Hierarchical-structured
electrodes having merits of superior
cycling stability and high rate performance are highly desired for
next-generation energy storage. For the first time, we reported
a compressible and hierarchical porous carbon nanofiber foam (CNFF)
derived from a sustainable and abundant biomaterial resource, bacterial
cellulose, for boosting the electrochemical performance of potassium-ion
batteries. The CNFF free-standing electrode with a hierarchical porous
three-dimensional structure demonstrated excellent
rate performance and outstanding
cyclic stability in the extended cycling test. Specifically, in the
long-term cycling-stability test, the CNFF electrode maintained a
stable capacity of 158 mA h g–1 after 2000 cycles
at a high current density of 1000 mA g–1, which
has an average capacity decay of 0.006% per cycle. After that, the
CNFF electrode maintained a capacity of 141 mA h g–1 at a current density of 2000 mA g–1 for another
1500 cycles, and a capacity of 122 mA h g–1 at a
current density of 5000 mA g–1 for an additional
1000 cycles. The mechanism for the outstanding performance is that
the hierarchical porous and stable CNFF with high surface area and
high electronic conductivity provides sufficient sites for potassium-ion
storage. Furthermore, quantitative kinetics analysis has validated
the capacitive- and diffusion-controlled charge-storage contributions
in the carbon-foam electrode. This work will inspire the search for
cost-effective and sustainable materials for potassium electrochemical
energy storage.