Accelerating Electrochemical Responses of Na₄VMn(PO₄)₃ via Bulk-Defects and Architecture Engineering for...

Manganese-based NASICON-type Na₄VMn(PO₄)₃ (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^-1 at 0.5C), high-rate performance (70.9 mAh g^-1 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^-1 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.