Dual-salts of LiTFSI and LiODFB for high voltage cathode LiNi0.5Mn1.5O4

The LiNi0.5Mn1.5O4 has been investigated as promising because of its high operating voltage (4.7 V vs. Li+/Li) and decent specific capacity. Despite these advantages, however, the market penetration of this material was significantly hindered by the lack of proper electrolytes that can work stably up to 5 V. To achieve better cycling stability, mixed salts of lithium bis (trifluoromethanesulfonylimide) (LiTFSI) and lithium difluoro (oxalate) borate (LiODFB) are used in LiNi0.5Mn1.5O4-based batteries to replace the lithium hexafluoride phosphate (LiPF6) salt in non-aqueous electrolytes. The SEM and CV data indicate that the corrosion to Al current collector caused by LiTFSI-based electrolytes under high voltage (similar to 5 V vs. Li+/Li) can be largely reduced by adding LiODFB into LiTFSI-based electrolytes. And a boron-based passivation layer from the oxidative decomposition of LiODFB to suppress the corrosion based on the XPS tests results. In addition, the LiTFSI0.5-LiODFB0.5-based electrolyte has better cycling stability and rate capability for LiNi0.5Mn1.5O4-based cells than LiPF6-based electrolyte.