Method for synchronously realizing SiOx pre-lithiation, residual alkali removal and surface coating by one-step method and product thereof

Abstract

The invention provides a method for synchronously realizing SiOx pre-lithiation, residual alkali removal and surface coating by a one-step method and a product thereof, and belongs to the technical field of lithium ion battery materials. The preparation method comprises the following steps: mixing and grinding a SiOx material, binary eutectic lithium salt and nano Al2O3 powder to obtain a solid-phase mixture, pressing the solid-phase mixture into a block, and carrying out heat treatment in an inert atmosphere to obtain the pre-lithiated SiOx negative electrode material of which the outer layer is wrapped by LiAlO2. According to the method, the residual alkali is removed and effectively utilized, active lithium of pre-lithiated SiOx is preserved to a great extent, and preconditions are provided for subsequent lithium ion batteries with high initial coulombic efficiency, long cycle life and safety. The method is expected to be applied to residual alkali removal of a binary eutectic lithium salt pre-lithiation SiOx system and improvement of chemical stability of the binary eutectic lithium salt pre-lithiation SiOx system.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and particularly relates to a one-step method for simultaneously realizing SiO2. x Methods and products for pre-lithiation, residual alkali removal and surface coating. Background Technology

[0002] SiO x Anodes, due to their ultra-high theoretical specific capacity (over 2000 mAh / g), abundant reserves, and environmental friendliness, hold promise as an ideal choice for next-generation emerging anode materials. However, their extremely low initial coulombic efficiency (ICE, typically around 60%) has consistently limited their further application. Pre-lithiation is an effective way to improve the efficiency of SiO₂. x The most effective strategy for ICE (Insulation, Electrode, and Chip) on the negative electrode side, which we are familiar with, includes pre-lithiation on the negative electrode side, such as pre-lithiation with stabilized lithium metal powder (SLMP), additive pre-lithiation, short-circuit pre-lithiation, and electrochemical pre-lithiation. However, these pre-lithiation methods face stringent environmental requirements and complex process flows, making large-scale application difficult. Most lithium-containing alkali metal salts exhibit relatively stable chemical properties, and are not easily oxidized or deliquescent even after short-term exposure to air. Combining lithium salts with SiO₂... x Thorough physical mixing followed by heat treatment for lithium replenishment is feasible, and to some extent avoids the challenges posed by mainstream pre-lithiation technologies, such as stringent environmental requirements and complex operating processes. Therefore, lithium salt pre-lithiation technology, due to its simple process and scalability, significantly improves the lithium content of SiO₂. x The anode material, ICE (Insulation and Chemical Reactor), holds promise for commercialization. However, the use of a single lithium salt inevitably leads to high energy consumption and SiO₂ content due to high-temperature reactions. x The material undergoes a disproportionation reaction, further leading to the problem of continuous coarsening of silicon particles. A binary lithium salt with a low eutectic point is selected for SiO₂. x Pre-lithiation of materials is crucial for reducing energy consumption and mitigating the growth-driving force of silicon particles. However, even with lithium salt pre-lithiation systems, residual alkali metal salts such as LiOH, Li₂CO₃, and organolithium salts are unavoidable. These residual lithium metal salts readily undergo hydrolysis with water to generate a third phase of alkali metal salts and gases, leading to an increase in the system's pH value. This presents extremely poor compatibility with aqueous pulping processes. On one hand, excessively high pH values ​​in the pulp severely affect its viscosity and flowability, causing material stratification and agglomeration, ultimately resulting in the failure of the entire pulping process. On the other hand, residual lithium metal salts react with active lithium in the electrolyte to form an excessively thick, uneven, and irreversible solid electrolyte interphase (SEI) layer, which can trigger SiO₂ formation. x The delithiation reaction in materials significantly reduces the amount of active lithium, ultimately leading to increased interfacial impedance and decreased ICE (interfacial resistance and electrochemical conductivity). This process also generates flammable gases, causing the battery to swell due to increased internal pressure, posing a safety hazard. Therefore, the removal of residual alkali is a crucial and essential process.

[0003] Currently, water, ethanol, and acid washing are commonly used to remove residual alkali during lithium salt pre-lithiation. However, water washing, ethanol cleaning, and acid washing inevitably consume some of the effective lithium due to the strong polarity of water and ethanol, weakening the pre-lithiation effect. Furthermore, these processes are complex and prone to introducing impurities. In addition, the pre-lithiated SiO₂... x The lithium silicate-rich SEI layer formed on the outer layer of the material is not completely inert and readily reacts slowly but significantly with water, CO2, and O2 exposed to air. This causes the effective active lithium silicate component in the material to become an ineffective and unfavorable lithium source. Therefore, strict sealing and protection measures are usually required to ensure the best pre-lithiation effect of the material. Thus, pre-lithiation of SiO2... x The material is also similar to SiO in its initial state. x The materials are far from being able to be exposed to air, and appropriate processes are still needed to remove residual alkali and strict inert protection measures.

[0004] In addition to water washing, ethanol cleaning, and acid washing to remove residual alkali, an inert material is used to coat the lithium salt pre-lithiated SiO₂. x Surface deposition is also a viable strategy; some studies have used vapor deposition on pre-lithiated SiO₂. x A layer of Al2O3 is coated on the surface, and the inert Al2O3 coating isolates the residual alkali from the aqueous solvent and electrolyte, greatly reducing side reactions. However, the biggest drawback is that this method completely retains the residual alkali without removing it. In subsequent electrochemical applications, it is still inevitable that the residual alkali will break and come into contact with the electrolyte, causing harmful reactions and ultimately threatening the safe use of the battery. In addition, this process is limited to the experimental stage and is costly, making it difficult to apply on a large scale. Introducing a feasible additive to consume the residual alkali while generating a third phase material to coat the pre-lithiation product and effectively reduce its air sensitivity, thus achieving good chemical stability, is a novel process worth exploring. Under certain driving forces, Al2O3 can react with some lithium-containing alkali metal salts to form lithium aluminate (LiAlO2). LiAlO2 has a very stable crystal structure due to the presence of Al-O chemical bonds. Lithium ions are firmly locked in the stable [AlO4] lattice, making it difficult to react with moisture and CO2 in the air, thus maintaining excellent chemical stability in air for a long time. Using Al2O3 and SiO2 pre-lithiated with a single lithium salt x The secondary heat treatment of materials and the generation of chemically stable LiAlO2 by controlling the amount of Al2O3 added have been proven to be feasible in related work. However, this pre-lithiation method inevitably involves high-temperature reactions, and the step-by-step process of pre-lithiation followed by modification requires additional process steps, which fails to fully achieve the synchronous synergy of residual alkali removal and coating layer formation.

[0005] Furthermore, although lithium salt pre-lithiation technology has advantages such as simple process and scalability, the use of single lithium salts (such as LiH, LiOH, etc.) still has significant shortcomings: on the one hand, single lithium salts have high melting points, requiring high temperatures (usually >700℃) to achieve effective pre-lithiation, resulting in high energy consumption, and high temperatures can easily trigger SiO2 formation. x The material undergoes a disproportionation reaction, leading to coarsening of silicon particles and affecting its cycle stability. On the other hand, even with lithium salt pre-lithiation, alkaline substances such as LiOH and Li₂CO₃ remain in the system. While these can be removed by washing with water or acid, such processes are complex, prone to introducing impurities, and inevitably result in the loss of some active lithium, weakening the pre-lithiation effect. Furthermore, existing technologies often employ a step-by-step process of "pre-lithiation followed by coating" to achieve material stabilization. For example, pre-lithiation is performed using lithium salts such as LiH, followed by the introduction of a coating layer such as Al₂O₃ through vapor deposition or secondary heat treatment. While this method can improve the environmental stability of the material to some extent, it is complex, costly, and fails to achieve in-situ conversion and utilization of residual alkali. The residual alkali remains inside the material or at the interface, and during long-term cycling, it may come into contact with the electrolyte due to coating layer rupture, continuously triggering side reactions and affecting battery safety and cycle life.

[0006] Therefore, how to achieve efficient pre-lithiation while fundamentally removing residual alkali and constructing a stable surface coating, and simplifying the process and reducing costs as much as possible, remains a pressing technical challenge in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a one-step method for simultaneous realization of SiO2. x The present invention relates to a method and product for pre-lithiation, residual alkali removal and surface coating, which utilizes binary eutectic lithium salts and micron-sized SiO2. x Simultaneous simple physical mixing and heat treatment of materials and nano-sized Al2O3 materials yields a SiO material with high initial coulombic efficiency and excellent chemical stability. x Anode material, this invention achieves SiO x While pre-lithiating the material with lithium salt, residual alkali is efficiently removed and the chemical stability of the material is improved, solving the problems of poor compatibility with aqueous pulping, low initial efficiency and short cycle life.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides a one-step method for simultaneous realization of SiO x The method for pre-lithiation, residual alkali removal, and surface coating includes the following steps:

[0010] SiO xThe material, binary eutectic lithium salt and nano-Al2O3 powder are mixed and ground to obtain a solid-phase mixture. The solid-phase mixture is pressed into a block and heat-treated under an inert atmosphere to obtain pre-lithiated SiO wrapped by LiAlO2 on the outer layer. x Anode material.

[0011] Further, the SiO x material is amorphous SiO x or carbon-coated SiO x , where 0 < x < 2 and the particle size is 2 - 10 μm.

[0012] Further, the binary eutectic lithium salt is selected from one of LiOH-Li2CO3, LiOH-LiNO3, LiOH-LiCl, and LiNO3-LiCl; preferably, the binary eutectic lithium salt is LiOH-Li2CO3 or LiOH-LiNO3.

[0013] Further, the particle size of the nano-Al2O3 powder is 15 nm.

[0014] Further, the mass ratio of the SiO x material to the binary eutectic lithium salt is (8 - 9.5):(0.5 - 2). Exemplarily, the mass ratio of the SiO x material to the binary eutectic lithium salt is 8:2, 8.5:1.5, 9:1, 9.5:0.5. Preferably, the mass ratio of the SiO x material to the binary eutectic lithium salt is 9:1, 9.5:0.5.

[0015] Further, the addition amount of the nano-Al2O3 powder is 1 - 10 wt% of the total mass of the SiO x [[ID=3!]]and the binary eutectic lithium salt, preferably 5 - 10 wt%.

[0016] Further, the temperature of the heat treatment is 600 - 700 °C, the holding time is 4 - 6 hours, and the heating rate is 2 - 10 °C / min; preferably, the heating rate is 2 °C / min.

[0017] Further, the pressure of the pressing is 15 - 20 MPa, and the pressure holding time is 3 - 4 minutes; preferably, the pressure is 16 MPa and the pressure holding time is 3 minutes.

[0018] Further, the inert atmosphere is Ar, He or N2; preferably, the inert atmosphere is Ar.

[0019] Further, the grinding time is 20 - 30 minutes; preferably, the grinding time is 20 minutes.

[0020] The present invention also provides a pre-lithiated SiOx The negative electrode material was prepared according to the above method.

[0021] The present invention also provides a lithium-ion battery comprising the above-mentioned pre-lithiated SiOx anode material.

[0022] Technical principle of the invention:

[0023] (1) Pre-lithiation process: The binary eutectic lithium salt is in a molten state at the heat treatment temperature and rapidly penetrates into SiO. x Inside the particles, with SiO x The reaction produces lithium silicate (Li). x SiO y Pre-lithiation of SiOx is achieved by using pre-lithiation products such as nano-Si and nano-Si.

[0024] (2) Residual alkali removal process: During the heat treatment process, Al2O3 can react with pre-lithiated SiO2. x The residual alkali (mainly LiOH and Li2CO3) on the material surface undergoes a chemical reaction to generate LiAlO2. The H2O and CO2 produced are discharged with the inert gas. The reaction process is as follows:

[0025] Reaction with LiOH: ;

[0026] Reaction with Li2CO3: ;

[0027] (3) Coating formation process: The residual alkali metal salts LiOH and Li2CO3 are converted into chemically stable LiAlO2. This process not only fundamentally eliminates the negative impact of residual alkali, but also... x A uniform, dense, and ion-conducting LiAlO2 protective layer was constructed in situ on the particle surface.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects:

[0029] (1) High efficiency and synchronization: The pre-lithiation, residual alkali removal and coating layer construction are completed in one step, without the need for step-by-step operation. The process is simple, the equipment requirements are low, and it is compatible with existing production processes.

[0030] (2) High efficiency in removing residual alkali: Al2O3 reacts directly with residual alkali without loss of active lithium. Compared with water washing and acid washing processes, it retains the active lithium introduced by pre-lithiation to a greater extent, ensuring a significant improvement in ICE.

[0031] (3) Excellent chemical stability: The LiAlO2 coating layer is dense and chemically inert, which can avoid the SiO2 corrosion. x Side reactions between particles and air, water, and electrolyte have improved cycle life to some extent;

[0032] (4) Compatibility with aqueous pulping: The pH value of the material is reduced after the removal of residual alkali, which fundamentally solves the problem of poor compatibility with aqueous pulping processes. The viscosity and fluidity of the pulp are improved, and there is no bubbling, stratification and agglomeration.

[0033] (5) Outstanding cost advantage: The cost of using binary eutectic lithium salt is lower than that of hydride lithium salt (LiH, LiAlH4), the amount of nano Al2O3 added is controllable (5~10wt%), and the heat treatment temperature is lower than that of some existing processes (above 700℃), which can effectively reduce the cost of industrialization.

[0034] In summary, this invention uses Al2O3 to remove lithium salt pre-lithiation SiO2. x The process removes residual alkali and simultaneously generates a chemically stable, dense LiAlO2 coating. This effectively improves the compatibility of the pulping process, which is often affected by pH increases due to aqueous pulping methods. Furthermore, it avoids the failure behavior caused by direct contact between residual alkali and the electrolyte during subsequent electrochemical testing, preventing side reactions that could lead to decreased ICE and rapid capacity decay. This achieves the removal and effective utilization of residual alkali, maximizing the preservation of pre-lithiated SiO2. x The active lithium provides a prerequisite for subsequent lithium-ion batteries with high ICE (intercalation efficiency), long cycle life, and high safety. This invention holds promise for the pre-lithiation of SiO2 in binary eutectic lithium salts. x It has been applied to the removal of residual alkali and the improvement of chemical stability of the system. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 The SiO2 pre-lithiated lithium salt in this embodiment of the invention x Schematic diagram of the material preparation process;

[0037] Figure 2 The SiO obtained in Comparative Example 1, Example 1 and 2 x XRD pattern of the material;

[0038] Figure 3 The SiO obtained in Comparative Examples 3, 5, and 6 x XRD pattern of the material;

[0039] Figure 4 For comparative example 9, SiO x XRD pattern of the material;

[0040] Figure 5The SiO obtained in Comparative Example 10 and Example 6 x XRD pattern of the material;

[0041] Figure 6 The SiO obtained in Comparative Example 9, Comparative Example 3, Example 5, and Example 6 x SEM images of the material;

[0042] Figure 7 For comparative examples 3, 9 and 10, and SiO obtained in Example 6 x A diagram showing the effect of the material being circulated 100 times at 400mA / g. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] This invention provides a one-step method for simultaneous SiO2 production. xMethod for prelithiation, residual alkali removal and surface coating, comprising the following steps:

[0049] Mix and grind the SiOx material, binary eutectic lithium salt and nano-Al2O3 powder to obtain a solid-phase mixture, press the solid-phase mixture into a block, and perform heat treatment in an inert atmosphere to obtain prelithiated SiO with an outer layer wrapped by LiAlO2 x Anode material.

[0050] In the present invention, by mixing, pressing and heat-treating the SiO x material, binary eutectic lithium salt and nano-Al2O3 powder in an inert atmosphere, one-step synchronous completion of prelithiation, residual alkali removal and surface coating of SiO x is achieved. This method utilizes the melting and penetration of the binary eutectic lithium salt into the SiO x particles during heat treatment and reacts with them to generate prelithiation products; at the same time, Al2O3 reacts with residual alkali (such as LiOH, Li2CO3) to form a stable LiAlO2 coating layer, and by-products such as H2O and CO2 are discharged, thereby constructing a dense protective layer while removing residual alkali, improving the chemical stability and electrochemical performance of the material.

[0051] In a preferred embodiment of the present invention, the SiO x material is amorphous SiO x or carbon-coated SiO x , where 0 < x < 2 and the particle size is 2 - 10 μm. Within this range, it can ensure that the material has an appropriate specific surface area and reaction activity, which is conducive to the penetration of lithium salt and the progress of the prelithiation reaction, while avoiding agglomeration caused by too small particle size or incomplete reaction due to too large particle size.

[0052] In a preferred embodiment of the present invention, the binary eutectic lithium salt is selected from one of LiOH-Li2CO3, LiOH-LiNO3, LiOH-LiCl and LiNO3-LiCl. Utilize its eutectic point characteristic to reduce the heat treatment temperature, reduce energy consumption and inhibit the disproportionation reaction of SiOx, while ensuring that the lithium salt fully penetrates and reacts in the molten state. The binary eutectic lithium salt is prepared according to the molar eutectic point ratio; in a binary mixture system, when two components are mixed in a specific ratio, they will melt simultaneously at a specific temperature, which is lower than the melting point of any pure component. This lowest point is called the eutectic point, and the corresponding composition is called the eutectic composition. When these two substances are mixed in a certain specific molar ratio, the melting point of the mixture will reach the lowest value, this temperature is called the "lowest eutectic point", and the corresponding composition ratio is the "lowest eutectic point ratio".

[0053] Taking LiOH-Li₂CO₃ as an example, the mixing ratio of the two phases is prepared according to the chemical composition corresponding to the lowest eutectic point in the LiOH-Li₂CO₃ binary phase diagram. Pure LiOH has a melting point of approximately 471℃, and pure Li₂CO₃ has a melting point of approximately 723℃. The melting point of the eutectic mixture can be reduced to approximately 418-433℃. At this point, the specific molar ratio of LiOH to Li₂CO₃ in the LiOH-Li₂CO₃ system is 2.85:1 (i.e., 0.0533g of LiOH and 0.0578g of Li₂CO₃). Taking LiOH-LiNO₃ as another example, the specific molar ratio of LiOH to LiNO₃ in the LiOH-LiNO₃ system is 1:1.63 (i.e., 0.0176g of LiOH and 0.0824g of LiNO₃).

[0054] In a preferred embodiment of the present invention, Al2O3 is a nano-sized powder with a particle size of 15 nm; this particle size range can ensure that it has a high specific surface area and reactivity, which is beneficial to fully contact with residual alkali and quickly generate a uniform LiAlO2 coating layer.

[0055] In a preferred embodiment of the present invention, SiO x The mass ratio of the material to the binary eutectic lithium salt is (8-9.5):(0.5-2). For example, the mass ratio of SiOx to the binary eutectic lithium salt is 8:2, 8.5:1.5, 9:1, or 9.5:0.5. Preferably, the mass ratio of SiOx material to the binary eutectic lithium salt is 9:1 or 9.5:0.5. Within this range, sufficient lithium salt can be ensured for effective pre-lithiation, while avoiding excessive lithium salt leading to excessive residual alkali or increased reaction byproducts.

[0056] In a preferred embodiment of the present invention, the amount of nano-Al2O3 powder added is 1-10 wt% of the total mass of SiOx and binary eutectic lithium salt, preferably 5-10 wt%. This ensures that the residual alkali is fully consumed and forms a continuous and dense LiAlO2 coating layer, while avoiding excessive Al2O3 from affecting the electrochemical performance of the material.

[0057] In a preferred embodiment of the present invention, the heat treatment temperature is 600-700℃, the holding time is 4-6 hours, and the heating rate is 2-10℃ / min; preferably, the heating rate is 2℃ / min. Heat treatment allows the binary eutectic lithium salt to fully melt and the pre-lithiation reaction to be complete, while simultaneously promoting the reaction of Al2O3 with residual alkali to form LiAlO2, avoiding excessively high temperatures that could lead to SiO2 formation. x Structural damage or coarsening of silicon particles.

[0058] In a preferred embodiment of the present invention, the pressing pressure is 15 - 20 MPa, and the pressure holding time is 3 - 4 minutes; preferably, the pressure is 16 MPa and the pressure holding time is 3 minutes. This ensures the tight combination of the mixed materials, facilitating heat and mass transfer during the heat treatment process and promoting the uniform progress of the reaction.

[0059] In a preferred embodiment of the present invention, the inert atmosphere is Ar, He or N2; preferably, the inert atmosphere is Ar.

[0060] In a preferred embodiment of the present invention, the grinding time is 20 - 30 minutes; preferably, the grinding time is 20 minutes.

[0061] Exemplarily, in an embodiment of the present invention, a method for synchronously realizing SiO x pre - lithiation, residual alkali removal and surface coating specifically includes the following steps:

[0062] (1) Place SiO x material (amorphous SiO x or carbon - coated SiO x , where 0 < x < 2 and the particle size is 2 - 10 μm), a binary eutectic lithium salt (selected from one of LiOH - Li2CO3, LiOH - LiNO3, LiOH - LiCl and LiNO3 - LiCl), and nano - Al2O3 powder (particle size 15 nm) in a mortar and grind for 20 - 30 minutes until evenly mixed to obtain a mixed material; the mass ratio of SiOx to the binary eutectic lithium salt is (8 - 9.5):(0.5 - 2), and the addition amount of nano - Al2O3 powder is 1 - 10 wt% of the total mass of SiOx and the binary eutectic lithium salt;

[0063] (2) Press the mixed material obtained in step (1) on a press to 15 - 20 MPa to form a block, release the pressure after holding the pressure for 3 - 4 minutes to obtain the pressed - block material;

[0064] (3) Transfer the material obtained in step (2) to a quartz crucible, and under an inert atmosphere (Ar, He or N2), heat it at a heating rate of 2 - 10 °C / min to 600 - 700 °C, and perform heat treatment for 4 - 6 hours. Wait for it to cool naturally to room temperature to obtain the SiO x material pre - lithiated with lithium salt and wrapped by LiAlO2 on the outer layer.

[0065] The schematic diagram of the preparation process of the SiO x material pre - lithiated with lithium salt in the embodiment of the present invention is shown in Figure 1 , it can be seen that the initial SiO xThere are several critical states of the material raw materials. The outermost layer is amorphous SiO2, and the innermost layer is nanodomain Si. After mixing and heat treatment with a binary eutectic lithium salt and nano-Al2O3 powder, a lithium salt pre-lithiated SiO material with an outer layer wrapped by LiAlO2 is obtained. x The material also contains lithium metasilicate (Li2SiO3) that can act as a buffer matrix and lithium orthosilicate (Li4SiO4) that forms an inert component.

[0066] An embodiment of the present invention also provides a pre-lithiated SiO x negative electrode material, which is prepared according to the above method.

[0067] An embodiment of the present invention also provides a lithium-ion battery, which includes the above-mentioned pre-lithiated SiOx negative electrode material.

[0068] In the embodiment of the present invention, room temperature refers to "25 ± 3°C".

[0069] All raw materials used in the embodiments of the present invention are obtained by purchasing commercially. Among them, the SiO x material is sourced from Kelude and belongs to amorphous SiO x or carbon-coated SiO x , where 0 < x < 2, the particle size is 2 - 10 μm, and the particle size of the nano-Al2O3 powder used is 15 nm.

[0070] The technical solution of the present invention is further described below through embodiments.

[0071] Example 1

[0072] A method for synchronously realizing SiO x pre-lithiation, residual alkali removal and surface coating in one step, specifically including the following steps:

[0073] (1) Place 0.9 g of SiOx material, 0.1 g of binary eutectic lithium salt (LiOH-Li2CO3, prepared according to the molar ratio of LiOH and Li2CO3 of 2.85∶1) and nano-Al2O3 powder in a mortar and grind for 20 minutes until evenly mixed to obtain a mixed material; the mass ratio of the SiOx material to the binary eutectic lithium salt is 9:1, and the addition amount of the nano-Al2O3 powder is 5 wt% of the total mass of the SiOx and the binary eutectic lithium salt;

[0074] (2) Press the mixed material obtained in step (1) on a pressure device to 16 MPa to form a block, and release the pressure after maintaining the pressure for 3 minutes to obtain the pressed block material;

[0075] (3) Transfer the material obtained in step (2) to a quartz crucible, heat it to 600°C at a heating rate of 2°C / min under an inert atmosphere (Ar), and heat-treat for 4 hours. After natural cooling to room temperature, a lithium salt pre-lithiated SiO2 with an outer layer coated by LiAlO2 is obtained. x Material.

[0076] Example 2

[0077] Same as Example 1, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0078] Example 3

[0079] Same as Example 1, except that the heat treatment lasts for 6 hours.

[0080] Example 4

[0081] Same as Example 3, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0082] Example 5

[0083] Same as Example 1, except that the temperature is raised to 700°C and heat-treated for 4 hours.

[0084] Example 6

[0085] Same as Example 5, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0086] Example 7

[0087] Same as Example 5, except that the temperature is raised to 700°C and heat-treated for 6 hours.

[0088] Example 8

[0089] Same as Example 7, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0090] Example 9

[0091] A one-step method for simultaneous realization of SiO x The method for pre-lithiation, residual alkali removal, and surface coating specifically includes the following steps:

[0092] (1) 0.9g of SiOx material, 0.1g of binary eutectic lithium salt (LiOH-LiNO3, prepared according to a molar ratio of LiOH to LiNO3 of 1:1.63) and nano Al2O3 powder were placed in a mortar and ground for 20 minutes until they were mixed evenly to obtain a mixed material; wherein the mass ratio of SiOx material to binary eutectic lithium salt was 9:1, and the amount of nano Al2O3 powder added was 5wt% of the total mass of SiOx and binary eutectic lithium salt;

[0093] (2) Press the mixed material obtained in step (1) to 16 MPa on a pressure device to form a block, hold the pressure for 3 minutes and then release the pressure to obtain the material in the block;

[0094] (3) Transfer the material obtained in step (2) to a quartz crucible, heat it to 600°C at a heating rate of 2°C / min under an inert atmosphere (Ar), and heat-treat for 4 hours. After natural cooling to room temperature, a lithium salt pre-lithiated SiO2 with an outer layer coated by LiAlO2 is obtained. x Material.

[0095] Example 10

[0096] Same as Example 9, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0097] Example 11

[0098] Same as Example 9, except that the heat treatment lasts for 6 hours.

[0099] Example 12

[0100] Same as Example 11, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0101] Example 13

[0102] Same as Example 9, except that the temperature is raised to 700°C and heat-treated for 4 hours.

[0103] Example 14

[0104] Same as Example 13, except that the amount of nano Al2O3 powder added is 10 wt% of the total mass of SiOx and binary eutectic lithium salt.

[0105] Example 15

[0106] Same as Example 14, except that the temperature is raised to 700°C and heat-treated for 6 hours.

[0107] Example 16

[0108] Same as Example 15, except that the amount of nano-Al2O3 powder added is SiO2. x 10 wt% of the total mass of the binary eutectic lithium salt.

[0109] Examples 17-32

[0110] Based on Examples 1-16, the raw material SiO was respectively... x The amounts of material and binary eutectic lithium salt have been modified to 0.95g SiOx material and 0.05g binary eutectic lithium salt, i.e., SiO... x The mass ratio of the material to the binary eutectic lithium salt was 9.5:0.5, and the remaining preparation steps remained the same.

[0111] Comparative Example 1

[0112] Same as Example 1, except that the addition of nano-Al2O3 powder is omitted, and the specific steps include:

[0113] (1) Take 0.9g SiO x The material and 0.1g of binary eutectic lithium salt (LiOH-Li2CO3, prepared according to a molar ratio of LiOH to Li2CO3 of 2.85:1) were placed in a mortar and ground for 20 minutes until they were mixed evenly to obtain a mixed material; wherein the mass ratio of SiOx material to binary eutectic lithium salt was 9:1.

[0114] (2) Press the mixed material obtained in step (1) to 16 MPa on a pressure device to form a block, hold the pressure for 3 minutes and then release the pressure to obtain the material in the block;

[0115] (3) Transfer the material obtained in step (2) to a quartz crucible, heat it to 600°C at a heating rate of 2°C / min under an inert atmosphere (Ar), and heat-treat for 4 hours. After natural cooling to room temperature, obtain lithium salt pre-lithiated SiO. x Material.

[0116] Comparative Example 2

[0117] Same as Comparative Example 1, the only difference is that the heat treatment lasted 6 hours.

[0118] Comparative Example 3

[0119] Similar to Comparative Example 1, the only difference is that the heat treatment was carried out at 700℃.

[0120] Comparative Example 4

[0121] Similar to Comparative Example 2, the only difference is that the heat treatment was carried out at 700°C.

[0122] Comparative Example 5

[0123] Same as Example 9, except that the addition of nano-Al2O3 powder is omitted.

[0124] Comparative Example 6

[0125] The same as Comparative Example 5, the only difference being that the heat treatment lasted 6 hours.

[0126] Comparative Example 7

[0127] Similar to Comparative Example 5, the only difference is that the heat treatment was carried out at 700℃.

[0128] Comparative Example 8

[0129] The same as Comparative Example 7, the only difference being that the heat treatment lasted 6 hours.

[0130] Comparative Example 9

[0131] Unlithiated SiO x Material (i.e., SiO used in Example 1) x Material).

[0132] Comparative Example 10

[0133] The lithium salt pre-lithiated SiO2 with an outer layer coated by LiAlO2 obtained in Example 6 x The material was exposed to air for 2 weeks.

[0134] Comparative Examples 11-18

[0135] Based on comparative examples 1-8, the raw material SiO was respectively... x The amounts of material and binary eutectic lithium salt have been modified to 0.95g SiOx material and 0.05g binary eutectic lithium salt, i.e., SiO... x The mass ratio of the material to the binary eutectic lithium salt was 9.5:0.5, and the remaining preparation steps remained the same.

[0136] Performance testing

[0137] The SiO₂ obtained in Examples 1, 2, 5, 6 and Comparative Examples 1, 3, 9, 10 x The material was subjected to X-ray diffraction (XRD) testing, with the diffraction angle ranging from 10 to 80° and the X-ray scanning speed being 5° / min.

[0138] SiO obtained in Comparative Examples 1, 1, and 2 x The XRD pattern of the material is shown below. Figure 2 .

[0139] SiO obtained in Comparative Examples 3, 5 and 6 x The XRD pattern of the material is shown below. Figure 3 .

[0140] Comparative Example 9 SiOx The XRD pattern of the material is shown below. Figure 4 .

[0141] Comparative Example 10 and SiO obtained in Example 6 x The XRD pattern of the material is shown below. Figure 5 .

[0142] SiO obtained from Comparative Example 9, Comparative Example 3, Example 5, and Example 6 x Scanning electron microscope (SEM) images of the material are shown below. Figure 6 .

[0143] The SiO obtained from each group of examples and comparative examples x The materials underwent constant current charge-discharge testing, and the results are shown in Table 1. Button cell test conditions: constant temperature 25℃, CR2016, constant current charge-discharge current density of 400 mA / g, test voltage range 0.01V-2.0V vs Li / Li + Among them, the SiO obtained in Comparative Examples 3, 9 and 10, and Example 6 x The cycling effect of the material after 100 cycles at 400 mA / g is shown in the figure. Figure 7 .

[0144] Table 1 Electrochemical performance of the examples and comparative samples

[0145]

[0146] Combination Figure 1-4 It can be seen that with the increase of Al2O3 addition, Li2CO3 in the phase composition is consumed and LiAlO2 diffraction peaks appear. Further combining the SEM images of Comparative Examples 3 and 9 and Examples 5 and 6, it can be found that the pre-lithiated SiO2... x The material (its morphology is amorphous) is encapsulated by a stable outer layer. Furthermore, the diffraction peak intensity of the irreversible Li4SiO4 decreases with increasing Al2O3 addition. This is attributed to the fact that at 600–700 °C, Al2O3 consumes excess residual alkali, preventing the formation of lithium metasilicate (Li2SiO3), which acts as a buffer matrix, from further reacting to form the inert component, orthosilicate (Li4SiO4), due to excessive residual alkali. The reversible transformation of the inert component Li4SiO4 to Li2SiO3 requires a thermodynamic reaction driving force exceeding 1000 °C. Under these high-temperature conditions, SiO... x The material is prone to disproportionation reactions, which exacerbate the continuous coarsening of Si particles and severely affect its cycle stability. To verify the effect of the LiAlO2 protective layer on pre-lithiated SiO2... x The significant manifestation of the chemical stability of the material. Figure 4 The SiO2 obtained in Comparative Example 10 and Example 6 are shown.x The XRD pattern of the material shows no change in peak intensity or shape, demonstrating that the LiAlO2 coating, by isolating H2O and O2 from the air, did not alter its original phase composition. This is significant for pre-lithiated SiO2. x The material provided effective protection.

[0147] As can be seen from Table 1, SiO in its initial state x The material (Comparative Example 9) exhibited an extremely low ICE (interval efficiency) of only 60.42%, with an initial discharge specific capacity of 2041.22 mAh / g that rapidly decreased to around 150 mAh / g after 20 cycles. After 100 cycles, the capacity was almost completely lost, demonstrating extremely poor electrochemical performance. This was achieved through pre-lithiation of SiO2 with the binary lithium salt LiOH-Li2CO3. x The material's ICE only improved to around 70%, and its initial discharge specific capacity dropped to around 1400 mAh / g. Although a pre-lithiation layer of Li2SiO3 was generated and detected by XRD, pre-lithiation did not significantly improve its ICE. This is because SiO2... x The alkali metal salts remaining on the surface react with the decomposition products of the electrolyte to generate LiF and Li3PO4. This process consumes the electrolyte and the active lithium source introduced by pre-lithiation, and the resulting third-phase alkali metal salts deposit at the interface. This uneven and weak interface will cause SiO2 to... x When the material comes into contact with the electrolyte, it generates irreversible substances, initiating the formation of SiO₂. x During the delithiation reaction, the proportion of active lithium participating in the reversible process is greatly reduced, ultimately leading to SiO₂. x The ICE (In-Circuit Equivalent) performance was not significantly improved. This invention will be based on SiO2. x By introducing Al2O3 with a total mass of 10wt% (LiOH-Li2CO3), a one-step process was used to complete pre-lithiation, residual alkali removal, and coating layer construction. Electrochemical testing showed a significant increase in ICE (intercalation efficiency) to 91.37%. This is attributed to eliminating the irreversible consumption of active lithium by multiple reactions of residual alkali. The construction of the LiAlO2 coating layer further enhanced the efficiency of SiO2. x A robust protective layer forms on the surface, and even without carbon coating, a specific capacity of 331.79 mAh / g remains after 100 cycles. To further verify the effect of the formed LiAlO2 coating on SiO2... x The material exhibits good chemical stability. Constant current charge-discharge tests were performed on the material obtained in Comparative Example 10, and the corresponding ICE and capacity retention after 100 cycles remained unchanged. These results demonstrate that the pre-lithiated SiO2 coated with LiAlO2 before and after exposure... x The material also exhibits excellent electrochemical properties.

[0148] In summary, for processes employing single-lithiation lithium salts followed by stepwise removal of residual alkali, the one-step process of this invention, which completes binary eutectic lithium salt pre-lithiation, residual alkali removal, and coating layer construction, fundamentally avoids material structure evolution caused by high-temperature reactions, simplifies the residual alkali removal process, and effectively preserves SiO₂. x The material exhibits excellent pre-lithiation effect and chemical stability, and demonstrates excellent compatibility with green and environmentally friendly aqueous pulping processes.

[0149] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A one-step method for simultaneous realization of SiO x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, Includes the following steps: SiO x Materials, binary eutectic lithium salts, and nano-Al2O3 powder are mixed and ground to obtain a solid mixture. The solid mixture is pressed into a block and heat-treated under an inert atmosphere to obtain a pre-lithiated SiO2 with an outer layer of LiAlO2. x Negative electrode material.

2. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The SiO x material is amorphous SiO x or carbon-coated SiO x , where 0 < x < 2 and the particle size is 2 - 10 μm.

3. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The binary eutectic lithium salt is selected from one of LiOH-Li2CO3, LiOH-LiNO3, LiOH-LiCl, and LiNO3-LiCl.

4. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The particle size of the nano-Al2O3 powder is 15 nm.

5. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The SiO x The mass ratio of the material to the binary eutectic lithium salt is (8-9.5):(0.5-2).

6. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The amount of nano-Al2O3 powder added is equal to the amount of SiO2 added. x 1-10 wt% of the total mass of the binary eutectic lithium salt.

7. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The heat treatment temperature is 600-700℃, the holding time is 4-6 hours, and the heating rate is 2-10℃ / min.

8. The one-step method for simultaneous realization of SiO2 according to claim 1 x The method for pre-lithiation, residual alkali removal and surface coating is characterized in that, The pressing pressure is 15-20 MPa, and the holding time is 3-4 minutes.

9. A pre-lithiated SiO x The negative electrode material is characterized by, Prepared by the method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Contains the pre-lithiated SiO as described in claim 9 x Negative electrode material.

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