Abstract：
Na3V2(PO4)3 (NVP) encounters significant obstacles, including limited intrinsic electronic and ionic conductivities, which hinder its potential for commercial feasibility. Currently, the substitution of V3+ with Mn2+ is proposed to introduce favorable carriers, enhancing the electronic conductivity of the NVP system while providing structural support and stabilizing the NASICON framework. This substitution also widens the Na+ migration pathways, accelerating ion transport. Furthermore, to bolster stability, Al2O3 coating is applied to suppress the dissolution of transition metal Mn in the electrolyte. Notably, the Al2O3 coating serves a triple role in reducing HClO4 concentration in the electrolyte, inhibiting Mn dissolution, and functioning as the ion-conducting phase. Likewise, carbon nanotubes (CNTs) effectively hinder the agglomeration of active particles during high-temperature sintering, thereby optimizing the conductivity of NVP system. In addition, the excellent structural stability is investigated by in situ XRD measurement, effectively improving the volume collapse during Na+ de-embedding. Moreover, the Na3V5.92/3Mn0.04(PO4)3/C@CNTs@1wt.%Al2O3 (NVMP@CNTs@1wt.%Al2O3) possesses unique porous structure, promoting rapid Na+ transport and increasing the interface area between the electrolyte and the cathode material. Comprehensively, the NVMP@CNTs@1wt.%Al2O3 sample demonstrates a remarkable reversible specific capacity of 122.6 mAh/g at 0.1 C. Moreover, it maintains a capacity of 115.9 mAh/g at 1 C with a capacity retention of 90.2 mAh/g after 1000 cycles. Even at 30 C, it achieves a capacity of 87.9 mAh/g, with a capacity retention rate of 84.87 % after 6000 cycles. Moreover, the NVMP@CNTs@1wt.%Al2O3//CHC full cell can deliver a high reversible capacity of 205.5 mAh/g at 0.1 C, further indicating the superior application potential in commercial utilization.
摘要：
Na3V2（PO4）3（NVP）遇到重大障碍，包括有限的固有电子和离子电导率，这阻碍了其商业可行性的潜力。目前,提出用Mn2+取代V3+以引入有利的载体，增强NVP系统的电子电导率，同时提供结构支持并稳定NASICON框架。这种取代也拓宽了Na+的迁移途径，加速离子传输。此外，为了增强稳定性，施加Al2O3涂层以抑制过渡金属Mn在电解质中的溶解。值得注意的是,Al2O3涂层在降低电解质中的HClO4浓度中起着三重作用，抑制Mn溶解，起离子传导相的作用。同样，碳纳米管(CNTs)在高温烧结过程中有效地阻止活性颗粒的团聚,从而优化NVP体系的电导率。此外,通过原位XRD测量研究了优异的结构稳定性，有效改善Na+去嵌入过程中的体积塌陷。此外，Na3V5.92/3Mn0.04(PO4)3/C@CNTs@1wt。%Al2O3(NVMP@CNTs@1wt。%Al2O3)具有独特的多孔结构，促进Na+的快速传输和增加电解质和阴极材料之间的界面面积。全面来说,NVMP@CNT@1wt。%Al2O3样品在0.1C时表现出显著的可逆比容量为122.6mAh/g。其在1C下保持115.9mAh/g的容量,在1000次循环后保持90.2mAh/g的容量。即使在30摄氏度，它实现了87.9mAh/g的容量，6000次循环后的容量保持率为84.87%。此外，NVMP@CNT@1wt。％Al2O3//CHC全电池在0.1C时可提供205.5mAh/g的高可逆容量，进一步表明在商业利用方面具有优越的应用潜力。
