1成果简介

        水系锌离子电池（AZIBs）面临锌负极树枝状晶体形成和副反应等关键问题，而其正极材料中Zn²⁺/H共插层现象进一步加剧了这些问题。尽管无锌金属AZIBs可规避锌负极缺陷，但正负极动力学失配严重阻碍了其商业化应用。本文，华南理工大学邝泉 副教授在《Chemical Engineering Journal》期刊发表名为“Decoupling Zn2+/H Co-insertion in VOMoO+4/rGO heterostructure for dendrite-free symmetric zinc-ion batteries”的论文，研究基于一对具有VOMoO+4/还原氧化石墨烯异质结构（VMO/rGO）的相同电极，构建了高性能水系对称锌离子电池（ASZBs）。

        VMO材料具有V单键Mo双氧化还原活性中心，使其成为理想的对称电极材料。经过充激活形成氧空位后，优化后的VMO/rGO电极在VMO/rGO||Zn半电池中于0.1 A g−1电流密度下展现出377 mAh g−1的峰值容量。然而，由于VMO/rGO与锌金属的不兼容性，该体系循环稳定性较差。通过设计新型VMO/rGO双电极ASZB电池实现Zn²⁺/H共插层解耦，该电池在0.1 A g⁻¹条件下展现出114.7 mAh g⁻¹的比容量，并在0.5 A g⁻¹循环2000次后仍保持78.6%的容量保持率。这项工作为无锌金属电池提供了新思路，并进一步推动了ASZB电池的发展。

        2图文导读

      图1. Crystal structure and microstructure of VMO. (a) Rietveld structure refinement of the powder XRD pattern. (b) Schematic of the crystal structure. (c) Raman spectrum. XPS spectra of (d) V 2p and (e) Mo 3d.

        图2. Crystal structure and microstructure of VMO/rGO. (a) Schematic illustration of VMO/rGO synthesis. (b) XRD patterns of VMO and VMO/rGO. (c) and (d) SEM images. (e) TEM images, (f) HRTEM image and SAED pattern (inset). (g) EDX elemental mapping.

     图3. Electrochemical property comparison of the VMO||Zn and VMO/rGO||Zn batteries. (a) Cycling performance at 0.5 A g−1. (b) Rate performance at various current densities from 0.1 to 5 A g−1. (c) Nyquist plots in pristine and overcharged states. (d) and (e) Charge/discharge curves at different current rates. (f) and (g) CV curves at different scan rates from 0.2 to 1 mV s−1. (h) and (i) Log i vs. log v plots at four peaks. (j) Capacitive contribution ratios. (k) GITT curves and calculated ion-diffusion coefficients (D).

       图4. Structural evolution of the VMO cathode. (a) Ex-situ XRD patterns, (b) ex-situ Raman spectra, and (c) in-situ XRD patterns of the VMO cathode during the initial charge-discharge cycles.

       图5. Valence state and morphological changes of the VMO cathode. (a) ICP-OES results, (b) EPR patterns, (c) XPS spectra, and (d)–(g) SEM images of the VMO cathode at different cycling states.

        图6. Failure analysis and DFT Calculations. (a) Cycling performance of the VMO||Zn electrolytic cell at 0.1 A g−1. (b) Comparison of zinc foil anodes before and after cycling. Optimized geometric models of the initial, transition, and final states of (c) VMO and (d) VMO/rGO. (e) H diffusion energy barriers in VMO and VMO/rGO. (f) DOS of VMO and VMO/rGO.+

       图7. Electrochemical Performance and Kinetics of VMO/rGO in ASZBs. (a) Schematic diagram of the ASZB. (b) Rate performance. (c) Charge-discharge and (d) cycling performance at 0.1 A g−1. (e) CV performance at different scan rates. (f) Cycling performance at 0.5 A g−1. (g) Comparison of specific capacity at different current densities with various zinc metal-free “rocking chair” AZIBs. (h) Rate performance of ASZB pouch cell. (i) Cycling performance of ASZB pouch cell at 0.3 A g−1.

        3小结 

        综上所述，本研究合成了纯VMO材料及VMO/rGO异质结构，并比较了其作为AZIB电池正极材料的电化学性能。通过过充活化策略创造大量氧空位，VMO/rGO正极在0.1Ag−1电流密度下展现出377.1mAh g−1的优异比容量。XRD、拉曼光谱和XPS综合分析揭示了VMO材料独特的Zn2+/H共插层机制。然而VMO||Zn半电池存在严重的容量衰减问题。尽管过充活化与rGO复合化策略可部分缓解该问题，但最终性能仍不理想（在5 A g−1条件下经2000次循环后容量保持率低于50%）。失效分析表明，容量衰减的根本原因是VMO独特的锌存储机制与锌金属阳极上锌枝晶形成之间的串扰效应。因此，通过采用VMO/rGO双电极设计新型水系对称锌离子电池，成功将Zn²⁺与H的共插层作用解耦至两个电极，从而解决了VMO||Zn体系的快速容量衰减问题。该对称电池不仅展现出优异的循环稳定性，更呈现出卓越的容量与倍率性能：在0.1 A g⁻¹条件下达到114.7 mAh g⁻¹，在1 A g⁻¹高电流下仍维持81.2 mAh g⁻¹。最终测试阶段中，软包电池与硬币电池的电化学性能相当，表明其具备实际应用潜力。基于VMO/rGO双电极的创新对称电池策略，为水系锌离子电池研究开辟了新路径，并为设计无锌金属的AZIB电池提供了重要参考。

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