NFM Cathodes: Sodium Nickel Iron Manganese Oxide

NFM is the shorthand for the O3-type layered oxide Na[Ni_xFe_yMn_z]O₂, most often the equal-thirds version NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM111). It is the cathode inside most of the layered-oxide sodium-ion cells you can buy today. This page expands the one-line entry on our Sodium Ion Layered Transition Metal Oxides page and looks at what NFM means for the cell, the line and the pack.

What it is

Think of NFM as the sodium cousin of NMC with cobalt swapped out for iron. The structure is the same α-NaFeO₂ type (space group R-3m) used for lithium layered oxides, with sodium sitting in octahedral sites between the transition metal layers. The material was first proposed for sodium-ion cells by Kim et al. at Argonne, who showed it could be charged to 4 V without an irreversible phase change [1][2].

Each metal has a job. Our reading of the literature is that nickel carries most of the capacity, manganese stays in the 4+ state and holds the lattice together, and iron is the cheap filler that adds some capacity but has the least stable redox couple at high states of charge [3]. Change the ratio and you trade capacity, cost and stability, just as with NMC.

Key numbers

Parameter	4.0 V cut-off	4.3 V cut-off	Note
Half-cell capacity (mAh/g)	133	165	NFM424, academic data [2]
Full-cell capacity vs hard carbon (mAh/g)	112	n/a	NFM424 [2]
Average discharge potential (V vs Na/Na⁺)	~3.1	~3.3	[2]
Crystal density (g/cm³)	4.54	4.54	NFM111 listed at 4.51 [2]
Cathode specific energy (Wh/kg CAM)	~412	~545	Our arithmetic, see below

NFM material data. Values from the Voß et al. 2025 review table [2]; the specific energy row is our estimate.

The working for that last row is simple: capacity times average voltage. At 4.0 V, 133 mAh/g × 3.1 V ≈ 412 Wh/kg of cathode active material. At 4.3 V, 165 mAh/g × 3.3 V ≈ 545 Wh/kg. So the conservative voltage limit gives away about a quarter of the material energy. That is the central trade-off with NFM, and it is why every datasheet upper voltage deserves a second look.

Making it: the precursor

Lab papers usually make NFM by solid-state reaction, but at scale the accepted route is the one used for NMC: co-precipitate a mixed Ni-Fe-Mn hydroxide precursor, then calcine it with a sodium source [2]. Iron is what makes this harder than NMC. The ferrous ammonia complex is unstable, so the usual ammonia chelating agent is swapped for oxalic acid in Fe-containing layered oxides [2]. Getting the Ni:Fe:Mn ratio uniform through every particle, and the particle size and shape right, sets the quality of the final cathode, just as precursor control does for NMC. Calcination is also where most of the cathode’s carbon footprint comes from, roughly half of it on a Chinese grid [2].

Why the upper voltage matters

Push NFM much past 4 V and the structure starts to change. Charging to 4.3 V brings in a new monoclinic phase, which points to an upper limit for NFM cells of around 4 V before irreversible damage sets in [3]. In practice, manufacturers have not settled on one number. Sandia and Oviedo tore down two commercial NFM111/hard carbon 18650s from different suppliers with essentially identical electrodes, yet one specified 3.95 V and the other 4.1 V as the upper limit [3].

The same study is a useful reality check on cycle life. Cell-to-cell variation within each batch was comparable to lithium-ion. But cycled at 0.5C/0.5C and 25°C over the full voltage window, both cell types were below 80% capacity by about 350 cycles, roughly a tenth of what the datasheets claimed [3]. Another group has reported NFM/hard carbon cells above 80% for at least 1,500 cycles [3], so the chemistry can do better. Our reading is that the spread comes from cell quality and operating window rather than NFM itself, and that a buyer should run their own cycling before believing a sodium-ion datasheet.

Air, moisture and the electrode line

This is the part that bites in manufacturing. O3 layered oxides react with moisture and CO₂ in air, pulling sodium out of the lattice to form NaOH and Na₂CO₃ on the particle surface [4]. That residual alkali then attacks the PVDF binder in an NMP slurry, crosslinking it until the slurry gels and can no longer be coated [4][5]. In one controlled study on an O3 oxide, around 15% of the C–F bonds in the PVDF were dehydrofluorinated [5].

NFM111 shows the same reactivity towards water and CO₂, with sodium loss and carbonate formation after air exposure [6]. For the line, the consequences are familiar from high-nickel NMC: sealed powder handling, tight humidity control through mixing and coating, and a defined process window for slurry pot life. Surface coatings and dopants are the materials-side fixes; most of the recent NFM papers are about exactly this [7].

Temperature and safety

Commercial NFM/hard carbon cells in standard NaPF₆-carbonate electrolyte cycle poorly at elevated temperature, with particle cracking and transition metal dissolution at the cathode [8]. Electrolyte additives help, which puts the same emphasis on electrolyte formulation that we already see in lithium-ion.

On safety, layered oxides are the sodium-ion cathode class most prone to thermal runaway, ahead of polyanion and Prussian blue cells [2]. Abuse work on commercial NFM cells found that repeated mild overcharge leads to sodium plating on the anode and a loss of safety margin [9]. The “sodium-ion is inherently safe” message does not carry over automatically to NFM: the voltage limit and charge control matter just as much as in an NMC pack. See our Thermal Runaway pages for the general mechanisms.

Who uses it

Commercial cells: the first published teardowns of commercial sodium-ion cells, mostly from China, found O3-NFM cathodes [2]. The Sandia 18650s above are NFM111 [3].
Cathode makers: Ningbo Ronbay, the largest NMC producer, holds several O3-NFM synthesis patents, and BTR advertises O3-NFM [2]. Chinese suppliers have ton-scale layered oxide production [2].
CATL: the Fraunhofer FFB review reads CATL’s patent portfolio and the 175 Wh/kg Naxtra cell as pointing to NFM-related cathodes [2]. This is an inference from patents; we could not find a CATL statement naming the Naxtra cathode.
Not NFM: HiNa’s published layered oxides are mainly Cu-Fe-Mn rather than Ni-Fe-Mn, and Faradion uses Ni-Mn-Mg-Ti [2]. BYD and Zhongna are scaling polyanion cathodes instead [2].

NFM against the other sodium cathodes

Cell chemistry	Wh/kg	Wh/L	CAM footprint (kg CO₂e/kg)
NFM111 / hard carbon	161	344	~15
NFPP / hard carbon	126	262	5.8
Fe-PBA / hard carbon	129	233	9.0
LFP / graphite	177	426	7.6

Modelled large prismatic cells, current hard carbon. Voß et al. 2025 [2]. The NFM111 case uses patent data at a 4.3 V cut-off, so a 4.0 V commercial cell will sit lower.

On those numbers the NFM cell is about 9% below LFP per kilogram and about 19% below per litre (our arithmetic: 160.5/176.6 and 344/426). It is clearly the densest sodium option, and the modelling shows layered oxides are the only sodium cells that could match LFP volumetrically once hard carbon improves [2]. The price is a cathode with roughly twice the carbon footprint of NFPP or LFP, mostly from calcination energy and nickel sulphate [2], plus the cycle life and air-handling issues above. Head to our Polyanionic Compounds and Prussian Blue Analogues pages for the other two families.

What it means for the design

Cell selection: choose NFM where volume matters (passenger cars, two-wheelers, compact starter packs). For stationary storage, where cycle life and cost per cycle dominate, polyanion cells are the stronger case today.
BMS: treat the upper voltage as a life parameter, not just a capacity one. Expect suppliers to differ by 150 mV for the same chemistry, and verify the window yourself. See Sodium-Ion Cell Characteristics for the steeper OCV slope that BMS estimation has to handle.
Testing: run your own cycling at the intended window and temperature before accepting datasheet cycle life.
Manufacturing: plan humidity control for the cathode, as for high-nickel NMC, rather than the more relaxed handling LFP allows. See Sodium Ion Cell Manufacturing Process.

Bottom line: NFM is the sodium-ion cathode to know if you care about energy density, and it is already in commercial cells. It behaves like a cheaper, lower-voltage NMC, with the same sensitivity to upper voltage and moisture. The chemistry is sound; the open question is cell quality, so test before you trust the datasheet.