The development of bio-inspired materials has opened new pathways for improving battery technology, particularly in the design of adhesive binders for electrodes. Among these, mussel-inspired adhesive binders have gained attention due to their unique combination of wet-adhesion, mechanical flexibility, and environmental compatibility. These binders draw inspiration from the adhesive proteins secreted by mussels, specifically the byssal threads that allow them to cling to surfaces in turbulent aquatic environments. The key component enabling this behavior is dopamine, a molecule that mimics the catechol and amine functional groups found in mussel foot proteins. When polymerized, dopamine forms polydopamine, a versatile adhesive material that can enhance electrode cohesion while accommodating mechanical stress.

Mussel foot proteins contain high concentrations of L-3,4-dihydroxyphenylalanine (DOPA), which is responsible for their strong interfacial adhesion. Similarly, dopamine-based polymers replicate this chemistry through catechol groups that form robust bonds with various substrates, including metals and metal oxides commonly used in battery electrodes. The wet-adhesion property is particularly valuable for aqueous battery systems, where conventional binders often fail due to poor stability in water. Polydopamine-based binders maintain adhesion even in submerged conditions, making them suitable for use in water-based electrolytes or flexible batteries exposed to humid environments. This characteristic also benefits stretchable batteries, where the binder must endure repeated deformation without delaminating from active materials or current collectors.

In comparison to traditional binders such as polyvinylidene fluoride (PVDF) or carboxymethyl cellulose (CMC), mussel-inspired binders offer several advantages. PVDF, while widely used, requires toxic organic solvents like N-methyl-2-pyrrolidone (NMP) for processing and lacks strong adhesion in wet conditions. CMC, though water-soluble, has limited mechanical resilience under strain. Dopamine-based polymers, on the other hand, exhibit superior binding strength in both dry and wet states while being processable in aqueous environments. This eliminates the need for hazardous solvents, reducing environmental and health risks during manufacturing. Additionally, the inherent flexibility of polydopamine helps accommodate volume changes in high-capacity electrode materials like silicon anodes, which undergo significant expansion during lithiation.

The environmental benefits of mussel-inspired binders extend beyond solvent-free processing. Many conventional binders are derived from petrochemical sources, whereas dopamine can be synthesized from biologically derived precursors, offering a more sustainable alternative. Furthermore, polydopamine’s adhesive properties reduce the need for additional conductive additives or surface treatments, simplifying electrode fabrication and lowering material costs. However, one challenge with these binders is their relatively low intrinsic conductivity. While they improve mechanical integrity, the insulating nature of polydopamine can impede electron transport within the electrode. Researchers have addressed this by incorporating conductive fillers such as carbon nanotubes or graphene, or by designing hybrid polymers with conductive backbones.

Applications of mussel-inspired binders are particularly promising in emerging battery formats. Stretchable and wearable electronics require electrodes that can bend and twist without cracking or losing electrical contact. The self-healing properties of some dopamine-based polymers further enhance durability in these systems. In aqueous batteries, where water acts as the electrolyte, the binder’s resistance to dissolution and delamination ensures long-term stability. These binders have also been explored for use in bio-integrated devices, where biocompatibility and adhesion to biological tissues are essential.

Despite their advantages, challenges remain in optimizing mussel-inspired binders for large-scale production. The polymerization of dopamine must be carefully controlled to achieve consistent adhesive properties and avoid excessive cross-linking, which could reduce flexibility. Long-term stability under electrochemical cycling is another area requiring further study, as repeated charge-discharge processes may degrade the binder over time. Additionally, while the environmental footprint of these materials is lower than that of conventional binders, the synthesis of dopamine derivatives still involves energy-intensive steps that could be improved.

In summary, mussel-inspired adhesive binders represent a significant advancement in electrode material design, combining bio-inspired adhesion with environmental and mechanical benefits. Their ability to function in wet and flexible environments makes them particularly suited for next-generation batteries, from stretchable electronics to aqueous energy storage systems. While conductivity limitations and processing challenges persist, ongoing research into hybrid materials and optimized polymer structures continues to expand their potential. As battery technology evolves toward more sustainable and adaptable forms, dopamine-based binders are poised to play a critical role in enabling these innovations.