Abstract
Understanding the structural transformations that materials undergo during (de)insertion of Li ions is crucial for designing high-performance intercalation hosts as these deformations can lead to significant capacity fade. Herein, we present a study of the metallic defect perovskite ReO3 to determine whether these distortions are driven by polaronic charge transport (i.e., the electrons and ions moving through the lattice in a coupled way) due to the semiconducting nature of most oxide hosts. Employing numerous techniques, including electrochemical probes, operando X-ray diffraction, X-ray photoelectron spectroscopy, and density functional theory calculations, we find that the cubic structure of ReO3 experiences multiple phase changes involving the correlated twisting of rigid octahedral subunits upon lithiation. This results in exceptionally poor long-term cyclability due to large strains upon lithiation, even though metallic character is maintained throughout. This suggests that phase transformations du...
Highlights
The reversibleinsertion of Li ions into densely packed intercalation hosts is a complex process of fundamental importance to rechargeable batteries
As positively charged ions move in and out of a structure, redoxactive transition-metal centers change their formal oxidation state and, in the process, adjust their bond lengths so as to maintain local charge neutrality.[1,2]. These complex structural distortions generate substantial strain in the lattice that manifests itself as large changes to the unit-cell volume during cycling, which can result in cracking of the electrode and delamination from the current collector, shortening the life of the battery.[3,4]
While the open framework of ReO3 has been heavily investigated in the past for its negative thermal expansion properties,[8,9] to our knowledge, there have been no studies that examine the role of structural flexibility on the performance of ReO3 as an intercalation electrode in functioning Li-ion batteries
Summary
The reversible (de)insertion of Li ions into densely packed intercalation hosts is a complex process of fundamental importance to rechargeable batteries. The metallic character of the starting phase might be expected to minimize lattice deformations resulting from polaron migration, we observe pronounced rotations of the Re octahedra during (de)insertion of Li. These tilting modes have a marked effect on the electronic structure of the material, eventually opening a small band gap in the fully lithiated Li2ReO3 end member.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
