3.7v battery 18650

　　3.7v battery 18650 research and development has made breakthrough progress, and the commercialization process is expected to accelerate

　　The researchers discovered a cobalt-based compound sulfur-containing material with smaller polarization phenomenon in the cathode material and better rate performance. Even at 40 degrees, the power density is nearly four times higher than the currently known highest power density. The research results were recently published in the top international energy materials journal "Joule".

　　It is reported that the national "Energy Technology Revolution Innovation Action Plan (2016-2030)" proposes to break through high-safety, low-cost, long-life solid-state lithium battery technology, as well as 3.7v battery 18650 technology with an energy density of 300Wh/kg, low-temperature Sodium sulfur energy storage battery technology. According to the industry, lithium-sulfur batteries have the advantages of rich element reserves and low cost, and are a new generation of batteries with great development prospects.

　　With the successive breakthroughs in important 3.7v battery 18650 technologies and the promotion of new energy vehicles, the commercialization process of lithium-sulfur batteries is expected to accelerate, and companies that take the lead in deploying related technologies are expected to seize market opportunities.

　　3.7v battery 18650 is a type of lithium-ion battery and is still in the scientific research stage as of 2013. 3.7v battery 18650 is a lithium-ion battery that uses sulfur as the positive electrode of the battery. The specific capacity is as high as 1675mAh/g, which is much higher than the capacity of lithium cobalt oxide batteries widely used commercially (<150mAh/g). Moreover, sulfur is an environmentally friendly element and has basically no pollution to the environment. It is a very promising lithium-ion battery.

　　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. The positive electrode reaction is that sulfur reacts with lithium ions and electrons to form sulfide. The potential difference between the positive electrode and the negative electrode reaction is the discharge voltage provided by the 3.7v battery 18650. Under the action of external voltage, the positive and negative electrode reactions of lithium-sulfur batteries proceed in reverse direction, which is the charging process. Based on the amount of electricity that can be provided by unit mass of elemental sulfur completely transformed into S2-, the theoretical discharge mass specific capacity of sulfur is 1675mAh/g. Similarly, the theoretical discharge mass specific capacity of elemental lithium is 3860mAh/g. The theoretical discharge voltage of lithium-sulfur batteries is 2.287V, when sulfur and lithium completely react to form lithium sulfide (Li2S). The theoretical discharge mass specific energy of the corresponding 3.7v battery 18650 is 2600Wh/kg.

　　The charging and discharging reactions of sulfur electrodes are complex. As of 2013, there is still no clear understanding of the intermediate products produced during the charging and discharging reactions of sulfur electrodes. The charge and discharge reactions of the lithium negative electrode and the sulfur positive electrode are as shown in Equations (1-1) to Equations (1-4). The discharge process of the sulfur electrode mainly includes two steps, corresponding to two discharge platforms. Formula (1-2) corresponds to the cyclic structure of S8 changing into the chain structure of Sn2- (3≤n≤7) ions, and combines with Li+ to generate 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 changing to S2- and S22- and combining with Li+ to generate 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 the further reduction of polysulfides, and the potential range of 2.05-1.5V corresponds to the reduction of soluble polysulfides to form a solid film of lithium sulfide. , which covers the surface of the conductive carbon matrix. 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 the charging platform near 2.5-2.4V in the charging curve.

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