还原氧化石墨烯含量对LVP/C@rGO复合材料电化学性能的影响

Effect of reduced oxide graphene content on electrochemical performance of LVP/C@rGO materials

针对磷酸钒锂电导率低的问题,采用微波消解法合成还原氧化石墨烯负载碳包覆磷酸钒锂复合材料(LVP/C@rGO)。借助XRD、SEM等手段表征复合材料的结构和形貌,通过恒流充放电、循环伏安测试等实验分析还原氧化石墨烯含量对其电化学性能的影响。结果表明:复合材料中磷酸钒锂具有P21/n空间结构,碳包覆磷酸钒锂均匀地分布在还原氧化石墨烯表面,磷酸钒锂表面碳层的厚度约为4 nm。还原氧化石墨烯的加入能够抑制焙烧过程中磷酸钒锂晶体的团聚。含7%还原氧化石墨烯的复合材料的电化学性能最好。在3.0~4.3 V电压范围、0.5 C倍率条件下其首次放电比容量为130 m Ah/g,0.5 C倍率条件下循环100周时,比容量保持率为99.5%,锂离子扩散系数约为2.08×10^(-11)cm^2/s。

This paper is an effort to address the lower conductivity of Li3V2（PO4）3. The research involves synthesizing the reductive oxidation graphene with carbon coated lithium vanadium phosphate cathode materials（ LVP/C@rGO） using microwave digestion method; characterizing the structure and morphology of the composite materials using XRD and SEM etc; and analyzing the effect of reduced graphene oxide on its electrochemical performance using experiments such as constant current charge-discharge and cyclic voltammetry,and EIS. The results demonstrate that crystalline structure of composite is of the P21/n space structure; the crystal of vanadium phosphate is uniformly loaded on the surface of reduced graphene oxide; amorphous carbon coats lithium phosphate with the thickness of about 4 nm; the addition of reductive oxidation graphene could provide the inhibition of the agglomeration of lithium vanadium phosphate crystals during the calcination process; and the composite materials with reductive oxidized graphene content of 7% boast the best electrochemical performance： the initial discharge specific capacity of 130 m Ah/g at 3. 0-4. 3 V voltage range and under 0. 5 C; the specific capacity retention rate of 99. 5% for100 times of charge and discharge under 0. 5 C; and lithium ion diffusion coefficient of about 2. 08 ×10-11 cm2/s.