Manufacturing method for graphite for electrode material, electrode material having the same and lithium-ion battery having the same

Abstract

The present invention relates to a method for manufacturing a graphite negative electrode material for a lithium secondary battery, a graphite negative electrode material for a lithium secondary battery comprising said graphite, and a lithium secondary battery comprising said graphite. The present invention provides a graphite negative electrode material for a lithium secondary battery in which spherical graphite with a hollow structure exhibits excellent electrical conductivity and reduces the diffusion distance of lithium ions, thereby maintaining stable performance even during rapid charging and discharging.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a graphite negative electrode material for a lithium secondary battery, a graphite negative electrode material for a lithium secondary battery comprising said graphite, and a lithium secondary battery comprising said graphite. The present invention provides a graphite negative electrode material for a lithium secondary battery in which spherical graphite with a hollow structure exhibits excellent electrical conductivity and reduces the diffusion distance of lithium ions, thereby maintaining stable performance even during rapid charging and discharging.

[0002] The present invention was devised (conceived) as a result of the research on "Development of eco-friendly recycled cathode materials for improving the performance and stability of lithium-ion batteries" of the Phase 3 Industry-Academic Cooperation Leading University Development Project (LINC 3.0), which was supported by funding from the Ministry of Education and the National Research Foundation of Korea. Background Technology

[0003] Lithium-ion batteries are characterized by high energy density, long lifespan, and low self-discharge rate, making them an essential energy source in various industrial sectors, including electric vehicles, portable electronic devices, and energy storage systems (ESS). Graphite is primarily used as the anode material in commercially available lithium-ion batteries. Graphite possesses advantages such as excellent electrical conductivity, chemical stability, and low lithiation potential, and is a material that provides relatively high lithium-ion storage capacity. However, commercial graphite faces issues such as performance degradation during rapid charging and reduced durability during long-term use.

[0004] In particular, commercial graphite exhibits problems such as increased internal resistance and reduced structural stability of the electrode during high-speed charging and discharging. This leads to long-term degradation of electrochemical performance and makes efficient lithium ion insertion and extraction difficult. To address these issues, composite cathode materials such as silicon-graphite mixtures are being studied, but it remains difficult to overcome limitations caused by volume expansion and structural instability.

[0005] Furthermore, graphite is classified into natural and synthetic graphite; natural graphite requires chemical or heat treatment to improve purity, while synthetic graphite is manufactured at high temperatures, generating environmentally harmful substances and wastewater. Therefore, there is a need to develop new anode materials that can improve the performance of lithium-ion batteries while simultaneously reducing their environmental impact. Prior art literature

[0006] Korean Published Patent Application No. 10-2023-0011133 The problem to be solved

[0007] The present invention aims to provide a graphite negative electrode material for a lithium secondary battery that provides excellent electrochemical performance, and a lithium secondary battery containing the same.

[0008] In addition, the present invention can maintain a high capacity even under rapid charging and discharging.

[0009] In addition, the present invention exhibits high-efficiency electrochemical reactions by having a high surface area and pore volume compared to conventional industrial graphite.

[0010] In addition, the present invention has a long lifespan and durability.

[0011] In addition, the present invention is eco-friendly and economical by recycling carbon waste. means of solving the problem

[0012] The negative electrode material of a lithium secondary battery according to an embodiment of the present invention is HCSG (Hollow-Core Spherical Graphite), which is hollow spherical graphite with a hollow interior.

[0013] The overall average diameter of the above lithium secondary battery negative electrode material may be 20 to 50 nm.

[0014] The average diameter of the above hollows may be 5 to 10 nm.

[0015] When analyzed by Raman spectroscopy, the value of D-band intensity (ID) versus G-band intensity (IG) (ID / IG) can be 0.15 to 0.20, and the BET specific surface area is 14.1 m² 2 It can be / g, and the pore volume is 0.034 cm³ 3 It can be / g.

[0016] The above lithium secondary battery negative electrode material may be obtained by a step of obtaining a product by reacting 2,4,6-trinitrotoluene (TNT) and 3,5-trinitroperhydro-1,3,5-triazine (RDX) under high pressure and high temperature conditions, and a step of removing diamond from the product.

[0018] A method for manufacturing a lithium secondary battery negative electrode material according to an embodiment of the present invention comprises the steps of: obtaining a product by reacting 2,4,6-trinitrotoluene (TNT) and 3,5-trinitroperhydro-1,3,5-triazine (RDX) under high pressure and high temperature conditions; and removing diamond from the product.

[0019] The step of obtaining the above product can be carried out at a pressure of 20 to 30 GPa and a temperature of 3000 to 4000 K.

[0021] A lithium secondary battery negative electrode according to an embodiment of the present invention comprises a current collector and a lithium secondary battery negative electrode material disposed on the current collector. The lithium secondary battery negative electrode material is as previously described.

[0023] A method for manufacturing a lithium secondary battery negative electrode according to an embodiment of the present invention comprises the steps of: preparing a mixture by mixing a lithium secondary battery negative electrode material, a conductive material, a binder, and a solvent; applying the mixture to a current collector; and drying the mixture. The lithium secondary battery negative electrode material is as described above.

[0025] A lithium secondary battery according to an embodiment of the present invention comprises a negative electrode, a positive electrode, and an electrolyte. The negative electrode is as previously described. Effects of the invention

[0026] A method for manufacturing graphite for a lithium secondary battery negative electrode material according to an embodiment of the present invention, a lithium secondary battery graphite negative electrode material comprising said graphite, and a lithium secondary battery comprising said graphite provide excellent electrochemical performance.

[0027] In addition, the present invention can maintain a high capacity even under rapid charging and discharging.

[0028] In addition, the present invention exhibits high-efficiency electrochemical reactions by having a high surface area and pore volume compared to conventional industrial graphite.

[0029] In addition, the present invention has a long lifespan and durability.

[0030] In addition, the present invention is eco-friendly and economical by recycling carbon waste. Brief explanation of the drawing

[0031] FIG. 1 illustrates a method for manufacturing a lithium secondary battery negative electrode material according to an embodiment of the present invention. Figure 2 is a TEM image of a lithium secondary battery negative electrode material according to an embodiment of the present invention. Figure 3 is an SEM analysis photograph of an example. Figure 4 is an SEM analysis photograph of the comparative example. Figure 5 shows the XRD analysis results of the examples and comparative examples. Figure 6 shows the Raman analysis results of the examples and comparative examples. Figure 7 shows the pore size analysis results of the examples and comparative examples. Figure 8 shows the results of the constant current charge-discharge performance analysis of a coin cell using an example. Figure 9 shows the results of the constant current charge-discharge performance analysis of a coin cell using a comparative example. Figure 10 shows the results of analyzing the specific capacity and Coulomb efficiency according to the cycle of the coin cell using the example and comparative example. Figure 11 shows the EIS analysis results of a coin cell using an example and a comparative example (analysis of specific capacity and Coulomb constant according to cycle). Figure 12 shows the EIS analysis results of a coin cell using an example and a comparative example (resistance measurement after 5 cycles). Figure 13 shows the EIS analysis results of a coin cell using an example and a comparative example (resistance measurement after 500 cycles). Specific details for implementing the invention

[0032] Hereinafter, preferred embodiments of the present invention are described as follows with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Furthermore, embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0034] The lithium secondary battery negative electrode material according to an embodiment of the present invention is a hollow-core spherical graphite (HCSG). The lithium secondary battery negative electrode material may be obtained by a step of obtaining a product generated by reacting 2,4,6-trinitrotoluene (TNT) and 3,5-trinitroperhydro-1,3,5-triazine (RDX) under high pressure and high temperature conditions, and a step of removing diamond from the product.

[0036] Referring to FIG. 1(b), it can be seen that the HCSG is spherical with a diameter of several to tens of nm and has a hollow interior. Additionally, the HCSG may include mesopores exceeding 5 nm. In one embodiment, the overall average diameter of the lithium secondary battery negative electrode material may be 20 to 50 nm, and the average diameter of the hollow may be 5 to 10 nm. Furthermore, when analyzed by Raman spectroscopy, the value of D-band intensity (ID) relative to G-band intensity (IG) (ID / IG) of the HCSG may be 0.15 to 0.20, and the BET specific surface area is 14.1 m² 2 It can be / g, and the pore volume is 0.034 cm³ 3 It can be / g.

[0037] As such, the HCSG has a spherical shape, which facilitates adhesion between particles during electrode manufacturing and can reduce electrical resistance between particles. In addition, by having a porous structure, Li + The ion transport rate can be increased by shortening the ion diffusion path. In addition, the electrochemical properties can be significantly improved as the electrolyte can penetrate into the porous structure. Furthermore, the HCSG can have fast charge / discharge speeds and stability as a cathode material.

[0039] In one embodiment, the lithium secondary battery negative electrode material can be prepared by reacting 2,4,6-trinitrotoluene with 3,5-trinitroperhydro-1,3,5-triazine. More specifically, a method for preparing a lithium secondary battery negative electrode material according to an embodiment of the present invention comprises the steps of obtaining a product produced by reacting 2,4,6-trinitrotoluene with 3,5-trinitroperhydro-1,3,5-triazine under high pressure and high temperature conditions, and removing diamond from the product.

[0041] The above 2,4,6-trinitrotoluene has a structure in which three nitro groups (NO2) are bonded to the benzene ring of toluene (methylbenzene) at the 2, 4, and 6 positions, and its chemical formula is C7H5N3O6. The above 2,4,6-trinitrotoluene is a powerful explosive and rapidly releases gases such as oxygen, nitrogen, and carbon upon explosion.

[0043] The above 3,5-trinitroperhydro-1,3,5-triazine is a heterocyclic compound with a 6-membered ring structure, in which three nitro groups (NO2) are bonded to a triazine ring containing three nitrogen atoms, and its chemical formula is C3H6N6O6. Like the above 2,4,6-trinitrotoluene, it is a powerful explosive and rapidly releases gases such as oxygen, nitrogen, and carbon upon explosion.

[0045] When the above 2,4,6-trinitrotoluene and 3,5-trinitroperhydro-1,3,5-triazine are subjected to an explosive reaction at high temperature and high pressure, HCSG and nanodiamonds can be produced. The above 2,4,6-trinitrotoluene and 3,5-trinitroperhydro-1,3,5-triazine are organic compounds that serve as carbon sources, and because the reaction occurs for a very short time under high temperature and high pressure conditions followed by rapid cooling, HCSG and nanodiamonds with a size of several to tens of nanometers are produced. In one embodiment, the step of obtaining the product can be performed at a pressure of 20 to 30 GPa and a temperature of 3000 to 4000 K.

[0047] The step of removing diamonds from the above product can remove nanodiamonds and separate HCSG by various physical and chemical separation methods. For example, HCSG can be separated by centrifuging the above product in an aqueous solution.

[0049] The lithium secondary battery negative electrode according to an embodiment of the present invention may be manufactured by a general method using materials commonly used in the field, provided that the material described above is used as the secondary battery negative electrode material.

[0050] A method for manufacturing a lithium secondary battery negative electrode according to an embodiment of the present invention comprises the steps of: preparing a mixture by mixing a lithium secondary battery negative electrode material, a conductive material, a binder, and a solvent; applying the mixture to a current collector; and drying the mixture. Each of the above steps is based on methods commonly used in the relevant technical field and is not particularly limited.

[0051] In addition, a lithium secondary battery according to an embodiment of the present invention comprises a negative electrode, a positive electrode, and an electrolyte. The negative electrode is the one described above. The positive electrode and the electrolyte may be those generally used in the field, provided that the one described above is used as the negative electrode.

[0053] Preparation of carbon lithium secondary battery anode material

[0054] HCSG, a hollow spherical graphite: To manufacture HCSG, Composition B (60% TNT + 40% RDX) was sealed in a closed reactor along with water or ice and inert gases (N2, Ar) and then detonated. When the temperature and pressure exceeded the limits of 20–30 GPa and 3000–4000 K, respectively, the carbon existed in the form of liquid carbon clusters. After the explosion, as the temperature and pressure decreased, the carbon atoms condensed into nanoclusters and combined into large liquid droplets, synthesizing nanodiamonds and HCSG. The detonation soot, which is the synthetic material of the explosion, has a composition of 5 to 10% nanodiamonds, 85 to 90% HCSG, and 0 to 5% metal oxides. Subsequently, the detonation soot was dispersed in an aqueous solution, and HCSG was obtained by centrifuging using the difference in specific gravity between nanodiamonds and HCSG.

[0056] Commercial Graphite: For the commercial graphite, Showa Denko’s SCMG-BM was prepared.

[0058] Example: Preparation of an electrode

[0059] Example: A slurry was prepared by mixing 0.8 g of the previously prepared HCSG, 0.1 g of 10 wt% Super P (Sigma Aldrich), 0.1 g of 10 wt% polyvinylidene fluoride (PVDF, Sigma Aldrich), and 3 to 5 ml of N-Methyl-2-pyrrolidone (NMP, Daejeong Hwakum) and homogenizing them using a centrifugal mixer (ARM-301, THINKY). The slurry was applied onto a Cu foil (Wellcos) using a doctor blade (CV-400, Rotech) and vacuum dried at 70°C for 10 hours to prepare an electrode.

[0061] Comparative Example: An electrode was prepared in the same manner as in the example, except that commercial graphite prepared earlier was used instead of HCSG.

[0063] Experimental Example: TEM Analysis

[0064] TEM images of the example were taken using FEI Tecnai G2 F30, and the results are shown in Fig. 2. In Fig. 2, the solid line indicates the outer boundary of the HCSG, and the dotted line indicates the boundary of the internal hollow. It was confirmed that the HCSG is a spherical shape with a hollow interior.

[0066] Experimental Example: SEM Analysis

[0067] SEM images of the example and comparative example were taken using a Thermo Scientific Phenom ProX under an acceleration voltage of 15 kV and are shown in FIGS. 3 and FIGS. 4, respectively. Referring to FIGS. 3 and FIGS. 4, it can be seen that the example is more densely packed than the comparative example. This indicates that the example maintains structural integrity and can more effectively transmit electrons and ions compared to the comparative example.

[0069] Experimental Example: XRD Analysis

[0070] XRD analysis was performed on the examples and comparative examples using Panalytical BV EMPYREAN, and the results are shown in Fig. 5. In Fig. 5, the commercial graphite comparative example shows a distinct (002) peak at 2 to 26.5°, and the example HCSG also shows a distinct (002) peak at 26.6°. Therefore, it can be seen that HCSG has a hexagonal carbon structure similar to commercial graphite, and it can be expected to have electrical conductivity and mechanical stability similar to that of commercial graphite.

[0072] Experimental Example: Raman Spectroscopic Analysis

[0073] Raman spectroscopic analysis of the examples and comparative examples was performed using LabRam Soleil from HORIBA Scientific, and the results are shown in Fig. 6. In Fig. 6, 1338 cm -1 and 1570 cm-1 The D band and G band are shown, respectively, and the value of D band intensity (ID) versus G band intensity (IG) (ID / IG) was 0.17 for HCSG and 0.13 for commercial graphite. This means that HCSG has a larger surface area and more active sites compared to commercial graphite.

[0075] Experimental Example: BET Surface Area and Pore Size Analysis

[0076] BET surface area and surface pore size analysis were performed on the examples and comparative examples using Quantachrome Autosorb-iQ / MP, and the results are shown in Fig. 7. According to Fig. 7, it can be seen that the example, which is HCSG, has a significantly higher number of pores with a diameter exceeding 5 nm compared to the comparative example, which is commercial graphite. In addition, the BET surface area of ​​the example, which is HCSG, is 14.1 m². 2 / g, and the comparative example, which is commercial graphite, is 1.61 m 2 The example is about 9 times larger than the comparative example at / g. The mesopores and large surface area of ​​HCSG are due to Li + It can facilitate the movement of ions and electrolytes.

[0078] Manufacturing Example: Manufacturing of Coin Cells

[0079] A coil cell was manufactured to evaluate electrochemical performance using the electrodes of the examples and comparative examples. The working electrode was the electrode of the example and comparative example cut to a diameter of 11 mm, the counter electrode was a Li foil with a diameter of 14 mm, the electrolyte solution was a 1:1 (v / v) mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and 10% fluoroethylene carbonate (FEC) with 1M LiPF6 added, and the separator was polyethylene (Celgard 2400) to be assembled into a CR2032 coin cell.

[0081] Experimental Example: Constant Current Charge-Discharge Performance Analysis

[0082] Using WonATech WBCS3000, 0.01 to 1.50 V (vs. Li +The characteristics of coin cells assembled as examples and comparative examples were measured at C-rates of 0.1, 0.5, 1, 2, and 5 C within the voltage range ( / Li), and the results are shown in FIGS. 8 and 9, respectively. Referring to FIGS. 8 and 9, when the example was used as the electrode, the discharge capacities at each C-rate were 363.8, 346.4, 334.6, 306.5, and 187.2 mAh g⁻¹, respectively. -1 And when the comparative example was used as the electrode, the discharge capacity at each C-rate was 363.9, 325.0, 269.1, 192.2, and 81.4 mAh g -1 As such, it can be seen that the high capacity of the coin cell using the example can be maintained.

[0084] Experimental Example: Charge / Discharge Cycle Performance Analysis

[0085] The specific capacity and Coulomb efficiency according to the cycle of the coin cells assembled in the example and comparative example were analyzed, and the results are shown in FIG. 10. Referring to FIG. 10, it can be seen that the coin cell using the example shows a higher specific capacity and stable performance compared to the coin cell using the comparative example, and that recovery is well achieved.

[0087] Experimental Example: EIS Analysis

[0088] EIS analysis was performed on coin cells assembled as examples and comparative examples using the WonATech ZIVE SP1, and the results are illustrated in FIGS. 11 to 13. Referring to FIG. 11, it can be seen that the coin cell using the example maintains low resistance even during long-term cycling. Referring to FIG. 12, at 5 cycles, R of the coin cell using the example SEI It is larger than the coin cell using the comparative example, which is interpreted as being due to the larger surface area of ​​the HCSG. In addition, the R of the coin cell using the example ct Since it is significantly low, the particle has lower resistance and Li +This means that the active surface area where ions can be inserted is large. Referring to Fig. 13, after 500 cycles, the R of the coin cell using the example SEI and R ct It can be seen that it is significantly lower compared to the comparative example, indicating that the performance of the coin cell using the example is superior.

[0090] The present invention is not limited by the embodiments described above and the attached drawings, but is intended to be limited by the appended claims. Accordingly, various substitutions, modifications, and changes may be made by those skilled in the art within the scope of the technical concept of the present invention as described in the claims, and such are also to be considered to fall within the scope of the present invention.

Claims

Claim 1 A lithium secondary battery negative electrode material, which is a hollow-core spherical graphite (HCSG) with a hollow interior, obtained by the steps of: reacting 2,4,6-trinitrotoluene (TNT) and 3,5-trinitroperhydro-1,3,5-triazine (RDX) under high pressure and high temperature conditions to obtain a product; and removing diamond from the product. Claim 2 A lithium secondary battery negative electrode material according to claim 1, wherein the overall average diameter of the lithium secondary battery negative electrode material is 20 to 50 nm and the average diameter of the hollow is 5 to 10 nm. Claim 3 A lithium secondary battery negative electrode material according to claim 1, wherein the value of D-band intensity (ID) relative to G-band intensity (IG) (ID / IG) during analysis by Raman spectroscopy is 0.15 to 0.

20. Claim 4 In claim 1, the BET specific surface area is 14.1 m² 2 / g, lithium secondary battery negative electrode material. Claim 5 In claim 1, the pore volume is 0.034 cm² 3 / g, lithium secondary battery negative electrode material. Claim 6 delete Claim 7 A method for manufacturing a lithium secondary battery negative electrode material, comprising the steps of: reacting 2,4,6-trinitrotoluene (TNT) and 3,5-trinitroperhydro-1,3,5-triazine (RDX) under high pressure and high temperature conditions to obtain a product; and removing diamond from the product. Claim 8 A method for manufacturing a lithium secondary battery negative electrode material, wherein, in claim 7, the step of obtaining the product is performed at a pressure of 20 to 30 GPa and a temperature of 3000 to 4000 K. Claim 9 A lithium secondary battery negative electrode comprising a current collector and a lithium secondary battery negative electrode material disposed on the current collector, wherein the lithium secondary battery negative electrode material is that of claim 1. Claim 10 A method for manufacturing a lithium secondary battery negative electrode, comprising the steps of: mixing a lithium secondary battery negative electrode material, a conductive material, a binder, and a solvent to prepare a mixture; applying the mixture to a current collector; and drying the mixture, wherein the lithium secondary battery negative electrode material is that of claim 1. Claim 11 A lithium secondary battery comprising a cathode, a positive electrode, and an electrolyte, wherein the cathode is that of claim 9.

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