# LiFePO₄: the olivine cathode

> Lithium iron phosphate is cheap, non-toxic and very stable: iron and phosphate build a rigid olivine framework, and lithium sits in one-dimensional channels running through it. Lithium leaves at about 3.5 V by turning LiFePO₄ into FePO₄, two phases sharing one framework, which gives the famously flat voltage. Making the particles small and coating them with carbon was what unlocked nearly all of the 170 mAh g⁻¹.

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- Updated: 2026-10-14
- Category: Battery materials
- Method: Olivine cathode
- Starting materials: Iron(II), lithium and phosphate sources, mixed homogeneously and sintered at a moderate temperature
- Product: Olivine LiFePO₄ (Pnma): FeO₆ octahedra and PO₄ tetrahedra with Li in channels along b
- Key result: Pattern computed from the refined structure: strongest line (311) near 35.6°, then (111) near 25.6° and (211)/(020) near 29.7° (Cu Kα)
- Figure: 1920 × 1080 px, 57 editable layers (4 generated objects with settings)

## Steps

1. **Structure**: Pnma, a = 10.33, b = 6.01, c = 4.69 Å: corner-sharing FeO₆ octahedra linked by PO₄ tetrahedra
2. **1D channels**: Lithium sites form chains along b, the only easy direction
3. **Two phases**: LiFePO₄ → FePO₄ (heterosite) + Li⁺ + e⁻ at 3.5 V; the framework is kept (Padhi et al. 1997)
4. **Small and coated**: Moderate sintering and a homogeneous precursor gave > 95 % of 170 mAh g⁻¹ (Yamada et al. 2001); carbon composites approach it at high rates (Huang, Yin & Nazar 2001)

## Strengths

- Iron and phosphate: cheap, non-toxic, abundant
- Very stable framework: safe and long-lived
- Flat voltage

## Limitations

- Low electronic conductivity: needs small particles and carbon
- Lower voltage and density than layered oxides

## Uses

- Electric buses and cars
- Stationary storage
- Power tools

## References

1. Padhi, Nanjundaswamy & Goodenough, “Phospho-olivines as Positive-Electrode Materials for Rechargeable Lithium Batteries”, J. Electrochem. Soc. 1997. https://doi.org/10.1149/1.1837571 (primary)
2. Yamada, Chung & Hinokuma, “Optimized LiFePO4 for Lithium Battery Cathodes”, J. Electrochem. Soc. 2001. https://doi.org/10.1149/1.1348257 (primary)
3. Huang, Yin & Nazar, “Approaching Theoretical Capacity of LiFePO4 at Room Temperature at High Rates”, Electrochem. Solid-State Lett. 2001. https://doi.org/10.1149/1.1396695 (primary)
4. Whittingham, “Lithium Batteries and Cathode Materials”, Chem. Rev. 2004. https://doi.org/10.1021/cr020731c (review)

Credit: After Padhi et al., J. Electrochem. Soc. 1997 (doi:10.1149/1.1837571) and Yamada et al., J. Electrochem. Soc. 2001 (doi:10.1149/1.1348257). Structure from refined positions; pattern computed; voltage curve schematic.

## Questions

**What does the “LiFePO₄: the olivine cathode” template show?** Lithium iron phosphate is cheap, non-toxic and very stable: iron and phosphate build a rigid olivine framework, and lithium sits in one-dimensional channels running through it. Lithium leaves at about 3.5 V by turning LiFePO₄ into FePO₄, two phases sharing one framework, which gives the famously flat voltage. Making the particles small and coating them with carbon was what unlocked nearly all of the 170 mAh g⁻¹.

**What are the steps shown in “LiFePO₄: the olivine cathode”?** 1. Structure: Pnma, a = 10.33, b = 6.01, c = 4.69 Å: corner-sharing FeO₆ octahedra linked by PO₄ tetrahedra. 2. 1D channels: Lithium sites form chains along b, the only easy direction. 3. Two phases: LiFePO₄ → FePO₄ (heterosite) + Li⁺ + e⁻ at 3.5 V; the framework is kept (Padhi et al. 1997). 4. Small and coated: Moderate sintering and a homogeneous precursor gave > 95 % of 170 mAh g⁻¹ (Yamada et al. 2001); carbon composites approach it at high rates (Huang, Yin & Nazar 2001).

**What are the starting materials and the product?** Starting materials: Iron(II), lithium and phosphate sources, mixed homogeneously and sintered at a moderate temperature. Product: Olivine LiFePO₄ (Pnma): FeO₆ octahedra and PO₄ tetrahedra with Li in channels along b.

**Which papers is “LiFePO₄: the olivine cathode” based on?** Padhi, Nanjundaswamy & Goodenough, “Phospho-olivines as Positive-Electrode Materials for Rechargeable Lithium Batteries”, J. Electrochem. Soc. 1997 (doi:10.1149/1.1837571); Yamada, Chung & Hinokuma, “Optimized LiFePO4 for Lithium Battery Cathodes”, J. Electrochem. Soc. 2001 (doi:10.1149/1.1348257); Huang, Yin & Nazar, “Approaching Theoretical Capacity of LiFePO4 at Room Temperature at High Rates”, Electrochem. Solid-State Lett. 2001 (doi:10.1149/1.1396695); Whittingham, “Lithium Batteries and Cathode Materials”, Chem. Rev. 2004 (doi:10.1021/cr020731c).

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