Researchers from France and The Netherlands have shown that both graphyne and graphdiyne surfaces in a solid-state Li-metal battery effectively permit Li intercalation while preventing other electrolyte molecules from reaching the electrodes. A paper on their work is published in Journal of Power Sources.

All-solid electrolytes could lead to a technological breakthrough in the performance of all-solid-state batteries when combined with a lithium-metal anode. However, the use of a lithium-metal anode presents several challenges, such as dendrite growth, interface electrochemical stability, formation and propagation of cracks, and delamination of the electrode/electrolyte interfaces.

This work aims to explore the effectiveness of using newly synthesized 2D graphyne-based membranes (namely graphyne, graphdiyne, and graphtriyne) for electrode protection in a solid polymer electrolyte battery through first-principle calculations, nudged elastic band method, and classical molecular dynamics simulation.

Specifically, we aim to investigate the effectiveness of these membranes in mitigating the aforementioned challenges.

— Lemaalem

The researchers proposed an alternative solution that prevents direct contact between electrolytes and electrodes by coating the electrodes with graphyne-n (n = 1, 2, 3) layers that are permeable to small cations, such as Li+ and Na+.

Graphyne (n=1), graphdiyne (n=2), and graphtriyne (n=3) are 2D carbon allotropes composed of acetylenic linkages (sp-) and benzene (aromatic rings) (sp-hybridized carbon atoms). Graphyne is a one-atom-thick planar sheet. Graphdiyne, synthesized since 2010, is the most stable non-natural carbon allotrope containing diacetylene bonds. Because of a porous structure containing triangular pores of sizes 3.94 ?, 5.42 ?, and 6.69 ? for graphyne, graphdiyne, and graphtriyne, respectively, and conjugated carbons, graphyne-n provides storage sites and diffusion pathways for small ions such as Li+.

The Li+ can thus diffuse in parallel and perpendicular directions to the graphyne-n layers, making graphyne-n a promising 2D material in energy-storage batteries.

The studied battery model consisted of solid polymer electrolytes (SPEs) delimited by two graphyne-n surfaces, where each surface is composed of four layers of a graphyne-n sheet, with n=1, 2, or 3.

The researchers applied a high external electric field of up to 0.5 V/?, 0.75 V/?, and 1 V/? to accelerate the ion diffusion process. The adsorption energies, charge transfer, and in-plane/out-plane diffusion of single lithium on graphyne-based surfaces were investigated. Afterward, they calculated and compared the Li permeability, the electrolyte molecules’ rejection efficiency, and the intrinsic properties of graphyne-based nanoporous membranes.

Resources

Mohammed Lemaalem, Nabil Khossossi, Gaelle Bouder, Poulumi Dey, Philippe Carbonnière (2023) “Graphyne-based membrane as a promising candidate for Li-Battery electrodes protection: Insight from atomistic simulations,” Journal of Power Sources, Volume 581 doi: 10.1016/j.jpowsour.2023.233482

by greencarcongress