Semi-interpenetrating double network quasi-solid electrolyte with pre-reduced artificial cathode electrolyte interphase for safe and high-performance lithium metal batteries

Poly (ionic liquid) (PIL) has emerged as a promising polymer substrate for solid electrolytes in lithium metal batteries due to its high ionic selectivity, excellent thermal stability, and compatibility with in situ polymerization processes. However, the limited ionic conductivity of PIL, primarily attributed to its restricted free volume and rigid polymer segments at room temperature, poses a significant challenge to its broader application on solid-state batteries. Herein, poly(1,3-dioxolane) (PDOL) is incorporated into PIL as a high-ionic-conductivity component to fabricate a semi-interpenetrating double network quasi-solid electrolyte (SIDN-QSE). The introduction of PDOL soft chains markedly improves the ionic conductivity of PIL-based quasi-solid electrolytes while preserving the advantageous properties of PIL, including its mechanical strength and thermal stability. Furthermore, the precursor containing ionic liquid with high dielectric constant induces the formation of the anions gathering inner Helmholtz plane (IHP) nearing the surface of the cathode, followed by the construction of the artificial cathode interface through the pre-reduction process. As a result, LiFeO 4 |SIDN-QSE|Li batteries achieve a high capacity retention of 70.4 % after 700 cycles at 2 C and 30 °C. Additionally, pouch cells incorporating the SIDN-QSE demonstrate excellent safety performance, withstanding mechanical stress tests such as bending, cutting, and piercing without compromising functionality.