Sodium iron pyrophosphate-phosphate

Example

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Hard carbon

A disordered, non-graphitisable carbon used as the negative electrode of sodium-ion cells, where graphite barely works, and as a fast-charge additive in lithium-ion. Its open structure accepts ions without the strict layer spacing of graphite.

LFP

A positive electrode material, LiFePO₄, giving cells a nominal voltage around 3.2 V, long cycle life and good thermal stability, but less energy per kilogram than nickel-rich oxides. Its flat voltage curve makes state of charge hard to read from voltage alone.

Sodium nickel-iron-manganese oxide

A layered-oxide sodium-ion positive electrode containing nickel, iron and manganese, usually in the O3 structure. It gives the most energy of the common sodium-ion cathodes, with cells around 3.0–3.1 V nominal, but it is sensitive to moisture and typically lasts fewer cycles than polyanionic NFPP.

Sodium vanadium phosphate

A polyanionic sodium-ion positive electrode, Na₃V₂(PO₄)₃, with a NASICON-type framework of open three-dimensional channels through which sodium moves quickly. Cells reach about 2.9–3.1 V nominal and suit high power and very long cycle life; vanadium makes the material costlier than iron-based NFPP.

Polyanionic cathode

A positive material built from transition metals and polyanion groups such as PO₄³⁻, SO₄²⁻ or P₂O₇⁴⁻. The strongly bonded groups raise the voltage through the inductive effect and hold oxygen tightly, giving long life and safety at some cost in capacity and conductivity. LFP is the lithium example; Na₃V₂(PO₄)₂F₃ and iron-based Na₄Fe₃(PO₄)₂P₂O₇ serve sodium-ion cells.

Sodium-ion battery

A cell built like a lithium-ion cell but shuttling sodium ions, usually between a hard-carbon negative and a layered-oxide (NFM), polyanionic (NFPP, NVP) or Prussian-blue positive. It uses no lithium or cobalt and needs no copper foil, so it can be stored at 0 V, at the cost of lower energy density.

References & further reading

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

1. Promise and reality of post-lithium-ion batteries with high energy densities

   Jang Wook Choi, Doron Aurbach · Nature Reviews Materials · 2016

   Topic background · Post-lithium-ion materials and battery concepts, including practical cell-level limitations; historical 2016 perspective.

2. DOE/EPRI 2013 Electricity Storage Handbook in Collaboration with NRECA

   Sandia National Laboratories · 2013

   Topic background · Storage technologies and grid services. The publisher notes that its historical cost and deployment figures are outdated.