An iron oxyborate FeBO material as a high-performance anode for lithium-ion and sodium-ion batteries.

An Fe3BO5 anode material synthesized by reducing Fe3BO6 was comprehensively studied for use in both lithium- and sodium-ion batteries. As a lithium-ion battery anode, the obtained Fe3BO5 displays a high initial reversible capacity of 654.7 mA h g-1 (with a coulombic efficiency of 75%) at a current density of 0.1 A g-1 and a favorable cycling performance, with a capacity of 544.6 mA h g-1 at 0.4 A g-1 after 400 cycles. As a sodium-ion battery anode, Fe3BO5 displays initial discharge/charge capacities of 644.6 and 433.6 mA h g-1 at a current density of 0.1 A g-1. Besides this, Fe3BO5 exhibits a stable reversible capacity of about 380 mA h g-1 at 0.4 A g-1 during the first 100 cycles and an excellent rate performance with a high capacity of 304.5 mA h g-1, even at a current density of as large as 4 A g-1. Kinetics analysis shows that the significance in high Na+ capacitive contribution at a high rate should account for the excellent rate performance. The excellent electrochemical properties demonstrate that the Fe3BO5 material could be an effective and promising anode candidate for both lithium- and sodium-ion batteries.