The schematic representation shown in Scheme. 1 illustrates the process
of sandwich-like MXene/AAC composite. First, a thin layer of MXene, as a
flexible and conductive binder, is formed using vacuum-assisted
filtration of a colloidal solution containing delaminated suspended
Ti3C2T3 flakes. Then, a
layer of AAC is deposited on the top of
Ti3C2T3 layer. Finally,
the sandwich-like MXene/AAC composite is produced by repeating the
process. The procedure is much simpler than the conventional paste
electrode fabrication means by mixing the Polytetrafluoroethylene (PTFE)
as the binder, Acetylene black as the conductive binder and the active
materials in aqueous solution, then coating the slurry onto nickel foam
current collectors5,
11.
Fig.1. FESEM and TEM images of
MXene/AAC: (a-i): FESEM images of MXene/AAC 2:1 (j-l): TEM images of
MXene/AAC 2:1.
The morphology and microstructure of synthetic MXene/AAC 2:1 are
observed by Field emission
electron microscope (FESEM)(Fig.1.a-i) at different magnifications and
the corresponding energy-dispersive spectrometry (EDS) mapping (Fig S1
(c)). As shown in Fig.1. (a-c), the MXene/AAC hybrids have a
sandwich-like structure, where the AAC powers are evenly encapsulated in
the MXene flakes, which could effectively avoid MXene flakes stacking
and could improve the electrochemical property. The MXene exhibits a
separately lamellar and accordion-like structure with lateral size of
0.5-2 µm and the AAC particles are relatively rigid and irregular with
the size of 10 nm-1µm shown in Fig.1. (d-i), demonstrating that LiF and
HCl treatment effectively removed Al ion from the lattices. The EDS
mapping of C, Ti, O and N exhibited in Fig. S1(c). It is obviously
observed that C and Ti are uniformly distributed as a whole, without
visible boundaries. The sandwich-like structure with the encapsulation
of the AAC particles and MXene flakes in the MXene/AAC hybrids is
further confirm by TEM shown in Fig.1. (j-l) and Fig. S1(a-b),
respectively. The Fig.S2 shows that the MXene/AAC film are flexible,
freestanding and could be directly employed as electrodes for
supercapacitors without the any metal current collector.