Preparation And Research Of Supercapacitors Based On Natural Polymer Hydrogels

Energy storage field have advanced considerably in the last two decades as a result of the advancement of contemporary technology and the growing need for energy.Currently,common energy storage devices include batteries,supercapacitors,etc.Supercapacitors stand out from the crowd as the ideal renewable energy storage devices because of its fast charging and discharging capability,high power density,durability,environmental friendliness,and stability.However,the main disadvantages of typical petroleum-based polymer materials are their high cost and environmental impact,as well as the toxicity risks related with ionic gels.As a result,the usage of biodegradable natural polymers rather than non-biodegradable synthetic polymers is on the horizon.The renewability,biodegradability,and biocompatibility make natural polymers perfect substitutes for non-degradable polymers.The preparation of supercapacitors using natural polymer hydrogels is one of the ways to compound green materials and green energy concepts.By preparing polymer hydrogel based supercapacitors with frost resistance,flexibility,and high electric capacity,this thesis aims to prepare supercapacitors using natural polymer hydrogels and can provide new ideas in the field of green chemistry and sustainable development.The main innovations of this paper include:(1)The hydrogel is created using pristine cellulose rather than combining petroleum-based polymers,demonstrating the immense potential of cellulose in the field of flexible device.(2)The anti-freezing performance of the cellulose hydrogels in harsh environment is improved,leadint to anti-freezing supercapacitor.(3)Using supercapacitors in conjunction with triboelectric nanogenerator to create cellulose based self-powered systems.(4)By preparing an integrated supercapacitor,the interface resistance is greatly reduced and the electrochemical performance of the supercapacitor is improved.(5)The advanced treatment and exploitation of waste animal teeth has paved the path for a more comprehensive use of animal-derived waste in the energy storage industry.The main research and findings of this thesis are summarized as follows:A self-charging power system composed of cellulose organohydrogel based supercapacitor and triboelectric nanogenerator is constructed in the present work.Cellulose organohydrogels with flexibility,optical transparency,conductivity and excellent low temperature tolerance are fabricated via a dissolution and regeneration process.The optical transmittance,elongation at break,and conductivity of the cellulose organohydrogel reach 93%,242%,and 1.92 S/m,as well as excellent anti-freezing property down to-54.3 ~oC,potential as flexible conductive device in harsh conditions.When demonstrated as energy storage device,the cellulose organohydrogel based supercapacitor demonstrates excellent supercapacitor performances,durability against deformation and resistance to low temperature.When demonstrated as energy harvesting device,the cellulose organohydrogel based triboelectric nanogenerator displays stability,and resistance to both low temperature and a large number of operation cycles.As the cellulose based triboelectric nanogenerator is integrated with cellulose based supercapacitor,a flexible and anti-freezing self-charging power system is built,capable of driving miniaturized electronics,demonstrating great potential as wearable power system in harsh conditions.A flexible,stretchable,and high-performance all-in-one supercapacitor was fabricated by in situ growth of polyaniline onto a cellulose hydrogel electrolyte from regenerating cross-linked cellulose network in phytic acid.The as-prepared supercapacitor showed high areal capacitance of 1210.7 m F/cm~2 at a current density of1 m A/cm~2,maximum energy density of 168.2μWh/cm~2 and maximum power density of 669.1μW/cm~2,outperforming the reported flexible all-in-one supercapacitors.The capacitance also retained 89%after 1000 bending cycles,due to the excellent mechanical property.On the other hand,the cellulose/phytic acid/polyaniline hydrogel also demonstrated great potential as strain sensor.After structured,the cellulose-based strain sensor demonstrated a high gauge factor up to 20.74,capable of detecting most human activities with high sensitivity and durability.The current devices based on cellulose are ideal candidate as wearable electronic devices in real-life scenarios.Due to the natural abundance,renewability,and environmental friendliness,biomass is regarded as a sustainable candidate for the fabrication of energy storage devices.However,the huge number of livestock produce countless animal-derived teeth,which always end up in the environment without any scientific intervention,leading to a vast waste.Herein,tooth-derived supercapacitor was fabricated for the first time.The demineralized tooth with 3D collagen matrix were applied as flexible gel electrolyte,while calcination of the demineralized tooth led to porous carbon as electrode.The preserved aligned tubular hierarchy typically promoted the ion transport in the gel electrolyte,and the multi-scaled porous structure favored the ion adsorption on the electrodes.The tooth-derived supercapacitor thus demonstrated excellent performance among the top class of the reported biomass-based supercapacitors,with high specific capacitance of 131.7 m F/cm~2,capacitance retention of 84.6%after 6000charging-discharging cycles and capacitance retention of 90.1%after 600 times bending.The present work opens a novel approach for the interdisciplinary and sustainable utilization of biomass in the field of energy storage.Supercapacitors based on natural polymer hydrogel were successfully developed in this thesis.The problem of using restricted supercapacitors under harsh conditions is solved by simply processing the hydrogel preparation process,imparting high conductivity,antifreeze,flexibility,and so on.The all-in-one supercapacitor solves the electrode-electrolyte contact problem,resulting in a significant increase in supercapacitor capacitance.Finally,the discarded biomass material is processed to create a supercapacitor produced from teeth.Natural polymer hydrogels have greatly broadened the spectrum of applications for supercapacitors,as well as providing new ideas for green chemistry and sustainable development,with tremendous academic innovation and practical application potential.