CR1620 battery.Progress in research on lithium-sulfur batteries with high volume and weight energy density

　　Lithium-sulfur batteries are regarded as one of the ideal choices for the next generation of high-energy-density battery systems. They have attracted great attention from the scientific research community and industry around the world. They are one of the key research directions for the future layout of various countries. However, as research continues to deepen, lithium-sulfur batteries are also facing increasingly severe challenges. The main problem currently is that the volumetric energy density of lithium-sulfur batteries is low, causing them to lose their competitiveness in many important market applications. At the same time, the high electrolyte dosage has also become a bottleneck in improving their gravimetric energy density. The main reason is that sulfur is an ion and electronic insulator, so the sulfur in the cathode requires a large amount of inactive material to exert its capacity. On the one hand, a large amount of carbon with high specific surface area (usually >30%) needs to be added to ensure good electronic conductivity of the electrode, resulting in electrode porosity usually >70% (commercial lithium-ion battery cathode: <40%), which makes lithium The volumetric energy density of sulfur batteries is greatly reduced. On the other hand, high porosity requires a large amount of electrolyte infiltration and dissolved intermediate products to ensure the ionic conductivity of the electrode (electrolyte active material ratio: lithium-sulfur batteries are usually >3 uL/mg, commercial lithium-ion batteries are usually <0.5 uL/mg ), thus greatly limiting the gravimetric energy density of lithium-sulfur batteries. Therefore, the key technical bottleneck currently restricting the practical application of lithium-sulfur batteries is how to achieve low electrolyte dosage, high electrode density and low inactive material content under high active material loading conditions (10 mg/cm2).

　　Liumin Suo, associate researcher of the E01 group of the Clean Energy Key Laboratory of the Institute of Physics, Chinese Academy of Sciences/Beijing National Research Center for Condensed Matter Physics, collaborated with Professor Ju Li and Dr. Weijiang Xue of the Massachusetts Institute of Technology In view of the common problem existing in current lithium-sulfur batteries - low energy density at the battery device level, it is innovatively proposed to use the embedded electrode material Mo6S8 with high electronic and ionic conductivity to replace the inactive material carbon to form an embedded-conversion hybrid electrode, so that Under the condition of ensuring high active material loading (more than 10 mg/cm2), the carbon content of the sulfur cathode is reduced to less than 10 wt%, the electrolyte active material ratio is greatly reduced to 1.2 μL mg-1, and the electrode porosity is less than 55%. The ampere-hour soft-package full battery using this new hybrid electrode can significantly increase the monomer energy density while ensuring cycle life, and can simultaneously achieve high volumetric energy density (581 Wh/L) and gravimetric energy density (366 Wh/L). kg), providing a new solution and a practical commercialization technology solution for the future development of new high-energy-density lithium-sulfur batteries (Figure 1). The research results were recently published in Nature Energy, 2019, DOI: 10.1038/s41560-019-0351-0. The title of the article is Intercalation-conversion hybrid cathodes enabling Li–S full-cell architectures with jointly superior gravimetric and volumetric energy densities.

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