Zero-Dimensional Ordered Sr₂CoMoO_6-δ Double Perovskite as High-Rate Anion Intercalation Pseudocapacitance.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Developing stable electrode materials for redox reactions is crucial for energy storage.
• Double perovskites offer potential for tailored structural and electronic properties.
• B-site cation ordering can enhance structural stability and electrochemical performance.

Purpose of the Study:

• To investigate B-site cation ordering in Sr2CoMoO6-δ (DP-SCM) for improved redox stability.
• To explore the relationship between cation ordering, oxygen mobility, and charge storage mechanisms.
• To evaluate the electrochemical performance of DP-SCM as an electrode material for energy storage devices.

Main Methods:

• Synthesis and characterization of B-site cation-ordered double perovskite Sr2CoMoO6-δ.
• X-ray photoelectron spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR) for oxygen vacancy analysis.
• Electrochemical testing including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
• Fabrication and testing of a symmetric cell using DP-SCM electrodes.

Main Results:

• Achieved a favorable rock salt structure (0D arrangement) through B-site cation ordering in DP-SCM.
• High oxygen vacancy content facilitated a high oxygen anion diffusion rate (2.03 × 10⁻¹¹ cm² s⁻¹).
• Exhibited fast charge storage kinetics (ΔEp ≈ 0.013 V@ 1 mV s⁻¹) with excellent cycle life (125% retention over 5000 cycles).
• Demonstrated a high capacitance of 747 F g⁻¹ at 1 A g⁻¹ with 56% rate capability up to 10 A g⁻¹.
• A symmetric cell achieved an energy density of 64 Wh kg⁻¹ at 855 W kg⁻¹ with a 1.4 V operating potential.

Conclusions:

• B-site cation ordering in DP-SCM enhances structural stability and electrochemical performance.
• High oxygen mobility and fast anion intercalation are key to the superior charge storage mechanism.
• DP-SCM is a promising electrode material for high-performance energy storage applications.
• Understanding cation ordering and charge storage mechanisms can guide the design of advanced capacitive materials.