FeN Coordination Induced Ultralong Lifetime of Sodium-Ion Battery with the Cycle Number Exceeding 65 000.

Sodium-ion batteries (SIBs) have received increasing attention because of their appealing cell voltages and cost-effective features. However, the atom aggregation and electrode volume variation inevitably deteriorate the sodium storage kinetics. Here a new strategy is proposed to boost the lifetime of SIB by synthesizing sea urchin-like FeSe 2 /nitrogen-doped carbon (FeSe 2 /NC) composites. The robust FeN coordination hinders the Fe atom aggregation and accommodates the volume expansion, while the unique biomorphic morphology and high conductivity of FeSe 2 /NC enhance the intercalation/deintercalation kinetics and shorten the ion/electron diffusion length. As expected, FeSe 2 /NC electrodes deliver excellent half (387.6 mAh g -1 at 20.0 A g -1 after 56 000 cycles) and full (203.5 mAh g -1 at 1.0 A g -1 after 1200 cycles) cell performances. Impressively, an ultralong lifetime of SIB composed of FeSe 2 /Fe 3 Se 4 /NC anode is uncovered with the cycle number exceeding 65 000. The sodium storage mechanism is clarified with the aid of density function theory calculations and in situ characterizations. This work hereby provides a new paradigm for enhancing the lifetime of SIB by constructing a unique coordination environment between active material and framework.