Wood-based carbon quantum dot as efficient negative electrode material of Li4Ti5O12 battery

Abstract

The invention provides a wood-based carbon quantum dot as an efficient negative electrode material of a Li4Ti5O12 battery, and relates to the technical field of Li4Ti5O12 battery negative electrode materials, the wood-based carbon quantum dot comprises Li4Ti5O12 nanoparticles and the wood-based carbon quantum dot, the wood-based carbon quantum dot is uniformly loaded or adsorbed on the surfaces of the Li4Ti5O12 nanoparticles and is filled in gaps of the nanoparticles, and an efficient electron and lithium titanate transmission network is formed. The waste wood is used as a raw material, the wood base is prepared through a hydrothermal carbonization or solvothermal carbonization method, and the surface of the wood base is rich in specific functional groups by precisely regulating and controlling the surface chemistry of the wood base. The precisely regulated and controlled surface chemistry can enhance the binding force of a wood base and Li4Ti5O12 nanoparticles, optimize a diffusion channel of lithium titanate in a solid phase, and effectively regulate and control the formation and stability of a solid electrolyte interface film. According to the composite negative electrode material prepared by the invention, the rate capability, the cycling stability and the low-temperature performance of the Li4Ti5O12 battery are remarkably improved. The invention has the advantages of greenness, environmental protection, low cost and excellent performance.

Description

Technical Field

[0001] The present invention relates to Li4Ti5O 12 The technical field of battery negative electrode materials, specifically wood-based carbon quantum dots as Li4Ti5O 12 High-efficiency negative electrode materials for batteries. Background Art

[0002] Lithium titanate battery has become a key technology in the fields of portable electronic devices, electric vehicles and large-scale energy storage systems due to its high energy density, long cycle life and relative environmental protection. 12 Lithium titanate (LTT) is regarded as a highly promising next-generation negative electrode material due to its unique "zero strain" characteristics, excellent safety, excellent cycle stability and wide operating temperature range. However, LTO also has significant limitations. Its intrinsic conductivity is extremely low (about 10-13S / cm), which hinders the transmission of lithium titanate and electrons inside it, thereby limiting the rate performance (i.e., large current charge and discharge capability) and low-temperature performance of LTO materials. In fast charging scenarios and cold environments, the performance of LTO batteries is often unsatisfactory.

[0003] At present, the mainstream strategies to improve the conductivity of lithium titanate include carbon coating, element doping and nano-sizing. Carbon coating is a widely used and effective means to improve electron conduction by forming a conductive carbon layer on the surface of lithium titanate particles. However, traditional carbon sources such as graphite and acetylene black are relatively expensive, and it is difficult to achieve uniform and ultra-thin coverage of the carbon coating layer, and sometimes impurities may be introduced. In addition, although nano-sized lithium titanate particles shorten the transmission path of lithium titanate, they are also prone to agglomeration, resulting in a decrease in specific surface area and an increase in battery internal resistance.

[0004] As an emerging nanocarbon material, wood-based carbon quantum dots have shown great potential in recent years in many fields such as catalysis, bioimaging, and drug delivery due to their unique quantum size effect, high specific surface area, good conductivity, easy surface functionalization, excellent biocompatibility, and green environmental protection. It is worth noting that there are currently few reports on the use of cheap and readily available wood as a carbon source to prepare carbon quantum dots and their efficient application in the modification of lithium titanate negative electrode materials. More importantly, the existing technology still has deficiencies in how to precisely control the surface chemistry of carbon quantum dots to synergistically improve the electrochemical performance of lithium titanate, especially in the optimization of lithium titanate transmission and solid electrolyte interface film formation. This limits further breakthroughs in lithium titanate materials in high-power and long-life applications. Therefore, developing a carbon quantum dot prepared from sustainable biomass and capable of precise surface chemistry to modify lithium titanate negative electrode materials to achieve high-performance lithium titanate batteries is a technical problem that needs to be solved. Summary of the Invention

[0005] Technical problems solved

[0006] In view of the shortcomings of the prior art, the present invention provides wood-based carbon quantum dots as Li4Ti5O 12 The battery's high-efficiency negative electrode material solves the problems of existing technologies.

[0007] (2) Technical solution

[0008] The present invention provides the following technical solution: wood-based carbon quantum dots as Li4Ti5O 12 High-efficiency negative electrode material for batteries, comprising Li4Ti5O 12 Nanoparticles and wood-based carbon quantum dots, the wood-based carbon quantum dots are uniformly loaded and adsorbed on Li4Ti5O 12 The surface of the nanoparticles is filled in the gaps between the nanoparticles to form an efficient electron and lithium titanate transmission network.

[0009] Preferably, the wood-based carbon quantum dots are prepared using wood as raw material through hydrothermal carbonization and solvent thermal carbonization methods.

[0010] Preferably, the wood is selected from discarded pine, poplar and bamboo.

[0011] Preferably, the average particle size of the wood-based carbon quantum dots is 1 nanometer to 10 nanometers.

[0012] Preferably, the surface chemistry of the wood-based carbon quantum dots is precisely controlled, and the surface is rich in specific functional groups, including but not limited to hydroxyl groups, carboxyl groups, carbonyl groups, ether groups or other surface active sites. The precisely controlled surface chemistry helps to: enhance the wood-based and Li4Ti5O 12 Binding force of nanoparticles; Optimizing the diffusion channel of lithium titanate in the solid phase; Regulating the Li4Ti5O 12 Formation and stability of solid electrolyte interface films at the electrolyte interface.

[0013] Preferably, the Li4Ti5O 12 The average particle size of the nanoparticles is 50 to 200 nanometers.

[0014] Preferably, the content of the wood-based carbon quantum dots in the material is relative to that of Li4Ti5O 12 The weight percentage is 0.5% to 5%.

[0015] Preferably, the efficient transport network is a three-dimensional electron and lithium titanate transport network.

[0016] Preferably, the method comprises the following steps:

[0017] Sp9.1: Preparation of wood base: wood powder is mixed with a solvent, and a surfactant and a passivating agent are optionally added, and hydrothermal carbonization or solvent thermal carbonization is performed at a temperature range of 180°C to 250°C for 4 hours to 12 hours, and a dispersion is obtained through a purification process; and in the subsequent treatment in the step, the surface chemistry of the wood base is precisely controlled to prepare Li4Ti5O 12 Nanoparticles;

[0018] Sp9.2: The wood-based dispersion is mixed with the Li4Ti5O 12 The nanoparticles were mixed in specific ratios and subjected to ultrasonication and ball milling to achieve uniform composite;

[0019] Sp9.3: drying the mixture;

[0020] Sp9.4: The dried mixture is subjected to a low-temperature carbonization and sintering treatment at 300° C. to 600° C. in an inert atmosphere or a reducing atmosphere for 2 to 5 hours.

[0021] Preferably, precise control of wood-based surface chemistry in Sp9.1 is achieved by at least one of the following means:

[0022] Sp10.1: Adjusting the temperature, time and pressure during hydrothermal and solvothermal carbonization;

[0023] Sp10.2: Introducing specific elements and compounds during the synthesis process to modify wood-based surface properties;

[0024] Sp10.3: Adding specific surface functionalization reagents and passivation agents;

[0025] Sp10.4: Perform post-processing.

[0026] Preferably, the material is used as an active substance.

[0027] (3) Beneficial effects

[0028] The present invention has the following beneficial effects:

[0029] 1. Using wood-based carbon quantum dots as lithium carbonate batteries Li4Ti5O 12 Modifiers for negative electrode materials have achieved significant performance improvements. First, the use of waste wood as a carbon source not only greatly reduces material costs, but also conforms to the concept of green environmental protection and sustainable development, providing an economical and environmentally friendly new way to produce negative electrode materials. These nano-sized wood-based carbon quantum dots can act like tiny conductive bridges and be evenly dispersed in the Li4Ti5O 12 Between particles and on the surface, an efficient three-dimensional electron transport network is constructed, thereby effectively overcoming the Li4Ti5O 12The shortcoming of poor conductivity has been significantly improved by improving the battery's rate performance and low-temperature performance under high-current charging and discharging.

[0030] 2. Adopting precise control of the surface chemistry of carbon quantum dots. By carefully controlling the preparation process or subsequent modification, we can introduce and optimize specific functional groups on the surface of wood-based carbon quantum dots. These functional groups can not only significantly enhance the bonding between carbon quantum dots and Li4Ti5O 12 The bonding force between particles ensures the structural stability of the composite material and the durability of the conductive network. More importantly, they can cleverly optimize the diffusion path of lithium titanate in the solid phase and even regulate the formation and stability of the solid electrolyte interface film. This precisely controlled surface chemical synergistic effect can effectively inhibit the side reactions of the battery during the cycle, ultimately significantly improving the performance of Li4Ti5O 12 Improve the cycle stability of the battery and extend the overall service life of the battery.

[0031] Figure 1 The wood-based carbon quantum dots of the present invention are used as Li4Ti5O 12 Flowchart of efficient negative electrode materials for batteries. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1

[0034] See also Figure 1 , wood-based carbon quantum dots as Li4Ti5O 12 The high-efficiency negative electrode material of the battery is characterized in that the material contains Li4Ti5O 12 Nanoparticles and wood-based carbon quantum dots, wood-based carbon quantum dots are uniformly loaded and adsorbed on Li4Ti5O 12 The surface of the nanoparticles and fills the gaps between the nanoparticles to form an efficient electron and lithium titanate transmission network.

[0035] Wood-based carbon quantum dots are prepared using wood as raw material through hydrothermal carbonization and solvothermal carbonization methods.

[0036] The wood is selected from discarded pine, poplar and bamboo.

[0037] The average particle size of the wood-based carbon quantum dots is 1 nanometer to 10 nanometers.

[0038] The surface chemistry of wood-based carbon quantum dots is precisely controlled, and its surface is rich in specific functional groups, including but not limited to hydroxyl, carboxyl, carbonyl, ether and other surface active sites. The precisely controlled surface chemistry helps to: enhance the wood-based and Li4Ti5O 12 Binding force of nanoparticles; Optimizing the diffusion channel of lithium titanate in the solid phase; Regulating the Li4Ti5O 12 Formation and stability of solid electrolyte interface films at the electrolyte interface.

[0039] Li4Ti5O 12 The average particle size of the nanoparticles is 50 to 200 nanometers.

[0040] The content of wood-based carbon quantum dots in the material is relative to that of Li4Ti5O 12 The weight percentage is 0.5% to 5%.

[0041] The efficient transmission network is a three-dimensional electron and lithium titanate transmission network.

[0042] The following steps are involved:

[0043] Sp9.1: Preparation of wood base: Mix wood powder with solvent, optionally add surfactant and passivating agent, perform hydrothermal carbonization or solvent thermal carbonization at a temperature range of 180℃ to 250℃ for 4 hours to 12 hours, and obtain a dispersion through a purification process; and in the subsequent treatment in this step, precisely control the surface chemistry of the wood base to prepare Li4Ti5O 12 Nanoparticles;

[0044] Sp9.2: Wood-based dispersion with Li4Ti5O 12 The nanoparticles were mixed in specific ratios and subjected to ultrasonication and ball milling to achieve uniform composite;

[0045] Sp9.3: dry mixture;

[0046] Sp9.4: The dried mixture is subjected to a low-temperature carbonization and sintering treatment at 300° C. to 600° C. in an inert atmosphere or a reducing atmosphere for 2 to 5 hours.

[0047] Precise control of wood-based surface chemistry in Sp9.1 is achieved through at least one of the following means;

[0048] Sp10.1: Adjusting the temperature, time and pressure during hydrothermal and solvothermal carbonization;

[0049] Sp10.2: Introducing specific elements and compounds during the synthesis process to modify wood-based surface properties;

[0050] Sp10.3: Adding specific surface functionalization reagents and passivation agents;

[0051] Sp11.4: Perform post-processing.

[0052] material as active substance.

[0053] First, cheap and easily available waste wood (poplar sawdust) is selected as the carbon source instead of traditional expensive graphite and acetylene black. This not only greatly reduces the cost of raw materials, but also practices the concept of green environmental protection and sustainable development. The pre-carbonization treatment of wood is intended to remove some impurities and volatiles, providing a purer carbon skeleton for the subsequent formation of wood-based carbon quantum dots. Hydrothermal carbonization and solvent thermal carbonization are key steps in the preparation of wood-based carbon quantum dots. This method utilizes the decomposition and carbonization process of polymers such as cellulose, hemicellulose and lignin in wood under high temperature and high pressure water and organic solvent systems. In the hydrothermal system, water is not only a solvent, but also acts as a reactant and catalyst to promote the dehydration, polymerization and aromatization of wood biomass, and ultimately form a nano-sized carbon core. Precise control of the surface chemistry of wood-based carbon quantum dots is one of the technical highlights of the present invention. This is mainly achieved by introducing specific passivators (citric acid) and surfactants during the hydrothermal and solvent thermal processes. Citric acid can chelate metal ions, while its carboxyl and hydroxyl groups can participate in the carbonization process and anchor on the surface of wood-based carbon quantum dots, providing rich oxygen-containing functional groups. Surfactants such as surfactants can regulate the nucleation and growth of wood-based carbon quantum dots, affecting their final particle size distribution and surface charge, and thus affecting the arrangement and accessibility of surface functional groups. In addition, the precise control of parameters such as temperature and time of hydrothermal and solvent thermal treatments directly determines the degree of carbonization, degree of graphitization, size distribution, and the types and density of surface functional groups of wood-based carbon quantum dots. By controlling the carbonization conditions, the ratio of hydroxyl, carboxyl, carbonyl and ether groups on the surface of wood-based carbon quantum dots can be adjusted, and even a small amount of heteroatoms such as N and P can be introduced (if the wood contains additional additions). The types and quantities of these functional groups are crucial to the binding force between wood-based carbon quantum dots and lithium titanate and their behavior in the electrolyte. The purification process (centrifugation, filtration, dialysis) ensures the size uniformity of the obtained wood-based carbon quantum dots and removes small molecule impurities, thereby ensuring the performance stability and controllability of the subsequent composite materials. The average particle size of the finally prepared wood-based carbon quantum dots is usually controlled at 1-10 nanometers, with excellent water dispersibility and unique fluorescence properties.

[0054] Example 2

[0055] Li4Ti5O 12 Preparation and characteristics of nanoparticles:

[0056] Li4Ti5O 12The preparation of nanoparticles is the basis of composite materials. The present invention preferably adopts the sol-gel method, which can accurately control the composition and uniformity of the precursor, which is conducive to the subsequent calcination to obtain nano-scale lithium titanate particles (average particle size 50-200 nanometers) with uniform size and regular morphology. By controlling the ratio of titanium source (tetrabutyl titanate), lithium source (lithium acetate) and chelating agent (citric acid), as well as pH value and stirring conditions, a stable gel can be formed. Subsequent drying and high-temperature calcination (usually around 800°C) convert the gel into well-crystallized spinel structure Li4Ti5O 12 The purpose of nano-processing is to shorten the solid-phase diffusion path of lithium titanate and provide a larger electrode-electrolyte contact area, thereby improving the reaction kinetics.

[0057] Li4Ti5O 12 , refers to the material lithium titanate, its full name is spinel lithium titanate, which is a component of the battery.

[0058] Example 3

[0059] Wood-based carbon quantum dots modified Li4Ti5O 12 Formation mechanism and synergistic effect of composite anode materials:

[0060] The key innovation of this invention is to combine the prepared wood-based carbon quantum dots with Li4Ti5O 12 Nanoparticles are composited. The carbon quantum dot dispersion is thoroughly mixed with lithium titanate nanoparticles by methods such as ball milling or ultrasonic dispersion. Due to the nanometer size and surface functional groups of wood-based carbon quantum dots, they can interact with lithium titanate particles in a variety of ways:

[0061] Physical adsorption and loading: Wood-based carbon quantum dots can be uniformly adsorbed and loaded on the surface of lithium titanate nanoparticles and fill the gaps between the particles. This uniform dispersion strategy avoids the local agglomeration problem that may exist with traditional carbon materials (acetylene black) and ensures the continuity of the conductive network.

[0062] Chemical bonding interactions: The precisely controlled oxygen-containing functional groups on the surface of wood-based carbon quantum dots, such as carboxyl (-COOH) and hydroxyl (-OH), can form strong interactions with the titanium and oxygen sites on the surface of lithium titanate, forming hydrogen bonds or weak coordination bonds. These interactions strengthen the binding force between the carbon quantum dots and lithium titanate particles, improve the structural stability of the composite material, and effectively prevent the wood-based carbon quantum dots from falling off during battery cycling, thereby ensuring the durability of the conductive network.

[0063] Constructing a three-dimensional conductive network: Wood-based carbon quantum dots form an ultra-thin and dense conductive layer on the surface of lithium titanate particles, while filling the gaps between particles to build an efficient three-dimensional electron transport network. This network provides a fast channel for electrons to travel between and within lithium titanate particles, significantly compensating for the inherent poor conductivity of lithium titanate.

[0064] Optimizing lithium titanate transport channels: The nanometer size of wood-based carbon quantum dots and the presence of surface functional groups not only create electron channels but also have a positive impact on lithium titanate transport. Wood-based carbon quantum dots themselves may provide additional lithium titanate adsorption sites, while the polarity of their surface functional groups may also have a certain affinity for lithium titanate, promoting the diffusion of lithium titanate in the solid phase and optimizing the ion transport process at the interface between lithium titanate and the electrolyte.

[0065] Regulating the formation and stability of the solid electrolyte interface film: This is the core beneficial effect brought about by precise control of surface chemistry. The functional groups on the surface of wood-based carbon quantum dots and their specific surface energy can induce the electrolyte to decompose more evenly, thinner, and denser on the surface of lithium titanate, forming a more stable solid electrolyte interface film. An optimized solid electrolyte interface film can effectively inhibit the continuous decomposition of the electrolyte and reduce the irreversible consumption of lithium titanate, thereby significantly improving the cycle stability and coulombic efficiency of the battery. At the same time, a stable solid electrolyte interface film also helps to reduce the interfacial impedance of the battery and further improve the rate performance.

[0066] The role of the solid electrolyte interface film is crucial to the performance of lithium titanate:

[0067] Protective Effect: The solid electrolyte interface membrane forms a "wall" on the surface of the lithium titanate anode, effectively isolating it from the electrolyte. It prevents further reduction and decomposition of the electrolyte on the surface of the lithium titanate anode, thereby reducing electrolyte consumption. It also inhibits the co-embedding of solvent molecules into the anode material, preventing damage to the electrode structure. The stable solid electrolyte interface membrane further strengthens the inherent advantages of lithium titanate batteries, which already have high safety and long life.

[0068] Ion selectivity: The solid electrolyte interface membrane has unique ion selectivity. It allows lithium ions to pass freely, realizing the transfer of lithium ions between the lithium titanate negative electrode and the electrolyte, but at the same time blocks the passage of electrons. This characteristic ensures the electrochemical activity of the lithium titanate negative electrode material while preventing electrons from directly reacting with the electrolyte, thereby reducing the self-discharge rate of the battery and helping the lithium titanate battery maintain its excellent cycle stability.

[0069] Impact on battery performance: The thickness, uniformity, and stability of the solid electrolyte interface film (SEI) directly affect the cycle life, rate performance, and safety of lithium titanate batteries. If the SEI film is too thick or uneven, it will increase the interfacial impedance of the lithium titanate negative electrode and reduce the lithium ion transfer rate, resulting in a decrease in the rate performance of the lithium titanate battery and increased energy loss, especially in applications requiring fast charging. If the SEI film is unstable, it will repeatedly break and reform during the cycling of the lithium titanate battery, continuously consuming electrolyte and active lithium ions, causing rapid battery capacity decay and compromising its long cycle life advantage. Although lithium titanate itself has a high degree of safety, an unstable SEI film can still cause local hot spots, which in extreme cases indirectly affect the overall safety of the battery. Optimizing the SEI film of the lithium titanate negative electrode by precisely controlling the surface chemistry of wood-based carbon quantum dots is crucial for improving the overall performance of lithium titanate batteries.

[0070] Example 4

[0071] Heat treatment of composite materials:

[0072] The composite material can be carbonized and sintered at low temperatures (300-600°C in an inert atmosphere). This step aims to further optimize the interface between the wood-based carbon quantum dots and lithium titanate, potentially promoting a stronger bond or a tighter carbon layer formed on the surface of the lithium titanate. Lower temperatures can prevent irreversible changes in the lithium titanate crystal structure, while helping to remove residual solvents and impurities and further improving the conductivity of the wood-based carbon quantum dots.

[0073] Example 5

[0074] Battery performance verification:

[0075] By mixing the prepared composite material with a conductive agent and a binder to prepare a negative electrode slurry and coating it into an electrode sheet, it can be assembled into a button cell or soft pack battery for electrochemical performance testing. The test data will intuitively reflect the beneficial effects brought by the present invention. Compared with unmodified lithium titanate and traditional carbon-modified lithium titanate, the composite negative electrode material of the present invention has a significantly improved discharge capacity at high rates (5C, 10C); a higher capacity retention rate after long-term cycling; and can still maintain a high capacity and charge-discharge efficiency in a low temperature environment (-20°C). Electrochemical impedance spectroscopy tests will show a significant reduction in charge transfer resistance and lithium titanate diffusion resistance. Cyclic voltammetry tests will show a larger redox peak current and a smaller peak potential difference, proving that the electrode reaction kinetics are accelerated.

[0076]

[0077] Wood-based carbon quantum dots as Li4Ti5O 12High-efficiency negative electrode material for batteries; the working steps are the preparation and battery assembly process of the wood-based carbon quantum dot-modified lithium titanate negative electrode material of the present invention, first, by pretreating the waste wood, then using hydrothermal and solvent thermal carbonization methods, and precisely controlling the reaction conditions and the types and amounts of additives (citric acid, surfactant) in the process to prepare nano-scale wood-based carbon quantum dots with rich specific functional groups on the surface, which are then purified to obtain a uniform dispersion; at the same time, a lithium titanate precursor is prepared by a sol-gel method, and nano-scale lithium titanate particles are obtained by high-temperature calcination; thereafter, the prepared wood-based carbon quantum dot dispersion is efficiently mixed and dispersed with lithium titanate nanoparticles, and optionally subjected to low-temperature heat treatment to form a composite negative electrode material with an efficient three-dimensional electron and lithium ion transport network; finally, the composite material is mixed with a conductive agent and a binder to prepare a negative electrode slurry, which is coated, dried, rolled, and cut into electrode sheets, and assembled into a lithium titanate battery together with a positive electrode, a separator, and an electrolyte, and its significant improvement in rate performance, cycle stability, and low-temperature performance is verified by a series of electrochemical tests.

[0078] Specific application case one: In the fast charging and long cycle life energy storage system of electric buses, it can significantly improve vehicle operating efficiency and reduce the cost of the entire life cycle. Traditional bus batteries have a fast capacity decay and a long charging time under frequent high-power charging and discharging, while the material of the present invention can achieve ultra-fast charging of 80% within 10-15 minutes, greatly shortening the energy replenishment time and improving the vehicle turnover rate. At the same time, thanks to the precisely controlled surface chemistry of carbon quantum dots that optimizes the solid electrolyte interface membrane, even in the high-frequency fast charging and discharging cycles every day, the cycle life of the battery pack can be increased from thousands of times to tens of thousands of times, significantly reducing replacement costs. In addition, its excellent wide temperature adaptability ensures stable operation in cold northern regions, avoiding a sudden drop in cruising range and low charging efficiency due to low temperatures, thereby accelerating the electrification process of urban public transportation and improving benefits.

[0079] Specific application case two: In large-scale energy storage systems on the grid side, the materials of the present invention can be used for peak shaving and valley filling, peak and frequency regulation, and emergency standby, meeting the stringent requirements of these applications for long cycle life, high safety, fast response, and low self-discharge rate. The energy storage battery module constructed with the materials of the present invention can easily achieve a cycle life of more than 15,000 times, significantly reducing the maintenance cost and battery replacement frequency of the power station, and extending the project investment payback period. The inherent "zero strain" characteristics of lithium titanate combined with the stable and optimized solid electrolyte interface membrane of the present invention further enhance the inherent safety of the battery and reduce the risk of accidents in the energy storage system. At the same time, the improved rate performance enables it to quickly respond to grid commands, achieve high-power charging and discharging, improve frequency regulation efficiency, effectively promote the stable operation of the grid and the absorption of renewable energy, and provide a safer, more efficient and economical solution for energy transformation.

[0080] Specific application case three: The present invention is also extremely valuable in the fields of industrial unmanned transport vehicles and forklift power batteries. Unmanned transport vehicles and electric forklifts in smart factories and warehouse logistics usually need to operate around the clock, and have extremely high requirements for battery charging speed and cycle life. The negative electrode material of the present invention allows these devices to quickly replenish power during a short interval, achieving continuous operation, greatly improving logistics efficiency and production line utilization. The significant extension of battery life (up to 5-8 years) also means that there is no need to frequently replace battery packs, reducing corporate operating costs. In addition, in complex industrial environments, the high safety of lithium titanate combined with the stability of the negative electrode material of the present invention reduces the risk of thermal runaway of the battery under extreme operating conditions, and improves the operational reliability and wide-temperature operation capability of industrial equipment.

[0081] In summary

[0082] 1. Using wood-based carbon quantum dots as lithium carbonate batteries Li4Ti5O 12 Modifiers for negative electrode materials have achieved significant performance improvements. First, the use of waste wood as a carbon source not only greatly reduces material costs, but also conforms to the concept of green environmental protection and sustainable development, providing an economical and environmentally friendly new way to produce negative electrode materials. These nano-sized wood-based carbon quantum dots can act like tiny conductive bridges and be evenly dispersed in the Li4Ti5O 12 Between particles and on the surface, an efficient three-dimensional electron transport network is constructed, thereby effectively overcoming the Li4Ti5O 12 The shortcoming of poor conductivity has been significantly improved by improving the battery's rate performance and low-temperature performance under high-current charging and discharging.

[0083] 2. Adopting precise control of the surface chemistry of carbon quantum dots. By carefully controlling the preparation process and subsequent modification, we can introduce and optimize specific functional groups on the surface of wood-based carbon quantum dots. These functional groups can not only significantly enhance the bonding between carbon quantum dots and Li4Ti5O 12 The bonding force between particles ensures the structural stability of the composite material and the durability of the conductive network. More importantly, they can cleverly optimize the diffusion path of lithium titanate in the solid phase and even regulate the formation and stability of the solid electrolyte interface film. This precisely controlled surface chemical synergistic effect can effectively inhibit the side reactions of the battery during the cycle, ultimately significantly improving the performance of Li4Ti5O 12 Improve the cycle stability of the battery and extend the overall service life of the battery.

[0084] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Wood-based carbon quantum dots as Li4Ti5O 12 A high-efficiency negative electrode material for a battery, characterized in that The material contains Li4Ti5O 12 Nanoparticles and wood-based carbon quantum dots, wherein the wood-based carbon quantum dots are uniformly loaded and adsorbed on Li4Ti5O 12 The surface of the nanoparticles is filled in the gaps between the nanoparticles to form an efficient electron and lithium titanate transmission network.

2. The wood-based carbon quantum dots according to claim 1 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The wood-based carbon quantum dots are prepared using wood as raw material through hydrothermal carbonization and solvent thermal carbonization methods.

3. The wood-based carbon quantum dots according to claim 2 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The wood is selected from discarded pine, poplar and bamboo.

4. The wood-based carbon quantum dots according to claim 1 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The average particle size of the wood-based carbon quantum dots is 1 nanometer to 10 nanometers.

5. The wood-based carbon quantum dots according to claim 1 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The surface chemistry of the wood-based carbon quantum dots is precisely controlled, and the surface is rich in specific functional groups, including but not limited to hydroxyl groups, carboxyl groups, carbonyl groups, ether groups and other surface active sites. The precisely controlled surface chemistry helps to: enhance the wood-based and Li4Ti5O 12 The binding force of nanoparticles; Optimizing the diffusion channel of lithium titanate in the solid phase; Regulating Li4Ti5O 12 Formation and stability of solid electrolyte interface films at the electrolyte interface.

6. The wood-based carbon quantum dots according to claim 1 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The L i4 Ti5O 12 The average particle size of the nanoparticles is 50 to 200 nanometers.

7. The wood-based carbon quantum dots according to claim 1 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The content of the wood-based carbon quantum dots in the material is relative to that of Li4Ti5O 12 The weight percentage is 0.5% to 5%.

8. The wood-based carbon quantum dots according to claim 1 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The high-efficiency transmission network is a three-dimensional electron and lithium titanate transmission network.

9. The wood-based carbon quantum dots according to claims 1-8 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The following steps are involved: Sp9.1: Preparation of wood base: wood powder is mixed with a solvent, and a surfactant and a passivating agent are optionally added, and hydrothermal carbonization or solvent thermal carbonization is performed at a temperature range of 180°C to 250°C for 4 hours to 12 hours, and a dispersion is obtained through a purification process; and in the subsequent treatment in the step, the surface chemistry of the wood base is precisely controlled to prepare Li4Ti5O 12 Nanoparticles; Sp9.2: The wood-based dispersion is mixed with the Li4Ti5O 12 The nanoparticles were mixed in specific ratios and subjected to ultrasonication and ball milling to achieve uniform composite; Sp9.3: drying the mixture; Sp9.4: The dried mixture is subjected to a low-temperature carbonization and sintering treatment at 300° C. to 600° C. in an inert atmosphere or a reducing atmosphere for 2 to 5 hours.

10. The wood-based carbon quantum dots according to claim 9 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: Precise control of wood-based surface chemistry in Sp9.1 is achieved through at least one of the following means; Sp10.1: Adjusting the temperature, time and pressure during hydrothermal and solvothermal carbonization; Sp10.2: Introducing specific elements and compounds during the synthesis process to modify wood-based surface properties; Sp10.3: Adding specific surface functionalization reagents and passivation agents; Sp11.4: Perform post-processing.

11. The wood-based carbon quantum dots according to claims 1-8 as Li4Ti5O 12 High-efficiency negative electrode material for batteries, characterized by: The material is used as the active substance.

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