Effect of Sodium-Site Doping on Enhancing the Lithium Storage Performance of Sodium Lithium Titanate

摘要

Via Li+, Cu2+, Y3+, Ce4+, and Nb5+ dopings, a series of Na-site-substituted Na1.9M0.1Li2Ti6O14 are prepared and evaluated as lithium storage host materials. Structural and electrochemical analyses suggest that Na-site substitution by high-valent metal ions can effectively enhance the ionic and electronic conductivities of Na2Li2Ti6O14. As a result, Cu2+-, Y3+-, Ce4+-, and Nb5+-doped samples reveal better electrochemical performance than bare Na(2)Li(2)T(i)6O(14), especially for Na1.9Nb0.1Li2Ti6O14, which can deliver the highest reversible charge capacity of 259.4 mAh g(-1) at 100 mA g(-1) among all samples. Even when cycled at higher rates, Na1.9Nb0.1Li2Ti6O14 still can maintain excellent lithium storage capability with the reversible charge capacities of 242.9 mAh g(-1) at 700 mA g(-1), 216.4 mAh g(-1) at 900 mA g(-1), and 190.5 mAh g(-1) at 1100 mA g(-1). In addition, ex situ and in situ observations demonstrate that the zero-strain characteristic should also be responsible for the outstanding lithium storage capability of Na1.9Nb0.1Li2Ti6O14. All of this evidence indicates that Na1.9Nb0.1Li2Ti6O14 is a high-performance anode material for rechargeable lithium ion batteries.