Ambient stable Na0.76Mn0.48Ti0.44O2 as anode for Na-ion battery

The moisture/air sensitive properties of electrode materials for Na ion batteries (NIBs) increase their storage cost and prohibit their practical applications. We herein report an ambient stable Na0.76Mn0.48Ti0.44O2 as anode of NIBs. It has been synthesized by sol-gel method and characterized by SEM and TEM, which displays irregular sheet-like morphology. The XRD result demonstrates that it is composed by tunnel type NaMnTiO4 and layered structured Na0.91MnO2. Evaluated as anode in NIB, it demonstrates an initial charge capacity of 103.4 mAh g−1. This is among one of the best result compared with other Ti-based insertion-type anode. The capacity retention is as high as 74.9% after 600 cycles, and a high rate performance is obtained. Ti serves as active center redox between Ti4+/Ti3+ during the discharge/charge process. Meanwhile, the introduction of Mn to the framework stabilize the electrode structure. Importantly, the ambient storage properties have been examined, and no obvious performance fading is observed even after exposing the materials to ambient air for more than 100 days. The combination of Mn and Ti in the composite contribute to the improved storage performance. The present study provides a new insight into electrode material design with improved ambient storage and electrochemical performance for NIBs.