In Situ High-Level Nitrogen Doping into Carbon Nanospheres
and Boosting of Capacitive Charge Storage in Both Anode and Cathode
for a High-Energy 4.5 V Full-Carbon Lithium-Ion Capacitor
To
circumvent the imbalances of electrochemical kinetics and capacity
between Li<sup>+</sup> storage anodes and capacitive cathodes for
lithium-ion capacitors (LICs), we herein demonstrate an efficient
solution by boosting the capacitive charge-storage contributions of
carbon electrodes to construct a high-performance LIC. Such a strategy
is achieved by the in situ and high-level doping of nitrogen atoms
into carbon nanospheres (ANCS), which increases the carbon defects
and active sites, inducing more rapidly capacitive charge-storage
contributions for both Li<sup>+</sup> storage anodes and PF<sub>6</sub><sup>–</sup> storage cathodes. High-level nitrogen-doping-induced
capacitive enhancement is successfully evidenced by the construction
of a symmetric supercapacitor using commercial organic electrolytes.
Coupling a pre-lithiated ANCS anode with a fresh ANCS cathode enables
a full-carbon LIC with a high operating voltage of 4.5 V and high
energy and power densities thereof. The assembled LIC device delivers
high energy densities of 206.7 and 115.4 Wh kg<sup>–1</sup> at power densities of 0.225 and 22.5 kW kg<sup>–1</sup>,
respectively, as well as an unprecedented high-power cycling stability
with only 0.0013% capacitance decay per cycle within 10 000
cycles at a high power output of 9 kW kg<sup>–1</sup>