Influence of Lithium Precursors and Calcination Atmospheres on Graphene Sheets-Modified Nano-Li4Ti5O12 Anode Material
In this study, we systematically investigated the influence of lithium precursor and calcination atmosphere on the reaction mechanisms, phase formation, particulate morphology, surface properties and electrochemical performance of graphene sheets-modified nano-Li4Ti5O12 composite. The results shown that the lithium precursor containing carboxyl anion such as LiAc and Li2CO3 would connect with oxygen groups of GO by strong hydrogen bonds to restrict the morphology of composites and the phase formation of pure spinel Li4Ti5O12. Furthermore, the oxygen ratio in the molecular structure of lithium compound is proportional to the consumption of graphene. In addition, the reducing atmosphere facilitates the partial reduction of Ti4+ to promote the interfacial charge transfer kinetics of the product.
Through optimization the conditions of the reaction, the sample adopting LiOH precursor with adjustment GS ratio calcined under Ar/H2 (5 %) atmosphere delivers 172.8 mAh g-1 at 1 C and maintained a discharge capacity of 98.0 mAh g-1 at a high rate of 40 C. This sample also showed fairly stable cycling performance. After 800 deep cycles at a high charge/discharge rate of 40 C, the capacity can hold 97.7 % of its second discharge value. This study not only provides an optimization of Li precursor and calcination condition for GS modified LTO material, but also has significant reference value for any combination reaction with GO participation.