PNNL

Abstract

2D layer structured material is often high-capacity ionic storage material with fast ionic transport within the layers. This appears to be the case for non-conversion layer structure, such as graphite. However, this is not the case for conversion-type layered structure such as transition metal sulfide, in which localized congestion of ionic species adjacent to the surface will induce localized conversion, leading to the blocking of the fast diffusion channels and fast capacity fading, which therefore constitutes one of the critical barriers for the application of transition metal sulfide layered structure. In this work, we report the tackling of this critical barrier through nanoscale engineering. We discover that vertically-stacked 2D-MoS2 can dramatically enhance the cycling stability. Atomic level in-situ TEM observation reveals that the MoS2 nanocakes assembled with tangling (100)-terminated nanosheets offer abundant open channels for Li+ insertion through the (100) surface, featuring an enhanced cyclability performance for over 200 cycle with a capacity retention of 90%. In contrast, (001)-terminated MoS2 nanoflowers only retains 10% of original capacity after 50 cycles. The present work demonstrates a general principle and opens a new route of crystallographic design to enhance electrochemical performance for assembling 2D materials for energy storage.