We report the synthesis and investigation of a novel redox-active poly(N,N′-diphenyl-p-phenylenediamine) (PDPPD) material obtained via the Buchwald–Hartwig C–N cross-coupling reaction. PDPPD has a high density of redox-active amine groups enabling a theoretical specific capacity of 209 mA h g⁻¹, which is much higher than that of all other materials of this family reported so far. The obtained polymer was evaluated as a cathode material for dual-ion batteries and it demonstrated promising operating voltages of 3.5–3.7 V and decent practical gravimetric capacities of 97, 94 and 63 mA h g⁻¹ in lithium, sodium and potassium half-cells, respectively, while being tested at a moderate current density of 1C. A specific capacity of 84 mA h g⁻¹ was obtained for ultrafast lithium batteries operating at 100C (full charge and discharge takes 36 seconds only), which is, to the best of our knowledge, the highest battery capacity reported so far for such high current densities. The PDPPD//Li batteries also showed promising stability reflected in 67% capacity retention after 5000 charge–discharge cycles.

A serious drawback of organic cathode materials for metal-ion and dual-ion batteries is the poor electronic conductivity of cathode materials leading to relatively low loading of active material in the electrode composite. Using excessive amounts of electrochemically non-active conductive fillers and polymeric binders approaching 40–60% of the total electrode weight makes organic cathodes non-competitive with respect to their inorganic counterparts, which operate efficiently with 3–4 times less ballast weight. In this work, we present non-doped polydiphenylamine (PDPA) as a highly promising positive electrode material for lithium and potassium based dual-ion batteries. In contrast to the vast majority of organic cathodes, the good intrinsic conductivity of PDPA allowed the spectacular increase of its loading in the cathode composites up to 80% thus reducing the ballast weight down to 20%, which brings the performance of organic materials closer to that of state-of-the-art inorganic cathodes. In particular, PDPA showed an impressive energy density of up to 523 W h kg⁻¹ for lithium- and up to 462 W h kg⁻¹ for potassium half-cells with an active material loading of 80%, which outperforms significantly the characteristics reached for previously reported polyaniline (PAni) and polytriphenylamine (PTPA) polymeric cathodes under the same conditions. Analysis of the literature data revealed that PDPA delivered record-high values of energy density recalculated for full cathode mass (418 W h kg⁻¹) among all organic polymer cathodes for dual-ion batteries reported so far.