A Li₂C₂O₄-coated FeTiO₃ anode material, its preparation method and application

Abstract

The application discloses a Li2C2O4-coated FeTiO3 anode material and a preparation method and application thereof, and the preparation method comprises the following steps: step 1, FeTiO3 powder is prepared; step 2, Li2C2O4 powder is dissolved in a mixed solvent composed of deionized water and anhydrous ethanol in a volume ratio of (6-8):3, and then the solution is placed in a water bath and stirred after ultrasonic treatment, PVP is added, and the mixture is uniformly mixed to obtain a Li2C2O4 solution; and step 3, FeTiO3 powder is added to the Li2C2O4 solution, part of the solvent is evaporated to make Li2C2O4 precipitate and adhere to the surface of the FeTiO3 powder, the coated product obtained after solid-liquid separation is washed and dried to obtain the Li2C2O4-coated FeTiO3 anode material. The introduction of Li2C2O4 compensates for the lithium loss in the process of forming a first SEI film, constructs a lithium ion transmission channel, and the lithium ions of the cathode in the first charging can more easily reach the negative electrode to react, thereby greatly improving the initial capacity of the electrode material. Meanwhile, a protective layer is formed on the surface of the coated structure to inhibit the deactivation of the electrode material in the cycle process, compensate for the defect of low material capacity, and improve the lithium storage capacity of the material itself.

Description

Technical Field

[0001] This invention relates to the field of lithium battery anode material technology, specifically to a Li2C2O4-coated FeTiO3 anode material, its preparation method, and its application. Background Technology

[0002] Currently, graphite is the most commonly used material for commercially available anodes. Due to its compact structure, it exhibits excellent stability as a LIB (liquid lithium-ion battery) anode. However, the difficulty in lithium-ion intercalation leads to a relatively low theoretical capacity (372 mAh g). -1 While graphite exhibits good rate performance and energy density, it also presents battery safety issues. Transition metal oxides (TMOs), such as MnO3, V2O5, Co3O4, and Fe2O4, are promising LIB anode materials due to their high theoretical specific capacity and higher safety than graphite. The advantages of TMOs as anode materials include a lower lithium intercalation potential than graphite anodes, preventing the growth of lithium dendrites in graphite layers. Furthermore, bimetallic transition oxides also exhibit dual lithium storage modes, such as intercalation-conversion and conversion-alloying, which not only possess high energy density but also allow for improved electron / ion transport properties through the manipulation of the anode's crystal and electronic structures, facilitating isotropic lithium intercalation reactions.

[0003] Ferrous titanate (FeTiO3) is a wide-bandgap semiconductor material (2.74 eV) and one of the most common minerals in natural resources. Its unique octahedral structure provides excellent lithium-ion diffusion channels, resulting in a safer lithiation potential and higher specific capacity compared to graphite anodes. Mainstream optimization strategies focus on addressing the primary problem of electrode particle fragmentation and aggregation during cycling. This involves controlling material morphology, adding highly conductive substances to optimize the material structure, or introducing unique electronic structures to compensate for the rate performance and cycle stability deficiencies of FeTiO3 as a lithium-ion battery material.

[0004] As lithium-ion battery systems mature, in addition to optimizing the material structure, the problems inherent in the battery system have also attracted attention. Specifically, most materials exhibit significant active lithium loss during the initial cycles. To further increase the internal lithium storage of the entire lithium-ion battery system, pre-lithiation technology has been proposed. During the initial charge and discharge of lithium-ion batteries, a solid electrolyte interphase (SEI) film forms on the negative electrode surface, continuously consuming lithium ions. Furthermore, the decomposition and fragmentation of electrode materials during cycling leads to SEI film rupture and subsequent regeneration, resulting in further lithium loss and causing low initial coulombic efficiency (ICE) and energy density.

[0005] Therefore, a stable SEI film is crucial for developing lithium-ion batteries with high energy density and long cycle life. Pre-lithiation is an effective technique to increase the lithium content in a battery, compensating for lithium loss during cycling. Currently, increasing the content of lithium-ion compounds is commonly used to achieve this, including adding lithium alloys (such as Li) to the negative electrode material. x Si, Li x Ge, Li x Among these additives (Sn), the high reactivity of lithium itself often presents challenges in the manufacturing process.

[0006] Coating is the process of coating one material onto the surface of another to improve its performance, stability, or application characteristics. Common coating methods include solution methods, hydrothermal methods, sol-gel methods, and chemical vapor deposition. Traditional anode materials suffer from problems such as active material loss, severe volume expansion, and interfacial instability during charge and discharge. Coating methods endow anode materials with excellent ionic / electronic conductivity, elastic properties, and an inert interfacial layer to prevent capacity decay caused by the loss of effective material, thus ensuring stable and continuous operation in lithium-ion battery systems. However, selecting the appropriate coating method is extremely important for different anode materials. Summary of the Invention

[0007] Therefore, the technical problem to be solved by this invention is to provide a Li2C2O4-coated FeTiO3 anode material, its preparation method, and its application. The introduction of Li2C2O4 compensates for lithium loss during the initial SEI film formation process, constructs a lithium-ion transport channel, and allows lithium ions from the cathode to more easily reach the anode and react during the initial charging, thus significantly improving the initial capacity of the electrode material. Simultaneously, the coating structure forms a protective layer on its surface, which to some extent suppresses deactivation during electrode material cycling, compensates for the low capacity of the material, improves the lithium storage capacity of the material itself, and enhances the stability of the SEI film.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] A method for preparing a Li2C2O4-coated FeTiO3 anode material includes the following steps:

[0010] Step 1: Prepare FeTiO3 powder for later use;

[0011] Step 2: Dissolve Li2C2O4 powder in a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of (6~8):3, sonicate, and then heat and stir in a water bath. Add PVP during the stirring process and mix evenly to obtain a solution containing Li2C2O4.

[0012] Step 3: Add the FeTiO3 powder obtained in Step 1 to the Li2C2O4 solution obtained in Step 2 under continuous water bath heating and stirring. Part of the solvent evaporates, causing Li2C2O4 to crystallize and precipitate and adhere to the surface of the FeTiO3 powder. After solid-liquid separation, the coated product is obtained. After washing and drying the coated product, the Li2C2O4 coated FeTiO3 anode material is obtained.

[0013] This invention dissolves Li₂C₂O₄ powder in a mixed solvent of deionized water and anhydrous ethanol at a volume ratio of (6-8):3. After sonication, the solution is heated and stirred in a water bath. PVP is added during the stirring process. Then, FeTiO₃ powder prepared by hydrothermal method is added to the Li₂C₂O₄ solution. Throughout this process, the temperature is kept constant and the stirring is continuous and uniform. Through the combined effect of the above techniques, the crystallization process of lithium oxalate crystals on the surface of FeTiO₃ material can be controlled, ensuring that the coating process does not damage the FeTiO₃ crystal structure. At the same time, it avoids the accumulation of crystals on individual FeTiO₃ crystals, which would result in uneven or incomplete coating thickness. This process involves forming a denser, more stable, and lower impedance SEI film protective layer on the material surface. This reduces the polarization and increases the ion diffusion coefficient of the resulting Li2C2O4-coated FeTiO3 anode material, resulting in better ionic conductivity, higher energy density, and lower internal resistance. It effectively suppresses deactivation during cycling, compensates for low capacity defects, and enhances the intrinsic lithium storage performance of the material, thereby improving its cycling stability. Simultaneously, it improves the stability of the SEI film, preventing severe lattice volume expansion in subsequent cycles and suppressing FeTiO3 collapse. Furthermore, the preparation method is simple, fast, and produces stable compositions.

[0014] In the above-mentioned method for preparing Li2C2O4-coated FeTiO3 anode material, step 1, the method for preparing FeTiO3 powder is as follows:

[0015] Step 1.1: Add tetrabutyl titanate dropwise to an aqueous solution of tetrabutylammonium hydroxide until the solution is clear and colorless to obtain a titanium source solution;

[0016] Step 1.2: Add ferrous sulfate aqueous solution to titanium source solution, and after the reaction is complete, add KOH to adjust the pH to 13-14 to obtain a mixed solution;

[0017] Step 1.3: The mixed solution is subjected to a hydrothermal reaction. After the reaction is complete, the resulting precipitate is washed, dried, and ground to obtain FeTiO3 powder.

[0018] Commercially available FeTiO3 powder is mostly industrial grade and contains Fe. 3+ Ti 4Impurities such as SO42-, SiO2, and heavy metals are often micron-sized particles with wide particle size distribution, severe agglomeration, and irregular morphology, and their surfaces contain adsorbed impurities and oxide layers. In contrast, the self-made FeTiO3 powder used in this application is an impurity-free nano-sized powder with a regular, approximately hexagonal morphology. After being coated with lithium oxalate, its electrochemical performance is systematically improved.

[0019] In the preparation method of the above-mentioned Li2C2O4-coated FeTiO3 anode material, in step 1.1, the tetrabutylammonium hydroxide aqueous solution is prepared by dissolving tetrabutylammonium hydroxide in deionized water and stirring it in a water bath at 70-80℃; the concentration of tetrabutylammonium hydroxide in the aqueous solution is 0.1-0.2 mol / L; the volume ratio of tetrabutyl titanate to tetrabutylammonium hydroxide is 1:(1.6-2.2). Tetrabutyl titanate is extremely sensitive to water and reacts strongly, i.e., a white precipitate is formed immediately upon contact with water. However, the tetrabutylammonium hydroxide used in this application, as a strong organic base, is used to inhibit the formation of precipitate and avoid the reaction of titanate ions to form a precipitate.

[0020] In the above-mentioned method for preparing a Li2C2O4-coated FeTiO3 anode material, in step 1.2, the molar ratio of iron to titanium in the ferrous sulfate aqueous solution and the titanium source solution is (0.95~1.05):1; the concentration of ferrous sulfate in the ferrous sulfate aqueous solution is 0.75~0.85 mol / L; and the molar ratio of potassium hydroxide to ferrous sulfate is (4~5):1.

[0021] In the above-mentioned method for preparing a Li2C2O4-coated FeTiO3 anode material, in step 1.3, the hydrothermal reaction temperature is 210-230℃ and the hydrothermal reaction time is 11-13h.

[0022] In the above-mentioned method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material, in steps 2 and 3, the heating temperature of the water bath is 50-70℃; the concentration of Li₂C₂O₄ in the Li₂C₂O₄ solution is 0.09-0.1 mol / L. Using a water bath ensures uniform heating, avoids local overheating, and prevents excessive and rapid crystal precipitation in localized areas, ensuring the formation of a uniform coating layer on the target material surface. If the heating temperature is too low, the solvent evaporates too slowly, resulting in insufficient crystallization driving force; if the heating temperature is too high, the coating layer will be loose and easily detached, affecting the coating effect.

[0023] In step 2, the mixed solvent consists of deionized water and anhydrous ethanol in a volume ratio of (6-8):3. Lithium oxalate is insoluble in anhydrous ethanol. The mixed solvent system is optimized by adjusting the ratio of deionized water to anhydrous ethanol. The introduction of ethanol can effectively reduce the surface tension of the mixed solvent, improve the wetting performance of the mixed solvent on FeTiO3, and allow lithium oxalate to reach saturation in the mixed solvent more effectively. This makes it easier to control the crystallization process of lithium oxalate crystals on the surface of FeTiO3, which is beneficial for the formation of a fine and dense coating layer of Li2C2O4 on the surface of FeTiO3. Furthermore, PVP is added during the stirring process. The addition of PVP guides the orderly growth of the generated crystals and prevents particle agglomeration, resulting in a uniform, complete, and strongly adherent coating layer on the surface of FeTiO3, preventing the coating layer from being loose and easily detached.

[0024] The stirring rate in steps 2 and 3 is 480-500 r / min. Too slow or too fast a stirring rate will affect the crystallization process, causing the crystals to accumulate on the surface or be dispersed before they can form. At the same time, the heating and stirring time in step 2 is 10-20 minutes, and the water bath heating and stirring time in step 3 is 60 minutes to allow the crystals to fully separate.

[0025] In the above-mentioned method for preparing a Li2C2O4-coated FeTiO3 anode material, in step 3, the mass ratio of FeTiO3 powder to Li2C2O4 powder added in step 2 is (1~3):1, and the evaporation rate is 8-12 mL / h to ensure crystal quality.

[0026] A Li2C2O4-coated FeTiO3 anode material is prepared by the above-mentioned method for preparing a Li2C2O4-coated FeTiO3 anode material.

[0027] Application of a Li2C2O4-coated FeTiO3 anode material in a battery, wherein the aforementioned Li2C2O4-coated FeTiO3 anode material is used.

[0028] The above-mentioned application of Li2C2O4-coated FeTiO3 anode material in a battery involves thoroughly grinding the Li2C2O4-coated FeTiO3 anode material and acetylene black, then adding sodium alginate and grinding again. The mass ratio of Li2C2O4-coated FeTiO3 anode material, acetylene black, and sodium alginate is 8:1:1. Subsequently, deionized water is added dropwise to prepare a slurry. The slurry is then coated onto copper foil, dried, and cut to serve as the working electrode. A polypropylene microporous membrane is used as the separator, a lithium metal sheet as the counter electrode, and 1 mol / L LiPF6 and EC:DMC:DEC in a volume ratio of 1:1:1 are used as the electrolyte to assemble the battery.

[0029] The technical solution of the present invention achieves the following beneficial technical effects:

[0030] (1) In this invention, Li2C2O4 powder is dissolved in a mixed solvent composed of deionized water and anhydrous ethanol in a volume ratio of (6~8):3. After sonication, the solution is heated and stirred in a water bath. PVP is added during the stirring process. Then, FeTiO3 powder prepared by hydrothermal method is added to the Li2C2O4 solution. During this process, the temperature is kept constant and the stirring is carried out at a constant speed. Through the combined effect of the above technical means, the crystallization process of lithium oxalate crystals on the surface of FeTiO3 material can be controlled, so that the coating process does not damage the FeTiO3 crystal structure. At the same time, it is avoided that the crystallization process accumulates on a single FeTiO3 crystal, resulting in uneven coating thickness or unevenness. The process achieves a complete and denser SEI film protective layer with lower impedance on the material surface. This reduces the polarization and increases the ion diffusion coefficient of the resulting Li2C2O4-coated FeTiO3 anode material, resulting in better ionic conductivity, higher energy density, and lower internal resistance. It effectively suppresses deactivation during cycling, compensates for low capacity defects, and enhances the intrinsic lithium storage performance of the material, thereby improving its cycling stability. Simultaneously, it improves SEI film stability, preventing severe lattice volume expansion in subsequent cycles and suppressing FeTiO3 collapse. Furthermore, the preparation method is simple, fast, and produces stable components. The lithium ions generated from the decomposition of lithium oxalate compensate for lithium loss during the initial SEI film formation and construct lithium-ion transport channels, facilitating efficient migration of cathode lithium ions to the anode during the first charge, significantly improving the initial capacity of the electrode material and increasing the battery energy density.

[0031] (2) This invention provides a direct lithium source for the original material by coating the FeTiO3 surface with Li2C2O4, which greatly reduces the loss of initial capacity and improves the energy density of the battery. At the same time, it forms a film structure on the surface, which disperses the material particles and avoids direct contact and agglomeration. It also reduces the direct contact between the electrolyte and the surface of the active material, thus reducing the occurrence of side reactions. In addition, lithium oxalate and its decomposition products have good lithium-ion conductivity, and the interface layer can serve as a "bridge" for the transport of lithium ions between the electrolyte and the negative electrode active material.

[0032] (3) Lithium oxalate (Li2C2O4) has good air stability and high theoretical capacity. Furthermore, the decomposition process of Li2C2O4 is relatively long, and it gradually releases Li. +Therefore, it can continuously play a role in the battery charging and discharging process according to the potential change, making it an excellent candidate for lithium replenishment agent. This invention uses a simple solution method, where the solution is heated and evaporated in a water bath to reach a supersaturated state, allowing lithium oxalate to gradually crystallize on the surface. The solution method for Li2C2O4 coating is chosen not only because it is uniform, controllable, and low-cost, but also because it can endow the material surface with new functions through simple chemical reactions without damaging the original structure. This simple process can easily be scaled up from laboratory research to industrial production. More importantly, Li2C2O4 is a water-soluble salt, and the solution method can directly dissolve it using water or an ethanol-water mixture, without the need for complex complexing agents. This method is less likely to introduce difficult-to-remove impurities, which helps maintain the high purity of the coating layer. Furthermore, the solution method typically involves solvent evaporation or precipitation at room temperature or lower heating temperatures, which avoids excessive oxidation of the FeTiO3 surface and prevents premature decomposition of Li2C2O4 during the coating process, ensuring the integrity of the coating layer. The sol-gel method requires high heat treatment temperatures, which may cause premature decomposition of Li₂C₂O₄; hydrothermal / solvothermal methods for preparing Li₂C₂O₄ tend to crystallize into large, bulky crystals, making it difficult to form a uniform thin film coating; and chemical vapor deposition causes Li₂C₂O₄ to decompose before sublimation upon heating. Therefore, the solution method is the most convenient and suitable method for coating Li₂C₂O₄.

[0033] (4) Compared with previously reported FeTiO3 anode materials, the battery achieves better performance at a current density of 0.1 A g. -1 After 200 cycles, the FeTiO3-Li2C2O4 sample (L 0.5 The capacity decay of FTO was significantly mitigated, reaching 1043.7 mAh g⁻¹. -1 Under high current long-cycle conditions (1 A g) -1 After 1000 cycles of current density cycling), the FeTiO3-Li2C2O4 sample (L 0.5 The capacity of FTO is 205mAh g. -1 . Attached Figure Description

[0034] Figure 1 Different proportions of Li2C2O4-coated FeTiO3 anode materials (L) prepared in Example 1 0.3 FTO, L 0.5 XRD patterns of FTO, L1FTO and FeTiO3 (FTO);

[0035] Figure 2 The Li2C2O4-coated FeTiO3 anode material prepared in Example 1 (L 0.5 TEM image of FTO;

[0036] Figure 3 The Li2C2O4-coated FeTiO3 anode material prepared in Example 1 (L 0.5 HRTEM topography of FTO;

[0037] Figure 4 Different proportions of Li2C2O4-coated FeTiO3 anode materials (L) prepared in Example 1 0.3 FTO, L 0.5 Cyclic capacity diagrams of FTO, L1FTO and FeTiO3 (FTO) (current magnitude 0.1 A g) -1 );

[0038] Figure 5 Different proportions of Li2C2O4-coated FeTiO3 anode materials (L) prepared in Example 1 0.3 FTO, L 0.5 Cyclic capacity diagrams of FTO, L1FTO and FeTiO3 (FTO) (current magnitude 1 A g) -1 );

[0039] Figure 6 Different proportions of Li2C2O4-coated FeTiO3 anode materials (L) prepared in Example 1 0.3 FTO, L 0.5 Rate performance diagrams of FTO, L1FTO and FeTiO3 (FTO) (current magnitude 0.1 A g) -1 ~2 A g -1 );

[0040] Figure 7 The Li2C2O4-coated FeTiO3 anode material prepared in Example 1 (L 0.5 First-cycle constant current charge-discharge curves of FTO and FeTiO3 (FTO) (current magnitude 0.1 A g) -1 );

[0041] Figure 8 The Li2C2O4-coated FeTiO3 anode material prepared in Example 1 (L 0.5 FTO) constant current charge-discharge curve (current magnitude is 0.1 A g) -1 );

[0042] Figure 9 Different proportions of Li2C2O4-coated FeTiO3 anode materials (L) prepared in Example 1 0.3 FTO, L 0.5 Electrochemical impedance spectroscopy of FTO, L1FTO and FeTiO3 (FTO);

[0043] Figure 10 (a) The Li2C2O4-coated FeTiO3 anode material (L) prepared in Example 1 0.5 (a) CV curves at different scan rates (scan rate range: 0.1 mV / s - 2 mV / s) for FTO; (b) L obtained in Example 1 0.5 (c) The b-values ​​of the oxidation and reduction peaks of the FTO sample; (c) The pseudocapacitive contribution calculated from the b-values ​​at different current densities; Figure 10 (d) represents the diffusion correlation factor of the redox peak;

[0044] Figure 11 (a), (d), and (g) are L obtained in Example 1, respectively. 0.5 TEM images at different magnifications after one FTO cycle; (b), (e), and (h) are L-type images obtained in Example 1, respectively. 0.5 TEM images at different magnifications after 10 FTO cycles; (c), (f), and (i) are L obtained in Example 1, respectively. 0.5 TEM images at different magnifications after 50 FTO cycles;

[0045] Figure 12 Li₂C₂O₄-coated FeTiO₃ anode materials prepared with different solvents were tested at a current of 0.1 A g. -1 The following is a cyclic capacity graph;

[0046] Figure 13 Li₂C₂O₄-coated FeTiO₃ anode materials prepared with different solvents at a current of 1 A g -1 The following is a cyclic capacity graph;

[0047] Figure 14 Rate performance diagrams of Li₂C₂O₄-coated FeTiO₃ anode materials prepared with different solvents (current magnitude: 0.1 A g) -1 ~2 A g -1 ). Detailed Implementation

[0048] Example 1

[0049] A method for preparing a Li2C2O4-coated FeTiO3 anode material includes the following steps:

[0050] Step 1: Prepare FeTiO3 powder for later use;

[0051] Step 1.1: Measure 5.2 ml of tetrabutylammonium hydroxide (40% concentration) and dissolve it in 60 ml of deionized water. Stir in an 80°C water bath for 10 min to obtain a tetrabutylammonium hydroxide aqueous solution. Then, slowly add 2.718 ml of tetrabutyl titanate dropwise (0.3 mL / s) to the tetrabutylammonium hydroxide aqueous solution using a dropper until the solution is transparent and colorless to obtain the titanium source solution.

[0052] Step 1.2: Weigh 2.224 g of ferrous sulfate heptahydrate and dissolve it in 10 ml of deionized water. After stirring evenly, an aqueous solution of ferrous sulfate heptahydrate is obtained. Under water bath heating and stirring, the obtained aqueous solution of ferrous sulfate heptahydrate is added to the titanium source solution. After reacting for 30 min, 2 g of KOH solid powder is added to adjust the pH. After 10 min, the resulting mixed solution is transferred to a polytetrafluoroethylene-lined reactor for hydrothermal reaction (held at 220℃ for 12 h). After the reaction is complete, the obtained precipitate is repeatedly washed with deionized water and ethanol, and dried in an oven at 80℃ for 12 h. The obtained powder is ground to obtain FeTiO3 powder, denoted as FTO.

[0053] Step 2: Dissolve Li2C2O4 powder in a mixed solvent consisting of 35 mL deionized water and 15 mL anhydrous ethanol. After sonication for 10 min, place it in a 60℃ water bath and stir (stirring rate 480 r / min). Add 0.2 g PVP (polyvinylpyrrolidone) to prevent particle agglomeration. Stir for 10 minutes. After mixing evenly, a homogeneous saturated Li2C2O4 solution is obtained. The concentration of Li2C2O4 in the Li2C2O4 solution is 0.09 mol / L.

[0054] Step 3: Under continuous water bath heating and stirring (the water bath heating temperature and stirring rate are the same as in Step 2), add the FeTiO3 powder prepared in Step 1 to the Li2C2O4 solution obtained in Step 2. The mass ratio of FeTiO3 powder to Li2C2O4 powder in Step 2 is 3:1, 2:1, and 1:1, respectively. Stir for 60 min. The evaporation rate corresponds to different mass ratios of FeTiO3 powder to Li2C2O4 powder in Step 2 (3:1, 2:1, 1:1) of 8, 10, and 12 mL / h, respectively. Partial solvent evaporation causes Li2C2O4 crystals to precipitate and adhere to the surface of FeTiO3 powder. After solid-liquid separation, the coated product is obtained. The coated product is washed with deionized water and anhydrous ethanol, respectively, and then dried in a 60℃ oven for 12 h to obtain Li2C2O4 coated FeTiO3 anode materials with different proportions. The samples are ground and denoted as L. 0.3 FTO, L 0.5 FTO and L1FTO are available for backup.

[0055] The battery assembly method is as follows: First, Li₂C₂O₄ coated FeTiO₃ anode material and acetylene black in different proportions are thoroughly ground and mixed in a mortar. Then, sodium alginate (SA) is added and further ground and mixed, with the ratio of the three being 8:1:1. 4-5 mL of deionized water is added to prepare a slurry, which is then coated onto copper foil and dried in a vacuum drying oven at 80 °C for 12 h. The dried foil is then cut to serve as the working electrode. The electrolyte consists of 1 mol / L LiPF₆ and EC:DMC:DEC (volume ratio 1:1:1). A polypropylene (PP) microporous membrane is used as the separator, and lithium metal sheets are used as the electrodes. Finally, the 2032 button battery is assembled in an argon-protected glove box.

[0056] The L prepared above 0.3 FTO, L 0.5 The morphological characterization of FTO, L1FTO, and FeTiO3 anode materials without Li2C2O4 coating was compared and analyzed as follows:

[0057] like Figure 1 The comparison with the standard PDF card (PDF#22-0169) shows that L... 0.3 FTO, L 0.5 The characteristic peaks of FTO and L1FTO at 2θ = 23.80°, 32.52°, 35.25°, and 53.04° correspond to the (1 1 0), (2 1 1), (-1 1 0), and (3 2 1) crystal planes of FeTiO3, respectively. The diffraction peaks of the three samples are sharp and elongated, maintaining a high degree of consistency with the diffraction pattern of the FeTiO3 sample, with no new diffraction peaks appearing. This indicates that the coating process does not damage its crystal structure; the core peak shifts to a higher angle, and the interplanar spacing shrinks. In other words, the original material is modulated by the coating layer, resulting in interfacial interactions.

[0058] Figure 2 The results show that the Li2C2O4-coated FeTiO3 anode material (L 0.5 FTO exhibits a relatively obvious hexagonal structure.

[0059] Figure 3 The display shows that L 0.5 The FTO particles have an irregular amorphous film structure on their surface. The region with a lower face spacing of 2.50 Å corresponds to the (-1 1 0) crystal plane of FeTiO3, indicating that Li2C2O4 is uniformly distributed on the FeTiO3 surface.

[0060] Assembled Li₂C₂O₄-coated FeTiO₃ anode materials in different proportions were used as working electrodes and connected to the blue electric current testing system. The voltage window was set to 0.01~3V, and the current density was selected to be 0.1 A g. -1Test constant current charge-discharge cycles. Continue setting the current density to 0.1 A g. -1 ~2 A g -1 The test involved charge-discharge cycles at various rates. A detailed performance analysis is as follows:

[0061] like Figure 4 The results showed that, after 200 cycles, the highest Li₂C₂O₄-coated FeTiO₃ anode material exhibited a maximum capacity of 1043.7 mAh g⁻¹. -1 The high capacity performance of FeTiO3 was achieved, while the capacity of FeTiO3 decreased to 742.6 mAh g. -1 .

[0062] Figure 5 The display shows that in 1 Ag -1 At different current densities, the highest capacity of Li₂C₂O₄-coated FeTiO₃ anode materials after 1000 cycles was 205 mAh g⁻¹. -1 Still superior to FeTiO3 (59 mAh g) -1 ).

[0063] Figure 6 The display shows that as the current density increases from 100, 200, 500, 1000 to 2000 mA g -1 Compared to FeTiO3, the discharge of FeTiO3 anode materials coated with Li2C2O4 in different proportions showed relatively stable performance. This indicates that the FeTiO3 anode materials coated with Li2C2O4 in different proportions have better rate performance.

[0064] Figure 7 The results show that the Li2C2O4-coated FeTiO3 anode material L 0.5 FTO has a flatter voltage plateau compared to FTO, indicating reduced polarization, which is beneficial for improving energy density. Its discharge plateau original electrode capacity is 1431 mAhg. -1 After introducing Li₂C₂O₄, the electrode capacity was significantly increased to 1645.9 mAh g⁻¹. -1 .

[0065] Figure 8 The display shows that L 0.5 The charge-discharge plateau of the FTO constant current charge-discharge curve changed significantly with cycling. As the number of cycles increased, its charging capacity and discharging capacity remained basically consistent, indicating that the battery material has good reversibility after cycling.

[0066] Figure 9 The results show that, through the construction of the coating layer, the electrolyte resistance (R0) of FeTiO3 anode materials with different proportions of Li2C2O4 coating is significantly higher than that of the FeTiO3 sample. e) and charge transfer impedance (R ct The value of ) decreases significantly, and the significant reduction in diffusion resistance (W0-R) corresponds to the increase in ion diffusion coefficient.

[0067] Figure 10 As shown in (a), L 0.5 The CV curves of FTO at various scan rates showed similar trends with no obvious polarization, indicating that the electrode material exhibited both battery and pseudocapacitive properties during cycling. The coating layer improved the lithium-ion diffusion coefficient of the sample, promoting lithium-ion transport efficiency and thus enhancing the battery's cycling performance. The contribution of pseudocapacitance increased with increasing scan rate. Figure 10 (b) is L 0.5 The b-values ​​of the oxidation and reduction peaks of the FTO sample indicate that when the b-value is close to 0.5, the electrode material exhibits battery properties and the process is diffusion-controlled. When the b-value is close to 1, the electrode material exhibits pseudocapacitive properties. Figure 10 In the figure (c), the pseudocapacitive contribution calculated by the b value under different current densities is shown. The higher the contribution, the faster the charging speed and the longer the lifespan. Figure 10 In the figure (d), the diffusion correlation factor of the redox peak is represented. The larger the factor, the better the diffusion kinetics performance.

[0068] Figure 11 In the middle (a), (d), and (g), respectively, L 0.5 TEM images at different magnifications after one FTO cycle; (b), (e), and (h) are L... 0.5 TEM images at different magnifications after 10 FTO cycles; (c), (f), and (i) represent L... 0.5 TEM images at different magnifications after 50 FTO cycles. During the first cycle, Fe metallic phase rapidly precipitates and surrounds the grains. After 10 cycles, some of it forms Fe2O3, while the rest cannot be completely reduced to Fe during the discharge process. 2+ This results in the formation of Fe3O4 with coexisting dual valence states. After 50 cycles, Fe and Fe2O3 are deposited on the particle surface. Throughout the cycle, the material undergoes a process of cracking-repairing-cracking, but the whole remains intact in a sheet-like shape without severe volume expansion. This indicates that the coating interface plays a role in inhibiting the collapse of the material.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that in step 2, Li2C2O4 powder is dissolved in 50mL of deionized water, and in step 3, the mass ratio of FeTiO3 powder to Li2C2O4 powder in step 2 is 2:1. The remaining steps are the same as in Example 1.

[0071] like Figure 12As shown, at 0.1 Ag -1 Under different current densities, Li₂C₂O₄-coated FeTiO₃ anode materials prepared with different solvents were tested for 200 cycles. Example 1 showed the Li₂C₂O₄-coated FeTiO₃ anode material prepared with ethanol and water as solvents. 0.5 FTO exhibited a maximum capacity of 1043.7 mAh / g after 200 cycles of cycling. -1 The high capacity performance of the original material was demonstrated, while the capacity of the Li2C2O4-coated FeTiO3 anode material prepared with water as the solvent in Comparative Example 1 decreased to 658.1 mAh g⁻¹. -1 .

[0072] like Figure 13 As shown, in 1 Ag -1 At different current densities, Li₂C₂O₄-coated FeTiO₃ anode materials prepared with different solvents were compared after 700 cycles. Example 1 shows the Li₂C₂O₄-coated FeTiO₃ anode material prepared with ethanol and water as solvents. 0.5 The highest capacity of FTO is 286 mAh g. -1 It is still superior to the Li2C2O4-coated FeTiO3 anode material prepared with water as solvent in Comparative Example 1 (132 mAh g). -1 ).

[0073] like Figure 14 As shown, with current densities ranging from 100, 200, 500, 1000 to 2000 mA g -1 Example 1: Li2C2O4-coated FeTiO3 anode material prepared using ethanol and water as solvents. 0.5 The discharge stability of FTO is better than that of the Li2C2O4-coated FeTiO3 anode material prepared with water as solvent in Comparative Example 1.

[0074] Because Li2C2O4 has high solubility in water, it is difficult to control the crystallization process of lithium oxalate crystals on the surface of FeTiO3 material. This can result in excessively large crystal size or uneven or incomplete thickness of the crystalline layer coating on the FeTiO3 surface. Furthermore, due to the slightly high surface tension of water, the wetting effect on FeTiO3 is poor, which also leads to poor adhesion of Li2C2O4 coating on the FeTiO3 surface, affecting subsequent cycling performance.

[0075] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material, characterized in that, Includes the following steps: Step 1: Prepare FeTiO3 powder for later use; Step 2: Dissolve Li2C2O4 powder in a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of (6~8):3, sonicate, and then heat and stir in a water bath. Add PVP during stirring and mix evenly to obtain Li2C2O4 solution. Step 3: Add the FeTiO3 powder obtained in Step 1 to the Li2C2O4 solution obtained in Step 2 under continuous water bath heating and stirring. Part of the solvent evaporates, causing Li2C2O4 to crystallize and precipitate and adhere to the surface of the FeTiO3 powder. After solid-liquid separation, the coated product is obtained. After washing and drying the coated product, the Li2C2O4 coated FeTiO3 anode material is obtained.

2. The method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material according to claim 1, characterized in that, In step 1, the preparation method of FeTiO3 powder is as follows: Step 1.1: Add tetrabutyl titanate dropwise to an aqueous solution of tetrabutylammonium hydroxide until the solution is clear and colorless to obtain a titanium source solution; Step 1.2: Add ferrous sulfate aqueous solution to titanium source solution, and after the reaction is complete, add KOH to adjust the pH to 13-14 to obtain a mixed solution; Step 1.3: The mixed solution is subjected to a hydrothermal reaction. After the reaction is complete, the resulting precipitate is washed, dried, and ground to obtain FeTiO3 powder.

3. The method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material according to claim 2, characterized in that, In step 1.1, the tetrabutylammonium hydroxide aqueous solution is prepared by dissolving tetrabutylammonium hydroxide in deionized water and stirring it in a water bath at 70~80℃; the concentration of tetrabutylammonium hydroxide in the tetrabutylammonium hydroxide aqueous solution is 0.1~0.2mol / L; the volume ratio of tetrabutyl titanate to tetrabutylammonium hydroxide is 1:(1.6-2.2).

4. The method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material according to claim 2, characterized in that, In step 1.2, the molar ratio of iron to titanium in the ferrous sulfate aqueous solution and the titanium source solution is (0.95~1.05):1; the concentration of ferrous sulfate in the ferrous sulfate aqueous solution is 0.75~0.85mol / L; and the molar ratio of potassium hydroxide to ferrous sulfate is (4~5):

1.

5. The method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material according to claim 2, characterized in that, In step 1.3, the hydrothermal reaction temperature is 210-230℃ and the hydrothermal reaction time is 11-13h.

6. The method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material according to claim 1, characterized in that, In steps 2 and 3, the heating temperature of the water bath is 50~70℃; the heating and stirring time in step 2 is 10-20 minutes, and the heating and stirring time in step 3 is 60 minutes; the concentration of Li2C2O4 in the Li2C2O4 solution is 0.09-0.1 mol / L.

7. The method for preparing a Li₂C₂O₄-coated FeTiO₃ anode material according to claim 1, characterized in that, In step 3, the mass ratio of FeTiO3 powder to Li2C2O4 powder added in step 2 is (1~3):1; the evaporation rate is 8-12 mL / h.

8. A Li₂C₂O₄-coated FeTiO₃ anode material, characterized in that, It is prepared by the method for preparing a Li2C2O4-coated FeTiO3 anode material according to any one of claims 1 to 7.

9. The application of a Li₂C₂O₄-coated FeTiO₃ anode material in a battery, characterized in that, The FeTiO3 anode material coated with Li2C2O4 as described in claim 8 is used.

10. The application of the Li2C2O4-coated FeTiO3 anode material according to claim 9 in a battery, characterized in that, After thoroughly grinding Li2C2O4-coated FeTiO3 anode material and acetylene black, sodium alginate was added and ground again. The mass ratio of Li2C2O4-coated FeTiO3 anode material, acetylene black, and sodium alginate was 8:1:

1. Deionized water was then added dropwise to prepare a slurry. The slurry was then coated onto copper foil, dried, and cut to serve as the working electrode. A polypropylene microporous membrane was used as the separator, a lithium metal sheet as the counter electrode, and 1 mol / L LiPF6 and EC:DMC:DEC in a volume ratio of 1:1:1 were used as the electrolyte to assemble the battery.

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