Revealing the interfacial kinetic mechanisms in high-entropy doped Na${}_3$V${}_2$(PO${}_4$)${}_3$ through electrochemical investigation and distribution of relaxation times

Abstract

We designed a high-entropy doped NASICON cathode, Na${}_3$V${}_{1.9}$(CrMoAlZrNi)${}_{0.1}$(PO${}_4$)${}_3$ and investigate its electrochemical performance for sodium-ion batteries (SIBs) to understand the diffusion mechanism including distribution of relaxation times analysis of interfacial kinetics. This trace doping induces high-entropy mixing at the vanadium site, tuning the lattice and enhancing specific capacity, activating V${}^{4+}$/V${}^{5+}$ redox couple 3.95~V. Interestingly, it delivers a reversible capacity of 119~mAh~g${}^{-1}$ at 0.1~C, and demonstrate excellent stability of 68\% after 1000 cycles at 10~C. The calculated diffusion coefficient values are found within the range of \(10^{-11}\)--\(10^{-13}~\mathrm{cm^2\,s^{-1}}\). The systematic investigation of temperature and voltage-dependent impedance data using the distribution of relaxation times provides deeper insights into the underlying charge-transfer and transport processes. The full cells with hard carbon delivers 326~Wh~kg${}^{-1}$ (with respect to cathode mass) at $\approx$3.2~V and retained $\sim$79\% capacity after 100 cycles at 2~C. Our study opens new avenues for developing high-entropy doped cathodes for enhanced structural stability, extended redox activity, and optimized electrochemical kinetics for practical implementation of SIBs.

submitted