Coupling thin Li metal anodes with high-capacity/high-voltage cathodes such as LiNi0.8Co0.1Mn0.1O2 (NCM811) is a promising way to 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 cluster, which is critical for enabling the formation of stable interfaces 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 = 679 Wh kgcell −1/1,024 Wh Lcell −1) coupled with nonflammability.
Bibliographical noteFunding Information:
This work was supported by US Army Research Office (ARO) ( W911NF-18-1-0016 ), Basic Science Research Program ( 2017M1A2A2087810 , 2018R1A2A1A05019733 , 2018M3D1A1058624 , and 2019R1I1A1A0144168 ), Wearable Platform Materials Technology Center ( 2016R1A5A1009926 ) through a National Research Foundation of Korea (NRF) grant by the Korean Government ( MSIT ), and Corporate R&D of LG Chem. The computation modeling work at ARL was supported by a Department of Energy Program (Peter Faguy).
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