2019 Engineering Sustainable Development
Visualization of Nickel Sulfide Pulverizing in Hierarchical Carbons; Applied for the Anode of Lithium Ion Battery
Authors
Park, J. H. - Presenter, Korea Advanced Institute of Science & Technology (KAIST)
Lee, J., Korea Advanced Institute of Science & Technology (KAIST)
Metal sulfides have been spotlighted as next-generation anode materials of lithium ion battery due to their high theoretical capacity. In addition, they have better thermal stability and electrical conductivity than metal oxide series while having similar theoretical capacity. Among them, the nickel sulfide (NiS) has high theoretical capacity of 590 mAh g-1. However, when NiS was used for the anode material of lithium ion battery, it was pulverized in a long term operation, and electrochemically isolated eventually. To solve this problem, this work suggested the synthesis of the NiS coated by hierarchical carbon shell. The NiS was mixed with CaCO3 nano-templates and then coated with carbon using a toluene bubbling CVD. As a result, hierarchical structured carbon was synthesized on the surface of inner NiS. The resultant material shows a high capacity of 575 mAh g-1 at 0.1 A g-1 and maintain over 483 mAh g-1 at 200th cycle for the anode material of lithium ion battery. During this long-term cycling, inner NiS was pulverized in the hierarchical carbon, which could contain pulverized pieces until the 100th cycle. However, after 100 cycles, the pulverized NiS was separated into Ni and Li2S, which leads to the formation of polysulfide. This converted polysulfide has high solubility and mobility in the organic electrolyte, and eventually diffused out of the carbon coating. This process was confirmed by the cycle-by-cycle TEM images and observed using additional ex situ SEM and XRD analyses.