Ionomer-Liquid Electrolyte Hybrid Ionic Conductor for High Cycling Stability of Lithium Metal Electrodes

Abstract

The inhomogeneous Li electrodeposition of lithium metal electrode has been a major impediment to the realization of rechargeable lithium metal batteries. Although single ion conducting ionomers can induce more homogeneous Li electrodeposition by preventing Li+ depletion at Li surface, currently available materials do not allow room-temperature operation due to their low room temperature conductivities. In the paper, we report that a highly conductive ionomer/liquid electrolyte hybrid layer tightly laminated on Li metal electrode can realize stable Li electrodeposition at high current densities up to 10 mA cm−2 and permit room-temperature operation of corresponding Li metal batteries with low polarizations. The hybrid layer is fabricated by laminating few micron-thick Nafion layer on Li metal electrode followed by soaking 1 M LiPF6 EC/DEC (1/1) electrolyte. The Li/Li symmetric cell with the hybrid layer stably operates at a high current density of 10 mA cm−2 for more than 2000 h, which corresponds to more than five-fold enhancement compared with bare Li metal electrode. Also, the prototype Li/LiCoO2 battery with the hybrid layer offers cycling stability more than 350 cycles. These results demonstrate that the hybrid strategy successfully combines the advantages of bi-ionic liquid electrolyte (fast Li+ transport) and single ionic ionomer (prevention of Li+ depletion).

Stabilizing electrodeposition in elastic solid electrolytes containing immobilized anions

“…The effectiveness of the anion tethering (fig. S1A), which was demonstrated in recent studies ( 34 – 36 ), and the suppression effect of higher separator moduli (fig. S1B) noted by Stone et al .…”

An ultrathin ionomer interphase for high efficiency lithium anode in carbonate based electrolyte

“…The formation of an artificial SEI (ASEI) through a surface coating of polymer, such as poly(vinylidene difluoride) 39 , silly putty 40 , poly((N-2,2-dimethyl-1,3-dioxolane-4-methyl)-5-norbornene-exo-2,3-dicarboximide) 41 , poly(dimethylsiloxane) 42 , and styrene butadiene rubber 43 , on the Cu foil surface has been suggested for suppressing Li dendrite formation. Particularly, cation-selective ionomer membranes, which contain negatively charged groups, such as –SO 3 − , –COO − , and –PO 3 2− , that are fixed to the polymer backbone, are promising ASEI candidates because they have the potential of simultaneously facilitating the passage of Li ions 44,45 and enabling the high CEs by reducing direct contact between a solvent and the anionic ions of a salt with Li metal anode, thereby reducing solvent or anion decomposition. Li dendrite suppressing enabled by cation ionomer membranes in the literature has so far been attributed mainly to the high transference number, t + , of the ionomer, which prolonged the so-called Sandy’s time for the occurrence of dendritic plating 45,46 .…”

A reversible dendrite-free high-areal-capacity lithium metal electrode

“…The persistent thrust to solve this issue has always been driven by the unprecedented characteristics of lithium electrode, that is, its high theoretical specific capacity of 3,861 mAh g −1 and low electrochemical potential (−3.04 V versus standard hydrogen electrode), for the implementation of high specific energy Li-metal-based batteries. To circumvent the propagation of lithium dendrites, intense studies of metallic lithium electrodes (MLEs) have used strategies for conducting stable lithium electrodeposition such as maintaining a sustained supply of Li + in the vicinity of MLE surface 4 5 6 7 8 9 , the spatial redistribution of Li + surge along tailored 10 11 12 13 14 or artificial solid-electrolyte interphase (SEI) films 15 16 17 18 , enhanced Li + surface diffusivity 19 20 and the fabrication of Li metal with high surface energy 18 21 22 . As a result of these strategies, reversible dendrite-free low-areal-capacity MLEs (0.5–3.0 mAh cm −2 ) have been developed.…”