Preparation And Electrochemical Performance Of Zeolite/S Cathode Composite For Lithium/Sulfur Battery

Lithium-sulfur batteries are considered as one of the most promising secondary battery system compared to the traditional secondary battery. Theoretical specific capacity of lithium-sulfur batteries is as high as 1675 mAh/g, and corresponding theoretical energy density is 2600 wh/kg. These advantages make lithium-sulfur batteries become a research hotspots. But now lithium-sulfur batteries still exist many problems, such as polysulfides’ s solubility and the large volume deformation of sulfur positive. Strong adsorption ability and developed void space structure of the materials were used to alleviate the above problem. Zeolite is a natural mineral material with strong adsorption, which was used to be an absorbent of sulfide in productions of chemical industry. And strong adsorption ability and rich gap can restrict the dissolution and migration of polysulfides. In this work, zeolite/S and modified zeolite/S and 13X-zeolite/S composites were prepared. The structure, morphology and pore size of the composite were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM) and Brunauer Emme-Teller(BET) techniques. The electrochemical properties of the composites were analyzed by charge-discharge, electrochemical impedance spectroscopy tests and Cyclic Voltammetry.Firstly, this paper verifies the feasibility of natural zeolite/S as the lithium battery cathode material. Zeolite/S composite with 40% sulfur was prepared by heat treatment with using sulfur and zeolite. The electrochemical results showed that initial recycling specific capacities was 950.6 mAh/g when charged-discharged at 0.2 C, and after 100 cycles, the specific capacities was 583.6 mAh/g, which was 61.3% of the initial cycle.The zeolite pore size distribution was broaded and the adsorption ability was improved by acid-washing and salt-washing as the small specific surface area of zeolite. Zeolite/S acid-washed zeolite/s and salt-washed zeolite/s composite with different sulfur content(40%、50%、60%) for lithium-sulfur batteries were attained by heat treatment using sulfur and zeolite. Among the three kinds of materials the best electrochemical performance showed in 40% sulfur injection. The first specific discharge capacity of three composites were 950.7、1068.1 and 1116.8 mAh/g, respectively. The results indicated that salt-washed zeolite/S showed the best electrochemical performance. It is observed that the cycling performance of the Li–S batteries with salt-washed zeolite is better than that without salt-washing. And this method is simple with short preparation period.Using 13X-zeolite molecular sieve as the carrier of the positive sulfur,the specific surface area of 13X-zeolite molecular sieve was 223.05 m2/g. 13X-zeolite/S composite with 40% sulfur was prepared by heat treatment using sulfur and 13X-zeolite. The electrochemical results show that initial recycling specific capacities was 1284.3 mAh/g when charged-discharged at 0.2 C, and after 200 cycles, the specific capacities was 850.9 mAh/g, which was 66% of the initial cycle, suggesting that the excellent cycle performance of 13X-zeolite /S composite.