Single-layer graphene-wrapped Li4Ti5O12 anode with superior lithium storage capability

Graphene has been intensively adopted into boosting the electrochemical performances of battery electrode materials due to its superior nature. In the case of Li4Ti5O12 (LTO), the application of graphene has been specifically focused on ameliorating the low electronic conductivity of LTO. So far, these attempts aiming to increase the composite's electronic conductivity involved thick graphene layers, which inevitably hindered Li-ion diffusion and eventually harmed the electrochemical kinetics in LTO's surface. In this work, high quality minimum-impurity graphene oxide was prepared by means of thorough cleaning and dialysis, which enabled each single-layered graphene to successfully wrap individual LTO particles. The resulting single-layer graphene-wrapped LTO exhibits an excellent specific capacity of 130 mAh g−1 even at a lithiation/delithiation of 30 C. Such a high rate capability is one of the highest values among the reported LTO with comparable sizes (∼200 nm). To uncover the reasons for such high performance, electrochemical properties from varied graphene contents were juxtaposed for comparison, and as a result, number of graphene layers and the corresponding kinetic parameters were found correlated. With adequate validity, single graphene layer was revealed to be the uttermost optimum for both Li+ diffusion and electronic conduction.