Catalytical cobalt phthalocyanine/carbon nanotube cathode for high-performance zinc-iodine batteries

Zinc-iodine (Zn-I) batteries are promising energy storage devices because of relatively high capacity, non-flammable aqueous electrolyte, eco-friendliness and low cost. However, the shuttle effect of polyiodides has severely caused rapid capacity decay. Herein, an interconnected conductive cobalt phthalocyanine/carbon nanotubes (CoPc@CNT) cathode was prepared for adsorbing iodine species and further catalyzing the conversion of polyiodides to inhibit the shuttle effect in Zn-I batteries. In situ Raman tests combined with theoretical calculation demonstrate that CoPc decreases the overall conversion energy barriers and accelerates conversion of polyiodides to improve the cycling stability. As a result, Zn-I batteries deliver an ultra-long cycle stability for 9500 cycles with a high-capacity retention of 94% at a high current density of 20 mA cm−2. The Zn-I pouch battery assembled with CoPc-loaded carbon fiber cathode achieve a high specific capacity of 9.1 mAh cm−2. In addition, the designed dual-layer series Zn-I pouch battery normally operates with the charge/discharge voltage platform of 2.33 V. This work broadens the application of CoPc and explores a novel catalytic pathway for polyiodides conversion.