High-performance anode materials based on anthracite for lithium-ion battery applications
摘要: 以我国资源丰富的低成本优质无烟煤为原料，经过2800 ℃高温纯化、石墨化处理，制备出锂电池用负极材料，用相同手段处理商业化石墨的前体石油焦与石墨化无烟煤作对比。通过X射线衍射（XRD），扫描电子显微镜（SEM），透射电子显微镜（TEM），拉曼光谱（Roman）和氮吸附−解吸等手段对无烟煤基负极材料进行微观结构的表征。采用恒流充放电（GCD），循环伏安（CV）表征其电化学性能。实验结果表明，无烟煤基石墨化负极材料的石墨化度可达95.44%，比表面积为1.1319 m2·g−1，石墨片层结构平整光滑。该石墨化无烟煤作为锂离子电池的负极材料首次库伦效率为87%，在0.1C的电流密度下具有345.3 mA·h·g−1的可逆容量，且在高倍率下该材料比石墨化石油焦材料显现出更好储锂性能，这归功于石墨化无烟煤较为规则高度有序的表面结构。在不同倍率循环后电流密度恢复到0.1C时容量基本无衰减，100圈循环后可逆容量保持率高达93.8%，基本与石墨化石油焦负极相当，拥有优异的循环稳定性。无烟煤基石墨在容量、倍率性能及循环稳定性上基本接近甚至超过石墨化石油焦。本研究表明，采用优质无烟煤作为原料生产锂离子电池负极材料具有潜在的研究价值和广阔的商业前景。Abstract: The rise in the price of petroleum coke and needle coke, which are used as anode materials of lithium-ion batteries, has revealed the difficulty of the industry in finding high-performance and low-cost alternatives of these raw materials. In this study, anthracite, a low-cost, high-quality raw material, of which China is rich in resources, was used. After a 2800 °C purification and graphitization treatment, the anode material for lithium battery was prepared. Petroleum coke, as the precursor of commercial graphite, was treated using the same method that was being used for graphitized anthracite, for comparison reasons. The microstructure of anthracite-based anode materials was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (Roman), and nitrogen adsorption-desorption. Cyclic voltammetry (CV) was used to characterize the electrochemical performance of anthracite-based anode materials by applying constant current charge and discharge (GCD). The experimental results show that the graphitization degree of anthracite-based graphitized anode material can reach 95.44%, with the specific surface area being 1.1319 m2·g−1, and the graphite sheet structure is found to be smooth. The graphitized anthracite, as the anode material of a lithium-ion battery, has a first coulombic efficiency of 87% and a reversible capacity of 345.3 mA·h·g−1 at a current rate of 0.1C, and the material has better lithium storage performance than graphitized petroleum coke material at a high rate. The relatively highly ordered surface structure of graphitized anthracite leads to a better storage performance of lithium. When the current rate returns to 0.1C after different current rates, the capacity has basically no attenuation. After 100 cycles, the reversible capacity retention rate is as high as 93.8%, which is basically equivalent to the rate of graphitized petroleum coke anode while the graphitized anthracite also shows excellent cycle stability. Anthracite-based graphite is equivalent or even superior to graphitized petroleum coke in terms of capacity, rate performance, and cycle stability. This study shows that the use of high-quality anthracite as raw material for the production of lithium-ion battery anode materials has a potential research value and broad commercial prospects.
图 5 GA和GPC样品的吸附曲线及孔径分布情况。（a）GA的氮气吸附−解吸等温线；（b）GA的孔径分布曲线；（c）GPC的氮气吸附−解吸等温线；（d）GPC的孔径分布曲线
Figure 5. Adsorption curve and pore size distribution of GA and GPC sample: (a) nitrogen adsorption-desorption isotherm of GA; (b) pore size distribution curve of GA; (c) nitrogen adsorption-desorption isotherm of GPC; (d) pore size distribution curve of GPC
表 1 实验药品和试剂
Table 1. Experimental samples and reagents
Reagent name Chemical formula Reagent grade Supplier Polyvinylidene fluoride（PVDF） [−CH2−CF2−] Premium grade CALB Co., Ltd. N-methylpyrrolidone（NMP） C5H9NO Electronic grade Shanghai Titan Technology Co., Ltd. Electrolyte LiPF6 Electronic grade BAK Battery Co., Ltd. Acetylene carbon black（Super-P） C Electronic grade Mitsubishi Chemical Co., Ltd.
表 2 石墨化无烟煤灼烧数据
Table 2. Graphitized anthracite burning data
Number Net weight of crucible, m1/g Sample quality, m2/g Total mass after burning, m3/g Ash, (m3−m1)·m2−1/% 1 17.1098 1.5137 17.1140 0.277 2 17.0690 1.5553 17.0732 0.270 3 16.7645 1.0415 16.7674 0.278 4 16.9199 1.0513 16.9229 0.275
表 3 GA和GPC的首次充放电容量和库伦效率
Table 3. First charge and discharge capacity and coulombic efficiency of GA and GPC
Sample name First discharge capacity/(mA·h·g−1) First charge capacity/(mA·h·g−1) Irreversible capacity/(mA·h·g−1) Coulombic efficiency/% GA 415.4 361.4 54 87 GPC 395.8 346.3 49.5 87.5
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