Three‐Dimensional Crown Ether Covalent Organic Framework as Interphase Layer toward High‐Performance Lithium Metal Batteries

Abstract

The practical application of lithium (Li) metal batteries is inhibited by accumulative Li dendrites and continuous active Li consumption during cycling, which results in a low Coulombic efficiency and short lifetime. Constructing artificial solid‐electrolyte interphase (SEI) layer in Li anode, such as two‐dimensional covalent organic frameworks (COFs), is an effective strategy to restrain the formation of Li dendrites and improve cycling performance. However, the exploration of three‐dimensional (3D) COFs as protecting layers is rarely reported, because of the preconception that the interconnect pores in 3D COFs eventually cause Li dendrites in disordered direction. We demonstrate 3D crown ether based COF with ffc topology as interphase layer, in which the crown ether units are arranged in parallel and vertical orientation along the electrode. The strong coupling effect between the crown ether and Li⁺ accelerates Li⁺ diffusion kinetics and enables homogeneous Li⁺ flux, resulting in a high Li⁺ transference number of 0.85 and smooth Li deposition in 3D direction. Li/COF‐Cu cells display a lower Li‐nucleation overpotential (17.4 mV) and high average Coulombic efficiency of ∼98.6% during 340 cycles with COF incorporation. This work gives us a new insight into designing COFs for energy storage systems.

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