Lithium Bis(trimethylsilyl) Phosphate as a Novel Bifunctional Additive for High-Voltage LiNi_1.5Mn_0.5O₄/Graphite Lithium-Ion Batteries

The beneficial role of lithium bis(trimethylsilyl) phosphate (LiTMSP), which may act as a novel bifunctional additive for high-voltage LiNi1.5Mn0.5O4 (LNMO)/graphite cells, has been investigated. LiTMSP is synthesized by heating tris(trimethylsilyl) with tert-butoxide. cycle performance LNMO/graphite cells at 45 °C significantly improved upon incorporation (0.5 wt %). Nuclear magnetic resonance analysis suggests that the trimethylsilyl (TMS) group in can react hydrogen fluoride (HF), generated through hydrolysis hexafluorophosphate (LiPF6) residual water an electrolyte solution or via oxidative decomposition reactions to form TMS fluoride. Inhibition HF leads decrease concentration transition-metal ion-dissolution (Ni and Mn) from LNMO electrode, determined inductively coupled plasma mass spectrometry. In addition, generation superior passivating surface film derived on graphite suppressing further reductive well deterioration/reformation caused migrated transition metal ions, supported combination chronoamperometry, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy. Furthermore, LiTMSP-derived better ion conductivity resistance confirmed electrochemical impedance leading improvement rate cells. HF-scavenging film-forming effects LiTMPS are responsible less polarization enabling °C.