A bipolar metal phthalocyanine complex for sodium dual-ion battery

Abstract

Dual-ion batteries (DIBs) have attracted immense interest as a new generation of energy storage device due to their low cost, environmental friendliness and high working voltage. However, developing DIBs using organic compounds as active electrode materials is in its infancy. Herein, we first report a bipolar and self-polymerized Cu phthalocyanine (CuTAPc) as an electrode material for sodium-based DIBs (SDIBs). Benefitting from the bipolar property, CuTAPc could serve as the cathode or anode material to construct metal sodium-based or metal sodium-free SDIB (cell 1 or 2) by coupling with sodium anode or graphite cathode, respectively. As a result, cell 1 displays a high discharge capacity of 195.7 mAh g−1 at 50 mA g−1 and a high reversible capacity of 57 mAh g−1 over 2500 cycles at 1 A g−1, and cell 2 shows a high energy density of 324 Wh kg−1 and a high power density of 7481 W kg−1. Subsequently, the proposed binding mechanism and the bipolar reactivity of CuTAPc have been revealed by the detailed reaction kinetic analysis and ex-situ techniques as well as the density functional theory (DFT) calculations. This work could open a pathway to develop the advanced SDIBs constructed by elemental abundant and environmentally friendly organic materials.