Stabilizing LiCoO2/Graphite at High Voltages with an Electrolyte Additive.

The energy density of commercial Li-ion batteries (LIBs) using LiCoO2 is adversely affected by the limited access to the Li stored in the CoO2 lattice, which is imposed partially by the instability of carbonate-based electrolytes at potentials higher than 4.5 V. In this work, we report a novel approach to fully utilize these extra Li via simultaneously stabilizing anode and cathode interfaces with a designed additive, 4-propyl-[1,3,2]dioxathiolane-2,2-dioxide (PDTD), which strongly coordinates with Co ions dissolved in electrolytes while decomposing to form protective interphases on both cathode and anode surfaces. The Co ions present in the electrolyte deposit on the anode in the form of a coordination complex with PDTD, avoiding the formation of Co metal that will catalyze the reduction decomposition of the additive-free electrolyte. The presence of PDTD in the electrolyte enables a higher charging potential of 4.45 V for LiCoO2/graphite cells, which significantly improves the energy density and cycling stability of this cathode chemistry that has already been used extensively in commercial LIBs.