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kunal
kunal • Jul 5, 2011

Sulphur Can Enhance Lithium Battery’s Capacity To Drive EVs

Stanford University researchers have found out a way to boost the efficiency and performance of the good old lithium battery. Almost everything electronic gadget and equipment that we use today is wireless. And more and more things are becoming portable so that we can use them anytime, anywhere on the move. All these portable wireless devices are powered by the Lithium batteries. Almost everyone today has at least one lithium battery in his/her possession. However, a big problem with these lithium batteries is that they tend to discharge quickly and so they can’t be used for heavy duty devices. For example, consider the case of electric vehicles which are in vogue now days, thanks to the global warming and rising carbon footprints. These eco friendly modes of transport can’t be powered by the lithium batteries. They main reason for the inability of the batteries to release enough power time and again is its cathode design. The materials used for anode like graphite and silicon have high specific capacities of 370 mAh/g and 4200 mAh/g respectively. On the contrary, the specific capacity for the cathode components is much lower (170 mAh/g for LiFePO4 and only 150mAh/g for layered oxides).
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So the solution to this problem is to improve the cathode specific density while maintaining the better features of the battery such as the excellent cycle life and satisfactory energy efficiency. Now, Hailiang Wang and his fellow scientists at Stanford University claim that they have cracked a solution to this problem by simply choosing sulphur as the cathode material. Well, it’s an established fact that sulphur has high specific capacity of around 1672 mAh/g. However, the skeptics will tell you that it also has a number of drawbacks such as poor conductivity, property of swelling in discharge cycle that causes it to crumble down, etc. However, all these negative features of sulphur have been done away with by using little nanoengineering. Wang and co makes submicron size sulphur particles and coats these articles with a plastic called PEG (polyethyleneglycol). This plastic coat prevents the polysulphides from crumbling and holds them together like an adhesive. After this, the tiny coated sulphur particles are enclosed in a trap like graphite cage. There occurs a reaction between the two that makes the cathode conduct better. Also, the cage supports the particles when they swell and shrink during the charging and discharging cycles.

This new innovative cathode design is capable of retaining specific capacity of 600 mAh/g over 100 charging cycles. This much enhanced capacity is impressive. Also, the batteries that will have such cathodes can boast of a much higher energy density than their counterparts. However, the Stanford scientists believe that there is much more work to be done for optimizing this material. Their next target is to develop a working model for such a battery. If this prototype successfully demonstrates all their claims then it might be the best alternative for your EV.

Source: Technology Review

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