Surfactant-templating strategy for ultrathin mesoporous TiO2 coating on flexible graphitized carbon supports for high-performance lithium-ion battery

Abstract

The electrochemical performance of nanocomposites could greatly be improved by rationally designing flexible core-shell heterostructures. Typically, the uniform coating of a thin mesoporous crystalline transition metal oxide shell on flexible graphitized carbon supports can provide both fast ion and electron transport pathways, which is an ideal material for high-performance lithium-ion batteries. Herein, we report a surfactant-templating assembly coating method to deposit an ultrathin mesoporous crystalline TiO2 shell on flexible graphitized carbon supports by using amphiphilic triblock copolymer Pluronic F127 as a template. Taking multi-wall carbon nanotubes (CNTs) as an example support, the obtained flexible CNTs@mTiO2 hybrid mesoporous nanocables exhibit an ultra-high surface area (~137 m2/g), large internal pore volume (~0.26 cm3/g), uniform accessible mesopores (~6.2 nm) and ultrathin highly-crystalline mesoporous anatase shells (~20 nm in thickness). As an anode material for lithium battery, the flexible CNTs@mTiO2 hybrid mesoporous nanocables show high-rate capacity (~210 mA h g-1 at 20 C, 1 C=170 mA g-1), high Coulombic efficiency (nearly 100% during 1000 cycles at 20 C) and ultralong-cycling life (keeping ~210 mAh g-1 after 1000 cycles at 20 C). The strong synergistic coupling effect between CNT cores and thin mesoporous TiO2 shells, high surface area, accessible large pores and highly crystalline thin mesoporous shells result in excellent performance in lithium batteries. This versatile surfactant-templating assembly coating method can be easily extended to deposit an ultrathin mesoporous TiO2 layer on flat graphene (GR) to form a uniform sandwich-like flexible GR@mTiO2 nanoflakes, which opens up a new opportunity for depositing thin mesoporous transition-metal oxides on graphitized carbon supports for advanced applications in energy conversion and storage, photocatalysis, sensors and drug delivery, etc. 2016 Elsevier Ltd.