Method for inhibiting growth of lithium dendrites by adding artificial protective films to electrodes on two sides

Abstract

The invention discloses a method for inhibiting lithium dendrite growth by adding artificial protective films to electrodes on two sides, and aims to solve the problems that an existing lithium metal negative electrode protection system only pays attention to lithium metal negative electrode protection, and the dendrite inhibition effect is poor. The method for inhibiting the growth of the lithium dendrites by adding the artificial protective films to the electrodes on the two sides comprises the following steps: 1, adding a polymer film-forming agent into an organic solvent to obtain an artificial protective film polymer skeleton solution; 2, adding an oxide into the artificial protective film polymer skeleton solution, and stirring at the temperature of 20-80 DEG C; 3, uniformly coating a substrate with the artificial protective film precursor turbid liquid, and uniformly forming a film by using a spin coater; and 4, attaching artificial protective films to two sides of the positive electrode and the negative electrode of the lithium ion battery, wherein the negative electrode is made of metal lithium. According to the invention, the oxide and the polymer film jointly generate a dielectric effect to regulate and control the transport behavior of lithium ions in the electrolyte, and the lithium metal negative electrode under the protection of the electrodes on the two sides realizes dendrite-free deposition and has ultrahigh cycle life.

Description

Technical Field

[0001] The present invention relates to a method for inhibiting dendrites of a lithium metal negative electrode, in particular to a method for adding artificial protective films to electrodes on both sides to inhibit the growth of lithium dendrites. Background Art

[0002] After two energy transitions, from firewood to coal and then from coal to oil, the world is now undergoing a third energy transition, seeking a shift toward low-pollution, diversified, renewable, and low-carbon energy sources. The core of this transition is to reduce dependence on fossil fuels to address global climate change and environmental issues. Under the "dual carbon" framework, namely the goals of "carbon peak" and "carbon neutrality," the utilization of fossil fuels in energy materials is gradually declining, while the utilization of renewable energy is gradually increasing. This transition requires cleaner and more sustainable energy solutions. However, renewable energy generation is unstable, intermittent, discontinuous, and uncontrollable, making it unsuitable for large-scale application. For example, wind power and photovoltaic power generation rely on weather conditions, which are unpredictable and uncontrollable, resulting in fluctuating power generation and posing challenges to grid stability. The discovery and development of batteries precisely meet people's demand for efficient and convenient energy. Since then, various commercial batteries have been invented, such as lead-acid batteries, zinc-manganese batteries, nickel-metal hydride batteries, and lithium-ion batteries. Batteries are widely used due to their long cycle life and low self-discharge.

[0003] Lithium metal has the most negative reduction potential (-3.045 V compared to standard hydrogen electrode) and a very small mass density (0.59 g cm -3 ) and a very high theoretical specific capacity (volume specific capacity of 2061 mAh cm -3 and mass specific capacity of 3860mAh g -1 ), is a lithium-ion battery with graphite (372 mAh g -1 ) is more than 10 times that of the negative electrode. Early researchers explored methods to inhibit lithium dendrite growth, primarily by focusing on the mechanisms that cause it. In electrolytes, due to the instability of the SEI layer formed at the interface between metallic lithium and the liquid electrolyte, additives that stabilize the SEI layer were sought to inhibit dendrite growth. However, with continued cycling, some additives are continuously consumed and ultimately lose their protective effect. For separators, the relationship between ionic conductivity, mechanical modulus, and flame retardancy must be considered. Improving the mechanical modulus of the separator is one way to prevent lithium dendrites from penetrating the separator, but this is limited to low current densities and low capacities; at high current densities, there is still a risk of lithium dendrites penetrating the separator. Furthermore, separators made of novel materials face challenges such as poor stability, complex manufacturing processes, and high costs. In the field of solid-state electrolytes, the solid-solid interface suffers from poor stability, and with continued cycling, the internal resistance of the battery increases, impacting overall performance. Summary of the Invention

[0004] The present invention aims to solve the problem that the existing lithium metal negative electrode protection system only focuses on lithium metal negative electrode protection and has poor dendrite inhibition effect, and provides a method for adding artificial protective films on both sides of the electrodes to inhibit lithium dendrite growth.

[0005] The method of adding artificial protective films on both sides of the electrodes to inhibit the growth of lithium dendrites is achieved by the following steps:

[0006] 1. Preparation of artificial protective membrane polymer skeleton solution:

[0007] Adding a polymer film-forming agent to an organic solvent and stirring at a temperature of 40°C to 80°C until the polymer film-forming agent is completely dissolved to obtain an artificial protective film polymer skeleton solution;

[0008] 2. Preparation of artificial protective film precursor suspension:

[0009] The oxide is added to the artificial protective membrane polymer skeleton solution, the mass ratio of the oxide to the polymer film-forming agent is controlled to be 0.5:9-10:9, the mixture is stirred at a temperature of 20°C-80°C, and ultrasonically dispersed to obtain an artificial protective membrane precursor suspension;

[0010] 3. Preparation of artificial protective film:

[0011] The artificial protective film precursor suspension is evenly coated on the substrate, and a coating machine is used to form a uniform film, and the artificial protective film is obtained after curing;

[0012] 4. Battery assembly:

[0013] The artificial protective film is attached to both sides of the positive electrode and the negative electrode of the lithium-ion battery, and the negative electrode is selected from metallic lithium, thereby completing the method of adding artificial protective films on both sides of the electrodes to inhibit the growth of lithium dendrites;

[0014] wherein the polymer film-forming agent is one or more of poly(vinylidene fluoride- co -hexafluoropropylene), starch, maltodextrin, pullulan, okra biopolymer, moringa gum, chitosan, hyaluronic acid, sodium alginate, pectin, gelatin, gum arabic, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyperfluorosulfonic acid, acrylic resin (including acrylate, acrylonitrile, acrylamide and maleic anhydride polymers), polyether, polystyrene and copolymers thereof, and polyvinyl chloride;

[0015] The oxide is one or more of sodium oxide, potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, ferroferric oxide, ferric oxide, cuprous oxide, silver oxide, lithium oxide, chromium oxide, cobalt oxide, nickel oxide, titanium oxide, zirconium oxide, silicon dioxide, arsenic trioxide, lead tetroxide, phosphorus pentoxide, iodine pentoxide, and selenium dioxide.

[0016] The present invention inhibits lithium dendrite growth through an artificial protective film. The polymer@oxide protective film system produces a dielectric effect under the action of an external electric field. The greater the electric field strength, the stronger the dielectric effect, thereby weakening the local electric field strength, thereby regulating the local lithium ion concentration distribution and reducing the concentration polarization within the battery. The dielectric constant of poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silicon dioxide used in the present invention is 4.59 farads / meter, the dielectric constant of poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide is 13.89 farads / meter, and the dielectric constant of poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% cobalt tetroxide is 143 farads / meter. When an artificial protective film is added to the negative electrode, the reverse electric field generated by the dielectric effect makes the lithium ion concentration distribution more uniform, thereby inhibiting dendrite growth. Furthermore, when the present invention adds an artificial protective film on both the positive and negative electrodes, the lithium ions extracted and embedded at the positive electrode tend to be evenly distributed. When they pass through the diaphragm and reach the negative electrode side, they are again regulated by the reverse electric field generated by the dielectric effect, thereby achieving a more uniform distribution of lithium ions and greatly inhibiting the dendrite growth caused by lithium ion aggregation.

[0017] The method of adding artificial protective films to electrodes on both sides of the present invention to inhibit lithium dendrite growth has the following beneficial effects:

[0018] 1. This invention proposes, for the first time, a battery system with artificial protective films on both electrodes. This system utilizes the dielectric effect of oxide and polymer films to regulate lithium ion transport in the electrolyte. By studying the addition of a protective film to the lithium metal anode and the addition of protective films on both electrodes, a dual-side electrode protection method was developed. The lithium metal anode protected by dual electrodes exhibits dendrite-free deposition and exhibits an exceptionally long cycle life.

[0019] 2. The present invention prepares a polymer@oxide protective film system, the dielectric effect of which can regulate the lithium ion concentration distribution, reduce concentration polarization and thus inhibit dendrite growth.

[0020] 3. The lithium metal negative electrode protected by the method of the present invention achieves no dendrite growth.

[0021] 4. The synthesis process of the present invention is very simple and the range of raw material selection is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1Actual photos of three artificial protective film precursor suspensions prepared in the examples;

[0023] Figure 2 This is a physical picture of the artificial protective membranes prepared from the three artificial protective membrane precursor suspensions in the examples;

[0024] Figure 3 This is the electrochemical impedance spectroscopy test diagram of the artificial protective membrane battery system prepared in Example 2;

[0025] Figure 4 This is a diagram showing the long cycle test results of the artificial protective membrane battery system prepared in Example 1;

[0026] Figure 5 This is a scanning electron microscope image of the lithium metal negative electrode of the artificial protective membrane battery system prepared in Example 3 after long-term cycling;

[0027] Figure 6 This is a diagram showing a long-cycle test of the artificial protective membrane battery system prepared in Example 2. DETAILED DESCRIPTION

[0028] Specific embodiment 1: The method of adding artificial protective films to the electrodes on both sides to inhibit the growth of lithium dendrites in this embodiment is implemented according to the following steps:

[0029] 1. Preparation of artificial protective membrane polymer skeleton solution:

[0030] Adding a polymer film-forming agent to an organic solvent and stirring at a temperature of 40°C to 80°C until the polymer film-forming agent is completely dissolved to obtain an artificial protective film polymer skeleton solution;

[0031] 2. Preparation of artificial protective film precursor suspension:

[0032] The oxide is added to the artificial protective membrane polymer skeleton solution, the mass ratio of the oxide to the polymer film-forming agent is controlled to be 0.5:9-10:9, the mixture is stirred at a temperature of 20°C-80°C, and ultrasonically dispersed to obtain an artificial protective membrane precursor suspension;

[0033] 3. Preparation of artificial protective film:

[0034] The artificial protective film precursor suspension is evenly coated on the substrate, and a coating machine is used to form a uniform film, and the artificial protective film is obtained after curing;

[0035] 4. Battery assembly:

[0036] The artificial protective film is attached to both sides of the positive electrode and the negative electrode of the lithium-ion battery, and the negative electrode is selected from metallic lithium, thereby completing the method of adding artificial protective films on both sides of the electrodes to inhibit the growth of lithium dendrites;

[0037] wherein the polymer film-forming agent is one or more of poly(vinylidene fluoride- co -hexafluoropropylene), starch, maltodextrin, pullulan, okra biopolymer, moringa gum, chitosan, hyaluronic acid, sodium alginate, pectin, gelatin, gum arabic, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyperfluorosulfonic acid, acrylic resin (including acrylate, acrylonitrile, acrylamide and maleic anhydride polymers), polyether, polystyrene and copolymers thereof, and polyvinyl chloride;

[0038] The oxide is one or more of sodium oxide, potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, ferroferric oxide, ferric oxide, cuprous oxide, silver oxide, lithium oxide, chromium oxide, cobalt oxide, nickel oxide, titanium oxide, zirconium oxide, silicon dioxide, arsenic trioxide, lead tetroxide, phosphorus pentoxide, iodine pentoxide, and selenium dioxide.

[0039] In step three of this embodiment, the dielectric constant of the artificial protective film is controlled to be 4 to 150 farads / meter.

[0040] The lithium-ion battery described in step 4 of this embodiment is a button battery, a wound soft-pack battery, or a laminated soft-pack battery.

[0041] This embodiment inhibits dendrite growth by regulating the lithium ion concentration distribution in the electrolyte through the dielectric effect generated by the oxide and polymer in the artificial protective film. This also modulates the dielectric constant of the protective film on both the positive and negative electrodes of the lithium-ion battery. The protective film acts at the electrolyte. Conventional techniques generally inhibit dendrite growth by increasing the Young's modulus of inorganic fillers within the protective film, but this acts at the interface of the protective film. The two techniques operate on different principles.

[0042] This embodiment proposes a method for adding an artificial protective film on both sides of the electrodes to inhibit the growth of lithium dendrites. An artificial protective film with a simple manufacturing process and controllable cost is constructed. The artificial protective film is added to both sides of the electrodes at the same time to achieve a lithium ion deposition-free dendrite growth battery system under long cycles.

[0043] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the average molecular weight Mw of the polymer film-forming agent in step 1 is 10,000 to 10,000,000.

[0044] Specific embodiment three: This embodiment is different from specific embodiment one or two in that the concentration of the polymer film-forming agent in the artificial protective membrane polymer skeleton solution in step one is 0.1 wt % to 10 wt %.

[0045] Specific embodiment four: This embodiment is different from any of specific embodiments one to three in that the organic solvent in step one is a mixed solvent of one or more of n-hexane, turpentine, cycloalkane, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, ethyl acetate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, tetrahydrofuran, ether, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, formic acid, glacial acetic acid, phenol, and m-cresol.

[0046] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that the mass ratio of the oxide to the polymer film-forming agent in step 2 is controlled to be 1:9 to 2:9.

[0047] This embodiment optimizes the ratio of oxide to polymer film-forming agent.

[0048] Specific embodiment 6: This embodiment is different from any one of specific embodiments 1 to 5 in that the oxide in step 2 is silicon dioxide or cobalt trioxide.

[0049] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that in step two, the stirring treatment is carried out at a temperature of 30° C. to 50° C. for 8 to 12 hours.

[0050] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that the substrate described in step three is gold foil, platinum foil, copper foil, nickel foil, chromium foil, aluminum foil, zinc foil, iron foil, titanium foil or zirconium foil.

[0051] Specific embodiment 9: This embodiment differs from any one of specific embodiments 1 to 8 in that the thickness of the artificial protective film in step 3 is 0.5-5 μm.

[0052] Specific embodiment ten: This embodiment differs from any one of specific embodiments one to nine in that the positive electrode material of the lithium-ion battery in step four is lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0053] Example 1: The method of adding an artificial protective film to a single-side electrode to inhibit lithium dendrite growth is implemented by the following steps:

[0054] 1. Preparation of artificial protective membrane polymer skeleton solution:

[0055] Adding a polymer film-forming agent, poly(vinylidene fluoride-co-hexafluoropropylene), to acetone at a rate of 10 ml of acetone per gram of the polymer film-forming agent, and magnetically stirring at 50°C until the polymer film-forming agent is completely dissolved at a stirring speed of 1000 rpm to obtain a colorless, transparent solution of the polymer skeleton of the artificial protective membrane;

[0056] 2. Preparation of artificial protective film precursor suspension:

[0057] Silica was added to the artificial protective membrane polymer skeleton solution, with the mass ratio of silica to poly(vinylidene fluoride-co-hexafluoropropylene) being controlled at 1:9. The solution was treated with magnetic stirring at 40°C for 10 hours and ultrasonically dispersed for 1 hour to obtain a poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silica precursor suspension.

[0058] 3. Preparation of artificial protective film:

[0059] The artificial protective film precursor suspension was evenly coated on the substrate and a film was formed evenly using a spin coater. The spin coater speed was controlled at 1000 rpm for 30 seconds. The film was then dried in a vacuum oven to obtain an artificial protective film with a thickness of 2 μm, which was recorded as poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silica.

[0060] 4. Battery assembly:

[0061] Poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silica is attached to one side of the lithium metal, and lithium metal is also used as the counter electrode, thereby completing the method of protecting one side of the lithium||lithium battery.

[0062] Example 2: The method of adding artificial protective films to the electrodes on both sides of this embodiment to inhibit the growth of lithium dendrites is implemented according to the following steps:

[0063] 1. Preparation of artificial protective membrane polymer skeleton solution:

[0064] Adding a polymer film-forming agent, poly(vinylidene fluoride-co-hexafluoropropylene), to acetone at a rate of 10 ml of acetone per gram of the polymer film-forming agent, and magnetically stirring at 50°C until the polymer film-forming agent is completely dissolved at a stirring speed of 1000 rpm to obtain a colorless, transparent solution of the polymer skeleton of the artificial protective membrane;

[0065] 2. Preparation of artificial protective film precursor suspension:

[0066] Silica was added to the artificial protective membrane polymer skeleton solution, with the mass ratio of silica to poly(vinylidene fluoride-co-hexafluoropropylene) being controlled at 1:9. The solution was treated with magnetic stirring at 40°C for 10 hours and ultrasonically dispersed for 1 hour to obtain a poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silica precursor suspension.

[0067] Cobalt tetroxide was added to the artificial protective membrane polymer skeleton solution, and the mass ratio of cobalt tetroxide to poly (vinylidene fluoride-co-hexafluoropropylene) was controlled to be 1:99. The solution was treated with magnetic stirring at 40°C for 10 hours and ultrasonically dispersed for 1 hour to obtain a poly (vinylidene fluoride-co-hexafluoropropylene) @ 1 wt% cobalt tetroxide precursor suspension.

[0068] 3. Preparation of artificial protective film:

[0069] The artificial protective film precursor suspension was evenly coated on the substrate and a film was formed evenly using a spin coater. The spin coater speed was controlled at 1000 rpm for 30 seconds, and the film was dried in a vacuum oven to obtain an artificial protective film with a thickness of 2 μm, which was recorded as poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silicon dioxide and poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide, respectively.

[0070] 4. Battery assembly:

[0071] Metallic lithium is used for both electrodes, one side is attached to poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silicon dioxide, and the other side is attached to poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide, thus completing the method of protecting both sides of the lithium||lithium battery.

[0072] Example 3: The method of adding artificial protective films to the electrodes on both sides to inhibit the growth of lithium dendrites in this embodiment is implemented according to the following steps:

[0073] 1. Preparation of artificial protective membrane polymer skeleton solution:

[0074] Adding a polymer film-forming agent, poly(vinylidene fluoride-co-hexafluoropropylene), to acetone at a rate of 10 ml of acetone per gram of the polymer film-forming agent, and magnetically stirring at 50°C until the polymer film-forming agent is completely dissolved at a stirring speed of 1000 rpm to obtain a colorless, transparent solution of the polymer skeleton of the artificial protective membrane;

[0075] 2. Preparation of artificial protective film precursor suspension:

[0076] Cobaltous oxide was added to the artificial protective membrane polymer skeleton solution, and the mass ratio of cobaltous oxide to poly (vinylidene fluoride-co-hexafluoropropylene) was controlled to be 1:99. The solution was treated with magnetic stirring at 40°C for 10 hours and ultrasonically dispersed for 1 hour to obtain a poly (vinylidene fluoride-co-hexafluoropropylene) @ 1 wt% cobaltous oxide precursor suspension.

[0077] 3. Preparation of artificial protective film:

[0078] The artificial protective film precursor suspension was evenly coated on the substrate and a film was formed evenly using a spin coater. The spin coater speed was controlled at 1000 rpm for 30 seconds. The film was then dried in a vacuum oven to obtain an artificial protective film with a thickness of 2 μm, which was recorded as poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide.

[0079] 4. Battery assembly:

[0080] Poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide is attached to the lithium metal side, and lithium iron phosphate is used as the positive electrode, thereby completing the lithium||lithium iron phosphate side electrode protection method.

[0081] Example 4: The method of adding artificial protective films to the electrodes on both sides to inhibit the growth of lithium dendrites in this embodiment is implemented according to the following steps:

[0082] 1. Preparation of artificial protective membrane polymer skeleton solution:

[0083] Adding a polymer film-forming agent, poly(vinylidene fluoride-co-hexafluoropropylene), to acetone at a rate of 10 ml of acetone per gram of the polymer film-forming agent, and magnetically stirring at 50°C until the polymer film-forming agent is completely dissolved at a stirring speed of 1000 rpm to obtain a colorless, transparent solution of the polymer skeleton of the artificial protective membrane;

[0084] 2. Preparation of artificial protective film precursor suspension:

[0085] Silica was added to the artificial protective membrane polymer skeleton solution, with the mass ratio of silica to poly(vinylidene fluoride-co-hexafluoropropylene) being controlled at 1:9. The solution was treated with magnetic stirring at 40°C for 10 hours and ultrasonically dispersed for 1 hour to obtain a poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silica precursor suspension.

[0086] Cobalt tetroxide was added to the artificial protective membrane polymer skeleton solution, and the mass ratio of cobalt tetroxide to poly (vinylidene fluoride-co-hexafluoropropylene) was controlled to be 1:99. The solution was treated with magnetic stirring at 40°C for 10 hours and ultrasonically dispersed for 1 hour to obtain a poly (vinylidene fluoride-co-hexafluoropropylene) @ 1 wt% cobalt tetroxide precursor suspension.

[0087] 3. Preparation of artificial protective film:

[0088] The artificial protective film precursor suspension was evenly coated on the substrate and a film was formed evenly using a spin coater. The spin coater speed was controlled at 1000 rpm for 30 seconds, and the film was dried in a vacuum oven to obtain an artificial protective film with a thickness of 2 μm, which was recorded as poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silicon dioxide and poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide, respectively.

[0089] 4. Battery assembly:

[0090] Poly(vinylidene fluoride-co-hexafluoropropylene)@1 wt% cobalt tetroxide is attached to the lithium metal side, and poly(vinylidene fluoride-co-hexafluoropropylene)@10 wt% silicon dioxide is attached to the lithium iron phosphate side, thereby completing the method of protecting the electrodes on both sides of lithium||lithium iron phosphate. Figure 1 These are three types of artificial protective film precursor suspensions; Figure 2 The artificial protective membranes are prepared from three artificial protective membrane precursor suspensions; Figure 3 The electrochemical impedance spectroscopy data were tested using Chenhua CHI760e equipment. Figure 4 and Figure 6 The test results for lithium||lithium batteries were tested using Shenzhen Xinweier Battery Testing System equipment; Figure 5 These are scanning electron microscope test results, using Zeiss Gemini 560 equipment.

[0091] Figure 3 Table 1 shows the electrochemical impedance spectroscopy test results for the artificial protective membrane battery systems prepared in Examples 1 and 2. The system without artificial protective membranes on both sides exhibited extremely high impedance and poor electrochemical performance. The system with single-side protection for the lithium||lithium battery exhibited much lower impedance than the system without artificial protective membranes. The system with double-side protection for the lithium||lithium battery exhibited the lowest impedance and the best electrochemical performance, with a solid electrolyte membrane impedance of only 45.62 ohms and an electron transfer resistance of only 8.42 ohms.

[0092] Table 1

[0093]

[0094] Figure 4 The long-cycle test results of the artificial protective film battery systems prepared in Examples 3 and 4 show that the system protected by the artificial protective film without adding an artificial protective film on both sides of the electrodes to inhibit lithium dendrite growth experienced rapid capacity decay during cycling, with a capacity retention rate below 80% after 245 cycles. The system with lithium||lithium iron phosphate battery protected on the lithium side showed improved cycling performance, and the system with lithium||lithium iron phosphate battery protected on both sides had the best cycling performance, with a capacity retention rate below 80% after 509 cycles.

[0095] Figure 5 These are the scanning electron microscopy results of the lithium metal negative electrode of the artificial protective film battery system prepared in Example 1 and Example 2 after long-term cycling. Figure (a) shows the cycling result of the system without artificial protective film protection, and a large amount of dendrite growth exists on the lithium metal negative electrode; Figure (b) shows the cycling result of the lithium||lithium iron phosphate battery with lithium side protection, and the lithium deposition is relatively uniform with certain holes; Figure (c) shows the cycling result of the lithium||lithium iron phosphate battery with both sides protected, and the lithium deposition is very flat, with no dendrite growth and no holes.

[0096] Figure 6 The results of long-term cycling of the artificial protective film battery systems prepared in Example 1 and Example 2 are as follows: the battery of the system without artificial protective film protection fails after 500 hours of cycling; the battery of the system with lithium||lithium battery protection on one side fails after 1100 hours of cycling; the system with lithium||lithium battery protection on both sides can still cycle stably for more than 4000 hours.

[0097] The above results show that the method of adding artificial protective film on both sides of the electrodes developed by the present invention to inhibit the growth of lithium dendrites has better protection effect than the previous method of only protecting the lithium metal negative electrode, achieving dendrite-free lithium metal deposition and having better electrochemical performance and cycle performance.

[0098] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for adding an artificial protective film on both sides of the electrodes to inhibit the growth of lithium dendrites, characterized in that The method of adding an artificial protective film on both sides of the electrodes to inhibit the growth of lithium dendrites is achieved by the following steps:

1. Preparation of artificial protective membrane polymer skeleton solution: Adding a polymer film-forming agent to an organic solvent and stirring at a temperature of 40°C to 80°C until the polymer film-forming agent is completely dissolved to obtain an artificial protective film polymer skeleton solution; 2. Preparation of artificial protective film precursor suspension: The oxide is added to the artificial protective membrane polymer skeleton solution, the mass ratio of the oxide to the polymer film-forming agent is controlled to be 0.5:9-10:9, the mixture is stirred at a temperature of 20°C-80°C, and ultrasonically dispersed to obtain an artificial protective membrane precursor suspension; 3. Preparation of artificial protective film: The artificial protective film precursor suspension is evenly coated on the substrate, and a coating machine is used to form a uniform film, and the artificial protective film is obtained after curing; 4. Battery assembly: The artificial protective film is attached to both sides of the positive electrode and the negative electrode of the lithium-ion battery, and the negative electrode is selected from metallic lithium, thereby completing the method of adding artificial protective films on both sides of the electrodes to inhibit the growth of lithium dendrites; wherein the polymer film-forming agent is one or more of poly(vinylidene fluoride-co-hexafluoropropylene), starch, maltodextrin, pullulan, okra biopolymer, moringa gum, chitosan, hyaluronic acid, sodium alginate, pectin, gelatin, gum arabic, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinylidene fluoride, polytetrafluoroethylene, polyperfluorosulfonic acid, acrylic resin, polyether, polystyrene and its copolymers, and polyvinyl chloride; The oxide is one or more of sodium oxide, potassium oxide, calcium oxide, magnesium oxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, ferroferric oxide, ferric oxide, cuprous oxide, silver oxide, lithium oxide, chromium oxide, cobalt oxide, nickel oxide, titanium oxide, zirconium oxide, silicon dioxide, arsenic trioxide, lead tetroxide, phosphorus pentoxide, iodine pentoxide, and selenium dioxide.

2. The method for inhibiting lithium dendrite growth by adding an artificial protective film to electrodes on both sides according to claim 1, characterized in that The average molecular weight Mw of the polymer film-forming agent in step 1 is 10,000 to 10,000,000.

3. The method for inhibiting lithium dendrite growth by adding an artificial protective film to electrodes on both sides according to claim 1, characterized in that In step 1, the concentration of the polymer film-forming agent in the artificial protective membrane polymer skeleton solution is 0.1 wt % to 10 wt %.

4. The method for inhibiting lithium dendrite growth by adding an artificial protective film to electrodes on both sides according to claim 1, characterized in that The organic solvent in step 1 is one or more mixed solvents selected from n-hexane, turpentine, cycloalkanes, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, ethyl acetate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, tetrahydrofuran, ether, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, formic acid, glacial acetic acid, phenol, and m-cresol.

5. The method for inhibiting lithium dendrite growth by adding an artificial protective film to electrodes on both sides according to claim 1, characterized in that In step 2, the mass ratio of the oxide to the polymer film-forming agent is controlled to be 1:9~2:

9.

6. The method for inhibiting lithium dendrite growth by adding an artificial protective film to electrodes on both sides according to claim 1, characterized in that The oxide described in step 2 is silicon dioxide or cobalt trioxide.

7. The method of adding an artificial protective film on both sides of the electrodes to inhibit the growth of lithium dendrites according to claim 1, characterized in that In step 2, the mixture is stirred at 30° C. to 50° C. for 8 to 12 hours.

8. The method of adding an artificial protective film on both sides of the electrodes to inhibit the growth of lithium dendrites according to claim 1, characterized in that The substrate described in step 3 is gold foil, platinum foil, copper foil, nickel foil, chromium foil, aluminum foil, zinc foil, iron foil, titanium foil or zirconium foil.

9. The method of adding an artificial protective film on both sides of the electrodes to inhibit the growth of lithium dendrites according to claim 1, characterized in that The thickness of the artificial protective film in step 3 is 0.5~5 μm.

10. The method for inhibiting lithium dendrite growth by adding an artificial protective film to electrodes on both sides according to claim 1, characterized in that In step 4, the positive electrode material of the lithium-ion battery is lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

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