Direct Evidence for Lip Lip Interactions in Multi-Walled Carbon Nanotubes

The stability of open edged multi-walled carbon nanotubes has been investigated by using in situ high resolution transmission electron microscopy at elevated temperatures.Formation of inter-shell structures was experimentally observed for the first time and attributed to a robust interaction between adjacent concentric shells(so-called lip lip interaction).The fl uctuating behavior of the inter-shell structures suggests a mechanism by which the carbon atoms can pass in or out through the inter-shell edges during carbon nanotube growth or shrinkage processes.

Cation-mixing stabilized layered oxide cathodes for sodium-ion batteries

Sodium-ion batteries are promising for large-scale energy storage due to sodium's low cost and infinite abundance. The most popular cathodes for sodium-ion batteries, i.e., the layered sodium-containing oxides, usually exhibit reversible host rearrangement between P-type and O-type stacking upon charge/discharge. Herein we demonstrate that such host rearrangement is unfavorable and can be suppressed by introducing transition-metal ions into sodium layers. The electrode with stabilized P3-type stacking delivers superior rate capability, high energy efficiency, and excellent cycling performance. Owing to the cation-mixing nature, it performs the lowest lattice strain among all reported cathodes for sodium-ion batteries. Our findings highlight the significance of a stable host for sodium-ion storage and moreover underline the fundamental distinction in material design strategy between lithium-and sodium-ion batteries.