Trace rGO-Induced Self-Template Hydrothermal Synthesis of δ-MnO2/C Microspheres as Efficient Cathode for Quasi-Solid Zinc-Ion Batteries

Designing and preparation of MnO2 cathode materials with elevated conductivity, rapid Zn2+ insertion reaction kinetics, and good mechanical properties are significant strategies for gaining high-performance quasi-solid zinc-ion batteries (ZIBs), while the complex synergistic effect has not yet been achieved due to the lack of an effective route. Herein, δ-MnO2 conductive microspheres (C@MnO2-rGO) are designed and manufactured through a facile hydrothermal route by deploying manganese glycerate microspheres as the precursor and template and rGO as the conductive connector and the structural protection additive. The obtained C@MnO2-rGO manifests as the in situ growth of interconnected MnO2 nanosheets on the carbon matrix derived from manganese glycerate microspheres, furnishing a larger surface area and rich ion transport channels while efficaciously suppressing inter slice aggregation. The skeleton effect of the carbon matrix can lessen the volume change brought on by ion migration in the process of discharge–charge, thereby strengthening structural stability. Moreover, the introduction of trace amounts of rGO can maintain the microsphere structure and set up a collaborative electron transport network to boost the charge transfer process of the material. The optimized cathode exhibits a significant reversible capacity of 349 mAh g–1 following 120 circulations at 0.2 A g–1 and 259 mAh g–1 following 300 circulations at 0.5 A g–1. Even after 2000 circulations at 2 A g–1, the system maintains a capacity retention rate of 85%. The assembled quasi-solid ZIBs exhibit superior bending resistance and cycling performance, indicating its promising application potential.