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Keywords:

  • carbon;
  • electrochemistry;
  • lithium;
  • nanoparticles;
  • nitrogen

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[BOND]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.