Preparation Of TiO_xN_y Thin Film Flexible Supercapacitors Based On The Polyimide Substrate

As the size of electronic devices tends to be miniaturized and the reliability of wireless communication protocols(Bluetooth,Wi-Fi,etc.)has improved,new fields have been opened up for the application of wireless Io T sensors,such as smart wear,medical care,etc.In the field of smart wear,in order to maintain the long-term stable operation of wireless Io T sensors,higher requirements are put forward on energy supply units.Normally,it is not only necessary to have good energy storage characteristics,but also to meet the requirements of flexibility.Supercapacitors are regarded as ideal replacements for lithium-ion batteries due to their long cycle life and high power density.At present,facing the field of smart wear,most flexible supercapacitors have the problems of immature preparation technology and low energy density.Therefore,it is of great significance to carry out research on the manufacturing process and energy density improvement of flexible supercapacitors.In this paper,TiN collector thin films were prepared on Si substrate by RF reactive magnetron sputtering.The effect of substrate bias on the performance and structure of TiN collector was investigated.The resistivity,chemical composition,preferred orientation,surface morphology and film uniformity of TiN collector were characterized by four-point-probe,XPS,GIXRD and AFM,and the preparation process was transferred to polyimide substrate.Secondly,the Ti O_xN_y thin film electrode was prepared by DC reactive magnetron sputtering on the TiN current collector film prepared on polyimide substrate.The effects of substrate temperature and working pressure on the microstructure and electrochemical performance of the Ti O_xN_y thin film electrodes were systematically investigated.The preferred orientation,morphology,resistivity,thickness and electrochemical performance of Ti O_xN_y thin film electrodes were characterized by GIXRD,FIB-SEM,four-point-probe,step tester and electrochemical workstation.Finally,an all-solid-state flexible micro-supercapacitor was prepared and subjected to electrochemical characterization analysis.The main research results are as follows:First,a TiN current collector film with ultra-low resistivity is prepared by the RF reactive magnetron sputtering.When a substrate bias of-200V is applied,the lowest resistivity value of the TiN current collector is 27.3??·cm.By transferring this process to a polyimide substrate,the TiN film can also maintain an ultra-low resistivity level.Secondly,the direct current reactive magnetron sputtering is used to obtain a Ti O_xN_y thin film electrode with a higher specific surface area by optimizing the substrate temperature and working pressure.In the electrochemical test,the maximum specific capacitance of the electrode is 13.15 m F·cm^-2.In addition,by introducing a Ti buffer layer and using a plasma cleaning method,the film-base bonding force is improved,the problem of film cracking on the flexible substrate is solved,and the flexibility of the film electrode is improved.Finally,filter paper soaked in 1 M KCl solution is used as the solid electrolyte,and the TiN current collector/Ti O_xN_y flexible film electrode was assembled into an all-solid flexible micro-supercapacitor.The electrochemical test results show that the different bending angles of the device have little effect on its electrochemical performance.After the series-connected device is charged,the small light-emitting diode can be lit for 15 s.The above test results show that the device has the potential to be used in practical application.