Enhancing cycle life of nickel-rich LiNi0.9Co0.05Mn0.05O2 via a highly fluorinated electrolyte additive - pentafluoropyridine

A highly fluorinated additive, pentafluoropyridine (PFP), is used here to enhance the interfacial stability of Ni-rich LiNi0.9Co0.05Mn0.05O2 (NCM90) cathode at a cut-off voltage 4.3 V vs. Li/Li+ 30 °C. The capacity retention NCM90||Li cell obviously improved from 72.3% 80.3% after 200 cycles 1C (1C = 180 mA g-1) when 0.2% PFP introduced into baseline electrolyte (1 mol L-1 LiPF6 in ethylene carbonate/diethyl carbonate). improvement electrochemical performance could be attributed formation compact and uniform interphase (CEI) layer enriched with F-containing polypyridine moieties LiF species on NCM90 particles. This CEI prevents side reactions between electrode hinders corrosion caused by HF attack. In addition, internal particle cracks somewhat suppressed robust CEI, thus prohibiting irreversible phase transformation better maintaining superior lithium-ion diffusion kinetics.