7.4 Hybrid Capacitors
217
1.4 kW kg
−1 (based on the weight of Ti 2 CT x ). Additionally, there was only 4%
loss of the second discharge capacity after 100 cycles at 600 mA g
−1 with a high
Coulombic efficiency of ~99.7% after a few initial cycles (Fig. 7.12d). Dall’Agnese
et al. (2015) studied the electrochemical behavior of V 2 C MXene for the Na-ion
hybrid capacitors. The XRD characterization results showed the continuous Na
+
intercalation between the V 2 CT x layers in a wide range of potentials. Furthermore,
the Na-ion hybrid capacitor based on the V 2 CT x cathode and the hard carbon anode
exhibited a specific capacity of 50 mA h g
−1 after 100 cycles at 6 °C with a maximum
cell voltage of 3.5 V.
7.5 Conclusions
Nanostructured materials have been extensively studied as electrode materials in
supercapacitors. The nanostructure can not only provide a plentiful active surface
for energy storage but also shorten the ion diffusion pathway, thus enhancing the
performance effectively. For further improving the performance of supercapacitors,
researchers could focus on the following several aspects.
The construction of nanocomposites of pseudocapacitive materials and nanostructured carbon materials can not only effectively improve the electrical conductivity of pseudocapacitive materials but also can inherit the nanostructures of carbon
materials. The obtained nanocomposites can realize the synergistic effect of each
component, thus effectively improves the performance of supercapacitors. This
topic deserves further comprehensive study.
Abundant studies show that nanostructured materials exhibit high specific capacitance and good rate performance. However, the nanostructure usually causes the
low tap density of the electrode materials. Hence, more reasonable nanostructures
should be designed to ensure large volume energy densities of the supercapacitor
device. MXenes have become very promising electrode materials for supercapacitors owing to their unique 2D structure and highly defined geometry. However,
there are few reports about the electrochemical reaction mechanism of MXene materials. In order to further improve the performance of these materials, more research
about the electrochemical reaction mechanism will be necessary. The free-standing
flexible electrode is an important research direction in the field of supercapacitors.
When the free-standing material is utilized as the electrode, the conductive carbon
and adhesive are unnecessary, which can effectively improve the energy density of
the device. Furthermore, the free-standing electrode can improve the cyclic stability
of the device.
217
1.4 kW kg
−1 (based on the weight of Ti 2 CT x ). Additionally, there was only 4%
loss of the second discharge capacity after 100 cycles at 600 mA g
−1 with a high
Coulombic efficiency of ~99.7% after a few initial cycles (Fig. 7.12d). Dall’Agnese
et al. (2015) studied the electrochemical behavior of V 2 C MXene for the Na-ion
hybrid capacitors. The XRD characterization results showed the continuous Na
+
intercalation between the V 2 CT x layers in a wide range of potentials. Furthermore,
the Na-ion hybrid capacitor based on the V 2 CT x cathode and the hard carbon anode
exhibited a specific capacity of 50 mA h g
−1 after 100 cycles at 6 °C with a maximum
cell voltage of 3.5 V.
7.5 Conclusions
Nanostructured materials have been extensively studied as electrode materials in
supercapacitors. The nanostructure can not only provide a plentiful active surface
for energy storage but also shorten the ion diffusion pathway, thus enhancing the
performance effectively. For further improving the performance of supercapacitors,
researchers could focus on the following several aspects.
The construction of nanocomposites of pseudocapacitive materials and nanostructured carbon materials can not only effectively improve the electrical conductivity of pseudocapacitive materials but also can inherit the nanostructures of carbon
materials. The obtained nanocomposites can realize the synergistic effect of each
component, thus effectively improves the performance of supercapacitors. This
topic deserves further comprehensive study.
Abundant studies show that nanostructured materials exhibit high specific capacitance and good rate performance. However, the nanostructure usually causes the
low tap density of the electrode materials. Hence, more reasonable nanostructures
should be designed to ensure large volume energy densities of the supercapacitor
device. MXenes have become very promising electrode materials for supercapacitors owing to their unique 2D structure and highly defined geometry. However,
there are few reports about the electrochemical reaction mechanism of MXene materials. In order to further improve the performance of these materials, more research
about the electrochemical reaction mechanism will be necessary. The free-standing
flexible electrode is an important research direction in the field of supercapacitors.
When the free-standing material is utilized as the electrode, the conductive carbon
and adhesive are unnecessary, which can effectively improve the energy density of
the device. Furthermore, the free-standing electrode can improve the cyclic stability
of the device.