Low-temperature fast-charge composite negative electrode material, preparation method thereof and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a low-temperature fast-charge composite negative electrode material, a preparation method thereof and a lithium ion battery. The method comprises the following steps: loading titanium dioxide on the surfaces of graphite particles, and then carrying out pretreatment by adopting an anionic surfactant; and constructing a nitrogen-containing organic metal framework compound containing cobalt on the surface of the pretreated composite material, and then performing pyrolysis treatment to obtain the composite negative electrode material. The preparation method comprises the following steps: coating the outside of titanium dioxide / graphite with a ZIF derivative to form Namp; due to the Co-doped porous carbon layer, the conductivity is improved, the electrolyte can be effectively dredged, the transportation process of Li < + > can be enhanced, and meanwhile, Namp is added; co doping can reduce a TiO2 energy band and a lithium intercalation energy barrier, and obviously improve the electron and ion conductivity, so that the conductivity of the material is improved, and the lithium intercalation energy barrier can be effectively reduced. The preparation method is reasonable in design, simple and easy to operate.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a low-temperature fast-charging composite anode material, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] Due to significant advantages such as high energy density and long cycle life, lithium-ion batteries have been increasingly widely used in daily production and life. Conventional lithium-ion batteries have slow kinetics of the graphite anode, resulting in severe performance degradation in low-temperature environments, especially low-temperature charging performance. The vast majority of lithium-ion batteries cannot be charged at -20°C. Forced charging will lead to severe lithium plating on the anode, increasing the risk of thermal runaway. Therefore, improving the charge transfer ability of the anode material and reducing the charge transfer impedance are the keys to optimizing fast-charging performance and low-temperature performance.

[0003] Currently, the basic problem faced by graphite anode materials in low-temperature charging is that at low temperatures, the diffusion rate of Li + becomes slower, and the charge transfer rate also decreases, resulting in severe low-temperature performance degradation. In particular, during low-temperature charging, due to the slower movement rate of Li + and the blocked charge transfer, a large amount of Li + will directly deposit on the surface of the graphite anode to form dendritic lithium metal crystals, causing the lithium-ion battery to malfunction and even posing serious safety risks. To solve a series of problems of lithium-ion batteries operating at low temperatures, Chinese Patent CN114335462B discloses a graphite anode material for low temperatures. It uses a metal-organic framework material to coat the graphite material, and then forms metal single nanoparticles, such as cobalt nanoparticles and a porous structure, on the graphite surface through heat treatment. On the one hand, the cobalt metal nanoparticles enhance the electronic conductivity of the graphite anode material. On the other hand, the coordination structure of its surface with N elements and the existing forms such as surface oxides have a strong adsorption effect on Li+. The combination of the two together improves the kinetics of the Li+ charge transfer step. Therefore, to a certain extent, the charge transfer ability of the graphite anode material can be improved. However, due to the agglomeration of cobalt metal nanoparticles during the heat treatment process, the size of the cobalt metal nanoparticles is relatively large, seriously affecting the charge transfer ability of the graphite anode material, and its low-temperature charging problem has not been effectively improved.

[0004] Therefore, in order to broaden the application of lithium-ion batteries in alpine regions, further research is needed to improve the charge transport performance of graphite anode materials. Summary of the Invention

[0005] Based on this, the present invention provides a low-temperature fast-charging composite anode material, aiming to effectively improve the charge transport performance of the graphite anode material, so as to broaden the application of lithium-ion batteries in alpine regions. The present invention uses small-sized graphite anodes as the core, and coats titanium dioxide on its surface to form a titanium dioxide / graphite structure. Among them, the lithium intercalation potential of titanium dioxide is high, and it can preferentially intercalate lithium before graphite, thus effectively preventing lithium precipitation. However, its poor ionic and electronic conductivity limits the intercalation and deintercalation reactions of lithium ions, resulting in poor rate performance. Coat ZIF-67 and its derivatives on the outside of titanium dioxide / graphite to form a porous carbon layer doped with N and Co. The porous carbon layer that catalyzes graphitization improves the conductivity of titanium dioxide, and its porous characteristics can effectively conduct the electrolyte and strengthen the transport process of Li + . Further, during the carbonization process, Co elements are doped into titanium dioxide, which can reduce the energy band of TiO2 and improve conductivity; N doping of titanium dioxide is beneficial to the aggregation of electrons near N, which helps to provide more carriers to participate in the electrochemical reaction and can reduce the lithium intercalation energy barrier. Therefore, the fast-charging ability of the graphite anode at low temperatures is greatly improved.

[0006] To achieve the above object, in the first aspect, the present invention provides a preparation method of a low-temperature fast-charging composite anode material, which includes the following steps:

[0007] S1. Load titanium dioxide on the surface of graphite particles to obtain a titanium dioxide / graphite composite material;

[0008] S2. Pretreat the titanium dioxide / graphite composite material with an anionic surfactant;

[0009] S3. Construct a nitrogen-containing organometallic framework compound containing cobalt on the surface of the pretreated titanium dioxide / graphite composite material to obtain a titanium dioxide / graphite composite material coated with a nitrogen-containing organometallic framework compound containing cobalt;

[0010] S4. Pyrolyze the titanium dioxide / graphite composite material coated with a nitrogen-containing organometallic framework compound containing cobalt to obtain a low-temperature fast-charging composite anode material.

[0011] As a further preferred technical solution of the present invention, the D50 of the graphite particles is 4-15 μm, such as 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc., and the optimal size is 7 μm. Selecting small-sized graphite can shorten the Li + diffusion path and enhance the Li+ transport kinetics; and / or, the loading rate of titanium dioxide on the surface of the graphite particles is 0.5-20 wt%, such as 0.5 wt%, 1.0 wt%, 2.0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, etc., and the optimal loading amount is 10 wt%. The high lithium intercalation potential of its titanium dioxide can prevent lithium precipitation at low temperatures.

[0012] As a further preferred technical solution of the present invention, step S1 loads titanium dioxide on the surface of graphite particles in the following manner:

[0013] S1-1. Pretreatment of graphite particles: Boil the graphite particles in nitric acid (preferably with a concentration of 5-6 mol / L), then wash, filter and dry.

[0014] S1-2. Preparation of sol: Take 5 ml of tetrabutyl titanate and slowly add it into a conical flask containing 10 ml of absolute ethanol, and stir on a magnetic stirrer for 30-50 min to obtain a pale yellow clear intermediate A; Take 1 ml of glacial acetic acid and add it into a conical flask containing 2.5 ml of absolute ethanol and 1 ml of deionized water, and adjust the pH < 3 with concentrated hydrochloric acid (about 1-3 drops) to prepare intermediate B; In a water bath at 80-100 °C, continuously stir intermediate B, and drop intermediate A into intermediate B at a rate of 5 ml / min by vigorous stirring, and add the pretreated graphite particles. Under stirring, gradually form a gel-like intermediate C; Preferably, adjust the pH to be greater than 1.5 and less than 3 with concentrated hydrochloric acid.

[0015] S1-3. Heat treatment: First, dry and grind intermediate C in an oven at 60-80 °C, and then calcine it at 450-600 °C under a nitrogen atmosphere to obtain a titanium dioxide / graphite composite material.

[0016] As a further preferred technical solution of the present invention, the steps of constructing a cobalt-containing nitrogenous metal-organic framework compound on the surface of the pretreated titanium dioxide / graphite composite material in step S3 include:

[0017] S3-1. Add the pretreated titanium dioxide / graphite composite material into a methanol solution, stir and disperse to obtain a methanol dispersion of the titanium dioxide / graphite composite material.

[0018] S3-2. Dissolve zinc nitrate and cobalt nitrate in a methanol solution to obtain a mixed solution of zinc nitrate and cobalt nitrate; Dissolve 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution. Preferably, the molar ratio of zinc nitrate to cobalt nitrate: 2-methylimidazole is 1:16; The molar ratio of Zn / Co in zinc nitrate and cobalt nitrate is 1 / 2.

[0019] S3-3. Under stirring, slowly pour the mixed solution of zinc nitrate and cobalt nitrate into the methanol dispersion of the titanium dioxide / graphite composite material; Then dropwise add the 2-methylimidazole methanol solution, continue to stir for a period of time, filter by suction, and wash with methanol 1-3 times. After drying, ZIF is coated on the surface of the titanium dioxide / graphite composite material to obtain a titanium dioxide / graphite composite material coated with a cobalt-containing nitrogenous metal-organic framework compound, that is, a titanium dioxide / graphite@ZIF composite material.

[0020] In step S4, under the protection of a nitrogen or argon atmosphere, the titanium dioxide / graphite@ZIF composite material is pyrolyzed at 900-1000 °C and finally ground to obtain a graphite anode material for low-temperature fast charging.

[0021] As a further preferred technical solution of the present invention, the anionic surfactant is one or more of sodium polystyrene sulfonate, sodium dodecyl sulfonate, and sodium dodecyl benzene sulfonate. Among them, sodium polystyrene sulfonate (PSS) is the most preferred. Using PSS as an anionic surfactant to activate graphite particles makes the graphite surface negatively charged. During the process of constructing a cobalt-containing nitrogen-containing organometallic framework compound, it helps Co 2+ to be evenly adsorbed on the surface of graphite particles. After adding 2-methylimidazole, it can be anchored on the surface of titanium dioxide / graphite particles to uniformly form a precursor of a coating layer such as ZIF-67 derivative.

[0022] Furthermore, the mass ratio of sodium polystyrene sulfonate (PSS) to the titanium dioxide / graphite composite material is 1:0.5-1:2. Among them, if the amount of PSS used is too small, the activation of the graphite particle surface is incomplete, resulting in Co 2+ not being completely adsorbed on the graphite surface, and ZIF-67 or its derivatives will be formed in the solution; if the amount of PSS used is too large, the material waste will be relatively serious.

[0023] Furthermore, in step S4, the proportional relationship between the cobalt metal ion and the graphite dosage is: 1 g of titanium dioxide / graphite composite material is formulated with 0.25-1 mmol of cobalt metal ions, and the molar ratio of cobalt metal ions to 2-methylimidazole is 1:4-1:32. Among them, this dosage and ratio can control the thickness of the coating layer, thereby ensuring that the initial efficiency of the composite anode sample is maintained between 87-92%. It is preferred that the coating layer thickness is controlled within 50-500 nm. If the coating layer thickness is too small, the porous characteristics cannot be achieved, and it is difficult to form a graphitized carbon layer coating for the Co metal nanoparticles formed by pyrolysis, and there is a risk of dissolution in the electrolyte; if the coating layer thickness is too large, the specific surface area is too large, resulting in a serious reduction in the initial efficiency.

[0024] In the present invention, both the titanium dioxide and the ZIF pyrolysis material are nanoscale.

[0025] According to the second aspect of the present invention, the present invention also provides a low-temperature fast-charging composite anode material, which is prepared by the method of the first aspect and has a porous structure on its surface.

[0026] According to the third aspect of the present invention, the present invention also provides a lithium-ion battery, which includes the low-temperature fast-charging composite anode material of the second aspect. Specifically, the low-temperature fast-charging composite anode material is used as the active material, and the active material, a conductive agent (such as acetylene black), and a binder (such as polyvinylidene fluoride) are mixed in a certain proportion in N-methylpyrrolidone to prepare a slurry, and then coated on a metal foil to obtain the anode electrode sheet for the lithium-ion battery.

[0027] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0028] 1) The present invention uses a small-particle-size graphite anode as the core, and titanium dioxide is coated on its surface to form a titanium dioxide / graphite structure. Anatase titanium dioxide has a relatively high lithium insertion / extraction potential (1.3 - 1.8V vs. Li + / Li), which can insert lithium prior to graphite and limit the growth of a large number of lithium dendrites on the electrode surface. During the process of lithium ion insertion / extraction, due to the extremely small volume expansion rate of titanium dioxide, the titanium dioxide electrode also has excellent cycle performance. However, the poor ion and electron conductivity limits the lithium ion insertion and extraction reactions and its rate performance; a ZIF derivative is coated outside the titanium dioxide / graphite to form a nitrogen and cobalt doped porous carbon layer, which not only improves the conductivity but also effectively channels the electrolyte and strengthens the Li + transport process. At the same time, nitrogen and cobalt doping can reduce the energy band of TiO2 and the lithium insertion energy barrier, significantly improving the electron and ion conductivity.

[0029] 2) The present invention uses a nitrogen-containing organometallic framework compound containing cobalt (such as ZIF-67) as the precursor of the coating layer. After heat treatment, a porous carbon coating layer can be formed. Its porous characteristics can significantly improve the electrolyte infiltration and liquid retention performance, facilitating the Li + transport process and effectively improving the low-temperature charging performance. The Co metal nanoparticles wrapped by the graphitized carbon layer formed during pyrolysis significantly improve the conductivity, thus contributing to accelerating the charge transfer process under low-temperature conditions.

[0030] 3) The present invention uses a nitrogen-containing organometallic framework compound containing cobalt (such as ZIF-67) as the precursor of the coating layer. After heat treatment, Co and N elements can effectively dope TiO2 during the pyrolysis process, reducing the energy band of TiO2 and the lithium insertion energy barrier, and significantly improving the electron and ion conductivity.

[0031] 4) The present invention selects small-particle-size graphite as the core, and the small-particle-size graphite significantly shortens the Li + diffusion path and improves the low-temperature charging performance to a certain extent. Description of the Drawings

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 This is the 0-degree 0.1C lithium intercalation curve (1C = 372 mAh / g) of the batteries of Example 1 of the present invention and Comparative Examples 1 to 4.

[0034] Figure 2 This is the 0-degree 0.1C lithium intercalation potential (1C = 372 mAh / g) of the batteries of Example 1 of the present invention and Comparative Examples 1 to 4.

[0035] Figure 3 This is the -25-degree 0.5C charging curve (1C = 372 mAh / g) of the batteries of Example 1 of the present invention and Comparative Examples 1 to 4.

[0036] The realization of the object, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific Embodiments

[0037] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0038] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0039] Example 1 (TiO2 + graphite + ZIFs coating treatment):

[0040] S1. Load TiO2 on the surface of the graphite material to obtain a titanium dioxide / graphite composite material, specifically:

[0041] Acidify the graphite: Boil 5 g of graphite particles with a D50 of 7 μm in 6 mol / L nitric acid at 100 °C for 1 h, then wash with deionized water, filter and dry to obtain the treated graphite.

[0042] Preparation of the sol: Take 5 ml of tetrabutyl titanate and slowly add it to a conical flask containing 10 ml of absolute ethanol, stir on a magnetic stirrer for 50 min to obtain a pale yellow clear intermediate A; take 1 ml of glacial acetic acid and add it to a conical flask containing 2.5 ml of absolute ethanol and 1 ml of deionized water, and adjust the pH value with concentrated hydrochloric acid (about 1 - 3 drops) to make the pH = 2 to obtain intermediate B; in a 90 °C water bath, continuously stir intermediate B, and drop intermediate A into intermediate B at a rate of 5 ml / min under vigorous stirring, and add the treated graphite, and stir to gradually form a gel-like intermediate C;

[0043] Heat treatment: The intermediate C was dried in an oven at 80 °C for 2 h, ground, and then calcined at 500 °C for 4 h under nitrogen protection to obtain a titanium dioxide / graphite composite with a titanium dioxide loading of 10 wt%.

[0044] S2: Weigh 5 g of sodium polystyrene sulfonate (PSS) and 18 g of sodium chloride (NaCl) and dissolve them in 300 mL of deionized water to obtain an aqueous solution of sodium polystyrene sulfonate. Add the titanium dioxide / graphite composite obtained in S1 to the aqueous solution of sodium polystyrene sulfonate, stir for 8 h to obtain a dispersion of the titanium dioxide / graphite composite. After suction filtration, add it to 300 mL of methanol solution and stir to disperse, obtaining a methanol dispersion of the titanium dioxide / graphite composite.

[0045] S3: Weigh 2.5 mmol of zinc nitrate and cobalt nitrate (Zn / Co = 1 / 2) and dissolve them in 100 mL of methanol solution to obtain a mixed solution of zinc nitrate and cobalt nitrate. According to the molar ratio of zinc nitrate and cobalt nitrate to 2-methylimidazole of 1:16, weigh 2-methylimidazole and dissolve it in methanol to obtain a 2-methylimidazole methanol solution.

[0046] S4: Slowly pour the mixed solution of zinc nitrate and cobalt nitrate into the methanol dispersion of the titanium dioxide / graphite composite obtained above, and continue to stir for 12 h. Then, dropwise add the 2-methylimidazole methanol solution and continue to stir for 24 h. After suction filtration and washing with methanol 3 times, and drying, a ZIF-67 derivative is coated on the surface of the titanium dioxide / graphite composite.

[0047] S5: Pyrolyze the product of S4 in an argon atmosphere at a pyrolysis temperature of 950 °C, a heating rate of 10 °C / min, and a holding time of 3 h. Finally, grind it to obtain a low-temperature fast-charging composite anode material, denoted as titanium dioxide / graphite@ZIF-67 composite anode material.

[0048] The electrochemical performance of the low-temperature fast-charging composite anode material of Example 1 was tested for application in a lithium-ion half-cell, as follows:

[0049] A slurry was prepared by mixing the active material (titanium dioxide / graphite@ZIF-67 composite anode material), conductive agent (acetylene black), and binder (polyvinylidene fluoride) in a mass ratio of 8:1:1 in N-methylpyrrolidone, and then coated on a copper foil to obtain the anode electrode sheet. A lithium sheet was used as the cathode, 50 μL of electrolyte (1.0 M LiPF6 dissolved in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) / ethyl acetate (EA) / ethyl propionate (EP) (20 / 20 / 30 / 5 / 25, volume ratio) + 0.8 wt% vinylene carbonate (VC) + 1 wt% fluoroethylene carbonate (FEC)) was added, and Celgard 2500 was used as the separator to assemble a 2032-type coin cell. The test conditions were constant current charge and discharge, and the voltage range was 0.01 V to 2 V.

[0050] Comparative Example 1 (TiO2 + graphite):

[0051] The titanium dioxide / graphite composite material was prepared by using the S1 step of Example 1, and then the lithium-ion half-cell was assembled and electrochemically tested by the same method and conditions as above.

[0052] Comparative Example 2 (ZIFs + graphite):

[0053] It was obtained by directly loading ZIFs on the graphite material and then pyrolysis treatment. The difference between its preparation method and that of Example 1 is that: compared with Example 1, the S1 step was omitted, and the S2 - S5 steps of Example 1 were used to prepare the ZIF-coated graphite composite anode material, and then the lithium-ion half-cell was assembled and electrochemically tested by the same method and conditions as above.

[0054] Comparative Example 3 (TiO2 + graphite + C coating treatment):

[0055] First, the titanium dioxide / graphite composite material was prepared, and then carbon was coated. Compared with Example 1, the titanium dioxide / graphite composite material was prepared by using the S1 step of Example 1, then glucose was dissolved in deionized water to form a 25 wt% glucose aqueous solution, the titanium dioxide / graphite composite material was added to the glucose aqueous solution, and a uniform graphite suspension was formed by ultrasonic treatment. Stirring was continued for 12 h, filtration was carried out, and it was washed 3 times with deionized water. After drying, glucose was coated on the surface of the titanium dioxide / graphite composite material. Finally, the pyrolysis treatment was carried out by repeating the S5 step of Example 1 to obtain the composite anode material with TiO2 + graphite + C coating treatment, and then the lithium-ion half-cell was assembled and electrochemically tested by the same method and conditions as above.

[0056] Comparative Example 4 (raw graphite):

[0057] Using the raw graphite without treatment in Example 1 as the active material, a lithium-ion half-cell was assembled by the same method and conditions as above, and its electrochemical performance was tested.

[0058] The half-cells assembled in the above examples and comparative examples were cycled at a current density of 0.1C for 3 cycles at room temperature to form a stable solid electrolyte interface layer (SEI), and then the pre-cycled cells were placed at 0°C and discharged to 0.1V at 0.1C to test their low-temperature lithium intercalation capacity. The results are as Figure 1 、 Figure 2 shown in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] It can be seen from the half-cell test results in Table 1 that the battery assembled with the negative electrode material treated by TiO2+graphite+ZIFs coating of the present invention has excellent low-temperature lithium intercalation ability, has the highest lithium intercalation capacity (330 mAh / g) at 0°C, and shows a higher lithium intercalation potential ( Figure 2 ), and is significantly better than each comparative example, which indicates that it can effectively prevent the generation of lithium dendrites at low temperatures. Further, the assembled battery was charged at a lower temperature (-25°C) at a larger current density (0.5C), and the results are as Figure 3 shown in Table 2. It can be seen that the battery assembled with the negative electrode material treated by TiO2+graphite+ZIFs coating of the present invention has a larger capacity and is significantly better than other comparative examples, indicating its ability to charge quickly at low temperatures.

[0063] Table 2

[0064]

[0065] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The protection scope of the present invention is only defined by the appended claims.

Claims

1. A preparation method of a low-temperature fast-charging composite anode material, characterized in that, It includes the following steps: S1. Load titanium dioxide on the surface of graphite particles to obtain a titanium dioxide / graphite composite material; S2. Pretreat the titanium dioxide / graphite composite material with an anionic surfactant; S3. Construct a cobalt-containing nitrogenous metal-organic framework compound on the surface of the pretreated titanium dioxide / graphite composite material to obtain a titanium dioxide / graphite composite material coated with a cobalt-containing nitrogenous metal-organic framework compound; S4. Perform pyrolysis treatment on the titanium dioxide / graphite composite material coated with a cobalt-containing nitrogenous metal-organic framework compound to obtain a low-temperature fast-charging composite anode material.

2. The preparation method of the low-temperature fast-charging composite negative electrode material according to claim 1, characterized in that, The D50 of the graphite particles is 4-15 μm; and / or the loading rate of titanium dioxide on the surface of the graphite particles is 0.5-20 wt%.

3. The preparation method of the low-temperature fast-charging composite anode material according to claim 2, characterized in that, Step S1 loads titanium dioxide on the surface of graphite particles in the following manner: S1-1. Pretreatment of graphite particles: Boil the graphite particles in nitric acid, then wash, filter, and dry; S1-2. Preparation of sol: Mix tetrabutyl titanate and absolute ethanol to prepare intermediate A; mix glacial acetic acid, absolute ethanol, and deionized water, and adjust the pH < 3 to prepare intermediate B; in a water bath at 80-100 °C, mix intermediate A and intermediate B by stirring, and add the pretreated graphite particles, and gradually form a gel-like intermediate C under stirring; S1-3. Heat treatment: First dry and grind intermediate C, and then calcine it at 450-600 °C in a nitrogen atmosphere to obtain the titanium dioxide / graphite composite material.

4. The preparation method of the low-temperature fast-charging composite anode material according to claim 1, characterized in that, The steps for pretreating the titanium dioxide / graphite composite material in step S2 include: S2-1. Dissolve an anionic surfactant and sodium chloride in deionized water to obtain a saline solution of the anionic surfactant; S2-2. Add the titanium dioxide / graphite composite material to the saline solution of the anionic surfactant, stir to obtain a dispersion of the titanium dioxide / graphite composite material, and finally filter by suction.

5. The preparation method of the low-temperature fast-charging composite negative electrode material according to claim 1, wherein The anionic surfactant is one or more of sodium polystyrene sulfonate, sodium dodecyl sulfonate, and sodium dodecyl benzene sulfonate.

6. The preparation method of the low-temperature fast-charging composite negative electrode material according to claim 1, wherein, The temperature of the pyrolysis treatment is 900-1000 °C.

7. The preparation method of the low-temperature fast-charging composite anode material according to claim 6, characterized in that, The steps for constructing a cobalt-containing nitrogenous metal-organic framework compound on the surface of the pretreated titanium dioxide / graphite composite material in step S3 include: S3-1. Add the pretreated titanium dioxide / graphite composite material to a methanol solution, stir and disperse to obtain a methanol dispersion of the titanium dioxide / graphite composite material; S3-2. Dissolve zinc nitrate and cobalt nitrate in a methanol solution to obtain a mixed solution of zinc nitrate and cobalt nitrate; dissolve 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution. S3-3. Under stirring, slowly pour the mixed solution of zinc nitrate and cobalt nitrate into the methanol dispersion of the titanium dioxide / graphite composite material; then gradually add the 2-methylimidazole methanol solution dropwise, continue stirring for a period of time, filter by suction, and wash with methanol 1-3 times. After drying, ZIF is coated on the surface of the titanium dioxide / graphite composite material to obtain a titanium dioxide / graphite composite material coated with a cobalt-containing nitrogenous metal-organic framework compound.

8. The preparation method of the low-temperature fast-charging composite negative electrode material according to claim 1, wherein, The cobalt-containing nitrogenous metal-organic framework compound is ZIF-67 or its derivative.

9. A low-temperature fast-charging composite anode material, characterized in that, It is prepared by the method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, It includes the low-temperature fast-charging composite anode material according to claim 9.

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