Improving the Capacity Retention of Poly(vinylphenothiazine) as Battery Electrode Material by Pore Size Engineering of Porous N‐Doped Carbon Nanospheres as Conductive Additive

Abstract The increasing demand for batteries in mobile devices, electromobility, and stationary storage requires the development of new battery materials. The organic redox‐active polymer poly(vinyl‐ N ‐methylphenothiazine) (PVMPT) shows a fast and reversible electrochemical reaction at a potential of 3.5 V versus Li|Li + and is a p ‐type electrode material. Due to the solubility of the oxidized form of PVMPT in many liquid electrolytes, strategies are needed to reduce the solubility and improve active material retention. Previous approaches focuses on adapting the electrolyte or polymer structure. A third strategy relates to the immobilization of PVMPT in the intra‐ and interparticle porosity generated by conductive carbon additives during electrode design. In a previous study, it is shown that the conductive carbon particle size has a major impact on the battery performance and can alter the electrode behavior between high accessible specific capacity and high rate capability and specific capacity retention. Here, an advanced approach is reported, in which N ‐doped (meso)porous carbon (MPNC) nanospheres with tailored intraparticle porosity and constant particle size are applied, whereby the entire volume of the carbon particles can be used for the immobilization of PVMPT. This allows reaching high specific capacities while maintaining good rate capability and high specific capacity retention.