Abstract
Mixed polyanionic compounds have been studied extensively as viable cathode materials for sodium-ion batteries. Mixed phosphates, Na4M3(PO4)2P2O7 (M = Mn2+, Fe2+, Co2+, Ni2+), provide a low barrier for Na-ion diffusion, being advantageous in comparison to phosphates and pyrophosphates. The reported order of sodium extraction is ambiguous and remains unclear. Despite being structurally similar, electrochemical performance differs for all four analogues with different degrees of (de)sodiation, according to the transition element present. Here, high-temperature oxide melt solution calorimetry has been used to establish the relation between thermodynamic phase stability and observed capacity for this series of mixed phosphates. Thermodynamic phase stability largely depends on the kind of structure, type of bonding, and size of the cations present. So, according to our results, the thermodynamic phase stability follows the order Na4Mn3(PO4)2P2O7 > Na4Fe3(PO4)2P2O7 > Na4Co3(PO4)2P2O7 > Na4Ni3(PO4)2P2O7. The thermodynamic studies serve as guidelines for the selection of compositions with the potential for fabricating advanced cathode materials with maximum performance.
| Original language | English |
|---|---|
| Pages (from-to) | 11700-11706 |
| Number of pages | 7 |
| Journal | Journal of Physical Chemistry C |
| Volume | 127 |
| Issue number | 24 |
| DOIs | |
| State | Published - Jun 22 2023 |
Funding
This manuscript has been authored by UT-Battelle, LLC, under Contract No. DEAC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Acknowledgments K.J. and A.N. acknowledge the U.S. Department of Energy Office of Basic Energy Sciences, Grant DE-SC0021987, for calorimetric measurements and thermodynamic analysis. The current work was partially supported by the Technology Mission Division (DST, Government of India) under the Materials for Energy Storage (MES-2018) program (DST/TMD/MES/2k18/00217). S.L. thanks Dr. S.P. Adiga for hosting him at Samsung R&D Centre Bangalore during the project work. S.L. is grateful to the Ministry of Human Resource Development (MHRD, Government of India) for financial support. P.B. is grateful to Alexander von Humboldt Foundation (Bonn, Germany) for a 2022 Humboldt fellowship for experienced researchers.