(Invited) Suitable Materials and Electrolytes for Li-Ion Battery Fast Charging Applications

Abstract

Extreme fast charging (XFC) and cost of Li-ion batteries are the major hurdle facing the wide acceptance of EVs. While thick electrodes are suited for high energy density and low cost, Li-ion mass transport limitation and concentration gradient lead to Li-ion depletion at higher C-rate, and charging the cells with reasonable energy density cannot be realized. In this work, we will examine the kind of materials and electrolytes that could be suitable for Li-Ion battery fast charging applications. On one hand, we coated LiNi0.5Mn1.5O4 with zirconia (ZrO2) nanosize particles. Unlike most coating processes, the method involved the use of a soft and scalable ball milling technique in which increasing amounts of ZrO2 (0.5-2 wt.%) were introduced to LiNi0.5Mn1.5O4 just before the final calcination. The obtained materials have been characterized by x-ray diffraction, scanning and transmission electron microscopies (SEM and TEM), and electrochemical charge and discharge. We also used the electrochemical impedance spectroscopy (EIS) to characterize the electrode/electrolyte interfaces before and after coatings. This process has resulted in significantly improving the life of LiNi0.5Mn1.5O4 under high-temperature (55oC) and rate performance (10-min charge) conditions. On the other hand, we improved Li-ion transference number and ionic conductivity in nonaqueous electrolyte system which will have significant impact on: (1) increasing accessible charge capacity (with thick electrodes) from 50% (industrial baseline electrolyte) to ≥80% and (2) reducing lithium metal plating to improve cell safety and cycle life.