Design of a Nitrogen‐Doped, Carbon‐Coated Li4Ti5O12 Nanocomposite with a Core–Shell Structure and Its Application for High‐Rate Lithium‐Ion Batteries. Issue 1 (29th November 2013) - Li, Hongsen
Abstract A facile solution‐based synthesis and characterization of a nitrogen‐doped, carbon‐coated Li4Ti5O12 (NC‐LTO) nanocomposite is reported. The mesoporous TiO2 nanoparticles (NPTiO2) are first prepared by using nanocrystalline cellulose (NCC) as a template and subsequently transform in situ into an NC‐LTO nanocomposite with a core–shell structure by using the ionic liquid 1‐ethyl‐3‐methylimdazolium tricyanomethanide as the carbon source. Various state‐of‐the‐art techniques, including field‐emission SEM, TEM, scanning transmission electron microscopy, XRD, X‐ray photoelectron spectroscopy, and thermogravimetric analysis, were performed to characterize the morphologies, structures, and compositions. Such NC‐LTO nanocomposites have a well‐defined LTO core and thin uniform carbon shell with a thickness of 1–2 nm. Electrochemical tests reveal that the NC‐LTO nanocomposite delivers a reversible capacity of 171.5 mAh g−1 at 0.2 C, and shows remarkable rate capability by maintaining 63 % of the capacity at 60 C (vs. 0.2 C), as well as excellent cycling stability with a capacity retention of 95 % after 300 cycles at a rate of 10 C. The excellent electrochemical performance is attributed exclusively to the well‐defined core–shell nanostructure and high electric conductivity. The nanosized LTO core can significantly shorten the transport lengths of lithium ions and the admirable electric conductivity of the nitrogen‐doped carbon shell can act as an "expressway" for electrons and lithium ions to transport them between the anode material core and the electrolytes.