A uniform few-layered carbon coating derived from self-assembled carboxylate monolayers capable of promoting the rate properties and durability of commercial TiO2

Abstract

The poor cyclability and rate property of commercial TiO₂ (c-TiO₂) hinder its utilization in lithium-ion batteries (LIBs). Coating carbon is one of the ways to ameliorate the electrochemical performance. However, how to effectively form a uniform thin carbon coating is still a challenge. On the basis of the strong interaction of the TiO₂ surface with carboxyl groups, herein a new tactic to achieve uniform and thin carbon layers on the c-TiO₂ particles was proposed. When mixing c-TiO₂ with citric acid containing carboxyl groups in deionized water, the high-affinity adsorption of TiO₂ for carboxyl groups resulted in self-assembled carboxylate monolayers on the surface of TiO₂ which evolved into a uniform few-layered amorphous carbon coating during carbonizing at 750 °C. The product derived from the mixture of c-TiO₂ and citric acid with a mass ratio of 1 : 0.3 exhibits the optimal performance, revealing a high specific capacity (256.6 mA h g⁻¹ after 50 cycles at 0.1 A g⁻¹) and outstanding cycling stability (retaining a capacity of 160.0 mA h g⁻¹ after 1000 cycles at 0.5 A g⁻¹). The greatly enhanced capacity and cyclability correlate with the uniform few-layered carbon coating which not only ameliorates the electronic conductivity of c-TiO₂ but also avoids the reduction in ionic conductivity caused by thick carbon layers and redundant carbon.