Synergistic Dual-Pinning Engineering Enables Stable Mn-Based Layered Oxide Cathodes for High-Performance Sodium-Ion Batteries

Mn-based oxide cathodes for sodium-ion batteries (SIBs) often suffer from structural degradation caused by Jahn–Teller distortion and irreversible phase transitions. Here, we propose a dual-site stabilization strategy by Mo/Mg codoping, which not only drives the transformation of the tunnel-type Na 0.44 MnO 2 into a P2-layered structure (Na 0.44 Mn 0.97 Mo 0.01 Mg 0.02 O 2, denoted as MoMg-12) by modulating the total energy to enhance capacity but also employs Mo and Mg ions substituting Mn sites to implement synergistic dual-pinning engineering to stabilize the structure. This dual-pinning mechanism concurrently suppresses Jahn–Teller distortion by stabilizing Mn redox activity and improves air stability by reducing Na + /H + exchange while promoting a hydrophobic surface. The optimized MoMg-12 cathode delivers a high specific capacity of 189 mAh g –1 within its stable P2-type layered structure coupled with superior rate capability and long-term cycling stability. In addition, its practical viability is demonstrated when paired with a Na 2 C 2 O 4 sodium compensation additive. This study highlights the effectiveness of the dual-pinning engineering in preserving structural integrity and offers a practical design example for high-energy-density and air-stable SIB cathodes.