Enhancing Electrochemical Performance By Coating Al2O3 on Na0.6Mn0.66Ni0.22Co0.11O2 cathode in Sodium-Ion Batteries

Abstract

Rechargeable sodium-ion batteries (SIBs) have recently attracted much attention as an alternative electric energy storage device to lithium-ion batteries (LIBs) because of the availability and low cost of sodium. However, the cycle performance of SIBs is not comparable to LIBs due to the side reaction between electrode and electrolyte as well as the structural instability and transition metal dissolution into electrolyte. In order to solve these problems, various surface coating techniques have been used to coat oxides on the cathode active material surface before making the electrode. However, additional coating process causes the price increase, and they have not been applied for SIB cathodes. Herein, an Al2O3 thin film was directly deposited on the surface of Na0.6Mn0.66Ni0.22Co0.11O2(NaMNCO2) cathode by a radio-frequency magnetron sputtering. Only 4 min coating of Al2O3 upon the NaMNCO2 could improve the specific capacity from 134.6 to 146.4 mA h g-1 in a voltage range of 2.1 to 4.3 V. In addition, the cycle performance was also enhanced to deliver 49.7 mA h g-1 even after 200 cycles. In case of high voltage operation up to 4.5 V, the discharge capacities of pristine and Al2O3-coated electrodes are 150.6 and 160.1 mA h g-1, respectively. Acknowledgement This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977).