Accelerating Electrochemical Responses of NaVMn(PO) via Bulk-Defects and Architecture Engineering for High-Performance Sodium-Ion Batteries.

Manganese-based NASICON-type NaVMn(PO) (NVMP) has captured widespread attention in sodium-ion batteries (SIBs) due to its abundant reserves and high operating voltages. However, the low intrinsic conductivity and detrimental Jahn-teller (J-T) effect impedes its electron and ion transfer, leading to rapid structural degradation and capacity decay. Herein, a facile multiscale coupling strategy is proposed to synthesize the nanosheet-stacked rods (NVMP-NSRs) with rational defects for improving intrinsic conductivity and structural stability, thus accelerating electrochemical responses. Localized unsaturated coordination states around vanadium atoms in NVMP-NSRs are also regulated, further facilitating rapid Na diffusion with relieved volume expansion due to the unique architecture design. Density functional theory (DFT) calculations reveal highly rearranged interfacial charges, yielding benefits for reducing the energy barriers of Na migration. The innovative NVMP-NSRs with appropriate bulk defects exhibit considerable discharge capacity (120.1 mAh g at 0.5C), high-rate performance (70.9 mAh g at 30C), and negligible capacity decay (3000 cycles at 20C). Moreover, the assembled NVMP-NSRs//hard carbon full cells demonstrate a high energy density of 391.1 Wh kg with excellent cyclic stability (91.2% after 100 cycles at 1C). The multiscale coupling strategy in this work offers new avenues to design high-performance electrode materials toward fast electrochemical responses and robust structural stability.