Acta Physico-Chimica Sinica ›› 2019, Vol. 35 ›› Issue (12): 1357-1364.

• Article •

### Improved Sodium Storage Performance of Na0.44MnO2 Cathode at a High Temperature by Al2O3 Coating

Hui LI1,Shuangyu LIU1,Huiming WANG2,Bo WANG1,Peng SHENG1,Li XU1,Guangyao ZHAO1,Huitao BAI1,Xin CHEN1,Yuliang CAO3,Zhongxue CHEN2,*()

1. 1 State Key Laboratory of Advanced Transmission Technology, Global Energy Interconnection Research Institute Co. Ltd., Beijing 102211, P. R. China
2 Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, P. R. China
3 Hubei Key Laboratory of Electrochemical Power Sources, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China
• Received:2019-02-25 Accepted:2019-04-02 Published:2019-04-10
• Contact: Zhongxue CHEN E-mail:zxchen_pmc@whu.edu.cn
• Supported by:
the Science and Technology Project of State Grid(SGRIDGKJ[2017]841);the National Basic Research Program of China(2016YFB0901500);the National Natural Science Foundation of China(21875171);the National Natural Science Foundation of China(21673165)

Abstract:

Renewable energy resources (such as wind and solar) are being increasingly utilized to overcome issues of energy shortage and environmental deterioration. However, the intrinsically fluctuant and intermittent character of renewable energy sources hinders their practical application; therefore, batteries have been developed to act as a link between renewable energy sources and consumers. Lithium-ion batteries have become the most advanced battery technology in the last three decades, and have successfully captured the electric vehicles market; however, many concerns have recently arisen about the vastly expanded demand for lithium resources, which contrasts with their limited reserves. In this context, sodium-ion batteries have emerged as a promising alternative because of their intercalation chemistry similar to that of lithium-ion batteries, and the abundance of Na resources in the Earth's crust. Like lithium-ion batteries, the performance and cost of sodium-ion batteries are determined primarily by their cathodes. Among the various cathode materials that have been reported for sodium-ion batteries, Na0.44MnO2 is regarded as one of the most promising because of its opened three-dimensional tunnel structure and good chemical stability; it has also been demonstrated in previous studies to have superior cycling stability at room temperature. In practical terms, commercial batteries are often used at high temperatures (above 40 ℃) in summer. Several Mn-based cathode materials for lithium-ion batteries, such as LiMn2O4 and LiNi0.5Mn1.5O4, exhibit severe capacity decay at high temperatures. Therefore, the evaluation of the Na0.44MnO2 cathode in sodium-ion batteries at high temperatures is critical for its further commercialization. In this study, a Na0.44MnO2 cathode is prepared by a facile solid-state method and its electrochemical performance at a high temperature is measured. The electrochemical tests show that the Na0.44MnO2 cathode has a capacity retention of 66.5% over 100 cycles and a low reversible capacity of 12.3 mAh∙g-1 at 10C (1C = 120 mAh∙g-1). To improve its performance at a high temperature, Al2O3-coated Na0.44MnO2 is prepared via a liquid-phase method, and the coating effect is evaluated by electrochemical measurements as well as morphological, structural, and chemical composition analyses. The results show that the electrochemical performance of uncoated Na0.44MnO2 at 55 ℃ is significantly improved after coating with Al2O3; the capacity retention after 100 cycles increases to 79.2%, and the discharge capacity at 10C is increased to 63.6 mAh∙g-1. The improved performance is clearly attributed to the Al2O3 coating, which effectively prevents direct contact of Na0.44MnO2 with the electrolyte and alleviates the dissolution of manganese at a high temperature, thus maintaining a stable electrode/electrolyte interface and reducing charge transfer resistance.

MSC2000:

• O646