Tris (trimethylsilyl) borate (TMSB) as a cathode surface film forming additive for 5 V Li/LiNi0.5Mn1.5O4 Li-ion cells

Abstract The cycling performance of 5 V Li/LiNi 0.5 Mn 1.5 O 4 cells with 1.0 M LiPF 6 EC/DMC (1/2, v/v) with and without TMSB (0.2, 0.5, 1.0 and 2.0 wt.%) has been investigated. After 200 cycles, the cells with 1.0 wt.% TMSB have superior cycling performance with 95.3% capacity retention; while the cells with baseline electrolyte only maintain 84.4% capacity retention. The cells with 1.0 wt.% TMSB containing electrolyte have lower impedance after cycling at high voltage. In addition, the TMSB added cells show superior elevated temperature storage performance, the discharge capacity is 122.1 mAh g −1 and 109.9 mAh g −1 for the cells with and without TMSB after storage at 60 °C for a week at fully charged state, respectively. In order to further understand the effects of TMSB on LiNi 0.5 Mn 1.5 O 4 cathode upon cycling at high voltage, scanning electron microscopy (SEM), thermal-gravimetric analysis (TGA), transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectrometry (ICP-MS) analysis were conducted after the cycling test. The results indicate that the use of TMSB can form a stable and compact film on the surface of the LiNi 0.5 Mn 1.5 O 4 electrode, which inhibits the continuous decomposition of the electrolyte and reduces the dissolution of Mn and Ni from the bulk cathode material.