期刊
JOURNAL OF POWER SOURCES
卷 541, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.jpowsour.2022.231727
关键词
Sodium-ion batteries; Cathode material; Zr-substitution; Na vacancies; Superior rate performance
资金
- Guangdong Basic and Applied Basic Reuter Foundation [2021A1515010154]
- National Natural Science Foundation of China [51772337]
This study focuses on a new cathode material for sodium-ion batteries, Na4-xFeV1-xZrx (PO4)3/C, which replaces V3+ in Na3V2(PO4)3 with Fe2+ and a small amount of Zr4+. The substituted materials show reduced cost, low toxicity, increased Na+ concentration, and improved performance in terms of discharge capacity, rate capability, and cyclic stability.
The Na Super Ionic Conductor (NASICON)-type Na3V2(PO4)3 has aroused enormous attentions as the cathode material for sodium-ion batteries. However, the scarcity of vanadium resources and toxicity of vanadium complexes limit its large-scale application. Herein, we use a reductive acid assisted sol-gel method to replace half of V3+ in Na3V2(PO4)3 with Fe2+ for synthesizing a NASICON-structure Na4FeV(PO4)3/C, and substitute V3+ in Na4FeV(PO4)3 by small amount of Zr4+ for fabricating a series of Na4-xFeV1-xZrx (PO4)3/C (x = 0.1 and 0.2) materials. The substitution of V3+ by Fe2+ shows reduced cost, low toxicity, and increased Na+ concentration in per formula unit; while the substitution of V3+ by Zr4+ indicates expanded unit cell volume and abundant Na vacancies, which facilitate Na+ mobility and inherent electronic conductivity. Consequently, Na3.9FeV0.9Zr0.1(PO4)3/C electrode exhibits high discharge capacity (114 mAh g-1 at 0.1C), superior rate capability (66.7 mAh g-1 at 40C), and remarkable cyclic stability (capacity retention of 82.4% after 4000 cycles at 20C). The kinetic analyses and ex-situ characterizations confirm that small volume change (5.21%) and highly reversible redox reaction (Fe2+/3+ and V3+/4+) occur during the electrochemical process.
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