Hard carbon composite material and preparation method and application thereof
By constructing a nanoscale fiber network on the surface of hard carbon and then performing secondary coating with sodium alginate and high-temperature carbonization, the conductivity and stability issues of hard carbon materials were solved, achieving efficient fast charging and long cycle performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-04-03
AI Technical Summary
Hard carbon materials have poor electronic conductivity, resulting in low fast-charging performance, low initial coulombic efficiency, and insufficient cycle stability.
By constructing a nanoscale fiber network on the surface of hard carbon and then performing secondary coating with sodium alginate and high-temperature carbonization, a dense carbon coating layer is formed, which enhances conductivity and structural stability.
It significantly improves the initial coulombic efficiency, rate performance, and cycle stability of lithium-ion batteries, with an initial coulombic efficiency of 80-90% and a capacity retention of over 90% after 500 cycles at 25 °C.
Smart Images
Figure CN121790341A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a hard carbon composite material, its preparation method, and its application. Background Technology
[0002] Lithium-ion batteries, with their significant advantages such as high energy density, long cycle life, and no memory effect, have been widely used in many fields, including portable electronic devices, electric vehicles, and large-scale energy storage systems. As a core component of lithium-ion batteries, the performance of the anode material directly determines the overall electrochemical performance of the battery. Therefore, developing high-performance anode materials has become one of the current research hotspots and core directions in the field of lithium-ion batteries.
[0003] Among many anode materials, hard carbon is considered a highly promising next-generation lithium-ion battery anode material due to its outstanding characteristics such as large interlayer spacing, low lithium intercalation potential, wide availability of raw materials, and relatively simple preparation process. It has shown broad application prospects, especially in high-energy-density power batteries and energy storage batteries.
[0004] However, due to the open pores and disordered layer structure of hard carbon, its electronic conductivity is poor, which reduces its fast charging performance and first coulomb efficiency. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a hard carbon composite material and its preparation method. The hard carbon composite material has abundant reaction sites on its surface and exhibits high stability. When used as a negative electrode material for lithium-ion batteries, it can significantly improve the initial coulombic efficiency, rate performance, and cycle stability of lithium-ion batteries.
[0006] The present invention also provides the application of the hard carbon composite material in lithium-ion batteries, which, when used as a negative electrode active material for lithium-ion batteries, can significantly improve the initial coulombic efficiency, rate performance and cycle stability of lithium-ion batteries.
[0007] The present invention also provides a lithium-ion battery anode, wherein the lithium-ion battery anode is prepared using the hard carbon composite material described in the present invention as the active material.
[0008] The present invention also provides a lithium-ion battery, wherein the lithium-ion battery is assembled with the negative electrode of the lithium-ion battery as the negative electrode, and the initial coulombic efficiency of the lithium-ion battery is 80-90%, and the capacity retention rate at 25 °C and 500 cycles is above 90%.
[0009] The technical solution adopted in this invention is as follows:
[0010] A method for preparing a hard carbon composite material, the method comprising the following steps:
[0011] (1) Preparation of polyacrylonitrile fiber spinning solution;
[0012] (2) Disperse hard carbon into polyacrylonitrile fiber spinning solution and perform electrospinning to obtain PAN-coated hard carbon nanofiber membrane;
[0013] (3) Coat the surface of the PAN-coated hard carbon nanofiber membrane with an aqueous solution of sodium alginate and then dry it to obtain a sodium alginate / PAN-coated hard carbon nanofiber membrane.
[0014] (4) Under the protection of inert gas, the hard carbon nanofiber membrane coated with sodium alginate (SA) / PAN is heat-treated to obtain hard carbon composite material.
[0015] In step (1), the preparation method of the polyacrylonitrile fiber spinning solution is as follows: glycerol is stirred in N,N-dimethylformamide for at least 1 hour, and after the stirring is completed, polyacrylonitrile fiber is added and the stirring is continued until the emulsion becomes a transparent spinning solution; the mass ratio of glycerol, N,N-dimethylformamide and polyacrylonitrile fiber is 2~5:5~15:1~3, preferably 2.5:10:1.5.
[0016] In step (2), the mass ratio of hard carbon fiber to polyacrylonitrile fiber spinning solution is 5-10:1.
[0017] In step (3), the mass ratio of the PAN-coated hard carbon nanofiber membrane to sodium alginate is 100:1-3; the mass concentration of the sodium alginate aqueous solution is 1~5%, preferably 1.5%.
[0018] In step (3), the coating method is spraying, and the spraying rate is 1-5 mL / min.
[0019] In step (4), the heat treatment conditions are: 750-850 ℃ for 2.5-3.5 h.
[0020] The hard carbon composite material prepared by the method described in this invention has a nanoscale fiber network on the surface of hard carbon, which increases the reactive sites of hard carbon and improves the conductivity of hard carbon, thereby improving the rate performance. After secondary coating with sodium alginate, the carboxyl groups on the surface of sodium alginate form a dense hydrogen bond network with the hydroxyl groups on the first coating layer. After high-temperature carbonization, a stable carbon coating layer is formed, which improves the stability of the material.
[0021] The method for preparing hard carbon composite material provided by this invention achieves a comprehensive breakthrough in key battery performance through an innovative combination of primary coating with polyacrylonitrile nanofiber membrane, secondary coating with sodium alginate, and heat treatment curing, focusing on three core dimensions: material structure optimization, enhanced interfacial interaction, and improved charge transport efficiency.
[0022] Polyacrylonitrile nanofiber membranes achieve precise coating of hard carbon through electrospinning technology. The polyacrylonitrile nanofibers produced by electrospinning have a diameter at the nanoscale, and the resulting three-dimensional fiber network closely adheres to the surface of hard carbon, significantly increasing the contact area between hard carbon and the electrolyte. This provides more exposed active sites for lithium-ion insertion / extraction and reduces the spatial resistance of lithium-ion transport. After subsequent heat treatment, polyacrylonitrile forms carbon-based fibers with good conductivity. The three-dimensional interwoven fiber structure constructs a continuous conductive pathway on the surface of hard carbon, effectively reducing the contact resistance between hard carbon particles and accelerating the electron transport rate inside the electrode, providing core support for improved rate performance.
[0023] The stable carbon coating layer formed by secondary coating and heat treatment of sodium alginate further enhances the performance of hard carbon composite materials from both interfacial interaction and structural protection aspects. The carboxyl groups on the surface of sodium alginate molecules interact with the hydroxyl groups on the surface of the primary coating layer, polyacrylonitrile nanofiber membrane, forming a uniform and dense hydrogen bond network. After high-temperature carbonization, this network is transformed into a stable carbon coating layer, which not only tightly wraps the hard carbon particles but also fills the micropores that may exist in the primary coating, forming a multi-layered protective structure of hard carbon-nanofiber network-dense carbon layer. This structure can effectively block the direct contact between the electrolyte and the hard carbon core, reduce the excessive growth of SEI film caused by electrolyte decomposition, and reduce irreversible capacity loss. At the same time, the coating layer on the surface of hard carbon has good mechanical toughness, which can buffer the volume expansion of hard carbon during charge and discharge, prevent the electrode structure from pulverizing and falling off, and significantly improve the cycle stability of the material.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] The hard carbon composite material provided by this invention, as a negative electrode active material for lithium-ion batteries, can improve the following performance characteristics of lithium-ion batteries:
[0026] 1) Significantly improved first-time coulombic efficiency: The dense secondary carbon coating layer inhibits the disordered growth of the SEI film and reduces the irreversible consumption of lithium ions during the first charge and discharge process; at the same time, the primary coating nanofiber network improves the reactivity and conductivity, allowing lithium ion insertion / extraction to be more complete, which together reduces the capacity loss during the first charge and discharge process and significantly improves the first-time coulombic efficiency.
[0027] 2) Continuous optimization of rate performance: The conductive network and abundant active sites constructed by the first coating shorten the transport path of lithium ions and electrons and improve the transport rate; the dense structure of the second coating does not destroy the ion transport channel, but reduces the transport resistance through structural optimization, so that the material can still maintain efficient reaction kinetics in high-rate charge and discharge scenarios, and the rate performance is better than that of traditional hard carbon materials.
[0028] 3) Significantly enhanced cycle stability: The multi-layered coating structure of the hard carbon composite material ensures the integrity of the material structure from both mechanical support and interface protection aspects. This suppresses the volume expansion of hard carbon and reduces the loss of active materials and the continuous occurrence of side reactions. As a result, the capacity decay rate is significantly reduced during long-term charge-discharge cycles, and the cycle stability is fundamentally improved. Attached Figure Description
[0029] Figure 1 This data represents the capacity retention rate of lithium-ion batteries prepared using the hard carbon material in the various embodiments and comparative examples as the negative electrode active material at different charge-discharge rates. Detailed Implementation
[0030] The present invention will now be described in detail with reference to the embodiments.
[0031] The hard carbon used in each embodiment and comparative example is from Kuraray Corporation, Japan.
[0032] The polyacrylonitrile fiber was sourced from Sinopec Anqing Branch.
[0033] The conditions for electrospinning are: voltage difference of 15±1kV, rotation speed controlled at 200~600 rpm, and spinning feed rate of 0.5~2.5mL / h.
[0034] Example 1
[0035] A method for preparing a hard carbon composite material includes the following steps:
[0036] (1) Stir glycerol in DMF solvent for 1 hour, then add polyacrylonitrile fiber and continue stirring until the emulsion becomes a transparent spinning solution to obtain polyacrylonitrile fiber spinning solution; wherein the mass ratio of glycerol, DMF and polyacrylonitrile fiber is 2.5:10:1.5.
[0037] (2) Hard carbon and polyacrylonitrile fiber spinning solution are subjected to strong magnetic stirring and ultrasonic treatment to uniformly disperse hard carbon particles in the spinning solution, and then electrospinning is performed to obtain PAN-coated hard carbon nanofiber membrane; wherein the mass ratio of hard carbon to polyacrylonitrile fiber spinning solution is controlled at 10:1.
[0038] (3) Sodium alginate was prepared into an aqueous solution with a concentration of 1.5 wt%. Then, while stirring, the sodium alginate solution was sprayed onto the PAN-coated hard carbon nanofiber membrane. The spraying rate was controlled at 4 mL / min. Then, it was transferred to a forced-air drying oven and dried for 10 h to obtain a sodium alginate / PAN-coated hard carbon nanofiber membrane. The mass ratio of the PAN-coated hard carbon nanofiber membrane to sodium alginate was 100:1.5.
[0039] (4) The sodium alginate / PAN-coated hard carbon nanofiber membrane was transferred to a horizontal tube furnace and heat-treated at 800°C for 3 hours under nitrogen protection. After the treatment, it was cooled to room temperature to obtain the final hard carbon composite material.
[0040] Example 2
[0041] A method for preparing a hard carbon composite material includes the following steps:
[0042] (1) Stir glycerol in DMF solvent for 1 hour, then add polyacrylonitrile fiber and continue stirring until the emulsion becomes a transparent spinning solution to obtain polyacrylonitrile fiber spinning solution; wherein the mass ratio of glycerol, DMF and polyacrylonitrile fiber is 2.5:10:1.5;
[0043] (2) Hard carbon and polyacrylonitrile fiber spinning solution are subjected to strong magnetic stirring and ultrasonic treatment to uniformly disperse hard carbon particles in the spinning solution, and then electrospinning is performed to obtain PAN-coated hard carbon nanofiber membrane; wherein the mass ratio of hard carbon to polyacrylonitrile fiber spinning solution is controlled at 8:1.
[0044] (3) Sodium alginate was prepared into a 1.5 wt% deionized aqueous solution. Then, while stirring, the sodium alginate solution was sprayed onto the PAN-coated hard carbon nanofiber membrane. The spraying rate was controlled at 4 mL / min. Then, it was transferred to a forced-air drying oven and dried for 10 h to obtain a sodium alginate / PAN-coated hard carbon nanofiber membrane. The mass ratio of the PAN-coated hard carbon nanofiber membrane to sodium alginate was 100:1.5.
[0045] (4) The sodium alginate / PAN-coated hard carbon nanofiber membrane was transferred to a horizontal tube furnace and heat-treated at 800°C for 3 hours under nitrogen protection. After the treatment, it was cooled to room temperature to obtain the final hard carbon composite material.
[0046] Example 3
[0047] A method for preparing a hard carbon composite material includes the following steps:
[0048] (1) Stir glycerol in DMF solvent for 1 hour, then add polyacrylonitrile fiber and continue stirring until the emulsion becomes a transparent spinning solution to obtain polyacrylonitrile fiber spinning solution; wherein the mass ratio of glycerol, DMF and polyacrylonitrile fiber is 2.5:10:1.5;
[0049] (2) Hard carbon and polyacrylonitrile fiber spinning solution are subjected to strong magnetic stirring and ultrasonic treatment to uniformly disperse hard carbon particles in the spinning solution, and then electrospinning is performed to obtain PAN-coated hard carbon nanofiber membrane; wherein the mass ratio of hard carbon to polyacrylonitrile fiber spinning solution is controlled at 10:1.
[0050] (3) Sodium alginate was prepared into an aqueous solution with a concentration of 1.5 wt%. Then, while stirring, the sodium alginate solution was sprayed onto the PAN-coated hard carbon nanofiber membrane. The spraying rate was controlled at 4 mL / min. Then, it was transferred to a forced-air drying oven and dried for 10 h to obtain a sodium alginate / PAN-coated hard carbon nanofiber membrane. The mass ratio of the PAN-coated hard carbon nanofiber membrane to sodium alginate was 100:3.
[0051] (4) The sodium alginate / PAN-coated hard carbon nanofiber membrane was transferred to a horizontal tube furnace and heat-treated at 800°C for 3 hours under nitrogen protection. After the treatment, it was cooled to room temperature to obtain the final hard carbon composite material.
[0052] Comparative Example 1
[0053] A method for preparing a hard carbon material includes the following steps: under nitrogen protection, the hard carbon is heat-treated at 800°C for 3 hours, and then cooled to room temperature.
[0054] Comparative Example 2
[0055] A method for preparing a hard carbon composite material is the same as in Example 1, except that step (3) is omitted.
[0056] Application examples
[0057] The hard carbon materials prepared in each embodiment and comparative example were mixed with CNT, CMC and PAA in a mass percentage of 94%:3%:1%:2% to form a negative electrode slurry, which was then coated onto copper foil to form a negative electrode sheet. Lithium iron phosphate was mixed with SP, CNT and PVDF in a mass percentage of 94%:3%:0.7%:2.3% to form a positive electrode slurry, which was then coated onto aluminum foil to form a positive electrode sheet. The mixture was then assembled into a 2Ah soft-pack battery.
[0058] The initial coulombic efficiency, capacity retention after 500 cycles at 25°C, and capacity retention at different charge / discharge rates of each pouch cell were tested. The results are shown in Tables 1 and 2. Figure 1 As shown.
[0059] Table 1. Initial coulombic efficiency and capacity retention at 25°C and 500 cycles.
[0060]
[0061] Table 2 Capacity retention data at different charge / discharge rates
[0062]
[0063] From Tables 1 and 2 Figure 1As can be seen, the lithium-ion battery prepared using the hard carbon material in each embodiment as the negative electrode active material has an initial coulombic efficiency of 80-90%, a capacity retention rate of over 90% after 500 cycles at 25 °C, and a capacity retention rate of over 87% after charge and discharge at different rates.
[0064] The lithium-ion batteries prepared using hard carbon materials as negative electrode active materials in Comparative Examples 1 and 2 showed significantly inferior initial coulombic efficiency, capacity retention at 25 °C and 500 cycles, and capacity retention after charge-discharge at different rates compared to the embodiments.
[0065] It is evident that the hard carbon composite material provided by this invention can be used as a negative electrode material for lithium-ion batteries, significantly improving the initial coulombic efficiency, rate performance, and cycle stability of lithium-ion batteries.
[0066] The above detailed description of a hard carbon composite material, its preparation method, and its application, with reference to the embodiments, is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.
Claims
1. A method for preparing a hard carbon composite material, characterized in that, The preparation method includes the following steps: (1) Preparation of polyacrylonitrile fiber spinning solution; (2) Disperse hard carbon into polyacrylonitrile fiber spinning solution and perform electrospinning to obtain PAN-coated hard carbon nanofiber membrane; (3) Coat the surface of the PAN-coated hard carbon nanofiber membrane with an aqueous solution of sodium alginate and then dry it to obtain a sodium alginate / PAN-coated hard carbon nanofiber membrane. (4) Under inert gas protection, the hard carbon nanofiber membrane coated with sodium alginate / PAN was heat-treated to obtain a hard carbon composite material.
2. The preparation method according to claim 1, characterized in that, In step (1), the preparation method of the polyacrylonitrile fiber spinning solution is as follows: glycerol is stirred in N,N-dimethylformamide for at least 1 hour, and after the end, polyacrylonitrile fiber is added and stirred continuously until the emulsion becomes a transparent spinning solution; the mass ratio of glycerol, N,N-dimethylformamide and polyacrylonitrile fiber is 2~5:5~15:1~3.
3. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of hard carbon fiber to polyacrylonitrile fiber spinning solution is 5-10:
1.
4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of PAN-coated hard carbon nanofiber membrane to sodium alginate is 100:1-3; the mass concentration of the sodium alginate aqueous solution is 1-5%.
5. The preparation method according to claim 1, characterized in that, In step (3), the coating method is spraying, and the spraying rate is 1-5 mL / min.
6. The preparation method according to claim 1, characterized in that, In step (4), the heat treatment conditions are: 750-850 ℃ for 2.5-3.5 h.
7. The hard carbon composite material prepared by the preparation method according to any one of claims 1-6.
8. The application of the hard carbon composite material as described in claim 7 in lithium-ion batteries.
9. A lithium-ion battery negative electrode, characterized in that, The lithium-ion battery anode is prepared using the hard carbon composite material described in claim 7 as the active material.
10. A lithium-ion battery, characterized in that, The lithium-ion battery is assembled using the lithium-ion battery negative electrode as described in claim 9 as the negative electrode.