Architecting precise and ultrathin nanolayer interface on 4.5V LiCoO2 cathode to realize poly (ethylene oxide) cycling stability

The poly (ethylene oxide) (PEO) solid polymer electrolytes suffer from narrow electrochemical stability window and cannot match high voltage lithium cobalt oxide (LCO) cathode. Herein, an ultrathin Al2O3 nanolayer was uniformly deposited on the surface of LCO via powder atomic layer deposition (PALD) to realize poly (ethylene oxide) polymer electrolyte cycling stability. The PEO solid polymer electrolyte contains 20 % (w/w) lithium difluoro(oxalate)borate (LiDFOB) and 7.5 % (w/w) lithium titanium aluminum phosphate (LATP) with cellulose nonwoven as a support substrate. The electrolyte exhibitsionic conductivity of 1.2×10−4 S cm−1, an electrochemical stability window of 4.5 V (vs. Li+/Li) and lithium-ion transference number of 0.38. Al2O3@LCO/PEO-LiDFOB20%-LATP7.5%/Li cell at high cut-off 4.5 V delivered better initial discharge specific capacity of 178.5 mAh g−1 and achieved a capacity retention ratio of 81.6 % after 200 cycles under 0.1 C at 50 °C. Further analysis showed that Al2O3 layer served as stable a protective layer to suppress the generation of strong oxidative Co4+ and O– species and separate from the PEO solid polymer electrolyte, inhibiting the side reactions at the cathode-side interface. Therefore, architecting precise and ultrathin protective nanolayer interface on high voltage LCO cathode via PALD is conducive to cycling performance of solid polymer electrolyte.