A Protective Layer for Lithium Metal Anode: Why and How

Abstract

Lithium metal is the most promising candidate anode material for high energy density batteries, but its high activity and severe dendrite growth lead to safety concerns and limit its practical use. Constructing a protective layer (PL) on the lithium surface to avoid the side reactions and stabilize the electrode‐electrolyte interface is an effective approach to solve these problems. In this review, the recent progress on PLs is summarized, and their desired properties and design principles are discussed from the aspects of materials selection and the corresponding fabrication methods. Advanced PLs with different properties are then highlighted, including a self‐adjusting feature to increase structural integrity, the synergistic effect of organic and inorganic hybrids to improve mechanical properties and ionic conductivity, the use of embedded groups and ion diffusion channels to regulate ion distribution and flux, and a protective barrier to suppress corrosion from humid air or water. Finally, the remaining challenges and the possible solutions for PL design in future studies are proposed.

A scalable, ecofriendly, and cost-effective lithium metal protection layer from a Post-it note

“…The use of a protection layer on Li metal could be the simplest and most effective approach to suppress dendrite growth and avoid side reactions. 26 Electrochemically active carbon is a good candidate material for the protection layer because of its mechanical robustness and underlying controlled Li deposition 27 Paper, made of natural bers that contain cellulose and lignin, 28 is a low-cost and ecofriendly two-dimensional material with uniform thickness. Like other plant-derived materials, such as coffee husks and sawdust, paper can be transformed into an energy storage material via thermal treatment because the cellulose and lignin can be carbonized.…”

“…The use of a protection layer on Li metal could be the simplest and most effective approach to suppress dendrite growth and avoid side reactions. 26 Electrochemically active carbon is a good candidate material for the protection layer because of its mechanical robustness and underlying controlled Li deposition 27 …”

A Li–In alloy anode and Nb2CTXartificial solid-electrolyte interphase for practical Li metal batteries

“…20,25 In addition to the Li alloying strategy, the introduction of an articial SEI (ASEI) layer has been considered as another promising approach to suppress dendrite formation and mitigate parasitic reactions. 5,13,26 A variety of ASEI materials have been reported to date, including those based on carbon, 27,28 polymers, 29,30 and transition metal. 25,31 For example, MXenes, a class of two-dimensional inorganic compounds, have attracted considerable attention as promising ASEIs owing to their high conductivity and layered structure and the high Li affinity of their surface functional groups, such as O and F atoms.…”

Regulating Li‐ion Flux through a Dense yet Highly Ionic Conductive Interlayer for Stable Li Deposition

“…[6][7][8][9][10][11][12][13][14][15][16] However, these 3D hosts usually lower the volumetric and gravimetric energy density due to their large volume and weight and increase the risk of side reactions. Another strategy is to construct a stable artificial solid electrolyte interphase by ex situ or in situ methods to ensure the uniform Li plating/stripping, [17][18][19][20][21][22][23][24][25] but the interfacial layer structure control is complicated to ensure the integrity in long cycling.The Li dendrite growth is mainly due to the uneven distribution of Li + ions on the electrode surface because of the uncontrollable ion diffusion driven by the electric field, which then induces non-uniform Li deposition. [26][27][28][29][30][31][32][33][34] Thus, regulating the Li + ion diffusion in a controlled direction should be a promising way for the uniform Li + ion distribution and then suppress the dendrite Li deposition.…”

“…[6][7][8][9][10][11][12][13][14][15][16] However, these 3D hosts usually lower the volumetric and gravimetric energy density due to their large volume and weight and increase the risk of side reactions. Another strategy is to construct a stable artificial solid electrolyte interphase by ex situ or in situ methods to ensure the uniform Li plating/stripping, [17][18][19][20][21][22][23][24][25] but the interfacial layer structure control is complicated to ensure the integrity in long cycling.…”