62 To make a GO/rGO binder, GO is dispersed in water and coated onto the active anode particles, then chemically or thermally reduced to rGO, which wraps the particles in a web that provides excellent conductivity and mechanical strength along with the flexibility to accommodate silicon’s expansion. The downside of GO/rGO is a combination of high cost and complex processing, plus a high specific surface area that can lead to excessive SEI formation and consequent low first-cycle efficiency. When functionalised for dispersion, CNTs form a percolating conductive and adhesive network. Their main advantage is extremely high conductivity at low loadings, but they are expensive, dispersion stability is marginal and they are potentially toxic. Silicon–carbon anode At this point, examination of a leading developer’s highly innovative silicon– carbon composite anode material, and the selection of a suitable binder, is enlightening. Here, nanoscale amorphous silicon is grown inside a porous carbon matrix via (silane) gasphase infiltration to produce a material that combines the high capacity of silicon with the conductivity and structural stability of carbon. The particle architecture is roughly 1/3 silicon, 1/3 carbon, 1/3 void by volume. The internal void space is critical because it accommodates silicon’s expansion internally, preventing particle fracture and excessive electrode-level swelling. This makes it a more forgiving ‘drop-in’ material for existing battery manufacturing lines. It is also designed for flexibility, usable in blends with graphite (e.g., 5–10% replacement) or as a 100% silicon–carbon anode. While the roles played by the binder in this composite anode material are common to all binders for silicon anodes, the developer stresses that there is no ‘one-size-fits-all’ solution, and that the optimal binder depends on the specific battery application and how it ranks high-power, long-life automotive, and cold-weather operation, for example. The company also emphasises that the binder formulation must suit the proportion of silicon in the anode. Graphite-dominated low-silicon blends can use more traditional binders such as SBR/SMC, while highsilicon (even 100%) anodes require specialised binders such as polyimidebased materials with higher mechanical strength and thermal stability. Also, close collaboration between the anode developer and the binder supplier is crucial to understanding how binder chemistry interacts with the silicon– carbon surface to ensure commercial success. The company’s particular silicon–carbon composite anode works with SBR/CMC, PAA, PEI, and other specialty binders, but the selection is purpose-driven. Cathode hurdles Cathodes present conductive binders with a much harsher environment than do anodes because the higher potentials encountered (4.3 V and above) cause high-voltage oxidative stress, so stability under these conditions is essential. The main categories of materials under investigation for cathode use are: oxidatively stable conductive polymers (OCPs), conjugated coordination polymers / metal–organic frameworks (CCP/MOFs), ion–electron mixed conductors (IEMCs) and cathode binders with ‘electronic wiring’. The first example of an OCP binder material is poly (9,9-dioctylfluoreneco-fluorenone-co-methylbenzoic ester). Thankfully abbreviated to PFM, this is a fluorene-based polymer designed specifically for cathode use. Its conjugated backbone is engineered to withstand high oxidation potentials of 4.5 V and above. PFM significantly boosts the rate capability of LFP and NMC cathodes in research. Additionally, polymers with rigid, ladder-like backbones, such as polybenzimidazoles, are exceptionally stable both thermally and electrochemically, but conductivity is often lower and processing is difficult. The second category – the CCP/MOF materials – have intrinsic porosity to ease ion transport and, if designed with conjugated linkers, can maintain useful electronic conductivity. Now in the early stages of r&d, much work has to be done to solve cost and complexity challenges, and to ensure stability in the electrolyte environment. Testing for electrolyte capability involves chemical screening, thermal analysis, electrochemical cycling and post-mortem studies to prevent side reactions with new electrolyte chemistries. Natural polymers Another line of binder development focused primarily on sustainably sourced silicon anodes is that of ‘natural’ polymers. Substances such as seaweed-derived alginate and chitosan, derived from crustacean shells, are promising because they are rich in functional groups (carboxyl in alginate, amine in chitosan) that form strong, multivalent hydrogen bonds with silicon particles, effectively accommodating volume expansion and improving cycle life. These are relatively inexpensive, renewable, enable aqueous processing and are easier to recycle. They present significant barriers Product focus | Battery electrode binders January/February 2026 | E-Mobility Engineering Group14’s SCC55 silicon–carbon composite anode material is created by growing nanoscale amorphous silicon inside a porous carbon matrix, leaving voids to accommodate silicon’s expansion (Image: Group14)
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