Electrolyte Additives for Reducing the Irreversible Capacity Loss, Impedance and Polarization of a Doped LiCoPO_4 Cathode

摘要

High voltage cathode materials show promise for improving the specific energy of the state-of-the-art lithium ion battery. One notable cathode material that displays a discharge voltage of ～4.8V, and has the potential to improve the specific energy to ～802Wh/kg, is the olivine-structured LiCoPO_4. A significant issue, however, that has plagued LiCoPO_4-based systems is the irreversible electrolyte decomposition that occurs at the electrolyte/electrode interface at higher voltages. Electrolyte additives have long been used to improve the passivation layer on the anode, but little is known about the importance of electrolyte additives on the cathode surface. The following study demonstrates a design of experiment (DOE) approach for optimizing the electrolyte additive concentration. The optimized electrolyte improves the cycle life and specific capacity of the cell, while reducing the interfacial impedance. The resulting full-cell containing the optimized electrolyte demonstrates a specific energy that is improved 60% over a full-cell containing the standard electrolyte.