Aliovalent doping and structural design of MoSe2 with fast reaction kinetics for high-stable sodium-ion half/full batteries

The development of high-quality anode materials is critical for the advancement of sodium-ion batteries (SIBs). MoSe2 is a candidate anode for SIBs, while its inherent limitations, such as the agglomeration of nanosheets, poor electron conductance and mechanical strain due to volume changes during cycling, which can lead to decreased performance and durability in SIBs. To overcome the challenges, a novel aliovalent doping and structural engineering was taken to prepare reduced graphene oxide (rGO) functionalized and phosphorus-doped MoSe2 flake (P-MoSe2@rGO) via in situ growth technique. The unique structural design of P-MoSe2@rGO addresses material limitations and optimizes performance by providing a high conductive grid for ion/electron transfer, a large surface area for full electrolyte penetration, and effective suppression of MoSe2 nanosheet agglomeration and mechanical strain due to volume change during charge/discharge in SIBs. The P-MoSe2@rGO inherits the enhanced electronic conductivity and enlarged layer spacing (from 0.652 to 0.668 nm), which boosts the reaction kinetics and facilitates the insertion/extraction of sodium ions. The P-MoSe2@rGO exhibits excellent long-cycle properties with a high reversible capacity of 384 mAh/g at 2 A/g and 338 mAh/g at 10 A/g after 1450 circulations. Detailed discussion of reaction kinetics is conducted. Theoretical calculations prove that doping of P atoms in MoSe2 reduces the forbidden band gap from 1.443 to 1.397 eV and accelerates ion and electron migration. Furthermore, the full cell P-MoSe2@rGO//Na3V2(PO4)3@C (NVP@C) demonstrates a remarkable cycling durability of 326 mAh/g after 200 cycles and a high energy density of 159.6 Wh kg−1. This process provides a reference for the adjustment and modification of MoSe2 to adapt to high performance SIBs anode.