Bonding Heterogeneity Leads to Hierarchical and Ultralow Lattice Thermal Conductivity in Sodium Metavanadate.

Abstract

Sodium metavanadate (NaVO3) is a promising low-cost candidate as a cathode material for sodium-ion batteries (SIBs) owing to its high cycle performance. Its thermal transport, although being a central factor limiting its practical applications, remains scarce. Herein, we comprehensively investigate the intrinsic thermal transport properties of the two phases of NaVO3 using the unified theory. Importantly, we identify a hierarchical thermal transport mechanism in NaVO3 and the significant contribution of diffusive thermal transport. With the combined two channels, we reveal that NaVO3 has the anisotropic and ultralow thermal conductivity κ, which is derived from the bonding heterogeneity with the coexistence of strong V-O bonds and weak Na-O bonds, implying the possibility of engineering the κ of SIBs by spatially tuning the sodium concentration distribution. Our work establishes a fundamental understanding of the intrinsic thermal transport of NaVO3 and provides guidance toward designing tunable thermal conductivity cathode materials for SIBs.