CVD-GROWTH SIMULATION OF PYROLYTIC CARBON ON SPHERONIZED GRAPHITE BY BENZENE PRECURSOR

Modeling of pyrolytic carbon (PyC) coating on spheronized graphite particles was performed. The model takes into account convective and radiative heat transfer, particle movement in a fluidized bed, benzene pyrolysis kinetics and carbon deposition in view of the adhesion coefficient. It has been shown that efficient benzene decomposition for PyC coating formation occurs at temperature of 1000–1100℃. A nitrogen pulse feed rate of 10 pulses min-1 maximizes particle concentration in the benzene active decomposition zone. A semi-empirical model predicting PyC coating thickness as a function of temperature and particle diameter was presented. The calculated layer thickness varies from 40 to 90 nm and is in good agreement with the experiment. The obtained anode material exhibits ≤ 5% loss in specific discharge capacity at 2C and recovers up to 99% capacity at 0.1C.

本研究针对球化石墨颗粒表面的热解碳（PyC）涂层开展了建模研究。该模型综合考量了对流与辐射换热、流化床内颗粒运动、苯热解动力学以及考虑附着系数的碳沉积过程。研究表明，用于PyC涂层制备的高效苯分解反应发生于1000~1100℃的温度区间内。当氮气脉冲进料速率为10次·分钟⁻¹时，苯活性分解区内的颗粒浓度可达到最大值。本研究提出了一款半经验模型，可基于温度与颗粒直径预测PyC涂层厚度。计算得到的涂层厚度介于40~90 nm之间，与实验结果吻合良好。所制备的负极材料在2C倍率下的比放电容量衰减率不超过5%，且在0.1C倍率下可恢复至99%的容量。