Published Research - Department of Chemistry

 

Date of this Version

2021

Citation

Angewandte Chemie 2021, 133, 10144 – 10151, and

Angew. Chem. Int. Ed. 2021, 60, 10056 – 10063

doi.org/10.1002/anie.202100730

doi.org/10.1002/ange.202100730

Comments

This is an open access article under the terms of the Creative Commons Attribution License,

International Edition attached below as an additional file.

Abstract

Oxygen redox in Li-rich oxides may boost the energy density of lithium-ion batteries by incorporating oxygen chemistry in solid cathodes. However, oxygen redox in the bulk usually entangles with voltage hysteresis and oxygen release, resulting in a prolonged controversy in literature on oxygen transformation. Here, we report spectroscopic evidence of peroxo species formed and confined in silicate cathodes amid oxygen redox at high voltage, accompanied by Co2+/Co3+ redox dominant at low voltage. First-principles calculations reveal that localized electrons on dangling oxygen drive the OO dimerization. The covalence between the binding cation and the O-O dimer determines the degree of electron transfer in oxygen transformation. Dimerization induces irreversible structural distortion and slow kinetics. But peroxo formation can minimize the voltage drop and volume expansion in cumulative cationic and anionic redox. These findings offer insights into oxygen redox in the bulk for the rational design of high-energy-density cathodes.

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