Wide-Temperature Operational P2-Type Cathode via Protective Coating: Synergistic Air Stability Improvement and Mn...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Surface modification is crucial for enhancing cathode material performance in sodium-ion batteries (SIBs).
• P2-type layered oxides are promising cathode materials for SIBs, but often suffer from poor air stability and Mn dissolution.
• Controlling the interface between the cathode material and electrolyte is key to improving battery longevity.

Purpose of the Study:

• To synthesize Al2O3-coated P2-Na0.67Mn0.95Mg0.05O2 (NMMO@Ax) cathode materials using a facile sol-gel method.
• To investigate the effect of varying Al2O3 coating masses on the structural, electrochemical, and thermal properties of the cathode.
• To evaluate the performance of the optimized NMMO@A1 material in SIBs and full battery configurations.

Main Methods:

• Sol-gel synthesis of P2-Na0.67Mn0.95Mg0.05O2 coated with different masses of Al2O3 (NMMO@Ax).
• Electrochemical characterization including cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy.
• Thermal stability testing and full battery assembly with a hard carbon anode.

Main Results:

• Al2O3 coating effectively improved the air stability of the P2-type cathode by reducing residual alkali and inhibiting Mn dissolution.
• NMMO@A1 (1 wt% Al2O3) exhibited the highest pseudocapacitance contribution and lowest impedance among the series.
• NMMO@A1 delivered an initial specific capacity of 184.9 mAh g-1 at 100 mA g-1, with 85.9% retention after 100 cycles and 67.7% after 1000 cycles at 1A g-1.
• The material showed good cycling stability from -20 to 60 °C.
• A full battery using NMMO@A1 cathode and hard carbon anode achieved a high energy density of 326.5 Wh kg-1.

Conclusions:

• Surface modification with Al2O3 is an effective strategy to enhance the electrochemical performance and stability of P2-Na0.67Mn0.95Mg0.05O2 cathode materials for SIBs.
• The optimized NMMO@A1 material demonstrates potential as a high-performance cathode for practical SIB applications.
• The study highlights the importance of interfacial engineering for developing advanced energy storage solutions.