Prof. Dr. Jean-Francois Gohy

Novel Approaches Towards Polymer-Based Electrolytes

Compared to conventional liquid electrolytes, polymer-based solid and quasi-solid-state electrolytes (e.g., ionogel) exhibit enhanced safety and broader electrochemical stability windows, enabling compatibility with high-voltage cathodes. While their improved mechanical robustness (compared with liquid electrolyte) is often highlighted, the lithium-ion transport mechanism in these systems—polymer segmental dominated motion—imposes an inherent trade-off between ionic conductivity and mechanical strength. To overcome this compromise, it is necessary to develop an ionic transport mechanism where lithium ions migrate independently of the host polymer chain dynamics. Its realization demands a focus shift in materials design from conventional polymer chains mobility to other environment engineering or transport pathways. Crucially, if such a mechanism becomes the dominant transport mode, it may decouple ion migration from polymer chain dynamics—fundamentally shifting the prevailing paradigm. This would open a pathway toward materials that simultaneously exhibit high ionic conductivity and mechanical strength.

One possibility relies on the so-called competitive coordination principle, creating an environment in which lithium ions are shared between multiple ligands with similar binding energy. In polymer-based ionogels, this can be achieved by combining polymer networks with ionic liquids. Lithium ions in such systems do not form strong coordination with any single ligand, resulting in reduced average binding energies and enhanced ion lability.  Although competitive coordination has been widely explored in liquid electrolyte systems, its application in solid and quasi-solid polymer electrolytes remains in its infancy. Herein, we design a crosslinked polyrotaxane network and then introduce ionic liquid and a lithium salt to obtain an ionogel electrolyte based on the principle of competitive coordination with the lowest binding energy for lithium ions coordinated with both the polymer network and ionic liquid clusters. This facilitates their migration within the ionogel and their release from the coordination environment, thereby improving lithium-ion transport efficiency (ionic conductivity of 2.2×10⁻³ S cm⁻¹ and t_Li⁺=0.45 at 20 °C).¹

Another possibility lies in the use of liquid crystalline block copolymer electrolytes (BCPE) with a liquid crystal and a lithium-ion conductive phase. Herein, we synthesize a lithium salt loaded poly(10-[(4-cyano-4’-biphenyl)oxy] decatyl methacrylate)-block-(methoxy-poly(ethylene glycol) methacrylate-co-glycidyl methacrylate) [P(MALC)-b-P(PEGMA-co-GM)] BCPE by reversible addition-fragmentation transfer polymerization. Formation of a smectic A mesophase in a broad temperature range was confirmed for those samples with or without added lithium salt. A setup was developed to drop-cast BCPE solutions into a homogeneous E_F (AC or DC) under controlled conditions. Self-standing films were obtained and employed for further electrochemical and morphological analysis. Samples subjected to E_F consistently exhibited enhanced ionic conductivity, reaching values up to 4.7·10^-5 S·cm­^-1 at 60° C, compared to 6.0·10^-6 S·cm­^-1 at the same temperature for the polymer electrolyte casted without E_F. Hierarchical morphologies at two nanoscales were identified across a broad range of examined BCPE compositions. In all recognized microstructures, the discrete smectic A layers exhibited a perpendicular orientation with respect to the BCPE. The observed increase in ionic conductivity is attributed to the stronger phase separation and longer-range order achieved through E_F directed self-assembly, that further allow the creation of efficient lithium-ion transport pathways between the different microphases of the BCPE.²

1. Yan, Shanshan, Liu, Jinjia, He, Zhenni, Jia, He, Chen, Zehan, Zhang, Yinghui & Gohy, Jean-François (2025). High‐Performance Ionogels from Dynamic Polyrotaxane‐Based Networks. Angewandte Chemie International Edition, 64, e202503307. doi :10.1002/anie.202503307
2. Álvarez Moisés, Isaac, Król, Monika, Keus, Garance, He, Zhenni, Innocenti, Alessandro, Passerini, Stefano, Ruokolainen, Janne, Gohy, Jean-François (2025). Enhancement of Lithium-Ion Conductivity in Liquid Crystalline Block Copolymer Electrolyte by Electric Field Alignment. Journal of the American Chemical society, 147, 20347–20358. doi : 10.1021/jacs.5c00278.