1. The Center of New Energy Materials and Technology School of Materials Science and EngineeringSouthwest Petroleum University Chengdu Sichuan 610500 P.R. China
2. Research Institute (RI) NingDe Amperex Technology Limited Ningde Fujian 352100 P.R.China
3. Institute of Microstructure and Properties of Advanced MaterialsBeijing University of Technology Beijing 100124 P.R.China
4. Department of Materials Science and EngineeringUniversity of Washington Seattle WA 98195 USA