Bipolar ionomer electrolytes with desirable self-discharge suppression for supercapacitors

Supercapacitors based on electric double layers are prone to serious self-discharge due to electrolyte ion desorption and the resulting energy loss severely limits the application range of supercapacitors. Rational design of polymer electrolyte systems to address this problem shows considerable generality and high feasibility. Herein, we reported a quasi-solid-state bipolar ionomer electrolyte prepared by an in-situ layer-by-layer ultraviolet-curing method, which has an integrated Janus structure with an intermediate binding layer. Based on the synergistic effect of confining impurity ions by ionizable groups and electrostatic repulsion to stabilize the electric double layers and superimposing synergies on both sides, the assembled device not only possesses ideal supercapacitor characteristics, but also exhibits an ultra-high voltage retention of 71% after being left to stand for 100 h after being fully charged. Furthermore, through the quasi-in-situ energy dispersive X-ray spectroscopy linear scanning, the characteristics of ion diffusion in this ionomer electrolyte are revealed, suggesting its correlation with self-discharge behavior.