Preparation Method and Application of a Class of Hard Carbon Anode Materials with High Specific Capacity

Abstract

The present invention belongs to the technical field of battery material synthesis, and discloses a preparation method and application of a hard carbon anode material with high specific capacity. The preparation method is to disperse citric acid, oxalyl diamide, and sucrose in a solvent in a certain proportion, in-situ polymerize and fully cure at a certain temperature, and then carbonize the precursor at high temperature under the protection of an inert gas. After natural cooling, the PCO-Su hard carbon anode material is obtained. The PCO-Su hard carbon anode material provided by the present invention has the characteristics of high specific capacity and stable electrochemical cycling. The reversible specific capacity for lithium storage is 227 mAh·g-1; the reversible specific capacity for sodium storage is as high as 422 mAh·g-1. After cycling 100 times at a current density of 50 mA·g-1, the capacity retention rate exceeds 95%. It is suitable for the anodes of commercial lithium and sodium ion batteries. The preparation method of the hard carbon anode material disclosed by the present invention is simple, easy to control, and low in cost, and has good application prospects.

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: Dispersing citric acid, oxalyl diamide, and sucrose in a solvent in a certain proportion, and reacting at a specified temperature for a certain period of 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: Carbonizing the precursor obtained in step S2 at high temperature under the protection of an inert gas, and then naturally cooling to obtain the high specific capacity hard carbon negative electrode material.

[0010] During the polymerization process, monomer citric acid and oxalyl diamide capture sucrose molecules regularly through strong O···H-O hydrogen bond interactions to form a hard carbon precursor in which a two-dimensional polymer is combined with sucrose. During the high-temperature carbonization process, the two-dimensional polymer induces the sucrose molecules to form an amorphous carbon with locally disordered structures. The locally disordered structures 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] Further, in S1, the molar ratio of citric acid to oxalyl diamide is 2:3; the molar ratio of citric acid to sucrose is 2:1.

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

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

[0014] Further, 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] Further, in S3, the high-temperature calcination temperature is 1200-1500 °C, preferably 1400 °C. The calcination atmosphere is helium, nitrogen, or argon, and the heat treatment time is 2-4 h, preferably 3 h.

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

[0017] Preferably, the composition components and mass percentage contents 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 by using two-dimensional polymers, precisely constructing abundant closed pores in hard carbon microscopically, achieving high specific capacity and long cycle stability of the anode materials for lithium-ion batteries and sodium-ion batteries, which is conducive to promoting the further commercialization process of lithium-ion batteries and sodium-ion batteries.

[0020] 2) The reversible specific capacity of the anode of the lithium-ion battery assembled with the hard carbon anode material provided by the present invention is 227 mAh·g -1 , and the reversible specific capacity of the anode of the sodium-ion battery assembled is as high as 422 mAh·g -1 . After cycling 100 times at a current density of 50 mA·g -1 , 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 anode material provided by the present invention uses sucrose, citric acid, and oxalyl diamine with wide sources 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 PCO-Su-1400-3 hard carbon obtained in Example 2;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0039] Figure 18 is the long-cycle stability graph of the sodium-ion battery obtained in Example 2 (current density: 50 mA·g -1 , electrolyte: 1.0 mol·L -1 sodium hexafluorophosphate dissolved in ethylene carbonate:dimethyl carbonate:ethyl methyl carbonate = 1:1:1, voltage window: 0 - 1.5 V). Detailed implementation mode

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

[0041] During the in-situ polymerization process, the carbonyl group in the two-dimensional polymer forms a strong O···H-O hydrogen bond with the hydroxyl group in sucrose, and then captures sucrose molecules regularly to form a precursor of PCO-Su hard carbon. The PCO-Su hard carbon precursor is carbonized at high temperature under the protection of inert gas to obtain PCO-Su hard carbon with high specific capacity.

[0042] Example 1:

[0043] In this example, a negative electrode material was synthesized and its lithium-ion battery and sodium-ion battery performances 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 as follows:

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

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

[0047] The counter electrode of the lithium-ion battery is a lithium metal 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 sodium metal 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, together with the corresponding electrolyte, negative electrode sheet, and other necessary battery components, such as a separator and a casing, etc., are assembled into a CR2032 type button battery. The charge-discharge capacity of the battery prepared in this example is tested: at room temperature, a Land CT2001A battery test system is used for constant current charge-discharge testing, and the test voltage range is 0 - 1.5V. Figure 2 is the constant current charge-discharge curve of the Li / / PCO-Su-1400-2 battery for the first two cycles, with a current density of 10 mA·g -1 , and the reversible specific capacity is 100 mAh·g -1 。 Figure 3 is the constant current charge-discharge curve of the Na / / PCO-Su-1400-2 battery for the first two cycles, with a current density of 10 mA·g -1 , and the reversible specific capacity is 382 mAh·g -1 。

[0050] Example 2:

[0051] In this example, a negative electrode material was synthesized and its performance in lithium-ion batteries and sodium-ion batteries was investigated. The negative electrode active material is the PCO-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.

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

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

[0054] The composition of the electrode sheet for preparing the PCO-Su-1400-3 hard carbon negative electrode material (calculated based on the mass fraction of the negative electrode material being 100%): 80% of PCO-Su-1400-3 hard carbon, 10% of conductive carbon black, and 10% of sodium carboxymethylcellulose.

[0055] The counter electrode of the lithium-ion battery is a lithium metal 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 sodium metal 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 were assembled with the corresponding electrolyte, negative electrode sheet, and other necessary battery components, such as a separator and a casing, etc., into a CR2032 type button battery. The charge and discharge capacity of the battery prepared in this example was tested: at room temperature, a Land CT2001A battery test system was used for constant current charge and discharge testing, and the test voltage range was 0 - 1.5 V. Figure 4 is the constant current charge and discharge curve of the Li / / PCO-Su-1400-3 battery for the first two cycles, and the current density is 10 mA·g -1 , and the reversible specific capacity is 227 mAh·g -1 . Figure 5 is the constant current charge and discharge curve of the Na / / PCO-Su-1400-3 battery for the first two cycles, and the current density is 10 mA·g -1 , and the reversible specific capacity is 422 mAh·g -1 , and the first cycle Coulomb efficiency is 84%. Figure 18 is the cycle performance curve of the sodium-ion battery electrode in Example 2, and the current density is 50 mA·g -1 . The test results show that: under the above test conditions, the capacity retention rate of the sample battery in Example 2 was 97.9% after 100 cycles, and the sample battery in Example 2 has excellent cycle stability.

[0058] Example 3:

[0059] In this example, a negative electrode material was synthesized and its performance in lithium-ion batteries and sodium-ion batteries was investigated. The negative electrode active material was the 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 as follows:

[0061] First, 1.71 g of sucrose (5.0 mmol) was added to a 50 mL mixed solvent of ethyl acetate and isopropyl alcohol with a volume ratio of 1:1, and ultrasonic dispersion was carried out for 20 min. Then, 1.92 g of citric acid (10.0 mmol) was added, and ultrasonic dispersion was carried out for 5 min. Finally, 1.32 g of oxalyl diamide (15.0 mmol) was added, and after ultrasonic dispersion for 10 min, in-situ polymerization was carried out at 70 °C for 6 h. After the reaction ended, curing was carried out at 100 °C for 12 h. The cured precursor was carbonized in an argon atmosphere, the carbonization temperature was 1400 °C, and the heating rate was 3 °C·min -1 , the carbonization time was 4 h, and after carbonization ended, it was naturally cooled.

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

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

[0064] The counter electrode of the sodium-ion battery was a sodium metal sheet; the solvent of the electrolyte was a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate with a volume ratio of 1:1:1; the electrolyte salt was sodium hexafluorophosphate, and the molar concentration in the electrolyte was 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 were assembled with the corresponding electrolyte, negative electrode sheet, and other necessary battery components, such as a separator and a casing, etc., into a CR2032 type button battery. The charge-discharge capacity of the battery prepared in this example was tested: at room temperature, a Land CT2001A battery test system was used for constant current charge-discharge testing, and the test voltage range was 0 - 1.5 V. Figure 6The first two cycles of constant current charge-discharge curves of the Li / / PCO-Su-1400-4 battery, with a current density of 10 mA·g -1 , and the reversible specific capacity is 171 mAh·g -1 . Figure 7 The first two cycles of constant current charge-discharge curves of the Na / / PCO-Su-1400-4 battery, with a current density of 10 mA·g -1 , and 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 performance in lithium-ion batteries and sodium-ion batteries was investigated respectively. The negative electrode active material was the Su-1400-3 hard carbon material obtained by directly carbonizing 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 as follows:

[0069] The directly purchased sucrose was carbonized under an argon atmosphere, the carbonization temperature was 1400 °C, the heating rate was 3 °C·min -1 , the carbonization time was 3 h, and after the carbonization was completed, it was cooled naturally.

[0070] The composition of the electrode sheet for preparing the Su-1400-3 hard carbon negative electrode material (calculated based on the mass fraction of the negative electrode material being 100%): 80% of Su-1400-3 hard carbon, 10% of conductive carbon black, and 10% of sodium carboxymethylcellulose.

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

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

[0073] The lithium foils of the lithium-ion batteries and sodium foils of the sodium-ion batteries prepared above, together with the corresponding electrolytes, negative electrode foils and other necessary battery components, such as separators and casings, etc., are assembled into CR2032 type button batteries. The charge-discharge capacity of the batteries prepared in this example is tested: at room temperature, a Land CT2001A battery test system is used for constant current charge-discharge tests, and the test voltage range is 0 - 1.5V. Figure 8 is the constant current charge-discharge curve of the first two cycles of the Li / / Su-1400-3 battery, and the current density is 10 mA·g -1 , and the reversible specific capacity is 101 mAh·g -1 . Figure 9 is the constant current charge-discharge curve of the first two cycles of the Na / / Su-1400-3 battery, and the current density is 10 mA·g -1 , and the reversible specific capacity is 215 mAh·g -1 .

[0074] Comparative Example 2:

[0075] In this comparative example, a negative electrode material was synthesized and its lithium-ion battery and sodium-ion battery performances were investigated. The negative electrode active material was the PTO-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.

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

[0077] First, 1.71 g of sucrose (5.0 mmol) was added to 50 mL of absolute ethanol and ultrasonically dispersed for 20 min. Then, 2.10 g of trimesic acid (10.0 mmol) was added and ultrasonically dispersed for 5 min. Finally, 1.32 g of oxalyl diamide (15.0 mmol) was added and ultrasonically dispersed for 10 min, and then in-situ polymerization was carried out at 70 °C for 6 h. After the reaction, it was cured at 100 °C for 12 h. The cured precursor was carbonized in an argon atmosphere, the carbonization temperature was 1400 °C, and the heating rate was 3 °C·min -1 , and the carbonization time was 3 h. After carbonization, it was naturally cooled.

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

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

[0080] The counter electrode of the sodium-ion battery is a sodium metal 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 separator and outer shell, etc., into a CR2032 type button battery. The charge-discharge capacity of the battery prepared in this example was tested: at room temperature, a Land CT2001A battery test system was used for constant current charge-discharge test, and the test voltage range was 0 - 1.5V. Figure 10 Figure 1 is the constant current charge-discharge curve of the Li / / PTO-Su-1400-3 battery for the first two cycles, and the current density is 10 mA·g -1 , and the reversible specific capacity is 134 mAh·g -1 . Figure 11 Figure 2 is the constant current charge-discharge curve of the Na / / PTO-Su-1400-3 battery for the first two cycles, and the current density is 10 mA·g -1 , and the reversible specific capacity is 175 mAh·g -1 .

[0082] Comparative Example 3:

[0083] In this comparative 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 the PCE-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.

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

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

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

[0087] The counter electrode of the lithium-ion battery is a lithium metal 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 sodium metal 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, together with the corresponding electrolyte, negative electrode sheet, and other necessary battery components, such as the separator and the casing, etc., are assembled into a CR2032 type button battery. The charge-discharge capacity of the battery prepared in this example is tested: at room temperature, a Land CT2001A battery test system is used for constant current charge-discharge testing, and the test voltage range is 0 - 1.5V. Figure 12 Figure 1 shows the first two cycles of constant current charge-discharge curves of the Li / / PCE-Su-1400-3 battery, with a current density of 10 mA·g -1 , and the reversible specific capacity is 125 mAh·g -1 。 Figure 13 Figure 2 shows the first two cycles of constant current charge-discharge curves of the Na / / PCE-Su-1400-3 battery, with a current density of 10 mA·g -1 , and the reversible specific capacity is 196 mAh·g -1 。

[0090] Comparative Example 4:

[0091] In this comparative example, a negative electrode material was synthesized and its performance in lithium-ion batteries and sodium-ion batteries was investigated. The negative electrode active material is the 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 as follows:

[0093] First, 0.90 g of glucose (5.0 mmol) was added to 50 mL of anhydrous ethanol and ultrasonically dispersed for 20 min. Then, 1.92 g of citric acid (10.0 mmol) was added and ultrasonically dispersed for 5 min. Finally, 1.32 g of oxalyl diamide (15.0 mmol) was added and ultrasonically dispersed for 10 min, followed by in-situ polymerization at 70 °C for 6 h. After the reaction, it was cured at 100 °C for 12 h. The cured precursor was carbonized under an argon atmosphere at a carbonization temperature of 1400 °C and a heating rate of 3 °C·min -1 , and the carbonization time was 3 h. After carbonization, it was cooled naturally.

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

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

[0096] The counter electrode of the sodium-ion battery was a sodium metal sheet; the solvent of the electrolyte was a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate with a volume ratio of 1:1:1; the electrolyte salt was sodium hexafluorophosphate, and the molar concentration in the electrolyte was 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 were assembled with the corresponding electrolyte, negative electrode sheet, and other necessary battery components, such as a separator and a casing, etc., into a CR2032 type button battery. The charge-discharge capacity of the battery prepared in this example was tested: at room temperature, a Land CT2001A battery test system was used for constant current charge-discharge testing, and the test voltage range was 0 - 1.5 V. Figure 14 Figure 1 shows the first two cycles of constant current charge-discharge curves for the Li / / PCO-Gl-1400-3 battery, with a current density of 10 mA·g -1 , and the reversible specific capacity was 148 mAh·g -1 . Figure 15 Figure 2 shows the first two cycles of constant current charge-discharge curves for the Na / / PCO-Gl-1400-3 battery, with a current density of 10 mA·g -1 , and the reversible specific capacity was 249 mAh·g -1 .

[0098] Comparative Example 5:

[0099] In this comparative example, a negative electrode material was synthesized and its performance in lithium-ion batteries and sodium-ion batteries was investigated. The negative electrode active material was the PCO-PI-1400-3 hard carbon negative electrode material, and the electrolyte system was 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 as follows:

[0101] First, 1.50 g of pitch was added to 50 mL of absolute ethanol and ultrasonically dispersed for 20 min. Then, 1.92 g of citric acid (10.0 mmol) was added and ultrasonically dispersed for 5 min. Finally, 1.32 g of oxalyl diamide (15.0 mmol) was added and ultrasonically dispersed for 10 min, followed by in-situ polymerization at 70 °C for 6 h. After the reaction, it was cured at 100 °C for 12 h. The cured precursor was carbonized in an argon atmosphere at a carbonization temperature of 1400 °C and a heating rate of 3 °C·min -1 , and the carbonization time was 3 h. After carbonization, it was cooled naturally.

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

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

[0104] The counter electrode of the sodium-ion battery was a sodium metal sheet; the solvent of the electrolyte was a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate with a volume ratio of 1:1:1; the electrolyte salt was sodium hexafluorophosphate, and the molar concentration in the electrolyte was 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 were assembled with the corresponding electrolyte, negative electrode sheet, and other necessary battery components, such as a separator and a casing, etc., into a CR2032 type button battery. The charge-discharge capacity of the battery prepared in this example was tested: at room temperature, a Land CT2001A battery test system was used for constant current charge-discharge testing, and the test voltage range was 0 - 1.5 V. Figure 16 Figure 2 shows the first two cycles of constant current charge-discharge curves of the Li / / PCO-PI-1400-3 battery, with a current density of 10 mA·g -1 , and the reversible specific capacity was 122 mAh·g -1 .Figure 17 It is the constant current charge-discharge curve of the Na / / PCO-PI-1400-3 battery for the first two cycles, and the current density is 10 mA·g -1 , and the reversible specific capacity is 224 mAh·g -1 .

[0106] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, 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 following steps are involved: S1: Disperse citric acid, oxalyl diamine and sucrose in a solvent in proportion, 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; 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; 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 polymers induce 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.

2. 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.

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

4. 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.

5. 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.

6. 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.

7. Use of a high specific capacity hard carbon negative electrode material prepared by the preparation method according to any one of claims 1 to 6 in a lithium ion battery or a sodium ion battery.

8. The use according to claim 7, 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 the high specific capacity hard carbon negative electrode material prepared according to any one of claims 1 to 6, 10% of conductive carbon black, and 10% of sodium carboxymethyl cellulose.

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