Lithium-sulfur battery is a kind of lithium battery, and it has not yet fully realized the practical process. Lithium-sulfur battery is a kind of lithium battery with sulfur element as the positive electrode of the battery and lithium metal as the negative electrode. Many characteristics are better than the lithium battery which is widely used nowadays. However, due to the difficulty of practical use, it is rarely used at present.
Lithium-sulfur battery introduction Lithium-sulfur battery is a kind of lithium battery, and it is still in the research stage as of 2013. A lithium-sulfur battery is a lithium battery in which a sulfur element is used as a positive electrode of a battery and lithium metal is used as a negative electrode. The specific capacity is as high as 1675 mAh/g, which is much higher than the capacity of the widely used lithium cobalt oxide battery ("150 mAh/g"). And sulfur is an environmentally friendly element that has no pollution to the environment and is a very promising lithium battery.
Chinese name: lithium sulfur battery
Specific capacity: up to 1675mAh / g
Battery positive: sulfur element
Battery negative: metal lithium
Lithium-sulfur batteries use sulfur as the positive reaction substance and lithium as the negative electrode. When the discharge is negative, the negative electrode reacts with lithium to lose electrons and becomes lithium ions. The positive electrode reacts with sulfur to react with lithium ions and electrons to form sulfides. 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 the applied voltage, the positive and negative electrodes of the lithium-sulfur battery react in reverse, which is the charging process. According to the unit mass of elemental sulfur completely changed to the amount of electricity that can be supplied by S2-, the theoretical discharge mass ratio of sulfur is 1675 mAh/g. Similarly, the theoretical discharge mass ratio of elemental lithium is 3860 mAh/g. . The theoretical discharge voltage of a lithium-sulfur battery is 2.287V when sulfur is completely reacted with lithium to form lithium sulfide (Li2S). The theoretical discharge mass specific energy of the corresponding lithium-sulfur battery is 2600 Wh/kg.
The charging and discharging reactions of the sulfur electrode are complicated, and as of 2013, there is no clear understanding of the intermediate products produced by the sulfur electrode in the charging and discharging reactions. The charge-discharge reaction of the lithium negative electrode and the sulfur positive electrode is as shown in the formula (1-1) to the formula (1-4), and the discharge process of the sulfur electrode mainly comprises two steps corresponding to two discharge platforms. The formula (1-2) corresponds to the chain structure of Sn2-(3≤n≤7) ions in the ring structure of S8, and combines with Li+ to form Li2Sn, which corresponds to a discharge near 2.4-2.1V on the discharge curve. platform. The chain structure of the formula (1-3) corresponding to the Sn2- ion becomes S2- and S22- and combines with Li+ to form Li2S2 and Li2S, which corresponds to a longer discharge platform near the 2.1-1.8V in the discharge curve. The main discharge area of lithium-sulfur batteries. Yuan Lixia et al. studied the electrochemical reaction process of sulfur positive electrode in lithium-sulfur battery. They believe that the potential interval of 2.5-2.05V during discharge corresponds to the reduction of elemental sulfur to form soluble polysulfide and polysulfide, and the potential interval of 2.05-1.5V corresponds to the reduction of soluble polysulfide 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 S8 and Sm2-(6≤m≤7), and cannot be completely oxidized to S8. The charging reaction corresponds to a charging platform near 2.5-2.4V in the charging curve.
