Search

Abstract Heterostructures have broad potential application in energy conversion material and optoelectronic device since of novel interface effect and enhanced electron transport dynamics at heterointerfaces. Herein, we report a heterostructured SnS/SnO 2 /spherical graphene composite, in which ultrafine SnS/SnO 2 nanoparticles with heterostructures are sandwiched between multi-layers of graphene sheets, exhibiting a hollow spherical architecture as a whole. Detailed electrochemical studies indicate that the molar ratio of SnS to SnO 2 has great influence on the charge transport efficiency. Theoretical calculation reveals that SnS and SnO 2 exhibit different work functions and the Fermi level shift is affected by the SnS/SnO 2 molar ratio, thus the hybrid with the ratio close to 1.0 owns the most adsorbed lithium ions, which leads to the highest specific charge-transfer kinetics and lowest ion-diffusion resistance than other samples. Electrochemical tests show that the composite with appropriate composition delivers the best lithium storage rate performance (620 and 312.7 mAh g−1 at 1 C and 10 C). A much stable and high reversible specific capacity of 850 mAh g−1 is obtained after 200 cycles at 0.1 C. The appropriate molar ratio of nano-heterostructures and the novel sandwich hollow spherical composite structure are attributed to the excellent electrochemical performances. Graphical abstract Image 1 Highlights • Heterostructured SnS/SnO 2 /spherical graphene composite is prepared. • Ultrafine SnS/SnO 2 nanoheterostructures are sandwiched between graphene shells. • Fermi level shift is influenced by SnS/SnO 2 molar ratio via DTF calculation. • The composite with molar ratio close to 1 exhibits best charge transfer capability. • Excellent rate performance and cyclic stability is obtained in optimized sample. [ABSTRACT FROM AUTHOR]

• The influence of halogens incorporation on Li 7 P 3 S 11 glass-ceramic is studied. • 80Li 7 P 3 S 11 •20LiBr shows improved ability to suppress lithium dendrites. • LiBr does not enter the lattice, but rather exists in the lattice gap of Li 7 P 3 S 11. • Br decrease electron cloud density on P and S , reduce Li+ binding and increase ion conductivity. • DFT evaluations prove that LiBr incorporation increases interface energy of SEI to Li. Li 7 P 3 S 11 glass-ceramic is considered as a superionic conductor electrolyte with great application prospect, but its realization is limited due to an unstable interface against lithium metal. Incorporation of lithium halides in electrolyte promotes enhancement in ionic conductivity and helps inhibit lithium dendrite growth. However, the mechanistic impact of halide incorporation is still not been fully explained. In this work, the effects of halogen introduction into Li 7 P 3 S 11 glass-ceramic to the ion conductivity, critical current density and interfacial stability of solid electrolyte interphase (SEI) is studied. It shows that the LiBr-incorporated Li 7 P 3 S 11 obtains the most obviously increased critical current density. Structural characterizations indicate that the LiBr does not enter the lattice, but rather exists in the lattice gap of Li 7 P 3 S 11. However, the highly electronegative Br decreases the electron cloud density on the surface of P 2 S 7 4− and PS 4 3− units, reduces their binding to Li+ and thus increases the ion conductivity. Density functional theory evaluations show that the addition of LiBr can increase the interface energy of SEI to Li, which is beneficial to suppress the growth of lithium dendrite. Therefore, the Li/80Li 7 P 3 S 11 •20LiBr/Li cell presents a double increase of the critical current density (0.968 mA/cm2) and circulates stably at 0.5 mA/cm2 at room temperature. The effects of halogen introduction into Li 7 P 3 S 11 glass-ceramic to the ion conductivity and interfacial stability of SEI is studied. [Display omitted] [ABSTRACT FROM AUTHOR]