Covalent Organic Framework Fiber-Constructed Artificial Solid Electrolyte Interphase Layer: Facilitated Uniform Deposition of Li<sup>+</sup> and Encapsulated Li Dendrite
Xiaoyun Fan, Yantao Zhang, Yaying Dou, Xiaodi Li, Zhiyi Zhao, Xiangjing Zhang, Haixia Wu, Shanlin Qiao
Abstract
Due to ultrahigh theoretical capacity and ultralow redox poteneial, lithium metal is considered as a promising anode material. However, uneven lithium deposition, uncontrollable lithium dendrite formation, and fragile solid electrolyte interphase (SEI) lead to low lithium utilization, rapid capacity decay, and poor cycle performance. Herein, a robust artificial SEI film by coating the lithium surface with fibrous covalent organic framework (Fib-COF) was constructed, which effectively prevented dendrite penetration and battery short-circuits. Experimental results demonstrated that the Fib-COF-decorated batteries showcased higher Coulombic efficiency (CE), extended cycling stability, and superior electrolyte compatibility. The strong affinity of the carbonyl group in Fib-COF towards Li + contributes to facilitating the Li + uniform transfer and nucleation. In situ optical microscopy dynamically revealed the formation process of dendrite-free interphase under the function of Fib-COF layer. As a result, the modified Li anode demonstrated remarkable cycle stability for more than 650 h at 20 mA cm –2 and 5 mAh cm –2 in ether-based electrolyte and 1000 h at 0.5 mA cm –2 and 0.5 mAh cm –2 in carbonate-based electrolyte. The dendrite-free Fib-COF@Li electrodes endowed higher specific capacities of 650 mAh g –1 for Fib-COF@Li|S full cell after 250 cycles and 120 mAh g –1 for Fib-COF @Li|LiFePO 4 full cells after 300 cycles.