A composite gel polymer electrolyte by incorporating modified POSS endowing inorganic-rich SEI formation and stable cycle life for lithium metal batteries

Low density and high theoretical capacity lithium metal anode is an ideal material to replace graphite anode. However, key issues such as the instability of the solid electrolyte intermediate phase (SEI), the degradation of the liquid electrolyte, and the growth of dendrites still hinder its practical application. Here, a composite gel polymer electrolyte with a well Li+ solvated structure was prepared by incorporating PEG-modified POSS. The introduction of modified POSS not only enhanced the structural strength of GPE, but also induced the formation of Li+ solvated sheath structures that dominated by SSIPs/CIPs and AGGs. The well solvated structure of Li+ is beneficial for the generation of stable LiF-rich SEIs to resist the lithium dendrites, improving the anti-oxidation ability of GPE and the cycling performance of the LMBs. Benefiting from the uniform and stable SEIs, the capacity retention rate of the composite GPE-based LiFePO4 full cell can be high up to 95.7 % after 300 cycles at 0.2C and 87.9 % after 400 cycles at 0.5C. This work provides valuable ideas for the study of organic–inorganic composite gel electrolytes.