A Thermochromic Polyoxovanadate with a 200,000-fold Conductivity Gain for Boosting Zinc-Ion Batteries Performance

Abstract

The performance of zinc-ion batteries is hampered by the cathode’s limited Zn2+ intercalation capacity and sluggish kinetics. Herein, we propose, for the first time, a thermochromic charge-separated strategy that simultaneously enhances capacity, rate performance, and cycling stability. We synthesized a new organic-inorganic hybrid thermochromic polyoxovanadate (POV), MV2[H2V10O28] (MV2V10, MV = methyl viologen cation) as cathode, which undergoes thermo-induced electron transfer from O to V, accompanied by color change from yellow to dark green, and the formation of an ultra-stable charge-separated state over one year, as well as a transition from insulator to semiconductor with 205,000-fold increase of electricity conductivity. After coloration, the capacity increased significantly by 57.3% from 172.8 to 271.8 mAh g-1 at 0.1 A g-1, while also exhibiting remarkable rate performance of 61.1% retention at a 100-fold higher current density, and cycling stability of 97.6% retention over 6000 cycles at a high current density of 10 A g-1. This work presents the first successful application of electron-transfer thermochromism to enhance ZIBs performance, offering a promising strategy for the development of advanced cathode materials.