Researchers develop tri-layer electrolyte for lithium-metal batteries

A research team led by scientists from South Korea’s Chonnam National University has developed a new tri-layer composite solid electrolyte for next-generation rechargeable lithium metal batteries (LMBs).

With enhanced ionic conductivity and mechanical durability, the new electrolyte is designed to address low ionic conductivity, dendrite formation, and interfacial instability, which can limit cycling life and safety.

“Inspired by the natural adhesive proteins mussels use to stick to rocks, our tri-layer composite incorporates chemically active ceramic fillers with a flexible triblock copolymer, boosting ionic conductivity and mechanical strength,” said corresponding author Mincheol Chang in a statement.

“Our electrolyte is designed for next-generation lithium-metal batteries that can enable longer driving ranges for electric vehicles, safer batteries, flexible and wearable electronics, and long-cycle-life grid-scale energy storage,” he added.

The proposed tri-layer architecture consists of soft outer layers made of a PEO/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) matrix surrounding a harder central layer reinforced with polydopamine (PDA)-coated Li7La3Zr2O12 (LLZO) particles and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PPP).

To fabricate the membrane, the researchers first dispersed PDA@LLZO in acetonitrile via magnetic stirring and sonication, then added PPP and the PEO-LiTFSI matrix to form a homogeneous slurry. They prepared four formulations containing 10 wt%, 20 wt%, 30 wt% and 40 wt% PDA@LLZO, labeled CSE-10, CSE-20, CSE-30 and CSE-40. The mixtures were then tape-cast into self-supporting composite films, which were then sandwiched between two PEO-LiTFSI layers and thermally laminated by hot pressing.

In this structure, the soft outer layers were designed to contact the electrodes and facilitate Li+ transport. Meanwhile, the central PDA@LLZO-PPP layer forms a mechanically robust and highly conductive backbone. The PDA-coated LLZO improves Li+-ion mobility through enhanced polymer-ceramic interactions and helps restrict TFSI−-mobility, while the flexible PPP polymer reinforces the hybrid network and helps suppress lithium dendrite growth.

The researchers tested the electrolyte’s structure, thermal behavior, ionic transport, electrochemical stability and mechanical strength using various techniques. They then evaluated CSE-30 in Li|Li symmetric cells and LFP|Li full cells for cycling stability and rate capability, followed by post-cycling analysis. The electrolyte was also tested with an NCM622 cathode and in an LFP|Li pouch cell, including operation while folded and partially cut.

“The optimized CSE-30 achieved an impressive ionic conductivity of 5.60 × 10⁻³ S.cm⁻¹ at 60 C and a high lithium transference number of 0.81, accompanied by exceptional mechanical strength and elongation,” the results showed. “Symmetric Li|Li cells exhibited dendrite-free cycling for over 1,000 h, whereas full LiFePO₄|Li cells delivered a stable discharge capacity of 133.6 mAh g⁻¹ at 0.5C with 80% retention after 1000 cycles, underscoring both electrochemical durability and interfacial resilience.”

In addition, morphological and spectroscopic examinations revealed that CSE-30 fosters the formation of a conformal, chemically uniform SEI enriched with LiF and polymer-derived organic species, which ensure interfacial continuity and electrochemical stability.

“These results establish a robust structure–property correlation, wherein the synergistic interaction between a surface-engineered ceramic additive and a mechanically compliant polymer matrix yields a multifunctional electrolyte capable of sustaining high-performance LMBs,” the team concluded.

The research “Surface-Functionalized LLZO-Incorporated Multilayer Composite Solid Electrolytes for Dendrite Suppression and Efficient Ionic Conduction in Lithium–Metal Batteries” appeared in Advanced Materials.

Researchers from Chonnam National University and the Korea Institute of Industrial Technology have contributed to the study.