Investigation of the effects of heteroatom doping on von-Alpen-type NASICON electrolytes and its applications to solid-state sodium batteries

초록

The development of electrolytes with high ionic conductivity and stable electrode-electrolyte interfaces is crucial for the practical realization of solid-state sodium batteries. In this study, the effect of heteroatom doping in a von-Alpen-type Na super ionic conductor (NASICON) was investigated by substituting Zr4+ with Mg2+, Zn2+, and La3+ to enhance its material properties and evaluate its potential for solid-state sodium battery applications. Computational chemistry was employed to predict the thermodynamic stability influenced by dopant introduction and the changes in ionic conductivity arising from crystal structure distortion, with the predictions validated by experiments. The optimized Zn2+-doped NASICON (Zn-NZSP0.07) exhibited the highest total ionic conductivity of 2.74x10-3 S center dot cm-1, representing a 4.5-fold increase compared with undoped NASICON (6.00x10-4 S center dot cm-1). The material also showed a high relative density of 99.1%, indicating a compact and well-sintered microstructure, as confirmed by a three-point bending test. Furthermore, a high critical current density of 1.4 mA center dot cm-2 was achieved in symmetric cell testing. Additionally, a Na3V2(PO4)3||Zn-NZSP0.07||Na cell delivered an initial capacity of 103.9 mAh center dot g-1 at 0.1 A center dot g-1 and retained 73.4% of its capacity after 200 cycles. These results demonstrate that optimal heteroatom doping is crucial for enhancing the performance of NASICON.

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