AUTHOR=Tang Shibao , Zhang Xiaoping , Sui Yulei , Wang Bingjue , Li Jiangpeng , Wu Ling 

TITLE=A Comparative Study on Na2Fe0.6Mn0.4PO4F/C Cathode Materials Synthesized With Various Carbon Sources for Na-ion Batteries

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.633949

DOI=10.3389/fchem.2020.633949

ISSN=2296-2646

ABSTRACT=<p>Na<sub>2</sub>Fe<sub>0.</sub>6Mn<sub>0.4</sub>PO<sub>4</sub>F/C composite materials are synthesized with various carbon sources via a simple spray-drying method in this study, and the effect of carbon sources on structure, morphology, and electrochemical properties of Na<sub>2</sub>Fe<sub>0.6</sub>Mn<sub>0.4</sub>PO<sub>4</sub>F/C materials are investigated in detail. XRD and SEM results indicate that the reduction ability of carbon sources has a key impact on the structure and morphology of Na<sub>2</sub>Fe<sub>0.6</sub>Mn<sub>0.4</sub>PO<sub>4</sub>F/C composite materials. Among these Na<sub>2</sub>Fe<sub>0.6</sub>Mn<sub>0.4</sub>PO<sub>4</sub>F/C materials, the sample prepared with ascorbic acid presents a uniform hollow spherical architecture. Electrochemical analysis demonstrates that the Na<sub>2</sub>Fe<sub>0.6</sub>Mn<sub>0.4</sub>PO<sub>4</sub>F/C sample prepared with ascorbic acid has optimal electrochemical performance. The sample shows high discharge capacities of 95.1 and 48.1 mAh g<sup>−1</sup> at 0.05C and 1C rates, respectively, and it exhibits an improved cycle stability (91.7% retention after 100 cycles at 0.5C), which are superior to Na<sub>2</sub>Fe<sub>0.6</sub>Mn<sub>0.4</sub>PO<sub>4</sub>F/C materials prepared with other carbon sources. This study demonstrates that the reduction ability of carbon sources significantly influences the electrochemical properties of fluorophosphate/C composite materials. This work also provides a promising strategy to obtain high performance cathode materials for sodium-ion batteries.</p>