Distributed Li‐Ion Flux Enabled by Sulfonated Covalent Organic Frameworks for High‐Performance Lithium Metal Anodes

Abstract

Metallic Li is considered the most promising anode material for high‐energy‐density batteries owing to its high theoretical capacity and low electrochemical potential. However, inhomogeneous lithium deposition and uncontrollable growth of lithium dendrites result in low lithium utilization, rapid capacity fading, and poor cycling performance. Herein, two sulfonated covalent organic frameworks (COFs) with different sulfonated group contents are synthesized as the multifunctional interlayers in lithium metal batteries. The sulfonic acid groups in the pore channels can serve as Li‐anchoring sites that effectively coordinate Li ions. These periodically arranged subunits significantly guide uniform Li‐ion flux distribution, guarantee smooth Li deposition, and reduce lithium dendrite formation. Consequently, these characteristics afford an excellent quasi‐solid‐state electrolyte with a high ionic conductivity of 1.9 × 10−3 S cm−1 at room temperature and a superior Li++ transference number of 0.91. A Li/LiFePO4 battery with the COF‐based electrolyte exhibited dendrite‐free Li deposition during the charge process, accompanied by no capacity decay after 100 cycles at 0.1 C.

Design of High-Performance Formyl-Functionalized COF Aerogels as Quasi-Solid Lithium Battery Electrolyte by a Solvent Substitution Strategy

“…The enhanced long-term cycling stability is attributed to the following reasons: (1) Agel-COF­[4 + 3]-CHO has a higher electrolyte retention capacity thanks to the hierarchical porous structures enabling polar groups to be easily acquired; (2) the polar groups accelerate Li + delivery while regularized pores effectively inhibit lithium dendrite generation; and (3) the higher Young’s modulus (more than twice that of PP in Figure S25) well resists lithium dendrite puncture. Besides, as shown in Figure d, compared with other COF-modified LMBs, the Agel-COF­[4 + 3] 2 -CHO battery is in the leading position in terms of loading (11.5 mg cm –2 ) and cycling rate (1C), − which demonstrates its strong potential for electrochemical applications.…”

Lithiated Phosphoryl Cellulose Nanocrystals Enhance Cycling Stability and Safety of Quasi-Solid-State Lithium Metal Batteries

“…Lithiated sulfonates are supposed to be effective in increasing the ionic conductive of gel polymer electrolytes. − Phosphate are used as well to improve the electrochemical properties of GPEs, − but no significant advantage has been found. Both groups can increase the Li + transference number to a similar extent.…”