Crystalline/Amorphous Interface Engineering for Superior Sodium-Ion Storage

Heterojunction engineering based on crystalline/crystalline interfaces has been demonstrated as a promising strategy for enhancing the performance of SIBs. However, the mismatch in expansion coefficients between crystalline components induces detrimental interfacial stress during Na⁺ intercalation/deintercalation or thermal expansion, ultimately leading to interfacial cracking or phase separation, which consequently results in rapid degradation of the capacity and cycling durability in SIBs. To address this issue, this work proposes a crystalline/amorphous (C/A) heterojunction constructed from crystalline VS₄ and amorphous CoS to alleviate interfacial stress while boosting the performance of SIBs. Theoretical calculations reveal that the C/A heterojunction markedly improves Na⁺ diffusion kinetics by reducing diffusion energy barriers and increasing Na⁺ transport channels through interfacial stress modulation, electronic structure tuning, and sulfur vacancies. Consequently, the synthesized material exhibits excellent rate capability, superior cycling stability, and high Na⁺ storage capacity. A high reversible specific capacity of 700.25 mAh g^-1 is achieved after 100 cycles at 1.0 A g^-1, with an ultralow capacity decay of 0.000045% per cycle. Even at an ultrahigh current density of 20 A g^-1, a considerable reversible capacity of 481.4 mAh g^-1 is retained after 1200 cycles. The full cell configured with Na₃V₂(PO₄)₃ as the cathode material demonstrates outstanding cycling stability, retaining 90.8% of its initial capacity after 11000 cycles at a current density of 5.0 A g^-1. This work proposed a novel strategy for developing next-generation heterojunction materials for SIBs.