Copper Doping of CoSe₂ Nanoparticles Encapsulated into Carbon Nanotubes with Enhanced Electron Conductance as Cathode for Rechargeable Magnesium Batteries

Abstract

Rechargeable magnesium batteries (RMBs) have been considered a promising alternative to lithium‐ion batteries (LIBs) due to the high energy density and abundance of magnesium resources. However, the development of high‐performance cathode materials for magnesium batteries has been a significant challenge. Herein, through comprehensive and simple hydrothermal, selenization and impregnation methods, Cu‐doped CoSe2 nanoparticles encapsulated into carbon nanotubes (Cu‐CoSe2@NC) was fabricated. CoSe2 nanoparticles confined in carbon nanotubes (CNTs) growing in three dimensions on the surface of nanofibers have abundant active sites and high doping degree. Cu doping further improves the electron conductance of the Cu‐CoSe2@NC for RMBs. As cathode, Cu‐CoSe2@NC delivers a reversible capacity of 294 mAh g−1 at 20 mA g−1 and 104 mAg g−1 at 500 mA g−1, which exhibits a reasonable specific capacity and rate capability. The characterization of the Cu‐CoSe2@NC by ex‐situ transmission electron microscopy (TEM) after cycles shows that it can be well adapted to the (de)intercalation of magnesium ions. Density Functional Theory (DFT) calculation shows that CoSe2 band gap decreases obviously after Cu doping, favoring the electron and ion transport. This work provides a reference for the design of cathode materials based on transition metal selenide for RMBs.

Enhancing the Lithium Storage Performance of the Nb2O5 Anode via Synergistic Engineering of Phase and Cu Doping

“…In the Nb 3d XPS spectrum of H–Nb 2 O 5 (Figure e), the peaks at 207.29 and 210.03 eV can be assigned to Nb 3d 5/2 and Nb 3d 3/2 of Nb 5+ , respectively. , After Cu doping, the Nb 3d peaks shift toward lower binding energies, indicating the chemical environment changes induced by the replacement of Nb 5+ by Cu 2+ . , As shown in the Cu 2p XPS spectra (Figures f and S8c), the two sharp peaks located at 931.6 and 951.3 eV can be indexed to Cu 2p 3/2 and Cu 2p 1/2 of Cu 2+ , while the other two peaks at 930.1 and 949.3 eV correspond to Cu 2p 3/2 and Cu 2p 1/2 of Cu + . Especially, the Cu 2+ /Cu + ratio in H–Cu 0.1 –Nb 2 O 5 is close to 3.75/1.00, suggesting that copper is mainly in the form of Cu 2+ . ,,, Figure S9 displays the Cu 2p XPS analysis of T–Cu 0.1 –Nb 2 O 5 . Different from H–Cu 0.1 –Nb 2 O 5 , T–Cu 0.1 –Nb 2 O 5 shows the majority of Cu + , which can be explained by the lower annealing temperature.…”

“…38 Especially, the Cu 2+ /Cu + ratio in H−Cu 0.1 −Nb 2 O 5 is close to 3.75/1.00, suggesting that copper is mainly in the form of Cu 2+ . 39,58,60,61 ), which is in inverse proportion to the square of the line slope of Z' − ω −1/2 . 68 Figure 4b shows the comparison of the slopes obtained by fitting the Z' − ω −1/2 plots, and the H−Cu 0.1 −Nb 2 O 5 electrode displays the smallest slope of 50.42, while H−Nb 2 O 5 shows the largest slope of 92.29, indicating that the Cu doping efficiently enhanced the lithium-ion diffusion coefficient of H−Nb 2 O 5 .…”

Copper–Carbon Nanotube Composites Enabled by Brush Coating for Advanced Conductors

“…Pyrrolic-N refers to N atoms that contribute two p-orbital electrons to the π-system, whereas graphitic-N refers to N atoms that substitute for C atoms in the hexagonal ring . The change in the G – band profile combined with the N-doping from PVP along with the diffusion of Cu atoms from both the underlying substrate and Cu overlayer into the SWCNT matrix should result in enhanced charge carrier density and improved electrical properties. ,,− …”