Binders are the unsung heroes of battery electrode fabrication—though they typically account for just 2–5 wt% of an electrode’s total mass, their impact on battery performance, stability, and scalability is profound. In battery laboratories, researchers rely on a diverse range of binders to address the unique challenges of emerging electrode materials (e.g., silicon, sulfur, sodium-based compounds) and next-generation battery chemistries (lithium-ion, sodium-ion, solid-state). These polymeric or biopolymeric materials serve three core functions: adhering active materials to current collectors, binding conductive additives into a interconnected network, and accommodating volume changes during charge-discharge cycles. This article explores the most widely used binders in battery labs, their working mechanisms, and how researchers tailor their selection to advance battery technology.

1. Polyvinylidene Fluoride (PVDF): The Traditional Workhorse

Polyvinylidene fluoride (PVDF) has long been the gold standard binder in lithium-ion battery (LIB) research, valued for its exceptional chemical stability and compatibility with organic electrolytes. Composed of repeating -CH₂-CF₂- units, PVDF’s hydrophobic nature and high crystallinity make it resistant to degradation by carbonate-based electrolytes (e.g., ethylene carbonate/diethyl carbonate mixtures) commonly used in LIBs.

2. Styrene-Butadiene Rubber/Carboxymethyl Cellulose (SBR/CMC): Aqueous Alternative for Anodes

The SBR/CMC composite binder has emerged as the leading aqueous alternative to PVDF, especially for anode research involving graphite or silicon-graphite blends. This water-based system combines the elasticity of styrene-butadiene rubber (SBR) with the mechanical strength of carboxymethyl cellulose (CMC), a cellulose derivative modified with carboxymethyl groups (-CH₂COOH) to enhance water solubility.

3. Polyacrylic Acid (PAA): Dynamic Binder for High-Volume-Expansion Materials

Polyacrylic acid (PAA)—a water-soluble polymer with repeating -CH₂-CH(COOH)- units—has become a staple in labs studying extreme volume-expansion materials like silicon, tin, or antimony. Unlike PVDF’s static covalent bonds, PAA forms dynamic hydrogen bonds between its carboxyl groups (-COOH) and hydroxyl groups (-OH) on active material surfaces (e.g., silicon oxide layers). These bonds can break and reform during charge-discharge cycles, accommodating volume changes without losing adhesion.

4. Polyimide (PI): High-Temperature Binder for Extreme Conditions

Polyimide (PI)—a high-performance polymer known for its thermal stability (decomposition temperature >400°C) and chemical inertness—is used in labs researching batteries for extreme environments (e.g., aerospace, industrial sensors) or high-temperature solid-state batteries (SSBs). PI’s rigid aromatic backbone and imide functional groups (-CO-NH-CO-) provide exceptional resistance to heat, organic electrolytes, and oxidative degradation.

PI is also used in high-voltage LIB cathodes (4.5V+) where traditional binders degrade. A 2025 study in Advanced Energy Materials showed that NMC 9010 cathodes with PI binders retained 92% capacity after 1,000 cycles at 4.6V, compared to 70% with PVDF, due to PI’s resistance to electrolyte oxidation. However, PI’s high cost (~$200/kg) and poor solubility in common solvents (requiring toxic dimethylacetamide) limit its use to specialized lab research, though efforts to develop water-soluble PI derivatives are ongoing.

5. Biobased Binders: Sustainable Options for Next-Gen Batteries

As labs prioritize sustainability, biobased binders derived from renewable resources (e.g., plants, algae) have gained traction. These include sodium alginate (from brown algae), chitosan (from crustacean shells), and lignin (from wood pulp)—all offering low cost, biodegradability, and aqueous processing.

Sodium alginate (SA) is a standout in SIB and LIB research. Its linear structure with guluronic acid and mannuronic acid units forms strong ionic crosslinks with metal ions (e.g., Na⁺, Ca²⁺), creating a flexible yet robust network. In SIB hard carbon anodes, SA binders outperform PVDF in cycle life (90% capacity retention after 1,000 cycles) and rate capability, as their ionic crosslinks enhance Na⁺ transport. Labs also use SA for sulfur cathodes in Li-S batteries, where its polar groups adsorb soluble polysulfides, mitigating the "shuttling effect" that causes capacity fade.

Chitosan, a cationic polysaccharide, is used in labs exploring zinc-ion batteries (ZIBs) due to its compatibility with aqueous electrolytes and ability to inhibit zinc dendrite growth. Its amino groups (-NH₂) form complexes with Zn²⁺, smoothing Zn deposition on anodes. Lignin, a byproduct of paper production, is being developed as a low-cost binder for LFP cathodes—though its low solubility requires modification (e.g., sulfonation) in lab settings to improve processability.

6. Binder Selection Criteria in Battery Labs

Researchers in battery labs select binders based on five key factors:

Material Compatibility: Binders must be stable with active materials (e.g., acid-resistant binders for silicon, oxidation-resistant for high-voltage cathodes) and electrolytes (aqueous vs. organic).

Volume Expansion Accommodation: High-flexibility binders (e.g., PAA, SBR/CMC) for materials like silicon; rigid binders (e.g., PVDF, PI) for low-expansion graphite or NMC.

Processing Requirements: Aqueous binders (SBR/CMC, PAA) for green manufacturing; organic-soluble binders (PVDF, PI) for specialized chemistries.

In battery laboratories, the choice of binder can make or break the success of new active materials or chemistries: PVDF sets the baseline for stability, SBR/CMC enables green anode research, PAA unlocks high-volume-expansion materials, PI addresses extreme conditions, and biobased binders pave the way for sustainable batteries. As researchers push toward higher energy density, longer cycle life, and greener manufacturing, binders will continue to evolve—with innovations like self-healing polymers, conductive binders, and multifunctional systems (e.g., binders that act as electrolyte reservoirs) on the horizon. For anyone working in battery R&D, understanding the nuances of different binders is essential to unlocking the full potential of advanced battery technologies.