Polyacrylonitrile block copolymers for the preparation of a thin carbon coating around TiO₂ nanorods for advanced lithium-ion batteries

Herein, a new method for the realization of a thin and homogenous carbonaceous particle coating, made by carbonizing RAFT polymerization derived block copolymers anchored on anatase TiO₂ nanorods, is presented. These block copolymers consist of a short anchor block (based on dopamine) and a long, easily graphitizable block of polyacrylonitrile. The grafting of such block copolymers to TiO₂ nanorods creates a polymer shell, which can be visualized by atomic force microscopy (AFM). Thermal treatment at 700 °C converts the polyacrylonitrile block to partially graphitic structures (as determined by Raman spectroscopy), establishing a thin carbon coating (as determined by transmission electron microscopy, TEM, analysis). The carbon-coated TiO₂ nanorods show improved electrochemical performance in terms of achievable specific capacity and, particularly, long-term cycling stability by reducing the average capacity fading per cycle from 0.252 mAh g^-1 to only 0.075 mAh g^-1. A thin and homogeneous carbon coating of anatase TiO₂ nanorods is described involving a new approach using block copolymers synthesized by RAFT polymerization. Grafting of these polymers onto the TiO₂ nanoparticle surfaces followed by pyrolysis results in carbon-coated particles, which are utilized as an electrode material in a lithium-ion half-cell configuration that shows a substantially enhanced electrochemical performance.