SnSex (x = 1, 2) nanoparticles encapsulated in carbon nanospheres with reversible electrochemical behaviors for lithium-ion half/full cells

Abstract

• SnSe x ⊂ CNSs (x = 1, 2) obtained by different in-situ selenation temperature. • SnSe x ⊂ CNSs show excellent electrochemical performances in half/full cells. • Reversible conversions of SnSe x ⊂ CNSs confirmed by ex-situ XRD. • More intermediate Li 2 Se in SnSe 2 ⊂ CNSs display excellent ion kinetics. • SnSe 2 ⊂ CNSs present batter electrochemical performance than SnSe ⊂ CNSs. Tin selenide materials, including SnSe and SnSe 2 , have larger interlayer spacing, weaker van der Waals forces still suffer undesirable volume changes as lithium-ion battery anodes. Herein, we successfully synthesized hierarchical SnSe x (x = 1, 2) nanoparticles encapsulated in carbon nanospheres (SnSe x ⊂ CNSs) by facile in-situ selenation method at different temperature. Partially diffused SnSe x nanoparticles form halo surrounding the SnSe x core with spare inner void space, coupled with thin carbon layer could enhance ionic transport and buffer volume expansion of SnSe x in Li + insertion/desertion processes. The SnSe ⊂ CNSs and SnSe 2 ⊂ CNSs anodes all deliver high initial coulombic efficiency, superior cycle stability and excellent rate capability. SnSe ⊂ CNSs//LiMn 2 O 4 and SnSe 2 ⊂ CNSs//LiMn 2 O 4 full cells also exhibit outstanding electrochemical properties. Furthermore, ex-situ X-ray diffraction patterns demonstrate the detailed reaction mechanisms and confirm the reversible conversions of SnSe ⊂ CNSs and SnSe 2 ⊂ CNSs. The comparison of dynamic behaviors of them by electrochemical impedance spectroscopy and cyclic voltammetry at different cycles confirm the existence of more intermediate Li 2 Se in SnSe 2 ⊂ CNSs, which could enhance the ion kinetics and improve rate capability. Thus, lower synthesis temperature, lower Li + migration energy barrier, outstanding electrochemical performance, and higher excellent ion kinetics of SnSe 2 ⊂ CNSs suggest that our synthesized SnSe 2 ⊂ CNSs are more suitable as LIB anodes to increase the energy density.