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.

LiMn_xFe_1−yPO₄
15 to 20% higher energy density than LFP
- Approximately 0.5V increase over LFP and hence energy increase
Maximum theoretical cell level gravimetric energy density ~230Wh/kg
Maximum cell volumetric energy density ~580Wh/litre [3]
manganese is not a rare metal, global manganese ore resources are very rich
Cell voltages with Graphite Anode
- 4.2V 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 LiMnyFe_1−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 (LiMnyFe_1−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 LiMnyFe_1-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 vs LFP

We are very lucky to have the specifications of two battery cells made by the same company and one being LMFP and the other LFP. Thus an opportunity to look at LMFP vs LFP in a like for like scenario. Both cells are from K-Tech New Energy Company Co Ltd (part of Greenway Battery).

At the moment the LFP chemistry wins this overall, but the LMFP offers some advantages that just might be critical for certain applications.

LMFP batteries can reach a gravimetric energy density of 230 to 240 Wh/kg and a volumetric density of ~580Wh/litre [3]. A significant improvement over LFP.

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

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

Future

Anodeless LMFP

Researchers at WMG, University of Warwick led by Prof. Louis Piper and Dr. Gerard Bree have tested a new battery chemistry in which the anodefree cell configuration (no anode host material like graphite) is coupled with an LMFP cathode (no cobalt, cost effective, secure supply chain) to create a high energy density, low-cost battery system.