Investigations on the Electrochemical and Mechanical Properties of Sb 2 O 3 Nanobelts by In Situ Transmission Electron Microscopy.

Sb 2 O 3 shows great promise as a high-capacity anode material for sodium-ion batteries (SIBs) due to the combined mechanisms of intercalation, conversion, and alloying. In this work, the electrochemical performance and mechanical property of Sb 2 O 3 nanobelts during sodiation/desodiation are revealed by constructing nanoscale solid-state SIBs in a high-resolution transmission electron microscopy. It is found that the Sb 2 O 3 nanobelt exhibits an ultrahigh sodiation speed of ≈13.5 nm s -1 and experiences a three-step sodiation reaction including the intercalation reaction to form Na x Sb 2 O 3 , the conversion reaction to form Sb, and the alloying reaction to form NaSb. The alloying reaction is found to be reversible, while the conversion reaction is partially reversible. The Sb 2 O 3 nanobelt shows anisotropic expansion and the orientation of the Sb 2 O 3 nanobelt has great influence on the expansion ratio. It is found that the existence of a {010} plane with large d-spacing in the nanobelt leads to a surprisingly small expansion ratio (≈5%). The morphology of the Sb 2 O 3 nanobelt is well maintained during multiple electrochemical cycles. In situ bending experiments suggest that the sodiated Sb 2 O 3 nanobelts show improved toughness and flexibility compared to pristine Sb 2 O 3 nanobelts. These fundamental studies provide insight into the rational design of anode materials with improved electrochemical and mechanical performance in SIBs.