Single vs. Blended Electrolyte Additives: Impact of a Sulfur-Based Electrolyte Additive on Electrode Cross-talk and Electrochemical Performance of LiNiO2||Graphite Cells

Lithium nickel oxide (LNO) is an attractive positive electrode active material for lithium ion batteries (LIBs) due to its high reversible specific capacity and absence of cobalt. Nevertheless, it is prone to structural instabilities that lead to rapid capacity fading, safety concerns and shows in average a lower voltage than mixtures with cobalt, limiting its applicability to date. Herein we introduce the sulfur-based electrolyte additive, benzo[d][1,3,2]dioxathiole 2,2-dioxide (DTDPh), to stabilize the LNO electrode and study its effects on interphase compositions by means of complementary electrochemical and spectroscopic techniques. Obtained results demonstrate an improved galvanostatic cycling performance in terms of cycle life and achievable specific discharge capacity that significantly outperform the common film-forming additive vinylene carbonate (VC). The cycle life was increased from 102 to 147 cycles compared to the baseline electrolyte and the accumulated discharge energy until end of life was increased by 45%. This study furthermore provides strong evidence of a significant cross-talk and negative interplay between DTDPh and VC when both are present in the electrolyte formulation. Mechanistic consideration based on density functional theory (DFT) calculations suggest the formation of mobile poly(VC) species, which is supported by the results of post mortem analysis of the resulting interphases.