A 3.8 V Quaternary Ammonium-Based Dual-Ion Battery Enabled by a Conjugated Ladder Polymer.

Rechargeable batteries based on nonmetal charge carriers like NH recently have attracted intensive attention due to high safety, environmental friendliness, low cost, and fast kinetics. However, NH electrolytes suffer from a narrow electrochemical potential window, making it challenging to construct high-voltage and energy-dense devices. Here we report a quaternary ammonium (NR )-based dual-ion battery (DIB) working at a high voltage of 3.8 V, which was enabled by a conjugated ladder polymer poly(benzobisimidazobenzophenanthroline) (BBL) anode for NR storage and a graphite cathode for anion uptake. The BBL functions as an efficient NR host by carbonyl/enol transformation, delivering a high capacity of 120 mAh g, low average potential, high stability, and excellent rate performance. In the redox process, the electronic and ionic conductivities of BBL change periodically, accompanied by the formation of radical anion () and diradical dianion (). In combination with an anion-intercalation graphite cathode, the assembled graphite//BBL DIB exhibits a maximum energy/power density up to 232 Wh kg and 6865 W kg based on mass of graphite, superior rate performance, and high cycling stability without capacity attenuation. Our work demonstrates the feasibility of NR as cation carrier and its efficient host, which will inspire novel designs for high-performance nonmetallic energy storage devices.