65 – and within composite electrodes and electrolytes. HM-PIB provides excellent adhesion, ensuring strong bonding between battery components and enhancing structural integrity. It also has a unique cold flow property that allows it to bridge gaps between particles, promoting efficient ion transport and connectivity within the solid-state matrix. These materials also offer superior elasticity and elongation, enabling them to accommodate electrode expansion and contraction, thereby reducing the risk of physical damage or premature failure. As HM-PIB materials undergo evaluation for use in next-generation SSBs, the focus will be on optimising properties like flexibility at low temperatures, chemical inertness and the ability to act as a bridge at the solid– solid interface, all of which are essential for this application. Making binders smart Smart binders represent the frontier of battery materials science, moving from passive components to dynamic, responsive systems. The most researched type are selfhealing binders, designed to repair the microcracks that form in electrodes owing to volume changes (in silicon anodes, for example) autonomously. They achieve this through reversible chemistry, which involves dynamic covalent bonds (such as boronic esters) or supramolecular interactions (such as hydrogen-bond networks) that can break under stress and reform afterwards, effectively ‘healing’ the electrode structure. A seminal example is a self-healing binder network constructed from PAA dynamically cross-linked via urea-functionalised linkers. The urea groups form dimers through quadruple hydrogen bonds, which provide strong mechanical cohesion but are sufficiently reversible to break and reform under mechanical stress. In laboratory tests with silicon nanoparticle anodes, electrodes employing this binder maintained structural and electrical integrity for hundreds of cycles. In stark contrast, conventional electrodes using a PVDF binder typically fail owing to irreversible cracking within a few tens of cycles. Other smart concepts include polymers that respond to stimuli, for example changing conductivity or adhesion with temperature or voltage. Thermoresponsive block copolymer binders represent a class of smart materials designed to adapt electrode properties to operating temperature, for example. These copolymers typically combine a rigid structural block (such as polyimide) with a soft block exhibiting a Lower Critical Solution Temperature (LCST), such as poly(ethylene oxide) (PEO). Below the LCST, the PEO blocks are hydrophilic and swell with electrolyte, promoting ionic transport. Upon heating during high-power operation (to 50–70 C, for example), the PEO blocks undergo a sharp phase transition, becoming hydrophobic and collapsing. This collapse induces two critical effects: first, it mechanically contracts the polymer network, pulling active material particles closer together to reduce interparticle electronic resistance; second, it vacates volume previously occupied by swollen polymer chains, generating additional nanoporosity for improved ionic transport – just when needed most. In this way, the binder dynamically reconfigures the electrode’s tortuosity and contact network, optimising it for prevailing conditions – effectively providing intrinsic, materiallevel thermal management. Currently, smart binders remain in advanced academic and early-stage r&d, with impressive lab-scale results but unproven scalability. The most significant hurdles in scaling-up include monomer purity, batch consistency and low yields at scale. Although binders are a small part of battery cost (at around 1%), scaling new materials requires proven performance and consistency to justify adoption. Binder selection can no longer be treated as an afterthought because it is a fundamental design choice that co-optimises cell performance, manufacturability and cost. The evolution of binder technology will continue to be a critical, if unseen, enabler of better EV performance. Acknowledgements The author would like to thank the following for their help with this article: Thorsten Schoeppe (Technical Sales) and Dr. Michael Koch (Global Marketing) at BASF; Rick Costantino, founder and CTO of Group14 Technologies; and Anne Risse at Synthomer. E-Mobility Engineering | January/February 2026 Battery electrode binders | Product focus Mercedes-Benz has begun road testing of its EQS electric saloon with a solid-state battery; a technology that requires binders to act as functional components of composite electrolytes (Image: Mercedes-Benz)
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