COF-42:一种理想的锂硫电池锚定材料

COF-42:an ideal anchoring material for lithium-sulfur batteries

寻找理想的锚定材料抑制穿梭效应是锂硫电池面临的重要问题之一.本文采用密度泛函方法,研究了四种共价有机框架COFs材料(COF-1,CTF-1,COF-LZU1和COF-42)和硫锂化合物(Li_(2)S_(n))的作用机理.通过分析吸附构型、吸附能、电子密度差分以及态密度等性质,发现COFs材料与硫锂化合物的化学吸附作用主要源于COFs表面极性N和O原子与Li之间的静电作用力.在COF-42/Li_(2)S_(n)吸附构型中,N和O原子与Li之间形成双重类离子键;电子密度差分和Bader电荷差分表明,与其他COFs材料相比,Li_(2)S_(n)和COF-42之间电荷转量最多,因此,COF-42具有最强的锚定作用.比较Li_(2)S_(n)和COF-42以及常用电解质分子1,3-二氧戊环(DOL)和二甲氧基乙烷(DME)的吸附能,证明COF-42可以抑制电解质分子的溶剂化作用;COF-42与COF-1,CTF-1和COF-LZU1相比较,具有良好导电性.因此,COF-42可能是一种理想的锂硫电池锚定材料.

Interaction mechanism between four kinds COFs materials and Li_(2)S_(n) was studied by DFT. The chemical adsorption interaction between COFs and Li_(2)S_(n) was studied by analyzing the adsorption structures,binding energies,charge density difference and density of states. The anchoring strength was determined by the electrostatic interaction. For COF-42/Li_(2)S_(n) complex,two Li atoms tend to directly bind to multiple N and O atoms and afford strong Li-N/O ionic bond interaction. Charge density difference and Bader charge difference indicate that the amount of charge transfer between Li2 S and COF-42 is significantly greater than those of COF-1,CTF-1 and COF-LZU1. The binding energies of Li_(2)S_(n) adsorbed on COF-42 exceed that of DOL or DME electrolyte,indicating that COF-42 can resist the solvation effect and alleviate the shuttle of Li_(2)S_(n) . Therefore,COF-42 possibly is an ideal anchoring materials for Li_(2)S_(n) .