Doping and surface modification enhance the applicability of Li4Ti5O12 microspheres as high-rate anode materials for lithium ion batteries

In this study we prepared Mg2+ and Cr3+ co-doped and phosphidated Li4Ti5O12 (LTO) microspheres using a spray-drying method. Doping with both Mg2+ and Cr3+ improved the electronic conduction of LTO, due to partial reduction of Ti4+ (from Ti4+ to Ti3+) and narrowing of the band gap, respectively. Moreover, the phosphidation process formed a uniform conductive glass layer on the LTO surface, leading to higher ionic conductivity. As a result, the modified LTO exhibited improved rate capability and cyclic stability, compared with those of the pristine LTO. In particular, the Mg2+ and Cr3+ co-doped and phosphidated LTO exhibited superior performance as a result of the combined effects of ion-doping and interfacial modification. Finally, the capacity improved significantly, especially at high C rates [e.g., 127.72 mA h g(-1) at 20 C-77.6% of the value recorded at 0.1 C (164.62 mA h g(-1))], due to the dual effects of the enhanced electric and ionic conductivities.