Few-Layered\nBoronic Ester Based Covalent Organic Frameworks/Carbon\nNanotube Composites for High-Performance K‑Organic Batteries

Abstract

Organic electrodes for low-cost potassium\nion batteries (PIBs)\nare attracting more interest by virtue of their molecular diversity,\nenvironmental friendliness, and operation safety. But the sluggish\npotassium diffusion kinetics, dissolution in organic electrolyte,\npoor electronic conductivity, and low reversible capacities are several\ndrawbacks compared with inorganic counterparts. Herein, the boronic\nester based covalent organic framework (COF) material is successfully\nprepared on the exterior surface of carbon nanotubes (CNTs) <i>via</i> rational design of the organic condensation reaction\nand used as an anode material for PIBs. The few-layered structure\nof COF-10@CNT can provide more exposed active sites and fast K⁺ kinetics. It exhibits ultrahigh potassium storage performances\n(large reversible capacities of 288 mAh g^–1 after\n500 cycles at 0.1 A g^–1 and 161 mAh g^–1 after 4000 cycles at 1 A g^–1), which is superior\nto previous organic electrodes and most inorganic electrodes. Moreover,\nthe K-storage mechanism is proposed to be π-cation interaction\nbetween K⁺ and conjugated π-electrons of benzene\nrings.