Study On The Properties And Mechanism Of A General Binder For High-Areal-Capacitance Supercapacitor

Supercapacitor is an emerging energy storage device.Due to its high power density and high cycle stability,supercapacitor has received wide attention from scientists.However,low areal capacitance and energy density have restricted its practical application.There are some common problems in current methods for increasing areal capacitance and energy density of supercapacitors,such as high cost and tedious steps.Binder is one of the most important components of supercapacitors,which can keep the electrode structure stable and promote the conduction of electrolyte ions.However,current binders generally have many drawbacks,such as insufficient cohesiveness and poor mechanical strength,which restrict the preparation of capacitors with high load and high surface capacitance.Bacterial Cellulose(BC)can be an ideal capacitor binder material because of its low production cost,stable structure and high mechanical strength.From above,this work employed BC nanofibers as binders to design high-areal-capacitance supercapacitor structures,and conducted a thorough study on its electrochemical properties and the generality of BC nanofiber as binders.First of all,BC nanofibers have good mechanical properties,and abundant surface hydroxyl groups can form a strong van der Waals force with the electrode material.As a result,the prepared self-supporting electrode structure achieved a high loading of 55.4 mg/cm2(equal to active material loading of 44.3 mg/cm2).Secondly,the abundant hydroxyl groups on the surface of BC nanofibers have good affinity with the electrolyte,which can promote the conduction of electrolyte ions in the electrode,thus maintain the specific capacity of 211.4 F/g and achieve a high areal capacitance of 10.4 F./cm2.The BC nanofiber binder exhibits structural and performance advantages over conventional binders,such as PVDF,CMC,and PVA.The specific surface area and electrochemical performance tests show that the unique fiber structure of BC does not affect the pore structure and specific surface area of the electrode material,and the intrinsic capacitance performance of the electrode material can be maximized.In addition,supercapacitors prepared from BC nanofibers and various commercial activated carbons(Kuraray activated carbon and Norit activated carbon)exhibit superior performance over conventional binders,further demonstrating the commercial application prospects of BC nanofibers as binders.