Calorimetric Study of Mixed Phosphates Na4M3(PO4)2P2O7 (M = Mn2+, Fe2+, Co2+, Ni2+) to Evaluate the Electrochemical Trends

Jayanthi, K and Lochab, S and Barpanda, P and Navrotsky, A (2023) Calorimetric Study of Mixed Phosphates Na4M3(PO4)2P2O7 (M = Mn2+, Fe2+, Co2+, Ni2+) to Evaluate the Electrochemical Trends. In: Journal of Physical Chemistry C, 127 (24). pp. 11700-11706.

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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.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry C
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to the American Chemical Society.
Keywords:	Calorimetry; Cathodes; Metal ions; Phase stability; Phosphates; Sodium-ion batteries; Thermodynamics, Cathodes material; Electrochemical performance; Electrochemicals; High temperature oxide melt solution calorimetry; Ions diffusion; Na+ ions; Polyanionics; Sodium ion batteries; Thermodynamic phasis; Transition element, Sodium compounds
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	24 Jul 2023 13:03
Last Modified:	24 Jul 2023 13:03
URI:	https://eprints.iisc.ac.in/id/eprint/82634

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