Preparation method and application of high-specific-capacity hard carbon negative electrode material

Abstract

The invention belongs to the technical field of battery material synthesis, and discloses a preparation method and application of a high-specific-capacity hard carbon negative electrode material. The preparation method comprises the following steps: dispersing citric acid, oxadiamide and cane sugar in a solvent in proportion, carrying out in-situ polymerization at a certain temperature and fully curing, carrying out high-temperature carbonization on a precursor under the protection of inert gas, and naturally cooling to obtain the PCO-Su hard carbon negative electrode material. The PCO-Su hard carbon negative electrode material provided by the invention has the characteristics of high specific capacity and stable electrochemical cycle, and the lithium storage reversible specific capacity is 227mAh. G <-1 >; the sodium storage reversible specific capacity reaches up to 422 mAh.g <-1 >, and the capacity retention rate exceeds 95% after 100 cycles under the current density of 50 mA. G <-1 >. The method is suitable for commercial lithium and sodium ion battery cathodes. The preparation method of the hard carbon negative electrode material disclosed by the invention is simple, easy to control and low in cost, and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of battery material synthesis, and specifically relates to a preparation method of a type of high specific capacity hard carbon material and its application in negative electrodes of lithium ion batteries and sodium ion batteries. Background Art

[0002] Negative electrode materials are crucial to the energy density and cycle life of secondary batteries, and are key factors in improving the overall performance of batteries and expanding their application range. Taking lithium-ion batteries as an example, graphite is widely used as a negative electrode material in the prior art. Due to its excellent reversible specific capacity, good conductivity and stable cycle performance, lithium-ion batteries have high energy density and long life, and are widely used in mobile communication equipment, electric vehicles and large-scale energy storage systems. However, in practical applications, graphite negative electrode materials have problems such as limited theoretical specific capacity, low first coulomb efficiency, insufficient structural stability and poor compatibility with electrolytes, making it difficult to simultaneously meet the requirements of high specific capacity, high stability and low cost. As an ideal substitute for lithium-ion batteries, sodium-ion batteries have the advantages of abundant resources, low cost and high safety. However, the radius of sodium ions is much larger than that of lithium ions, which makes it difficult for sodium ions to be efficiently embedded and extracted in graphite negative electrodes, limiting their storage capacity. Therefore, it is urgent to develop more excellent negative electrode materials to improve the comprehensive performance of secondary batteries.

[0003] Hard carbon is a highly disordered carbon material with large interlayer spacing, rich defects and difficult to graphitize at high temperature. It is considered to be a highly competitive commercial negative electrode material for lithium-ion batteries and sodium-ion batteries due to its good structural stability, suitable working potential, high first coulombic efficiency and reversible specific capacity. However, most of the commercialized hard carbon negative electrodes currently use biomass-based precursors. In addition to the regional and seasonal problems of raw materials, the electrochemical properties of biomass-based hard carbon, such as specific capacity and first coulombic efficiency, also need to be improved. Existing studies have shown that the influence of the microstructure of hard carbon on its electrochemical properties cannot be ignored. Among the capacity contributions of hard carbon, the platform area at low potential (≤0.1V) accounts for the main part, and the electrochemical behavior in this process mainly corresponds to the intercalation of active components in graphite microcrystals and the filling of closed pores. Therefore, it is crucial to develop high-performance hard carbon negative electrodes by regulating the microstructure of hard carbon for the large-scale promotion of lithium-ion batteries and sodium-ion batteries. Summary of the invention

[0004] The present invention aims to overcome the deficiencies of the prior art, provide a preparation method and application of a type of high specific capacity hard carbon negative electrode material, and solve the problems of low specific capacity and first coulombic efficiency of the prior art hard carbon negative electrode material.

[0005] The technical solution to solve the problem of the present invention is as follows:

[0006] The present invention provides a method for preparing a high specific capacity hard carbon negative electrode material, comprising the following steps:

[0007] S1 in-situ polymerization: citric acid, oxalyl diamine and sucrose are dispersed in a solvent in proportion and reacted at a specified temperature for a certain time;

[0008] S2 curing: curing the precursor obtained in step S1 at a specified temperature for a certain period of time;

[0009] S3 high temperature carbonization: the precursor obtained in step S2 is carbonized at high temperature under the protection of an inert gas, and then naturally cooled to obtain the high specific capacity hard carbon negative electrode material.

[0010] During the polymerization process, the monomers citric acid and oxalyl diamide capture sucrose molecules in a certain pattern through strong O···HO hydrogen bonds to form a hard carbon precursor composed of two-dimensional polymers and sucrose. During the high-temperature carbonization process, the two-dimensional polymer induces the sucrose molecules to form amorphous carbon with local structural disorder. The local disordered structure and abundant closed pores in the hard carbon provide more storage sites for active substances. This type of hard carbon negative electrode material exhibits high reversible specific capacity and long cycle stability in lithium-ion batteries and sodium-ion batteries.

[0011] Furthermore, in S1, the molar ratio of the citric acid to oxalyl diamide is 2:3; and the molar ratio of the citric acid to sucrose is 2:1.

[0012] Furthermore, the solvent is one or more of anhydrous methanol, anhydrous ethanol, isopropanol, acetone, dimethyl sulfoxide, and ethyl acetate, preferably anhydrous ethanol;

[0013] Furthermore, the polymerization reaction temperature in S1 is 50-120° C., preferably 60-90° C.; the heat treatment time is 3-12 h, preferably 4-8 h.

[0014] Furthermore, in S2, the curing temperature is 70-120° C., preferably 90-110° C.; the curing time is 10-24 h, preferably 10-14 h.

[0015] Furthermore, the high temperature calcination temperature in S3 is 1200-1500° C., preferably 1400° C. The calcination atmosphere is helium, nitrogen or argon, and the heat treatment time is 2-4 hours, preferably 3 hours.

[0016] The present invention also provides application of the hard carbon negative electrode material in lithium ion batteries and sodium ion batteries.

[0017] Preferably, the composition and mass percentage of the negative electrode material electrode sheet are: 80% of the hard carbon negative electrode material, 10% of conductive carbon black, and 10% of sodium carboxymethyl cellulose.

[0018] Advantages and beneficial effects of the present invention:

[0019] 1) The present invention provides a method for inducing local structural disorder during the carbonization of sucrose using a two-dimensional polymer, accurately constructing abundant closed pores in hard carbon at the microscopic level, achieving high specific capacity and long cycle stability of negative electrode materials for lithium-ion batteries and sodium-ion batteries, which is conducive to promoting the process of lithium-ion batteries and sodium-ion batteries further towards commercialization.

[0020] 2) The reversible specific capacity of the negative electrode of the lithium-ion battery assembled with the hard carbon negative electrode material provided by the present invention is 227 mAh·g -1 The reversible specific capacity of the negative electrode of the assembled sodium-ion battery is as high as 422 mAh g -1 , at 50mA·g -1 After 100 cycles at a current density of , the capacity retention rate exceeds 95%. The lithium ion battery and sodium ion battery provided by the present invention have high energy density.

[0021] 3) The hard carbon negative electrode material provided by the present invention uses sucrose, citric acid, and oxalyl diamide, which are widely available, as precursors, has low cost and simple preparation process, and can be applied to commercial lithium and sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the XRD pattern of the PCO-Su-1400-3 hard carbon obtained in Example 2;

[0023] Figure 2 The charge and discharge curve of the lithium ion battery obtained in Example 1 (current density: 10 mA g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0024] Figure 3 The sodium ion battery charge and discharge curve obtained in Example 1 (current density: 10 mA g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0025] Figure 4 The charge and discharge curve of the lithium ion battery obtained in Example 2 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0026] Figure 5 The sodium ion battery charge and discharge curve obtained in Example 2 (current density: 10 mA g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0027] Figure 6 The charge and discharge curve of the lithium ion battery obtained in Example 3 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0028] Figure 7 The sodium ion battery charge and discharge curve obtained in Example 3 (current density: 10 mA g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0029] Figure 8 The charge and discharge curve of the lithium-ion battery obtained in Example 1 (current density: 10 mA g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0030] Fig. 9 The charge and discharge curve of the sodium ion battery obtained in Example 1 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0031] Fig.10 The charge and discharge curve of the lithium-ion battery obtained in Example 2 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0032] Fig.11 The charge and discharge curve of the sodium ion battery obtained in Example 2 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L-1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0033] Fig.12 The charge and discharge curve of the lithium-ion battery obtained in Example 3 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0034] Fig.13 The charge and discharge curve of the sodium ion battery obtained in Example 3 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0035] Fig.14 The charge and discharge curve of the lithium-ion battery obtained in Example 4 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0036] Fig.15 The charge and discharge curve of the sodium ion battery obtained in Example 4 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0037] Fig.16 The charge and discharge curve of the lithium-ion battery obtained in Example 5 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Lithium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0038] Fig.17 The charge and discharge curve of the sodium ion battery obtained in Example 5 (current density: 10 mA·g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V);

[0039] Fig.18 The long cycle stability diagram of the sodium ion battery obtained in Example 2 (current density: 50 mA·g -1 、Electrolyte: 1.0mol·L -1 Sodium hexafluorophosphate is dissolved in ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 1:1:1, voltage window: 0-1.5V). DETAILED DESCRIPTION

[0040] The present invention is described in detail and completely below with reference to the accompanying drawings.

[0041] During the in-situ polymerization process, the carbonyl groups in the two-dimensional polymer formed strong O···HO hydrogen bonds with the hydroxyl groups in sucrose, and then captured the sucrose molecules in a certain pattern to form the precursor of PCO-Su hard carbon. The PCO-Su hard carbon precursor was carbonized at high temperature under the protection of inert gas to obtain PCO-Su hard carbon with high specific capacity.

[0042] Embodiment 1:

[0043] In this example, a negative electrode material was synthesized and its lithium ion battery and sodium ion battery performance were investigated. The negative electrode active material was PCO-Su-1400-2 hard carbon negative electrode material, and the electrolyte system was a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0044] The detailed synthesis method of the PCO-Su-1400-2 hard carbon negative electrode material is:

[0045] First, 1.71g sucrose (5.0mmol) was added to a mixed solvent of 50mL acetone and anhydrous methanol, the volume ratio of the mixed solvent was 1:1, and ultrasonic dispersion was performed for 20min. Then, 1.92g citric acid (10.0mmol) was added, ultrasonic dispersion was performed for 5min, and finally 1.32g oxalyl diamide (15.0mmol) was added, ultrasonic dispersion was performed for 10min, and in-situ polymerization was performed at 70℃ for 6h. After the reaction was completed, it was cured at 100℃ for 12h. The cured precursor was carbonized under argon atmosphere, the carbonization temperature was 1400℃, and the heating rate was 3℃·min -1 The carbonization time is 2 hours, and the temperature drops naturally after the carbonization is completed.

[0046] The electrode sheet composition of the PCO-Su-1400-2 hard carbon negative electrode material is prepared (based on the mass fraction of the negative electrode material as 100%): 80% PCO-Su-1400-2 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0047] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0048] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0049] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Figure 2 The constant current charge and discharge curves of the Li / / PCO-Su-1400-2 battery in the first two cycles, with a current density of 10 mA g -1 , reversible specific capacity is 100 mAh g -1 . Figure 3 The constant current charge and discharge curves of the Na / / PCO-Su-1400-2 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 382 mAh g -1 .

[0050] Embodiment 2:

[0051] In this example, a negative electrode material was synthesized and its lithium ion battery and sodium ion battery performance were investigated. The negative electrode active material was PCO-Su-1400-3 hard carbon negative electrode material, and the electrolyte system was a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0052] The detailed synthesis method of the PCO-Su-1400-3 hard carbon negative electrode material is:

[0053] First, 1.71g sucrose (5.0mmol) was added to 50mL anhydrous ethanol and ultrasonically dispersed for 20min. Then, 1.92g citric acid (10.0mmol) was added and ultrasonically dispersed for 5min. Finally, 1.32g oxalyl diamine (15.0mmol) was added and ultrasonically dispersed for 10min. Then, in-situ polymerization was carried out at 70℃ for 6h. After the reaction was completed, it was cured at 100℃ for 12h. The cured precursor was carbonized in an argon atmosphere at a carbonization temperature of 1400℃ and a heating rate of 3℃·min -1The carbonization time is 3 hours, and the temperature is naturally lowered after carbonization. The powder XRD results of PCO-Su-1400-3 hard carbon are as follows Figure 1 As shown, where 2θ (002) =23.81°, and the 002 crystal plane spacing calculated by the Bragg equation is 0.373nm, which is conducive to the embedding and extraction of active components during the charging and discharging process.

[0054] The electrode sheet composition of the PCO-Su-1400-3 hard carbon negative electrode material is prepared (based on the mass fraction of the negative electrode material as 100%): 80% PCO-Su-1400-3 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0055] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0056] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0057] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Figure 4 The constant current charge and discharge curves of the Li / / PCO-Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 227 mAh g -1 . Figure 5 The constant current charge and discharge curves of the Na / / PCO-Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 422mAh·g -1 , the first-cycle Coulomb efficiency is 84%. Fig.18 The cycle performance curve of the sodium ion battery electrode in Example 2, the current density is 50mA·g -1 The test results show that under the above test conditions, the capacity retention rate of the sample battery of Example 2 after 100 cycles is 97.9%, and the sample battery of Example 2 has excellent cycle stability.

[0058] Embodiment 3:

[0059] In this example, a negative electrode material was synthesized and its lithium ion battery and sodium ion battery performance were investigated. The negative electrode active material was PCO-Su-1400-4 hard carbon negative electrode material, and the electrolyte system was a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0060] The detailed synthesis method of the PCO-Su-1400-4 hard carbon negative electrode material is:

[0061] First, 1.71g sucrose (5.0mmol) was added to 50mL of a mixed solvent of ethyl acetate and isopropanol, with a volume ratio of 1:1, and ultrasonically dispersed for 20min. Then, 1.92g citric acid (10.0mmol) was added, ultrasonically dispersed for 5min, and finally 1.32g oxalyl diamine (15.0mmol) was added, ultrasonically dispersed for 10min, and then in-situ polymerized at 70°C for 6h. After the reaction was completed, it was cured at 100°C for 12h. The cured precursor was carbonized in an argon atmosphere, with a carbonization temperature of 1400°C and a heating rate of 3°C·min -1 The carbonization time is 4 hours, and the temperature drops naturally after the carbonization is completed.

[0062] The electrode sheet composition of the PCO-Su-1400-4 hard carbon negative electrode material is prepared (based on the mass fraction of the negative electrode material as 100%): 80% PCO-Su-1400-4 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0063] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0064] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0065] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Figure 6The constant current charge and discharge curves of the Li / / PCO-Su-1400-4 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 171 mAh g -1 . Figure 7 The constant current charge and discharge curves of the Na / / PCO-Su-1400-4 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 359 mAh g -1 .

[0066] Comparative Example 1:

[0067] In this comparative example, a negative electrode material was synthesized and its lithium-ion battery and sodium-ion battery performance were investigated respectively. The negative electrode active material was Su-1400-3 hard carbon material obtained by direct carbonization of sucrose at 1400°C, and the electrolyte system was a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.

[0068] The detailed synthesis method of the Su-1400-3 hard carbon material is:

[0069] The purchased sucrose was carbonized in an argon atmosphere at a temperature of 1400 °C and a heating rate of 3 °C min -1 The carbonization time is 3 hours, and the temperature drops naturally after the carbonization is completed.

[0070] The electrode sheet composition of the Su-1400-3 hard carbon negative electrode material is prepared (based on the mass fraction of the negative electrode material as 100%): 80% Su-1400-3 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0071] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0072] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0073] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Figure 8 The constant current charge and discharge curves of the Li / / Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 101 mAh g -1 . Fig. 9 The constant current charge and discharge curves of the Na / / Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 215 mAh g -1 .

[0074] Comparative Example 2:

[0075] In this comparative example, a negative electrode material is synthesized and its lithium ion battery and sodium ion battery performance are investigated. The negative electrode active material is PTO-Su-1400-3 hard carbon negative electrode material, and the electrolyte system is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0076] The detailed synthesis method of the PTO-Su-1400-3 hard carbon negative electrode material is:

[0077] First, 1.71g sucrose (5.0mmol) was added to 50mL anhydrous ethanol and ultrasonically dispersed for 20min. Then, 2.10g trimesic acid (10.0mmol) was added and ultrasonically dispersed for 5min. Finally, 1.32g oxalyl diamine (15.0mmol) was added and ultrasonically dispersed for 10min, and then in-situ polymerized at 70℃ for 6h. After the reaction was completed, it was cured at 100℃ for 12h. The cured precursor was carbonized in an argon atmosphere at a carbonization temperature of 1400℃ and a heating rate of 3℃·min -1 The carbonization time is 3 hours, and the temperature drops naturally after the carbonization is completed.

[0078] The electrode sheet composition of the prepared PTO-Su-1400-3 hard carbon negative electrode material (based on the mass fraction of the negative electrode material as 100%) is: 80% PTO-Su-1400-3 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0079] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0080] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0081] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Fig.10 The constant current charge and discharge curves of the Li / / PTO-Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 134 mAh g -1 . Fig.11 The constant current charge and discharge curves of the Na / / PTO-Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 175 mAh g -1 .

[0082] Comparative Example 3:

[0083] In this comparative example, a negative electrode material is synthesized and its lithium-ion battery and sodium-ion battery performance are investigated. The negative electrode active material is PCE-Su-1400-3 hard carbon negative electrode material, and the electrolyte system is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0084] The detailed synthesis method of the PCE-Su-1400-3 hard carbon negative electrode material is:

[0085] First, 1.71g sucrose (5.0mmol) was added to 50mL anhydrous ethanol and ultrasonically dispersed for 20min. Then, 1.92g citric acid (10.0mmol) was added and ultrasonically dispersed for 5min. Finally, 0.90g ethylenediamine (15.0mmol) was added and ultrasonically dispersed for 10min, and then in-situ polymerization was carried out at 70℃ for 6h. After the reaction was completed, it was cured at 100℃ for 12h. The cured precursor was carbonized in an argon atmosphere at a carbonization temperature of 1400℃ and a heating rate of 3℃·min -1 The carbonization time is 3 hours, and the temperature drops naturally after the carbonization is completed.

[0086] The electrode sheet composition of the PCE-Su-1400-3 hard carbon negative electrode material is prepared (based on the mass fraction of the negative electrode material as 100%): 80% PCE-Su-1400-3 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0087] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0088] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0089] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Fig.12 The constant current charge and discharge curves of the Li / / PCE-Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , reversible specific capacity is 125 mAh g -1 . Fig.13 The constant current charge and discharge curves of the Na / / PCE-Su-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 196 mAh g -1 .

[0090] Comparative Example 4:

[0091] In this comparative example, a negative electrode material is synthesized and its lithium-ion battery and sodium-ion battery performance are investigated. The negative electrode active material is PCO-Gl-1400-3 hard carbon negative electrode material, and the electrolyte system is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0092] The detailed synthesis method of the PCO-Gl-1400-3 hard carbon negative electrode material is:

[0093] First, add 0.90g glucose (5.0mmol) to 50mL anhydrous ethanol and ultrasonically disperse for 20min. Then add 1.92g citric acid (10.0mmol) and ultrasonically disperse for 5min. Finally, add 1.32g oxalyl diamine (15.0mmol), ultrasonically disperse for 10min, and then in-situ polymerize at 70℃ for 6h. After the reaction is completed, cure at 100℃ for 12h. The cured precursor is carbonized in an argon atmosphere at a carbonization temperature of 1400℃ and a heating rate of 3℃·min -1 The carbonization time is 3 hours, and the temperature drops naturally after the carbonization is completed.

[0094] The electrode sheet composition of the prepared PCO-Gl-1400-3 hard carbon negative electrode material (based on the mass fraction of the negative electrode material as 100%) is: 80% PCO-Gl-1400-3 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0095] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0096] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0097] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Fig.14 The constant current charge and discharge curves of the first two cycles of the Li / / PCO-Gl-1400-3 battery are shown in Figure 1. The current density is 10 mA g -1 , the reversible specific capacity is 148 mAh g -1 . Fig.15 The constant current charge and discharge curves of the Na / / PCO-Gl-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 249 mAh g -1 .

[0098] Comparative Example 5:

[0099] In this comparative example, a negative electrode material is synthesized and its lithium ion battery and sodium ion battery performance are investigated. The negative electrode active material is PCO-PI-1400-3 hard carbon negative electrode material, and the electrolyte system is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0100] The detailed synthesis method of the PCO-PI-1400-3 hard carbon negative electrode material is:

[0101] First, add 1.50g of asphalt to 50mL of anhydrous ethanol and ultrasonically disperse for 20min. Then add 1.92g of citric acid (10.0mmol) and ultrasonically disperse for 5min. Finally, add 1.32g of oxalyl diamine (15.0mmol), ultrasonically disperse for 10min, and then in-situ polymerize at 70℃ for 6h. After the reaction is completed, cure at 100℃ for 12h. The cured precursor is carbonized in an argon atmosphere at a carbonization temperature of 1400℃ and a heating rate of 3℃·min -1 The carbonization time is 3 hours, and the temperature drops naturally after the carbonization is completed.

[0102] The electrode sheet composition of the prepared PCO-PI-1400-3 hard carbon negative electrode material (based on the mass fraction of the negative electrode material as 100%) is: 80% PCO-PI-1400-3 hard carbon, 10% conductive carbon black, and 10% sodium carboxymethyl cellulose.

[0103] The counter electrode of the lithium-ion battery is a metal lithium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is lithium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0104] The counter electrode of the sodium ion battery is a metallic sodium sheet; the solvent of the electrolyte is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with a volume ratio of 1:1:1; the electrolyte salt is sodium hexafluorophosphate, and the molar concentration in the electrolyte is 1.0 mol·L -1 .

[0105] The lithium sheet of the lithium ion battery and the sodium sheet of the sodium ion battery prepared above are assembled with the corresponding electrolyte, negative electrode sheet and other necessary battery components, such as a diaphragm and a shell, into a CR2032 type button battery. The battery prepared in this embodiment is subjected to a charge and discharge capacity test: At room temperature, a constant current charge and discharge test is performed using a LandCT2001A battery test system, and the test voltage range is 0-1.5V. Fig.16 The constant current charge and discharge curves of the first two cycles of the Li / / PCO-PI-1400-3 battery are shown in Figure 1. The current density is 10 mA g -1 , the reversible specific capacity is 122 mAh g -1 . Fig.17 The constant current charge and discharge curves of the Na / / PCO-PI-1400-3 battery in the first two cycles, with a current density of 10 mA g -1 , the reversible specific capacity is 224 mAh g -1 .

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high specific capacity hard carbon negative electrode material, characterized in that: The two-dimensional polymer is used to induce sucrose molecules to form amorphous carbon with local disordered structure and rich closed pores during high-temperature carbonization. The structure provides a large number of storage sites for active components, including the following steps: S1: Disperse citric acid, oxalyl diamine and sucrose in a solvent according to a certain ratio, and react at 50-120°C for 3-12h to obtain a precursor; S2 cures the precursor at 70-120°C for 10-24h; S3: carbonizing the solidified precursor at 1200-1500° C. for 2-4 hours under the protection of an inert gas, and naturally cooling the precursor to obtain the high specific capacity hard carbon negative electrode material.

2. The method for preparing a high specific capacity hard carbon negative electrode material according to claim 1, characterized in that: The molar ratio of the citric acid to oxalyl diamide is 2:3; the molar ratio of the citric acid to sucrose is 2:

1.

3. The method for preparing a high specific capacity hard carbon negative electrode material according to claim 1, characterized in that: The solvent is one or more of anhydrous methanol, anhydrous ethanol, isopropanol, acetone, dimethyl sulfoxide and ethyl acetate.

4. The method for preparing a high specific capacity hard carbon negative electrode material according to claim 1, characterized in that: In S1, the reaction temperature is 60-90°C and the heat treatment time is 4-8h.

5. The method for preparing a high specific capacity hard carbon negative electrode material according to claim 1, characterized in that: The curing temperature in S2 is 90-110°C and the curing time is 10-14h.

6. The method for preparing a high specific capacity hard carbon negative electrode material according to claim 1, characterized in that: The inert gas in S3 is helium, nitrogen, argon or neon.

7. The method for preparing a high specific capacity hard carbon negative electrode material according to claim 1, characterized in that: The carbonization temperature in S3 is 1400°C and the carbonization time is 3h.

8. Use of a high specific capacity hard carbon negative electrode material according to any one of claims 1 to 7 in lithium ion batteries or sodium ion batteries.

9. The use according to claim 8, characterized in that: The components and mass percentage of the negative electrode sheet of a lithium ion battery or a sodium ion battery are: 80% of a high specific capacity hard carbon negative electrode material prepared according to any one of claims 1 to 7, 10% of conductive carbon black, and 10% of sodium carboxymethyl cellulose.

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