Lignocellulose‑mediated gel polymer electrolytes toward next‑generation energy storage

As global energy demands surge and environmental concerns intensify, the quest for safe, high-performance, and sustainable energy storage devices has become urgent. Traditional liquid electrolytes—widely used in lithium-ion batteries, supercapacitors, and zinc-ion batteries—suffer from leakage, flammability, and dendrite growth, limiting device reliability and safety. Now, a team led by Prof. Liyu Zhu, Prof. Ting Xu, Prof. Kun Liu, and Prof. Chuanling Si from Tianjin University of Science and Technology has published a comprehensive review on lignocellulose-mediated gel polymer electrolytes (L-GPEs), offering a bio-based, scalable, and high-performance alternative for next-generation energy storage systems.

Why Lignocellulose-Based Gel Electrolytes Matter

• Sustainability: Lignocellulose—composed of cellulose, hemicellulose, and lignin—is the most abundant renewable biomass on Earth. It offers a carbon-neutral, low-cost, and biodegradable platform for electrolyte design.
• Safety & Stability: L-GPEs eliminate leakage and flammability risks associated with liquid electrolytes. Their 3D crosslinked network suppresses dendrite growth and enhances thermal stability (>320 °C).
• Performance: With tunable porous structures, high ionic conductivity (up to 38.6 mS cm^-1), and excellent mechanical strength (>40 MPa), L-GPEs outperform conventional synthetic polymer electrolytes in lithium, sodium, zinc, and supercapacitor systems.

Innovative Design Strategies

• Material Engineering:
  • Cellulose provides rigid mechanical support and ion transport channels.
  • Hemicellulose enhances electrolyte uptake and ion mobility via hydrophilic branching.
  • Lignin improves thermal stability and electrochemical stability through aromatic radical-scavenging and hydrophobic shielding.
• Structural Optimization:
  • Nanofiber Networks: Cellulose nanofibers (CNFs) and nanocrystals (CNCs) form low-tortuosity ion pathways.
  • Crosslinking & Blending: Chemical crosslinking (e.g., epichlorohydrin) and polymer blending (e.g., PVA, alginate) enhance flexibility and toughness.
  • Inorganic Fillers: Boron nitride (BN) and SiO₂ nanofibers boost thermal stability and ionic conductivity via Lewis acid-base interactions.
• Interface Engineering:
  • Coating: PVDF-HFP/cellulose composite coatings reduce interfacial resistance (194.5 Ω) and suppress lithium dendrites.
  • In-Situ Polymerization: Direct gelation on electrodes ensures seamless contact and stable SEI formation.

Applications & Performance Highlights

• Supercapacitors: L-GPEs achieve 97.5% capacitance retention over 2,000 bending cycles and 10,000 charge/discharge cycles.
• Lithium-Ion Batteries: L-GPEs enable 98% capacity retention after 300 cycles at 1C and high Li⁺ transference numbers (0.88–0.902).
• Sodium-Ion Batteries: Vertical-aligned cellulose channels reduce Na⁺ migration resistance, delivering 89.8% capacity retention after 200 cycles.
• Zinc-Ion Batteries: Lignin-modified hydrogels suppress dendrites and extend cycle life by 175% at 2,000 mA g^-1.
• Solar Cells: L-GPEs replace volatile liquid electrolytes in dye-sensitized solar cells (DSSCs), maintaining 67.2% efficiency after 6 days.

Challenges & Future Outlook

The review identifies key bottlenecks:

• Scalability: Green pretreatment and cost-effective synthesis routes are needed.
• Interface Chemistry: Balancing covalent crosslinking (mechanical strength) and dynamic bonds (self-healing) remains critical.
• Advanced Characterization: In-situ EIS, cryo-TEM, and multi-scale simulations are essential to decode ion transport and interfacial reactions.

This roadmap underscores the transformative potential of lignocellulose in energy storage. By merging materials science, electrochemistry, and sustainability, L-GPEs are poised to power a safer, greener, and more resilient energy future. Stay tuned for more breakthroughs from the Tianjin team!