2.1 Vacuum filtration
According to the reported work on cellulose paper based electrode
materials for supercapacitors, vacuum filtration is the most widely used
and relatively simple method for preparing paper based electrode
materials from cellulose [47]. The method is to filter the solvent
(mostly water) in the homogenous electrode material slurry by pressure
difference, and then form 2D cellulose paper-based electrode material
through the interaction between materials. In the vacuum filtration
process, the structural design between cellulose and active materials is
the key to determine the energy storage performance of cellulose based
paper based supercapacitors. In the work related to this preparation
process, most of the work is focused on the structural design of
cellulose and carbon materials (activated carbon, graphene, carbon
nanotubes and graphene quantum dots, etc.) [48-51], polyaniline
[52, 53], MXene [54, 55] and other electrically active
substances [56-58]. Then, the electrochemical energy storage
performance is enhanced by introducing the third component active
substance or electropolymerization.
In the application of traditional electrode materials, carbon based
electrode materials are prepared by mixing the binder and conductive
carbon black. When used as a device, the specific surface area of the
active material involved in the electrochemical reaction will be reduced
due to the adhesion of the adhesive on the surface of the active
material, which severely limits the energy storage performance of the
active material. Cellulose, as a good binder, can provide sufficient
specific capacitance and good conductivity after being compounded with
active materials. Cellulose provides excellent mechanical properties and
porous structure. This makes the cellulose paper based supercapacitor
have good mechanical and electrochemical properties.