Background

The development of lithium metal batteries (LMBs) capable of operating under extreme conditions is of paramount importance for ensuring the reliable performance of energy storage systems in diverse environments, which is crucial for modern energy infrastructure. However, conventional liquid electrolyte-based LMBs suffer from inherent safety vulnerabilities and limited cycle life, mainly due to lithium dendrite growth and electrolyte leakage.¹ Although solid-state electrolytes offer enhanced safety features, their widespread application is hampered by suboptimal electrode-electrolyte interfacial compatibility and inadequate ionic conductivity.²

In contrast, gel polymer electrolytes (GPEs), which synergistically combine the mechanical stability of solid electrolytes with the ionic transport benefits of liquid systems, have emerged as a promising candidate for next-generation LMBs.³ Nevertheless, conventional GPEs still encounter significant challenges. These include impaired ionic transport kinetics and high desolvation energy barriers at subzero temperatures, as well as thermally induced parasitic reactions at elevated temperatures.⁴ Collectively, these issues severely limit their practical feasibility in extreme thermal environments.

Inspiration source

Natural organisms evolve remarkable biological topological configurations to adapt to their environments, providing profound inspiration for designing high-performance materials. For instance, water grasses enhance interactions with water by removing hydrophobic wax layers on their leaf surfaces, thereby enabling efficient nutrient absorption. Their short, brush-like leaves increase the contact area with water and exhibit rapid oscillatory motion to facilitate swift fluid transport.⁵ This system is analogous to gel electrolytes, where water corresponds to the liquid electrolyte component, and water grasses mirror the polymer framework.

Conventional gel polymer electrolytes (GPEs) primarily rely on liquid components to determine performance, with polymer skeletons serving merely as inert encapsulating matrices.^6,7 Inspired by the dynamic interactions between water and water grasses observed in aquatic systems, we pose a paradigm-shifting question: Can we achieve solvation structure modulation in gel electrolytes by strategically regulating the interactions between the polymer framework and the encapsulated liquid components?

Design Principle

The construction of weakly solvated electrolytes is widely recognized as pivotal for achieving extended temperature-range operation in batteries. Inspired by the structure-function integration of water grass, we engineered brush-like polymers with short side chains. This biomimetic design increases polymer-solvent interaction sites by mimicking the water grass morphology. Crucially, we developed Li⁺ solvation clusters emulating the dynamic water-water grass interactions, enabling the formation of unique dynamic non-bonding interactions with the short side chains of brush polymers (Fig. 1a). Specifically, poly(trifluoroethyl methacrylate) (PTFMA) was selected as the brush-like polymer framework, and ethyl 3,3,3-trifluoropropanoate (FEP) that has an asymmetric structure to the polymer side chain was used as the coupling agent. The double dipole coupling interactions between FEP and PTFMA drive FEP enrichment around the brush polymer, effectively weakening Li⁺-FEP interactions and successfully inducing weakly solvated structure formation (Fig. 1b). 

Results and Outlook

The weakly solvated gel polymer electrolyte (WSGPE) exhibits ionic conductivities of 4.40 × 10⁻⁴ S cm⁻¹ at room temperature and 1.03 × 10⁻⁴ S cm⁻¹ at −40 °C, with a Li⁺ transference number of 0.83 and an electrochemical stability window of 5.05 V (Fig. 1c). Remarkably, WSGPE shows fire resistance, thus ensuring the safety of high-voltage batteries (Fig. 1d). The electrolyte enables stable operation across an ultrawide temperature range (−30 to 80 °C), enabling the fabrication of a pouch cell with a specific energy of 490.8 Wh kg⁻¹. We believe this work offers a novel idea for developing high-performance GPEs for lithium metal batteries in extreme conditions.

More details of this study can be found in our recent article "Bioinspired Gel Polymer Electrolyte for Wide Temperature Lithium Metal Battery" published in Nature Communication.

Reference

1. Feng, Y. et al. Challenges and advances in wide-temperature rechargeable lithium batteries. Energy Environ. Sci. 15, 1711–1759 (2022).
2. Wang, H. et al. A novel hyperbranched polyurethane solid electrolyte for room temperature ultra-long cycling lithium-ion batteries. Energy Storage Mater. 66, 103188 (2024).
3. Gou, J. et al. An ultrahigh modulus gel electrolytes reforming the growing pattern of Li dendrites for interfacially stable lithium‐metal batteries. Adv. Mater. 36, 2309677 (2024).
4. Liu, Q. & Wang, L. Fundamentals of electrolyte design for wide‐temperature lithium metal batteries. Adv. Energy Mater. 13, 2301742 (2023).
5. Maberly, S. C. & Gontero, B. The Leaf: A Platform for Performing Photosynthesis. (Springer Cham, Switzerland, 2018).
6. Guo, C. et al. Multifunctional nitrile additives for inducing pseudo-concentration gel-polymer electrolyte: Enabling stable high-voltage lithium metal batteries. Energy Storage Mater. 71, 103683 (2024).
7. Huang, K. et al. Optimizing Li‐ion solvation in gel polymer electrolytes to stabilize Li‐metal anode. ChemSusChem 16, e202300671 (2023).