1. Guangxi Academy of Sciences Nanning Guangxi 530007 P. R. China
2. Guangxi Key Laboratory of Information Materials Guilin University of Electronic Technology Guilin 541004 P. R. China
3. College of Materials Science and Engineering Hunan Joint International Laboratory of Advanced Materials and Technology for Clean Energy Hunan University Changsha 410082 P. R. China
4. School of Materials Science and Engineering South China University of Technology Guangzhou 510641 P. R. China
5. Guangxi Key Laboratory of Electrochemical Energy Materials School of Chemistry and Chemical Engineering Guangxi University Nanning 530004 P. R. China