Fluorine-free gel polymer electrolyte for lithium oxide-rich solid electrolyte interphase and stable Li metal batteries

The development of stable solid-electrolyte interphases (SEI) represents a fundamental challenge for Li-metal batteries. Although fluorinated reagents improve cycling performance through LiF-rich SEI formation, their associated costs and environmental impacts remain problematic. Here, we present a fluorine-free quasi-solid polymer electrolyte that generates an O/N -containing hybrid SEI with improved interfacial stability and Li+ transport kinetics. This unique SEI architecture preferentially directs Li deposition along the (200) crystallographic plane while enhancing charge-transfer efficiency. When implemented in Li | |LiNi0.8Co0.1Mn0.1O2 full cells, the fluorine-free gel polymer electrolyte enables a capacity retention of 84.7% over 800 cycles at 3 C. The fluorine-free gel polymer electrolyte system reported here exhibits improved high-rate performance compared to conventional fluorinated polymer electrolytes, providing a sustainable materials design paradigm for next-generation solid-state batteries. Stable solid-electrolyte interphases are crucial for lithium-metal batteries but often depend on costly and environmentally harmful fluorinated reagents. Here, the authors develop a fluorine-free polymer electrolyte that forms a highly stable O/N-rich SEI, significantly enhancing the battery cycling performance.