Carbon-Based Composites with Mixed Phosphate-Pyrophosphates with Improved Electrochemical Performance at Elevated...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium iron phosphate-pyrophosphate (Na4Fe3(PO4)2P2O7, NFPP) is a promising cathode material for sodium-ion batteries.
• Its electrochemical performance is significantly limited by low electronic conductivity, necessitating optimized synthesis methods.

Purpose of the Study:

• To develop a simple and unified method for synthesizing NFPP composites with reduced graphene oxide (rGO) and carbon black (C).
• To evaluate the performance of these composites as electrode materials in both sodium-ion and lithium-ion batteries at elevated temperatures.

Main Methods:

• Synthesis of NFPP/rGO and NFPP/C composites.
• Electrochemical performance evaluation in sodium and lithium half-cells at 20 °C and 40 °C.
• Characterization using ex situ X-ray diffraction (XRD) and microscopic studies.

Main Results:

• NFPP/rGO composites exhibited superior electrochemical performance compared to NFPP/C in both Na and Li cells.
• In sodium half-cells, NFPP/rGO achieved a reversible capacity of 95 mAh/g at 20 °C and 115 mAh/g at 40 °C with high cycling stability.
• While NFPP/rGO showed good capacity in lithium cells, cycling stability decreased at 40 °C.

Conclusions:

• The hybrid energy storage mechanism in NFPP/rGO contributes to its enhanced performance.
• NFPP/rGO demonstrates excellent sodium storage capability at elevated temperatures, marking a significant step towards commercialization.