Researchers at RWTH Aachen University have performed the first detailed teardown and characterization of a commercial sodium-ion battery cell from China’s HiNa Battery, finding that its manufacturing quality, cell-to-cell uniformity and tabless architecture, is comparable to Tesla’s industry-leading 4680 lithium-ion cells, even though its energy density remains roughly half.
The findings, published in Cell Reports Physical Science on May 28, offer an independent look at a technology many see as a potential low-cost complement to lithium-ion for grid storage and short-range electric vehicles.
What they found
The team, led by Christian Siebert and Moritz Schütte at RWTH Aachen’s Institute for Power Electronics and Electrical Drives (ISEA), took apart and tested over 120 HiNa NaCR33140-MP10 cells, cylindrical 33140-format cells (33.2 mm diameter, 140 mm height) mass-produced by HiNa Battery, a Chinese company founded in 2017.
The cell delivers 10 Ah at 3.0 V nominal, for a total energy of about 30 Wh per cell. Its gravimetric energy density is 110 Wh/kg, substantial for a sodium-ion cell but roughly half that of Tesla’s 4680 cells (241, 296 Wh/kg, depending on chemistry).
What surprised the researchers was the production quality. The cell-to-cell impedance variance across 120 cells was just 5.27%, a level of uniformity the authors describe as “comparable to well-established lithium-ion batteries.” The cells also use a double-aluminum tabless architecture, closely mirroring the design Tesla pioneered with its 4680 format to reduce internal resistance and improve heat distribution.
“It is important to note that the comparison with Tesla refers specifically to manufacturing quality and design features, not absolute energy performance,” Schütte said. The HiNa cell uses aluminum current collectors on both electrodes, unlike conventional lithium-ion batteries, which use heavier copper foil on the anode side, contributing to its respectable weight figure.
The chemistry inside
The cathode is a layered oxide with the formula NaCu1/9Ni2/9Fe1/3Mn1/3O2, double-coated on aluminum foil. One unexpected finding: copper was distributed unevenly within individual cathode particles, reaching up to 25.1 atomic percent locally versus a global average of just 1.7 percent. The researchers note this raises “interesting questions about its role in performance and aging” that remain unresolved.
The anode uses hard carbon, the standard for sodium-ion, also double-coated on aluminum foil. The electrolyte is a propylene carbonate / ethylene propionate mixture with sodium salts and sulfone-based additives.
Cold performance, the weak link
The cell performs well at moderate temperatures: at 25°C it delivers 10.7 Ah at a slow C/15 rate, and at 45°C it reaches 10.8 Ah. At -10°C it still delivers 8.2 Ah, about 77% of room-temperature capacity.
But charging in the cold is a clear limitation. At -20°C, the cell retains only 56% of its capacity when charged, though it can still discharge about 82% of its stored energy. The researchers are explicit about the implication: “For applications that require frequent charging at low ambient temperatures, appropriate thermal management or operating strategies will be important.”
Power capability, however, is strong. The cell delivers over 10 Ah at rates up to 4C, meaning it can be fully charged or discharged in 15 minutes, and the manufacturer specifies a cycle life exceeding 3,000 cycles at over 80% depth of discharge.
What this means
HiNa’s own newer “Haixing” pack, announced in March 2025, already claims cell-level energy densities above 165 Wh/kg and cycle lives exceeding 8,000 cycles, meaning the 33140 cells studied here represent an earlier generation. The company projects cost parity with lithium-ion by 2027, 2028.
“The sodium-ion technology is less mature than lithium-ion,” the authors note, characterizing these cells as “early commercial” products. The study did not measure cost directly.
For applications where weight and volume matter less than cost and safety, grid-scale storage, low-speed vehicles, and backup power, sodium-ion batteries offer sodium’s natural abundance and the ability to ship fully discharged (reducing fire risk during transport). The Aachen team’s detailed teardown provides the first independent verification that Chinese manufacturers can produce these cells at a quality level that matches the world’s best lithium-ion factories.
Caveats
The study examined beginning-of-life cells only; long-term aging behavior was not characterized. The paper also does not compare the HiNa cell directly against other commercial sodium-ion products or provide a cost-per-kilowatt-hour analysis. And the unexpected copper segregation in the cathode material raises open questions about long-term stability that will need to be addressed as the technology scales.
Source: Siebert, C., Schütte, M., Rinner, J. et al. “Cell teardown and characterization of a Hina commercial sodium-ion battery.” Cell Reports Physical Science 7, 103323 (2026). DOI: 10.1016/j.xcrp.2026.103323