Fabrication of porous imidazole polymerized ionic liquids with fast ion diffusing kinetics for super lithiation anode materials in lithium-ion batteries

Abstract

Porous imidazole polymerized ionic liquids (PILs-Im) with fast Li⁺ diffusion kinetics and numerous molecular pores have been used as anodes in lithium-ion batteries for the first time. In situ FTIR, ex situ XPS and DFT calculations indicate that the N atoms in aromatic rings and methylene C react with Li⁺ to form N–Li and C–Li bonds, realizing a specific capacity of 846.6 mA h g⁻¹ at 100 mA g⁻¹ with super lithiation in Li_0.5(C/N). PILs-Im also exhibit excellent cycling stability (598.7 mA h g⁻¹ at 1.0 A g⁻¹) after 500 cycles, and a superior rate capability of 165 mA h g⁻¹ at 10 A g⁻¹. The excellent lithium storage performance could be attributed to the ionic skeleton allowing fast Li⁺ diffusion, abundant micropores facilitating the filtration of liquid electrolyte, and large cross-linking system with strong endurance to the volume variation of Li⁺ insertion. Polymerized ionic liquids give a new route to provide traditional electrodes with a high Li⁺ diffusion coefficient.