Fan Haining, Tang Qunli, Chen Xiaohua, Fan Binbin, Chen Shanliang, Hu Aiping
College of Materials Science and Engineering, Hunan University, Hunan Province Key Laboratory for Spray Deposition Technology and Application, Changsha, 410082, P. R. China.
Chem Asian J. 2016 Oct 20;11(20):2911-2917. doi: 10.1002/asia.201600919. Epub 2016 Sep 14.
Lithium-sulfur (Li-S) batteries are attractive owing to their higher energy density and lower cost compared with the universally used lithium-ion batteries (LIBs), but there are some problems that stop their practical use, such as low utilization and rapid capacity-fading of the sulfur cathode, which is mainly caused by the shuttle effect, and the uncontrollable deposition of lithium sulfide species. Herein, we report the design and fabrication of dual-confined sulfur nanoparticles that were encapsulated inside hollow TiO spheres; the encapsulated nanoparticles were prepared by a facile hydrolysis process combined with acid etching, followed by "wrapping" with graphene (G-TiO @S). In this unique composite architecture, the hollow TiO spheres acted as effective sulfur carriers by confining the polysulfides and buffering volume changes during the charge-discharge processes by means of physical force from the hollow spheres and chemical binding between TiO and the polysulfides. Moreover, the graphene-wrapped skin provided an effective 3D conductive network to improve the electronic conductivity of the sulfur cathode and, at the same time, to further suppress the dissolution of the polysulfides. As results, the G-TiO @S hybrids exhibited a high and stable discharge capacity of up to 853.4 mA h g over 200 cycles at 0.5 C (1 C=1675 mA g ) and an excellent rate capability of 675 mA h g at a current rate of 2 C; thus, G-TiO @S holds great promise as a cathode material for Li-S batteries.
锂硫（Li-S）电池因其与普遍使用的锂离子电池（LIBs）相比具有更高的能量密度和更低的成本而备受关注，但存在一些问题阻碍了其实际应用，例如硫阴极的低利用率和快速容量衰减，这主要是由穿梭效应引起的，以及硫化锂物种的不可控沉积。在此，我们报道了一种双限域硫纳米颗粒的设计与制备，该颗粒被封装在空心TiO球内；通过简便的水解过程结合酸蚀刻制备封装的纳米颗粒，随后用石墨烯“包裹”（G-TiO@S）。在这种独特的复合结构中，空心TiO球通过限制多硫化物并借助空心球的物理力和TiO与多硫化物之间的化学结合来缓冲充放电过程中的体积变化，从而作为有效的硫载体。此外，石墨烯包裹层提供了有效的三维导电网络，以提高硫阴极的电子导电性，同时进一步抑制多硫化物的溶解。结果，G-TiO@S复合材料在0.5C（1C = 1675 mA g）下200次循环中表现出高达853.4 mA h g的高稳定放电容量，在2C电流速率下具有675 mA h g的优异倍率性能；因此，G-TiO@S作为Li-S电池的阴极材料具有很大的潜力。
