The central challenge the team confronted is the peculiar double life that water leads inside a zinc battery. Water is indispensable: it dissolves the zinc salts that carry charge between the electrodes, giving aqueous electrolytes ionic conductivities that organic solvents simply cannot match. Yet the very water molecules that enable fast transport also swarm the zinc anode, where they participate in hydrogen evolution reactions that waste charge, build up gas pressure, and corrode the metal. Free water also encourages the formation of dendrites, needle-like zinc structures that grow unevenly during charging and can eventually pierce separators or detach from the electrode entirely. The trick, therefore, is not to remove water but to discipline it, binding enough of it into the polymer network so that it can no longer mediate destructive side reactions while leaving sufficient mobility for ions to travel freely.

Oxidized sodium alginate turned out to be an unusually capable disciplinarian. Sodium alginate is a polysaccharide extracted from brown algae, and when it is oxidized, the sugar rings in its backbone are opened to create dialdehyde groups along the chain. These aldehyde-bearing chains are chemically versatile: they can form dynamic covalent bonds, participate in hydrogen bonding, and coordinate metal ions. In the new study, the researchers introduced the oxidized alginate into a polyacrylamide matrix, the workhorse polymer of hydrogel electrolytes, and systematically varied the loading. At an optimized dose of 0.9 grams per batch, the resulting gel, dubbed PAM OSA-0.9 GEL, developed a more open and porous microstructure with noticeably improved wettability, meaning electrolyte solutions spread through and saturate the gel far more effectively than in the pristine polyacrylamide control.

The performance numbers tell a striking story. Ionic conductivity, the measure of how easily charge-carrying ions move through the electrolyte, climbed from 16.2 to 28.6 millisiemens per centimeter, an increase of more than 75 percent. Even more consequential was the change in the apparent zinc-ion transference number, which rose from 0.47 to 0.76. This parameter describes the fraction of total current carried by zinc ions rather than by other mobile species such as protons or sulfate anions. A higher transference number means that when current flows, it is predominantly zinc ions doing the work, which translates directly into more uniform zinc deposition and less concentration polarization near the electrode surface. In parallel, the electrochemical stability window widened from 2.47 to 2.64 volts, giving the electrolyte more headroom before it begins to decompose electrochemically.

The researchers attribute these gains to the way oxidized alginate reorganizes the water inside the gel. The aldehyde and hydroxyl groups along the alginate chains form extensive hydrogen-bonding networks with surrounding water molecules, converting a portion of the free, reactive water into bound water that is far less available for hydrogen evolution or zinc corrosion. At the same time, the alginate’s carboxylate groups coordinate zinc ions, reshaping the solvation shells that surround each ion as it migrates. Solvation structure is a recurring theme in modern electrolyte design, because how zinc ions are dressed in coordinating molecules determines how easily they shed that dressing when they arrive at the anode and join the growing metal deposit. By tuning both the water state and the zinc coordination environment simultaneously, the oxidized alginate addresses two failure modes with a single additive.

The consequences for the zinc anode were immediately visible in the electrochemical tests. Hydrogen evolution and zinc corrosion, the twin scourges of aqueous zinc chemistry, were both alleviated in the modified gel. Nucleation and deposition of zinc became more uniform, with the metal plating as dense, even layers rather than the patchy, dendritic growth that plagues conventional electrolytes. Uniform deposition matters enormously for cycle life: when zinc plates evenly, the electrode surface stays flat and the effective area remains constant, whereas dendritic growth creates dead metal, exposes fresh surface to corrosion, and progressively degrades the cell. The improved wettability and porosity of the OSA-modified gel also help by distributing zinc ion flux more evenly across the electrode interface, preventing the local current hotspots where dendrites preferentially nucleate.

Symmetric zinc-zinc cells, in which two identical zinc electrodes are cycled against each other, provided the most direct test of anode stability. Cells built with the PAM OSA-0.9 GEL electrolyte operated continuously for 1300 hours at a current density of 1.0 milliampere per square centimeter and an areal capacity of 1.0 milliampere-hour per square centimeter. For a hydrogel-based system, sustaining plating and stripping for well over fifty days without short-circuiting or catastrophic voltage drift is a demanding benchmark, and it reflects the cumulative benefit of faster ion transport, suppressed side reactions, and homogeneous deposition working in concert.

Full cells pairing the zinc anode with a sodium vanadate cathode, specifically NaV3O8·xH2O, showed that the electrolyte improvements carry through to complete devices. At a moderate rate of 1.0 ampere per gram, the full cells retained 79 percent of their initial capacity after 220 cycles. More impressively, when the researchers pushed the cells to a demanding 5.0 amperes per gram, roughly a fivefold faster charge-discharge regime, the cells still held 58 percent of their capacity after 3500 cycles. Fast-charging stability is where many aqueous zinc systems falter, because high rates amplify concentration gradients and accelerate dendrite formation, so the endurance at 5.0 amperes per gram suggests the gel’s enhanced zinc-ion transport genuinely relieves the kinetic bottlenecks that normally sabotage rapid cycling.

What makes the result particularly appealing is its simplicity and sustainability. Oxidized sodium alginate is derived from abundant, renewable seaweed biomass, and alginate chemistry is already well established in fields ranging from wound dressings to drug delivery, where oxidized alginates are prized for their biodegradability and controllable gelation. The literature on alginate oxidation dates back well over a decade, and the material’s behavior, including how oxidation degree governs degradability and crosslinking, is well characterized. Repurposing this biomedical staple as an electrolyte engineer for grid-scale batteries illustrates how cross-disciplinary materials knowledge can accelerate energy research. The work also aligns with a broader trend in the field: rather than chasing exotic synthetic additives, several recent studies have turned to polysaccharides such as cellulose, chitosan, and alginate, whose dense arrays of oxygen-containing functional groups are naturally suited to binding water and coordinating metal ions.

The road to commercial aqueous zinc batteries still has distance to travel. Cathode dissolution, particularly of vanadium-based materials, remains a concern, and the capacity retention figures, while strong for a hydrogel system, indicate that degradation has not been eliminated. Scaling hydrogel electrolytes from laboratory coin cells to large-format pouch cells introduces additional challenges in mechanical robustness, manufacturing throughput, and long-term water retention. Nevertheless, the Nanjing team’s demonstration that a single seaweed-derived polymer can simultaneously raise conductivity, sharpen ion selectivity, widen the stability window, and calm the anode offers a compelling template. If future designs can stack multiple such molecular strategies, pairing alginate-type water regulators with zincophilic interfaces and optimized cathodes, the vision of safe, inexpensive, water-based batteries for grid storage and flexible electronics moves a meaningful step closer to reality.

Subject of Research: Oxidized sodium alginate-modified polyacrylamide hydrogel electrolytes for stable aqueous zinc-ion batteries

Article Title: Oxidized sodium alginate regulates water state and Zn²⁺ transport in polyacrylamide hydrogel electrolytes for stable aqueous zinc-ion batteries

Article References: Chen, M., Huo, X., Tan, G., Wang, C., Wang, J., & Zhong, Q. (2026). Oxidized sodium alginate regulates water state and Zn²⁺ transport in polyacrylamide hydrogel electrolytes for stable aqueous zinc-ion batteries. Ionics. https://doi.org/10.1007/s11581-026-07523-x

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07523-x

Keywords: aqueous zinc-ion batteries, hydrogel electrolyte, oxidized sodium alginate, polyacrylamide, zinc-ion transport, zinc dendrites, hydrogen evolution, solvation structure, ionic conductivity, transference number, sodium vanadate cathode, energy storage

The central engineering challenge is deceptively simple to state. A battery must store and deliver meaningful energy, yet every component—anode, cathode, electrolyte, separator, current collector and packaging—must remain stable during operation and then degrade predictably into products the body can metabolize or excrete. Conventional lithium-ion chemistry fails this test on nearly every count: lithium is reactive, the organic electrolytes are toxic, and the metal casings persist indefinitely. Designing around those constraints requires rethinking the battery from first principles, choosing electrode materials from the palette of biologically tolerated elements and finding ionic chemistries that function in aqueous, physiological environments.

Among the most promising strategies reported in recent work are metal–air and metal-based cells built around magnesium, zinc, iron, molybdenum and tungsten. Zinc, in particular, has attracted attention because it is an essential trace nutrient, electrochemically well behaved in neutral aqueous media, and yields benign zinc ions and hydroxide species upon discharge. Magnesium offers a higher theoretical voltage and specific capacity and is already widely used in biodegradable orthopedic implants, giving clinicians a long safety track record to draw upon. Pairing these metals with cathodes made from oxides, phosphates or even bio-derived molecules such as iodine and quinones allows researchers to assemble complete cells whose every element participates in the body’s normal biochemistry.

Electrolytes present a subtler problem. The medium through which ions shuttle must conduct well, resist premature self-discharge, and dissolve cleanly afterward. Teams have explored hydrogels cross-linked from natural polymers, salt-loaded chitosan membranes, phosphate-buffered solutions held within biodegradable pouches, and solid polymer electrolytes based on polyethylene glycol and polylactic acid. The encapsulation strategy matters as much as the chemistry: a transient battery is only as transient as its slowest-dissolving layer. Researchers have therefore developed multilayer packaging from polyanhydrides, polycaprolactone and silk fibroin, tuning film thickness and crystallinity so that the operational lifetime can be programmed from days to months, much as drug-eluting stents control their release kinetics.

Power output has long been the Achilles heel of resorbable energy storage, since aqueous chemistries deliver lower cell voltages than lithium systems. The field has responded with clever circuit-level solutions. Stacking individual cells in series within a single package boosts voltage to the levels needed by microcontrollers, radios and sensors, while parallel arrays extend operating time. Reports of transient batteries generating on the order of one to a few volts, sufficient to power cardiac pacemakers in large animal models and to drive wireless transmission from implantable sensors, have shifted the conversation from feasibility to engineering refinement. Energy densities approaching levels useful for clinical devices have been demonstrated in packages small enough to fit within the capsule formats familiar from swallowable diagnostics.

The ingestible application is arguably the most immediate. Electronic capsules that sample the gastrointestinal tract, deliver drugs on schedule, or monitor pH, temperature and pressure currently contain rigid, persistent hardware. A power source that dissolves after a defined period means the device can be designed to break apart and pass or absorb without intervention, reducing the risk of retained foreign bodies and simplifying regulatory pathways. Transient batteries have been engineered to survive the acidic environment of the stomach, activate in the intestine, and maintain output long enough to complete a diagnostic or therapeutic mission before their hydrogel electrolytes swell, weaken and finally dissolve into the surrounding fluid.

Implanted applications raise the stakes in different ways. Temporary pacemakers intended to support patients after cardiac surgery, biodegradable sensors for monitoring wound healing, and stimulators for nerve regeneration all require power for days to weeks and none of the encumbrance of permanent hardware. In animal studies, resorbable battery packs have successfully paced hearts at clinically relevant rates and then degraded over weeks with no significant inflammatory response, the degradation products appearing at concentrations well within physiological tolerance. Surgeons and cardiologists watching these demonstrations see a path to devices that avoid the extraction procedures, infections and device erosion complications that complicate conventional implants.

Safety evaluation is where laboratory promise meets biological reality, and the field has been accumulating the necessary evidence. Biocompatibility testing of the constituent materials—zinc, magnesium, molybdenum, tungsten, silk, chitosan, PLGA and related polymers—shows degradation products that are cleared renally or metabolized into water and carbon dioxide. Histological examination of implantation sites typically reveals a mild, transient foreign-body response that resolves as the materials disappear. The critical design parameter is the balance of dissolution rates: the battery must not release its stored electrochemical charge or its degradation products faster than tissue clearance mechanisms can handle, a constraint that drives careful control of surface area, porosity and protective coatings.

Manufacturing and integration remain open questions on the road to commercialization. Many laboratory devices are assembled by hand from foils, films and gels; scaling to consistent, sterile, high-volume production demands reel-to-reel deposition, laser micromachining and packaging methods borrowed from flexible electronics. Integration with ultrathin silicon sensors, biodegradable antennas and dissolvable interconnects is advancing rapidly, driven by parallel progress in transient semiconductor research. As these threads converge, researchers envision complete diagnostic and therapeutic systems—power, electronics, antenna and all—that are implanted or swallowed, perform their function, and vanish, leaving nothing behind but a small, harmless chemical trace.

For patients, the implications extend beyond convenience. Eliminating extraction surgeries removes anesthesia risks, costs and anxiety; for pediatric and elderly populations especially, any procedure avoided is meaningful. For health systems, self-erasing devices could reduce long-term follow-up burdens. The research community is candid that clinical adoption will require years of validation, standardization of degradation timelines and regulatory frameworks adapted to hardware that is designed to fail safely. But the trajectory is clear: energy storage is joining the broader movement toward medical technology that respects the body’s own temporality, delivering function precisely when it is needed and then, quietly and completely, disappearing.

Subject of Research: Development of biodegradable, transient power sources for ingestible and implantable bioelectronics

Article Title: Bioresorbable batteries for transient ingestible bioelectronics

Article References: Say, M. G., Erus, A., Morgan, L., Cai, Y., Moon, I., Park, Y.-G., DeBruyn, B., Kang, Z., Parvataneni, K., Akouissi, O., Girand, O., You, S. S., Pettinari, A., Guevara, A., Laidlaw, B., Schmidt, K., Fabian, N., Hayward, A., & Traverso, G. (2026). Bioresorbable batteries for transient ingestible bioelectronics. Nature Chemical Engineering. https://doi.org/10.1038/s44286-026-00443-7

Image Credits: AI Generated

DOI: 10.1038/s44286-026-00443-7

Keywords: bioresorbable batteries, transient electronics, ingestible devices, biodegradable implants, zinc battery, magnesium anode, hydrogel electrolyte, biocompatibility, implantable sensors, transient pacemaker, biomedical engineering, dissolvable electronics