Ordered LiNi0.5Mn1.5O4 Cathode in Bis(fluorosulfonyl)imide-Based Ionic Liquid Electrolyte: Importance of the Cathode-Electrolyte Interphase

The high-voltage (4.7 V vs Li+/Li) spinel lithium nickel manganese oxide (LiNi0.5Mn1.5O4, LNMO) is a promising candidate for the next generation of lithium-ion batteries due to its high energy density, low cost, and low environmental impact. However, poor cycling performance at high cutoff potentials limits its commercialization. Herein, hollow-structured LNMO is synergistically paired with an ionic liquid electrolyte, 1 M lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl-N-methylpyrrolidinium bis( fluorosulfonyl)imide (Pyr(1,3)FSI), to achieve stable cycling performance and improve the rate capability. The optimized cathode-electrolyte system exhibits extended cycling performance (>85% capacity retention after 300 cycles) and high rate performance (106.2 mAh g(-1) at 5C) even at an elevated temperature of 65 degrees C. X-ray photoelectron spectroscopy and spatially resolved X-ray fluorescence analyses confirm the formation of a robust, LiF-rich cathode-electrolyte interphase. This study presents a comprehensive design strategy to improve the electrochemical performance of high-voltage cathode materials.

Automated summary

By synergistically pairing hollow-structured LNMO with an ionic liquid electrolyte, stable cycling performance and improved rate capability were achieved, allowing for high energy density and low cost. This comprehensive design strategy provides insights to enhance the electrochemical performance of high-voltage cathode materials.