Realizing a high-performance LiNi0.6Mn0.2Co0.2O2/silicon–graphite full lithium ion battery cell via a designer electrolyte additive

Abstract

An optimized dosage of (2-cyanoethyl)triethoxysilane (TEOSCN), is investigated as the electrode/electrolyte interface (EEI) modulating electrolyte additive to improve electrochemical performance of LiN_0.6Mn_0.2Co_0.2O₂(NMC622)/silicon(Si)–graphite(Gr) battery cells at a high temperature (45 °C). The addition of 1 wt% of TEOSCN to 1 M LiPF₆ in EC:DEC + 5 wt% FEC/2 wt% VC electrolyte is found to significantly improve the long-term cyclability, capacity retention and coulombic efficiency of NMC622/Si–Gr cells at 45 °C. Pouch cells cycled in a nitrile-functionalized silane bearing electrolyte show superior capacity retention (∼75.95%) compared to those with FEC/VC (∼8.05%) and without additives (EC:DEC, ∼19.23%) electrolytes at the 364^th cycle. Chemical mimicking and X-ray Photoelectron Spectroscopy (XPS) analysis proved that the enhanced electrochemical performance is attributed to the formation of –CN reduction/oxidation induced robust EEI layers, both on the anode and cathode compartments, thus mitigating the escorted prevailing challenges. This work provides a highly promising electrolyte additive enabling the large-scale commercial deployment of Si-containing high-energy lithium-ion full cell batteries.