Constructing a Protective Interface Film on Layered Lithium-Rich Cathode Using an Electrolyte Additive with Special Molecule Structure

Phenyl vinyl sulfone (PVS) as a novel electrolyte additive is used to construct a protective interface film on layered lithium-rich cathode. Charge-discharge cycling demonstrates that the capacity retention of Li(Li0.2Mn0.54Ni0.13Co0.13)O2 after 240 cycles at 0.5 C between 2.0 and 4.8 V (vs Li/Li+) reaches about 80% by adding 1 wt % PVS into a standard (STD) electrolyte, 1.0 M LiPF6 in EC/EMC/DEC (3/5/2 in weight). This excellent performance is attributed to the special molecular structure of PVS, compared to the additives that have been reported in the literature. The double bond in the molecule endows PVS with preferential oxidizability, the aromatic ring ensures the chemical stability of the interface film, and the sulfur provides the interface film with ionic conductivity. These contributions have been confirmed by further electrochemical measurements, theoretical calculations, and detailed physical characterizations.