A lithium-sulfur cell includes a lithium-containing anode, a sulfur-containing cathode and a separator arranged between the lithium-containing anode and the sulfur-containing cathode. A first semiconductor layer is formed over a substrate, and a second semiconductor layer is formed over the first semiconductor layer. After dry etching a vertical groove, a dielectric layer is grown on the surface of the silicon substrate to protect the vertical wall, preventing the groove from getting wider due to subsequent wet etching. The material retains heat to assist in styling of the hair. In addition, a method for manufacturing the bag is disclosed.