Heterostructured Manganese-Based Cathode with Atomic Interlocking for Advanced Sodium-Ion Batteries

Abstract

Although manganese-rich layered oxides are promising as low-cost, high-capacity cathodes for sodium-ion batteries, their single-phase design suffers from structural degradation due to unfavorable phase transitions and lattice strain accumulation caused by inherent defects. To address this issue, we propose a functionally oriented multi-element doping strategy to construct a P2/Zig-Zag biphasic cathode (NMFCAT) with an atomically interlocked heterojunction. Unlike conventional biphasic systems, this in-plane connection design enables continuous Na⁺ diffusion through atomically shared phase boundaries while leveraging strain-complementary evolution to restrict volume fluctuation to 1.44% (vs 3.12% in pure P2). Crucially, the Zig-Zag motifs serve as mechanical anchors at phase boundaries, exploiting the interlocking effect to suppress interfacial separation and maintain heterojunction integrity during cycling. Concurrently, the integrated P2 phase lowers the Na⁺ migration barrier to 0.19 eV, synergistically enhancing electrode kinetics and air stability (only 0.05% residual alkali increase after 7-day exposure). The rationally designed NMFCAT cathode exhibits superior electrochemical performance, fast electrode kinetics, and negligible volume variation, establishing a new paradigm for multiphase structural engineering in layered Mn-based cathodes for high-performance sodium-ion batteries.