Defect-Induced Dense Amorphous/Crystalline Heterophase Enables High-Rate and Ultrastable Sodium Storage

摘要

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 V2O3 heterophase structure (donated as A/C-V2O3-x@C-HMCS) composed of mesoporous oxygen-deficient amorphous (-) hollow core (A-V2O3-x/HMC) and lattice-distorted crystalline shell (C-V2O3/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-V2O3-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-V2O3-x@C-HMCS. In contrast, the perfect heterophase (defects-free) A/C-V2O3@C-HCS demonstrates sparse A/C interfacial sites with limited synergistic effect and sluggish kinetics. As expected, the A/C-V2O3-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.

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