A Comparison of as-synthesized P2-K0.70[Cr0.85Sb0.15]O2 and Ion-Exchanged P2-K0.62Na0.08[Cr0.85Sb0.15]O2 Demonstrates the Superiority of the Latter as a Potassium-Ion Battery Cathode. Issue 10 (1st June 2020)

• Record Type: Journal Article
• Authors: Nathan, Muthu Gnana Theresa; Park, Woon Bae; Naveen, Nirmalesh; Park, Sangwon; Sohn, Kee-Sun; Pyo, Myoungho
• Is Part Of: Journal of the Electrochemical Society. Volume 167:Issue 10(2020)
• Publication Date: 2020-06-01
• Subjects: potassium ion battery -- ion exchange -- cathode -- oxide; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/ab9568
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : In this study, P2-type K0.7 [Cr0.85 Sb0.15 ]O2 (KCSO) is prepared via a solid-state route and its electrochemical properties are compared with those of P2-K0.62 Na0.08 [Cr0.85 Sb0.15 ]O2 (IE-KCSO), which is prepared via an electrochemical ion-exchange of P2-Na0.7 [Cr0.85 Sb0.15 ]O2 . Despite the near-identical chemical compositions and crystallographic structures, the IE-KCSO demonstrates rate capability and cyclic stability that is distinctively better than those of KCSO when used as a cathode in potassium-ion batteries (KIBs). For example, while KCSO shows a significant reduction in discharge capacities at high rates (48 mAh·g −1 at 2C vs 70 mAh·g −1 at 0.1C), IE-KCSO retains substantial capacities at high rates (67 mAh·g −1 at 2C vs 78 mAh·g −1 at 0.1C). The cyclic stability of IE-KCSO is also superior, as it delivers 96% of initial capacity after 100 charge/discharge (C/D) cycles, in contrast to 76% retention for KCSO. This study confirms that the Na + ions remaining in IE-KCSO contribute to the fast K + diffusion and, thereby, to its superior rate capability. Smaller dimensional changes in IE-KCSO during C/D are also apparent and these result in better cyclic stability. This work suggests that preparing KIB cathode materials via an ion-exchange protocol is more efficient than direct synthesis, particularly when the latter creates difficulties in obtaining phase-pure target compounds.