Diphenyl diselenide as a bifunctional electrolyte additive in a high-voltage LiNi0.8Mn0.1Co0.1O2/graphite battery

• Diphenyl diselenide (DPDS) is introduced as a bifunctional electrolyte additive. • The CEI and SEI from DPDS protects Ni-rich NMC811 and graphite from parasitic side reaction • DPDS enables long-cycle stability of high-voltage LiNi 0.8 Mn 0.1 Co 0.1 O 2 /graphite battery • Working mechanism of DPDS is proposed by computational and experimental measurement. To increase the practical energy density and capacity of high-nickel cathode materials, it is crucial to develop a novel electrolyte additive that can enhance the unstable electrolyte/electrode interface over a wide operating voltage range. In this study, diphenyl diselenide (DPDS) is selected as a bifunctional electrolyte additive for high-voltage LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811)/graphite batteries, considering the energy levels of its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). DPDS is oxidized and reduced prior to the decomposition of ethylene carbonate (EC) and diethyl carbonate (DEC), forming protective layers on both electrode surfaces. The DPDS-driven layers prevent parasitic reactions, maintain the structural stability of electrodes, and reduce active lithium loss. As a result, in the high voltage window of 2.8–4.5 V, DPDS enhances the capacity retention of NMC811/graphite batteries from 68.0% to 82.0% after 200 cycles at 1C. This paper provides an understanding of the DPDS operating principle in high voltage NMC811/graphite full cells to achieve high energy density. A very small amount of electrolyte additive diphenyl diselenide forms stable CEI on the NMC 811 surface, preventing electrolyte decomposition, TM dissolution, and microcracking.