| In recent years, renewable energy have gotten development rapidly in the world. Energy storage technology of large-scal is the key to solve the renewable energy and the core of technology.Due to abundant resources of sodium, sodium ion batteries are considered to be the best choice for the next generation of secondary batteries. Aqueous rechargeable sodium ion batteries use inorganic salt solution as electrolyte.It offers safer operation, higer conductivity and low-cost production. So this work we used the cathode material NaTi2（PO4）3 as the research subject. We selected the best synthesis temperature, we did some proper modification, we studied the electrochemical performance of the batteries used the NaTi2（PO4）3 as aqueous sodium ion battery cathode materials.We prepared the cathode material sol-gel. The results indicate that the best synthesis temperature is 700 ℃, which select from the different calcination temperatures 600℃, 700℃, 800℃, 900℃. The phase of NaTi2（PO4）3 cathode material synthesis at this temperature is pure. CV test comparison results show that the material calcinate at 700℃ possess better cycle reversibility and the strongest the redox peaks, which the materials at different calcination temperature placed in the 1mol/L Na2SO4 aqueous solution. The electrochemical properties in 1mol/L Na2SO4 aqueous solution is favorable. It is similar to the electrochemical behavior in other works reported.We prepared hierarchical porous structured NaTi2（PO4）3 by a facile self-assembled strategy. The electrochemical properties of materials have been characterized by CV curves and galvanostatic charge/discharge curves. Compared with the reference samples, the results show that the hierarchical porous structure material we prepared act out the best electrochemical performance. The diffusion coefficient of the materials reach to 10-12-10-13cm2/s, much higher than the reference samples. Specific capacity of 129.4mAh·g-1 and 114mAh·g-1 with flat potential plateau are obtained for the materials at 1C and 2C rate. The results show that the materials at the 2C rate after 300 cycles obtained specific capacity 92 mAh·g-1, the coulombic efficiency of the cell finally stabilizes at nearly 100% during the cycles. Both CV and galvanostatic charge/discharge results demonstrate its improved sodium intercalation capability, high rate capability and superior cycling stability as compared to the reference samples.In this work, a facile preform impregnation strategy is employed to synthesis NaTi2（PO4）3 array. Compared with the reference samples, the electrochemical properties of materials have been characterized by CV curves and galvanostatic charge/discharge curves. As characterized by EIS, the results display that the NaTi2（PO4）3 array possess the lower resistance and good conductivity. Moreover, it has better electrochemical performance and superior cycling stabilily. A full aqueous sodium ion battery is assembled based on the anode material of prepared NaTi2（PO4）3 array. It exhibits excellent cycling stability. It is capable of long term cycling at both rates, which retains 70% of the capacity after 1000 cycles at alternate 10 C and 60 C and retains 84% of the capacity after 500 cycles at 1C with nearly 100% coulombic efficiency, which is among the best of state-of-the-art aqueous sodium ion systems. In addition, the core-shell composite structure provides a new strategy for the study of high performance polyanion material. |
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