Study On The Preparation And Properties Of Integral Flexible Bacterial Cellulose Supercapacitor

The environmental pollution and energy shortage have been payed attention in recent years.Developing new,green and environmental energy and energy storage devices has also been widely researched.Comparing to lithium battery,supercapacitor as the green new device,with higher power density and cycle life is welcome.The structure of traditional supercapacitor,similar to battery,is consisted of positive electrode,negative electrode,separator and electrolyte,needs a lots of materials and has complex assembly technology.Especially,the natural polymer bacterial cellulose?BC?,due to the special three-dimensional nanofiber network,super hydrophilic absorbability and excellent mechanical properties,not only suitable for hydrogels,flexible substrates and carbon sources,but for separator.Besides,recent literatures have done a lot of study about it,which is an ideal raw material for new environmental protection supercapacitors.This topic is mainly based on the special structure of BC,prepared the conductive polymer coated BC as a nitrogen contained carbon source and carbonized it for N doped activated carbon.A flexible thin film integrated solid-state supercapacitor was prepared by assembling them in a novel way and its characterization and electrochemical performance was tested and analyzed.The article was divided into three parts:?1?In the hydrogel state,Polyaniline?PANI?was deposited in-situ on the BC surface of3D nanofiber network.Because of the influence of molecular dynamics,the aniline molecules are difficult to enter in the thicker and denser fiber membrane,which formed a special sandwich structure.By simply peeling of the film,we can obtain PANI coated BC PANI/BC on one side and uncoated pure cellulose BC fiber on the other side.The peeled PANI/BC//BC film can work as positive electrode and separator materials;same time,it can be carbonized as high specific surface area N-doped active carbon negative electrode KPBC.After added electrolyte,flexible all solid-state supercapacitor PANI/BC//KPBC was prepared and the electrochemical performance was analyzed.The solid-state capacitor shows good cyclic stability?retains 100%capacitance over 2500 cycles?and coulomb efficiency during the charge-discharge test.?2?Another conductive polymer polypyrrole?PPy?was studied and Fe Cl₃ was used as oxidant to polymerize on the surface of BC to obtain similar PPy coated PPy/BC on a side and the other side is cellulose BC.The PPy/BC as another nitrogen-containing carbon source to prepare KYBC by carbonation and alkali activation at high temperature.Finally,all-solid-state flexible supercapacitor PPy/BC//KYBC were fabricated and the performance was further studied.The solid-state capacitor also shows high working potential?up to 1.4 V?and a specific area capacitance of?195.5 mF/cm²?.?3?In order to improve the capacity of the capacitor,the Fe was doped in negative electrode material.The precursor of iron hydroxide was formed on BC by hydrothermal synthesis and then the pyrrole monomer was in-situ polymerized on the surface of film to obtain PPy/Fe₃O₄/BC.By the same way,negative carbon material Fe-N-BC was obtained by carbonation and alkali activation at high temperature.This double doped carbon material doped metal element Fe,nonmetallic element N,shows obvious pseudo-capacitance and double layer capacitance.Besides,the capacity of this new carbon is increased effectively and the working potential is low?lowest-1 V?.By matching the potential,the PPy/BC//BC is used as the positive electrode and the separator and all-solid-state flexible supercapacitor PPy/BC//Fe-N-BC was obtained.After measure,the capacitor shows a higher area capacitance?426.2 mF/cm²?and working potential?up to 1.6 V?.In this paper,the bio environment-friendly material BC was used as the substrate and all-solid-state flexible supercapacitor was successfully prepared by polymerization-peeling carbonization and filtration.This new way provides a new idea for the preparation of conventional supercapacitor and has a certain significance in the protection of the environment and energy storage.