Electrochemical response in aprotic ionic liquid electrolytes of TiO2 anatase anodes based on mesoporous mesocrystals with uniform colloidal size

Abstract

Mesocrystals (superstructures of crystallographically-oriented inorganic nanocrystals) represent sophisticated configurations generated from biomineralization processes, and an example of nonclassical crystallization mechanisms. Being the closest relatives to single-crystals at the nanoscale, porous mesocrystals are considered as ideal configurations to improve functional properties, and to correlate structural and textural features with materials functionality. Here we show that TiO2 anatase mesoporous colloidal mesocrystals, synthesized by a self-assembly/seeding method, can be easily processed as active materials in anode composites. These anode composites can be efficiently infiltrated during battery operation with safe aprotic ionic liquid electrolytes down to the mesoporosity of mesocrystals (3–4 nm), and operate over a wider temperature window than organic carbonates. For example, after continuous galvanostatic cycling for 1 month at high temperatures (15 days at 60 °C + 15 days at 80 °C, ∼130 cycles), these anode composites sustain a capacity at 67 mA g−1 that is still remarkable for TiO2-based anodes (155 mAh g−1 or 200 mAh cm−3, coulombic efficiency of ∼99%). On contrast, in organic carbonates the capacity decays down to 80 mAh g−1 after only 15 days at 60 °C. Our results suggest that the principles derived from porous anatase mesocrystal/ionic liquid electrolyte combinations could constitute the basis for battery applications in which safety, durability and variability in operating temperature represent the primary concerns.