Fullerene polymer material, negative electrode material, lithium ion battery and preparation method of lithium ion battery

Abstract

The invention provides a fullerene polymer material, a negative electrode material, a negative electrode plate, a lithium ion battery and a preparation method of the lithium ion battery. The fullerene polymer material provided by the invention comprises a fullerene polymer and alkaline earth metal ions doped in the fullerene polymer, the molar ratio of the alkaline earth metal ions to the fullerene molecules is (0.01-1): 1. Alkaline-earth metal is adopted to induce fullerene molecules to be covalently connected, then an acidic reagent is adopted to remove part of alkaline-earth metal ions, the fullerene polymer material of a three-dimensional layered network structure is obtained, the fullerene polymer material is good in stability and large in interlayer gap, has more adsorption sites, and has a good adsorption effect when being used as a negative electrode material. The lithium ion intercalation and deintercalation efficiency is high, and the specific capacity, the rate capability and the cycle performance of the lithium ion battery can be improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of energy storage materials, in particular to a fullerene polymer material, a negative electrode material, a lithium ion battery and a preparation method thereof. BACKGROUND

[0002] With the rapid popularization of portable electronic devices, electric vehicles and large-scale energy storage systems, the demand for high energy density, long cycle life and high safety of lithium ion batteries is increasingly urgent. As one of the core components of the battery, the performance of the negative electrode material directly determines the overall electrochemical performance of the battery - it not only needs to have high specific capacity to improve the endurance, but also needs to have good cycle stability to cope with the structural changes in the repeated charging and discharging process.

[0003] At present, graphite materials (natural graphite, artificial graphite) are still the mainstream choice for lithium ion battery negative electrode materials, which have the advantages of good cycle stability and mature process, but the low theoretical specific capacity (only 372 mAh g −1 ) has become a key short board restricting the improvement of battery energy density. In addition, the lithium intercalation potential of graphite is close to the lithium deposition potential, which is easy to cause lithium metal dendrite growth during charging and discharging, seriously threatening the safety of the battery. In order to break through the capacity limit of graphite, researchers have turned their attention to high-capacity new materials, such as new carbon-based materials (carbon nanotubes, graphene, fullerenes), silicon-based materials (silicon, silicon oxide, silicon alloy) and transition metal selenides (such as MoSe2, FeSe2). Among them, new carbon-based materials (carbon nanotubes, graphene, fullerenes) have the advantages of large specific surface area, excellent electrical conductivity and good stability, and are very suitable for preparing high-performance lithium ion batteries. At present, many researchers continue to explore the application of new carbon-based materials in lithium battery negative electrodes.

[0004] In recent years, fullerenes C 60 have attracted the attention of many battery researchers. Fullerenes C 60 have a unique spherical molecular structure ("buckyball" composed of 60 carbon atoms), and their high specific surface area (nanoscale fullerenes have a larger specific surface area) and rich electronic system can provide more storage sites for lithium ions; the electronic transmission performance of fullerenes C 60 is also outstanding, with a carrier mobility of 0.08~0.3 cm 2 V −1 s −1 , which can effectively reduce the electronic transmission resistance in the electrode. After modification and regulation of pure fullerenes C 60 and fullerenes C 60 , fullerenes C 60The research on new carbon materials as anode materials for lithium ion batteries is gradually carried out at home and abroad. For example, Linghong Yin et al. prepared pure fullerene C 60 After nanoization, the particles were used as anode materials for lithium ion batteries, and it was found that, in the second discharge process of lithium ion batteries, C 60 The nanoparticles reached a specific capacity of 750 mAh g −1 at a current density of 0.1 A g −1 , which was about twice that of a graphite electrode, but the cycle stability thereof needs to be improved. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to provide a fullerene polymer material, an anode material, a lithium ion battery and a preparation method thereof. The fullerene polymer material provided by the present application has high capacity and good cycle stability when used as an anode material for a lithium ion battery.

[0006] The present application provides a fullerene polymer material, comprising a fullerene polymer and alkaline earth metal ions doped in the fullerene polymer.

[0007] The molar ratio of the alkaline earth metal ions to the fullerene molecules is 0.01-1:1.

[0008] In some specific implementation manners, the alkaline earth metal ions are one or more of magnesium ions, calcium ions, strontium ions and barium ions.

[0009] The fullerene molecules are one or more of fullerene C 60 , fullerene C 70 , fullerene C 80 and fullerene C 82 .

[0010] In some specific implementation manners, the molar ratio of the alkaline earth metal ions to the fullerene molecules is 0.1-0.8:1.

[0011] In some specific implementation manners, the fullerene polymer material has a layered structure.

[0012] The present application also provides an anode material, comprising a binder, a conductive agent and the fullerene polymer material according to the above technical solution.

[0013] In some specific implementation manners, the binder comprises one or more of sodium carboxymethyl cellulose, sodium alginate and polyvinylidene fluoride.

[0014] The conductive agent comprises one or more of Ketjen black, conductive carbon black and carbon nanotubes.

[0015] The mass ratio of the fullerene polymer material, the binder and the conductive agent is 5-10:1:1.

[0016] The application also provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector.

[0017] The negative electrode active material layer comprises the negative electrode material described in the above technical solution.

[0018] The application also provides a lithium ion battery comprising the negative electrode material described in the above technical solution or the negative electrode sheet described in the above technical solution.

[0019] The application also provides a preparation method of the fullerene polymer material described in the above technical solution, comprising the following steps:

[0020] a) encapsulating an alkaline earth metal and a fullerene molecular crystal in a sealed container;

[0021] b) performing heat treatment on the sealed container to obtain a metal-doped fullerene polymer crystal material;

[0022] c) performing acid pickling on the metal-doped fullerene polymer crystal material, and obtaining a fullerene polymer material after drying.

[0023] In some specific implementations, in the step a), the sealed container is a quartz tube.

[0024] The molar ratio of the alkaline earth metal and the fullerene molecular crystal is 4-40:1.

[0025] After encapsulation, the pressure of the sealed container is 0.01 Pa-100 Pa.

[0026] In the step b), the heat treatment is performed in an air atmosphere, the temperature is 200℃-1000℃, the time is 1h-60h, and the temperature rising rate is 1-20℃ / min. −1 ;

[0027] In the step c), the acid reagent used for the acid pickling is one or more of nitric acid, hydrochloric acid, sulfuric acid and acetic acid.

[0028] The time for the acid pickling is 2h-20h.

[0029] The fullerene polymer material provided in the application comprises a fullerene polymer and alkaline earth metal ions doped in the fullerene polymer; the molar ratio of the alkaline earth metal ions to the fullerene molecules is 0.01-1:1. The application adopts alkaline earth metal to induce covalent connection of fullerene molecules, and then removes part of the alkaline earth metal ions by using an acidic reagent, to obtain a three-dimensional layered network structure of the fullerene polymer material. The fullerene polymer material has good stability, large interlayer gap and more adsorption sites. When used as a negative electrode material, the lithium ion embedding and extraction efficiency is high, and the specific capacity, rate performance and cycle performance of the lithium ion battery can be improved. The experimental results show that the lithium ion battery prepared by using the fullerene polymer material provided in the application can achieve a high reversible specific capacity of greater than 700 mAh g −1 at a current density of 0.1 A g −1 , and can maintain a specific capacity of about 500 mAh g −1 after 100 cycles, and can maintain a specific capacity of about 280 mAh g −1 at a high current density of 5 A g −1 . BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a scanning electron microscope image of the material before acid washing;

[0031] Figure 2 is a scanning electron microscope image of the material after acid washing;

[0032] Figure 3 is a Raman spectrum of the material before and after acid washing;

[0033] Figure 4 is an X-ray diffraction pattern of the material before and after acid washing;

[0034] Figure 5 is an EDS energy spectrum test result of the material after acid washing;

[0035] Figure 6 is a cyclic voltammetry test result of the half battery prepared in Example 1 of the application;

[0036] Figure 7 is a rate performance test result of the half battery prepared in Example 1 of the application;

[0037] Figure 8 is a cycle performance test result of the half battery prepared in Example 1 of the application. DETAILED DESCRIPTION

[0038] The application provides a fullerene polymer, a negative electrode material, a lithium ion battery and a preparation method thereof. Those skilled in the art can refer to the content herein, and appropriately improve the process parameters to achieve the method and application of the application.

[0039] The application provides a fullerene polymer material, which comprises a fullerene polymer and alkaline earth metal ions doped in the fullerene polymer.

[0040] The molar ratio of the alkaline earth metal ions to the fullerene molecules is 0.01-1:1.

[0041] The fullerene polymer material provided by the application comprises a fullerene polymer, and the fullerene polymer is formed by covalent connection of fullerene molecules. In some specific implementation manners, the fullerene molecules comprise but are not limited to fullerene C 60 , fullerene C 70 , fullerene C 80 , fullerene C 82 , etc., and can be one or more of them. When the fullerene molecules are a combination of multiple substances, the application does not have special limitations on the specific ratio thereof. In some specific implementation manners, the fullerene is preferably fullerene C 60 .

[0042] The fullerene polymer material provided by the application comprises alkaline earth metal ions doped in the fullerene polymer, and the alkaline earth metal ions comprise but are not limited to magnesium ions (Mg 2+ ), calcium ions (Ca 2+ ), strontium ions (Sr 2+ ) and barium ions (Ba 2+ ), etc., and can be one or more of them. When the alkaline earth metal ions are a combination of multiple substances, the application does not have special limitations on the specific ratio thereof. In some specific implementation manners, the alkaline earth metal ions are preferably magnesium ions.

[0043] In the fullerene polymer material provided by the application, the molar ratio of the alkaline earth metal ions to the fullerene molecules is 0.01-1:1, preferably 0.1-0.8:1, and more preferably 0.2-0.6:1.

[0044] The fullerene polymer material provided by the application has a three-dimensional layered structure, and the interlayer gap is large. In some specific implementation manners, the fullerene polymer material has a three-dimensional layered network structure, and the structure is stable.

[0045] The fullerene polymer material provided by the application can be used as a negative electrode material of a lithium ion battery, has more adsorption sites, and can improve the efficiency of lithium ion intercalation and deintercalation.

[0046] The application further provides a preparation method of the fullerene polymer material in the technical solution.

[0047] a) encapsulating the alkaline earth metal and the fullerene molecular crystal in a closed container;

[0048] b) performing heat treatment on the closed container to obtain a metal-doped fullerene polymer crystal material;

[0049] c) performing acid washing on the metal-doped fullerene polymer crystal material, and obtaining the fullerene polymer material after drying.

[0050] The application uses an alkaline earth metal and a fullerene molecular crystal as raw materials, and first encapsulates them in a closed container. In some specific implementation manners, the alkaline earth metal is an alkaline earth metal powder, for example, magnesium powder, calcium powder, strontium powder, barium powder, etc., and is preferably magnesium powder. In some specific implementation manners, the purity of the alkaline earth metal is greater than 99%. In some specific implementation manners, the fullerene molecular crystal is a fullerene molecular crystal powder, for example, fullerene C60 powder, fullerene C70 powder, fullerene C76 powder, fullerene C84 powder, fullerene C90 powder, fullerene C94 powder, etc. In some specific implementation manners, the purity of the fullerene molecular crystal is greater than 99.5%. In some specific implementation manners, the closed container is a quartz tube. In some specific implementation manners, the length of the quartz tube is 10 cm to 50 cm, and the diameter is 1 cm to 5 cm. 60 In some specific implementation manners, the length of the quartz tube is 10 cm to 50 cm, and the diameter is 1 cm to 5 cm. 70 In some specific implementation manners, the length of the quartz tube is 10 cm to 50 cm, and the diameter is 1 cm to 5 cm. 80 In some specific implementation manners, the length of the quartz tube is 10 cm to 50 cm, and the diameter is 1 cm to 5 cm. 82 In some specific implementation manners, the length of the quartz tube is 10 cm to 50 cm, and the diameter is 1 cm to 5 cm.

[0051] Specifically, the application first adds the alkaline earth metal and the fullerene molecular crystal into the closed container under an inert atmosphere, performs high-temperature vacuum encapsulation on the closed container, and keeps the inside of the closed container in a low-pressure state. In some specific implementation manners, the alkaline earth metal and the fullerene molecular crystal can be first mixed uniformly under an inert gas and then added into the closed container, or the alkaline earth metal and the fullerene molecular crystal can be added into the closed container respectively, for example, the alkaline earth metal and the fullerene molecular crystal are added into two ends of the quartz tube respectively. In some specific implementation manners, the molar ratio of the alkaline earth metal to the fullerene molecular crystal is 4 to 40:1, preferably 5 to 35:1, and more preferably 8 to 30:1. In some specific implementation manners, after encapsulation, the pressure of the closed container is 0.01 Pa to 100 Pa, preferably 1 Pa to 90 Pa, and more preferably 10 Pa to 60 Pa.

[0052] After the encapsulation, the sealed container is subjected to a heating treatment to obtain a metal-doped fullerene polymer crystal material. In some specific embodiments, the heating treatment is performed in an air atmosphere, the heating temperature is 200-1000°C, preferably 200-800°C, more preferably 300-800°C, the heating time is 1-60h, preferably 2-40h, more preferably 10-35h, and the heating rate is 1-20°C / min, preferably 3-15°C / min, more preferably 5-10°C / min. −1 ~20°C / min −1 , preferably 3°C / min −1 ~15°C / min −1 , more preferably 5°C / min −1 ~10°C / min −1 In some specific embodiments, the heating treatment is performed in a double-temperature-zone tube furnace. In some specific embodiments, the reactants containing fullerene molecular crystals are placed in the center of the high-temperature zone, specifically, when the alkaline earth metal and the fullerene molecular crystals are mixed uniformly in an inert gas and then added to the sealed container, the reactants in the sealed container are placed in the center of the high-temperature zone of the double-temperature-zone tube furnace; the alkaline earth metal and the fullerene molecular crystals are added to the two ends of the sealed container, respectively, the alkaline earth metal is placed in the center of the low-temperature zone of the double-temperature-zone tube furnace, and the fullerene molecular crystals are placed in the center of the high-temperature zone of the double-temperature-zone tube furnace. In some specific embodiments, the reaction temperature of the high-temperature zone is 500-800°C, preferably 600-800°C, more preferably 700-800°C, and the reaction temperature of the low-temperature zone is 200-500°C, preferably 300-500°C, more preferably 400-500°C.

[0053] After the reaction is completed, the crystals grown on the wall of the sealed container are selected and subjected to an acid washing, i.e., the crystals are soaked with an acidic reagent to remove most of the metal elements therein. In some specific embodiments, the acid washing is performed under stirring, and the stirring rate has no special limitation and can be any parameter commonly used by those skilled in the art. In some specific embodiments, the acidic reagent used in the acid washing is nitric acid, hydrochloric acid, sulfuric acid, acetic acid, or a combination thereof. In some specific embodiments, the concentration of the acidic reagent is 0.1-5mol / L, preferably 0.5-3mol / L, more preferably 1-2mol / L. In some specific embodiments, the temperature of the acid washing is 10-100°C, preferably 15-90°C, more preferably 20-80°C. In some specific embodiments, the acid washing time is 2-20h, preferably 3-15h, more preferably 4-12h.

[0054] After the acid washing, the obtained material is vacuum filtered and cleaned with ethanol and water to obtain fullerene polymer powder. The specific parameters and specific operations of the vacuum filtration and cleaning are not particularly limited in the present application, and the operations commonly used by those skilled in the art can be used.

[0055] After obtaining the fullerene polymer powder, it is vacuum dried to obtain a fullerene polymer material. In some specific implementations, the temperature of the vacuum drying is 80-120°C, preferably 90-110°C, and more preferably 100°C; the time of the vacuum drying is 10-20h, preferably 12-18h. After vacuum drying, the obtained material is ground to obtain a fullerene polymer material that can be used as a negative electrode material.

[0056] The present application induces covalent connection of fullerene molecules to form a fullerene polymer by using an alkaline earth metal, then removes the metal element in the fullerene polymer using an acidic reagent, and grinds after drying to obtain a three-dimensional layered fullerene polymer with stable structure and large interlayer gap, which can be used as a negative electrode material for lithium ion batteries. The preparation method provided by the present application is simple and easy to control, and the material obtained by using it as a negative electrode material for lithium ion batteries has high specific capacity and good cycle stability.

[0057] The present application also provides a negative electrode material comprising a binder, a conductive agent and the fullerene polymer material described in the above technical solution.

[0058] The negative electrode material provided by the present application comprises the fullerene polymer material described in the above technical solution, which will not be described here again.

[0059] The negative electrode material provided by the present application comprises a binder. In some specific implementations, the binder includes but is not limited to sodium carboxymethyl cellulose, sodium alginate, and polyvinylidene fluoride, etc., and can be one or more of them. When the binder is a combination of multiple substances, the present application does not have a special limitation on the proportion of each specific substance.

[0060] The negative electrode material provided by the present application comprises a conductive agent. In some specific implementations, the conductive agent includes but is not limited to Ketjen black, conductive carbon black, and carbon nanotubes, and can be one or more of them. When the conductive agent is a combination of multiple substances, the present application does not have a special limitation on the proportion of each specific substance.

[0061] In the negative electrode material provided by the present application, the mass ratio of the fullerene polymer material, the binder and the conductive agent is 5-10:1:1, preferably 6-9:1:1, and more preferably 7-8:1:1.

[0062] The present application does not have a special limitation on the preparation method of the negative electrode material, and the raw materials can be mixed uniformly.

[0063] The application also provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector.

[0064] The negative electrode active material layer comprises the negative electrode material in the above technical solution.

[0065] The negative electrode sheet provided by the application comprises a negative electrode current collector, which is a metal material, preferably a copper foil, including but not limited to a pure copper foil, a carbon-coated copper foil and the like.

[0066] The negative electrode sheet provided by the application comprises a negative electrode active material layer formed on at least one surface of the negative electrode current collector, and the negative electrode material layer is formed of the negative electrode material in the above solution, which will not be described herein again.

[0067] The preparation method of the negative electrode sheet is not particularly limited, the negative electrode material is uniformly mixed to form a slurry, which is coated on the surface of the negative electrode current collector, and the negative electrode sheet can be obtained after drying. The coating is not particularly limited, for example, the negative electrode material can be evenly coated on the negative electrode current collector by using a doctor blade.

[0068] The application also provides a lithium ion battery comprising the negative electrode material in the above technical solution or the negative electrode sheet in the above technical solution.

[0069] The fullerene polymer material provided by the application comprises a fullerene polymer and alkaline earth metal ions doped in the fullerene polymer; the molar ratio of the alkaline earth metal ions to the fullerene molecules is 0.01-1:1. The alkaline earth metal is used to induce the covalent connection of the fullerene molecules, and then part of the alkaline earth metal ions are removed by using an acidic reagent, so that a three-dimensional layered network structure of the fullerene polymer material is obtained. The fullerene polymer material has good stability, large interlayer space and more adsorption sites. When used as a negative electrode material, the lithium ion intercalation and deintercalation efficiency is high, and the specific capacity, rate performance and cycle performance of the lithium ion battery can be improved. Experimental results show that the lithium ion battery prepared by using the fullerene polymer material provided by the application can achieve a high reversible specific capacity of greater than 700 mAh g-1 at a current density of 0.1 A g-1, and can maintain a specific capacity of about 500 mAh g-1 after 100 cycles, and can still maintain a specific capacity of about 280 mAh g-1 at a high current density of 5 A g-1. −1 −1 −1 −1 −1

[0070] ​​​​​The application will be further described in detail in connection with the following examples. It is particularly pointed out that, in the following examples, the specific conditions not noted are carried out according to the conventional conditions or the conditions recommended by the manufacturer, and the raw materials used in the following examples can be sourced from the commonly commercially available, except for the special instructions.

[0071] Example 1

[0072] The alkali earth metal magnesium powder with a purity of 99% and the fullerene C 60 powder with a purity of 99.5% are uniformly mixed in an inert atmosphere, loaded into a quartz tube with a length of 15 cm and a tube diameter of 5 cm, and the molar ratio of the two is controlled to be 40:1. The quartz tube is high-temperature vacuum packaged, and the internal gas pressure is 10 Pa. The packaged quartz tube is placed horizontally in a double-temperature zone tube furnace, while ensuring that the reactants in the quartz tube are at the center position of the high-temperature zone and the other end is at the center position of the low-temperature zone. The high-temperature zone and the low-temperature zone are set to 750 ℃ and 500 ℃ respectively, and the heating rate is 5 ℃ min −1 , and the reaction is carried out under air atmosphere for 24 h to obtain fullerene polymer Mg4C 60 crystals. The crystals grown on the wall of the tube are selected, and most of the Mg element is removed by soaking with 1 mol L −1 of nitric acid reagent, and the washing time is 12 h. Then vacuum filtration is carried out, and ethanol and deionized water are used for auxiliary cleaning to obtain fullerene C 60 polymer powder with clean composition. The obtained fullerene polymer powder is placed in a vacuum drying box and dried at 100 ℃ for 12 h, and then ground to obtain fullerene C 60 polymer material for lithium ion battery negative electrode material.

[0073] The materials before and after acid pickling are observed by scanning electron microscopy, detected by Raman spectrum, and analyzed by X-ray diffraction. The results are shown in Figure 1 , Figure 2 , Figure 3 and Figure 4 , Figure 1 is a scanning electron micrograph of the material before acid pickling, Figure 2 is a scanning electron micrograph of the material after acid pickling, Figure 3 is a Raman spectrum of the material before and after acid pickling, Figure 4 is an X-ray diffraction pattern of the material before and after acid pickling. As can be seen from Figures 1 to 4 , the fullerene C 60 polymer prepared in the application has a three-dimensional layered structure, and the Raman spectrum test results show that the peaks of the polymer at 910 cm -1 and 970 cm -1 Raman shift before and after acid pickling correspond to C 60The bridge signal between the ball cages remains, and the X-ray diffraction test results show that the polymer crystal is washed by acid, and the peak signal of the (200) and (400) crystal planes is shifted to the left, corresponding to the expansion of the interlayer spacing, that is, after acid washing, we obtain a stable three-dimensional layered C 60 polymer.

[0074] The obtained fullerene C 60 The elemental analysis of the polymer material is shown in Table 1. Figure 5 , Figure 5 The elemental analysis of the fullerene C 60 The polymer material prepared in Example 1 is shown in Table 1. Figure 5 It can be seen that the fullerene C 60 The polymer material provided by the application comprises fullerene C 60 Polymer and Mg 2+ doped therein. 2+ The molar ratio of Mg 60 and fullerene C −1 is 0.5:1.

[0075] Based on the prepared fullerene C60 polymer material, it is ground with sodium alginate and Ketjen black at a ratio of 8:1:1, uniformly mixed, and then the obtained slurry is evenly coated on a carbon-coated copper foil by scraping. After vacuum drying, an electrode sheet is obtained. The battery is assembled in an argon atmosphere, the oxygen content in the argon atmosphere is less than 1 ppm, the water content is less than 1 ppm, and the electrolyte is 1 mol L 60 Lithium hexafluorophosphate is dissolved in a mixed solution of diethyl carbonate-ethylene carbonate (volume ratio 1:1) and 10% fluoroethylene carbonate. The assembled lithium ion half-cell is subjected to constant current charge and discharge performance test, and the test voltage is 0.01V~3 V. The test results are shown in Figure 6 、 Figure 7 and Figure 8 , Figure 6 The cyclic voltammetry test results of the half-cell prepared in Example 1 of the application are shown in Table 2. Figure 7 The rate performance test results of the half-cell prepared in Example 1 of the application are shown in Table 3. Figure 8 The cycle performance test results of the half-cell prepared in Example 1 of the application are shown in Table 4. Figures 6 to 8 It can be seen that the fullerene C −1 Polymer material provided by the application has a first reversible specific capacity of 711 mAh g −1 at a current density of 0.1 A g −1 , a first coulombic efficiency of 95.1%, a reversible specific capacity of 533 mAh g −1 after 100 cycles, a cycle retention rate of 74.9%, and still maintains 275 mAh g−1 Specific capacity.

[0076] Example 2

[0077] It uses 99% pure alkaline earth metal magnesium strip and 99.5% pure fullerene C. 60 The powder was separately packed into both ends of a quartz tube 40 cm long and 2 cm in diameter under an inert atmosphere, with a molar ratio of 30:1. The quartz tube was then vacuum-sealed at a high temperature with an internal pressure of 60 Pa. The sealed quartz tube was then placed horizontally in a dual-temperature zone tube furnace, while ensuring that the carbon content in the quartz tube was maintained at a constant level. 60 The powder is positioned at the center of the high-temperature zone, and the magnesium strip is positioned at the center of the low-temperature zone. The high-temperature zone is set to 700 °C, and the low-temperature zone to 450 °C, with a heating rate of 10 °C / min. −1 The reaction was carried out in air for 30 h to obtain the fullerene polymer Mg4C. 60 Crystals. Crystals grown on the tube wall were selected and analyzed using 1 mol L... −1 Most of the Mg element was removed by soaking in acetic acid reagent for 12 hours; then vacuum filtration was performed, followed by washing with ethanol and deionized water to obtain clean fullerene C. 60 Polymer powder. The obtained fullerene polymer powder was dried in a vacuum drying oven at 100 °C for 12 h, and then ground to obtain fullerene C for lithium-ion battery anode materials. 60 Polymer materials.

[0078] Elemental analysis of the obtained fullerene C60 polymer material showed that the fullerene C60 polymer material provided in this application includes fullerene C60 polymer and Mg2+ doped therein, with a molar ratio of Mg2+ to fullerene C60 of 0.6:1.

[0079] Based on the prepared fullerene C 60 The polymer material was ground with sodium alginate and Ketjen black in an 8:1:1 ratio. After uniform mixing, the resulting slurry was smoothly coated onto carbon-coated copper foil using a scraping method. After vacuum drying, the electrode sheets were cut to obtain electrode plates. The battery was assembled under an argon atmosphere with an oxygen content of less than 1 ppm and a water content of less than 1 ppm. The electrolyte was 1 mol / L. −1 Lithium bis(trifluoromethanesulfonyl)imide was dissolved in a mixed solution of 1,3-dioxolane-ethylene glycol dimethyl ether (volume ratio 1:1) and 2% lithium nitrate. The assembled lithium-ion half-cell was subjected to constant current charge-discharge performance testing at voltages ranging from 0.01 to 3 V. The results show that the fullerene C provided in this application… 60 Polymer materials at 0.1 A g −1At a current density of 745 mAh g, its initial reversible specific capacity is 745 mAh g. −1 The initial coulombic efficiency was 86.7%, and the reversible specific capacity after 100 cycles was 413 mAh g. −1 The cycle retention rate was 53.6%.

[0080] Example 3

[0081] It uses 99% pure alkaline earth metal magnesium powder and 99.5% pure fullerene C. 60 The powder was uniformly mixed in an inert atmosphere and then compressed into tablets. The tablets were then packed into quartz tubes 30 cm long and 1 cm in diameter, with a molar ratio of 8:1. The quartz tubes were then vacuum-sealed at a high temperature with an internal pressure of 30 Pa. The sealed quartz tubes were placed horizontally in a dual-temperature zone tube furnace, ensuring that the reactants were centered in the high-temperature zone at one end and in the low-temperature zone at the other. The high-temperature zone was set to 800 °C and the low-temperature zone to 450 °C, with a heating rate of 5 °C / min. −1 The reaction was carried out in air for 20 h to obtain the fullerene polymer Mg4C. 60 Crystals. Crystals grown on the tube wall were selected and analyzed using 1 mol L... −1 Most of the Mg element was removed by immersion in hydrochloric acid at 80°C for 8 hours; then vacuum filtration was performed, followed by washing with ethanol and deionized water to obtain clean fullerene C. 60 Polymer powder. The obtained fullerene polymer powder was dried in a vacuum drying oven at 100 °C for 12 h, and then ground to obtain fullerene C for lithium-ion battery anode materials. 60 Polymer materials.

[0082] Elemental analysis of the obtained fullerene C60 polymer material showed that the fullerene C60 polymer material provided in this application includes fullerene C60 polymer and Mg2+ doped therein, with a molar ratio of Mg2+ to fullerene C60 of 0.2:1.

[0083] Based on the prepared fullerene C 60 The polymer material was ground with sodium carboxymethyl cellulose and Ketjen black in an 8:1:1 ratio. After uniform mixing, the resulting slurry was smoothly coated onto carbon-coated copper foil using a scraping method. After vacuum drying, the electrode sheets were cut to obtain electrode plates. The battery was assembled under an argon atmosphere with an oxygen content of less than 1 ppm and a water content of less than 1 ppm. The electrolyte was 1 mol / L. −1Lithium hexafluorophosphate was dissolved in a mixed solution of diethyl carbonate-ethylene carbonate (volume ratio 1:1) and 10% fluoroethylene carbonate. The assembled lithium ion half battery was subjected to constant current charge-discharge performance test, and the test voltage was 0.01-3 V. The results show that the fullerene C 60 The polymer material has a first reversible specific capacity of 423 mAh g −1 at a current density of 0.1 A g −1 , a first coulombic efficiency of 95.5%, a reversible specific capacity of 287 mAh g −1 after 100 cycles, and a cycle retention rate of 67.8%.

[0084] The above-described embodiments only express the specific implementation of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the protection scope of the present application. It should be pointed out that for ordinary skilled persons in the art, without departing from the technical concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A fullerene polymer material, comprising a fullerene polymer and alkaline earth metal ions doped in the fullerene polymer; The molar ratio of the alkaline earth metal ions to fullerene molecules is 0.01 to 1:

1.

2. The fullerene polymer material according to claim 1, characterized in that, The alkaline earth metal ions are one or more of magnesium ions, calcium ions, strontium ions, and barium ions. Fullerene molecules are fullerene C 60 Fullerene C 70 Fullerene C 80 and fullerene C 82 One or more of them.

3. The fullerene polymer material according to claim 2, characterized in that, The molar ratio of alkaline earth metal ions to fullerene molecules is 0.1 to 0.8:

1.

4. The fullerene polymer material according to any one of claims 1 to 3, characterized in that, It has a layered structure.

5. A negative electrode material comprising a binder, a conductive agent, and the fullerene polymer material according to any one of claims 1 to 4.

6. The negative electrode material according to claim 5, characterized in that, The binder includes one or more of sodium carboxymethyl cellulose, sodium alginate, and polyvinylidene fluoride; The conductive agent includes one or more of Ketjen black, conductive carbon black, and carbon nanotubes. The mass ratio of the fullerene polymer material, binder, and conductive agent is 5~10:1:

1.

7. A negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector; The negative electrode active material layer includes the negative electrode material as described in claim 5 or 6.

8. A lithium-ion battery, comprising the negative electrode material of claim 5 or 6 or the negative electrode sheet of claim 7.

9. A method for preparing the fullerene polymer material according to any one of claims 1 to 4, comprising the following steps: a) Encapsulate alkaline earth metals and fullerene molecular crystals in a sealed container; b) The sealed container is heated to obtain a metal-doped fullerene polymer crystal material; c) The metal-doped fullerene polymer crystal material is acid-washed and dried to obtain the fullerene polymer material.

10. The preparation method according to claim 9, characterized in that, In step a), the sealed container is a quartz tube; The molar ratio of the alkaline earth metal to the fullerene molecular crystal is 4~40:1; After sealing, the pressure of the sealed container is 0.01 Pa to 100 Pa; In step b), the heating treatment is carried out in an air atmosphere at a temperature of 200℃ to 1000℃ for 1 hour to 60 hours, with a heating rate of 1 to 20℃ per minute. −1 ; In step c), the acidic reagent used for pickling is one or more of nitric acid, hydrochloric acid, sulfuric acid, and acetic acid; The pickling time is 2h to 20h.

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