Synthesis of Conductive Polymer Particles by Electroreductive Polymerization of Carbon Disulfide

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CS₂ is produced by the reaction of sulfur with carbon-based materials such as charcoal and methane, which are widely available and cost-effective. Consequently, utilizing CS₂ as a precursor for functional materials can promote the advancement of sustainable industries. For instance, electrically conductive poly(carbon sulfide)s (PCS) are synthesized via the polymerization of CS₂, and their potential application as cathode materials for Li-ion batteries has been explored. PCS films can be fabricated by gas-phase polymerization of CS₂ under UV or plasma irradiation. 1 However, these reactions are difficult due to the high flammability and toxicity of CS₂ gas. Alternatively, reduction polymerization of CS₂ in organic solvents has been reported as a more feasible approach compared to gas-phase polymerization. Nevertheless, this method requires an equimolar or greater amount of Na as a reductant. To develop a safer and easier polymerization of CS₂, we previously reported the electroreductive polymerization of CS₂ in acetonitrile solution, eliminating the need for hazardous reducing agents. 2 Moreover, the resulting PCS demonstrated potential as a cathode material for Li-ion batteries. However, PCS exhibits poor processability due to its insolubility and infusibility. To enhance its processability, we investigated the synthesis of PCS particles by electroreductive polymerization of CS₂ under stirring conditions (Scheme 1). Electroreductive polymerization was performed via constant current electrolysis at 50 mA cm⁻², 100 mA cm⁻², and 200 mA cm⁻², with stirring at 450 rpm in an acetonitrile solution containing 0.18 M Bu₄NBF₄, using a glass cell equipped with a water-cooling jacket. A platinum plate (1 × 1 cm²) and a platinum wire ( Φ = 0.5 mm) were used as the working and counter electrodes, respectively. After polymerization, PCS particles were deposited at the bottom of the cell and subsequently purified by centrifugation with methanol and water. The PCS particles were obtained as a brown solid with a yield of 14.5%. The particle size distribution estimated by laser diffraction (LD) measurement was narrower than that of PCS synthesized without stirring, and the particle size decreased as current density increased. This phenomenon is probably attributed to the rapid formation of multiple cores of polymer particles at higher current densities. In the optical microscope image of the aqueous dispersion of PCS particles, the particles prepared under stirring were smaller and more uniform than those synthesized without stirring. The resulting polymer particles exhibited electrical conductivity after doping by iodine. (1) R. K. Sadhir, K. F. Schoch, Chem . Mater . 1996 , 8 , 1281. (2) Y. Matsumura, B. Ochiai, Chem . Lett. 2021 , 50 , 1856. Figure 1

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