Application Of Biochars In Li-S Battery

In the recent years, the research about lithium sulfur battery becomes more and more popular in the area of energy storage. The essential reason is attributed to its quite high capacity while the other battery systems without. What is more, sulfur is a kind of abundant natural resource which is friendly to the environment at the same time. However, because of its insulated feature, sulfur cannot be used as the battery cathode directly. That means the application of sulfur must be combined with variety of measures and conductive skeleton materials. Besides, the reaction between sulfur and lithium is very complicated which result in many new problems occurred while the other battery systems haven’t.Activated carbon is one of the conductive skeleton materials which can load sulfur. It is a kind of traditional conductive materials with well-developed porous construction and gigantic surface area. These characters make it well used in the lithium sulfur battery. There are a lot of methods and raw material source to produce activated carbon. If derived from crop waste and then applied in lithium sulfur battery to turn the waste to treasure, it would be very worthwhile.This work uses walnut shell, peanut shell and pistachio-nut hull respectively as the raw material and Zn Cl2 as the activator through chemical activation to produce activated carbon at a relatively low temperature. After compositing the three activated carbons with sulfur, we got AC/S composites respectively and assembled them into coin batteries. Then we tested their behavior thoroughly and comprehensively. The test results indicate:(1) The three biochars all have gigantic specific surface area and abundant pore structure. But they are quite different from each other. One is layer structure, such as pistachio shell activated carbon. The second one is round hole structure, such as walnut shell activated carbon. And the third one is long flat hole structure, such as peanut shell activated carbon.(2) The three kinds of activated carbons have different constructions. At 0.2C, the initial discharge capacities of the three compounds are 685 m Ah/g for pistachio shell biochar, 900.2 m Ah/g for walnut shell biochars and 961 m Ah/g for peanut shell biochar. After cycled for 100 times,they still keep at 476.6 m Ah/g, 579.45 m Ah/g and 712.18 m Ah/g respectively. This result indicates that the peanut shell activated carbon structure is the most suitable for the Li-S battery.(3) We combined the three activated carbons together and made them into a so-called composite activated carbon. The composite activated carbon includes the three biochars at a rate of 1:1:1. In the hope of getting a better capacity, we test the composite activated carbon with various methods. The results tell us this idea is available,its initial discharge capacity is 1104.7 m Ah/g, 100 times of cycling later, it is 742 m Ah/g. After 500 times of cycling, it still keeps at 340 m Ah/g.In summary, the preparation of the lithium-sulfur battery cathode is very simple, environment friend and the experimental conditions are not hard to get. The preparation cycle time is short. Besides, the cost of the cathode preparation is quite cheap. The research we did here conclude the relationship between the biochars structure and battery capability and is beneficial for exploring the commercialization of power lithium-sulfur battery.