High-Charge Density Polymerized Ionic Networks Boosting High Ionic Conductivity as Quasi-Solid Electrolytes for High-Voltage Batteries

Solid-state electrolytes are actively sought for their potential application in energy storage devices, especially lithium metal rechargeable batteries. However, one of the key challenges in the development of solid-state electrolytes is their lower ionic conductivity compared with that of liquid electrolytes (10–2 S cm–1 at room temperature), where a large gap still exists. Therefore, the pursuit of high ionic conductivity equal to that of liquid electrolytes remains the main objective for the design of solid-state electrolytes. Here, we show a series of high-charge density polymerized ionic networks as solid-state electrolytes that take inspiration from poly(ionic liquid)s. The obtained quasi-solid electrolyte slice displays an astonishingly high ionic conductivity of 5.89 × 10–3 S cm–1 at 25 °C (the highest conductivity among those of the state-of-art polymer gel electrolytes and polymer solid electrolytes) and ultrahigh decomposition potential, >5.2 V versus Li/Li+, which are attributed to the continuous ion transport channel formed by an ultrahigh ion density and an enhanced chemical stability endowed by highly cross-linked networks. The Li/LiFePO4 and Li/LiCoO2 batteries (3.0–4.4 V) assembled with the solid electrolytes show high stable capacities of around 155 and 130 mAh g–1, respectively. In principle, our work breaks new ground for the design and fabrication of the solid-state electrolytes in various energy conversion devices.