Conductive porous vanadium nitride/graphene composite as chemical anchor of polysulfides for lithium-sulfur batteries

Abstract

Although the rechargeable lithium–sulfur battery is an advanced energy storage system, its practical implementation has been impeded by many issues, in particular the shuttle effect causing rapid capacity fade and low Coulombic efficiency. Herein, we report a conductive porous vanadium nitride nanoribbon/graphene composite accommodating the catholyte as the cathode of a lithium–sulfur battery. The vanadium nitride/graphene composite provides strong anchoring for polysulfides and fast polysulfide conversion. The anchoring effect of vanadium nitride is confirmed by experimental and theoretical results. Owing to the high conductivity of vanadium nitride, the composite cathode exhibits lower polarization and faster redox reaction kinetics than a reduced graphene oxide cathode, showing good rate and cycling performances. The initial capacity reaches 1,471 mAh g−1 and the capacity after 100 cycles is 1,252 mAh g−1 at 0.2 C, a loss of only 15%, offering a potential for use in high energy lithium–sulfur batteries.

Recent development of metal compound applications in lithium–sulphur batteries

“…38 Not long ago, Li and his co-workers reported a 3D porous vanadium nitride/graphene (VN/G) composite as a chemical bridle for the polysulphides. 154 The anchoring effect of vanadium nitride was confirmed by both experimental and theoretical results as shown in Fig. 8.…”

“…8(a)], indicating the strong adsorption of Li 2 S 6 molecules to polar VN. The First-principles calculations based on DFT demonstrated the binding energy between Li 2 S 6 and VN was 3.75 eV, 154 much higher than that on pyridinic N-doped graphene. And the strong polar-polar interaction between Li 2 S 6 and VN resulted in an obvious deformation of the Li 2 S 6 molecule [ Fig.…”

“…The pioneered works on TiN, VN, and Mo 2 N have shown the improved performances of Li-S batteries by their high conductivity and strong chemical anchor functions, 38,154,155 which opens a new direction of metal nitrides for energy storage.…”

“…However, most metal compounds should still be coupled with conductive polymers or carbon materials to enhance the overall conductivity of the cathode rather than relying on the intrinsic conductivity to attain the best service performances in the Li-S batteries. Thirdly polar metal compounds, which can also serve as the electrocatalyst to facilitate the polysulphides redox reactions and increase the active materials utilization is preferable, of which VN, 154 CoS 2 , 41 and MnO 2 81 have been reported. Finally, the nanostructures of metal compounds, i.e., surface area, pore size, pore volume, as well as particle size are also important factors which influence the performance of Li-S batteries.…”

Macroporous Activated Carbon Derived from Rapeseed Shell for Lithium–Sulfur Batteries

“…Lithium-sulfur (Li-S) batteries are expected to perform a significant role in the field of energy storage owing to its ultrahigh theoretical energy density of 2500 Wh kg −1 , environmental friendliness, and low cost [12][13][14][15][16][17][18][19]. However, in practical applications, Li-S batteries are usually hindered by problems originating from the sulfur cathode, metallic lithium anode, and electrolyte [20][21][22][23].…”