Structure and Electrochemical Properties of α-NaFeO2 Obtained under Various Hydrothermal Conditions. Issue 10 (1st January 2019)

• Record Type: Journal Article
• Authors: Tabuchi, Mitsuharu; Kataoka, Riki
• Is Part Of: Journal of the Electrochemical Society. Volume 166:Issue 10(2019)
• Page Start: A2209
• Page End: A2214
• Publication Date: 2019-01-01
• Subjects: Batteries -- positive electrode material -- Sodium-ion battery; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.1411910jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : High-crystallinity α-NaFeO2 samples can be obtained from α-FeOOH in highly concentrated NaOH solution under various hydrothermal conditions. The electrochemical performance of the process depends on the hydrothermal condition: selecting a higher treatment temperature engenders better cycle performance. The cycle performance can also be changed by adding small amounts of KOH or LiOH·H2 O to the NaOH solution. Better cycle performance is obtainable for a sample with added KOH. X-ray Rietveld analysis revealed a metastable structure: Na and Fe ion sites (3 a and 3 b sites) were not fully occupied in a hexagonal layered rock salt structure ( R 3 ¯ m ). The electrochemical cycle performance depends strongly on the crystal structure: conversion to nearly ideal α-NaFeO2 structure with small lattice parameters is effective to attain better cycle performance. Growing-up primary particle size was also important strategy to obtain the sample with better cycle performance.