Lithium sulfur batteries have advantages such as high theoretical energy density, low cost, and environmental friendliness. Their theoretical specific capacity and energy density are 1675mA h g-1 and 2600 mA h g-1, respectively, far superior to existing lithium-ion batteries. They have broad application prospects in emerging technologies such as new energy power batteries. However, the conductivity of its positive electrode active material is low; The polysulfides generated during the charging and discharging process are easily soluble in the electrolyte solution, causing a "shuttle effect"; The volume expansion contraction phenomenon that occurs during the insertion and removal of lithium leads to problems such as low utilization of active sulfur substances and short cycle life, which limits the further development of existing lithium sulfur battery technology and applications.

　　In recent years, researchers have attempted to design various novel nanostructured sulfur cathode materials to improve their battery performance. Among them, graphene, due to its unique two-dimensional structure, has high specific surface area, excellent conductivity, and stable structure, which has great potential to be used as a conductive substrate in lithium sulfur battery systems.

　　Zhang Yuegang's team from the International Laboratory of Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences, recently proposed a simple, low-cost and controllable method to prepare high magnification, ultra long cycle life cathode composites. This material encapsulates S nanoparticles in nitrogen doped graphene layers (S @ NG), only mixed with PVDF binder without adding any carbon black material. The assembled battery exhibits extremely high specific capacity under high discharge rate conditions, such as 1167 mA h g-1 at 0.2C; 1058 mA h g-1 at 0.5C; 971 mA h g-1 at 1C; At 2C, it is 802 mA h g-1; At 5C, it is 606 mA h g-1. In addition, the battery can achieve an ultra long cycle life of 2000 times, with a capacity degradation rate of only 0.028% per cycle. The relevant results have been published in the journal Nano Letters (DOI: 10.1021/nl5020475).

　　The sulfur content of the positive electrode of the battery can reach up to 60%, and it has excellent Coulombic efficiency (about 97%) during the cycling process. Even after 2000 cycles, its specific capacity can still compare to the best lithium-ion batteries today. After X-ray absorption spectroscopy and first principles simulation analysis, the excellent performance of this material is attributed to the excellent adsorption of N functional groups in nitrogen doped graphene layers on lithium polysulfides. The research results also confirm that lithium sulfur batteries based on S @ NG composite materials have great potential to replace existing lithium-ion batteries in portable electronics, new power energy and other energy storage fields.