One-pot hydrothermal synthesis of ZnS quantum dots/graphene hybrids as a dual anode for sodium ion and lithium ion batteries

One‐Pot Hydrothermal Synthesis of ZnS Nanospheres Anchored on 3D Conductive MWCNTs Networks as High‐Rate and Cold‐Resistant Anode Materials for Sodium‐Ion Batteries

“…Figure a, 4b, Figure S7a and S7b show the initial three CV curves of the pure ZnS, ZnS/MWCNTs‐B and ZnS/MWCNTs‐A, C electrodes at 100 mA g −1 within the voltage range of 0.01‐3 V, respectively. During the initial cathodic scan of ZnS/MWCNTs‐B, three conspicuous peaks are presented at 0.38, 0.22, and 0.07 V. The peak at 0.38 V corresponds to the decomposition of the electrolyte and the irreversible formation of the solid electrolyte interphase (SEI) film, which results in the low Coulombic efficiency (CE) of the first cycle . Peak at 0.22 V is associated with the conversion reaction of ZnS and Na to form Zn and Na 2 S, and another peak at 0.07 V can be ascribed to further alloy reaction between Zn and Na to form NaZn 13 .…”

“…The weight loss below 300 °C should be attributed to the volatilization of adsorbed water and unstable organic species on the surface . In the temperature range of 300–600 °C, the weight loss in TGA curves can be assigned to the degradation of oxygen‐containing groups . The main weight loss above 600 °C should be resulted from the combustion of MWCNTs and the oxidation reaction of ZnS according to the following reaction [Eqs.…”

“…Figure c exhibits doublet S 2p 1/2 and S 2p 3/2 with binding energies of about 162.1 and 163.1 eV . The characteristic peaks of C1s in Figure d are observed at the binding energy of 284.7, 285.4, 286.4, and 289.1 eV, corresponding to C=C, C−O, C=O and O‐C=O groups, and the abundant oxygen‐containing groups are attribute to the carboxylated MWCNTs …”

“…The impedance curves of the four samples are composed of a depressed semicircle in the high‐frequency region and an inclined line in the low‐frequency region . The diameter of the depressed semicircle denotes the charge transfer impedance ( R ct ) at the electrode/electrolyte interface and the inclined line corresponds to a diffusion impedance called Warburg impedance ( W 1 ) . The electrochemical process is controlled by both charge transfer and Na + diffusion .…”

“…The remarkable decrease of R ct values for all the ZnS/MWCNTs composites is mainly due to the introduction of MWCNTs, which will significantly improve the electron conductivity. Na + diffusion coefficients ( D Na ) are further calculated from the low‐frequency region of the Nyquist plot . As shown in Figure b, the σ value of pure ZnS, ZnS/MWCNTs‐A, B and C are 217.5, 10.8, 4.6, and 9.4.…”