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.