High Capacity Li/S Battery for Advancing Commercialization

Rechargeable Li/S batteries are promising candidates for portable electronics, electric vehicles and energy storage system due to their high specific energy and low cost.  Many researchers have reported remarkable results in this area, but there are still huge obstacles for commercialization in terms of sulfur loading level for higher specific energy and higher stabilization for lithium metal anode. To solve these problems, we have researched with two aspects. One is attempting to realize highly loaded sulfur cathode with large utilization by impregnating carbonaceous conductive network with nano-sized sulfur.  The other is preventing sulfide-shuttle by separator coated with negatively charged material. 

Using nano-sized sulfur has advantages not only for increasing networks for sulfur-carbon, but also for obtaining enough space against expansion during lithiation.  Furthermore, the conductive network of sulfur-carbon can be more stably maintained with cycling which gives long life span as compared to micro-sized sulfur cathode.  Nano-sulfur was fabricated using the conventional milling process in water added with glycerol.  Ketjen Black with high surface area and aqueous PVP-PEO mixture were used as a conductive material and binder respectively.  Finally, cathode electrodes were prepared with high sulfur contents of 70 wt% and elevated sulfur loading of 3.0 mg/cm². Electrochemical measurements were carried out using CR2032 coin-type cell system.  Initial specific capacity and capacity retention were more than 1,000mAh/g(sulfur) and 80% after 100 cycle respectively. Adapting separator coated with negatively charged moiety significantly decreased the over-charging. This phenomenon can be interpreted as an effect of the negative moiety on separator to repulse the soluble polysulfides which move toward the surface of anode.

   Detailed properties up to 300 cycles for pouch cell will be discussed. We believe that the nano-sized sulfur and separator coated with negative moiety can be helpful to advance the commercialization of lithium sulfur battery with high specific energy density more than 300Wh/kg.