Thermodynamic data of a promising cathode material NaV6O15 and its synthesis/decomposition thermodynamic analysis

Sodium-ion batteries have emerged as a promising alternative to lithium-ion batteries due to their lower cost and similar electrochemical properties. The development of high-capacity and long-life electrode materials is crucial for advancing sodium-ion battery research. A significant amount of research has been conducted on the electrochemical properties of NaV₆O₁₅, however, there remains a dearth of data on its thermodynamic properties. Herein, NaV₆O₁₅ was synthesized using the solid-phase sintering method and thoroughly characterized. Thermodynamic data in the temperature ranges of 298.15–900 K, 15–303 K, and 573–873 K were determined using the Neumann-Kopp rule, low-temperature physical property measurement system, and MHTC 96 line, respectively. The heat capacity equation of NaV₆O₁₅ was derived and its enthalpy, entropy, and Gibbs free energy (298.15–800 K) were calculated. Moreover, the thermodynamics of NaV₆O₁₅-related formation and decomposition reactions were analyzed. The obtained heat capacity equation of NaV₆O₁₅ was $C_p=517.05524+0.08612T-1.25053\times 10^7{T}^{-2}\left(J/mol·K\right)\left(298.15\sim 873K\right)$. This study addresses the thermodynamic knowledge gaps of NaV₆O₁₅ and provides valuable insights for its preparation and decomposition in manufacturing processes.