Lanthanide doping induced electrochemical enhancement of Na2Ti3O7 anodes for sodium-ion batteries

摘要

Na _(2) Ti _(3) O _(7) is considered as a promising anode material for sodium ion batteries (SIBs) due to its excellent high-rate performance compared with hard carbons. However, the electrochemical performance of Na _(2) Ti _(3) O _(7) is heavily limited by its low electrical conductivity. In this study, we synthesized a series of lanthanide (Ln = La, Ce, Nd, Sm, Gd, Er, and Yb) doped microsized Na _(2) Ti _(3) O _(7) anode materials and systematically studied the electrochemical performance. Compared with pristine Na _(2) Ti _(3) O _(7) , all the doped samples show superior electrochemical performance. Especially, the Yb ~(3+) doped sample not only delivers a high reversible capacity of 89.4 mA h g ~(?1) at 30C, but also maintains 71.6 mA h g ~(?1) at 5C after 1600 cycles, nearly twice that of pristine Na _(2) Ti _(3) O _(7) . It is found for the first time that the enhancement in doped samples is attributed to the introduction of lanthanides which induces lattice distortion and oxygen vacancies.