ARC Studies of the Effects of Electrolyte Additives on the Reactivity of Delithiated Li1-x[Ni1/3Mn1/3Co1/3]O2 and Li1-x[Ni0.8Co0.15Al0.05]O2 Positive Electrode Materials with Electrolyte

Abstract

Using accelerating rate calorimetry (ARC), the effect of lithium bis(oxalato)borate (LiBOB), vinylene carbonate (VC) and succinonitrile (SN) electrolyte additives and LiPF6 salt on the reactivity between electrolyte and charged positive electrode material has been investigated. The ARC samples were made with varying concentrations of LiBOB, VC and SN as electrolyte additives and delithiated Li1-x[Ni1/3Mn1/3Co1/3]O2 (NMC) and Li1-x[Ni0.8Co0.15Al0.05]O2 (NCA) charged to 4.2 V as positive electrode materials. The thermal stability of NMC decreases slightly with the addition of the electrolyte additives but the thermal stability of NCA increases with the addition of the electrolyte additives except in the case of VC. The thermal stability of NMC decreases as the concentration of LiPF6 increases while the thermal stability of NCA increases as the concentration of LiPF6 increases. The ARC results shown here suggest that additives and LiPF6 salt can play a different role in thermal stability depending on the positive electrode material. Therefore careful considerations about safety are required to incorporate new electrolyte additives in Li-ion cells.