Reversible construction of rigid-flexible layered-tunnel heterostructures endowing MnO2 cathode with robust zinc ion storage

MnO2 emerges as a promising cathode material for aqueous zinc-ion batteries (AZIBs) due to its high theoretical capacity and ideal working voltage. However, inherent limitations in low electrical conductivity and structural instability restrict its widespread application. Herein, we fabricated layered δ-MnO2 and introduced Cu and Ce metal ions for structural regulation, thus constructing a δ/α-MnO2 heterostructure within the δ-MnO2 matrix, forming a heterointerface that simultaneously enhances the electrical conductivity and structural stability of the material. In this system, Cu2+ acts as a catalyst, promoting the reduction of high-valent Mn to Mn2+ and enabling local two-electron transfer, which significantly increases the discharge specific capacity of MnO2. For Ce3+, it functions as a structural regulator, inducing the partial transformation of δ-MnO2 to α-MnO2 and forming the δ/α-MnO2 heterostructure. Further supported by density functional theory (DFT) calculations and in-situ characterization results, the heterointerface between α-MnO2 and δ-MnO2 generates an internal electric field due to the difference in Fermi levels. This not only effectively enhances the electron transfer capability but also significantly improves structural stability. Benefiting from these advantages, the Cu, Ce co-incorporated MnO2 (CCMO) cathode delivers a high discharge capacity of 455.4 mAh g−1 at 0.2 A g−1 and maintains 191.2 mAh g−1 specific capacity after 1500 cycles with 95% capacity retention at 2 A g−1, which is significantly better than non-doped MnO2. This strategy of structural regulation and heterostructure construction using guest ions offers a new approach for developing high-performance Mn-based cathode materials for AZIBs.