Research progress on high-rate and long-life lithium-sulfur batteries

[Introduction]

Wang Ruihu, a researcher at the State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, and Yang Zhi, a professor at Wenzhou University, collaborated to combine water vapor etched porous NbS2 and highly conductive iodine-doped graphene (IG) into a ternary mixture. In the sulfur positive electrode system, a sandwich type NbS2@S@IG positive electrode material wrapped by IG was synthesized. In this special sandwich structure, the high polarity and strong affinity of the layered NbS2 promotes the physical interception and chemisorption of polysulfides, synergistically solves the problem of polysulfide dissolution and shuttle effect; high conductivity and porosity of NbS2 The rate increases the interface charge transfer and ion migration, thereby improving the electrochemical kinetics of the redox reaction of the Li-S battery; the sandwich structure surrounded by IG can not only make the sulfur material and the layered NbS2 (or IG) close contact, Moreover, it can withstand large volume fluctuations of the sulfur positive electrode during charging and discharging. The Li-S battery assembled by NbS2@S@IG exhibits excellent cycle stability at a high rate of 20-40C.

[Graphic introduction]

Figure 1 Schematic diagram of the synthesis of NbS2@S@IG composite

The slurry of NbS2 and sulfur powder in CSS is mixed with IG, and then freeze-dried, and the molten diffusion of sulfur produces NbS2@S@IG, in which NbS2@S is completely surrounded by IG.

Figure 2 Schematic diagram of the rational mechanism for embedding sulfur in the NbS2 interlayer

During the discharge process, sulfur is gradually converted into soluble Li2S8 species due to the strong interfacial interaction between NbS2 and Li2S8, and then they are adsorbed on the edge positions and surfaces of the conductive NbS2 nanosheets.

【research content】

With the urgent demand for high-capacity energy storage devices in emerging electronic products such as portable electronic devices and electric vehicles , lithium-sulfur batteries (Li-S) have advantages such as high theoretical specific capacity and energy density, low sulfur cost and environmental friendliness. One of the most promising high-capacity storage systems. However, there are still some technical challenges in the commercial application of Li-S batteries, such as the insulation of solid sulfides, the shuttle effect of soluble long-chain polysulfides, and the large volume change of sulfur during charge and discharge. These problems often result in low sulfur utilization, poor cycle life, and even a range of safety issues. How to greatly improve the stability of Li-S battery and increase its high-power discharge performance has become one of the hotspots of current research.

Wang Ruihu, a researcher at the State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, and Yang Zhi, a professor at Wenzhou University, collaborated to combine water vapor etched porous NbS2 and highly conductive iodine-doped graphene (IG) into a ternary mixture. In the sulfur positive electrode system, a sandwich type NbS2@S@IG positive electrode material wrapped by IG was synthesized. In this special sandwich structure, the high polarity and strong affinity of the layered NbS2 promotes the physical interception and chemisorption of polysulfides, synergistically solves the problem of polysulfide dissolution and shuttle effect; high conductivity and porosity of NbS2 The rate increases the interface charge transfer and ion migration, thereby improving the electrochemical kinetics of the redox reaction of the Li-S battery; the sandwich structure surrounded by IG can not only make the sulfur material and the layered NbS2 (or IG) close contact, Moreover, it can withstand large volume fluctuations of the sulfur positive electrode during charging and discharging. The Li-S battery assembled by NbS2@S@IG exhibits excellent cycle stability at a high rate of 20-40C.

The research results were published on the ACS Nano, and the research work was funded by the National Natural Science Foundation of China and the Strategic Science and Technology Special Project of the Chinese Academy of Sciences.