Stable Li-Metal Batteries Enabled by in Situ Gelation of an Electrolyte and In-Built Fluorinated Solid Electrolyte Interface.

Lithium-metal batteries (LMBs) are the focus of upcoming energy storage systems with extremely high-energy density. However, the leakage of liquid electrolyte and the uncontrollable dendritic Li growth on the surface of the Li anode lead to their low reversibility and safety risks. Herein, we propose a stable quasi-solid LMB with in situ gelation of liquid electrolyte and an in-built fluorinated solid electrolyte interface (SEI) on the Li anode. The gel polymer electrolyte (GPE) is readily constructed via cationic polymerization between lithium hexafluorophosphate and ether electrolyte. The fluorine-containing additive, fluoroethylene carbonate (FEC), plays a crucial role in the building of a dense SEI with fast interfacial charge transport. The ex situ spectroscopic characterizations suggest that the enhanced LiF species in the SEI with the addition of FEC and the in situ optical microscopy reveal the inhibited dendritic Li growth. Moreover, GPE@FEC exhibits a high oxidative stability beyond 5.0 V (vs Li/Li+). The significantly improved Li plating/stripping efficiency (400 cycles, 98.7%) is presented for the Li∥Cu cells equipped with GPE@FEC. Decent cycling stability is also available for the cells with the LiFePO4 cathode, reflecting the feasibility of GPE@FEC for practical LMBs with enhanced stability and safety.

Self-assembly of MoO3-decorated carbon nanofiber interlayers for high-performance lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are attractive for next-generation energy storage systems due to their high theoretical capacity and energy density. However, the undesired shuttling of soluble lithium polysulfides (Li2Sn, 2 < n≤ 8) and the uncontrolled growth of lithium dendrites have hindered their practical applications. Herein, a self-assembled freestanding MoO3/carbon nanofiber (MoO3/CNF) composite membrane is effectively integrated into Li-S batteries as a functional interlayer. Improved cell performance is achieved due to the strong interfacial chemical and physical interactions between the interlayers with Li2Sn. The Li-S batteries exhibit a decent cyclic stability with a fading rate of 0.12% per cycle for 500 cycles at 1675 mA g-1, a high rate performance and a low self-discharge rate. In this rational design, the CNF network provides abundant electron pathways and physically prevents polysulfide diffusion. The polar MoO3 nanorods act as effective anchoring sites by the chemical interactions with Li2Sn. Meanwhile, the suppressed Li-dendrite growth on the Li-anode surface results in a stable Li stripping/plating.