posted on 2020-03-13, 14:12authored byJae Min Park, Milan Jana, Puritut Nakhanivej, Bo-Kyong Kim, Ho Seok Park
High-capacity electrode
materials have been investigated to overcome
the low energy density of electrochemical capacitors, but there are
still issues arising from the trade-off between charge storage capacity
and kinetics, efficiency, and stability. Herein, we describe multivalent
sulfur redox chemistry for the high power and energy efficiency of
hybrid energy storage full cells, where nitrogen-incorporated nanoporous
carbon/nanosulfur (N-NC/nS) and lithium manganese oxide are configured
into negative and positive electrodes, respectively, using water-in-bisalt
(WIBS)-soaked poly(acrylic acid) hydrogel electrolyte. As confirmed
by the major contribution of surface redox capacity to the total capacity,
low activation energy, high exchange current density, and fast charge
transfer, the N-NC/nS achieves facile surface redox kinetics arising
from the hierarchical porosity, nanoscale confinement of nS, and high
ionic conductivity of WIBS hydrogels. The resulting full cells deliver
capacitor-like high power density of 15.7 kW kg–1, along with an energy density of 30.1 Wh kg–1,
78.7% retention over 2000 cycles, and an energy efficiency of 98%.