NFM Sodium Cathode Performance Across Voltage Windows | atomfair

By ATOMFAIR LLC | Published July 27, 2026 | Updated August 18, 2026

This NFM dataset answers a practical screening question: how much capacity is gained when the upper voltage limit moves from 4.0 V to 4.2 V, and what happens to first-cycle efficiency at the same time? In sodium-metal 2320 coin cells, the reported capacity spans 123.53-153.26 mAh/g across 2.0-4.0 V, 2.0-4.1 V, and 2.0-4.2 V windows. The chart also includes an 18 mg/cm2 condition, which helps separate a voltage-window effect from a loading effect before any full-cell claim is made.

What This NFM Voltage-Window Result Shows

The data show a clear trade-off rather than a single best number. At 10 mg/cm2, expanding the upper cutoff from 4.0 V to 4.2 V raises the reported capacity from 123.53 mAh/g to 153.26 mAh/g, while first-cycle efficiency moves from 96.00% to 94.71%. That makes the 4.2 V curve useful when accessible capacity is the priority, but it also increases the amount of sodium-inventory and formation behavior that must be checked before electrode pairing.

Test Conditions and Data Source

The following conditions are transcribed from the supplied NFM charge-discharge chart. The four panels are labeled S01-4.0V, S01-4.1V, S01-4.2V, and S04-4.0V. Each panel uses an NFM cathode against sodium metal in a 2320 coin cell with a carbonate-based electrolyte, 0.1C/0.1C cycling, and a test temperature of 25 +/- 1 C.

How Capacity Changes with the Upper Cutoff Voltage

The S01 series isolates the upper cutoff most cleanly because the loading remains 10 mg/cm2. Moving from 4.0 V to 4.1 V adds 5.34 mAh/g, from 123.53 to 128.87 mAh/g, while first-cycle efficiency decreases by 0.44 percentage points. Moving from 4.1 V to 4.2 V adds a much larger 24.39 mAh/g, reaching 153.26 mAh/g, but the first-cycle efficiency decreases another 0.85 percentage points to 94.71%. The extra capacity at 4.2 V is therefore a meaningful screening result, not a free improvement.

For a controlled material comparison, keep the voltage window, loading, current collector, coating side, electrolyte volume, rest time, and formation protocol aligned. The sodium-ion cathode electrode sheets product family makes those electrode-format variables easier to control. A current single-sided NFM111 electrode sheet can support a repeatable electrode-format comparison, while a single-crystal NFM 424 sodium cathode foil represents a different material form that should not be merged into the same result set without separate evidence.

Why the 18 mg/cm2 Result Matters

The S04-4.0V panel adds a second variable: loading rises to 18 mg/cm2 while the voltage window returns to 2.0-4.0 V. Its reported capacity is 127.51 mAh/g with 95.75% first-cycle efficiency, compared with 123.53 mAh/g and 96.00% for S01-4.0V at 10 mg/cm2. The closeness of these values suggests that the 4.0 V response is not only a low-loading artifact in this chart, but a single pair of curves cannot establish high-loading reproducibility or transport behavior.

This is the point where electrode-sheet construction matters. Coating uniformity, drying, compaction, pore access, and electrolyte wetting can change the measured result even when the active material name is unchanged. The dataset is therefore useful for selecting a next electrode condition, not for assuming that every 18 mg/cm2 NFM sheet will reproduce the same capacity.

What This Dataset Supports – and What It Does Not

Supported by the reported chart: a voltage-window comparison for NFM sodium cathode in sodium-metal half cells; a capacity range of 123.53-153.26 mAh/g; a first-cycle efficiency range of 94.71-96.00%; and a direct comparison between 10 mg/cm2 and 18 mg/cm2 at the 2.0-4.0 V window.

Not established by the reported chart: repeat-cell statistics, long-term retention, rate capability beyond 0.1C, impedance growth, electrolyte optimization, electrode density, full-cell N/P balance, or whether the 4.2 V condition remains beneficial after extended cycling. Those questions require a planned test matrix rather than extrapolation from one figure.

Next Validation Steps for Sodium-Ion Full Cells

The next experiment should repeat each voltage window across multiple cells, then add rate capability, extended cycling, impedance tracking, and post-formation capacity measurement. Use battery test equipment and instruments that can hold the same current, cutoff, rest, and recording protocol across the comparison set. The wider Battery Research hub provides the surrounding workflow for moving from material screening to electrode and cell validation.

Once the preferred NFM voltage window is selected, pair it with a measured hard-carbon anode rather than nominal material capacity. The next full-cell design should track cathode areal capacity, first-cycle losses, electrode density, and the intended N/P target. A pouch-cell step can follow after the coin-cell variables are narrowed, but this chart alone does not represent pouch-cell performance.

Data Scope

This article interprets the supplied NFM first-cycle voltage-capacity chart only. It does not add unreported cycle-life, rate, impedance, density, electrolyte composition, or full-cell data. Researchers requiring a comparable NFM electrode condition or raw test context should specify the target voltage window, loading, coating side, current collector, electrolyte, cell format, and validation objective when contacting ATOMFAIR at inquiry@atomfair.com.