mg / cm2 per side): composed of lithium nickel cobalt manganese oxide (NCM811), conductive carbon black (SuperP), polyvinylidene fluoride (PVDF5130) and carbon nanotubes (CNT) in a weight ratio of 96:1.8:1.7:0.5.

[0093] (2) Negative electrode: the above-mentioned lithium metal sheet composite negative electrode.

[0094] (3) Diaphragm: Polyethylene (PE) diaphragm, thickness 20 μm.

[0095] (4) Electrolyte: lithium bis(fluorosulfonyl)imide: dimethyl ether: triethylene glycol dimethyl ether = 1:1.2:3 (molar ratio).

[0096] The battery is assembled according to the conventional assembly method of lithium-ion batteries.

[0097] Comparative Example 1:

[0098] A lithium ion battery, specifically as follows:

[0099] (1) Positive electrode (16.0 mg / cm2 per side): composed of lithium nickel cobalt manganese oxide (NCM811), conductive carbon black (SuperP), polyvinylidene fluoride (PVDF5130) and carbon nanotubes (CNT) in a weight ratio of 96:1.8:1.7:0.5.

[0100] (2) Negative electrode: pure metallic lithium sheet.

[0101] (3) Diaphragm: Polyethylene (PE) diaphragm, thickness 20 μm.

[0102] (4) Electrolyte: lithium bis(fluorosulfonyl)imide: dimethyl ether: triethylene glycol dimethyl ether = 1:1.2:3 (molar ratio).

[0103] The battery is assembled according to the conventional assembly method of lithium-ion batteries.

[0104] Comparative Example 2:

[0105] A lithium ion battery, specifically as follows:

[0106] (1) Positive electrode (16.0 mg / cm2 per side): composed of lithium nickel cobalt manganese oxide (NCM811), conductive carbon black (SuperP), polyvinylidene fluoride (PVDF5130) and carbon nanotubes (CNT) in a weight ratio of 96:1.8:1.7:0.5.

[0107] (2) Negative electrode: soaked lithium metal sheet. The specific operation of soaking the lithium metal sheet includes: weighing lithium chloride and indium chloride tetrahydrate in a mass ratio of 1:1, adding them to deionized water, and stirring to obtain a mixed solution. Soaking the lithium metal sheet in the mixed solution for 5 hours, and baking it in a vacuum oven at 60°C for 6 hours to obtain the soaked lithium metal sheet.

[0108] (3) Diaphragm: Polyethylene (PE) diaphragm, thickness 20 μm.

[0109] (4) Electrolyte: lithium bis(fluorosulfonyl)imide: dimethyl ether: triethylene glycol dimethyl ether = 1:1.2:3 (molar ratio).

[0110] The battery is assembled according to the conventional assembly method of lithium-ion batteries.

[0111] The batteries prepared in the above-mentioned Examples 1-3 and Comparative Examples 1 and 2 were tested as follows:

[0112] Ionic conductivity test: Using an Au substrate, a coating film with adjustable thickness (i.e., the coating in Examples 1-3) was deposited. Then, using electrochemical impedance spectroscopy (EIS), the EIS spectrum of the coating film was measured, and the bulk resistance (Rb) of the film was further determined. Subsequently, the in-plane ionic conductivity (σ) of the coating film was calculated using the following formula: σ = d / [Rb×(l×δ)], where d is the gap between the Au branches (2um), l is the total branch length (8000um), and δ is the coating film thickness that varies with the atomic deposition cycle.

[0113] Lithium ion migration number test: The lithium ion migration number (tLi+) immersed in the coating was measured in a symmetrical Li||Li battery at room temperature using a polarization voltage of 10mV.

[0114] XPS test: Fresh coated lithium metal sheets, coated lithium metal sheets after cycling, and pure metal lithium sheets before and after cycling were cut into 4*4mm samples and tested and analyzed using an X-ray spectrometer.

[0115] Cycle test: The working window during cycle test is 2.5-4.3V vs Li / Li + .

[0116] The test results are shown in Table 1 below:

[0117]

[0118] Table 1

[0119] From the test results in the above table, it can be seen that the batteries assembled in Examples 1-3 have high ion conductivity, a large number of lithium ion migrations, and improved battery performance.

[0120] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a composite negative electrode, characterized in that: The following steps are involved: The lithium metal sheet, lithium tert-butoxide and glycerol are heated to a first preset temperature, a second preset temperature and a third preset temperature respectively; In an inert gas atmosphere, lithium tert-butoxide at a first preset temperature and glycerol at a second preset temperature are reacted on a surface of a lithium metal sheet at a third preset temperature by an atomic layer deposition method to form a pre-coating layer; Mixing lithium chloride, indium chloride tetrahydrate, and deionized water to obtain a mixed solution; A lithium metal sheet with a pre-coating layer is placed in a mixed solution and vacuum-baked to obtain a lithium metal composite negative electrode containing polymethylsiloxane.

2. The method for preparing a composite negative electrode according to claim 1, characterized in that: The lithium metal sheet, lithium tert-butoxide and glycerol are heated to a first preset temperature, a second preset temperature and a third preset temperature respectively, including heating the lithium metal sheet to 150-180°C; heating the lithium tert-butoxide to 135-145°C and placing it in a bubbler; and heating the glycerol to 150-160°C and placing it in a stainless steel cylinder.

3. The method for preparing a composite negative electrode according to claim 1, characterized in that: The content of water and oxygen in the inert gas atmosphere is less than 1ppm; Preferably, the inert gas is argon or krypton.

4. The method for preparing a lithium metal sheet composite negative electrode according to claim 1, characterized in that: The atomic layer deposition method comprises at least five cycle reactions, each cycle reaction The following steps are involved: In the first step, lithium tert-butoxide at a first preset temperature is introduced into a reaction chamber filled with argon gas in a pulsed manner to react with a lithium metal sheet at a second preset temperature; The second step is to introduce argon gas for purging; The third step is to introduce glycerol at a second preset temperature into a reaction chamber filled with argon gas in a pulsed manner to react with the lithium metal sheet; The fourth step is to introduce argon gas for purging.

5. The method for preparing a composite negative electrode according to claim 4, characterized in that: The atomic layer deposition method comprises at least five cycle reactions, each cycle reaction The following steps are involved: In the first step, lithium tert-butoxide at 140°C was pulsed into a reaction chamber filled with argon gas to react with a lithium metal sheet at 150°C for 10 seconds. In the second step, argon gas was introduced for purging for 60 s; In the third step, glycerol at 150°C was pulsed into a reaction chamber filled with argon gas to react with the lithium metal sheet for 10 seconds. The fourth step is to introduce argon gas for purging for 60 seconds.

6. The method for preparing a composite negative electrode according to claim 4, characterized in that: The atomic layer deposition method includes more than or equal to 5 cycle reactions.

7. The method for preparing a composite negative electrode according to claim 1, characterized in that: The molar ratio of the lithium tert-butoxide to the glycerol is 1:(2-10).

8. The method for preparing a composite negative electrode according to claim 1, characterized in that: The method of mixing lithium chloride, indium chloride tetrahydrate and deionized water to obtain a mixed solution comprises: Lithium chloride and indium chloride tetrahydrate are mixed in a mass ratio of (1-2):1, added into deionized water, and stirred to obtain a mixed solution.

9. The method for preparing a composite negative electrode according to claim 1, characterized in that: The lithium metal sheet with the pre-coating is placed in the mixed solution and vacuum-baked to obtain the lithium metal sheet composite negative electrode. Including: The pre-coating layer is immersed in the mixed solution for 5 to 10 hours, and baked in a vacuum oven at 60° C. for 6 to 12 hours to obtain a lithium metal composite negative electrode containing polymethylsiloxane.

10. A battery, characterized in that: A lithium metal composite negative electrode containing polymethylsiloxane prepared by the method for preparing a composite negative electrode according to any one of claims 1 to 9.

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