Do you know lithium-sulfur batteries?

Development history of lithium-sulfur batteries: Lithium batteries have a history of more than 30 years, and lithium-sulfur batteries are younger. In 1962, Herbet and Ulam first proposed the use of sulfur as the cathode material and alkaline perchlorate as the electrolyte. The early lithium-sulfur system was studied as a primary battery, and it was even once commercialized, but it was later replaced by a rechargeable battery. In 2009, LindaF.Nazar proposed a lithium-sulfur secondary rechargeable battery on NatureMaterials, and used CMK-3 to achieve a high specific capacity of 1320mAh/g. Since then, lithium-sulfur batteries have truly opened a chapter in development. The principle of lithium-sulfur battery: the positive electrode of the lithium-sulfur battery is sulfur or sulfur-containing materials, and the negative electrode is lithium. The uniform voltage is 2.1V. In theory, the lithium-sulfur system (Li-S) has a specific capacity of 1672mAh/g and an energy density of 2600Wh/kg. It is a traditional commercial lithium battery with LiCo02 as the positive electrode (theoretical specific capacity 273.8mAh/g, Energy density 360Wh/kg) is about 7 times. Compared with general lithium batteries, the nature of lithium-sulfur battery discharge is not simply lithium ion deintercalation, but a redox process accompanied by a large number of intermediate products. During the discharge process of lithium-sulfur discharge batteries, elemental sulfur reacts with Li from ring-opening S8, and the conversion from long-chain Li2S8 to short-chain Li2S is accompanied by two distinct discharge platforms, the high-potential discharge platform is 2.45V-2.1 V, the process can be considered that a large amount of S8 is converted to S42-, and the low-potential discharge is 2.1V1.7V. This process is a large amount of S42- converted into S22- and S2-. On the other hand, different conversion degrees also correspond to different capacitances. The discharge reaction equation is as follows: positive electrode: S8+16Li+e-→8Li2S negative electrode: Li→Li++e-total reaction: 2Li+nS→Li2Sn→Li2S General lithium battery is single-electron deintercalation, lithium-sulfur battery is 8-electron oxidation Reduction, thus having 7-8 times the theoretical capacity and energy density. Similar to traditional lithium batteries, lithium-sulfur batteries are composed of a positive electrode, a negative electrode, a separator, an electrolyte and a separator. Therefore, lithium-sulfur batteries are considered to be the most promising alternative to traditional lithium batteries and become a new energy source for a new generation of energy storage equipment. Sulfur cathode materials are a key factor restricting the development and application of lithium-sulfur batteries, so we focus on sulfur cathodes. At present, the sulfur cathode of the lithium-sulfur system also has several problems to be dealt with: the shuttle effect, poor conductivity, and volume expansion. 1. Polysulfides dissolve during the discharge process (Li2Sx, 3＜x＜8), a complex disproportionation reaction occurs, a shuttle effect occurs, resulting in a large amount of self-discharge, coulombic efficiency and cycle performance decrease, and irreversible capacity attenuation occurs; 2. Elemental sulfur The electrical conductivity of lithium sulfide and the discharge product is low, S electrical conductivity (5×10-30S/cm, 25℃), Li2S/Li2S2 electrical conductivity (~10-30S/cm), resulting in a sulfur utilization rate of only 50-70% about. 3. And from orthorhombic crystal system α-S (ρ1u003d2.03g/cm3) to Li2S with inverse fluorite structure (ρ2u003d1.66g/cm3), the volume expansion is large, the electrode structure is destroyed, and the cycle stability statement is affected. ：Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete the previous article: What should I pay attention to if the lead-acid battery of a motor vehicle can be changed to a lithium battery?