Ultra-High Energy-Density/Nonflammable Lithium Metal Full Cells Based on Coordinated Carbonate Electrolytes

Abstract

Coupling thin Li metal anodes with high-capacity/high-voltage cathodes such as LiNi0.8Co0.1Mn0.1O2 (NCM811) is a promising way to significantly increase lithium battery energy density. Yet, the realization of high performance full cells remains a formidable challenge. Here, we demonstrate a new class of highly coordinated, nonflammable carbonate electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) in propylene carbonate/fluoroethylene carbonate mixtures. Utilizing an optimal salt concentration (4 M LiFSI) of the electrolyte results in a unique coordination structure of Li+-FSI−-solvent clusters, which is critical for enabling the formation of stable interphases on both the thin Li metal anode and high-voltage NCM811 cathode. Under highly demanding cell configuration and operating conditions (Li metal anode = 35 μm, areal-capacity/charge-voltage of NCM811 cathode = 4.8 mAh cm−2/4.6 V, and anode excess capacity (relative to the cathode) = 0.83), the Li metal-based full cell provides exceptional electrochemical performance (energy densities = 681 Wh kgcell−1/1026 Wh Lcell−1) coupled with nonflammability.