1. Henan Joint International Research Laboratory of New Energy Storage Technology, Xinyang Normal University, Xinyang 464000, P. R. China
2. College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061, P. R. China
3. Pingdingshan University, Pingdingshan 467000, P. R. China
4. City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China