Organic-inorganic composite SEI for a stable Li metal anode by in-situ polymerization

Li metal anode is regarded as the ultimate anode material for high-energy-density batteries. However, the severe side reaction with the electrolyte calls for a scientific interface engineering. Here, we develop an organic-inorganic composite SEI for Li metal anode which is formed by the in-situ polymerization of precursor mainly composed of poly (ethylene glycol) diacrylate (PEGDA) and lithium difluoro(oxalato)borate (LiDFOB). The artificial SEI contacts intimately with Li anode due to the formation of lithiated polymer, and possesses a good stability with LiF formed. Besides, good flexibility and high mechanical strength enable the organic-inorganic composite SEI to adapt the volume change during cycling and protect Li metal anode continuously. Benefiting from the artificial SEI, the Li || LiNi0.8Co0.1Mn0.1O2 (NCM811) cells maintain a capacity above 80 mA h g−1 even after 500 cycles at 0.5 C, and the Li || Li symmetrical cells achieve a stable long-term cycling over 700 h (0.5 mA cm−2, 1 mA h cm−2) with a small overpotential of around 60 mV. This artificial SEI provides a facile and effective strategy for next-generation Li metal batteries with better safety and cycling performance.