Gotu Kola Powers a New Solid Electrolyte for Magnesium Batteries

A humble herb better known for its role in traditional medicine than in electrochemistry has just delivered a surprisingly capable battery component. Researchers in India have turned Centella asiatica—the leafy plant commonly called gotu kola—into a flexible, solid electrolyte membrane that conducts magnesium ions with remarkable efficiency, and they have shown that it can actually power a working primary magnesium battery. The study, published in the journal Ionics by M. Megaraj Begam, MV. Leena Chandra, and the late S. Selvasekarapandian, describes a biomaterial electrolyte that combines a plant-derived polymer matrix with magnesium chloride hexahydrate and a plasticizer called succinonitrile. The result is a membrane that is biodegradable, mechanically flexible, and capable of ionic conductivities that rival many synthetic polymer electrolytes.

The appeal of solid electrolytes in battery research is easy to understand. Conventional batteries rely on liquid electrolytes—flammable organic solvents that carry ions between the electrodes but also introduce risks of leakage, fire, and chemical degradation. Replacing that liquid with a solid film would make batteries safer, more compact, and potentially compatible with flexible and implantable electronics. The catch is that most solid electrolytes, whether ceramic or polymer based, struggle to move ions as freely as liquids do. Magnesium adds another layer of difficulty: the doubly charged Mg2+ ion interacts strongly with its surroundings, making it notoriously sluggish inside solid frameworks. That is precisely why the conductivity numbers reported in this study turn heads.

The team fabricated their membranes using a straightforward solution casting technique, dissolving Centella asiatica material with magnesium chloride hexahydrate and then adding succinonitrile as a plasticizer. Succinonitrile is an intriguing molecule in its own right—it is a plastic crystal, a solid whose molecules rotate freely in a disordered lattice, and this rotational mobility creates pathways through which ions can hop. When blended into a polymer host, it loosens the rigid structure, suppresses crystallinity, and dramatically increases the fraction of amorphous material where ion transport is fastest. The researchers confirmed these structural changes with a battery of analytical techniques, including scanning electron microscopy with energy-dispersive X-ray analysis, elemental mapping, X-ray diffraction, and X-ray photoelectron spectroscopy.

Those characterization methods told a coherent story. Electron microscopy and elemental mapping showed that the magnesium, chlorine, and nitrogen species were distributed uniformly throughout the membrane, with no signs of the salt agglomeration that plagues poorly formulated polymer electrolytes. X-ray diffraction revealed a dominance of amorphous phases after succinonitrile incorporation—a critical feature, because crystalline regions in a polymer act as barriers that force ions to take long, tortuous detours. X-ray photoelectron spectroscopy verified the chemical interactions between the plant polymer, the magnesium salt, and the plasticizer, confirming that the components were genuinely complexed rather than simply mixed together in a fragile physical blend.

Thermal analysis added further support. Differential scanning calorimetry measured a glass transition temperature of 56.8 degrees Celsius for the plasticized membrane, a reduction that signals enhanced chain mobility in the polymer backbone. Thermogravimetric analysis demonstrated robust thermal stability, meaning the membrane will not decompose under the modest operating temperatures a battery is likely to encounter. This combination of low glass transition temperature and good thermal endurance is the sweet spot that electrolyte designers chase: the polymer chains must wiggle enough to let ions pass, yet the material must hold together over time and temperature without softening into uselessness or breaking down chemically.

The electrical measurements are where the study delivers its headline numbers. Using AC impedance spectroscopy, the researchers measured an ionic conductivity of 1.17 times ten to the minus four siemens per centimeter for the unplasticized membrane. After adding succinonitrile, that figure jumped fifteen-fold to 1.76 times ten to the minus three siemens per centimeter—one of the more respectable values reported for magnesium-ion-conducting biopolymer electrolytes. Temperature-dependent dielectric analysis showed that conduction followed the expected thermally activated behavior, consistent with ions hopping between coordinating sites along the flexible polymer chains. Evans and Wagner polarization measurements were used to determine the transference number, confirming that the current is carried overwhelmingly by ions rather than electrons—an essential property for any electrolyte, since electronic leakage would slowly self-discharge the cell.

Electrochemical stability is often the Achilles heel of biopolymer electrolytes, but here too the results were encouraging. Linear sweep voltammetry established a stability window extending up to 2.74 volts, wide enough to support practical magnesium battery chemistries. Cyclic voltammetry demonstrated high reversibility over 150 cycles, indicating that the electrode processes at the membrane interface could proceed repeatedly without severe degradation or passivation. For a material derived from a medicinal plant, sustaining 150 reversible electrochemical cycles is a meaningful benchmark, suggesting the membrane interface remains chemically compatible with the electrode materials over extended operation.

The proof, of course, lies in an actual device. The team assembled primary magnesium-ion batteries using their highest-conductivity plasticized membrane as the electrolyte separator, paired with two different cathode materials. With molybdenum disulfide as the cathode, the cell delivered an open-circuit voltage of 1.96 volts; with manganese dioxide, it delivered 1.91 volts under load testing. Both values are consistent with the thermodynamics of magnesium-based primary cells and demonstrate that the biomaterial electrolyte is not merely a laboratory curiosity that performs well in isolation—it can function as the working heart of a complete electrochemical cell.

The choice of Centella asiatica as the polymer host deserves attention. The plant is rich in polysaccharides and other oxygen-bearing functional groups that can coordinate magnesium ions and provide the hopping sites needed for conduction. It is also abundant, inexpensive, and biodegradable, which aligns with a growing movement in materials science toward sustainable, environmentally benign battery components. Previous work from the same research group and others has explored biopolymer electrolytes derived from cellulose acetate, pectin, gellan gum, agar, tamarind seed polysaccharide, sodium alginate, and even corn silk extract, building a body of evidence that natural polymers can serve as credible hosts for ion-conducting membranes. This study extends that lineage by showing that Centella asiatica, when properly complexed with a magnesium salt and plasticized with succinonitrile, can reach conductivities at the upper end of the biopolymer electrolyte spectrum.

There are, naturally, caveats. These are primary batteries, not rechargeable ones, and magnesium’s tendency to form passivating layers on metal anodes remains a formidable obstacle to rechargeable magnesium technology. The 2.74-volt stability window, while adequate for the demonstrated cells, would need to widen considerably for high-voltage applications. And scaling from laboratory-cast films to industrially manufactured membranes always presents challenges in reproducibility and mechanical consistency. Still, the study offers a compelling demonstration that the path to safer, greener batteries may run through unexpected territory. A plant prized for centuries in traditional healing now helps shuttle charged atoms through a solid film—and in doing so, it lights up a small but promising corner of the future of energy storage.

Subject of Research: Succinonitrile-plasticized Centella asiatica-based solid biomaterial electrolytes for primary magnesium batteries

Article Title: Succinonitrile-plasticized centella asiatica-based solid biomaterial electrolytes for primary magnesium batteries

Article References: Begam, M. M., Chandra, M. L., & Selvasekarapandian, S. (2026). Succinonitrile-plasticized centella asiatica-based solid biomaterial electrolytes for primary magnesium batteries. Ionics. https://doi.org/10.1007/s11581-026-07538-4

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07538-4

Keywords: solid electrolyte, biomaterial, Centella asiatica, magnesium battery, succinonitrile, ionic conductivity, polymer electrolyte, MgCl2, primary battery, biodegradable materials, electrochemistry, energy storage