微扩层鳞片石墨负极材料的制备及电化学性能研究

Preparation and Electrochemical Performance of Flake Graphite Anode Materials with Slightly Expanded Interlayer

研究了微扩层鳞片石墨的制备工艺、晶体结构、表面形貌以及电化学行为之间的关系。采用XRD和SEM等手段分析了石墨样品的结构和表面形貌;采用比表面积分析仪、振实密度仪分别测试了样品的BET比表面积和振实密度等指标;并应用恒电流充放电测试、循环伏安技术和电化学阻抗法(EIS)研究了微扩层处理前后石墨负极的电化学行为。结果表明,经微扩层处理后,石墨的平均层间距d002略微增大,平均晶粒尺寸Lc、La减小,颗粒的表面更光滑。微扩层石墨的首次库伦效率从91.6%提高至92.7%,可逆容量由345.5 mAh/g提高至379.8 mAh/g。且其循环性能与倍率放电性能均得到有效改善,同时石墨的嵌锂电位略有提高,锂离子从石墨中脱出更容易,电化学可逆性提高。分析是由于微扩层后石墨负极材料脱嵌锂反应的活化能降低所致。

Correlation among preparation method, crystal structure, morphology and electrochemical performance of graphite with a slightly expanded interlayer were investigated. The structure and morphology of the samples were characterized by XRD and SEM analysis, respectively. The specific surface area （BET） and tap density were tested by the related equipments, The elec- trochemical behavior of the samples was studied using galvanostatic charge/discharge test, cyclic voltammograms, and electro- chemical impedance spectra. The results indicate that average interlayer distance d002 of modified graphite expands slightly, and average in-plane crystallite size La and Lc decrease, while spherical graphite particles become smoother. Electrochemical meas- ures show that the initial columbic efficiency of graphite increases from 91.6% to 92.7%, and reversible capacity increases from 345.5 mAh/g to 379.8 mAh/g, while both cycling performance and rate discharge capacity are improved. The intercalation po- tential of modified graphite is mild increased, lithium-ion can deinterealate from graphite more easily, and the electrochemical reversibility of graphite is improved, compared with that of the raw graphite. The improvement can be ascribed to the reduction of activation energy of deintercalation reaction for modified graphite.