In Situ Preparation of Thin and Rigid COF Film on Li Anode as Artificial Solid Electrolyte Interphase Layer Resisting Li Dendrite Puncture

Abstract

Metallic Li is considered the most promising anode material for high‐energy density batteries due to its high theoretical capacity and low electrochemical potential. However, commercialization of the Li anode has been hampered by the safety issue associated with Li‐dendrite growth resulting from uneven Li‐ion deposition and an unstable solid electrolyte interphase (SEI). Herein, an in situ prepared 10 nm thin film of covalent organic framework (COF) uniformly covered on the Li anode (COF‐Li) is used as an artificial SEI layer for Li plating/striping stabilization and Li dendrite inhibition. Abundant microcellular structures in the COF can redistribute the Li‐ion flux and lead to the homogeneous plating/stripping process. Meanwhile, the superhard mechanical properties and mechanical behavior during needling of the ultrathin COF film is studied via the digital pulsed force mode equipped in atomic force microscopy, illustrating a high Young's modulus of 6.8 GPa that is strong enough to resist dendrite growth. As a result, stable cycling for 400 h is achieved in the COF‐Li symmetrical cell at a current density of 1 mA cm−2, and the internal short circuit is effectively blocked by COF‐Li in Li–S batteries.

Hybrid Artificial Solid Electrolyte Interphase with Dendrite-Free Lithium Deposition and High Ion Transport Kinetics

“…At the current density of 2 mA cm –2 and areal capacity of 2 mA h cm –2 , both PVA@Li and PVA-BNOH@Li symmetric cells exhibited higher overpotential than the bare Li symmetric cell in the initial stage of cycling (Figure a). The slightly higher overpotential observed from the SEI-protected cells is due to the activation related to the wetting of artificial SEI, similar to other reported works. − After 75 cycles, the voltage profiles had stabilized and stable Li plating–stripping was obtained. When the cycling time was increased, however, the Li symmetric cell without any protection exhibited a notable increment of overpotential along with prolonged cycling.…”

Fabrication of Scalable Covalent Organic Framework Membrane‐based Electrolytes for Solid‐State Lithium Metal Batteries

“…It is speculated that the lithiophilic ether chains on the skeleton enrich the chemical environment around Li + , and the uniformly dispersed lithiophilic sites facilitate homogeneous lithium nucleation. This result is consistent with the dendrite suppression ability exhibited by COF‐based electrolytes prepared using a pressing strategy previously [45–47] . Moreover, the COF skeleton with a porous topology provides specific pathways for the directional transport of Li + by introducing lithiophilic PEG chains, thereby regulating uniform Li + deposition.…”

A Dual‐Protective MXene/COF Artificial Interface for Dendrite‐Free and Stable Lithium Metal Anodes

“…Notably, the synthesized MXene/COF exhibited high hardness and ceramic characteristics, as evidenced by the difficulty of grinding. However, this is different from the previously reported COF behavior in the 1,3-dioxolane/1,2dimethoxyethane (DOL/DME) system [26] and is thought to be due to the unique micro ceramic structure of MXene. [27] The structure and crystallization of COFs are shown in Figures S6-S9 (Supporting Information).…”