Structural Reversibility of Nanoscaled Sn Anodes.

Alloying-type anode materials provide high capacity for lithium-ion batteries; however, they suffer pulverization problems resulting from the volume change during cycling. Realizing the cycling reversibility of these anodes is therefore critical for sustaining their electrochemical performance. Here, we investigate the structural reversibility of Sn NPs during cycling at atomic-level resolution utilizing in situ high-resolution TEM. We observed a surprisingly near-perfect structural reversibility after a complete cycle. A three-step phase transition happens during lithiation, accompanied by the generation of a significant number of defects, grain boundaries, and up to 202% volume expansion. In subsequent delithiation, the volume, morphology, and crystallinity of the Sn NPs were restored to their initial state. Theoretical calculations show that compressive stress drives the removal of vacancies generated within the NPs during delithiation, therefore maintaining their intact morphology. This work demonstrates that removing vacancies during cycling can efficiently improve the structural reversibility of high-capacity anode materials.

Preparation and Comprehensive Performance Test of Superhydrophobic Paper Mulch Films.

Paper mulch was treated with nano-zinc oxide and nano-silica dispersion by a brushing method, and its mechanical stability, hydrophobicity, impermeability, and wet strength were verified. The experiment shows that the mulch film after brushing has superhydrophobic properties, and it can also have better superhydrophobic properties and stability after being allowed to stand at room temperature for 240 h and drying under a vacuum of 0.03 MPa under negative pressure. The wet strength test after soaking for different times shows that the mechanical properties of the base paper are reduced more than that of the hydrophobic paper. It is concluded that the hydrophobic coating can improve the wet strength of the paper mulch. The experimental results show that the coating has the erosion durability and mechanical stability of the paper mulch, the wet strength can improve, and the paper mulch has stronger mechanical stability and stronger ability to adapt to complex environments.