Researchers at Columbia Engineering have developed a new gel electrolyte that both improves the lifetime and safety of anode-free lithium batteries, an emerging battery architecture that could dramatically boost energy density while simplifying manufacturing. Although such design promises higher energy density and lower cost, the approach has long been plagued by short battery life and safety concerns caused by unstable lithium plating and parasitic reactions at the electrode-electrolyte interface.
The Columbia team, led by Yuan Yang, associate professor of applied physics and applied mathematics at Columbia Engineering, addressed these challenges by rethinking how polymer electrolytes interact with lithium ions at the nanoscale.
A "Salt-Phobic" polymer network that reshapes ion solvation
The researchers designed a gel polymer electrolyte that contains a parasitic salt-phobic polymer network. This structure overcomes previous challenges by selectively repelling lithium salts while attracting solvent molecules. This unique chemical contrast spontaneously divides the electrolyte into nanoscale domains with different local compositions, which favors the formation of an efficient protective layer on the lithium surface.
"In these confined regions, lithium ions are forced to coordinate more strongly with anions rather than solvent molecules," said Yang. "That anion-rich solvation environment fundamentally changes how the solid electrolyte interphase forms."
Where previous attempts to solve this problem have used large quantities of fluorinated electrolytes, the new approach incorporates the electrolytes directly into the polymer backbone. This enabled the researchers to develop smaller, less expensive, and more efficient batteries.
Stabilizing lithium–electrolyte interface
Advanced spectroscopy, cryogenic electron microscopy, and molecular simulations revealed that this salt-phobic network promotes the formation of a thin, inorganic-rich interphase. This interphase enables smoother, denser lithium deposition and suppresses parasitic reactions that typically consume active lithium in anode-free cells. As a result, anode-free pouch cells using the new gel electrolyte retained over 80% of their capacity after hundreds of cycles under demanding conditions, including high areal capacity, lean electrolyte content, and low external pressure—parameters that closely resemble those required for practical electric vehicle batteries.
Enhanced safety under extreme conditions
Beyond extending battery life, the gel electrolyte also improves thermal stability. In abuse tests, multilayer anode-free pouch cells equipped with the new electrolyte withstood aggressive drilling without thermal runaway, while comparable cells using conventional liquid electrolytes ignited or exploded. "These results show that polymer chemistry can be a powerful and underexplored lever for controlling solvation structure and interfacial stability," said the study's first author Shengyu Cong, a postdoctoral research scientist with Yang. Yang said. "By embedding safety and durability directly into the electrolyte architecture, we can push anode-free batteries closer to real-world deployment."
Toward practical high-energy batteries
The work highlights a new design principle for gel electrolytes, using polymer backbone chemistry to engineer nanoscale solvation environments rather than relying on extreme electrolyte formulations. The researchers believe this strategy could be extended beyond lithium to other alkali-metal batteries, opening new pathways for safer, high-energy-density storage technologies.
