Lithium Manganese Iron Phosphate

Abbreviated as LMFP, Lithium Manganese Iron Phosphate brings a lot of the advantages of LFP and improves on the energy density.

  • LiMnxFe1−yPO4
  • 15 to 20% higher energy density than LFP
    • Approximately 0.5V increase over LFP and hence energy increase
  • Maximum theoretical cell level energy density ~230Wh/kg
  • manganese is not a rare metal, global manganese ore resources are very rich
  • Cell voltages with Graphite Anode
    • 4.25V maximum, 3.75V nominal, 2.5V minimum
  • Electrodes
    • aluminium on the cathode side
    • copper on the anode side

Lithium Manganese Iron Phosphate (LMFP) battery uses a highly stable olivine crystal structure, similar to LFP as a material of cathode and graphite as a material of anode. A general formula of LMFP battery is LiMnyFe1−yPO4 (0⩽y⩽1).

The success of LFP batteries encouraged many battery makers to further develop attractive phosphate alternatives. The olivine-type cathode materials LiMPO4 ( M=Mn,Ni, Co) have attracted much attention. However, these materials have drawbacks that limit their use – the dissolution of substituted metal and decomposition of the electrolyte.

Therefore, attention has focused more on the combination of LFP + manganese = LMFP (LiMnyFe1−yPO4) as a promising cathode material that combines features of the high safety of LiFePO4 and the high energy density of LiMnPO4. The amount of manganese in LiMnyFe1-yPO4 is crucial because a cathode material that contains too much manganese exhibits poor cycling stability. Especially at elevated temperature, which can be attributed to the manganese dissolution.  Although the theoretical capacity of LMFP is the same as LFP, its energy density is roughly 20% higher than that of LFP because higher operating voltage (3.7V vs 3.2V).

LMFP batteries can reach a gravimetric energy density of 200-210 Wh/kg.

Technical difficulties such as low electrical conductivity and mentioned dissolution of manganese during charge and discharge cycles still hinder their practical application. LMFP is not a new battery at all. Chinese battery giants BYD, Gotion, CATL, etc. started their development more than 10 years ago. They announced several terms to launch their mass production, but technical challenges forced them to postpone it. LMFP surpasses NMC in thermal stability and cycle life.

downsides

  • low electronic conductivity
  • LMFP sees a 5 to 10% cost increase over LFP
  • low rate performance
  • dissolution of manganese during charge and discharge
LMFP cell chemistry

Cathode: Production of LMFP cathode material is similar to those of #lfp and it is made by solid-state synthesis, which means mixing and heating of solid precursor lithium carbonate (Li2CO3) as a source of lithium and manganese carbonate (MnCO3) as a source of manganese with sources of iron and phosphorus. The resulting mixture is coated, dried, and calendered – rolled under high pressure to form a uniform layer. After calendering is material cut into pieces of the desired shape a size.
Anode: The anode material is a mixture of graphite, a conductive agent (carbon black), and a binder ((SBR, PVDF, Carboxymethyl cellulose (CMC), Polyacrylic acid (PAA)). The mixture is then formed coated on a copper current collector, dried, calendered, and cut into the desired shape.
Electrolyte: Due to the decomposition of organic electrolytes at high voltages, there were developed special hybrid solid electrolytes, to improve high-temperature cycling.
Separator: Separators are made up of polyolefin material, which is either polypropylene (PP) or polyethylene (PE), or both combined.

Gotion L600 Astroinno

The Gotion L600 Astroinno is an Lithium Manganese Iron Phosphate (LMFP) based cell chemistry.

  • 5% lower cost than a conventional LFP
  • 20-25% less expensive than cells NMC
  • 240Wh/kg and 525Wh/litre

References

  1. LMFP industry special report in 2022, TycoRun Energy
  2. Customcells presents the newest cobalt free cathode active material, CustomCells Newsletter 2018

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