National Base for International Science & Technology Cooperation, National Local Joint Engineering Laboratory for Key Materials of New Energy Storage Battery, Hunan Province Key Laboratory of Electrochemical Energy Storage & Conversion, School of Chemistry , Xiangtan University , Xiangtan 411105 , China.
ACS Appl Mater Interfaces. 2018 Apr 25;10(16):13562-13572. doi: 10.1021/acsami.8b02029. Epub 2018 Apr 11.
A high sulfur loading cathode is the most crucial component for lithium-sulfur batteries (LSBs) to obtain considerable energy density for commercialization applications. The major challenges associated with high sulfur loading electrodes are poor material utilization caused via the nonconductivity of the charged product (S) and the discharged product (LiS), poor stability arisen from dissolution of lithium polysulfides (LiPSs) into most organic electrolytes and pulverization, and structural damage of the electrode caused by large volumetric expansion. A multifunctional synergistic composite enables ultrahigh sulfur content for advanced LSBs, which comprises the sulfur particle encapsulated with an ion-selective polymer with conductive carbon nanotubes and dispersed around Magnéli phase TiO (MS-3) by the bottom-up method. The ion-selective polymer provides a physical shield and electrostatic repulsion against the shuttling of polysulfides with negative charge, whereas it can permit the transmission of lithium ion (Li) through the polymer membrane, and the carbon nanotubes twined around the sulfur promote electronic conductivity and sulfur utilization as well as strong chemical adsorption of LiPSs by means of TiO. Because of this hierarchical construction, the cathode possesses a lofty final sulfur loading of 72% and large sulfur areal mass loading of 3.56 mg cm, which displays the large areal specific capacity of 4.22 mA h cm. In the same time, it can provide excellent cyclic performance with the corresponding capacity attenuation ratio of 0.08% per cycle at 0.5 C after 300 cycles. Especially, while sulfur areal mass loading is sharply enhanced to 5.11 mg cm, the MS-3 composite exhibits a large initial areal capacity of 5.04 mA h cm and still keeps a high reversible capacity of 696 mA h g at 300th cycle even at a 1.0 C. The design of high sulfur content cathodes is a viable approach for boosting practical commercialized application of LSBs.
高硫载量的阴极是锂硫电池（LSB）获得高能量密度商业化应用的最关键组件。高硫载量电极所面临的主要挑战包括：充电产物（S）和放电产物（LiS）的导电性差导致的材料利用率低；多硫化物（LiPSs）溶解在大多数有机电解质中而导致的稳定性差，以及电极的粉碎和结构破坏；体积膨胀大。多功能协同复合材料能够为先进的 LSB 提供超高硫含量，其包含用离子选择性聚合物封装的硫颗粒，以及通过自下而上的方法分散在 Magnéli 相 TiO（MS-3）周围的导电碳纳米管。离子选择性聚合物提供了物理屏蔽和静电排斥，防止带负电荷的多硫化物穿梭，同时它可以允许锂离子（Li）通过聚合物膜传输，而缠绕在硫周围的碳纳米管促进了电子导电性和硫的利用率，以及 LiPSs 通过 TiO 的强化学吸附。由于这种分层结构，阴极具有 72%的高最终硫载量和 3.56mg cm 的大硫面质量负载，显示出 4.22mA h cm 的大面比容量。同时，在 300 次循环后，在 0.5C 时，其相应的容量衰减率为 0.08%/循环，具有出色的循环性能。特别是，当硫面质量负载急剧增加到 5.11mg cm 时，MS-3 复合材料在 5.04mA h cm 时表现出大的初始面容量，甚至在 1.0C 时，在 300 次循环后仍保持高的可逆容量 696 mA h g。高硫含量阴极的设计是提高锂硫电池实际商业化应用的可行方法。
