Electronic Structure Modulation in MoO₂/MoP Heterostructure to Induce Fast Electronic/Ionic Diffusion Kinetics for Lithium Storage

Abstract

Transition metal oxides (TMOs) are considered as the prospective anode materials in lithium‐ion batteries (LIBs). Nevertheless, the disadvantages, including large volume variation and poor electrical conductivity, obstruct these materials to meet the needs of practical application. Well‐designed mesoporous nanostructures and electronic structure modulation can enhance the electron/Li‐ions diffusion kinetics. Herein, a unique mesoporous molybdenum dioxide/molybdenum phosphide heterostructure nanobelts (meso‐MoO2/MoP‐NBs) composed of uniform nanoparticles is obtained by one‐step phosphorization process. The Mott–Schottky tests and density functional theory calculations demonstrated that meso‐MoO2/MoP‐NBs possesses superior electronic conductivity. The detailed lithium storage mechanism (solid solution reaction for MoP and partial conversion for MoO2), small change ratio of crystal structure and fast electronic/ionic diffusion behavior of meso‐MoO2/MoP‐NBs are systematically investigated by operando X‐ray diffraction, ex situ transmission electron microscopy, and kinetic analysis. Benefiting from the synergistic effects, the meso‐MoO2/MoP‐NBs displays a remarkable cycling performance (515 mAh g−1 after 1000 cycles at 1 A g−1) and excellent rate capability (291 mAh g−1 at 8 A g−1). These findings can shed light on the behavior of the electron/ion regulation in heterostructures and provide a potential route to develop high‐performance lithium‐ion storage materials.

MOF‐derived Multi‐Shelled NiP2 Microspheres as High‐Performance Anode Materials for Sodium‐/Potassium‐Ion Batteries

“…[ 28 ] However, single‐factor regulation cannot satisfy the demand for their further improvements in performance. As an effective strategy to improve overall performance, multifactor synergistic effects formulated by combining the advantages of each factor have been widely utilized in electrochemistry to achieve the objective of “two are better than one.” [ 31–33 ] Thus, modulation of multifactor for synergistic optimization of the sluggish electrochemical reaction kinetics and poor cycling stability in NiP 2 for SIBs and PIBs is expected to be a better strategy.…”

Regulating the electronic structure of MoO2/Mo2C/C by heterostructure and oxygen vacancies for boosting lithium storage kinetics

“…The peaks located at 530.5 and 531.8 corresponded to the Mo–O and C–O, and the peak located at 531.3 eV is related to the oxygen vacancy of MoO 2 /Mo 2 C/C. 31,36 Fig. 2e shows the EPR signals, as can be seen, MoO 2 /Mo 2 C/C showing the stronger EPR signals with a g value of 2.002 than that of MoO 2 /C confirmed the abundant oxygen vacancies in MoO 2 /Mo 2 C/C.…”

“…The peaks at 231.9, 228.7 eV correspond to the Mo 2 C phase, 232.6, 229.4 eV correspond to the Mo 4+ of MoO 2 , and 236, 233.2 eV correspond to the Mo 6+ of MoO 3 , which are related to the surface oxidation of MoO 2 /Mo 2 C/C during the test process or being exposed to the air for a long time. 31,32,49,50 The high-resolution O 1s spectrum of MoO 2 /Mo 2 C/C is shown in Fig. 2d.…”

“…As can be seen, two obvious couples of redox peaks at 1.54/1.7 and 1.21/1.42 V are related to the phase transformed process of Li x MoO 2 caused by Li + embedding into MoO 2 . 31,32 The redox peaks at 1.32 V/1.46 V may present the conversion reaction of Mo 2 C. 32,63 The involved reaction mechanism of MoO 2 /Mo 2 C/C can be described as:MoO 2 + x Li + + x e − ↔ Li x MoO 2 (0 ≤ x ≤ 1)Li x MoO 2 + (4 − x ) Li + + (4 − x )e − ↔ 2Li 2 O + MoMo 2 C + x Li + + x e − ↔ 2Mo + Li x C…”

“…Recently, constructing the heterostructure with interfacial electric field effects by coupling compounds with different properties has been recognized as an effective strategy to improve the intrinsic electronic conductivity and Li-ion diffusion kinetics. 30–34 Mai et al fabricated MoO 2 /MoP heterostructure nanobelts by a facile phosphating treatment, 31 and this material delivered an excellent cyclic performance with 515 mA h g −1 at 1 A g −1 after 1000 cycles and superior rate capability with 291 mA h g −1 at 8 A g −1 , which is due to the mesoporous and heterostructure of MoO 2 /MoP. Chen et al successfully synthesized MoO 2 /Mo 2 C heteronanotubes with excellent electrochemical performance.…”