Tuning crystal structure and redox potential of NASICON-type cathodes for sodium-ion batteries
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Tuning crystal structure and redox potential of NASICON-type cathodes for sodium-ion batteries Xuemei Ma1, Xinxin Cao1,2 (), Yifan Zhou1, Shan Guo1, Xiaodong Shi1, Guozhao Fang1,2, Anqiang Pan1,2, Bingan Lu3, Jiang Zhou1,2 (), and Shuquan Liang1,2 () 1
School of Material Science and Engineering, Central South University, Changsha 410083, China Key Laboratory of Electronic Packaging and Advanced Functional Materials of Hunan Province, Central South University, Changsha 410083, China 3 School of Physics and Electronics, Hunan University, Changsha 410082, China 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 6 June 2020 / Revised: 22 July 2020 / Accepted: 26 July 2020
ABSTRACT Sodium superionic conductor (NASICON)-type compounds have been regarded as promising cathodes for sodium-ion batteries (SIBs) due to their favorable ionic conductivity and robust structural stability. However, their high cost and relatively low energy density restrict their further practical application, which can be tailored by widening the operating voltages with earth-abundant elements such as Mn. Here, we propose a rational strategy of infusing Mn element in NASICON frameworks with sufficiently mobile sodium ions that enhances the redox voltage and ionic migration activity. The optimized structure of Na3.5Mn0.5V1.5(PO4)3/C is achieved and investigated systematically to be a durable cathode (76.6% capacity retention over 5,000 cycles at 20 C) for SIBs, which exhibits high reversible capacity (113.1 mAh·g−1 at 0.5 C) with relatively low volume change (7.6%). Importantly, its high-areal-loading and temperature-resistant sodium ion storage properties are evaluated, and the full-cell configuration is demonstrated. This work indicates that this Na3.5Mn0.5V1.5(PO4)3/C composite could be a promising cathode candidate for SIBs.
KEYWORDS sodium superionic conductor (NASICON)-type, crystal structure, cathode material, full cell, sodium ion battery
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Introduction
Rechargeable sodium-ion batteries (SIBs) have been considered as promising alternative to lithium-ion batteries (LIBs) for grid-scale electric storage applications owing to the good performance as well as low cost of sodium resources [1–3]. However, SIBs face the challenges of low energy density and poor cycling stability [4]. In recent years, a wide range of materials with different crystalline structures and building units have been investigated as sodium hosts [5, 6], such as layered structure, tunnel structure, and framework structure, etc. Among them, polyanionic framework compounds have been brought into the limelight owing to their excellent structural stability, good safety, and small volume variations during cycling, especially for the need of large-scale energy-storage. As a typical one, Na3V2(PO4)3, an immortal superstar, has been extensively investigated as promising two-electron reaction cathode material. However, it faces severe bottle-necks owing to limited energy density (about 370 Wh·kg−1), low vanadium (V) abunda
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