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

Abstract In this study we prepared Mg 2+ and Cr 3+ co-doped and phosphidated Li 4 Ti 5 O 12 (LTO) microspheres using a spray-drying method. Doping with both Mg 2+ and Cr 3+ improved the electronic conduction of LTO, due to partial reduction of Ti 4+ (from Ti 4+ to Ti 3+ ) 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 Mg 2+ and Cr 3+ 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.