Anionic Te-Substitution Boosting the Reversible Redox in CuS Nanosheet Cathodes for Magnesium Storage

Abstract

The conversion-type copper chalcogenide cathode materials hold great promise for realizing the competitive advantages of rechargeable magnesium batteries among next-generation energy storage technologies; yet, they suffer from sluggish kinetics and low redox reversibility due to large Coulombic resistance and ionic polarization of Mg 2+ ions. Here we present an anionic Te-substitution strategy to promote the reversible Cu 0 /Cu + redox reaction in Te-substituted CuS 1−x Te x nanosheet cathodes. X-ray absorption fine structure analysis demonstrates that Te dopants occupy the anionic sites of sulfur atoms and result in an improved oxidation state of the Cu species. The kinetically favored CuS 1−x Te x (x = 0.04) nanosheets deliver a specific capacity of 446 mAh g −1 under a 20 mA g −1 current density and a good long-life cycling stability upon 1500 repeated cycles with a capacity decay rate of 0.0345% per cycle at 1 A g −1 . Furthermore, the CuS 1−x Te x (x = 0.04) nanosheets can also exhibit an enhanced rate capability with a reversible specific capacity of 100 mAh g −1 even under a high current density of 1 A g −1 . All the obtained electrochemical characteristics of CuS 1−x Te x nanosheets significantly exceed those of pristine CuS nanosheets, which can contribute to the improved redox reversibility and favorable kinetics of CuS 1−x Te x nanosheets. Therefore, anionic Te-substitution demonstrates a route for purposeful cathode chemistry regulation in rechargeable magnesium batteries.

Ammonium-Modified Synthesis of Vanadium Sulfide Nanosheet Assemblies toward High Sodium Storage

“…The CV response current (i) can comply with the power-law formula where α and b are variable parameters. The calculated b value could be used to estimate the electrochemical behaviors. − Figure b shows a linear relationship between log­(scan rate) and log­(peak current). The b values of the five marked redox peaks could be calculated to be 1.16, 0.86, 1.24, 1.20, and 0.58, indicative of a pseudocapacitive-controlled electrochemical reaction kinetics process .…”

Synchrotron Radiation Spectroscopic Studies of Mg2+ Storage Mechanisms in High‐Performance Rechargeable Magnesium Batteries with Co‐Doped FeS2 Cathodes

“…Overall, the electrochemical performance of Co‐doped FeS 2 cathodes for RMBs is comparable with other RMBs reported before (Figure 4o and Table S3, Supporting Information). [ 5a,9c,21,22d,25,27,39 ] In addition, in this study, inexpensive PMC electrolyte and Co‐doped FeS 2 cathodes are applied for high‐performance RMBs, showing great potential of applying such RMBs in energy storage fields.…”

“…[ 8a,11b,39h ] The Cu 2p spectra (Figure S25b, Supporting Information) show obvious changes during cycling, where Cu 0 is found in the fully discharged state (state IV) and Cu + is detected in fully charged state (state I, VI). [ 10,22a,25 ]…”

“…[ 21 ] In type II systems, Mg does not react with M, e.g., 3d transition metals. [ 9c,22 ] Even though S has a high theoretical specific capacity of 1675 mAh g –1 , Table S1 (Supporting Information) shows that M in MS x materials reduces generally specific capacities compared with pure sulfur. In theory, VS 4 (S content = 71.6 wt%) has a high theoretical specific capacity based on the assumed conversion of V 0 ‐S 4 0 to V 0 ‐4MgS.…”

“…finds that FeS 2 cathodes show extremely poor electrochemical performance and capacities are contributed by Mg 2+ insertion/extraction. [ 22c ]…”