Current collectors are critical components in battery electrodes, serving as conductive substrates that facilitate electron transfer between active materials and external circuits. Traditional current collectors rely on metal foils, such as copper for anodes and aluminum for cathodes, due to their high electrical conductivity and mechanical stability. However, metal foils present limitations, including weight, rigidity, and susceptibility to corrosion, which hinder their suitability for next-generation flexible, lightweight, or highly durable battery systems. Conductive polymers have emerged as promising alternatives, offering unique advantages in specific applications where metals fall short. Among these, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and polyaniline (PANI) are the most studied due to their tunable conductivity, flexibility, and corrosion resistance.

Conductive polymers like PEDOT:PSS and PANI exhibit intrinsic electrical conductivity through conjugated electron systems along their polymer backbones. PEDOT:PSS, a water-dispersible polymer complex, achieves conductivity through the interaction between PEDOT’s conjugated chains and PSS’s dopant properties. Its conductivity can range from 1 to over 1,000 S/cm depending on formulation and post-treatment, such as solvent annealing or additive incorporation. Polyaniline, in its doped emeraldine salt form, demonstrates conductivity between 1 and 100 S/cm, influenced by protonation levels and processing methods. While these values remain lower than those of metals (copper: ~5.8×10^5 S/cm; aluminum: ~3.5×10^5 S/cm), conductive polymers compensate with other properties.

Flexibility is a standout advantage of polymer-based current collectors. Unlike metal foils, which can fracture under repeated bending, conductive polymers maintain structural integrity even under mechanical strain. This makes them ideal for flexible or wearable electronics, where electrodes must endure deformation without performance degradation. Additionally, polymers are inherently lightweight, reducing the overall mass of the battery—a critical factor for portable and aerospace applications. Corrosion resistance is another key benefit. Metals like aluminum and copper are prone to oxidation or dissolution in certain electrolytes, particularly under high voltages or extreme temperatures. Conductive polymers, however, demonstrate superior stability in acidic, alkaline, and even aqueous environments, extending battery lifespan in harsh conditions.

Despite these advantages, conductive polymers face challenges that limit their widespread adoption. The primary drawback is their lower conductivity compared to metals, which can increase internal resistance and reduce power output in high-current applications. Durability is another concern; while polymers resist corrosion, their long-term mechanical and electrochemical stability under cycling conditions remains inferior to metals. Repeated charge-discharge cycles can lead to delamination or cracking of polymer films, especially when paired with high-loading active materials. Furthermore, processing conductive polymers into thin, uniform films with consistent properties is more complex than handling metal foils, often requiring specialized coating or printing techniques.

Hybrid designs combining conductive polymers with metal grids or nanostructures have been explored to mitigate these limitations. In such systems, a metal grid provides a high-conductivity pathway for electrons, while the polymer matrix ensures flexibility and corrosion protection. For example, embedding a silver nanowire network within a PEDOT:PSS film can yield a composite with conductivity exceeding 10,000 S/cm, approaching that of pure metals, while retaining bendability. Similarly, coating a thin copper mesh with PANI can prevent oxidation of the metal while maintaining low sheet resistance. These hybrids balance the strengths of both materials, though they introduce additional complexity in manufacturing and may not fully eliminate metal-related issues like weight or cost.

The electrochemical performance of polymer-based current collectors has been evaluated in various battery systems. In lithium-ion batteries, PEDOT:PSS collectors have demonstrated stable operation at moderate current densities, with minimal polarization losses compared to metal foils. Their compatibility with both organic and aqueous electrolytes reduces the risk of side reactions, enhancing cycle life. Polyaniline collectors, meanwhile, have shown promise in supercapacitors and zinc-based batteries, where their redox activity can contribute additional pseudocapacitance. However, under high-load conditions or extended cycling, polymer collectors often exhibit higher resistance growth than metals, limiting their use in power-intensive applications.

Environmental and cost considerations further influence the viability of polymer current collectors. Conductive polymers are generally less resource-intensive to produce than metals, with lower energy requirements for synthesis and processing. They also avoid the geopolitical and ethical concerns associated with mining metals like cobalt or copper. However, the raw materials for PEDOT:PSS and PANI are derived from petrochemicals, raising sustainability questions. Advances in bio-based or recyclable conductive polymers could address this issue in the future.

In summary, conductive polymer-based current collectors offer a compelling alternative to metal foils in applications prioritizing flexibility, weight reduction, or corrosion resistance. PEDOT:PSS and polyaniline are the leading candidates, though their lower conductivity and durability necessitate careful design considerations. Hybrid systems incorporating metal grids provide a middle ground, enhancing performance without sacrificing all the benefits of polymers. While challenges remain in scalability and long-term reliability, ongoing research into material formulations and processing techniques continues to narrow the gap between polymers and traditional metal collectors. As battery technology evolves toward diverse form factors and operating conditions, conductive polymers are poised to play an increasingly important role in enabling innovative energy storage solutions.