Understanding the Effect of Lithium Bis(oxalato) Borate (LiBOB) on the Structural and Electrochemical Aging of Li and Mn Rich High Capacity Li1.2Ni0.16Mn0.56Co0.08O2 Cathodes

Abstract

Li1.2Mn0.56Ni0.16Co0.08O2 synthesized by self-combustion reaction (SCR) was studied as a cathode material for advanced Li ion batteries in standard electrolyte solutions with and without Lithium Bis(oxalate) borate (LiBOB) at 30 and 45°C. When these cathodes were tested with LiBOB as an additive in solution, a capacity retention of 98% could be demonstrated during 50 cycles due to a unique stabilizing effect of this additive against 86% in standard electrolyte. Its presence in solutions suppresses the irreversible charge required to activate this cathode material. When cycled at 45°C, the capacity retention of Li1.2Mn0.56Ni0.16Co0.08O2 cathodes in LiBOB containing solutions may reach 97% during 50 cycles as compared to 78% in standard electrolyte solutions. The effect of LiBOB was examined by electrochemical (differential capacity plot and impedance) and structural analysis (Raman and TEM study). The presence of LiBOB in solutions leads to relatively low impedance of these cathodes. HRTEM and Raman spectral studies show that presence of LiBOB in solutions has bulk effect on this cathode material. While the initially present Li2MnO3 phase completely disappears upon cycling in standard solutions when the upper potential limit is above 4.5V, it does not fully disappear in solutions containing LiBOB.