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Scientists at the Ulsan National Institute of Science and Technology (UNIST) have unveiled a remarkably simple but highly effective method to boost the performance of solid-state batteries: physically stretching the electrolyte material. The technique, detailed in Energy Storage Materials, significantly improves ion transport and durability, marking a promising advance toward safer electric vehicle batteries and flexible electronics.
The research, led by Professor Seok Ju Kang and first author Jonggeon Na, tackles a persistent limitation of solid-state batteries, slow lithium-ion movement through rigid electrolyte structures. Unlike traditional lithium-ion cells that use flammable liquid electrolytes, solid-state designs are safer but often brittle and inefficient. UNIST’s approach applies a uniaxial stretch to a flexible polymer electrolyte (PVDF-TrFE-CFE) enhanced with ceramic particles (LLZTO), dramatically restructuring the material.
According to the team, stretching increases lithium-ion diffusion 4.8-fold and boosts ionic conductivity by 72% compared to unstretched samples. The mechanical action essentially untangles the polymer chains, opening continuous pathways for ions, a structural improvement achieved without altering the chemistry. When paired with lithium-metal anodes and lithium iron phosphate (LFP) cathodes, the stretched electrolyte retained 78% capacity after 200 cycles, compared to just 55 percent in its original form.
“This research demonstrates that the inherent issues of polymer electrolytes—such as hindered lithium-ion transport—can be effectively addressed through a simple physical process like stretching,” explained Jonggeon Na, a researcher at the School of Energy and Chemical Engineering at UNIST and the study’s first author.
Safety results are equally compelling. The flame-retardant polymer extinguished itself within four seconds in burn tests, addressing one of the major concerns around EV battery fires. The LLZTO ceramic also strengthened the material, improving flexibility and resistance to cracking.
“Polymer electrolytes are more flexible and easier to produce at scale compared to inorganic solid electrolytes. The method developed in this study can be applied to various types of polymer electrolytes, accelerating the commercialization of safer, longer-lasting all-solid-state batteries,” said Professor Seok Ju Kang.
The breakthrough arrives as the EV market seeks commercially viable solid-state solutions. Despite billions invested globally, many prototypes still struggle with rapid performance decay. UNIST’s low-cost, post-production enhancement could accelerate progress without demanding new chemistries.
Beyond vehicles, the stretch-engineered electrolytes could benefit drones, medical devices, and next-generation wearables requiring durable, flexible power sources.
