Layered Molybdenum (Oxy) Pyrophosphate (MoO₂)₂P₂O₇ as a Cathode Material for Sodium‐Ion Batteries

Abstract

Layer‐structured (MoO2)2P2O7 was prepared through the decomposition of MoO2HPO4 and further used as a cathode material for sodium‐ion batteries. Results reveal that the capacity and cycling stability of the (MoO2)2P2O7/Na battery largely depends on the lower cutoff voltage. When cycling between 4.0 ‐1.5 V, (MoO2)2P2O7 delivers a capacity of 180 mAh g−1 in the first cycle, but it drops very fast owing to a phase decomposition of the crystal structure to an amorphous one. The cycling stability is still not good when cycling between 4.0 ‐1.7 V. However, when cycling between 4.0 ‐ 2.0 V, the performance can be significantly improved, which delivers 93 mAh g−1 in the first cycle and, after 50 cycles, the capacity can maintain 55 mAh g−1. This is mainly attributed to the stable crystal structure of the Na‐intercalated (MoO2)2P2O7 electrode. Ex situ X‐ray diffraction examination demonstrates that the volume change of the (MoO2)2P2O7 electrode during the first charging process is only 1 %.

Triclinic Off-Stoichiometric Na3.12Mn2.44(P2O7)2/C Cathode Materials for High-Energy/Power Sodium-Ion Batteries

“…The apparent diffusion coefficient of sodium ion during different sodiation/desodiation states was finally evaluated by CV (Figure c). The Randles Sevchik equation for semi-infinite diffusion of Na + into the NMP/C cathode was used for calculation. , where n represents the number of electrons transferred per species reaction, A represents the surface area of the electrode (0.785 cm –2 ), C 0 represents the concentration of sodium ions (0.0086 mol cm –3 ), D represents the apparent sodium-ion diffusion coefficient, v represents the scanning rate, and I p represents the peak current intensity. For an obvious distinction, the anodic peaks are labeled as a, b, and c, whereas the cathodic peaks as a′, b′, and c′.…”

“…The Randles Sevchik equation for semi-infinite diffusion of Na + into the NMP/C cathode was used for calculation. 53…”

“…The apparent diffusion coefficient of sodium ion during different sodiation/ desodiation states was finally evaluated by CV (Figure7c). The Randles Sevchik equation for semi-infinite diffusion of Na + into the NMP/C cathode was used for calculation 53,54. = × I n AC D v 2.69 10 p…”

A Review on Nano-/Microstructured Materials Constructed by Electrochemical Technologies for Supercapacitors

“…Molybdenophosphate (A-Mo-O-P, A = Na, K, etc.) materials are a family of polyanionic phosphate compounds with open frameworks, which have recently aroused great interest in rechargeable batteries [305][306][307][308] 32f, g). Meanwhile, the content of O vacancy increased, as indicated by the enhanced intensity in the electron spin resonance (EPR) spectra (Fig.…”

Layered Molybdenum (Meta)phosphate for Photoreduction of Hexavalent Chromium and Degradation of Methylene Blue under Sunlight Radiance

“… 31 A chitosan-zirconium phosphate nanomaterial has been reported for chromium and dye remediation. 32 Molybdenum polyphosphates such as (MoO 2 ) 2 P 2 O 7 29 and (MoO 2 ) 2 P 2 O 7 33 have recently been studied for battery applications in the literature. Chiweshe et al reported the molybdenum (meta)phosphate phase 34 using a fusion method.…”