Introducing Oxygen Defects into Phosphate Ions Intercalated Manganese Dioxide/Vertical Multilayer Graphene Arrays to Boost Flexible Zinc Ion Storage

Designed and fabricated flexible high-performance MnO₂ cathode materials are highly desirable for developing advanced rechargeable Zn–MnO₂ batteries. In this work, a facile phosphorization process is reported for introducing oxygen defects into phosphate ions intercalated manganese dioxide/vertical multilayer graphene (VMG) arrays, forming an integrated P-MnO_2-x @VMG cathode. The oxygen defects and phosphate ions intercalation are achieved simultaneously via phosphorization. The former can increase the electrical conductivity of MnO₂, while the latter is able to expand its interlayer spacing accelerating ion transfer. Furthermore, flexible VMG conductive networks provide excellent peripheral charge transfer and endow the cathode with favorable mechanical strength. Benefiting from these virtues, the obtained P-MnO_2-x @VMG cathode demonstrates high capacity (302.8 mAh g⁻¹ at 0.5 A g⁻¹) and long-term cycling stability (>90% capacity retention after 1000 cycles at 2.0 A g⁻¹) in aqueous electrolytes. More impressively, the P-MnO_2-x @VMG cathode exhibits a high energy density of 369.5 Wh kg⁻¹ in quasi-solid-state flexible devices (P-MnO_2-x @VMG//Zn@VMG), and thereby shows great prospects for applications in wearable electronics. This work demonstrates a new synergistic way to construct high-performance electrodes for energy storage toward divalent metal ions.