Structural characteristic of vanadium(V) oxide/sulfur composite cathode for magnesium battery applications

Abstract

Magnesium batteries are regarded as promising candidates for energy storage devices owing to their high volumetric capacity. The practical application is hindered, however, by strong electrostatic interactions between Mg 2+ and the host lattice and due to the formation of a passivation layer between anode and electrolyte. V 2 O 5 is a typical intercalation compound with a layered crystal structure ((0 0 1) interlayer spacing ∼ 11.53 Å), which can act as a good host for the reversible insertion and extraction of multivalent cations. Herein, we have presented an investigation of the effects of S injection on the structure, electrochemical performance and Mg 2+ diffusion in V 2 O 5 cathode materials for Mg-ion batteries. The V 2 O 5 /S composite structure was investigated using X-ray diffraction, field-emission scanning electron microscope and energy dispersive X-ray spectroscopy. The integrated electrode exhibits an improvement in the electrical and electrochemical properties compared to the V 2 O 5 electrode. The as-prepared V 2 O 5 /S composite has an initial discharge capacity of 310 mAh·g −1 compared to 160 mAh·g −1 for the V 2 O 5 electrode. The V 2 O 5 /S composite is a promising cathode material for magnesium-ion battery applications.

High‐Voltage Aqueous Mg‐Ion Batteries Enabled by Solvation Structure Reorganization

“…Some new reflections appear at 2.41 V (about 25% of depth of discharge). Upon discharge to 2.15 V (about 50% of depth of discharge), all reflections of V 2 O 5 disappear and the obtained reflections of the formed Mg‐rich Mg x V 2 O 5 ( x ≈0.6) (see Rietveld refinement Figure S8a (Supporting Information), space group Pmn 2 1 , lattice parameters a = 12.503 Å, b = 4.180 Å, and c = 3.526 Å) are in good match with ε‐Mg 0.6 V 2 O 5 from our previous work, [ 2j ] indicating a 2‐phase transition process. With further Mg 2+ intercalation to 1.93 and 1.58 V (about 75% and 100% of depth of discharge), the disappearance of new reflections from Mg x V 2 O 5 ( x ≈0.6) suggests a second 2‐phase transition process to form Mg‐rich Mg x V 2 O 5 ( x ≈1.0) phase (Figure S8b, Supporting Information).…”

“…AC was used as the counter electrode due to its high surface area, which can provide sufficient charge storage via electrical double‐layer capacitance to guarantee full charge balance during Mg intercalation. [ 2h,22 ] Note that the specific capacities in this work were calculated according to the weight of the V 2 O 5 active cathode material. Galvanostatic cycling with potential limitation (GCPL) and cyclic voltammetry (CV) measurements were performed in the potential range of [−1.0, 1.1 V] and [−0.75, 0.75 V] (vs AgCl/Ag, 3 m NaCl) in 0.8 m Mg(TFSI) 2 ‐85%PEG‐15%H 2 O and 0.8m Mg(TFSI) 2 ‐100%H 2 O on a VMP3 potentiostat (BioLogic) at 25 °C, corresponding to [1.58, 3.68 V] and [1.88–3.33 V] versus Mg 2+ /Mg, respectively.…”

“…Practically, in contrast to theoretical predictions, the V 2 O 5 nanoclusters/carbon composites show an initial discharge capacity of 300 mAh g −1 in the voltage range of 0.5–2.8 V versus Mg 2+ /Mg. [ 2i ] Despite this, the cycle stability of this kind of high voltage cathode material has been seriously limited by the low electrochemical stability window (ESW, 1.3–2 V) of aqueous Mg‐ion electrolyte (AME). [ 1b,3 ] The ESW of aqueous electrolytes strongly depends on the salts and solvents, electrolyte‐electrode interphases, and electrolyte additives.…”

“…Aqueous magnesium‐ion batteries (AMIBs) have become very attractive recently due to the low cost, high safety, high conductivity of aqueous electrolytes, and rich resources of Mg. [ 1 ] Generally, the specific energy of AMIBs largely depends on the capacity and working potential of the cathode material. Among numerous cathode materials under investigation, vanadium pentoxide (V 2 O 5 ) has been considered as a promising one owing to its large theoretical capacity (294 mAh g −1 when considering 1 mol of Mg 2+ per mol V 2 O 5 ) and high average working voltage of ≈2.4 V, [ 2 ] which results in a large specific energy (> 600 Wh kg −1 ). Practically, in contrast to theoretical predictions, the V 2 O 5 nanoclusters/carbon composites show an initial discharge capacity of 300 mAh g −1 in the voltage range of 0.5–2.8 V versus Mg 2+ /Mg.…”

V2O5 as a versatile electrode material for postlithium energy storage systems

“…They proved that Mg 2+ intercalation occurs from the (101) plane of V 2 O 5− x . Amorphous V 2 O 5 [94], V 2 O 5 –P 2 O 5 [95], GO/V 2 O 5 [96], and V 2 O 5 /S [97] composites are also prepared to improve the capacity and cycling stability of V 2 O 5 . For instance, V 2 O 5 /S composite displays a much higher capacity (310 mAh g −1 ) than that of pristine V 2 O 5 (160 mAh g −1 ).…”