Lithium / sodium ion battery negative electrode material and preparation method thereof

Abstract

This invention belongs to the field of battery materials technology. It provides a lithium / sodium-ion battery anode material and its preparation method. Melamine and formaldehyde are used as polymerization monomers, and hydrochloric acid is used as a catalyst. Melamine resin microsphere samples are prepared in a mixed system of ethanol and water. A suitable amount of the sample is carbonized at a temperature of 650-1000℃ to form hard carbon powder. The treated hard carbon powder is then composited with a high-molecular organic material, heat-treated, and sieved to obtain the hard carbon anode material. The battery prepared using the hard carbon anode material of this invention has an initial reversible specific capacity of over 320 mAh / g and an initial coulombic efficiency of over 88%.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to lithium / sodium-ion battery anode materials and their preparation methods. Background Technology

[0002] In the wave of new energy technologies, lithium-ion and sodium-ion batteries, as two core forces in the field of electrochemical energy storage, are driving innovation in electric vehicles, energy storage systems, and portable electronic devices at an unprecedented pace. Lithium-ion batteries, with their high energy density, long cycle life, and environmentally friendly characteristics, have become the mainstream power source for electric vehicles and high-end electronic devices, while sodium-ion batteries, with their abundant raw materials and low cost, are considered an ideal choice for large-scale energy storage systems. However, as market demands for battery performance continue to increase, especially the growing need for low-temperature performance and fast-charging performance, traditional anode materials are finding it increasingly difficult to meet these stringent requirements.

[0003] Melamine resin, as a thermosetting polymer, has demonstrated remarkable potential in the preparation of lithium / sodium-ion battery anode materials due to its unique chemical structure and physical properties. Firstly, melamine resin can be transformed into carbon materials with abundant pores and high specific surface area through pyrolysis. These characteristics provide more active sites and more efficient transport pathways for the insertion and extraction of lithium / sodium ions, thus significantly improving the battery's specific capacity and cycle stability. Secondly, nitrogen in melamine resin can be in-situ doped into the carbon framework during carbonization, forming nitrogen-doped carbon materials. This material not only improves the electronic conductivity of the anode material but also optimizes the storage performance of lithium / sodium ions, enabling the battery to charge and discharge rapidly under fast-charging conditions without sacrificing excessive capacity and cycle stability. Most importantly, melamine resin-based anode materials maintain good electrochemical activity at low temperatures, effectively solving the problem of the sharp performance decline of traditional anode materials at low temperatures. This is of great significance for promoting the development of fast charging and low-temperature application technologies for electric vehicles and portable electronic devices. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a negative electrode material for lithium / sodium-ion batteries and a method for preparing the same. To achieve the above-mentioned objective, this invention provides the following technical solution.

[0005] This invention provides a lithium / sodium-ion battery anode material and its preparation method, comprising the following steps: (1) Add a certain amount of anhydrous ethanol to deionized water, heat it to 60-80℃ in a container, and then stir the mixture at a speed of 600-1000 r / min for 0.5-2 h to obtain a colorless and transparent solution; (2) Weigh a certain amount of melamine and disperse it in the solution until it becomes a colorless and transparent solution. After 0.5 h, add a certain amount of formaldehyde solution and disperse for another 0.5 h. Then add 0.1 mol / L hydrochloric acid and continue the reaction for 2-3 h to obtain a milky white turbid liquid. (3) The turbid liquid was centrifuged, washed three times with water and ethanol, and dried in a vacuum drying oven at 60°C for 10 hours to obtain melamine resin. (4) Melamine resin is subjected to high-temperature pretreatment in a protective atmosphere to obtain hard carbon powder; (5) The dried hard carbon powder and organic carbon source are heat-treated to obtain a single-layer coated hard carbon anode material, which is then sieved to obtain the hard carbon anode material.

[0006] Preferably, the mass ratio of deionized water to anhydrous ethanol in step 1) is 20:1-5:1.

[0007] Preferably, the mass ratio of the colorless transparent solution to melamine in step 2) is 100:1-25:1; and the mass ratio of melamine to formaldehyde solution is 1:2-1:5.

[0008] Preferably, the high-temperature pretreatment in step 4) is carried out at a temperature of 650~1000℃ for a time of 120~240min.

[0009] Preferably, the protective atmosphere in step 4) is nitrogen or argon.

[0010] Preferably, the organic carbon source in step 5) is one or more of high molecular organic materials such as PVA, PEO, and PVP; the mass ratio of the hard carbon powder to the organic carbon source is 97:3-80:20; and the heat treatment temperature is 900~1600℃ and the time is 2~3h.

[0011] The present invention also provides a hard carbon anode material prepared by the preparation method described above, wherein the median particle size D50 of the hard carbon anode material is 5-8 μm, the initial reversible specific capacity is ≥320 mAh / g, and the initial coulombic efficiency is ≥88%.

[0012] The beneficial effects of this invention include the following: 1) In this invention, melamine resin microspheres were synthesized in a mixed system of ethanol and water, using melamine and formaldehyde as monomers and hydrochloric acid as catalyst, under conditions without surfactants or templates. The preparation method is simple and the reaction conditions are mild. 2) This invention uses melamine resin as raw material to prepare a hard carbon anode material that can be applied to lithium / sodium ion batteries. The prepared anode material has a special morphology and has the advantages of stable structure, excellent electrochemical performance, good cycle performance and high specific capacity, making it very suitable as a lithium / sodium ion battery anode material. 3) The method of this invention solves the problem of large specific surface area and low initial coulombic efficiency of hard carbon anode materials through high-temperature graphitization pretreatment and single-layer carbon coating. The reversible capacity of the battery prepared by the hard carbon anode material of this invention exceeds 320 mAh / g, and the initial coulombic efficiency is above 88%. Attached Figure Description

[0013] Figure 1 This is a charge-discharge curve diagram of the first cycle of Embodiment 1 of the present invention. Detailed Implementation

[0014] The technical solution of the present invention and its beneficial effects will be further explained below with reference to the embodiments.

[0015] Implementation Example 1: Add 15 ml of anhydrous ethanol to 90 ml of deionized water and disperse at 70 °C and 800 rpm for 1 h. Weigh 2 g of melamine and disperse it in the solution until a colorless and transparent solution is obtained. After 30 min, add 4 ml of formaldehyde solution and disperse for another 30 min. Then add 1 ml of hydrochloric acid (0.1 mol / L) and continue the reaction for 2.5 h to obtain a milky white turbid liquid. Centrifuge the turbid liquid, wash it three times alternately with water and ethanol, and dry it in a vacuum drying oven at 60 °C for 10 h to obtain melamine resin powder. The melamine resin powder is carbonized in a N2 atmosphere by heating the material to 700 °C at a heating rate of 3 °C / min. The sieved hard carbon powder was poured into a PVA solution at a mass ratio of 95:5. The mixture was stirred at 250 rpm for 5 hours to coat the surface of the hard carbon particles with PVA. The particles were then filtered and dried to obtain hard carbon particles with PVA adsorbed on their surface. The hard carbon particles were then placed in a tubular furnace and heat-treated at 100°C for 1 hour under an inert atmosphere, followed by heat treatment at 900°C for 1 hour. The mixture was then passed through a 350-mesh sieve to obtain the hard carbon anode material.

[0016] Implementation Example 2: Add 15 ml of anhydrous ethanol to 90 ml of deionized water and disperse by stirring at 800 rpm for 1 h at 70 °C. Weigh 2 g of melamine and disperse it in the solution until a colorless and transparent solution is obtained. After 30 min, add 4 ml of formaldehyde solution and disperse for another 30 min. Then add 1 ml of hydrochloric acid (0.1 mol / L) and continue the reaction for 2.5 h to obtain a milky white turbid liquid. Centrifuge the turbid liquid, wash it three times alternately with water and ethanol, and dry it in a vacuum drying oven at 60 °C for 10 h to obtain melamine resin powder. The melamine resin powder is carbonized in a N2 atmosphere by heating the material to 800 °C at a heating rate of 3 °C / min. The sieved hard carbon powder was poured into a PVA solution at a mass ratio of 95:5. The mixture was stirred at 250 rpm for 5 hours to coat the surface of the hard carbon particles with PVA. The particles were then filtered and dried to obtain hard carbon particles with PVA adsorbed on their surface. The hard carbon particles were then placed in a tubular furnace and heat-treated at 100°C for 1 hour under an inert atmosphere, followed by heat treatment at 900°C for 1 hour. The mixture was then passed through a 350-mesh sieve to obtain the hard carbon anode material.

[0017] Example 3: Add 15 ml of anhydrous ethanol to 90 ml of deionized water and disperse at 70 °C and 800 rpm for 1 h. Weigh 2 g of melamine and disperse it in the solution until a colorless and transparent solution is obtained. After 30 min, add 4 ml of formaldehyde solution and disperse for another 30 min. Then add 1 ml of hydrochloric acid (0.1 mol / L) and continue the reaction for 2.5 h to obtain a milky white turbid liquid. Centrifuge the turbid liquid, wash it three times alternately with water and ethanol, and dry it in a vacuum drying oven at 60 °C for 10 h to obtain melamine resin powder. The melamine resin powder is carbonized in a N2 atmosphere by heating the material to 700 °C at a heating rate of 3 °C / min. The sieved hard carbon powder was poured into a PVA solution at a mass ratio of 95:5. The mixture was stirred at 250 rpm for 5 hours to coat the surface of the hard carbon particles with PVA. The particles were then filtered and dried to obtain hard carbon particles with PVA adsorbed on their surface. The hard carbon particles were then placed in a tubular furnace and heat-treated at 100°C for 1 hour under an inert atmosphere, followed by heat treatment at 900°C for 1 hour. The mixture was then passed through a 350-mesh sieve to obtain the hard carbon anode material.

[0018] Comparative example: Add 15 ml of anhydrous ethanol to 90 ml of deionized water and disperse by stirring at 800 rpm for 1 h at 70 °C. Weigh 2 g of melamine and disperse it in the solution until a colorless and transparent solution is obtained. After 30 min, add 4 ml of formaldehyde solution and disperse for another 30 min. Then add 1 ml of hydrochloric acid (0.1 mol / L) and continue the reaction for 2.5 h to obtain a milky white turbid liquid. Centrifuge the turbid liquid, wash it three times alternately with water and ethanol, and dry it in a vacuum drying oven at 60 °C for 10 h to obtain melamine resin powder. The melamine resin powder is carbonized in a N2 atmosphere by heating the material to 800 °C at a heating rate of 3 °C / min to obtain hard carbon powder, which is then passed through a 350-mesh sieve to obtain hard carbon anode material.

[0019] The performance parameters of the hard carbon anode materials prepared in Examples 1-3 and the comparative examples were measured, and the results are shown in Table 1.

[0020] Table 1 Performance parameters of the hard carbon anode materials prepared in Examples 1-3 and the comparative examples in sodium-ion batteries. project Example 1 Example 2 Example 3 Comparative Example D50(μm) 6.7 5.2 5.8 7.6 First reversible specific capacity (mAh / g) 322.1 325.3 326.9 286.8 First-time Coulomb efficiency (%) 90.2 89.2 88.6 80.6 The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent variations and improvements made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A lithium / sodium-ion battery anode material and its preparation method, characterized in that, It includes the following steps: (1) Add a certain amount of anhydrous ethanol to deionized water, heat it to 60-80℃ in a container, and then stir the mixture at a speed of 600-1000 r / min for 0.5-2 h to obtain a colorless and transparent solution; (2) Weigh a certain amount of melamine and disperse it in the solution until it becomes a colorless and transparent solution. After 0.5 h, add a certain amount of formaldehyde solution and disperse for another 0.5 h. Then add 0.1 mol / L hydrochloric acid and continue the reaction for 2-3 h to obtain a milky white turbid liquid; (3) The turbid liquid was centrifuged, washed three times with alternating water and ethanol, and dried in a vacuum drying oven at 60°C for 10 hours to obtain melamine resin; (4) Melamine resin is subjected to high-temperature pretreatment in a protective atmosphere to obtain hard carbon powder; (5) The dried hard carbon powder and organic carbon source are heat-treated to obtain a single-layer coated hard carbon material, which is then sieved to obtain a hard carbon anode material.

2. The preparation method according to claim 1, characterized in that, Step 1) The mass ratio between deionized water and anhydrous ethanol is 20:1-5:

1.

3. The preparation method according to claim 1, characterized in that, Step 2) The mass ratio between the colorless transparent solution and melamine is 100:1-25:1; the mass ratio between melamine and formaldehyde solution is 1:2-1:

5.

4. The preparation method according to claim 1, characterized in that, Step 4) The high-temperature pretreatment is carried out at a temperature of 650~1000℃ for a time of 120~240min.

5. The preparation method according to claim 1, characterized in that, Step 4) The protective atmosphere is nitrogen or argon.

6. The preparation method according to claim 1, characterized in that, Step 5) The organic carbon source is one or more of the high molecular organic materials such as PVA, PEO, and PVP; the mass ratio of the hard carbon powder to the organic carbon source is 97:3-80:20; the heat treatment temperature is 900~1600℃ and the time is 2~3h.

7. The hard carbon anode material prepared by the method according to claim 1, characterized in that, The median particle size D50 of the hard carbon anode material is 5-8 μm, the initial reversible specific capacity is ≥320 mAh / g, and the initial coulombic efficiency is ≥88%.

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