Sodium iron phosphate

Sodium iron phosphate Na₄Fe₃(PO₄)2(P₂O₇), also known as sodium ferric phosphate pyrophosphate (NFPP), is a NASICON-type mixed polyanionic cathode active material designed for sodium-ion batteries. It adopts an orthorhombic crystal structure (space group Pn21a) with an open framework featuring large tunnels, facilitating efficient sodium-ion transport essential for high-performance battery applications. NFPP exhibits a relatively flat voltage profile with two small plateaus at approximately 3.2 V and 2.9 V vs. Na/Na⁺, resulting in a nominal voltage around 3.1 V. Its theoretical capacity is approximately 129 mAh g⁻¹, based on the extraction of three Na⁺ ions per formula unit. The material displays exceptional structural stability, with minimal volumetric change of less than 4% during charge-discharge cycles, contributing to its long cycle life and safety. Our NFPP is a black, air-stable powder that simplifies handling and processing. It features a 3 wt% carbon coating, which enhances its electronic conductivity and rate performance. With a typical particle size of 5 μm (D50) and a surface area of approximately 10 m²/g, it is highly suitable for various battery manufacturing applications.

NFPP is an attractive cathode material for sodium-ion batteries, offering a cost-effective and sustainable alternative to lithium-ion systems. Its efficient sodium-ion transport and stable voltage profile enhance battery performance, providing high specific capacities even at fast charging and discharging rates. The nominal operating voltage of around 3.1 V is higher than many other sodium-ion cathode materials, improving the energy density of the battery. The exceptional structural stability of NFPP, with less than 4% volumetric change during operation, ensures excellent cycling stability and safety—key factors for high-energy-demand applications such as energy storage systems, electric vehicles, and power tools. Its air stability simplifies processing and reduces manufacturing complexities and costs.

These attributes make NFPP a promising candidate for next-generation, reliable energy storage solutions, meeting the growing demand for sustainable and efficient battery technologies.