Method for preparing composite negative electrode material

Abstract

The application discloses a preparation method of a composite negative electrode material, and comprises the following steps: adding a niobium source, a fluorine source, a titanium source, a lithium source, a carbon source, graphite and a dispersing agent into a solvent, uniformly mixing, and then performing spray drying and calcination to obtain the composite negative electrode material. 5+ and F ‑ , Nb 5+ and F ‑ can be uniformly introduced into the LTO crystal lattice, Nb 5+ and Ti 4+ occur substitution reaction to generate Ti 3+ , so that the crystal lattice is slightly expanded, the Li + channel is widened, the electronic conductivity is improved by 10 2 -10 3 times, F ‑ substitutes O 2‑ , the Ti 3+ / Ti 4+ ratio is increased, the crystal lattice distortion energy is reduced, and the oxygen precipitation is inhibited; and the slightly fluorine-rich ratio can balance the doping efficiency and inhibit the impurity phase, so that the ionic conductivity is improved by 5-10 times, and the graphite serves as the core of the material, the LTO doping and the carbon layer coating are supplemented, the interface impedance is reduced, and the stability of the material is higher.

Description

Technical Field

[0001] This invention relates to the field of negative electrode technology, and in particular to a method for preparing a composite negative electrode material. Background Technology

[0002] Graphite is currently the most technologically mature and widely penetrated core anode material in the lithium-ion battery industrialization system. Its ability to achieve large-scale industrial application is primarily attributed to its unique layered crystal topology, highly reversible lithium intercalation / deintercalation electrochemical response characteristics, excellent physicochemical structural stability, and good process adaptability. This allows it to fully meet the core technical requirements of long cycle life, high electrochemical efficiency, and high structural stability for batteries in various scenarios such as power, energy storage, and consumer electronics. However, graphite undergoes volume changes during lithium-ion intercalation and deintercalation, leading to lower-than-expected cycle performance, and it is prone to lithium plating during high-current fast charging.

[0003] Compared to graphite, LTO has the following advantages: (1) It undergoes almost no volume change during lithium-ion insertion and extraction, exhibiting excellent cycle performance, hence it is also known as a "zero-strain material". (2) Due to its high lithium insertion platform (1.55V vs Li / Li+), it can effectively avoid the formation of SEI film and the safety issues caused by lithium plating. However, the theoretical specific capacity of LTO material is only 175 mAh / g, significantly lower than graphite's 372 mAh / g, and its low electronic and ionic conductivity also hinders its rate performance, limiting its commercial application. Therefore, it is necessary to propose a new solution to address these issues. Summary of the Invention

[0004] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide a method for preparing composite anode materials, the resulting anode materials possessing excellent properties such as high specific capacity, high rate capability, low expansion, long cycle life, and high safety.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a composite negative electrode material includes the following steps: (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to solvent, wherein the mass of niobium source and fluorine source accounts for 0.03%-0.07% of the mass of solute, the mass of titanium source and lithium source accounts for 2%-4% of the mass of solute, the mass of carbon source accounts for 3%-5% of the mass of solute, the mass of graphite accounts for 90%-94% of the mass of solute, and the mass of dispersant accounts for 0.5%-1.5% of the mass of solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28%-32wt%, the pH of the slurry is 8.5-9.0, and the temperature is 40-50℃. (2) Spray dry the slurry obtained in step (1). The inlet temperature of the spray dryer is 230-250℃, the outlet temperature of the spray dryer is 95-150℃, the rotation speed of the atomizing disc is 18000-22000rpm, and the feed rate is 6-8mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite anode material.

[0006] As a preferred embodiment, the niobium source is Nb(HC₂O₄)₅ or NbCl₅, and the fluorine source is NH₄F or LiF, and Nb 5+ and F - The mass ratio is 1:1.3.

[0007] As a preferred embodiment, the titanium source is anatase TiO2 or Ti(OC4H9)4, the titanium source has a D50 of 50-200 nm, and the lithium source is LiOH•H2O or Li2CO3, the lithium source has a D50 of 1-5 μm, and Li + and Ti 4+ The mass ratio is 4:5.

[0008] As a preferred embodiment, the carbon source is glucose or pitch.

[0009] As a preferred embodiment, the graphite is artificial graphite or natural graphite with a D50 of 5-20 μm.

[0010] As a preferred embodiment, the dispersant is PEG.

[0011] As a preferred embodiment, the inert atmosphere is one of helium, argon, and nitrogen.

[0012] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution: Nb is introduced into the system simultaneously 5+ and F - Nb 5+ and F - Both can be uniformly inserted into the LTO lattice, Nb 5+ With Ti 4+ A substitution reaction occurs, producing Ti. 3+ This causes the lattice to expand slightly, Li + The channel is widened, and the electron conductivity is increased to 10. 2 -103 A multiple increase, combined with F - Replace O 2- Improve Ti 3+ / Ti 4+ The proportion of fluorine reduces lattice distortion energy and suppresses oxygen evolution; moreover, the fluorine-rich ratio can balance doping efficiency and suppress impurity phases, resulting in a 5-10 times increase in ionic conductivity. Furthermore, graphite, as the core of the material, is supplemented by LTO doping and carbon layer coating, which reduces the interfacial impedance and makes the material more stable.

[0013] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments: Attached Figure Description Figure 1 This is a SEM image of the first embodiment of the present invention. Detailed Implementation

[0014] This invention discloses a method for preparing a composite negative electrode material, which includes the following steps: (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.03%-0.07% of the mass of the solute, the mass of the titanium source and lithium source accounts for 2%-4% of the mass of the solute, the mass of the carbon source accounts for 3%-5% of the mass of the solute, the mass of the graphite accounts for 90%-94% of the mass of the solute, and the mass of the dispersant accounts for 0.5%-1.5% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28%-32wt%, the pH of the slurry is 8.5-9.0, and the temperature is 40-50℃. The titanium source is anatase TiO2 or Ti(OC4H9)4, and the D50 of the titanium source is 50-200nm. The lithium source is LiOH•H2O or Li2CO3, and the D50 of the lithium source is 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5 or NbCl5, the fluorine source is NH4F or LiF, and Nb 5 + and F - The mass ratio is 1:1.3, the carbon source is glucose or pitch, the graphite is artificial graphite or natural graphite with D50=5-20μm, and the dispersant is PEG.

[0015] (2) Spray dry the slurry obtained in step (1). The inlet temperature of the spray dryer is 230-250℃, the outlet temperature of the spray dryer is 95-150℃, the rotation speed of the atomizing disc is 18000-22000rpm, and the feed rate is 6-8mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is increased to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is increased to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is increased to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, it is naturally cooled to room temperature to obtain the composite anode material. The inert atmosphere is one of helium, argon, and nitrogen. Segmented calcination can effectively improve the composite anode material. The material's performance is as follows: Holding at 200℃ allows residual free water to slowly vaporize and dissipate, preventing bursting due to rapid boiling and vaporization of water, which could lead to the peeling of the LTO, carbon, and graphite interfaces. Holding at 450℃ allows the fluorine and niobium sources to slowly decompose, preventing excessive vaporization of fluorine and agglomeration of niobium oxides, thus preventing elemental doping failure and impurity phase formation. It also effectively pre-carbonizes the carbon source, preventing the instantaneous and violent pyrolysis of organic matter that could cause carbon coating failure. Holding at 780℃ maintains LTO crystallization and Nb... 5+ / F - The balance between the three processes of solid solution, carbon source carbonization, and thermal runoff is crucial. Too low a holding temperature leads to incomplete LTO crystallization, dopant solid solution failure, and insufficient coating carbonization; while too high a holding temperature causes rapid coarsening of LTO grains and damage to Nb already dissolved into the crystal lattice. 5+ / F - Extracted from the crystal lattice and over-carbonized.

[0016] The following detailed description is provided in conjunction with several embodiments and comparative examples.

[0017] Example 1 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.04% of the mass of the solute, the mass of the titanium source and lithium source accounts for 3% of the mass of the solute, the mass of the carbon source accounts for 4% of the mass of the solute, the mass of the graphite accounts for 92% of the mass of the solute, and the mass of the dispersant accounts for 0.96% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 30 wt%, the pH of the slurry is 8.8, and the temperature is 45 °C. The titanium source is anatase TiO2 with a D50 of 50-200 nm. The lithium source is LiOH•H2O with a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is LiF, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is glucose, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0018] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 240℃, the outlet temperature of the spray drying is 120℃, the rotation speed of the atomizing disc is 18000rpm, and the feed rate is 7mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite anode material. The inert atmosphere is helium.

[0019] Example 2 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.03% of the mass of the solute, the mass of the titanium source and lithium source accounts for 3.1% of the mass of the solute, the mass of the carbon source accounts for 3.8% of the mass of the solute, the mass of the graphite accounts for 92.57% of the mass of the solute, and the mass of the dispersant accounts for 0.5% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28 wt%, the pH of the slurry is 8.5, and the temperature is 40-50℃. The titanium source is Ti(OC4H9)4 with a D50 of 50-200 nm, the lithium source is Li2CO3 with a D50 of 1-5 μm, and the Li2CO3 has a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is LiF, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is pitch, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0020] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 230℃, the outlet temperature of the spray drying is 95℃, the rotation speed of the atomizing disk is 22000rpm, and the feed rate is 6mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite negative electrode material. The inert atmosphere is nitrogen.

[0021] Example 3 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.07% of the mass of the solute, the mass of the titanium source and lithium source accounts for 2.5% of the mass of the solute, the mass of the carbon source accounts for 5% of the mass of the solute, the mass of the graphite accounts for 90.93% of the mass of the solute, and the mass of the dispersant accounts for 1.5% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 32 wt%, the pH of the slurry is 9.0, and the temperature is 40 °C. The titanium source is Ti(OC4H9)4, the D50 of the titanium source is 50-200 nm, the lithium source is LiOH•H2O, the D50 of the lithium source is 1-5 μm, and the Li... + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is LiF, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is pitch, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0022] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 240℃, the outlet temperature of the spray drying is 100℃, the rotation speed of the atomizing disk is 18000rpm, and the feed rate is 8mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite negative electrode material. The inert atmosphere is nitrogen.

[0023] Example 4 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.05% of the mass of the solute, the mass of the titanium source and lithium source accounts for 2% of the mass of the solute, the mass of the carbon source accounts for 4% of the mass of the solute, the mass of the graphite accounts for 93% of the mass of the solute, and the mass of the dispersant accounts for 0.95% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28%-32wt%, the pH of the slurry is 8.5, and the temperature is 43℃. The titanium source is anatase TiO2 with a D50 of 50-200nm. The lithium source is Li2CO3 with a D50 of 1-5 μm. + and Ti 4+The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is NH4F, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is glucose, the graphite is natural graphite with D50=5-20μm, and the dispersant is PEG.

[0024] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 250℃, the outlet temperature of the spray drying is 150℃, the rotation speed of the atomizing disk is 18000rpm, and the feed rate is 8mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite negative electrode material. The inert atmosphere is nitrogen.

[0025] Example 5 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.06% of the mass of the solute, the mass of the titanium source and lithium source accounts for 2% of the mass of the solute, the mass of the carbon source accounts for 4% of the mass of the solute, the mass of the graphite accounts for 94% of the mass of the solute, and the mass of the dispersant accounts for 0.94% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28%-32wt%, the pH of the slurry is 8.7, and the temperature is 40℃. The titanium source is anatase TiO2 with a D50 of 50-200nm. The lithium source is Li2CO3 with a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is NH4F, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is glucose, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0026] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 230℃, the outlet temperature of the spray drying is 95℃, the rotation speed of the atomizing disc is 18000rpm, and the feed rate is 6mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite negative electrode material. The inert atmosphere is argon.

[0027] Example 6 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.04% of the mass of the solute, the mass of the titanium source and lithium source accounts for 3.5% of the mass of the solute, the mass of the carbon source accounts for 3.2% of the mass of the solute, the mass of the graphite accounts for 92.26% of the mass of the solute, and the mass of the dispersant accounts for 1% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28%-32wt%, the pH of the slurry is 9.0, and the temperature is 45℃. The titanium source is Ti(OC4H9)4 with a D50 of 50-200nm. The lithium source is LiOH•H2O with a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is NH4F, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is glucose, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0028] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 250℃, the outlet temperature of the spray drying is 150℃, the rotation speed of the atomizing disk is 22000rpm, and the feed rate is 8mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite anode material. The inert atmosphere is helium.

[0029] Comparative Example 1 (1) Add a titanium source, a lithium source, a carbon source, graphite, and a dispersant to a solvent. The mass of the titanium source and lithium source accounts for 3.04% of the mass of the solute, the mass of the carbon source accounts for 4% of the mass of the solute, the mass of the graphite accounts for 92% of the mass of the solute, and the mass of the dispersant accounts for 0.96% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 30 wt%, the pH of the slurry is 8.8, and the temperature is 45 °C. The titanium source is anatase TiO2 with a D50 of 50-200 nm. The lithium source is LiOH•H2O with a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the carbon source is glucose, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0030] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 240℃, the outlet temperature of the spray drying is 120℃, the rotation speed of the atomizing disc is 18000rpm, and the feed rate is 7mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite anode material. The inert atmosphere is helium.

[0031] Comparative Example 2 (1) Add a titanium source, a carbon source, graphite and a dispersant to a solvent. The mass of the titanium source accounts for 3.04% of the mass of the solute, the mass of the carbon source accounts for 4% of the mass of the solute, the mass of the graphite accounts for 92% of the mass of the solute, and the mass of the dispersant accounts for 0.96% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 30 wt%, the pH of the slurry is 8.8, and the temperature is 45 °C. The titanium source is anatase TiO2 with a D50 of 50-200 nm. The carbon source is glucose. The graphite is artificial graphite with a D50 of 5-20 μm. The dispersant is PEG.

[0032] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 240℃, the outlet temperature of the spray drying is 120℃, the rotation speed of the atomizing disc is 18000rpm, and the feed rate is 7mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite anode material. The inert atmosphere is helium.

[0033] Comparative Example 3 (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to the solvent. The mass of the niobium source and fluorine source accounts for 0.04% of the mass of the solute, the mass of the titanium source and lithium source accounts for 3% of the mass of the solute, the mass of the carbon source accounts for 4% of the mass of the solute, the mass of the graphite accounts for 92% of the mass of the solute, and the mass of the dispersant accounts for 0.96% of the mass of the solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 30 wt%, the pH of the slurry is 8.8, and the temperature is 45 °C. The titanium source is anatase TiO2 with a D50 of 50-200 nm. The lithium source is LiOH•H2O with a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:5, the niobium source is Nb(HC2O4)5, the fluorine source is LiF, and Nb 5+ and F - The mass ratio is 1:1.3, the carbon source is glucose, the graphite is artificial graphite with D50=5-20μm, and the dispersant is PEG.

[0034] (2) The slurry obtained in step (1) is spray-dried. The inlet temperature of the spray drying is 240℃, the outlet temperature of the spray drying is 120℃, the rotation speed of the atomizing disc is 18000rpm, and the feed rate is 7mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 8 hours. Then, it is naturally cooled to room temperature to obtain the composite anode material. The inert atmosphere is helium.

[0035] Comparative Example 4 It is a pure LTO anode material.

[0036] Comparative Example 5 It is a pure graphite anode material.

[0037] The performance of the anode materials prepared in the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0038]

[0039] Table 1 A detailed analysis of the above data shows that the composite anode materials prepared in Examples 1-6 possess excellent electrochemical performance, low volume expansion, and are less prone to lithium plating. Comparative Example 1 uses pure LTO and carbon to coat graphite, while Comparative Example 2 uses titanium dioxide and carbon to coat graphite. Both of these methods exhibit performance inferior to Examples 1-6 in all aspects. Comparative Example 3 directly raises the temperature to 780°C during calcination, making it impossible to prevent vaporization and pore formation during the calcination process. Furthermore, it is difficult to suppress the formation of impurity phases during element doping, resulting in a decrease in capacity, a significant reduction in initial efficiency, a larger volume expansion during charge-discharge cycles, and consequently, a deterioration in cycle performance. Comparative Example 4 is a pure graphite electrode with high capacity, but it also suffers from the most severe 3C lithium plating. During charge-discharge cycles, its volume expansion is the largest, resulting in the worst cycle performance and making it difficult to use alone in fast-charging and long-cycle scenarios. Comparative Example 5 is a pure TLO anode with the lowest volume expansion rate, and its cycle performance and first-cycle efficiency are the best. However, its reversible capacity is very low and its energy density is extremely poor, which limits its widespread application. It can be seen that by carbon coating and LTO doping of graphite, and then supplementing it with element doping, not only can the advantages of both be obtained, but the original performance can also be improved, achieving significant progress and unexpected results.

[0040] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite negative electrode material, characterized in that: It includes the following steps: (1) Add niobium source, fluorine source, titanium source, lithium source, carbon source, graphite and dispersant to solvent, wherein the mass of niobium source and fluorine source accounts for 0.03%-0.07% of the mass of solute, the mass of titanium source and lithium source accounts for 2%-4% of the mass of solute, the mass of carbon source accounts for 3%-5% of the mass of solute, the mass of graphite accounts for 90%-94% of the mass of solute, and the mass of dispersant accounts for 0.5%-1.5% of the mass of solute. Stir until the solute is completely dissolved to obtain a slurry. The solid content of the slurry is 28%-32wt%, the pH of the slurry is 8.5-9.0, and the temperature is 40-50℃. (2) Spray dry the slurry obtained in step (1). The inlet temperature of the spray dryer is 230-250℃, the outlet temperature of the spray dryer is 95-150℃, the rotation speed of the atomizing disc is 18000-22000rpm, and the feed rate is 6-8mL / min to obtain the doped and coated precursor. (3) The doped and coated precursor obtained in step (2) is placed in an inert atmosphere for calcination. First, the temperature is raised to 200°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. Next, the temperature is raised to 780°C at a heating rate of 5°C / min and held for 5 hours. Then, the temperature is naturally cooled to room temperature to obtain the composite anode material.

2. The method for preparing the composite negative electrode material according to claim 1, characterized in that: The niobium source is Nb(HC₂O₄)₅ or NbCl₅, and the fluorine source is NH₄F or LiF, and Nb 5+ and F - The mass ratio is 1:1.

3.

3. The method for preparing the composite negative electrode material according to claim 1, characterized in that: The titanium source is anatase TiO2 or Ti(OC4H9)4, with a D50 of 50-200 nm. The lithium source is LiOH•H2O or Li2CO3, with a D50 of 1-5 μm. + and Ti 4+ The mass ratio is 4:

5.

4. The method for preparing the composite negative electrode material according to claim 1, characterized in that: The carbon source is glucose or pitch.

5. The method for preparing the composite negative electrode material according to claim 1, characterized in that: The graphite is either artificial or natural graphite, with a D50 of 5-20 μm.

6. The method for preparing the composite negative electrode material according to claim 1, characterized in that: The dispersant is PEG.

7. The method for preparing the composite negative electrode material according to claim 1, characterized in that: The inert atmosphere is one of helium, argon, or nitrogen.

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