Electrophoretic deposition has emerged as a promising technique for fabricating porous electrodes, particularly for advanced battery systems such as lithium-sulfur and lithium-air batteries. The method leverages electric fields to drive charged particles in a colloidal suspension toward a substrate, forming a dense or porous coating depending on process parameters. Unlike templated or foamed electrode synthesis, EPD offers precise control over electrode architecture without requiring sacrificial templates or complex foaming agents. The technique’s effectiveness hinges on three critical factors: zeta potential control, suspension stability, and the use of pore-forming additives.

Zeta potential plays a central role in determining the success of electrophoretic deposition. It represents the electrokinetic potential at the slipping plane of particles in a colloidal suspension and dictates particle mobility under an applied electric field. For stable EPD, particles must possess sufficient surface charge to remain dispersed and migrate uniformly. In aqueous systems, a zeta potential magnitude exceeding 30 mV typically ensures colloidal stability, preventing agglomeration during deposition. For non-aqueous suspensions, common in battery applications due to moisture sensitivity, achieving adequate zeta potential requires careful selection of dispersants and charging agents. Polymeric stabilizers such as polyvinylpyrrolidone or polyethyleneimine can adsorb onto particle surfaces, providing steric and electrostatic stabilization. The pH of the suspension also significantly influences zeta potential, particularly for oxide materials, necessitating tight control during processing.

Suspension stability represents another critical parameter for producing high-quality porous electrodes through EPD. The colloidal system must maintain homogeneity throughout the deposition process to ensure uniform coating thickness and composition. Sedimentation or flocculation during deposition leads to inhomogeneous electrode structures with poor mechanical integrity and inconsistent electrochemical performance. Achieving stable suspensions often requires optimizing solvent choice, solid loading, and additive concentrations. Ethanol, isopropanol, and acetone serve as common solvents for battery material EPD due to their moderate dielectric constants and low moisture content. Solid loading typically ranges between 0.1 and 5 weight percent, balancing deposition rate with suspension stability. Ultrasonication and ball milling prove effective for breaking up agglomerates and promoting particle dispersion prior to deposition.

Pore-forming additives introduce controlled porosity into electrodes fabricated via electrophoretic deposition, a crucial feature for lithium-sulfur and lithium-air battery applications. These batteries benefit from porous architectures that accommodate volume changes during cycling and facilitate electrolyte infiltration. Unlike templated approaches that rely on pre-formed structures, EPD incorporates pore formers directly into the deposited layer. Subsequent thermal or chemical treatment removes these additives, leaving behind interconnected pore networks. Common pore formers include ammonium carbonate, poly(methyl methacrylate) microspheres, or citric acid, which decompose or dissolve post-deposition. The size distribution and loading of these additives directly influence the resulting pore structure, with typical loadings ranging from 10 to 40 volume percent. Higher loadings increase porosity but may compromise mechanical strength, requiring careful optimization.

In lithium-sulfur battery applications, EPD enables fabrication of porous carbon-sulfur composite cathodes with uniform sulfur distribution. The process can sequentially deposit carbon matrices followed by sulfur infiltration or co-deposit premixed composites. Porous architectures help mitigate polysulfide shuttle by physically trapping soluble intermediates while maintaining electronic conductivity. The open pore structure also accommodates sulfur’s substantial volume expansion during lithiation. For lithium-air batteries, EPD produces porous oxygen electrodes with tailored triple-phase boundaries essential for oxygen reduction and evolution reactions. The technique’s ability to control pore size distribution proves particularly valuable for optimizing oxygen diffusion pathways while maintaining sufficient catalyst loading.

Process parameters such as applied voltage, deposition time, and electrode spacing significantly influence the morphology and properties of EPD-produced porous electrodes. Typical voltages range from 1 to 100 V/cm, with higher fields increasing deposition rates but potentially causing uneven particle accumulation. Deposition times vary from seconds to minutes, allowing precise control over coating thickness. The substrate’s conductivity and surface chemistry also affect film quality, with pretreatments like plasma cleaning often improving adhesion. Post-deposition drying and sintering steps finalize the electrode structure, removing residual solvents and strengthening particle bonds without collapsing the porous network.

The advantages of EPD for porous electrode fabrication include room-temperature processing, compatibility with complex geometries, and scalability. The technique can coat irregularly shaped substrates and produce graded compositions by modifying suspension composition during deposition. Compared to conventional slurry casting, EPD eliminates the need for binders in many cases, reducing inactive material content. The method also enables multilayer deposition of different materials, potentially useful for functional gradient electrodes in lithium-sulfur systems where composition varies from current collector to electrolyte interface.

Challenges remain in applying EPD to commercial battery production, particularly regarding large-area uniformity and reproducibility. Suspension composition must remain constant throughout deposition to ensure consistent electrode properties across batches. Scaling up requires addressing edge effects and field distribution inhomogeneities that become pronounced in larger cells. Despite these challenges, the technique’s versatility and ability to create tailored porous structures make it a compelling option for next-generation battery electrodes where conventional methods fall short.

For lithium-sulfur batteries specifically, EPD offers a pathway to overcome cathode challenges through controlled porosity at multiple length scales. Macropores facilitate electrolyte transport while mesopores provide high surface area for sulfur loading and micropores help confine polysulfides. The technique’s ability to co-deposit conductive additives and catalyst materials alongside sulfur hosts presents opportunities for integrated electrode design. Similarly, in lithium-air batteries, EPD can construct hierarchical porous networks that optimize oxygen diffusion, electrolyte wetting, and discharge product accommodation simultaneously.

Future developments in EPD for porous battery electrodes will likely focus on expanding material compatibility and improving process control. Advanced suspension formulations that maintain stability for multicomponent systems could enable more complex electrode architectures. In-situ monitoring techniques may provide better control over deposition uniformity and porosity distribution. Combining EPD with other fabrication methods could yield hybrid processes that leverage the strengths of multiple techniques while mitigating their individual limitations.

The environmental benefits of EPD also warrant consideration, as the technique typically uses less solvent than conventional slurry methods and can operate without toxic binders. Water-based EPD systems, when compatible with moisture-sensitive materials, could further improve sustainability. As battery technologies evolve toward more sophisticated electrode designs, electrophoretic deposition stands poised to play an increasingly important role in enabling high-performance porous architectures for energy storage applications.