Synthesis and Preparation of the Self-Healing Polyurethane Electrolytes for Lithium-Ion Battery Applications

Self-healing polyurethane electrolytes (SPUs) have been suggested as electrolyte materials to improve the lifetime and performance of lithium-ion batteries (LIBs). This study aims to investigate how the chemistry of the hard segment affects the mechanical and electrochemical performances of the SPUs in LIBs. For this purpose, isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and toluene diisocyanate (TDI) were used to synthesize SPUI, SPUH, and SPUT self-healing PUs, respectively. Two methods were used to prepare polymer electrolytes based on SPUs: coating of Celgard with SPUs and preparation of poly(vinylidene fluoride)(PVDF)/SPUs blend membranes. Electrochemical impedance spectroscopy (EIS) for SPUs-coated Celgard with SPUH, SPUT, SPUI, and SPUI/PVDF blend membranes showed ionic conductivities of 0.135, 1.8, 0.82, and 1.6 mS/cm, respectively. The electrochemical stability window of the electrolytes was measured to be in the range of 4.5–6 V. The LiFePO4 half-cells assembled using SPUI/PVDF blend membranes showed an improved capacity of around 140 mAh/g at 0.1 C. After 100 cycles of charge/discharge at 0.2 C, the capacity and Coulombic efficiency were measured to be around 129 mAh/g and 96.9%, respectively.