1,4-Phenylene diisocyanate (PPDI)-containing low H2O/HF and multi-functional electrolyte for LiNi0·6Co0·2Mn0·2O2/graphite batteries with enhanced performances

Abstract

Lithium-ion batteries (LIBs) with high-nickel ternary material cathode can provide a high specific capacity but are more sensitive to the H2O/HF contents and functional additives in the electrolyte. In this work, 1,4-phenylene diisocyanate (PPDI) is developed as an H2O/HF scavenger and film-forming electrolyte additive to enhance the performances of pouch LiNi0·6Co0·2Mn0·2O2 (NCM622)/graphite batteries. Compared with batteries containing the blank electrolyte, the electrochemical performances of batteries with the PPDI-containing electrolyte can be significantly improved. Thereinto, after 600 cycles at room temperature (25 °C) and 300 cycles at high temperature (45 °C), the capacity retentions for the batteries with the PPDI-containing electrolyte are 84.9% and 81.3% at 1C, while the rates for the batteries with the blank electrolyte are only 29.3% and 14.4%, respectively. With the aid of theory calculations and spectroscopic characterization, the reasons behind the performance enhancement are elucidated, and the reaction mechanism of PPDI and H2O/HF is proposed. It is demonstrated that PPDI can scavenge H2O/HF in the electrolyte and form stable and highly conductive films on two electrodes to stabilize NCM622 and improve battery performances. Besides the functionalized electrolyte, this work can also inspire new ideas to develop functionalized electrolytes for high-performance NCM622-based LIBs.