Exceptional Li-Rich Mn-Based Cathodes Enabled by Robust Interphase and Modulated Solvation Microstructures Via Anion Synergistic Strategy

Abstract

Coupling Li-rich Mn-based oxide (LRMO) cathodes with lithium metal anodes is crucial to enabl high-energy batteries. However, capacity decline of LRMO caused generally by unexpected parasitic reactions needs to be solved. Herein, an anion synergistic strategy is developed to manipulate the solvation structure to boost the electrochemical performance of high-voltage lithium batteries. Multi-salt electrolytes containing TFSI−, DFOB−, and DFBOP− anions are formulated via facilitating a distinctive aggregate, Li+-(DFBOP−)0.10(DFOB−)0.49(TFSI−)0.51EC0.63EMC2.49DEC0.77, which can reduce the penetration of other anions into the first solvation sheath and strengthen the interaction between Li+ ions and solvent molecules simultaneously. The solvation structure is studied by molecular dynamics (MD) and its feature is found to be able to enhance the transport kinetics of Li+ effectively and favor the formation of an inorganic-rich interphase. Corrosion of the Al collector is retarded effectively by a cathode−electrolyte interphase (CEI) constructed by the decomposition of DFBOP−, thereby enhancing the cyclability. In addition, Li||LRMO cell can retain its 85% initial capacity after 650 cycles at 1 C. This study provides a guideline to formulate high-voltage electrolytes with excellent kinetics by regulating the microstructures of solvation and interphases via anion formulation engineering.