Potassium-ion
batteries (PIBs) are attracting great interest for
large-scale energy storage owing to the abundant resources and low
redox potential of K+/K. However, the large volume changes
and slow kinetics caused by the larger ionic radius of K+ for cathode materials remain a critical challenge for PIBs. Herein,
we construct few-layered covalent organic frameworks integrated with
carboxylated carbon nanotubes (DAAQ-COF@CNT) as cathode materials
for PIBs. The synthesized DAAQ-COF@CNT features numerous active sites,
a stable conductive framework, and an appropriate surface area with
nanopores, which can render high electrical conductivity, shorten
the ion/electron diffusion distance, and accelerate K+ diffusion.
In consequence, the DAAQ-COF@CNT delivers a high reversible capacity
of 157.7 mAh g–1 at 0.1 A g–1,
an excellent rate capability of 111.2 mAh g–1 at
1 A g–1, and a long cycling stability of 77.6% capacity
retention after 500 cycles at 0.5 A g–1. The integrated
characterization of ex situ X-ray photoelectron spectroscopy, Fourier
transform infrared spectroscopy, and theoretical simulation discloses
that the storage mechanism of DAAQ-COF@CNT is based on the reversible
reaction between electroactive CO groups and K+ during two successive steps. This work provides a promising high-performance
cathode material for PIBs and encourages the development of new types
of covalent organic frameworks for PIBs.
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