Biomass‐Based Bicomponent Hydrogel With High Strength and Self‐Healing Ability for Safety Quasi‐Solid‐State Electrolytes

Biomass materials with low cost, renewability, and biodegradability are important in the development of batteries. In this study, lignin and carboxymethyl cellulose (CMC) are used as raw materials to prepare a dual‐crosslinking hydrogel electrolyte with high strength and self‐healing abilities. Hydrogen‐bond crosslinking is formed between hydroxyl groups in lignin and CMC through the freeze–thawing method. By adding multivalent ions (Ca 2+ and Fe 3+ ), synergistic ionic coordination is formed through the strong chelating ability of phenolic hydroxyl groups in lignin and carboxymethyl groups in CMC. The mechanical strength of lignin/CMC‐Ca 2+ /Fe 3+ hydrogel increased by 52.6% and 60.0% compared with the lignin/CMC‐Fe 3+ and lignin/CMC‐Ca 2+ hydrogel, respectively. The ionic conductivity also increased by 61.6% and 58.3%, respectively. This bio‐based hydrogel electrolyte can be completely degraded by soil within 21 days, and the capacitance retention rate remains 92.5% after five cuttings, showing good soil‐degradation abilities and strong self‐healing abilities.