On the Electrochemical Properties of Carbon-Coated NaCrO[sub.2] for Na-Ion Batteries

• Published in: Batteries (Basel) Vol. 9; no. 9
• Main Authors: Shi, Zhepu, Wang, Ziyong, Shaw, Leon L, Ashuri, Maziar
• Format: Journal Article
• Language: English
• Published: MDPI AG 01-08-2023
• Subjects: Electrochemical analysis; Methods; United States
• ISSN: 2313-0105; 2313-0105
• DOI: 10.3390/batteries9090433

NaCrO[sub.2] is a promising cathode for Na-ion batteries. However, further studies of the mechanisms controlling its specific capacities and cycle stability are needed for real-world applications in the future. This study reveals, for the first time, that the typical specific capacity of ~110 mAh/g reported by many researchers when the charge/discharge voltage window is set between 2.0 and 3.6 V vs. Na/Na[sup.+] is actually controlled by the low electronic conductivity at the electrode/electrolyte interface. Through wet solution mixing of NaCrO[sub.2] particles with carbon precursors, uniform carbon coating can be formed on the surface of NaCrO[sub.2] particles, leading to unprecedented specific capacities at 140 mAh/g, which is the highest specific capacity ever reported in the literature with the lower and upper cutoff voltages at the aforementioned values. However, such carbon-coated NaCrO[sub.2] with ultrahigh specific capacity does not improve cycle stability because with the specific capacity at 140 mAh/g the Na deintercalation during charge is more than 50% Na ions per formula unit of NaCrO[sub.2] which leads to irreversible redox reactions. The insights from this study provide a future direction to enhance the long-term cycle stability of NaCrO[sub.2] through integrating carbon coating and doping.