Figure 1. Uncoated carbon / sulfur material (b) Perfectly wrapped carbon / sulfur material (prior to battery assembly) (c) Defective carbon / Sulfur material (prior to battery assembly). (D) Carbon / sulfur material in situ.
Figure 2. (a) Flow chart of in situ package (b) Uncoated carbon / sulfur material, (c) Defective carbon / sulfur material in the package and (d) In situ TEM Fig. (E) Long cycle performance diagram of in situ wrapped carbon / sulfur materials in situ.
With the development of society and technology, the human demand for electrochemical energy storage technology is increasing day by day, researchers are looking for the next generation of secondary batteries with higher specific energy.Lithium sulfur battery uses sulfur as cathode active material, based on sulfur Reversible electrochemical reaction with lithium to achieve energy storage and release, the theoretical mass ratio of energy up to 2600 Wh / kg, is currently 3 to 5 times the lithium-ion battery is expected to be used in power batteries, portable electronics, etc. However, the problem of the short cycle life caused by the polysulfide shuttling effect inside will limit its practical application in the future.
Recently, Chen Liping, a researcher at the Suzhou Institute of Nanotechnology and Nanostructure Biology, CAS, made new progress in the research of positive electrode materials for lithium-sulfur batteries. The researchers demonstrated a new strategy that is different from the conventional sulfur cathode material package. Of the coating strategy is to prepare a coating outside of the sulfur cathode material particles, and then the material is prepared as a positive electrode and assembled with the electrolyte and other batteries into a conventional coating strategy there is an insurmountable contradiction: If the material particles in the assembly The battery has been covered with a perfect coating, the electrolyte will be difficult to diffuse into the material, resulting in the internal sulfur can not participate in the charge and discharge process; and if the material is not perfect coating, the charge and discharge process intermediates and more Sulfide will still diffuse out of the cathode material, creating a shuttling effect. In this new work, researchers preformed an imperfect pore-containing pre-coating on carbon / sulfur composite particles (during material preparation Completed), the positive electrode prepared from this material and the electrolyte containing a special additive together into a battery in the electrolyte infiltration of carbon / Meanwhile the particles, the additive will react with the precoated layer, thereby forming a dense outer coating layer in situ particle.
This in-situ coating strategy avoids the drawbacks of conventional methods, not only to achieve the infiltration of electrolyte and materials, but also limits the diffusion of polysulfides.The results show that using this new coating strategy for lithium-sulfur battery Coulomb Efficiency and cycle life are significantly improved.The assembled batteries exhibit excellent cycling stability at high discharge rates, cycling 1000 cycles at a current density of 1 C, with a capacity decay rate of only 0.03% per cycle. Relevant results have been published in Nature Communications (8,479,2017).
This work has been supported by the Chinese Academy of Sciences strategic pilot science and technology projects, the Ministry of Science and Technology key research and development programs, the National Natural Science Foundation of China.
