An expanded microcrystalline graphite / Fe2O3 / SnO2 lithium ion battery micro-nano negative electrode material and a preparation method and application thereof

Abstract

The application discloses an expanded microcrystalline graphite / Fe2O3 / SnO2 lithium ion battery micro-nano negative electrode material and a preparation method and application thereof, and relates to the field of new material preparation and new energy technology.The application comprises the following steps: taking high-purity microcrystalline graphite as raw material, preparing expanded microcrystalline graphite by adopting an oxidation method and an inert atmosphere heat treatment method, preparing expanded microcrystalline graphite / Fe2O3 composite material by adopting a water bath method and an air atmosphere heat treatment method I, and then preparing expanded microcrystalline graphite / Fe2O3 / SnO2 composite material by adopting a hydrothermal method and an air atmosphere heat treatment method II, which is used for a lithium ion battery negative electrode.The ternary composite material has a first discharge specific capacity of 1539.9 mAh / g at a current density of 0.1 A / g, a first coulombic efficiency of 70.1%, and a discharge specific capacity of 1003.2 mAh / g after 100 cycles.The high-purity microcrystalline graphite has a remarkable expansion effect, the selection and addition of the nano metal oxide significantly improve the lithium storage capacity and cycle stability of the lithium ion battery negative electrode material, and a new idea and method are provided for developing a high-performance lithium ion battery negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new material preparation and new energy technology, and particularly relates to an expanded microcrystalline graphite / Fe2O3 / SnO2 lithium ion battery micro-nano negative electrode material, a preparation method thereof and application thereof in a lithium ion battery. BACKGROUND

[0002] Microcrystalline graphite has rich reserves, structural characteristics such as small size and isotropy, and a higher theoretical lithium storage capacity than commercialized flake graphite when applied in a lithium ion battery negative electrode material. However, compared with Si / C negative electrode materials, the lithium storage capacity of microcrystalline graphite is low, and the first coulombic efficiency is not high due to the formation of SEI film. Therefore, it is an urgent problem to be solved to try to improve the lithium storage performance of microcrystalline graphite by using various modification methods.

[0003] It is an effective method to increase the pore structure and lithium storage space of microcrystalline graphite by oxidation treatment. However, it is difficult to expand the overall volume of microcrystalline graphite because of the small size of microcrystalline graphite, the volume micro-expansion of defects and etching generated at the boundary. Metal oxide composite is also an effective means to improve the lithium storage capacity, but the volume expansion effect cannot be ignored, so it is particularly important to select a suitable metal oxide. SUMMARY

[0004] In order to improve the lithium storage performance of the microcrystalline graphite lithium ion battery negative electrode material, the application aims to provide an expanded microcrystalline graphite / Fe2O3 / SnO2 lithium ion battery micro-nano negative electrode material, a preparation method thereof and application thereof. The high-purity microcrystalline graphite is expanded, and then compounded with Fe2O3 and SnO2 nano materials. The combination of the two can fully exert the synergistic effect of nano-sized particles and micron-sized microcrystalline graphite, and effectively inhibit the volume expansion of metal oxides.

[0005] In order to further achieve the above-mentioned purpose, the application adopts the following technical scheme: a preparation method of an expanded microcrystalline graphite / Fe2O3 / SnO2 lithium ion battery micro-nano negative electrode material, comprising the following steps:

[0006] First, high-purity microcrystalline graphite is used as raw material to prepare expanded microcrystalline graphite by using an oxidation method and an inert atmosphere heat treatment method;

[0007] Second, the expanded microcrystalline graphite / Fe2O3 composite material is prepared by using a water bath method and an air atmosphere heat treatment method I;

[0008] Finally, the expanded microcrystalline graphite / Fe2O3 / SnO2 composite material is prepared by using a hydrothermal method and an air atmosphere heat treatment method II.

[0009] Optionally, the expanded microcrystalline graphite is prepared by using the high-purity microcrystalline graphite as raw material, an oxidation method and an inert atmosphere heat treatment method, and includes the following steps:

[0010] Step (1): under the condition of ice water bath, 1-10 g of high-purity microcrystalline graphite is added into a beaker containing 50-100 mL of concentrated sulfuric acid, and then 50-100 mL of potassium permanganate is added, and stirring is performed for 30-60 min;

[0011] Step (2): after stirring in a 20-50 ℃ water bath for 10-40 min, deionized water is added for dilution, and when the temperature no longer rises, an appropriate amount of hydrogen peroxide is added until no bubbles are generated;

[0012] Step (3): after standing for a period of time, high-speed centrifugation is performed, and the product is washed with deionized water until neutral;

[0013] Step (4): the obtained product is dried in a 30-80 ℃ air drying oven;

[0014] Step (5): the product is heated at 600-900 ℃ for 5-20 min in an inert atmosphere to prepare expanded microcrystalline graphite.

[0015] As shown above, the expanded microcrystalline graphite has a significant expansion effect on the surface and boundary thereof.

[0016] Optionally, the expanded microcrystalline graphite / Fe2O3 composite material is prepared by using a water bath method and an air atmosphere heat treatment method I, and includes the following steps:

[0017] Step (1): 0.1-0.5 g of expanded microcrystalline graphite and 0.01-0.5 g of FeCl3·6H2O are weighed into a beaker, and ultrasonic treatment is performed for 20-50 min;

[0018] Step (2): stirring is performed in a 60-90 ℃ water bath for 3-6 h, and after standing for a period of time, suction filtration is performed;

[0019] Step (3): the obtained product is placed in a 40-80 ℃ air drying oven for 3-8 h;

[0020] Step (4): the product is heated at 200-800 ℃ for 1-2 h in air to prepare an expanded microcrystalline graphite / Fe2O3 composite material with different mass fractions of Fe2O3.

[0021] As shown above, the Fe2O3 nanoparticles are distributed in the pore structure on the surface and edge of the expanded microcrystalline graphite.

[0022] Optionally, the expanded microcrystalline graphite / Fe2O3 / SnO2 composite material is prepared by using a hydrothermal method and an air atmosphere heat treatment method II, and includes the following steps:

[0023] Step (1): 0.1-1g SnCl2·2H2O was weighed and dissolved in 10-20mL concentrated sulfuric acid, and magnetic stirring was performed until complete dissolution;

[0024] Step (2): 0.01-0.5g L-ascorbic acid was weighed and dissolved in 10-20mL deionized water;

[0025] Step (3): The SnCl2 solution was added dropwise to the aqueous solution of L-ascorbic acid, and magnetic stirring was performed for 10-30min, and then 0.1-0.5g expanded microcrystalline graphite / Fe2O3 composite material was added, and stirring was performed for 10-40min;

[0026] Step (4): The reaction kettle was reacted at 100-200℃ for 1-3h, the black precipitate was extracted by a centrifuge, and washed with deionized water until neutral, and dried in a blast drying oven at 50-80℃ for 1-3h;

[0027] Step (5): The obtained material was heat treated in air at 300-700℃ for 1-2h, to prepare expanded microcrystalline graphite / Fe2O3 / SnO2 composite material with different contents.

[0028] From the above, the Fe2O3 and SnO2 nanoparticles are distributed on the surface and interlayer of the expanded microcrystalline graphite, forming a micro-nano composite structure.

[0029] An expanded microcrystalline graphite / Fe2O3 / SnO2 composite material prepared by the preparation method.

[0030] An application of the aforementioned expanded microcrystalline graphite / Fe2O3 / SnO2 composite material in a lithium ion battery negative electrode.

[0031] Compared with the prior art, the technical advantages of the present application are:

[0032] (1) Due to the small size of the microcrystalline graphite, only a small volume expansion can be achieved by oxidation treatment. In the present application, high-purity microcrystalline graphite is used as raw material, and an oxidation method and an inert atmosphere heat treatment method are used to prepare expanded microcrystalline graphite, which has a significant volume expansion and an increased pore structure, which is beneficial to increasing the lithium storage vacancies and improving the lithium storage capacity.

[0033] (2) Adding metal oxides to the lithium ion battery negative electrode material is a method to improve the lithium storage capacity, but the metal oxides are prone to volume expansion during the delithiation / lithiation process, which reduces the cycle stability of the composite material. In the present application, a water bath method and an air atmosphere heat treatment method are used to prepare a composite material with a micro-nano structure. Due to the porous structure of the expanded microcrystalline graphite, it is beneficial to embed the nano metal oxide particles therein, which provides a buffer space for the volume expansion of Fe2O3 and SnO2, fully utilizes the synergistic effect of the micro-nano structure, and improves the electrochemical stability of the composite material.

[0034] (3) The raw materials used in this invention are inexpensive and the synthesis process is simple. It significantly improves the electrochemical performance of lithium-ion battery anode materials, expands the application range of abundant mineral resources (microcrystalline graphite), and enhances the commercial value of microcrystalline graphite. Attached Figure Description

[0035] Figure 1 This is a microstructure morphology diagram of the expanded microcrystalline graphite prepared in Example 1 of this invention.

[0036] Figure 2 This is a microstructure diagram of the expanded microcrystalline graphite / Fe2O3 / SnO2 composite material prepared in Example 1 of this invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] A method for preparing expanded microcrystalline graphite / Fe2O3 / SnO2 lithium-ion battery micro / nano anode material includes the following steps:

[0039] (1) Under ice-water bath conditions, add 1-10g of high-purity microcrystalline graphite to a beaker containing 50-100mL of concentrated sulfuric acid, then add 50-100mL of potassium permanganate and stir for 30-60min.

[0040] (2) After stirring in a water bath at 20-50℃ for 10-40 minutes, add deionized water to dilute. When the temperature no longer rises, add an appropriate amount of hydrogen peroxide until no more bubbles are generated.

[0041] (3) After standing for a period of time, centrifuge at high speed and wash with deionized water to make it neutral;

[0042] (4) Dry the obtained product in a forced-air drying oven at 30-80℃;

[0043] (5) Prepare expanded microcrystalline graphite by keeping it at 600-900℃ for 5-20 minutes in an inert atmosphere;

[0044] (6) Weigh 0.1-0.5g of expanded microcrystalline graphite and 0.01-0.5g of FeCl3·6H2O and put them into a beaker, and sonicate for 20-50 minutes;

[0045] (7) Stir in a water bath at 60-90℃ for 3-6 hours, let stand for a period of time, and then filter.

[0046] (8) Place the obtained product in a 40-80℃ forced-air drying oven for 3-8 hours;

[0047] (9) Prepare expanded microcrystalline graphite / Fe2O3 composite materials with different Fe2O3 mass fractions by keeping them in air at 200-800℃ for 1-2 hours;

[0048] (10) Weigh 0.1-1g of SnCl2·2H2O and dissolve it in 10-20mL of concentrated sulfuric acid. Stir magnetically until completely dissolved.

[0049] (11) Weigh 0.01-0.5g of L-ascorbic acid and dissolve it in 10-20mL of deionized water;

[0050] (12) Add SnCl2 solution dropwise to the aqueous solution of L-ascorbic acid, stir magnetically for 10-30 min, then add 0.1-0.5 g of expanded microcrystalline graphite / Fe2O3 composite material and stir for 10-40 min;

[0051] (13) React in a reactor at 100-200℃ for 1-3 hours, extract the black precipitate with a centrifuge, wash with deionized water until neutral, and dry in a forced-air drying oven at 50-80℃ for 1-3 hours.

[0052] (14) The obtained material was kept at 300-700℃ in air for 1-2 hours to prepare composite materials of expanded microcrystalline graphite / Fe2O3 / SnO2 with different contents;

[0053] (15) The expanded microcrystalline graphite / Fe2O3 / SnO2 composite material prepared was used as the negative electrode of lithium-ion battery.

[0054] Example 1: Under ice-water bath conditions, 5g of high-purity microcrystalline graphite was added to a beaker containing 80mL of concentrated sulfuric acid, followed by 50mL of potassium permanganate, and stirred for 50min. After stirring for another 30min in a 50℃ water bath, deionized water was added for dilution. When the temperature stopped rising, an appropriate amount of hydrogen peroxide was added until no more bubbles were generated. After standing for a period of time, the product was centrifuged at high speed and washed with deionized water to neutralize it. The resulting product was dried in a 60℃ forced-air oven. Expanded microcrystalline graphite was prepared by oxidation and inert atmosphere heat treatment at 800℃ for 15min.

[0055] Weigh 0.3g of expanded microcrystalline graphite and 0.2g of FeCl3·6H2O into a beaker and sonicate for 30min; stir in a 70℃ water bath for 5h, let stand for a period of time and then filter; place the obtained product in a 60℃ forced-air drying oven for 5h; keep warm in air at 500℃ for 1.5h, and prepare expanded microcrystalline graphite / Fe2O3 composite materials with different Fe2O3 mass fractions using water bath method and air atmosphere heat treatment method I.

[0056] 0.5 g of SnCl2·2H2O was dissolved in 15 mL of concentrated sulfuric acid and magnetically stirred until completely dissolved. 0.3 g of L-ascorbic acid was dissolved in 15 mL of deionized water. The SnCl2 solution was added dropwise to the L-ascorbic acid aqueous solution and magnetically stirred for 20 min. Then, 0.3 g of expanded microcrystalline graphite / Fe2O3 composite material was added and stirred for 30 min. The mixture was reacted in a reactor at 150 °C for 2 h. The black precipitate was extracted using a centrifuge and washed with deionized water until neutral. The precipitate was dried in a forced-air drying oven at 60 °C for 2 h. The resulting material was kept at 500 °C in air for 2 h. Expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials with different contents were prepared using hydrothermal method and air atmosphere heat treatment method II. The prepared expanded microcrystalline graphite / Fe2O3 / SnO2 composite material was used as the negative electrode of a lithium-ion battery.

[0057] like Figure 1 As shown, microcrystalline graphite expands in volume and exhibits a porous structure. Figure 2 As shown, Fe2O3 and SnO2 nanoparticles are tightly bonded and distributed together on the surface and between layers of micron-sized expanded microcrystalline graphite.

[0058] The electrochemical performance testing method for composite materials is as follows: using Shenzhen Xinweier BTS-5V / 2.2A battery testing equipment, the temperature is constant at 25℃, and the test voltage range is 0.01~3V.

[0059] Comparative Example 1: 10g of high-purity microcrystalline graphite was weighed according to the water bath method in Example 1, and the rest of the operation process was the same as in Example 1.

[0060] Comparative Example 2: The inert atmosphere heat treatment method in Example 1 was followed, with a heat treatment temperature of 600°C and the remaining operation process being the same as in Example 1.

[0061] Table 1 Electrochemical properties of expanded microcrystalline graphite / Fe2O3 / SnO2 composite material I

[0062]

[0063]

[0064] Example 2: Under ice-water bath conditions, 1g of high-purity microcrystalline graphite was added to a beaker containing 50mL of concentrated sulfuric acid, followed by 50mL of potassium permanganate, and stirred for 30min. After stirring for another 20min in a 20℃ water bath, deionized water was added for dilution. When the temperature no longer rose, an appropriate amount of hydrogen peroxide was added until no more bubbles were generated. After standing for a period of time, the product was centrifuged at high speed and washed with deionized water to neutralize it. The resulting product was dried in a 60℃ forced-air oven and kept at 700℃ for 5min in an inert atmosphere. Expanded microcrystalline graphite was prepared by oxidation and inert atmosphere heat treatment.

[0065] Weigh 0.1g of expanded microcrystalline graphite and 0.01g of FeCl3·6H2O into a beaker and sonicate for 30min; stir in a 60℃ water bath for 3h, let stand for a period of time and then filter; place the obtained product in a 50℃ forced-air drying oven for 3h; keep in air at 300℃ for 1h, and prepare expanded microcrystalline graphite / Fe2O3 composite materials with different Fe2O3 mass fractions using water bath method and air atmosphere heat treatment method I.

[0066] 0.2 g of SnCl2·2H2O was dissolved in 10 mL of concentrated sulfuric acid and magnetically stirred until completely dissolved. 0.03 g of L-ascorbic acid was dissolved in 10 mL of deionized water. The SnCl2 solution was added dropwise to the L-ascorbic acid aqueous solution and magnetically stirred for 10 min. Then, 0.2 g of expanded microcrystalline graphite / Fe2O3 composite material was added and stirred for 10 min. The mixture was reacted in a reactor at 100 °C for 1 h. The black precipitate was extracted using a centrifuge and washed with deionized water until neutral. The precipitate was dried in a forced-air drying oven at 50 °C for 1 h. The resulting material was kept at 300 °C in air for 2 h. Expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials with different contents were prepared using hydrothermal method and air atmosphere heat treatment method II. The prepared expanded microcrystalline graphite / Fe2O3 / SnO2 composite material was used as the negative electrode of a lithium-ion battery.

[0067] The electrochemical performance testing method for composite materials is as follows: using Shenzhen Xinweier BTS-5V / 2.2A battery testing equipment, the temperature is constant at 25℃, and the test voltage range is 0.01~3V.

[0068] Comparative Example 3: Following the water bath method in Example 2, 0.8 g of expanded microcrystalline graphite and 0.5 g of FeCl3·6H2O were weighed, and the remaining operations were the same as in Example 2.

[0069] Comparative Example 4: The air atmosphere heat treatment method I in Example 2 was followed, with the temperature of the air being 800°C, and the rest of the operation process being the same as in Example 2.

[0070] Table 2 Electrochemical properties of expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials II

[0071]

[0072] Example 3: Under ice-water bath conditions, 10g of high-purity microcrystalline graphite was added to a beaker containing 100mL of concentrated sulfuric acid, followed by 100mL of potassium permanganate, and stirred for 60min. After stirring for another 40min in a 50℃ water bath, deionized water was added for dilution. When the temperature stopped rising, an appropriate amount of hydrogen peroxide was added until no more bubbles were generated. After standing for a period of time, the product was centrifuged at high speed and washed with deionized water to neutralize it. The resulting product was dried in an 80℃ forced-air oven. It was then kept at 900℃ for 20min in an inert atmosphere to prepare expanded microcrystalline graphite using oxidation and inert atmosphere heat treatment methods.

[0073] Weigh 0.5g of expanded microcrystalline graphite and 0.5g of FeCl3·6H2O into a beaker and sonicate for 50min; stir in a 90℃ water bath for 6h, let stand for a period of time and then filter; place the obtained product in an 80℃ forced-air drying oven for 8h; keep warm in air at 800℃ for 2h, and prepare expanded microcrystalline graphite / Fe2O3 composite materials with different Fe2O3 mass fractions using water bath method and air atmosphere heat treatment method I.

[0074] 1 g of SnCl2·2H2O was dissolved in 20 mL of concentrated sulfuric acid and magnetically stirred until completely dissolved. 0.5 g of L-ascorbic acid was dissolved in 20 mL of deionized water. The SnCl2 solution was added dropwise to the L-ascorbic acid aqueous solution and magnetically stirred for 30 min. Then, 0.5 g of expanded microcrystalline graphite / Fe2O3 composite material was added and stirred for 40 min. The reaction was carried out in a reactor at 200 °C for 3 h. The black precipitate was extracted using a centrifuge and washed with deionized water until neutral. The precipitate was dried in a forced-air drying oven at 80 °C for 3 h. The resulting material was kept at 700 °C in air for 2 h. Expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials with different contents were prepared using hydrothermal method and air atmosphere heat treatment method II. The prepared expanded microcrystalline graphite / Fe2O3 / SnO2 composite material was used as the negative electrode of a lithium-ion battery.

[0075] The electrochemical performance testing method for composite materials is as follows: using Shenzhen Xinweier BTS-5V / 2.2A battery testing equipment, the temperature is constant at 25℃, and the test voltage range is 0.01~3V.

[0076] Comparative Example 5: Following the hydrothermal method in Example 3, 0.3g of SnCl2·2H2O was weighed out, and the rest of the operation process was the same as in Example 3.

[0077] Comparative Example 6: 0.3g of expanded microcrystalline graphite / Fe2O3 composite material was weighed according to the hydrothermal method in Example 3, and the rest of the operation process was the same as in Example 3.

[0078] Comparative Example 7: The air atmosphere heat treatment method II in Example 3 was followed, with the temperature of the air being 600°C, and the rest of the operation process being the same as in Example 3.

[0079] Table 3 Electrochemical properties of expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials III

[0080]

[0081] Application effects of the present invention:

[0082] (1) Expanded microcrystalline graphite / Fe2O3 / SnO2 lithium-ion battery anode materials prepared by oxidation method and inert atmosphere heat treatment method, water bath method and air atmosphere heat treatment method I, hydrothermal method and air atmosphere heat treatment method II, the microcrystalline graphite exhibits overall volume expansion and significantly improved porosity.

[0083] (2) The initial charge-discharge specific capacity of the ternary composite material is 1539.9 mAh / g, the initial coulombic efficiency is 70.1%, and after 100 cycles, it still has a reversible specific capacity of 1003.2 mAh / g, with a capacity retention rate of 62.9%.

[0084] (3) The synergistic effect of micro and nano structures can effectively suppress the volume expansion of metal oxides while improving lithium storage capacity.

[0085] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a micro / nano anode material for expanded microcrystalline graphite / Fe2O3 / SnO2 lithium-ion batteries, characterized in that, Includes the following steps: First, expanded microcrystalline graphite was prepared using high-purity microcrystalline graphite as raw material by oxidation and inert atmosphere heat treatment. Secondly, expanded microcrystalline graphite / Fe2O3 composite materials were prepared using water bath method and air atmosphere heat treatment method I; Finally, expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials were prepared using hydrothermal method and air atmosphere heat treatment method II; The preparation of expanded microcrystalline graphite using high-purity microcrystalline graphite as raw material, employing oxidation and inert atmosphere heat treatment methods, includes the following steps: Step (1): Under ice-water bath conditions, add 1-10g of high-purity microcrystalline graphite to a beaker containing 50-100mL of concentrated sulfuric acid, then add 50-100mL of potassium permanganate and stir for 30-60min. Step (2): Continue stirring in a water bath at 20-50℃ for 10-40 minutes, then add deionized water to dilute. When the temperature stops rising, add an appropriate amount of hydrogen peroxide until no more bubbles are generated. Step (3): After standing for a period of time, centrifuge at high speed and wash with deionized water to make it neutral; Step (4): Dry the obtained product in a forced-air drying oven at 30-80℃; Step (5): Prepare expanded microcrystalline graphite by keeping it at 600-900℃ for 5-20 minutes in an inert atmosphere; The preparation of expanded microcrystalline graphite / Fe2O3 composite material using water bath method and air atmosphere heat treatment method I includes the following steps: Step (1): Weigh 0.1-0.5g of expanded microcrystalline graphite and 0.01-0.5g of FeCl3·6H2O into a beaker and sonicate for 20-50 minutes; Step (2): Stir in a water bath at 60-90℃ for 3-6 hours, let stand for a period of time, and then filter. Step (3): Place the obtained product in a 40-80℃ forced-air drying oven for 3-8 hours; Step (4): Prepare expanded microcrystalline graphite / Fe2O3 composite materials with different Fe2O3 mass fractions by keeping the temperature at 200-800℃ in air for 1-2 hours; The preparation of expanded microcrystalline graphite / Fe2O3 / SnO2 composite material using hydrothermal method and air atmosphere heat treatment method II includes the following steps: Step (1): Weigh 0.1-1g of SnCl2·2H2O and dissolve it in 10-20mL of concentrated sulfuric acid. Stir magnetically until completely dissolved. Step (2): Weigh 0.01-0.5g of L-ascorbic acid and dissolve it in 10-20mL of deionized water; Step (3): Add SnCl2 solution dropwise to the aqueous solution of L-ascorbic acid, stir magnetically for 10-30 min, then add 0.1-0.5 g of expanded microcrystalline graphite / Fe2O3 composite material and stir for 10-40 min; Step (4): React in a reactor at 100-200℃ for 1-3 hours, extract the black precipitate with a centrifuge, wash with deionized water until neutral, and dry in a forced-air drying oven at 50-80℃ for 1-3 hours; Step (5): The obtained material is kept at 300-700℃ in air for 1-2 hours to prepare expanded microcrystalline graphite / Fe2O3 / SnO2 composite materials with different contents.

2. The expanded microcrystalline graphite / Fe2O3 / SnO2 composite material prepared by the preparation method described in claim 1.

3. The application of the expanded microcrystalline graphite / Fe2O3 / SnO2 composite material as described in claim 2 in the negative electrode of a lithium-ion battery.

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