Co-Modification of commercial TiO2 anode by combining a solid electrolyte with pitch-derived carbon to boost cyclability and rate capabilities

Abstract

The bad electrochemical performance circumscribes the application of commercial TiO₂ (c-TiO₂) anodes in Li-ion batteries. Carbon coating could ameliorate the electronic conductivity of TiO₂, but the ionic conductivity is still inferior. Herein, a co-modification method was proposed by combining the solid electrolyte of lithium magnesium silicate (LMS) with pitch-derived carbon to concurrently meliorate the electronic and ionic conductivities of c-TiO₂. The homogeneous mixtures were heated at 750 °C, and the co-modified product with suitable amounts of LMS and carbon demonstrates cycling capacities of 256.8, 220.4, 195.9, 176.4, and 152.0 mA h g⁻¹ with multiplying current density from 100 to 1600 mA g⁻¹. Even after 1000 cycles at 500 mA g⁻¹, the maintained reversible capacity was 244.8 mA h g⁻¹. The superior rate performance and cyclability correlate closely with the uniform thin N-doped carbon layers on the surface of c-TiO₂ particles to favor the electrical conduction, and with the ion channels in LMS as well as the cation exchangeability of LMS to facilitate the Li⁺ transfer between the electrolyte, carbon layers, and TiO₂ particles. The marginal amount of fluoride in LMS also contributes to the excellent cycling stability of the co-modified c-TiO₂.