Difference Between Lithium Ion and Lithium Sulfur Batteries

Lithium-sulfur battery is a kind of lithium battery, and the practical process has not yet been fully realized. Lithium-sulfur batteries use sulfur as the positive electrode of the battery and lithium metal as the negative electrode. Many characteristics are better than those of the widely used lithium batteries. However, due to the difficulty of practical application, they are rarely used at present.
Lithium-sulfur battery is a kind of lithium battery, which is still in the scientific research stage as of 2013. A lithium-sulfur battery is a kind of lithium battery with sulfur as the positive electrode of the battery and metal lithium as the negative electrode. The specific capacity is as high as 1675mAh/g, which is much higher than the capacity of the widely used lithium cobalt oxide battery (<150mAh/g). And sulfur is an environmentally friendly element, which basically does not pollute the environment, and is a very promising lithium battery.
Chinese name: Lithium-sulfur battery
Specific capacity: up to 1675mAh/g
Battery positive electrode: sulfur element
Battery negative electrode: lithium metal
Lithium-sulfur batteries use sulfur as the positive electrode reaction material and lithium as the negative electrode. During discharge, the negative electrode reaction is that lithium loses electrons and becomes lithium ions, and the positive electrode reaction is that sulfur reacts with lithium ions and electrons to form sulfides. The potential difference between the positive electrode and the negative electrode reaction is the discharge voltage provided by the lithium-sulfur battery. Under the action of an applied voltage, the positive and negative reactions of the lithium-sulfur battery are reversed, which is the charging process. According to the amount of electricity that the unit mass of elemental sulfur can completely change into S2-, the theoretical discharge mass specific capacity of sulfur can be obtained as 1675mAh/g. Similarly, the theoretical discharge mass specific capacity of elemental lithium can be obtained as 3860mAh/g. The theoretical discharge voltage of a lithium-sulfur battery is 2.287V, when sulfur reacts completely with lithium to form lithium sulfide (Li2S). The theoretical discharge mass specific energy of the corresponding lithium-sulfur battery is 2600 Wh/kg.
The charge and discharge reactions of sulfur electrodes are complex, and as of 2013, there is no clear understanding of the intermediate products produced by sulfur electrodes during the charge and discharge reactions. The discharge process of the sulfur electrode mainly includes two steps, corresponding to two discharge platforms respectively. The ring structure of S8 changes to the chain structure of Sn2- (3≤n≤7) ions, and combines with Li+ to form Li2Sn. This reaction corresponds to the discharge platform near 2.4-2.1V on the discharge curve. The chain structure of Sn2- ions changes to S2- and S22- and combines with Li+ to generate Li2S2 and Li2S. This reaction corresponds to a longer discharge platform near 2.1-1.8V in the discharge curve, which is the main discharge region of lithium-sulfur batteries. . During discharge, it is located in the potential range of 2.5-2.05V, which corresponds to the reduction of elemental sulfur to form soluble polysulfides and further reduction of polysulfides. The potential range of 2.05-1.5V corresponds to the reduction of soluble polysulfides to form lithium sulfide solid-state films. Covered on the surface of the conductive carbon substrate. During charging, Li2S and Li2S2 in the sulfur electrode are oxidized to S8 and Sm2- (6≤m≤7), and cannot be completely oxidized to S8. This charging reaction corresponds to a charging platform near 2.5-2.4V in the charging curve.