School of Materials Science and Engineering and Guangdong Provincial, Key Laboratory of Advanced Energy Storage Materials, South China University of Technology, Guangzhou, Guangdong, 510641, China.
Multiscale Crystal Materials Research Center, Shenzhen Institute of Advanced Technology, Chinese Academy of Science, Shenzhen, 518055, China.
Adv Sci (Weinh). 2022 Dec;9(36):e2205575. doi: 10.1002/advs.202205575. Epub 2022 Oct 30.
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 V O heterophase structure (donated as A/C-V O @C-HMCS) composed of mesoporous oxygen-deficient amorphous hollow core (A-V O /HMC) and lattice-distorted crystalline shell (C-V O /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-V O @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-V O @C-HMCS. In contrast, the perfect heterophase (defects-free) A/C-V O @C-HCS demonstrates sparse A/C interfacial sites with limited synergistic effect and sluggish kinetics. As expected, the A/C-V O @C-HMCS achieves a high rate and ultrastable performance (192 mAh g over 6000 cycles at 10 A g ) 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.
目前，通过构建非晶/晶相（A/C）异质结构来调节电子和/或离子行为并促进结构稳定性已成为一种先进策略，这是因为它们具有协同优势。然而，它们不同的动力学限制了协同效应。此外，它们的相互作用功能和潜在机制仍不清楚。在这里，通过一种简便的方法，合理设计了一种独特的工程缺陷富 V O 异质相结构（命名为 A/C-V O @C-HMCS），它由介孔缺氧非晶空心核（A-V O /HMC）和晶格畸变的结晶壳（C-V O /S）组成，并用碳封装。综合密度泛函理论（DFT）计算表明，晶格畸变扩大了结晶相中 Na 扩散的多孔通道，从而优化了动力学，使其与富氧空位的非晶相兼容。这显著降低了 A/C-V O @C-HMCS 中结晶相与非晶相之间动力学性质的高对比度，并诱导形成具有强协同效应的高度密集的 A/C 界面。结果，密集的异质界面有效地优化了 Na 吸附能并降低了扩散势垒，从而加速了 A/C-V O @C-HMCS 的整体动力学。相比之下，具有完美异质相（无缺陷）的 A/C-V O @C-HCS 具有稀疏的 A/C 界面位，协同效应有限，动力学缓慢。不出所料，首次将 A/C-V O @C-HMCS 用作钠离子电池（SIB）的正极时，它表现出高倍率和超稳定的性能（在 10 A g 下 6000 次循环后为 192 mAh g ）。这项工作为实现高性能 SIB 及其它应用的密集异质相阴极设计提供了一般性指导。
