The Impact of the Cathode Electrolyte Interface Evolution and Formation on Ni-Rich Cathodes Stability and Kinetics

Extended-range electric vehicles, the proliferation of portable electronics, and the demand for a stable supply of battery materials have pushed lithium-ion cathode development away from cobalt and towards nickel-based oxides. LiNiO2 (LNO) promises high voltage and capacity to meet these needs but suffers from significant stability issues due to LNOs' continuous cathode electrolyte interface (CEI) growth and particle microcracking. To better understand the fundamental reasons for such phenomena, single-crystal LNO (SC-LNO) is applied as a platform to avoid the grain boundaries that are part of the well-established degradation mechanism of polycrystalline LNO (PC-LNO). We found that the CEI of SC-LNO formed within ten cycles and was stable in later cycles with no continuous growth. There was also minimal particle cracking, even when cycled above the voltage that triggers microcracking. PC-LNO, by comparison, experienced constant growth of the CEI and pulverization of secondary particles after 100 cycles. These findings support a deeper understanding of the CEI without the interference of grain boundaries for the future development of Ni-rich cathodes.