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[Display omitted] • Multiwalled carbon nanotube@poly(quinone-thiourea) (MWCNT@PQTU) composite was fabricated. • A core–sheath nanostructure of MWCNT@PQTU was formed. • Ultrathin PQTU layers with 10–30 nm in thickness were tightly adhered onto MWCNT. • MWCNT@PQTU exhibited a discharge capacity of 120.6 mAh/g at 100 mA g−1. Quinone-based redox active polymers are regarded as the most suitable cathode materials for constructing high-energy aqueous zinc-ion battery (AZIB) because of adjustable structure, high capacity and excellent electrochemical reversibility. However, their Zn2+ storage performances are often limited by low electronic conductivity and sluggish ion diffusion of Zn2+. Herein, a novel inorganic–organic nanocomposite of multiwalled carbon nanotube@poly(quinone-thiourea) (MWCNT@PQTU) was successfully fabricated by the method of in-situ interfacial polymerization, wherein 1,4-quinone and thiourea were used as low cost polymer precursors and MWCNT as a conductive support. The π-π stacking interaction between poly(quinone-thiourea) (PQTU) and MWCNT drove the self-assembly of the polymer around MWCNT during the polymerization process, ensuring the formation of the core–sheath nanostructure with ultrathin PQTU layers (10–30 nm in thickness). The unique nanostructure of MWCNT@PQTUs could enhance electronic conductivity, increase active carbonyl (C O) groups for charge storage, promote the Zn2+ diffusion, buffer the volume variation and inhibit the dissolution of the PQTU polymer during the charge − discharge processes. Thanks to these effects, the MWCNT@PQTU cathode exhibited high discharge capacity (120.6 mAh g−1 at 100 mA g−1), excellent rate capability (64.1 mAh g−1 at 1 A g−1) and long cycling stability (81 % capacity retention after 2000 cycles at 500 mA g−1). This work demonstrated that the fabrication of core–sheath nanostructured CNT@polymer cathodes was an effective way to improve the charge storage performance of the quinone-based polymers for Zn-ion batteries. [ABSTRACT FROM AUTHOR]