1. The Jiangsu Province Engineering Laboratory of High Efficient Energy Storage Technology and Equipments School of Materials Science and Physics China University of Mining and Technology Xuzhou 221116 P. R. China
2. Jiangsu Huaheng New Energy Company Xuzhou 221116 P. R. China
3. Institute of New Energy Materials Chemistry, School of Materials Science and Engineering Nankai University Tianjin 300350 P. R. China