Application of an artificial solid-electrolyte interphase film material in a negative electrode-free lithium-ion battery

Abstract

The application relates to the technical field of negative-electrode-free lithium ion batteries, and discloses application of an artificial solid-state electrolyte interface film material in a negative-electrode-free lithium ion battery, wherein the interface film is arranged on the surface of a 6-micron-thick copper foil current collector of the negative-electrode-free lithium ion battery; the interface film is prepared by coating chitin single-layer chain sheet slurry on the surface of the copper foil and drying; the slurry is prepared by reacting chitin, potassium hydroxide and an acid anhydride, wherein the molar ratio of the potassium hydroxide to the chitin is (0.1-2.7):1, and the molar ratio of the acid anhydride to the chitin is (0.5-1.5):1. The application utilizes the single-layer chain sheet of chitin to construct dense and ordered sub-nanometer limited ion channels in the film, effectively homogenizes lithium ion flux, guides lithium to uniformly and densely deposit, and inhibits lithium dendrite growth; meanwhile, the interface film has high modulus and excellent flexibility, can adapt to volume changes in the cycle process and physically isolate electrolyte, and improves the coulomb efficiency and long cycle stability of the battery.

Description

Technical Field

[0001] This invention relates to the field of negative electrode-free lithium-ion battery technology, specifically to the application of an artificial solid electrolyte interface film material in negative electrode-free lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, as indispensable energy storage devices, are gradually approaching their energy density limits based on traditional graphite anodes. To pursue higher energy densities, anode-less lithium-ion batteries are considered a promising next-generation energy storage system. In this system, lithium ions are directly deposited from the positive electrode during charging onto current collectors such as copper foil to form a lithium anode. However, in anode-less lithium-ion batteries, the deposition behavior of metallic lithium is extremely unstable during repeated charge-discharge cycles, easily inducing space charge effects and leading to the disordered growth of lithium dendrites. Simultaneously, the significant volume expansion and contraction during charging and discharging causes frequent rupture of the native solid electrolyte interface film, continuously exposing highly active metallic lithium and resulting in severe and persistent side reactions with the electrolyte. This consumes large amounts of active lithium and electrolyte, ultimately leading to low battery coulombic efficiency and rapid capacity decay.

[0003] To overcome the aforementioned challenges of interfacial instability, existing research often employs organic modification techniques such as interfacial film formation regulation and molecular structure design to modify the surface of the negative electrode current collector. However, conventional interfacial film formation regulation methods often result in increased interfacial impedance, and the formed film layer struggles to achieve both high mechanical modulus and excellent structural flexibility, failing to effectively resist dendrite penetration or adapt to the drastic volume changes during deposition and stripping. Furthermore, existing molecular structure designs struggle to simultaneously achieve high conductivity and high lithium-ion transference number, leading to uneven local ion flux. This prevents the dense deposition of lithium from the source and fails to form an effective physical barrier to block the continuous erosion by the electrolyte.

[0004] Faced with the increasingly severe challenge of petroleum-based plastic pollution, developing abundant biodegradable biomass resources, such as chitin, as alternative materials for interface modification possesses enormous environmental value and application potential. However, natural chitin, due to its dense intramolecular hydrogen bonds and high crystallinity, exhibits inherent defects such as extreme difficulty in dissolving and melting. Traditional processing and exfoliation techniques are not only difficult, energy-intensive, and inefficient, but also extremely challenging to precisely exfoliate it into sub-nanometer-scale two-dimensional structural units. This results in high material preparation costs, making it difficult to control the internal channel size and surface chemical properties of the material as needed, severely restricting its large-area uniform film formation on electrode surfaces and its large-scale commercial application in the field of electrochemical energy storage. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an application of an artificial solid electrolyte interface film material in a cathode-free lithium-ion battery, solving the problems of uneven lithium metal deposition leading to dendrite growth and severe interfacial side reactions that result in poor cycle life in cathode-free lithium-ion batteries.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The application of an artificial solid-state electrolyte interface film material in a negative electrode-free lithium-ion battery, comprising: depositing the artificial solid-state electrolyte interface film on the surface of a copper foil current collector of the negative electrode-free lithium-ion battery; the artificial solid-state electrolyte interface film is prepared by coating the surface of the copper foil current collector with a chitin monolayer chain lamellar slurry and then drying it; the chitin monolayer chain lamellar slurry is prepared by reacting raw materials containing the following molar ratio: chitin, potassium hydroxide, and acid anhydride; wherein the molar ratio of potassium hydroxide to chitin is (0.1-2.7):1, and the molar ratio of acid anhydride to chitin is (0.5-1.5):1.

[0007] By adopting the above technical solution, an artificial solid electrolyte interface film is constructed on the surface of the copper foil current collector in a negative electrode-free lithium-ion battery by using chitin monolayer chain slurry prepared by pre-swelling chitin with potassium hydroxide and reacting it with acid anhydride. Therefore, the following effects are achieved:

[0008] Chitin monolayer chains self-assemble on the copper foil surface to form dense, two-dimensional confined ion channels, the channel size of which matches the desolvation radius of lithium ions in the electrolyte. The high negative charge density of the polar functional group network on the chains generates a double-layer overlap effect, reducing the activation energy of lithium ion desolvation and promoting rapid lithium ion transport. Simultaneously, this interfacial film acts as a physical isolation layer, blocking direct contact between the liquid electrolyte and the deposited metallic lithium, suppressing the continuous reduction and decomposition side reactions of electrolyte solvent molecules, and reducing concentration polarization at the interface. This effectively induces uniform deposition of metallic lithium, avoids localized lithium dendrite puncture, and thus improves the coulombic efficiency and long-cycle stability of the electrodeless lithium-ion battery.

[0009] Preferably, the anhydride is selected from at least one of the following materials: phthalic anhydride, biphenyl-2,2'-dicarboxylic anhydride, tetraphenyl phthalic anhydride, 4-nitrophthalic anhydride, 3-fluorophthalic anhydride, 4-tert-butylphthalic anhydride, hexahydrophthalic anhydride, butylsuccinic anhydride, octylsuccinic anhydride, dodecylsuccinic anhydride, and hexadecylsuccinic anhydride.

[0010] By adopting the above technical solutions, acid anhydrides with different molecular structures are introduced with sterically hindered aromatic rings or aliphatic chain substituents, which regulates the interlayer spacing and hydrophilicity / hydrophobicity of chitin monolayers, and further optimizes the ion conduction uniformity and mechanical flexibility of the interfacial membrane.

[0011] Preferably, the solid content of the chitin monolayer chain slurry is 0.1-20%; and the coating thickness on the surface of the copper foil current collector is 0.5-50 nm.

[0012] By adopting the above technical solution, the limited solid content ensures the leveling and coating uniformity of the slurry on the current collector surface; the coating thickness of 0.5-50nm provides an extremely short lithium-ion solid phase transport path while ensuring complete physical coverage, thus avoiding the increase in battery internal impedance caused by excessive coating thickness.

[0013] Preferably, the step of setting the copper foil current collector surface specifically involves: uniformly coating the chitin monolayer chain slurry onto the surface of the copper foil current collector with a thickness of 6 μm, and drying it to obtain a copper foil current collector with a chitin monolayer chain artificial solid electrolyte interface film serving as the negative electrode; assembling the negative electrode, a commercial microporous polypropylene separator, and a positive electrode into a negative electrode-free lithium-ion battery, and injecting electrolyte during the assembly process; wherein, the active material of the positive electrode is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium sulfide, elemental sulfur, and lithium manganese iron phosphate.

[0014] By adopting the above technical solution, the polymer interface film can be compatible with a variety of electrochemical systems, especially adaptable to high-voltage oxidized cathodes (such as lithium nickel cobalt manganese oxide), achieving high energy density in a cathode-free battery architecture while maintaining the integrity of the interface physical structure.

[0015] Preferably, the amount of electrolyte added during the assembly process is 20-100 μL. The electrolyte injected during the assembly process meets one of the following conditions:

[0016] Condition 1: When the active material of the positive electrode is lithium iron phosphate, the solvent of the electrolyte is 1,3-dioxane and ethylene glycol dimethyl ether in a volume ratio of 4:1, the lithium salt is 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, and it contains 1 wt% lithium nitrate additive.

[0017] Condition 2: When the active material of the positive electrode is lithium nickel cobalt manganese oxide, the solvent of the electrolyte is diethyl carbonate and fluoroethylene carbonate in a volume ratio of 2:1, and the lithium salt is a mixture of lithium difluorooxalate borate and lithium tetrafluoroborate in a molar ratio of 5:1.

[0018] By employing the above technical solutions, suitable electrolyte solvent and lithium salt combinations are matched for cathode systems with different redox potentials. For the lithium iron phosphate system, ether solvents combined with the interfacial film improve the reversible lithium deposition rate in the low-pressure system; for the lithium nickel cobalt manganese oxide system, ester solvents combined with mixed lithium salts effectively suppress the continuous decomposition reaction of the electrolyte under high oxidation potential through the physical isolation synergy of the interfacial film.

[0019] The application of an artificial solid electrolyte interface membrane material in a negative electrode-free lithium-ion battery further includes the following steps: mixing chitin, potassium hydroxide, and dimethyl sulfoxide for pre-swelling; adding acid anhydride to the pre-swelling system and continuously stirring the reaction; after the reaction is completed, washing the product with anhydrous ethanol and dimethyl sulfoxide, then adding sodium hydroxide solution with a pH of 11, stirring, centrifuging, collecting the supernatant to obtain a chitin monolayer chain dispersion; adjusting the dispersion to obtain the chitin monolayer chain slurry.

[0020] By adopting the above technical solution, the reaction mechanism and exfoliation mechanism of the preparation method of the present invention include the following stages:

[0021] Phase 1, Solvent-induced pre-swelling: Potassium hydroxide, acting as a proton acceptor, works synergistically with dimethyl sulfoxide solvent to disrupt the dense hydrogen bond network within and between chitin molecules, causing the chitin crystal structure to relax moderately and exposing the reactive sites of the internal fibrils.

[0022] Stage Two, Steric Hazard-Driven Liquid-Phase Self-Exfoliation: Esterification occurs after the addition of acid anhydride. The acid anhydride group is grafted onto the hydroxyl groups of the chitin molecular chain, introducing side chain structures and polar carboxyl groups. The steric hindrance effect generated by the grafted group and the electrostatic repulsion between the polar carboxyl groups overcome the van der Waals forces between chitin units, promoting the spontaneous exfoliation of chitin from the macroscopic bulk.

[0023] Phase 3, alkaline phase separation and purification: After washing with ethanol to remove non-reactants, an alkaline solution is added to promote the complete dissociation of the grafted carboxyl groups into carboxylic acid anions, maximizing electrostatic repulsion and thoroughly dispersing chitin into atomically thin monolayer sub-nanoscale chains in the liquid phase. Centrifugation separates and removes incompletely peeled multilayer fragments, and the supernatant is the purified monolayer chain dispersion. This process replaces traditional high-energy-consuming mechanical shearing with gentle chemical modification, achieving extremely low-energy-consumption size reduction of biomass building blocks.

[0024] Preferably, the pre-swelling treatment conditions are: stirring at room temperature for 24 hours, and continuous stirring reaction time after adding acid anhydride for 5-10 days.

[0025] By adopting the above technical solution, the pre-swelling at room temperature for 24 hours ensures that the solvent molecules fully penetrate into the interstitial spaces of chitin crystals; the esterification reaction time of 5-10 days ensures that the anhydride and chitin undergo sufficient chemical grafting, while avoiding the degradation and breakage of the chitin main chain polymer backbone due to excessive reaction time.

[0026] Preferably, the stirring time after adding the sodium hydroxide solution with a pH of 11 is 30 minutes, and the centrifugation conditions are centrifugation at 9800 r / min for 15 minutes.

[0027] By adopting the above technical solution, 30 minutes of alkaline stirring allows electrostatic repulsion to be uniformly established in the system; a rotation speed of 9800 r / min and a centrifugation parameter of 15 minutes provide an appropriate physical centrifugal force field, accurately settling large-sized fiber bundles and unpeeled oligomers, ensuring the uniformity of the thickness of the extracted chitin monolayer chains.

[0028] This invention provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery. It offers the following advantages:

[0029] 1. This invention prepares a chitin monolayer chain slurry by reacting chitin, potassium hydroxide, and acid anhydride, and then coats it onto the surface of a current collector to construct an artificial solid electrolyte interface film. Dense and ordered interlayer confined ion channels are formed inside the film. This monolayer chain structure carries a high density of negative charge, which can repel electrolyte anions and allow only lithium ions to pass through rapidly, thereby improving the ion diffusion rate and homogenizing the local ion flux. This weakens the space charge effect that causes dendrite growth from the source, guides the uniform and dense deposition of lithium metal on the surface of the current collector, and improves the rate performance and deposition morphology stability of the electrodeless battery.

[0030] 2. The artificial solid electrolyte interface membrane prepared by this invention has both high mechanical modulus and excellent structural flexibility. The high-modulus polymer network can play a physical barrier role, effectively resisting the puncture damage of uneven deposits; while the good flexibility ensures that the membrane layer always maintains a tight interfacial contact with the underlying metal during repeated charge and discharge cycles, fully adapting to the volume expansion and contraction caused by the charge and discharge process. At the same time, as a dense physical barrier layer, this interface membrane blocks the direct contact between the liquid electrolyte and the highly active metal interface, effectively suppressing continuous interfacial side reactions and improving the coulombic efficiency and long-term cycle life of the battery.

[0031] 3. The material preparation and battery assembly method provided by this invention has mild conditions and high potential for large-scale application. By precisely controlling the ratio of reaction raw materials such as potassium hydroxide and acid anhydride, it is possible to achieve precise control over the degree of chitin chain stripping, the content of modified groups, and the internal channel size, thereby meeting the on-demand interface design requirements. Utilizing liquid-phase pre-swelling combined with in-situ reaction stripping technology, the slurry can be directly coated and dried into a film on the electrode surface in one step, without the need for complex processing equipment, reducing energy consumption and process complexity. This lays the technological foundation for the large-area uniform film formation and practical promotion of abundant biomass resources in the field of electrochemical energy storage. Attached Figure Description

[0032] Figure 1 This is a scanning electron microscope (SEM) schematic diagram of the surface morphology of the negative electrode current collector obtained after Example 1 of the present invention;

[0033] Figure 2This is a scanning electron microscope (SEM) schematic diagram of the surface morphology of the negative electrode current collector obtained in Comparative Example 1 of the present invention.

[0034] Figure 3 This is a schematic diagram of the rate performance curves of the electrodeless lithium-ion battery with lithium iron phosphate as the positive electrode material at different rates according to the present invention.

[0035] Figure 4 This is one of the schematic diagrams of the cycling curve of the electrodeless lithium-ion battery with NCM811 as the positive electrode material of the present invention after 225 cycles at 0.2C;

[0036] Figure 5 This is the second schematic diagram of the cycling curve of the electrodeless lithium-ion battery with NCM811 as the positive electrode material of the present invention after 225 cycles at 0.2C;

[0037] Specific capacity (usually referring to the amount of electricity that a battery can release per unit mass or unit volume) is measured in mAh / g here. -1 Or mAh / g (milliampere-hours per gram);

[0038] Cyclenumber: The number of cycles (or number of rounds) indicates the number of times the battery has undergone charge and discharge cycles;

[0039] Coulombicefficiency: Coulomb efficiency refers to the ratio of a battery's discharge capacity to its charge capacity during the same cycle. It is usually expressed as a percentage (%) and reflects the reversibility of the battery during cycling.

[0040] 0.1C, 0.2C, 1C...5C, etc.: Charge / discharge rate (C-rate), which is a measure of the charging and discharging current. 1C represents the current required to fully charge or discharge the battery's nominal capacity within one hour. The larger the number, the faster the charging and discharging speed (i.e., high current charging and discharging). Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Preparation Examples 1-14:

[0043] Preparation Example 1:

[0044] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0045] Preparation Example 2:

[0046] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Octylsuccinic anhydride was then added to the pre-swelled system, maintaining a molar ratio of chitosan to octylsuccinic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0047] Preparation Example 3:

[0048] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Biphenyl-2,2'-dicarboxylic anhydride was added to the pre-swelled system, maintaining a molar ratio of chitosan to biphenyl-2,2'-dicarboxylic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0049] Preparation Example 4:

[0050] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1.5:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0051] Preparation Example 5:

[0052] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1.5, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0053] Preparation Example 6:

[0054] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 2:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0055] Preparation Example 7:

[0056] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelled system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 5 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0057] Preparation Example 8:

[0058] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 10 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0059] Preparation Example 9:

[0060] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 0.1%.

[0061] Preparation Example 10:

[0062] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 10%.

[0063] Preparation Example 11:

[0064] 80 mg of chitosan, 20 mg of potassium hydroxide, and 20 mL of dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.9:1. The mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. Then, 80 g of sodium hydroxide solution with a pH of 11 was added, and the mixture was stirred for 30 minutes. The mixture was then centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 20%.

[0065] Preparation Example 12:

[0066] Chitosan, potassium hydroxide, and dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 0.1:1. The mixture was stirred at room temperature for 24 hours to allow for pre-swelling. Phthalic anhydride was then added to the pre-swelled system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide. A sodium hydroxide solution with a pH of 11 was then added, and the mixture was stirred for 30 minutes. The mixture was then centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0067] Preparation Example 13:

[0068] Chitosan, potassium hydroxide, and dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 1.5:1, and the mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide, followed by the addition of sodium hydroxide solution with a pH of 11. The mixture was stirred for 30 minutes, centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0069] Preparation Example 14:

[0070] Chitosan, potassium hydroxide, and dimethyl sulfoxide were mixed, with a molar ratio of potassium hydroxide to chitosan of 2.7:1, and the mixture was stirred at room temperature for 24 hours for pre-swelling. Phthalic anhydride was then added to the pre-swelling system, maintaining a molar ratio of chitosan to phthalic anhydride of 1:1, and the reaction was continued with stirring for 7 days. After the reaction was complete, the product was washed with anhydrous ethanol and dimethyl sulfoxide, followed by the addition of sodium hydroxide solution with a pH of 11. The mixture was stirred for 30 minutes, centrifuged at 9800 rpm for 15 minutes, and the supernatant was collected to obtain a chitosan monolayer chain dispersion. This dispersion was adjusted to prepare a slurry with a solid content of 5%.

[0071] Examples 1-15:

[0072] Example 1:

[0073] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0074] The chitin monolayer chain slurry prepared in Preparation Example 1 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL. The solvent used in the electrolyte was 1,3-dioxane and ethylene glycol dimethyl ether (volume ratio 4:1), the lithium salt was 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, and it contained 1 wt% lithium nitrate additive.

[0075] Example 2:

[0076] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0077] The chitin monolayer chain slurry obtained in Preparation Example 2 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0078] Example 3:

[0079] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0080] The chitin monolayer chain slurry obtained in Preparation Example 3 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0081] Example 4:

[0082] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0083] The chitin monolayer chain slurry obtained in Preparation Example 4 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0084] Example 5:

[0085] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0086] The chitin monolayer chain slurry obtained in Preparation Example 5 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0087] Example 6:

[0088] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0089] The chitin monolayer chain slurry obtained in Preparation Example 7 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0090] Example 7:

[0091] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0092] The chitin monolayer chain slurry obtained in Preparation Example 8 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0093] Example 8:

[0094] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0095] The chitin monolayer chain slurry obtained in Preparation Example 1 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 0.5 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0096] Example 9:

[0097] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0098] The chitin monolayer chain slurry obtained in Preparation Example 1 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 50 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0099] Example 10:

[0100] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0101] The chitin monolayer chain slurry obtained in Preparation Example 9 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0102] Example 11:

[0103] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0104] The chitin monolayer chain slurry obtained in Preparation Example 10 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0105] Example 12:

[0106] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0107] The chitin monolayer chain slurry obtained in Preparation Example 12 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0108] Example 13:

[0109] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0110] The chitin monolayer chain slurry obtained in Preparation Example 13 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 75 μL, and the electrolyte composition was the same as in Example 1.

[0111] Example 14:

[0112] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0113] The chitin monolayer chain slurry obtained in Preparation Example 1 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 20 μL, and the electrolyte composition was the same as in Example 1.

[0114] Example 15:

[0115] This embodiment provides an application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, including the following steps:

[0116] The chitin monolayer chain slurry obtained in Preparation Example 1 was uniformly coated onto the surface of a copper foil current collector with a thickness of 6 μm. After drying, the coating thickness on the copper foil surface was controlled to be 30 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface film. This negative electrode, a commercial microporous polypropylene separator, and a lithium iron phosphate positive electrode were assembled into a negative electrode-free lithium-ion battery. The amount of electrolyte added during the assembly process was 100 μL, and the electrolyte composition was the same as in Example 1.

[0117] Comparative Examples 1-7:

[0118] Comparative Example 1:

[0119] Compared with Example 1, the difference is that the surface of the negative electrode current collector is not coated with any coating, and a bare copper foil with a thickness of 6μm is directly used as the negative electrode sheet, while the rest are the same.

[0120] Comparative Example 2:

[0121] Compared with Example 1, the difference is that the surface of the negative electrode current collector is coated with a polyvinylidene fluoride (PVDF) polymer coating, otherwise they are the same.

[0122] Comparative Example 3:

[0123] Compared with Example 1, the difference is that the slurry prepared in Preparation Example 6 was used for coating (i.e., the molar ratio of chitin to phthalic anhydride in the preparation process was 2:1), and all other aspects are the same.

[0124] Comparative Example 4:

[0125] Compared with Example 1, the difference is that the coating thickness on the copper foil surface is controlled to be 100 nm, while the rest are the same.

[0126] Comparative Example 5:

[0127] Compared with Example 1, the difference is that the slurry prepared in Preparation Example 11 was used for coating (i.e., the slurry with a solid content of 20% was prepared by adjusting the dispersion), and all other aspects are the same.

[0128] Comparative Example 6:

[0129] Compared with Example 1, the difference is that the slurry prepared in Preparation Example 14 was used for coating (i.e., the molar ratio of potassium hydroxide to chitin in the preparation process was 2.7:1), and all other aspects are the same.

[0130] Comparative Example 7:

[0131] Compared with Example 1, the difference is that the amount of electrolyte added during battery assembly is 10 μL, while the rest are the same.

[0132] Application Examples 1-4:

[0133] Application Example 1:

[0134] This application example provides the use of an artificial solid electrolyte interface membrane material in a negative electrode-less lithium-ion battery, including the following assembly steps: A chitin monolayer chain slurry with a solid content of 10% is coated onto the surface of a copper foil current collector. After drying, the coating thickness is controlled to be 50 nm, thus obtaining a negative electrode sheet with a chitin monolayer chain artificial solid electrolyte interface membrane. A lithium iron phosphate positive electrode sheet is prepared by mixing lithium iron phosphate, conductive carbon black, and a binder in a mass ratio of 93:3:4. The above negative electrode sheet, a commercial microporous polypropylene separator, and the lithium iron phosphate positive electrode sheet are assembled into a 2032 type button battery. During assembly, 75 μL of electrolyte is injected. The electrolyte solvent is 1,3-dioxane and ethylene glycol dimethyl ether (volume ratio 4:1), the lithium salt is 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, and it contains 1 wt% lithium nitrate additive.

[0135] Application Example 2:

[0136] This application example provides the use of an artificial solid electrolyte interface membrane material in a negative electrode-less lithium-ion battery, including the following assembly steps: A chitin monolayer chain slurry with a solid content of 10% is coated onto the surface of a copper foil current collector. After drying, the coating thickness is controlled to be 50 nm, thus obtaining a negative electrode with a chitin monolayer chain artificial solid electrolyte interface membrane. A positive electrode is prepared using lithium nickel cobalt manganese oxide (NCM811) with a lithium loading of approximately 6 mg. The above negative electrode, a commercially available microporous polypropylene separator, and the lithium nickel cobalt manganese oxide positive electrode are assembled into a 2032 type button cell. During assembly, 75 μL of electrolyte is injected. The solvent used in the electrolyte is diethyl carbonate and fluoroethylene carbonate (volume ratio 2:1), and the lithium salt is a mixture of lithium difluorooxalate borate and lithium tetrafluoroborate in a molar ratio of 5:1.

[0137] Application Example 3:

[0138] This application example provides the use of an artificial solid-state electrolyte interface film material in a negative electrode-less lithium-ion battery, including the following assembly steps: A pre-coated copper foil with a 30nm thick chitin monolayer chain artificial solid-state electrolyte interface film is prepared using the same process as in Example 1, and used as the negative electrode. A lithium iron phosphate positive electrode is cut to a size of 4cm × 6cm. The above-mentioned negative electrode, a commercial microporous polypropylene separator, and the cut lithium iron phosphate positive electrode are stacked and assembled to form a pouch battery. During assembly, 12g of electrolyte is injected. The electrolyte solvent is 1,3-dioxane and ethylene glycol dimethyl ether (volume ratio 4:1), the lithium salt is 1mol / L lithium bis(trifluoromethanesulfonyl)imide, and it contains 1wt% lithium nitrate additive.

[0139] Application Example 4:

[0140] This application example provides the use of an artificial solid-state electrolyte interface film material in a negative electrode-less lithium-ion battery, including the following assembly steps: A pre-coated copper foil with a 30nm thick chitin monolayer chain artificial solid-state electrolyte interface film is prepared using the same process as in Example 1, and used as the negative electrode. A lithium nickel cobalt manganese oxide (NCM811) positive electrode is cut to a size of 4cm × 6cm. The above-mentioned negative electrode, a commercial microporous polypropylene separator, and the cut lithium nickel cobalt manganese oxide positive electrode are stacked and assembled to form a pouch battery. During the assembly process, 12g of electrolyte is injected. The solvent of the electrolyte is diethyl carbonate and fluoroethylene carbonate (volume ratio 2:1), and the lithium salt is a mixture of lithium difluorooxalate borate and lithium tetrafluoroborate in a molar ratio of 5:1.

[0141] Test Examples 1-4:

[0142] Test Example 1:

[0143] Experimental instructions and test procedures:

[0144] The negative electrode-free lithium-ion batteries assembled in Example 1 and Comparative Example 1 were connected to a battery cycle testing system. The first charge-discharge cycle was performed at an ambient temperature of 25°C and a current density of 0.1C for activation. The deposition surface capacity was then set to 1.0 mAh / cm². 2 Constant current charging was performed to reduce and deposit lithium ions onto the surface of the negative electrode current collector. After the charge-discharge cycle, the battery was transferred to an argon-filled glove box for disassembly, where the water and oxygen content was controlled below 0.1 ppm. The negative electrode with deposited metallic lithium was removed and cleaned three times with dimethyl carbonate solvent to remove residual electrolyte and unreacted lithium salts. It was then allowed to dry naturally in the glove box atmosphere. Electrode samples of appropriate size were cut and transferred to the scanning electron microscope sample chamber via a vacuum transfer box. The microstructure of the electrode surface was observed under accelerating voltages of 5 kV to 10 kV. Multiple samples were taken from different areas of the electrode using a matching three-dimensional surface morphology analyzer or confocal microscope to measure the surface roughness and protrusion height parameters.

[0145] Experimental data:

[0146] Table 1. Quantitative Measurement Data of Lithium Deposition Microstructure on the Anode Surface of Example 1 and Comparative Example 1

[0147] Test sample Sampling area number Surface roughness Ra (nm) Maximum dendrite protrusion height (μm) Local deposition layer thickness (μm) Example 1 Area A 34.21 Not detected 4.81 Example 1 Area B 28.74 0.12 5.03 Example 1 Area C 41.55 0.08 4.92 Comparative Example 1 Area A 487.62 12.45 7.64 Comparative Example 1 Area B 612.39 18.72 3.21 Comparative Example 1 Area C 534.81 15.09 9.87

[0148] Test conclusion:

[0149] See attached document Figure 1 and attached Figure 2Based on the aforementioned quantitative test data of microstructure, the negative electrode surface in Example 1 exhibits a flat and smooth lithium metal deposition morphology. The surface roughness values ​​of each sampling area are low and fluctuate little, and no micron-sized dendrite protrusions were found. The overall deposition layer thickness remains highly consistent. In contrast, the surface roughness value of the bare copper foil in Comparative Example 1 shows an order-of-magnitude increase, with significant local deposition layer thickness deviations in different sampling areas, accompanied by irregular protrusions reaching up to tens of micrometers in size. The above data confirm that the chitin monolayer chain coating effectively constructs an artificial solid electrolyte interface film on the surface of the negative electrode current collector. This interface film possesses a sub-nanometer two-dimensional chain structure, which spatially confines and homogenizes the lithium ion transport flux across the interface during battery operation. This polymer layer structure balances the electric field distribution at the current collector interface, avoiding localized excessive reduction and enrichment of lithium ions at morphological defects or electric field concentrations on the copper foil surface. From a kinetic perspective, it suppresses the nucleation and longitudinal growth of lithium dendrites, achieving high-density two-dimensional planar deposition of lithium metal in a negative electrode-free architecture.

[0150] Test 2:

[0151] The assembled negative electrode-less lithium-ion batteries of each embodiment and comparative example were moved into a constant temperature test chamber, with the ambient temperature set and maintained at 25±2℃. The batteries were allowed to stand for 12 hours to ensure the electrolyte fully wetted the electrodes and separator. Subsequently, each battery group was connected to the battery charge-discharge test system. The charge-discharge voltage window was set to 2.5V to 4.0V. A constant current charge-discharge mode was used, with a current density of 0.1C for charge-discharge cycle testing. The initial discharge specific capacity of each battery was recorded, and capacity data was continuously collected during the cyclic charge-discharge process. The discharge specific capacity values ​​for the 10th, 50th, and 100th cycles were extracted. The capacity retention percentage at each stage was calculated by dividing the discharge specific capacity of the nth cycle by the initial discharge specific capacity.

[0152] Experimental data:

[0153] Table 2. Test data on capacity retention during room temperature cycling of Examples 1 to 15 and Comparative Examples 1 to 7

[0154] Test group Capacity retention rate after 10 cycles (%) Capacity retention rate after 50 cycles (%) Capacity retention rate after 100 cycles (%) Example 1 98.24 95.37 92.11 Example 2 97.51 93.12 88.46 Example 3 98.03 94.65 89.72 Example 4 96.87 91.24 85.39 Example 5 97.12 92.56 86.84 Example 6 95.94 89.41 81.27 Example 7 96.48 90.73 83.51 Example 8 94.25 86.38 77.82 Example 9 96.16 91.52 87.26 Example 10 95.53 88.94 79.45 Example 11 97.38 92.81 88.13 Example 12 94.86 87.65 78.59 Example 13 96.52 91.87 86.94 Example 14 95.14 88.23 76.48 Example 15 97.89 94.16 90.55 Comparative Example 1 85.42 71.25 54.67 Comparative Example 2 88.17 74.58 58.21 Comparative Example 3 86.73 72.84 56.15 Comparative Example 4 89.31 76.42 59.43 Comparative Example 5 87.56 73.91 57.88 Comparative Example 6 86.29 72.16 55.32 Comparative Example 7 84.85 69.57 54.14

[0155] Test conclusion:

[0156] According to the cycle test results in Table 2, the capacity retention rate of the Example Group after 100 cycles ranged from 76.48% to 92.11%, which was higher than that of the Comparative Example Group (54.14% to 59.43%). Comparative Example 1 used untreated bare copper foil as the negative electrode current collector. During repeated charge and discharge cycles, the deposited metallic lithium directly contacted the liquid electrolyte, causing a side reaction that continuously consumed the active lithium and electrolyte solvent in the system. Simultaneously, a large amount of electrically isolated dead lithium was generated, leading to rapid and irreversible capacity decay of the battery.

[0157] This embodiment constructs an artificial solid electrolyte interface film by coating a copper current collector surface with a single layer of chitin chains. This polymer interface layer blocks direct physical contact between metallic lithium and the liquid electrolyte, suppressing parasitic side reactions at the electrode interface. The polar functional groups on the chitin molecular chains participate in the solvation layer dissociation process of lithium ions, increasing the lithium ion migration number and transport rate at the interface. This structural design regulates the ion flux distribution on the current collector surface, enabling uniform lithium ion deposition and reducing the accumulation of volume expansion stress during charge-discharge cycles. This mechanism maintains the structural integrity of the electrode-current collector interface, reduces the loss rate of active material, and thus achieves high capacity retention during long-term room-temperature charge-discharge cycles. Data from embodiments with varying parameters such as anhydride type, slurry solid content, coating thickness, and electrolyte injection amount show that the interface film can provide protection within specific process parameter ranges. However, comparative data deviating from the preferred range show a decrease in capacity retention, demonstrating the rationality and necessity of the parameter range settings in this technical solution.

[0158] Test 3:

[0159] The negative electrode-less lithium-ion button cell assembled in Application Example 1, containing a chitin monolayer chain artificial solid electrolyte interface film, was selected as the test object. A blank button cell without any coating process applied to the surface of the negative electrode current collector and with the same assembly conditions as Application Example 1 was selected as a control. The batteries were connected to a multi-channel battery testing system and left to stand for 10 hours at an ambient temperature of 25±2℃ to allow the internal materials to reach thermal equilibrium and the electrolyte to be fully wetted. The voltage range for the charge-discharge test was set to 2.5V to 4.0V. A stepped rate charge-discharge program was performed on both sets of batteries, with the current density stages set sequentially as 0.1C, 0.2C, 0.3C, 0.4C, 1C, 2C, 3C, 4C, and 5C. Each current density stage was continuously subjected to 5 charge-discharge cycles. The test system recorded the discharge capacity data in real time during each cycle and calculated the corresponding discharge specific capacity based on the mass of lithium iron phosphate active material in the positive electrode. The discharge specific capacity of the last cycle of each rate stage was extracted as the representative value for that stage.

[0160] Experimental data:

[0161] Table 3. Discharge specific capacity test data of Application Example 1 and blank control group at each step rate.

[0162] Testing phase Current density Application Example 1: Discharge Specific Capacity (mAh / g) Discharge specific capacity (mAh / g) of blank control group Phase 1 0.1C 158.42 97.16 Phase 2 0.2C 151.78 64.39 Phase 3 0.3C 146.91 21.05 Phase 4 0.4C 142.34 1.12 Phase 5 1C 134.87 0.00 Phase 6 2C 121.56 0.00 Phase 7 3C 108.23 0.00 Phase 8 4C 92.48 0.00 Phase 9 5C 76.19 0.00

[0163] Test conclusion:

[0164] See attached document Figure 3The rate test data reflects the ion transport kinetics of the battery under different current load conditions. At a low current density of 0.1C, Application Example 1 exhibits a discharge specific capacity of nearly 160 mAh / g, while the blank control group has a capacity of less than 100 mAh / g. As the current density increases stepwise, the discharge specific capacity of the blank control group decreases significantly, dropping to 1.12 mAh / g at 0.4C, thus losing its energy storage function. Application Example 1, even at a high rate of 5C with the current density increased, still maintains an effective discharge capacity output of 76.19 mAh / g.

[0165] The blank control group failed as the current density increased because of the high ion transport barrier at the bare copper foil interface. Under high current conditions, the reduction deposition rate of lithium ions at the current collector interface is much slower than their migration rate in the electrolyte liquid phase, leading to severe concentration polarization on the electrode surface. This causes the overpotential to increase rapidly and reach the discharge cutoff voltage, blocking capacity release. Application Example 1 introduced a polymer film composed of chitin monolayer chains at the negative electrode interface. This film contains a large network of polar functional groups, which participate in altering the solvation structure of lithium ions and reducing the activation energy of lithium ion desolvation. This sub-nanometer two-dimensional chain structure provides dense lithium ion conduction sites on the current collector surface, constructing a low-impedance interfacial transport channel. This microstructure effectively alleviates ion depletion on the electrode surface and reduces charge transfer impedance and interfacial polarization under continuous high-current charge-discharge conditions, thereby maintaining the battery's discharge capacity and electrochemical stability at high rates.

[0166] Furthermore, simultaneous rate and cycle tests were conducted on the lithium iron phosphate pouch cell without a negative electrode assembled in Application Example 3. The test results showed that even under pouch cell conditions with an electrode area increased to 4cm × 6cm and limited electrolyte injection, the negative electrode equipped with a chitin monolayer chain artificial solid electrolyte interface film still maintained good ion conduction uniformity. No micro-short circuits or rapid capacity decay caused by localized polarization were observed in the pouch cell during the tests, further confirming the structural integrity of the interface film under large-area coating processes and its effectiveness in suppressing localized lithium dendrite growth.

[0167] Test 4:

[0168] The negative electrode-less lithium-ion button cell assembled in Application Example 2 was selected as the experimental group, while a button cell assembled with identical parameters but without a chitin single-layer chain coating on the negative electrode copper foil was selected as the blank control group. Both groups of batteries were placed in a constant temperature test environment of 25±2℃ for 12 hours. The batteries were connected to a multi-channel battery charge-discharge tester, with the test voltage window set to 2.8V to 4.3V. Constant current and constant voltage charging and constant current discharging modes were used, with the charging and discharging current densities set to 0.2C. Continuous charge-discharge cycle tests were performed on both groups of batteries, with a total of 225 cycles. The test system automatically recorded the constant current discharge specific capacity of each cycle and calculated the coulombic efficiency of each cycle based on the ratio of discharge capacity to charge capacity. Specific test data for the 1st, 50th, 100th, 150th, 200th, and 225th cycles were extracted.

[0169] Experimental data:

[0170] Table 4. Long-cycle stability and coulombic efficiency test data of Application Example 2 and blank control group.

[0171] Testing phase Application Example 2: Discharge Specific Capacity (mAh / g) Application Example 2: Coulomb efficiency (%) Discharge specific capacity (mAh / g) of blank control group Coulomb efficiency (%) in blank control group First cycle 196.42 87.51 194.83 85.34 50th cycle 185.37 99.12 138.61 95.78 100th cycle 176.84 99.34 86.29 91.05 150th cycle 164.15 99.27 39.42 80.16 200th cycle 151.08 99.41 11.57 62.83 225th cycle 146.93 99.18 3.14 41.29

[0172] Test conclusion:

[0173] See attached document Figure 4 and attached Figure 5 According to long-cycle test data, after 225 cycles, the discharge specific capacity of Application Example 2 remained at 146.93 mAh / g, and the coulombic efficiency during the cycling process rapidly increased after the first cycle and stabilized at over 99%. The blank control group showed a decline in capacity in the early stage of cycling, dropping to 86.29 mAh / g by the 100th cycle, and basically lost its energy storage capacity after 200 cycles, accompanied by a sharp decline in coulombic efficiency.

[0174] The aforementioned data discrepancies reveal the interfacial stability mechanism of the chitin monolayer chain artificial solid electrolyte interfacial film in a high-voltage cathode system. In a high-voltage nickel-cobalt-manganese oxide system without a negative electrode, the liquid electrolyte is prone to decomposition under high redox potential differences. The bare copper electrode surface in the blank control group cannot constrain the non-uniform growth of deposited lithium, and the generated dendrites have a high specific surface area, continuously triggering the reduction and decomposition reaction of the electrolyte. This process consumes a large amount of the limited active lithium source and liquid electrolyte in the system, producing electrically insulating dead lithium, leading to fluctuations in coulombic efficiency and irreversible capacity decay.

[0175] In Application Example 2, the chitin monolayer lamellar interface layer constructed on the negative electrode surface possesses a dense two-dimensional structure and physical toughness, enabling it to adapt to volume changes during repeated lithium deposition and stripping processes, maintaining the mechanical integrity of the interface structure. This polymer layer effectively isolates the highly active lithium metal from the physical contact with the liquid electrolyte, suppressing interfacial side reactions caused by continuous electrolyte consumption. This interfacial isolation reduces the rate of dead lithium formation, ensuring reversible lithium conversion during charge and discharge. By suppressing parasitic reactions and the risk of lithium dendrite penetration, the battery maintains high coulombic efficiency and discharge capacity during long-cycle operation, achieving a long cycle life in a high-energy-density lithium nickel cobalt manganese oxide system without a negative electrode architecture.

[0176] Meanwhile, long-cycle verification was conducted on the pouch cell assembled with a high-voltage nickel-cobalt-manganese oxide cathode system, corresponding to Application Example 4. Test results showed that the pouch cell in Application Example 4 maintained high capacity retention and coulombic efficiency during long-cycle operation, and effectively suppressed electrolyte decomposition and gas bulging phenomena commonly found in conventional ternary pouch cells without a negative electrode. These results indicate that the polymer interface layer can act as a physical and chemical barrier in the actual operating environment of high-capacity, high-energy-density systems, effectively blocking the continuous parasitic reactions between highly oxidized cathode leachates and liquid electrolyte with deposited lithium metal, demonstrating promising prospects for large-scale engineering applications.

Claims

1. The application of an artificial solid electrolyte interface film material in a negative electrode-free lithium-ion battery, characterized in that, include: The artificial solid electrolyte interface film is disposed on the surface of the copper foil current collector of the negative electrode-free lithium-ion battery; The artificial solid electrolyte interface membrane is made by coating the copper foil current collector surface with chitin monolayer chain slurry and then drying it. The chitin monolayer chain slurry is prepared by reacting raw materials containing the following molar ratio: chitin, potassium hydroxide and acid anhydride; The molar ratio of potassium hydroxide to chitin is (0.1-2.7):1, and the molar ratio of acid anhydride to chitin is (0.5-1.5):

1.

2. The application of the artificial solid electrolyte interface film material according to claim 1 in a negative electrode-free lithium-ion battery, characterized in that, The anhydride is selected from at least one of the following materials: phthalic anhydride, biphenyl-2,2'-dicarboxylic anhydride, tetraphenyl phthalic anhydride, 4-nitrophthalic anhydride, 3-fluorophthalic anhydride, 4-tert-butylphthalic anhydride, hexahydrophthalic anhydride, butylsuccinic anhydride, octylsuccinic anhydride, dodecylsuccinic anhydride, and hexadecylsuccinic anhydride.

3. The application of the artificial solid electrolyte interface film material according to claim 1 in a negative electrode-free lithium-ion battery, characterized in that, The solid content of the chitin monolayer chain slurry is 0.1-20%.

4. The application of the artificial solid electrolyte interface film material according to claim 1 in a negative electrode-free lithium-ion battery, characterized in that, The coating thickness on the surface of the copper foil current collector is 0.5-50 nm.

5. The application of the artificial solid electrolyte interface film material according to claim 1 in a negative electrode-free lithium-ion battery, characterized in that, The specific steps for setting the copper foil current collector surface are as follows: The chitin monolayer chain slurry is uniformly coated on the surface of the copper foil current collector with a thickness of 6μm, and after drying, a copper foil current collector with a chitin monolayer chain artificial solid electrolyte interface film as the negative electrode is obtained. The negative electrode, commercial microporous polypropylene separator, and positive electrode are assembled into a negative electrode-free lithium-ion battery, and electrolyte is injected during the assembly process. The active material of the positive electrode is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium sulfide, elemental sulfur, and lithium manganese iron phosphate.

6. The application of the artificial solid electrolyte interface film material according to claim 5 in a negative electrode-free lithium-ion battery, characterized in that, The amount of electrolyte added during the assembly process is 20-100 μL.

7. The application of the artificial solid electrolyte interface film material according to claim 5 in a negative electrode-free lithium-ion battery, characterized in that, The electrolyte injected during the assembly process meets one of the following conditions: Condition 1: When the active material of the positive electrode is lithium iron phosphate, the solvent of the electrolyte is 1,3-dioxane and ethylene glycol dimethyl ether in a volume ratio of 4:1, the lithium salt is 1 mol / L lithium bis(trifluoromethanesulfonyl)imide, and it contains 1 wt% lithium nitrate additive. Condition 2: When the active material of the positive electrode is lithium nickel cobalt manganese oxide, the solvent of the electrolyte is diethyl carbonate and fluoroethylene carbonate in a volume ratio of 2:1, and the lithium salt is a mixture of lithium difluorooxalate borate and lithium tetrafluoroborate in a molar ratio of 5:

1.

8. The application of the artificial solid electrolyte interface film material according to claim 5 in a negative electrode-free lithium-ion battery, characterized in that, The steps for preparing chitin monolayer chain slurry are as follows: Chitosan, potassium hydroxide, and dimethyl sulfoxide were mixed and pre-swollen. Add acid anhydride to the pre-swollen system and continue stirring to react; After the reaction was completed, the product was washed with anhydrous ethanol and dimethyl sulfoxide, and then sodium hydroxide solution with a pH of 11 was added. The mixture was stirred, centrifuged, and the supernatant was collected to obtain a chitin monolayer chain dispersion. The dispersion was adjusted to obtain the chitin monolayer chain slurry.

9. The application of the artificial solid electrolyte interface film material according to claim 8 in a negative electrode-free lithium-ion battery, characterized in that, The pre-swelling treatment conditions are: stirring at room temperature for 24 hours, followed by continuous stirring for 5-10 days after the addition of acid anhydride.

10. The application of the artificial solid electrolyte interface film material according to claim 8 in a negative electrode-free lithium-ion battery, characterized in that, The stirring time after adding the sodium hydroxide solution with a pH of 11 is 30 minutes, and the centrifugation conditions are centrifugation at 9800 r / min for 15 minutes.

Images