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.
Highlights
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
Intercalation-type electrode materials are commonly employed in commercial lithium-ion batteries (LIBs), as they accommodate Li via topotactic transformation, conducive to small structural change over cycling1
The use of single crystal in this study enabled us to reveal the crystallographic correlation among all the involved phases, and the co-operative migration of Li and Fe ions within the ccp O-anion framework
Summary
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. Intercalation-type electrode materials are commonly employed in commercial lithium-ion batteries (LIBs), as they accommodate Li via topotactic transformation, conducive to small structural change over cycling. Intercalation-type electrode materials are commonly employed in commercial lithium-ion batteries (LIBs), as they accommodate Li via topotactic transformation, conducive to small structural change over cycling1 Their capacity is low, limited by one or less electron transfer per redox center, which has been a bottleneck for the large-scale applications. In the particular systems that undergo MET reaction, multi-phase transformations occur within nanosized domains, which have often been complicated by the use of polycrystalline materials, since the random orientation of constituent crystallites obscures the crystallographic relationship between the involved intermediates as they develop
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