Study On Electrode Materials Of Supercapacitors Based On Nano-TiO₂

With the improvement of economic level and quality of life,the demands for portable electronic equipment and electric vehicles are increasing.So it is urgent to develop an advanced energy storage system with high performance、low cost and friendly environment.Chemical cells、supercapacitors（SCs）and fuel cells are three unconventional energy devices based on electrochemical energy conversion.SCs fill in the gap between batteries and common capacitor energy storage devices,and have become a hot research topic of energy storage devices today.TiO₂ is usually used as electrode materials of supercapacitors instead of precious metals such as Ru O₂,because of its low cost、non-toxic、chemical stability.However,due to the low conductivity of TiO₂,its specific capacitance and electrochemical stability are poor.So improving the performance of TiO₂ electrode materials is the focus of current research.The main contents and results of this paper are as follows:（1）、We prepared nano-TiO₂ particles with different sizes by sol-gel method.The morphology and structure of nano-TiO₂ were characterized by XRD and SEM.The results showed that the TiO₂ was composed of many nanoparticles,and the TiO₂ prepared with HCl as inhibitor was smaller than that prepared with C₂H₄O₂.（2）、The electrochemical performance of nano-TiO₂ was tested by three-electrode system.The results showed that the testing atmosphere had a great influence on the electrical properties of TiO₂.In the air atmosphere,the coulomb efficiency of TiO₂ was only26%（10 m V/s）.In N₂ atmosphere,the coulomb efficiency of TiO₂ increased obviously,reaching 67.4%at the same scan rate.There was an obvious redox current peak on the CV curves,which indicated that TiO₂ was a pseudo-capacitive electrode material.The calculation results of GCD showed that the specific capacitance of TiO₂electrode material under HCl condition was the largest,which was 27.49 F/g,it was 5 times as much as commercial TiO₂ specific capacitance.（3）、Nano-TiO₂ prepared with HCl as inhibitor was combined with activated carbon by ball milling method,and TiO₂@AC composite electrode materials with coated structure were prepared.Electrochemical test showed that the CV curves of TiO₂@AC were like rectangles,and there was a peak of oxidation-reduction current at the same time,which indicated that there were both pseudo-capacitance and double-layer capacitance behaviors in TiO₂@AC electrode materials.The result of EIS indicated that the composites of activated carbon and nano-TiO₂ greatly increased the conductivity of nano-TiO₂.So the specific capacitance of TiO₂@AC reached 139.05 F/g,and its specific capacitance was larger than that of TiO₂ prepared by sol-gel method at almost all current densities.The results indicated that the composites of activated carbon had a good effect on the improvement of electrochemical performance of nano-TiO₂.（4）、We assembled hybrid supercapacitors（TiO₂//AC、TiO₂@AC//AC）with active carbon as positive electrode and TiO₂、TiO₂@AC as negative electrode respectively.And we studied the electrochemical properties of two kinds of hybrid capacitors.The results showed that after 500 cycles,the specific capacitance of TiO₂//AC was 82%of the initial specific capacitance,and the coulomb efficiency fluctuated greatly.However,the coulomb efficiency of TiO₂@AC//AC was basically stable at 96.7%,and the specific capacitance was almost unchanged,which was 19.15 F/g,it was 4.2 times as much as the specific capacitance of TiO₂//AC hybrid device.