The criticality of cobalt (Co) has been motivating the quest for Co-free positive electrode materials for building lithium (Li)-ion batteries (LIBs). However, the LIBs based on Co-free positive electrode materials usually suffer from relatively fast capacity decay when coupled with conventional LiPF6-organocarbonate electrolytes. To address this issue, a 1,2-dimethoxyethane-based localized high-concentration electrolyte (LHCE) was developed and evaluated in a Co-free Li-ion cell chemistry (graphite||LiNi0.96Mg0.02Ti0.02O2). Extraordinary capacity retentions were achieved with the LHCE in coin cells (95.3%), single-layer pouch cells (79.4%), and high-capacity loading double-layer pouch cells (70.9%) after being operated within the voltage range of 2.5-4.4 V for 500 charge/discharge cycles. The capacity retentions of counterpart cells using the LiPF6-based conventional electrolyte only reached 61.1, 57.2, and 59.8%, respectively. Mechanistic studies reveal that the superior electrode/electrolyte interphases formed by the LHCE and the intrinsic chemical stability of the LHCE account for the excellent electrochemical performance in the Co-free Li-ion cells.
Keywords: Co-free Ni-rich cathode; cycle life; electrode/electrolyte interphases; lithium-ion batteries; localized high-concentration electrolyte.