Highly stable lithium metal anodes enabled by bimetallic metal-organic frameworks derivatives-modified carbon cloth.

Lithium (Li) metal anodes hold great promise for next-generation secondary batteries with high energy density. Unfortunately, several problems such as Li dendrite growth, low Coulombic efficiency and poor cycle life hinder the commercialization of Li metal anodes. Herein, we design a highly lithiophilic carbon cloth host modified with Sn-doped zinc oxide (ZnO) (ZnSn-CC) directly derived from a bimetallic ZnSn metal-organic framework (ZnSn-MOF), which boosts uniform Li plating/stripping during charge-discharge and effectively protects the Li metal anode. Due to the lithiophilic modification, the cycling reversibility of the host material is increased and the growth of Li dendrites and the generation of "dead Li" are inhibited. As a result, the resultant composite Li metal anode (ZnSn-CC@Li) manages to retain cycling stability for over 1000 h at a current density of 1 mA cm and a specific capacity of 1 mAh cm in a symmetric cell. When paired with the LiFePO (LFP) and LiNiCoMnO (NCM) cathodes, both the assembled ZnSn-CC@Li||LFP and ZnSn-CC@Li||NCM full cell achieve good rate capability and improved cycle life. Density functional theory calculations, in combination with in-situ X-ray diffraction (XRD), in-situ time-lapse optical testing, ex-situ extended X-ray fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis, reveal the origin of the synergetic interaction between Tin (Sn) and Zinc (Zn) atoms upon Sn-doping in ZnO. The improved lithiophilicity can be attributed to the incorporation of Sn atoms, which have a higher coordination number than Zn atoms, into the ZnO lattice, forming joint adsorption sites of multiple oxygen atoms toward Li atoms. The Li nucleation barrier is thereby reduced and the smooth Li deposition is facilitated. The findings provide a new strategy for the rational design of functional host materials based on bimetallic MOFs derivatives toward high-performance and safe Li metal batteries.