製程參數最適化在石墨烯鋰電池負極材料之研究

Process-Optimization for Synthesizing Graphene Nanosheets as Anode Materials for Li-Ion Batteries

本研究藉由控制氧化參數及高溫熱脫層製備出具有不同官能基之石墨烯奈米薄片，探討石墨烯負極於鋰離子電池之應用。所探討之參數包括氧化劑選擇、氧化劑配比及石墨起始物尺寸。除了以SEM、FTIR、XRD 及TGA 分析材料的結構特性外，亦由充放電測試及循環壽命測試探討石墨烯負極之電化學特性與鋰離子電池之充放電行為。研究結果顯示以硫酸／磷酸9：1作為嵌入劑及添加硝酸鈉氧化劑為最佳之製程。製得之石墨烯於第一次充放電電容量分別可達到2172 mAh/g 及783 mAh/g，且循環30 次後可逆電容量仍可保有1165mAh/g約為商業化石墨負極電容量之3倍。我們藉由控制氧化參數成功製備出具有高可逆電容量及良好循環壽命之石墨烯負極材料，預期對鋰離子電池負極之開發有所助益。

In this study, we synthesize chemical-exfoliated graphene nanosheets(GNS) with different functional groups via controlling the oxidation parametersin conjunction with subsequently thermal exfoliation and investigatetheir electrochemical performance for Li-ion battery applications.The corresponding oxidation parameters include the sorts of oxidants,the recipe of oxidants and particle sizes of being-treated graphite have beeninvestigated. As-synthesized GNS with different acid treatments werecharacterized by SEM, FTIR, XRD, TGA as well as charge/discharge testsand cycling tests. The results indicate that the optimized condition forsynthesizing GNS anode materials for Li-ion batteries is by usingH2SO4/H3PO4 as composite oxidants with the ratio of 9 : 1 with addingNaNO3 agent during the oxidation processes. The first discharge and charge capacities of oxidation processes-optimized GNS anodes were ashigh as 2172 mAh/g and 783 mAh/g, respectively. The reversible capacityafter 30 cycles maintained a high capacity of 1165mAh/g, which is almostthree times than that of commercial graphite anode materials. Thecorresponding results demonstrate we successfully synthesized high reversiblecapacity and excellent cycle life of graphene anode materials viatuning the oxidation parameters, which could be a potential candidate as aanode material for Li-ion batteries.