Abstract
The performance of zinc-ion batteries is hampered by the cathode's limited Zn(2+) intercalation capacity and sluggish kinetics. Herein, we propose, for the first time, a thermochromic charge-separation strategy that simultaneously enhances capacity, rate performance, and cycling stability. We synthesized a new organic-inorganic hybrid thermochromic polyoxovanadate (POV), MV(2)[H(2)V(10)O(28)] (MV(2)V(10), MV = methyl viologen cation) as a cathode, which undergoes thermo-induced electron transfer from O to V, accompanied by a color change from yellow to dark green, and the formation of an ultra-stable charge-separated state lasting over one year, as well as a transition from an insulator to a semiconductor with a 205 000-fold increase in electrical 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 with 61.1% retention at a 100-fold higher current density, and cycling stability with 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 ZIB performance, offering a promising strategy for the development of advanced cathode materials.