Self-discharge suppression of 4.9 V LiNi0.5Mn1.5O4 cathode by using tris(trimethylsilyl)borate as an electrolyte additive

Abstract In this paper, tris(trimethylsilyl)borate (TMSB) is evaluated as an electrolyte additive for the self-discharge suppression of 4.9 V LiNi 0.5 Mn 1.5 O 4 cathode for lithium ion battery. The effect of TMSB on the surface properties of LiNi 0.5 Mn 1.5 O 4 is investigated via linear sweep voltammetry (LSV), cyclic voltammetry (CV), chronoamperometry (CA), charge–discharge test, electrochemical impedance spectra (EIS), scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometer (ICP-AES) and Fourier transform infrared spectroscopy (FTIR). It is found that the LiNi 0.5 Mn 1.5 O 4 cathode charged to 4.9 V (vs. Li/Li + ) suffers a serious self-discharge in 1 mol L −1 LiPF 6 –EC/DMC (1:2, in weight), which can be suppressed effectively by adding 1 wt.% TMSB into the electrolyte. After storage for 20 days, the voltage of the charged cathode decreases from 4.7 to 0.5 V (vs. Li/Li + ) in the additive-free electrolyte, while that remains almost unchanged in the TMSB-containing electrolyte. The self-discharge suppression of the charged LiNi 0.5 Mn 1.5 O 4 cathode results from the preferential oxidation of TMSB and the subsequent formation of a protective solid electrolyte interphase film, which prevents electrolyte decomposition and protects LiNi 0.5 Mn 1.5 O 4 from destruction.