The Effect of Trimethoxyboroxine on Some Positive Electrodes for Li-Ion Batteries

The effects of trimethoxyboroxine (TMOBX) on the electrochemical properties of some positive electrode materials for Li-ion batteries were studied. LiCoO2 (LCO), Li(Ni1/3Mn1/3Co1/3)O2 (NMC) and Li(Ni0.8Co0.15Al0.05)O2 (NCA) were chosen for study. Positive half cells containing different concentrations of TMOBX were studied using storage tests and dQ/dV analysis. These results suggest that TMOBX increases the rate of electrolyte oxidation and/or shuttle-type reactions at the positive electrode, especially at 60°C, but that there is no dramatic oxidation of TMOBX itself during the first cycles. NCA/NCA symmetric cells with different concentrations of TMOBX were constructed and tested. Capacity retention in symmetric NCA/NCA cells with small concentrations of TMOBX (0.3% and 1%) was equivalent to cells without TMOBX. Electrochemical impedance spectroscopy (EIS) tests showed that adding TMOBX decreased cell impedance when the concentration of TMOBX was no more than 1%. These results suggest TMOBX is a useful impedance reducing additive for Li-ion cells if it is incorporated at low concentration, such as 0.3%.