![Author ORCID: We display the ORCID iD icon alongside authors names on our website to acknowledge that the ORCiD has been authenticated when entered by the user. To view the users ORCiD record click the icon. [opens in a new tab]](https://chemrxiv.org/engage/assets/public/chemrxiv/images/logos/orcid.png)
Abstract
Micrometer-size particles of entropy-stabilized transition metal-based high entropy oxide, (MgCoNiCuZn)O, has demonstrated long-term cycling stability against lithium-ion battery, a feat that has only been achieved with nanometer-size transition metal binary oxides. This electrochemical performance has been attributed to the entropy stabilization effect observed in this material. This work demonstrates that entropy stabilization might not play a role in the electrochemical performance of this compound as previously suggested, by comparing the electrochemical data of two medium entropy materials, (MgNiCuZn)O and (CoNiCuZn)O, with that of the high entropy material. In addition, the mechanism of lithium interaction with these materials is still poorly understood, in part owing to the difficulties in characterizing structure at the nanoscale. Solid-state operando NMR/derivative operando techniques are used to demonstrate that the lithiation of these compounds proceeds via a partially reversible conversion-type reaction involving the reduction of the transition metals cations to their metallic form during lithiation and the oxidation of these individual metal particles to their oxides form, losing the initial single-phase compound after the first lithiation cycle. The NMR results also show that the conductive carbon black used as an electronic conductor can store a significant amount of charge at low voltage, indicating that it is a major contributor to the additional observed in these entropy-stabilized oxides and in transition metal salts.
Supplementary materials
Title
The Role of Entropy on the Electrochemistry of Entropy-Stabilized Oxides and Their Lithium Storage Mechanism
Description
This work demonstrates that entropy stabilization might not play a role in the electrochemical performance of this compound as previously suggested, by comparing the electrochemical data of two medium entropy materials, with that of the high entropy material. The mechanism of lithium interaction with these materials is still poorly understood, in part owing to the difficulties in characterizing structure at the nanoscale. Operando NMR/dOp techniques are used to demonstrate that the lithiation of these compounds proceeds via a partially reversible conversion-type reaction involving the reduction of the transition metals cations to their metallic form during lithiation and the oxidation of these individual metal particles to their oxides form. The NMR results also show that the conductive carbon black can store a significant amount of charge at low voltage, indicating that it is a major contributor to the additional capacity observed in these entropy-stabilized oxides and in transition metal salts.
Actions
