7.3 Pseudocapacitors
211
Fig. 7.8 a SEM image of the Ti 3 C 2 T x layered particle. b Rate performances in different aqueous
electrolytes. c SEM image of paper electrode. d Capacitance retention of Ti 3 C 2 T x paper in KOH
at 1 A g −1 . e Rate performance of different samples. f Capacitance retention of a 5-mm-thick
rolled electrode in 1 M H 2 SO 4 . a–d Reprinted from Ref. Lukatskaya et al. (2013), copyright 2013,
with permission from Science. e, f Reprinted from Ref. Ghidiu et al. (2014), copyright 2014, with
permission from Nature
Owing to the large surface area-to-volume ratios, two-dimensional (2D) nanomaterials have become the favorable electrode materials for SCs. However, the traditional method for the fabrication of electrodes usually results in restacking of 2D
nanomaterials, thus decreasing ion transport rate in thick films. Therefore, the thickness of the film can obviously affect the electrochemical performance of SCs. In
this regard, Gogotsi’s group (Xia et al. 2018) reported a suitable method to fabricate
MXene (Ti 3 C 2 T x ) lamellar liquid crystal (MXLLC), which can lead to an excellent electrochemical performance regardless of the thickness of 2D nanomaterials.
They prepared a vertical alignment of 2D flakes under an external mechanical shear
force. As shown in Fig. 7.9a, the vertical alignment of MXene enabled fast ion transport. Thus, excellent electrochemical performance was achieved. MXLLC (with
pseudocapacitive characteristics) got a distinct improvement of the electrochemical
performance compared to the filtered MXene paper (lost most of the pseudocapacitive characteristics of Ti 3 C 2 T x ). Meanwhile, the electrochemical performance of
MXLLC remained no significant changes when the film thickness changed from 40
to 200 μm, indicating a thickness-independent behavior (Fig. 7.9b). Additionally,
the as-prepared MXLLC electrodes were extremely stable and retained almost 100%
capacitance retention after 20,000 cycles at 20 A g
−1 (Fig. 7.9c).
211
Fig. 7.8 a SEM image of the Ti 3 C 2 T x layered particle. b Rate performances in different aqueous
electrolytes. c SEM image of paper electrode. d Capacitance retention of Ti 3 C 2 T x paper in KOH
at 1 A g −1 . e Rate performance of different samples. f Capacitance retention of a 5-mm-thick
rolled electrode in 1 M H 2 SO 4 . a–d Reprinted from Ref. Lukatskaya et al. (2013), copyright 2013,
with permission from Science. e, f Reprinted from Ref. Ghidiu et al. (2014), copyright 2014, with
permission from Nature
Owing to the large surface area-to-volume ratios, two-dimensional (2D) nanomaterials have become the favorable electrode materials for SCs. However, the traditional method for the fabrication of electrodes usually results in restacking of 2D
nanomaterials, thus decreasing ion transport rate in thick films. Therefore, the thickness of the film can obviously affect the electrochemical performance of SCs. In
this regard, Gogotsi’s group (Xia et al. 2018) reported a suitable method to fabricate
MXene (Ti 3 C 2 T x ) lamellar liquid crystal (MXLLC), which can lead to an excellent electrochemical performance regardless of the thickness of 2D nanomaterials.
They prepared a vertical alignment of 2D flakes under an external mechanical shear
force. As shown in Fig. 7.9a, the vertical alignment of MXene enabled fast ion transport. Thus, excellent electrochemical performance was achieved. MXLLC (with
pseudocapacitive characteristics) got a distinct improvement of the electrochemical
performance compared to the filtered MXene paper (lost most of the pseudocapacitive characteristics of Ti 3 C 2 T x ). Meanwhile, the electrochemical performance of
MXLLC remained no significant changes when the film thickness changed from 40
to 200 μm, indicating a thickness-independent behavior (Fig. 7.9b). Additionally,
the as-prepared MXLLC electrodes were extremely stable and retained almost 100%
capacitance retention after 20,000 cycles at 20 A g
−1 (Fig. 7.9c).