What is the difference between lithium ion battery and lithi

 news     |      2021-12-03 15:49

Lithium-sulfur battery is a kind of lithium battery, and the practical process has not yet been fully realized. Lithium-sulfur battery is a kind of lithium battery with sulfur element as the positive electrode of the battery and metal lithium as the negative electrode. Many characteristics are better than the widely used lithium batteries, but because of the difficulty of practical application, there are few applications at present.

Lithium-sulfur battery is a type of lithium battery, which is still in the scientific research stage as of 2013. Lithium-sulfur battery is a kind of lithium battery in which sulfur is used as the positive electrode of the battery and metal lithium is used as the negative electrode. The specific capacity is as high as 1675mAh/g, which is much higher than the capacity of lithium cobalt oxide batteries that are widely used commercially ("150mAh/g). In addition, sulfur is an environmentally friendly element and basically does not pollute the environment. It 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. When discharging, the negative electrode reaction is that lithium loses electrons and becomes lithium ions. The positive electrode reaction is the reaction of sulfur with lithium ions and electrons to generate sulfide. The potential difference between the positive electrode and the negative electrode is the discharge voltage provided by the lithium-sulfur battery. Under the action of an external voltage, the positive and negative electrodes of the lithium-sulfur battery react in reverse, which is the charging process. According to the amount of electricity that the unit mass of elemental sulfur can completely change to S2-, it can be concluded that the theoretical discharge mass specific capacity of sulfur is 1675mAh/g, and the theoretical discharge mass specific capacity of elemental lithium is 3860mAh/g. The theoretical discharge voltage of a lithium-sulfur battery is 2.287V, when sulfur and lithium completely react to form lithium sulfide (Li2S). The theoretical discharge mass specific energy of the corresponding lithium-sulfur battery is 2600Wh/kg.

The charging and discharging reactions of sulfur electrodes are complicated. As of 2013, there is no clear understanding of the intermediate products produced in the charging and discharging reactions of sulfur electrodes. The charge-discharge reaction of the lithium negative electrode and the sulfur positive electrode is shown in formula (1-1) to formula (1-4). The discharge process of the sulfur electrode mainly includes two steps, corresponding to two discharge platforms respectively. Formula (1-2) corresponds to the ring structure of S8 to become a chain structure of Sn2-(3≤n≤7) ions, and combines with Li+ to form Li2Sn. This reaction corresponds to the discharge near 2.4-2.1V on the discharge curve. platform. Formula (1-3) corresponds to the chain structure of Sn2- ions becoming S2- and S22- and combining with Li+ to produce Li2S2 and Li2S. This reaction corresponds to the longer discharge platform near 2.1-1.8V in the discharge curve. This platform is The main discharge area of lithium-sulfur batteries. YuanLixia et al. studied the electrochemical reaction process of sulfur cathode in lithium-sulfur batteries. They believe that the potential range of 2.5-2.05V during discharge corresponds to the reduction of elemental sulfur to form soluble polysulfides and further reduction of polysulfides, and the potential range of 2.05-1.5V corresponds to the reduction of soluble polysulfides to form lithium sulfide solid film. , It covers the surface of the conductive carbon substrate. During charging, Li2S and Li2S2 in the sulfur electrode are oxidized by 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.