A high-entropy-designed cathode with V5+-V2+multi-redox for high energy density sodium-ion batteries

Na 3 V 2 (PO 4 ) 3 (NVP) is gifted with fast Na + conductive NASICON structure. But it still suffers from low electronic conductivity and inadequate energy density. Herein, a high-entropy modification strategy is realized by doping V 3+ site with Ga 3+ /Cr 3+ /Al 3+ /Fe 3+ /In 3+ simultaneously (i.e. Na 3 V 2- x (GaCrAlFeIn) x (PO 4 ) 3 ; x = 0, 0.04, 0.06, and 0.08) to stimulate the V 5+ =V 2+ reversible multi-electron redox. Such configuration highentropy can effectively suppress the structural collapse, enhance the redox reversibility in high working voltage (4.0 V), and optimize the electronic induced effect. The in -situ X-ray powder diffraction and in -situ electrochemical impedance spectroscopy tests efficaciously confirm the robust structural recovery and far lower polarization throughout an entire charge-discharge cycle during 1.6-4.3 V, respectively. Moreover, the density functional theory calculations clarify the stronger metallicity of high-entropy electrode than the bare that is derived from the more mobile free electrons surrounding the vicinity of Fermi level. By grace of high-entropy design and multi-electron transfer reactions, the optimal Na 3 V 1.7 (GaCrAlFeIn) 0.06 (PO 4 ) 3 can exhibit perfect cycling/rate performances (90.97%@5000 cycles@30 C; 112 mA h g -1 @10 C and 109 mA h g -1 @30 C, 2.0-4.3 V). Furthermore, it can supply ultra-high 185 mA hg -1 capacity with fantastic energy density (522 Wh kg -1 ) in half-cells(1.4-4.3 V), and competitive capacity (121 mA h g -1 ) as well as energy density (402 W h kg -1 ) in full-cells (1.6-4.1 V), demonstrating enormous application potential for sodium-ion batteries. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.