A high-energy dual-ion battery based on chloride-inserted polyviologen cathode and LiCl/DMSO electrolyte

To improve the energy density of dual-ion batteries (DIBs), for the first time we employ a Cl--insertable p-type polymer, poly(butyl viologen dichloride) (PBV-Cl2), as cathode material, and low-cost LiCl/DMSO (dimethyl sulfoxide) solution as electrochemically favorable electrolyte. Benefiting from the highest reversible capacity of the PBV-Cl2 cathode among all p-type polymers (183 mAh g-1 based on the weight involving anion), and greatly lowered Li+/Li potential (by 0.5 V) in DMSO compared to that in conventional ester solvents, the Li-PBV-Cl2 DIB achieves the highest actual energy density of 470 Wh kg-1. After adding fluoroethylene carbonate (FEC) additive in the electrolyte for better Li anode compatibility, it also exhibits an excellent cycling stability (88% after 300 cycles) and a superior rate capability (75% at 5000 mA g-1). The concepts of Cl- charge carrier, polyviologen cathode, and LiCl-based electrolyte provide significant insights for the development of high-energy, low-cost, and sustainable DIBs.