Modulating the Stoichiometry and Lithium Content to Boost the Electrochemical Performance of Li2ZnTi3O8 via High Valence Nb5+ Dopants

A series of anode materials with the general formula of Li2ZnTi3O8 (LZTO) and Li2-xZnTi3-xNbxO8 (x = 0.2, 0.4, and 0.5) (LZTNO) are designed. Different amount of high valence Nb5+ dopants not only reduces the content of lithium in LZTO but also alters the intrinsic characteristics of the composites, leading to optimized electrochemical performances. XRD, SEM, TEM, and XPS results suggest that Nb dopants are introduced successfully, but large amount of Nb5+ dopants (x > 0.2) result in the formation of ZnNb2O6 and TiO2. Owing to the small particle size and the improved structural stability, LZTNO-2 sample exhibits the best electrochemical performance, and it can deliver a charge/discharge capacity of 182.7/181.2 mAh g(-1) at 1 A g(-1) after 500 cycles, which is much higher than the value of LZTO (100.41/100.41 mAh g(-1)). The experiments suggest that the introduction of high valence dopants can effectively modulate the stoichiometry and lithium content of the anode materials, making the available vacant sites for subsequent intercalation of lithium obviously extended. Such a strategy is expected to be feasibly applied to other anode materials to enhance their specific capacity and electrochemical performances.