| With the strong support of our country for the new energy fields,the lithium-ion battery market is developing rapidly.And the prices of lithium carbonate,lithium hydroxide and other lithium salt in the upstream industry are rising.Due to the abundant reserves of sodium elements,the prices of raw materials in sodium are low.Because the sodium and lithium elements belong to the first main family,the chemical properties between them are similar.So in the long term,the development of sodium-related energy storage equipment is very promising for the future.In this paper,we mainly study the aqueous sodium hybrid supercapacitor of NaTi2(PO4)3/C//AC,which using aqueous electrolytic solution to improve the ionic conductivity of the electrolyte.Because the aqueous solution itself has the characteristics of flame retardant,the using process can eliminate the security risks of combustion,explosion and so on.The anode electrode material of the supercapacitor is NaTi2(PO4)3,but the intrinsic electron conductivity of NaTi2(PO4)3 is low,so the electrical conductivity of NaTi2(PO4)3 is improved by coating the conductive material.In this paper,the nanoparticles of NaTi2(PO4)3/C composite is synthesized by the technology of carbon coating in the liquid phase,which can improve the electron conductivity and shorten the ion diffusion path.And this synthesized way improved the cycling performance of the NaTi2(PO4)3.We used in-situ carbon coating in the liquid phase to synthesis the nano-carbon coating NaTi2(PO4)3/C composite,and the products were tested by XRD analysis,Raman Spectroscopy,thermogravimetric analysis,scanning electron microscopy,transmission electron microscopy and electrochemical performance analysis.Compared with NaTi2(PO4)3/C composite synthesized by solid phase method,the electrochemical performance of NaTi2(PO4)3/C composite through the synthesis in-situ carbon coating in the liquid phase was better.In those experiments,we found that:the NaTi2(PO4)3/C composite synthesized by in-situ carbon coating in the liquid phase have the amorphous carbon surface,and thickness of carbon is about 2 nm.The morphology of NaTi2(PO4)3/C particles are irregular sphere.The NaTi2(PO4)3/C particles crosslink to form a porous structure,and the sizes of those particles are from 20 nm to 100 nm.In order to remove the influence of oxygen to the electrochemical properties of NaTi2(PO4)3/C composite,we improve the device.We used Solartron electrochemical workstation to test the cyclic voltammetry curves of NaTi2(PO4)3/C composite in different scan rates.When the scan rate of 0.1 mV s-1,the voltage from-1.1?-0.4 V,the cyclic voltammetry curves arise the peak potentials of-0.86 V and-0.78 V,corresponding to the oxidation and reduction of Ti4+/Ti3+.When the scanning speed increases,the redox peaks are evident,indenting the NaTi2(PO4)3/C composite had good cycle stability.When constant-current charging and discharging in the current of 1 C rate,the discharge capacity of the NaTi2(PO4)3/C composite reached 122 mAh g-1.When constant-current charging and discharging in the current of 15 C rate,the discharge capacity maintained at 88 mAh g-1.The NaTi2(PO4)3/C composite shows an excellent cycling stability with the retention of 60%of the initial capacity after 1000 cycles at a rate of 10 C.The supercapacitor was prepared with anode of the NaTi2(PO4)3/C composite,the cathode of activated carbon,the electrolyte 1 mol L-1 Na2SO4,and the weight ratio of active materials(NaTi2(PO4)3/C//AC)was 2.2.The as-fabricated device was then cycled between 0.15?1.4 V with different current density.Our results show the power density of 121.15 W kg-1 with specific energy of 18.71 Wh kg-1 at the current density of 0.5 A g-1.Moreover,the specific energy and power density goes to 14.1 Wh kg-1 and 2.42 W kg-1 at a higher current density of 10 A g-1.More importantly,the device showed an excellent cycling stability with the retention of 76%after 1000 cycles at a current density of 1 A g-1.This research shows the designed aqueous sodium hybrid supercapacitor has the potential to be used as auxiliary high-power energy storage device for the practical applications. |
PDF Full Text Request