A new strategy for the construction of 3D TiO2 nanowires/reduced graphene oxide for high-performance lithium/sodium batteries

Abstract

Anatase TiO₂ is inexpensive and potentially has high capacity as an Li⁺/Na⁺ battery anode, but its low capacity utilization and poor rate capability remain a challenge for practical applications. To address this issue, the fabrication of the 3D rational nanoarchitecture of anatase TiO₂ nanowires (NWs) with desired size and microstructure on a reduced graphene oxide (RGO) host is an efficient and promising approach to meet the demand of high Li/Na storage and rate capability. However, to date, most of the reported anatase TiO₂ NW_s/RGO composites have been synthesized via the hydrothermal method and rarely investigated for Li⁺/Na⁺ batteries. Thus, herein, an innovative supercritical CO₂ fluid-assisted strategy (SCFAS) is proposed for the synthesis of ultrafine TiO₂ NWs/RGO composites. With the aid of the high permeability and superior solvability of supercritical CO₂ fluid, the diameter of the ultrafine TiO₂ NWs was well controlled at around 4.2 nm. Even at a high TiO₂ loading (79.4 wt%), the TiO₂ NWs still showed good dispersion and tight contact with the RGO host. As an anode material for Li-ion batteries, the reversible capacity of the as-formed composite remained 666 mA h g⁻¹ after 300 cycles at 0.1 A g⁻¹ and 460 mA h g⁻¹ after 2000 cycles at 2 A g⁻¹, which is nearly twice of that synthesized from the hydrothermal method. When cycled against Na, the reversible capacity was 113 mA h g⁻¹ with 81.8% retention even at 5 A g⁻¹ after 5000 cycles, which is better than other TiO₂/RGO composites reported thus far. Noteworthy, this SCLAS method is universally suited for the construction of other 3D metal oxide/RGO nanocomposites for electrochemical energy storage.