In the race to build lithium-ion batteries that can charge in minutes rather than hours, the biggest obstacles are no longer the electrodes but the electrolyte and the hidden chemical interfaces inside the cell. Now, a team of researchers from Central South University, Changsha University of Science and Technology and Tianjin Lishen Battery has unveiled a gel polymer electrolyte that addresses both problems at once. By embedding a zwitterionic polymer network—molecules carrying paired positive and negative charges—inside a conventional carbonate-based liquid electrolyte, the team created a material that physically separates lithium-ion motion from anion motion, delivering fast-charging performance in full-size pouch cells that conventional gel electrolytes cannot match.
The new material, described in the journal Ionics, was produced by a process called in-situ copolymerization. The researchers mixed two liquid monomers—sulfobetaine methacrylate (SBMA), a zwitterionic molecule, and pentaerythritol triacrylate, a three-armed crosslinker—directly into the liquid carbonate electrolyte of an assembled cell. When polymerized, the monomers form a solid yet solvent-swollen gel that fills the separator and electrode pores without the need to disassemble or re-stack the cell. This in-situ strategy is industrially attractive because it preserves intimate contact between the electrolyte and the rough, porous surfaces of battery electrodes, a contact that is notoriously difficult to achieve with pre-made polymer films.
The chemical trick at the heart of the material lies in how it treats the two charged species in a battery. In a standard liquid electrolyte, lithium ions travel surrounded by a shell of solvent molecules and, often, PF6- anions; when current flows, both cations and anions drift in opposite directions. This coupled motion wastes driving force, builds up concentration gradients under high current, and delivers anions to the anode surface where they decompose. In the zwitterionic gel, however, the permanently charged sulfobetaine groups act as electrostatic anchors that immobilize the PF6- anions, while the same framework offers dynamic coordination sites where lithium ions can briefly bind and then hop to the next site. The result is a hopping transport mechanism in which lithium migration is decoupled from both anion flux and the sluggish segmental motion of the polymer backbone itself.
The measured numbers underscore why this matters. The gel achieves a room-temperature ionic conductivity of 6.72 millisiemens per centimeter—approaching the range of free-flowing liquid electrolytes and far above most solid polymer electrolytes. More striking is the lithium-ion transference number of 0.69, meaning nearly seven of every ten charge carriers moving through the electrolyte are lithium ions rather than anions. Typical liquid electrolytes have transference numbers around 0.3 to 0.4, which means most of the current is carried by anions that contribute nothing to storing energy and much to degrading the cell. A high transference number reduces concentration polarization, allowing the cell to sustain high charging rates without the lithium depletion at the anode that triggers damaging lithium plating.
To test the concept under realistic fast-charging stress, the researchers built 1 ampere-hour pouch cells pairing an NCM523 layered oxide cathode—nickel-rich lithium nickel cobalt manganese oxide—with graphite anodes, the same chemistry family used in commercial electric vehicle batteries. The cells were cycled at a punishing regime of 2C charging, meaning a full charge in half an hour, combined with 5C discharging, or twelve minutes to empty. After 500 such cycles, the cells with the zwitterionic gel retained 80.7 percent of their original capacity. Both the pristine liquid electrolyte and a non-zwitterionic gel counterpart faded substantially faster under the same conditions, demonstrating that the zwitterionic solvation strategy, not merely the gelling itself, was responsible for the endurance.
The mechanistic story behind this durability lies in the interfacial films that form on the electrodes. Every lithium-ion battery contains two crucial passivation layers: the solid electrolyte interphase (SEI) on the anode and the cathode electrolyte interphase (CEI) on the cathode. When anions and solvent molecules decompose uncontrollably, these films grow thick, porous and chemically heterogeneous, adding resistance and consuming lithium inventory. In the zwitterionic gel, the regulated solvation environment—where lithium ions are coordinated by the polymer’s charged sites rather than by reactive solvent clusters—changes the decomposition chemistry itself. On the graphite anode, the team observed a robust interphase enriched in lithium fluoride (LiF), an inorganic compound prized for its chemical stability and high interfacial energy that suppresses parasitic side reactions.
On the cathode side, the improvement was equally pronounced. The NCM523 cathode developed an ultrathin CEI of only about 5 nanometers—roughly a hundred times thinner than a human red blood cell is wide—that was uniform and dominated by inorganic species. Thin, inorganic-rich interphases conduct lithium ions efficiently while blocking electrons and solvent, protecting the high-voltage cathode from transition-metal dissolution and electrolyte oxidation. Together, the LiF-rich SEI and the nanometer-scale CEI explain how the cells survived half a thousand aggressive cycles: the electrolyte spent its early cycles building near-ideal protective layers, then simply kept working.
The decoupling of ion transport also has a subtle kinetic benefit for fast charging. During rapid charge, lithium ions are consumed at the graphite anode far faster than they can diffuse through the electrolyte and through the SEI. If anions must move to balance the charge, large salt concentration gradients form, lowering the local lithium concentration at the anode surface until metallic lithium plates directly instead of intercalating into graphite—an effect that both erodes capacity and, in the worst case, short-circuits the cell. With anions largely pinned in place by the zwitterionic network, the concentration gradient is shallower, and the effective lithium supply at the anode remains adequate even at 2C charging rates.
Zwitterionic materials have been drawing growing attention in electrolyte research, and this work builds on a broader trend. Zwitterions and zwitterionic polymers have previously been explored for lithium-sulfur batteries, for low-temperature lithium metal cells, and as additives that modulate the solvation sheath of lithium ions. What distinguishes the new study is the combination of a practical in-situ fabrication route, compatibility with standard carbonate electrolytes and commercial electrode chemistries, and demonstration in genuine 1 Ah pouch cells rather than small coin cells—a scale where many laboratory breakthroughs quietly fail. The collaboration with Tianjin Lishen Battery, a major Chinese cell manufacturer, suggests the researchers are attentive to manufacturability from the start.
The work was supported by the Natural Science Foundation of Hunan Province and the National Natural Science Foundation of China, and the research team included Yan Tong, Maohui Bai, Xuhui Wang, Xihao Zou, Shu Hong, Bo Hong and Yanqing Lai. Fast charging has become one of the most fiercely contested battlegrounds in battery development, because charging time is consistently cited by consumers as a barrier to electric vehicle adoption, and because grid storage operators value the flexibility that rapidly rechargeable systems provide. Yet pushing current through a cell heats it, stresses its interfaces and invites lithium plating; nearly every proposed solution involves trade-offs among conductivity, safety, cost and cycle life.
Gel polymer electrolytes occupy a compelling middle ground in this trade-off landscape: they retain most of the ionic conductivity of liquids while offering the leak resistance, mechanical robustness and improved safety of solids. What they have historically lacked is control—control over which ions move, control over how lithium is solvated, and control over the interfacial chemistry that ultimately determines whether a cell lives for a decade or dies in a year. The zwitterionic design described in Ionics shows that this control can be engineered directly into the polymer architecture rather than bolted on through additives.
If the approach proves scalable, the implications extend beyond fast-charging electric cars. High-transference-number electrolytes could ease thermal management burdens, permit thinner electrodes and higher energy densities, and improve the low-temperature behavior of cells by reducing concentration polarization in sluggish electrolytes. The researchers describe their zwitterionic solvation strategy as a general pathway—one that other labs can adapt by tuning the balance between anion immobilization and lithium coordination in related polymer chemistries. For now, the demonstration of 500 stable fast-charge cycles at pouch-cell scale with a transference number of 0.69 marks a significant step toward batteries that can drink from a high-power charger as casually as they deliver power on the road.
Subject of Research: A zwitterionic gel polymer electrolyte with decoupled ion transport for fast-charging lithium-ion batteries
Subject of Research: Technology and Engineering
Article Title: Decoupled ion transport in zwitterionic gel electrolytes for fast-charging lithium-ion batteries
Article References: Tong, Y., Bai, M., Wang, X., Zou, X., Hong, S., Hong, B., & Lai, Y. (2026). Decoupled ion transport in zwitterionic gel electrolytes for fast-charging lithium-ion batteries. Ionics. https://doi.org/10.1007/s11581-026-07467-2
Image Credits: AI Generated
DOI: 10.1007/s11581-026-07467-2
Keywords: Zwitterionic polymer, Gel polymer electrolyte, Lithium-ion battery, Solvation structure, Fast charging, Li+ transference number, Solid electrolyte interphase, Cathode electrolyte interphase, In-situ polymerization, Ionic conductivity
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Denise Maddox. (September 6, 2026). Zwitterionic gel electrolytes enable fast-charging lithium-ion batteries. Scienmag. https://scienmag.com/zwitterionic-gel-electrolytes-enable-fast-charging-lithium-ion-batteries/
Denise Maddox. “Zwitterionic gel electrolytes enable fast-charging lithium-ion batteries.” Scienmag, 6 September 2026, https://scienmag.com/zwitterionic-gel-electrolytes-enable-fast-charging-lithium-ion-batteries/. Accessed 6 September 2026.
Denise Maddox. “Zwitterionic gel electrolytes enable fast-charging lithium-ion batteries.” Scienmag. September 6, 2026. https://scienmag.com/zwitterionic-gel-electrolytes-enable-fast-charging-lithium-ion-batteries/
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