Abstract
SummaryCoupling 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.
Highlights
Li metal batteries (LMBs) have garnered substantial attention as an appealing next-generation energy storage system owing to the use of Li metal anodes possessing a low redox potential (À3.04 V versus standard hydrogen electrode), high specific capacity (3,860 mAh gLiÀ1), and low density (0.534 g cmÀ3) (Albertus et al, 2017)
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+-FSIÀ-solvent cluster, which is critical for enabling the formation of stable interfaces on both the thin Li metal anode and high-voltage NCM811 full-cell (NCM811) cathode
Summary
Li metal batteries (LMBs) have garnered substantial attention as an appealing next-generation energy storage system (i.e., beyond Li-ion batteries [LIBs]) owing to the use of Li metal anodes possessing a low redox potential (À3.04 V versus standard hydrogen electrode), high specific capacity (3,860 mAh gLiÀ1), and low density (0.534 g cmÀ3) (Albertus et al, 2017). This demonstrates that electrolytes play a determinant role in both the electrochemical stability of the electrode-electrolyte interface and the safety of full cells
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