Conversion reaction of vanadium sulfide electrode in the lithium-ion cell: Reversible or not reversible?

Abstract

Recently two-dimensional layered transition metal dichalcogenides (TMDs) have attracted great scientific interest in electrochemical energy storage. As an important family member of TMDs, vanadium disulfide (VS2) is a promising electrode material for lithium-ion cells because of its remarkable electrical conductivity and fast Li + diffusion rate, but its electrochemical reaction mechanism is still poorly understood. Herein, we have prepared an electrode consisting of VS2 nanosheets and systematically investigated its structural and chemical evolution during the electrochemical processes by employing both in situ and ex situ X-ray spectroscopies. The VS2 undergoes intercalation and conversion reactions in sequence during discharge and this process is found to be partially reversible during the subsequent charge. The decreased reversibility of the conversion reaction over extended cycles could be mainly responsible for the capacity fading of the VS2 electrode. In addition, the hybridization strength between S and V shows a strong dependence on the states of charge, as directly proved by the intensity change of the V-S hybridized states and pure V states. We also reveal that the solid electrolyte interphase on the electrode surface is dynamically evolved during cycling, which may be a universal phenomenon for conversion-based electrodes. This study is expected to be beneficial for the further development of high-performance VS2based electrodes.

Strengthening the Interface between Flower‐Like VS4 and Porous Carbon for Improving Its Lithium Storage Performance

“…The cyclic voltammetry (CV) of VS 4 and other three VS 4 −HC composites with a scan rate of 0.1 mv s −1 from 0.01 to 3 V are tested in Figure S6, Supporting Information. In the first cycle of VS 4 (Figure S6a, Supporting Information), the reduction peaks at 1.8, 1.6, and 1.3 V are related to lithiation process ( x Li + + xe ‐ + VS 4 → Li x VS 4 ), and the peak around 0.6 V is owning to the conversion of Li x VS 4 to Li 2 S and elemental V. [ 25,26 ] On the contrary, the two obvious peaks around 1.9 and 2.5 V during the charge process are related to either the delithiation of Li 2 S with the formation of amorphous VS 4 or the conversion reaction of Li 2 S to S. However, the two reduction peaks around 1.6 and 0.7 V disappear during the subsequent cycles, and the intensity of the couple of peaks become weaker indicating the poor cycle performance. [ 28 ] Apart from the initial cycles, the curves of VS 4 −HC‐0.02 (Figure S6b, Supporting Information), VS 4 −HC‐0.04 (Figure S6c, Supporting Information), and VS 4 −HC‐0.08 (Figure S6d, Supporting Information) show two pairs of reversible peaks around 1.3−1.8 V and 1.9−2.5 V, which are related to the lithiation−delithiation process in the amorphous VS 4 .…”

“…[ 24 ] Both the intercalation of lithium ions and the conversion reaction mechanism occur sequentially in the initial discharge process, and the amorphization of VS 4 anode in the initial process influences the storage mechanism in following the cycles. [ 25,26 ] In addition, the anionic transformation between S 2 2− and 2S 2− provides extra contribution. Nonetheless, pure VS 4 shows a poor cycle performance and low rate capability since intrinsically low conductivity, the effect of large volume expansion, and dissolution of produced polysulfide.…”

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries

“…i Warburg factor of the batteries with a current density of 3 A g −1 after different cycles 1 3 cycles. The capacities of the final stabilization stage can be attributed to the reversible conversion reaction between Na 2 S and S which was the main reaction mechanism of Na-S batteries [31,51].…”

VS4‐Decorated Carbon Nanotubes for Lithium Storage with Pseudocapacitance Contribution

“…Vanadium sulfides, with attractive S–V–S layer structure and high electric conductivity, have recently been recognized as ideal host materials for Li + storage . To realize the high Li + storage performances of vanadium sulfides, fabricating specific nanostructures and compositing with carbon materials have been adopted.…”

“…[22] Vanadium sulfides, with attractive S-V-S layer structure and high electric conductivity,h ave recently been recognized as ideal host materials for Li + storage. [28][29][30][31][32][33][34][35] To realize the high Li + storagep erformances of vanadium sulfides, fabricating specific nanostructures and compositingw ith carbon materials have been adopted. Ac omputational study by Wang and co-workers predicted that VS 2 monolayer could obtain at heoretical capacity as higha s1 397 mAh g À1 for lithium ion storage,s uggesting the potentiala pplication for pseudocapacitive lithium storage.…”