Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw materials.Among the several candidate materials for the anode,spinel-type Li4Ti5O12 (LTO) has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na+ intercalation properties.However,a low diffusion coefficient for Na+ and the insulating nature of LTO remains challenging for practical sodium-ion battery systems.Herein,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO.We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO.Optimized Cr doped LTO shows a superior reversible capacity of 110 mAh g-1 after 400 cycles at 1C,with a three-fold higher capacity (75 mAh g-1) at 10C compared with undoped LTO material.This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.