Batteries & Energy Storage
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Sodium-Ion Electrolyte Cost Sensitivity
Sodium-Ion Electrolyte
How large is the 300-cycle capacity-retention difference between 1.0 M NaFSI and 1.0 M NaPF6 formulations in matched 1 Ah full cells and coin half cells?
THE QUESTION
Which sodium salt and solvent formulation holds [threshold] capacity retention over [cycles] at a cost per kWh below the Li reference? Verifier: half-cell then full-cell cycling. [baseline: to verify]
WORK ORDER
Retention difference of sodium bis(fluorosulfonyl)imide in matched 1 Ah full cells and half cells
BACKGROUND
What this Apodex Lab is
Sodium-ion batteries offer an alternative to lithium chemistries by drawing on sodium's 2.75 per cent crustal abundance. Yet practical adoption depends on the cost of delivered energy over operating life rather than elemental abundance alone. If changing the electrolyte salt and solvent does not substantially extend full-cell lifespan or reduce total materials mass, formulation efforts divert resources away from electrode manufacturing, formation protocols, and cell assembly.
Current salt and solvent rankings rely heavily on unreplicated half-cell tests against sodium metal foil. A reported capacity retention of 89.90 per cent for sodium bis(fluorosulfonyl)imide in dimethyl carbonate against 55.39 per cent for a comparator, or 200 cycles at 1C with coulombic efficiency above 99 per cent, comes from single-laboratory studies without matched full-cell confirmation. Crucial physical parameters, including first-cycle irreversible loss, gravimetric fill mass per ampere-hour, measured discharge energy in watt-hours, and full-cell fade over 300 cycles, have never been measured together on a single cell design. Without these matched inputs, reported half-cell improvements cannot establish whether electrolyte formulation alters delivered energy economics.
The Sodium-Ion Electrolyte Apodex Lab benchmarks coin half cells against 1 Ah multilayer pouch full cells built from a single coating lot of hard-carbon anodes and layered sodium transition-metal oxide cathodes. Testing compares a 1.0 M sodium bis(fluorosulfonyl)imide formulation against a 1.0 M NaPF6 baseline across 300 cycles at 25 degrees C, tracking discharge energy, precision coulometry over 120 cycles at C/2, and fill mass to 0.01 g. The protocol resolves full-cell retention differences to a 90 per cent interval half-width of ±3.5 percentage points and fade rate differences to ±0.004 per cent per cycle. These measurements determine whether qualification programmes should continue broad electrolyte screening or freeze the formulation and focus on formation optimisation and fill metering.
WHY NOW
Why the field is spending on an assumption
Sodium-ion research relies on single-group coin half-cell tests reporting capacity retentions such as 89.90 per cent for sodium bis(fluorosulfonyl)imide against 55.39 per cent for comparators. The consensus assumes formulation governs cycle life, yet full-cell retention remains unmeasured on matched electrodes. Bottom-up models link material properties to delivered energy, but lack matched inputs from a single cell design: gravimetric fill per ampere-hour, first-cycle irreversible loss, and full-cell fade rate. Test facilities cannot determine whether published half-cell gains transfer into multilayer pouch cells or whether salt selection alters delivered energy.
WHAT WE’D BUY
What we would ask a laboratory to run
We are not buying the answer. We are buying a measurement with an interval — and the bars it will be compared against.
A testing facility builds coin half cells and nominally 1 Ah multilayer pouch full cells from one coating batch of hard-carbon anodes and layered transition-metal oxide cathodes. Cells receive either a 1.0 M sodium bis(fluorosulfonyl)imide electrolyte or a 1.0 M NaPF6 baseline. The facility measures full-cell capacity-retention differences at 300 cycles to a 90 per cent confidence interval of ±3.5 percentage points, fade rates from ultra-high-precision coulometry over 120 cycles to ±0.004 per cent per cycle, and matched half-cell retention over 300 cycles. It also records first-cycle irreversible loss, discharge energy in watt-hours, and gravimetric fill mass to 0.01 g.
SCOPE & LIMITS
Because tests use a single lot of layered sodium transition-metal oxide cathode material, observed retention and fade behaviours do not apply to Prussian-blue-analogue chemistries.
WHO EXECUTES
The kind of lab that can run this
A university battery core facility or contract cell-testing house able to build both sodium half cells and multilayer pouch/full cells and to weigh, meter and cost the actual bill of materials that goes into them.
EXECUTOR KIND
wet-lab
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