Stabilizing the Deep Sodiation Process in Layered Sodium Manganese Cathodes by Anchoring Boron Ions

Abstract Advanced high‐energy‐density sodium‐ion batteries (SIBs) are inseparable from cathode materials with high specific capacities. Layered manganese‐rich oxides (Na_xMnO₂, 0.6 ≤ x ≤1) are promising cathode materials owing to their ease of intercalation and extraction of a considerable amount of sodium ions. However, lattice interactions, especially electrostatic repulsive forces and anisotropic stresses, are usually caused by deep desodiatin/sodiation process, resulting in intragranular cracks and capacity degradation in SIBs. Here, boron ions are introduced into the layered structure to build up B─O─Mn bonds. The regulated electronic structure in Na_0.637B_0.038MnO₂ (B‐NMO) materials inhibits the deformation of MnO₆ octahedra, which finally achieves a gentle structural transition during the deep sodiation process. B‐NMO electrode exhibits a high capacity (141 mAh g^–1) at 1 C with a capacity retention of 81% after 100 cycles. Therefore, anchoring boron to manganese‐rich materials inhibits the detrimental structural evolution of deep sodiation and can be used to obtain excellent cathode materials for SIBs.