Multi-electron transfer enabled by topotactic reaction in magnetite

Abstract

A bottleneck for the large-scale application of today’s batteries is low lithium storage capacity, largely due to the use of intercalation-type electrodes that allow one or less electron transfer per redox center. An appealing alternative is multi-electron transfer electrodes, offering excess capacity, which, however, involves conversion reaction; according to conventional wisdom, the host would collapse during the process, causing cycling instability. Here, we report real-time observation of topotactic reaction throughout the multi-electron transfer process in magnetite, unveiled by in situ single-crystal crystallography with corroboration of first principles calculations. Contradicting the traditional belief of causing structural breakdown, conversion in magnetite resembles an intercalation process—proceeding via topotactic reaction with the cubic close packed oxygen-anion framework retained. The findings from this study, with unique insights into enabling multi-electron transfer via topotactic reaction, and its implications to the cyclability and rate capability, shed light on designing viable multi-electron transfer electrodes for high energy batteries.

In situ Scanning/Transmission Electron Microscopy and Spectroscopy of Local Ionic Transport in Battery Electrodes

“…Contradicting the traditional belief of causing structural breakdown, conversion in FeF2 was found to resemble an intercalation process -proceeding via topotactic reaction with the anion framework retained throughout the process. Similar phenomenon was observed in oxides and other types of conversion electrodes [7]. These findings provide a new paradigm for re-interpretation of conversion reaction and, for practical application, shed light on designing viable conversion electrodes for high energy batteries [8].…”

Room-Temperature Manipulation of Magnetization Angle, Achieved with an All-Solid-State Redox Device

“…While the origin of irreversible processes can generally be attributed to various factors ( e.g . bulk/interface trapping sites, strain effect), we assigned the generation of the rock salt phase to the irreversibility of our redox device based on discussions in the literature and to the large irreversible Li + capacity, 5.1 × 10 21 cm –3 , observed in the study. ,− Please refer to Section S2.8 for details.…”

Dimensionality Concept in Solid‐State Reactions: A Way to Control Synthesis of Functional Materials at the Nanoscale

“…Insights into mechanisms of topotactic reactions, bond breaking and making are readily provided by electron microscopy techniques. [ 39,40 ] High‐resolution electron microscopy corroborates the 1D character of reaction (2). High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) images of layered SrSi 2 and SrAl 2 Si 2 on the same scale (Figure 2d) demonstrate the stability of the lattice parameter a and a significant expansion of the lattice along the c direction by formation of the [AlSi] 2 bilayer from the silicene monolayer.…”