PVA-Cu leads the first comparison
A copper-containing polymer binder was linked to higher reported capacity than a polymer-only control in laboratory lithium-sulfur, or Li-S, cells. In the main capacity screen, at a sulfur loading of 3 mg per square centimetre and 1 C, cells using PVA-Cu averaged 1,130 mAh per gram. The PVA-only control averaged 745 mAh per gram under the same conditions. The result came from a screen of six main sulfur-cathode formulations. For this comparison, the values were averages from three independently assembled cells, with error bars representing standard deviation.
The full screen put PVA-Cu at the top. PVA-Fe, PVA-Zn, PVA-Ga and PVA-Al recorded 992, 983, 895 and 837 mAh per gram, respectively, while PVA-only was lowest at 745. The cathodes used 65% sulfur, 20% conductive carbon and 15% binder by weight. The six main cathode types included PVA-metal hybrids and a metal-free control.
The difference remained across the tested rate range. At 0.1 C, PVA-Cu delivered 1,598 mAh per gram, falling to 1,131 at 2 C, for reported retention of 71%. PVA-only went from 1,208 to 708 mAh per gram, with 58% retention. The supplied analysis does not give replicate counts or uncertainty for this rate series.
Performance under heavier sulfur loads
The study also tested PVA-Cu at higher sulfur loadings. At 3 mg per square centimetre and 1 C, the cell began at 1,100 mAh per gram and retained 82% after 300 cycles. At 6 mg per square centimetre and 1 C, it delivered 622 mAh per gram, equivalent to 3.7 mAh per square centimetre, with 70% retention after 100 cycles. At 9 mg per square centimetre and 0.5 C, it delivered 813 mAh per gram, or 7.3 mAh per square centimetre.
In another high-loading series, the PVA-binder cell delivered 791 mAh per gram and 5.5 mAh per square centimetre at 7 mg per square centimetre and 0.5 C, with the reported performance sustained for 100 cycles. At 9 and 13 mg per square centimetre, areal capacity reached 7.3 and 14.7 mAh per square centimetre at 0.5 and 0.1 C, respectively. Both figures were at or above the study's stated practical benchmark of 4 mAh per square centimetre. The text also reports a linear increase in areal capacity across 2 to 9 mg per square centimetre at 0.5 C.
The chemistry points in the same direction
The electrochemical work used galvanostatic charge-discharge tests, cyclic voltammetry, electrochemical impedance spectroscopy and temperature-dependent impedance measurements. The reported kinetic measures, which describe how readily the reactions proceed, favored PVA-Cu over PVA-only. Polarization was 319 millivolts for PVA-Cu versus 453 millivolts for PVA-only. The second-reduction-peak Tafel slope, another measure used to compare reaction kinetics, was 56 versus 91 millivolts per decade. Charge-transfer resistance was 9.5 versus 15.3 ohms. Reported activation energy was 6.5 versus 13.8 kilojoules per mole at 2.05 volts, and 11.0 versus 15.2 kilojoules per mole at 1.8 volts.
The study also measured how lithium sulfide, or Li2S, formed and dissolved. PVA-Cu reached a reported Li2S deposition capacity of 210 mAh per gram in 37.1 minutes, versus 91 mAh per gram in 231.0 minutes for PVA-only. During dissolution, PVA-Cu reached 708 mAh per gram in 23.3 minutes, compared with 447 mAh per gram in 40.6 minutes. Deposition was described as predominantly three-dimensional for PVA-Cu, rather than the mixed two-dimensional and three-dimensional pattern reported for PVA.
Density-functional-theory calculations offered a possible explanation, but they were not a direct observation of a working full cell. The calculations used model polymer-metal surfaces and examined charge and electronic-state descriptors when sulfur species were adsorbed. They reported the largest positive charge changes at the copper centre after Li2S adsorption, +1.500 elementary charges, and Li2S6 adsorption, +0.663 elementary charges. After Li2S6 adsorption, the calculated integrated density of states rose from 1.00 to 2.02 for Cu and from 0.00 to 2.89 for Fe. The calculated electronic states also showed overlap between copper d orbitals and sulfur p orbitals. These descriptors were consistent with the proposed PVA-Cu mechanism, but direct full-cell mechanistic validation was not reported.
Pouch tests offer a practical check
Three PVA-Cu pouch prototypes were tested at 0.5 C. The first used two layers, with 3.3 mg per square centimetre of sulfur on each side and an electrolyte-to-sulfur ratio of 6. After the stated conditioning sequence, it delivered 790 mAh per gram, 140 Wh per kilogram and 150 W per kilogram at 0.5 C for 20 cycles. A second pouch containing 100 mg of sulfur reached 132 W per kilogram and retained 80% capacity over 100 cycles. A third, with 120 mg of sulfur in a single-layer design, reached 140 W per kilogram and operated stably for 60 cycles at 0.5 C.
The reported pouch energy figure needs careful reading. Specific energy was calculated from output voltage and capacity divided by the total mass of the pouch components, while specific power used the actual discharge time. Packaging materials and tabs were excluded from the energy-density calculation. The three prototypes and their limited cycle durations do not establish long-term device durability, and complete variability was not reported.
What the tests do not settle
Most experiments did not report overall cell counts or replicate variability. Sulfur loading, electrolyte-to-sulfur ratio, current density and cell format varied across tests, limiting direct comparisons between conditions. The computational results came from model surfaces, while literature benchmarking used differing protocols and mass-accounting conventions. Further work will need longer cycling, scale-up, independent laboratory replication and tests connecting the model descriptors with measured full-cell kinetics.
The article reports receipt on July 7, revision on July 20 and acceptance on August 11, 2026, along with open-access licensing. It reports support from the Air Force Office of Scientific Research and the ARC Research Hub for Advanced Manufacturing with 2D materials. The document states that M.M.N., P.J., M.S. and M.M. are authors of a patent application, while the other authors declare no competing interests. Supporting data are available from the corresponding author on request but are not publicly available because of stated privacy or ethical restrictions.
Paper data and sources
Original title: Bidirectional Soft Catalysts for Improved Power Performance of Li-S Batteries.
Authors: Maleesha M Nishshanke, Petar Jovanovic, Swarit Dwivedi et al.
Journal/Repository: Advanced science (Weinheim, Baden-Wurttemberg, Germany)
Status: Peer-reviewed
First online: 2026-08-21
DOI: 10.1002/advs.77302
Original paper