Synchronous synthesis of Kirkendall effect induced hollow FeSe2/C nanospheres as anodes for high performance sodium ion batteries.

In this work, we have developed a simple and facile method to synchronously synthesize hollow FeSe2/C nanospheres using the Kirkendall effect. When evaluated as an anode for SIBs, the hollow FeSe2/C nanospheres exhibit a high discharge capacity retention of 474.1 mA h g-1 at 0.05 A g-1 (based on the calculation of FeSe2), which is very close to the theoretical capacity of FeSe2 (∼500 mA h g-1). Meanwhile, hollow FeSe2/C also has a superior rate capability of 364.5 and 316.5 mA h g-1 even at 2.0 and 5.0 A g-1, respectively. The high performance of the hollow FeSe2/C nanospheres can be ascribed to the unique carbon coated hollow nanostructure.