Interlayer Cationic Defect Engineering in Lamellar Vanadate Cathodes Enables Ultralong-Lifespan Magnesium-Ion Batteries

The rate performance and lifespan of rechargeable magnesium-ion batteries (RMIBs) are limited by the low ionic conductivity and poor structural stability of the cathode materials. Herein, we introduce interlayer cationic defect engineering to enhance the diffusion dynamics and structural integrity of vanadate cathodes for the RMIBs. Through interlayer Mg2+ doping, we synthesized a defect-engineered cathode material (d-MgNVO) that establishes optimized migration pathways. Lattice defects confine ionic migration within the vanadate framework and reconstruct short, rapid, and reversible migration pathways, increasing the Mg2+ diffusion coefficient to 10–11–10–13 cm2 s–1. The d-MgNVO cathode exhibits a capacity of 198 mAh g–1 at 0.05 A g–1 and 73 mAh g–1 at 3.0 A g–1, showcasing good rate capability; the PTCDA//d-MgNVO full cell achieves a long lifespan of 5,000 cycles at 1.0 A g–1 with 79% capacity retention. These findings highlight interlayer cationic defect engineering as a promising strategy for high-performance, long-lasting RMIBs and other secondary batteries.