Superior full-cell cycling and rate performance achieved by carbon coated hollow Fe3O4 nanoellipsoids for lithium ion battery

Iron oxide , a promising anode material for lithium ion batteries, has a high theoretical specific capacity but exhibits poor cycling performance and rate capability. To resolve these issues, 150 nm sized carbon coated, hollow Fe 3 O 4 nanoellipsoids are designed in this study. Owing to the relatively high utilization ratio of Fe 3 O 4 and the buffer provided by the carbon layer, this composite has enhanced lithium ion storage properties and long cycle life. From half-cell measurements, the capacity is found to be in excess of 400 mAh g −1 even after 1000 cycles at 5 A g −1 . And then, a facile and practical strategy is used to gain a relatively high compressed density (∼1.87 g cm −3 ), so the volumetric capacity of the Fe 3 O 4 @C electrode can be further enhanced by subjecting it to compression. In the full cell test, the Fe 3 O 4 @C electrode has a specific capacity of 400 mAh g −1 and volumetric capacity of 749 mAh cm −3 after 100 cycles. The improvement in cycling stability can be attributed to minimal volume expansion and the stability of the solid-electrolyte interphase (SEI) layer, over the nanoparticles . Finally, the evolution of solid-electrolyte interphase layer is indirectly monitored and the progressive loss of active lithium is quantitatively measured.