RESUMEN
Currently, the construction of amorphous/crystalline (A/C) heterophase has become an advanced strategy to modulate electronic and/or ionic behaviors and promote structural stability due to their concerted advantages. However, their different kinetics limit the synergistic effect. Further, their interaction functions and underlying mechanisms remain unclear. Here, a unique engineered defect-rich V2 O3 heterophase structure (donated as A/C-V2 O3- x @C-HMCS) composed of mesoporous oxygen-deficient amorphous - hollow core (A-V2 O3- x /HMC) and lattice-distorted crystalline shell (C-V2 O3 /S) encapsulated by carbon is rationally designed via a facile approach. Comprehensive density functional theory (DFT) calculations disclose that the lattice distortion enlarges the porous channels for Na+ diffusion in the crystalline phase, thereby optimizing its kinetics to be compatible with the oxygen-vacancy-rich amorphous phase. This significantly reduces the high contrast of the kinetic properties between the crystalline and amorphous phases in A/C-V2 O3- x @C-HMCS and induces the formation of highly dense A/C interfaces with a strong synergistic effect. As a result, the dense heterointerface effectively optimizes the Na+ adsorption energy and lowers the diffusion barrier, thus accelerating the overall kinetics of A/C-V2 O3- x @C-HMCS. In contrast, the perfect heterophase (defects-free) A/C-V2 O3 @C-HCS demonstrates sparse A/C interfacial sites with limited synergistic effect and sluggish kinetics. As expected, the A/C-V2 O3- x @C-HMCS achieves a high rate and ultrastable performance (192 mAh g-1 over 6000 cycles at 10 A g-1 ) when employed for the first time as a cathode for sodium-ion batteries (SIBs). This work provides general guidance for realizing dense heterophase cathode design for high-performance SIBs and beyond.
RESUMEN
Lithium-sulfur battery has been considered to be one of the promising alternatives to the traditional lithium-ion battery due to its high theoretical energy density and saving-cost. However, the sluggish reaction during the decomposition of lithium sulfide results in a low specific capacity and poor cycling stability. Herein Co3O4 nano-particle embedded mesoporous carbon rod (Co3O4@MCR) was prepared through a template method to accommodate sulfur as cathode of lithium-sulfur battery. The resultant composite was characterized by Raman spectra, XRD, TEM, SEM, etc. The electrochemical investigation demonstrated that Co3O4@MCR composite exhibits enhanced electrocatalytic performance in lithium-sulfur battery, which was confirmed by cyclic voltammograms, galvanostatic charge-discharge testing, and study of sulfide oxidation using linear sweep voltammetry. With the current density of 0.2 A/g, the specific discharge capacity can be achieved up to more than 1000 mAh/g after 100 cycles. The enhanced electrocatalytic conversion from Co3O4@MCR leads to a low over-potential, fast lithium-ion kinetics and sulfide oxidation reaction.