Revealing the Origin of Transition-Metal Migration in Layered Sodium-Ion Battery Cathodes: Random Na Extraction and Na-Free Layer Formation

Publication Name

Angewandte Chemie - International Edition

Abstract

Cation migration often occurs in layered oxide cathodes of lithium-ion batteries due to the similar ion radius of Li and transition metals (TMs). Although Na and TM show a big difference of ion radius, TMs in layered cathodes of sodium-ion batteries (SIBs) can still migrate to Na layer, leading to serious electrochemical degeneration. To elucidate the origin of TM migration in layered SIB cathodes, we choose NaCrO2, a typical layered cathode suffering from serious TM migration, as a model material and find that the TM migration is derived from the random desodiation and subsequent formation of Na-free layer at high charge potential. A Ru/Ti co-doping strategy is developed to address the issue, where the doped active Ru is first oxidized to create a selective desodiation and the doped inactive Ti can function as a pillar to avoid complete desodiation in Ru-contained TM layers, leading to the suppression of the Na-free layer formation and subsequent enhanced electrochemical performance.

Open Access Status

This publication is not available as open access

Funding Number

M17943

Funding Sponsor

National Natural Science Foundation of China

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Link to publisher version (DOI)

http://dx.doi.org/10.1002/anie.202216174