Tetrathiafulvalene as a Conductive Film-Making Additive on High-Voltage Cathode.

Tetrathiafulvalene (TTF) is investigated as a conductive film-making additive on an overlithiated layered oxide (OLO) cathode. When the OLO/graphite cell is cycled at high voltage, carbonate-based electrolyte without the additive decomposes continuously to form a thick and highly resistant surface film on the cathode. In contrast, TTF added into the electrolyte becomes oxidized before the electrolyte solvents, creating a thinner film on the cathode surface. This film inhibits further electrolyte decomposition through cycling and stabilizes the interface between the cathode and the electrolyte. The cells containing the OLO cathode with TTF-added electrolyte afforded enhanced capacity retention and rate capability, making TTF a prospective electrolyte additive for higher energy density lithium-ion cells.