2.2.2.2 Cellulose/conductive polymer paper-based composite
electrode
In view of the excellent flexibility and modifiable properties of 2D
cellulose paper, two conductive polymers, PEDOT and PPy, have been
widely used in 2D cellulose paper by in-situ polymerization.Li et al.
[99] constructed a PEDOT/CP paper-based composite electrode by
successfully loading PEDOT in cellulose paper (CP) by gas phase
polymerization. Figure 9A shows a schematic diagram of the preparation
of a paper-based electrode. The Fe3+ oxidant is first
added dropwise to the CP, and then the CP adsorbed
Fe3+ is placed in a vapor phase polymerization vessel.
Finally, PEDOT/CP paper-based electrode was obtained by washing and
drying. The authors prepared paper-based electrodes with different PEDOT
loading amounts by controlling the number of gas-phase polymerization.
The results show that the electrode (PEDOT/CP-10) after 10
polymerization shows excellent conductivity (14 Ω/square) and a volume
ratio capacitance of 13.7F cm-3. Similarly, Heo et al.
[100] obtained conductive KHO (C-KHP) by loading Korean conventional
paper (KHP) with a loaded conductive ink. Then the PEODT is loaded on
C-KHP by gas phase polymerization to obtain PC-KHP paper-based composite
electrode material. Finally,1D paper-based yarn electrode was prepared
by mechanical winding of PC-KHP (Figure 9B). A power supply unit formed
by connecting six independent devices in series successfully charges a
smart device operating at 3.6V (Figure 9C). This work provides a
conceptual reference for the practical application and large-scale
production of 2D paper-based electrodes, and promotes the development of
a new generation of flexible paper-based electronic devices.
In recent years, simple paper-based flexible energy storage devices have
been difficult to meet people’s living needs. As a device for collecting
tiny energy, nanogenerators have received widespread attention. Shi et
al. [101] prepared PPy/Cellulose Paper (PCC) by in-situ
polymerization as the main component units of flexible supercapacitors
and friction nanogenerators, respectively. As shown in Figure 9D, the
TENG consists of a Cellulose Paper substrate, a negative triboelectric
layer Nitrocellulose Membrane, and a PCC that acts as both a positive
triboelectric layer and an electrode. Supercapacitors consist of two
symmetrical PCCs, PVA/H2SO4 electrolytes, and a Cellulose Paper
substrate. The TENG exhibits an output voltage of up to 60V and a power
density of 0.83W m-2. SC exhibits a specific
capacitance of 90.1mF cm-2. The two devices were
successfully assembled into a miniaturized electronic energy storage
device (Figure 9E). To obtain paper-based high-performance electrodes
under high-quality loads. After the traditional in-situ polymerization
process, the addition of electric double-layer graphene can improve
energy storage performance (Figure 9F) [102]. The paper-based
electrode exhibits a specific capacitance of 1685mF
cm-2 and a cycle stability of 92.8% (5000 cycles). In
addition, the assembled solid-state paper-based device exhibits an area
capacitance of 1408mF cm-2 and a high area energy
density of 147μWh cm-2.
Aramid fiber has attracted the attention of researchers due to its
excellent mechanical properties and chemical stability. In recent years,
multifunctional paper-based materials prepared from aramid fibers have
been widely used in various fields of social life. Yu et al. [103]
formed ACF/PPS/MWCNT composites by papermaking processes with adhesive
polyphenylene sulfide (PPS), MWCNTs and aramid chopped fibers. The PPS
is then used as a binder for ACF and MWCNT after heating. Finally, the
ACF/PPS/MWCNT-PPy paper-based electrode was obtained by in situ
polymerization of PPy (Figure 9G). The synergies between PPy thanks to
flexible ACF fibers, highly conductive MWCNTs and excellent
pseudocapacitance properties. The paper-based electrode exhibits high
specific capacitance (3205mF cm-2 current density at
5mA cm-2) and excellent cycle stability (93%
capacitance retention after 5000 cycles). In addition, ACF/PPS/MWCNT-PPy
also exhibits excellent flame retardant properties (Figure 9H). In
conclusion, bifunctional paper-based materials with excellent energy
storage performance and good flame retardant performance were prepared.