Amorphous TiO₂ Nanotube Anode for Rechargeable Sodium Ion Batteries

TLDR

Sodium ion batteries offer a cost‑effective alternative to lithium ion batteries, yet few low‑voltage metal‑oxide anodes can reversibly host sodium ions at room temperature. The authors synthesize binder‑free amorphous TiO₂ nanotube electrodes directly grown on current collectors for use as sodium‑ion battery anodes. Only large‑diameter (>80 nm ID) amorphous TiO₂ nanotubes support sodium‑ion cycling, delivering 150 mAh g⁻¹ over 15 cycles and enabling the first all‑oxide Na‑ion full cell with good rate capability.

Abstract

Sodium ion batteries are an attractive alternative to lithium ion batteries that alleviate problems with lithium availability and cost. Despite several studies of cathode materials for sodium ion batteries involving layered oxide materials, there are few low-voltage metal oxide anodes capable of operating sodium ion reversibly at room temperature. We have synthesized amorphous titanium dioxide nanotube (TiO2NT) electrodes directly grown on current collectors without binders and additives to use as an anode for sodium ion batteries. We find that only amorphous large diameter nanotubes (>80 nm I.D.) can support electrochemical cycling with sodium ions. These electrodes maximize their capacity in operando and reach reversible capacity of 150 mAh/g in 15 cycles. We also demonstrate for the first time a full cell all-oxide Na ion battery using TiO2NT anode coupled to a Na1.0Li0.2Ni0.25Mn0.75Oδ cathode at room temperature exhibiting good rate capability.