The main challenge for sodium/potassium ion storage is
to find
the suitable host materials to accommodate the larger-sized Na+/K+ and conquer the sluggish chemical kinetics.
Herein, by selenation of polyoxometalate in electrospinning fiber,
a novel MoO2/MoSe2 heterostructure embedded
in one-dimensional (1D) N,P-doped carbon nanofiber (MoO2/MoSe2@NPC) is rationally constructed to show distinct
enhancement of rate performance and cycle life for sodium ion batteries
(SIBs) and potassium ion batteries (PIBs). The 1D skeleton of MoO2/MoSe2@NPC decreases the diffusion pathway of Na+/K+, and the doping of N/P heteroatoms in carbon
fiber creates abundant active sites and provides good reachability
for Na+/K+ transportation. MoSe2 nanosheets
grow in the bulk phase of MoO2
via in situ local phase transformation to achieve effective and firm heterointerfaces.
Especially, the exposure extent of heterointerfaces can be controlled
by treatment temperature during the preparation process, and the optimized
heterointerfaces result in an ideal synergic effect between MoO2 and MoSe2. DFT calculations confirm that the internal
electric field in the heterogeneous interface guides the electron
transfer from MoO2 to MoSe2, combined with strong
adsorption capacity toward sodium/potassium, facilitating ion/electron
transfer kinetics. It is confirmed that the MoO2/MoSe2@NPC anode for SIBs delivers 382 mA h g–1 under 0.1 A g–1 upon 200 cycles; meanwhile, a
reversible capacity of 266 mA h g–1 is maintained
even under 2 A g–1 after 2000 cycles. For PIBs,
it can reach up to 216 mA h g–1 in the 200th cycle
and still retain 125 mA h g–1 after 2000 cycles
under 1 A g–1. This study opens up a new interface
manipulation strategy for the design of anode materials to boost fast
Na+/K+ storage kinetics.