Quasi-solid polymer electrolyte with autonomous self-healing capabilities for lithium metal batteries

Quasi-solid polymer electrolytes (QSPE) are expected to lead to technological breakthroughs in the development of Li metal batteries, implementing functional properties (e.g., power density, safety, stability). QSPEs are systems where small amounts of liquid phase are chemically/physically entrapped into solid polymer matrix, resulting in effective combination between liquid-like transport and solid-like mechanical behaviour. The presence of a polymer backbone allows the introduction of smart functionalities, such as self-healing units, capable to repair spontaneously physical damages from mechanical stress. Here, we produce new QSPEs with self-healing functionalities whose repairing mechanism involves dynamic multiple hydrogen bonding. These electrolytes consist of: i) a blend of a fluropolymer (mechanically strong network) and ureidopyrimidinone-telechelic (repairing functionality); ii) dual-salt liquid electrolyte. QSPE including 9 wt% of liquid electrolyte shows outstanding ionic conductivity exceeding 1 mS cm−1 at 30 °C, wide electrochemical stability above 5.2 V and great mechanical strength, despite the presence of small liquid fraction. These properties are paired to excellent self-healing performances capable to recover conductivity decays and internal short circuits caused by dendrite penetration across the electrolytes. The self-healing QSPE was tested in LFP/Li cell at 40 °C. Higher thermal resistance against thermal abuse and improved functional performances were delivered compared to the liquid electrolyte.