Deficient TiO2−x coated porous SiO anodes for high-rate lithium-ion batteries

Abstract

Silicon monoxide (SiO) is regarded as a promising material to replace traditional graphite anode in the next generation lithium-ion batteries. However, the huge volume expansion and poor ionic/electronic conductivity of SiO particles largely restrict its application in the fast charging and discharging process. Herein, a deficient TiO_2−x coated porous SiO structure was designed through the Ag-assisted chemical etching process followed by a hydrolysis approach. Within this composite, the internal pores of SiO particles could accommodate the irregular volume change and also shorten the diffusion pathway of lithium ions. Moreover, the outer TiO_2−x could provide a protective shell and favor the generation of stable SEI films. In addition, the large specific surface area increases surface active sites and promotes the electrochemical reaction of lithium ions during the high-rate lithiation/de-lithiation process. As a result, the synthesized porous SiO/TiO_2−x composites delivered a high capacity of 501.2 mA h g⁻¹ with a capacity retention of 52.41% at a current density of 1.0 A g⁻¹ after 300 cycles. Even at 2.0 A g⁻¹, it maintained a reversible capacity of 423.4 mA h g⁻¹ after 500 cycles. Finally, a full cell composed of porous SiO/TiO_2−x composites and commercial LiCoO₂ presented a distinctive enhancement in energy density compared with that of a pure SiO anode. A series of characterization analyses and electrochemical measurements were performed to disclose the mechanism for the superb performance of materials.