【作者】 张涛；

【导师】 吴贤文； 向延鸿；

【作者基本信息】 吉首大学 ， 化学， 2022， 硕士

【摘要】 近年来,受中东地区局势不稳定的影响,导致化石燃料等不可再生资源需求成本激增,而最大限度的对太阳能、风能等可再生资源的利用显得尤为重要。将可再生能源转化为电能储存的二次电池受到研究者们的广泛关注。中性或弱酸性体系下以金属锌为负极的水系锌离子电池（简称AZIBs）由于成本低、安全性高、组装工艺简单等优点,成为研究的首选。钒具有价格低廉、化合价及其结构的多样性,钒基正极材料拥有高的理论比容量和优异的倍率特性,在AZIBs中是一类具有广阔应用前景的正极材料。但钒基材料在Zn²⁺的不断嵌入/脱出过程中引起材料结构不稳定、导电性能较差、电压窗口比较窄等系列问题,限制了其在AZIBs中的应用。基于此,本文通过层间金属离子预嵌、复合材料的可控制备来提高材料的电化学稳定性。具体研究内容如下:（1）以C₂H₂O₄·2H₂O为还原剂,NH₄VO₃为钒源通过水热法合成（NH₄）₂V₁₀O₂₅·8H₂O材料（NVO）。以Al（NO₃）₃·9H₂O为铝源,通过不同Al:V物质的量之比（1:3、1:6、1:9）进行金属离子的预嵌改性,在相同制备工艺下,Al³⁺的预嵌能使材料形貌由密集堆叠的片状结构向更细小更分散的纳米片状结构转变。细小分散的纳米片更有利于材料与电解液的接触,为Zn²⁺的传输提供快速、便捷的扩散通道。Al-6NVO材料经过100次循环后,保持着较高的放电比容量（252 m Ah/g）,在2 A/g电流密度下循环1200圈放电比容量仍能保持在122.8 m Ah/g,容量保持率高达94.6%。双阳离子NH₄⁺和Al³⁺协同于层间形成支柱作用能有效提高Zn²⁺的扩散动力学,改善材料的电化学性能。（2）以Na₃VO₄为钒源、无水Ca Cl₂为钙源,通过水热法合成Na⁺与Ca²⁺离子共预嵌V₁₀O₂₄·12H₂O材料（Na,Ca-VOH）,并以此作为正极,商业锌片为负极组装成AZIBs。并采用水热法分别制备出了单金属离子Na⁺(或Ca²⁺)预嵌V₁₀O₂₄·12H₂O材料,利用陈化法制备V₁₀O₂₄·12H₂O纯相材料（VOH）,通过四种材料的电化学性能比较,Na,Ca-VOH材料展现出较为优异的电化学循环稳定性。在2.0 A/g电流密度下经过500圈循环保持着较高的放电比容量（116.9 m Ah/g）,容量保持率约为94.3%。在5.0 A/g高电流密度下经过1000次循环依然有89.0 m Ah/g放电比容量,容量保持率约为98.5%。实验证明Na、Ca金属离子的共预嵌能进一步扩大材料的层间距与提高材料的稳定性,花状结构Na,Ca-VOH材料与电解液的接触面积大,材料具有较短的Zn²⁺扩散路径,有效提高Zn²⁺的扩散动力学。（3）以NH₄VO₃为钒源,Ca（CH₃COO）₂·H₂O为钙源,通过水热法合成（NH₄）₂V₆O₁₆·1.5H₂O/Ca V₆O₁₆·3H₂O复合材料（NVO/CVO材料）,并通过水热法制备的V₂O₅材料进行电化学性能对比。短片状结构的NVO/CVO材料在2.0 A/g电流密度下循环2000圈放电比容量仍能保持在89.8 m Ah/g。实验证明NVO/CVO复合材料具有丰富的相界面,扩充了锌离子的扩散通道,能有效提高Zn²⁺的扩散动力学、提高材料的容量、倍率性能及循环稳定性能。更多还原

【Abstract】 In recent years,the surge in the demand cost of unrenewable resources such as fossil oil has been affected by the instability of the situation in the Middle East.It is particularly important to maximize the utilization of renewable resources such as solar energy and wind energy.Researchers have paid extensive attention to the conversion of renewable energy into secondary energy storage.The aqueous zinc ion batteries（AZIBs）built on neutral or mild aqueous electrolytes with a zinc plate as the anode,featuring the low cost,good safety and straightforward operation,which became the preferred choice in research.Vanadium has low price,complex valence and diversity of structure.Vanadium-based cathode materials have high theoretical specific capacity and excellent rate performance.They are a kind of cathode materials with widespread application prospects in AZIBs.However,vanadium-based materials arose a series of problems such as unstable material structure,poor conductivity and narrow voltage window in the process of Zn²⁺insertion/extraction,which limits its application in AZIBs.In conclusion,this paper improves the electrochemical stability of the materials by intercalation of metal ions and controllable preparation of composites.The specific contents of research are as follows:（1）（NH₄）₂V₁₀O₂₅·8H₂O material（NVO）was synthesized by hydrothermal method with C₂H₂O₄·2H₂O as reducing agent and NH₄VO₃ as vanadium source.Pre-embedded modification of NVO materials with different Al:V molar ratios（1:3,1:6,1:9）by Al（NO₃）₃·9H₂O as aluminum source.The morphology of Al³⁺pre-embedded materials changed from dense stacked sheet structure to smaller and more dispersed nanosheet structure under the same preparation process.Finely dispersed nanosheets provide fast and convenient diffusion channels for the transmission of Zn²⁺and facilitate the contact between materials and electrolyte.Al-6NVO materials maintains high discharge capacity（252 m Ah/g）after 100 cycles.The discharge capacity of the material can still remain at122.8 m Ah/g after 1200 cycles at 2.0 A/g,and the capacity retention rate is about 94.6%.The diffusion kinetics of Zn²⁺can be effectively improved and the electrochemical performance of the material can be improved due to the synergistic effect of bication NH₄⁺and Al³⁺on the formation of pillar between layers.（2）Na⁺and Ca²⁺co-intercalation V₁₀O₂₄·12H₂O materials（Na,Ca-VOH）were synthesized by hydrothermal method using Na₃VO₄ as vanadium source and anhydrous Ca Cl₂ as calcium source.AZIBs were assembled by using Na,Ca-VOH as anode and commercial zinc foils as cathode.Na⁺(or Ca²⁺)single metal ion pre-embedded V₁₀O₂₄·12H₂O materials were prepared by hydrothermal method.V₁₀O₂₄·12H₂O pure phase materials（VOH）were prepared by aging method.By comparing the electrochemical properties of the four materials,Na,Ca-VOH materials show excellent electrochemical cycle stability.The material maintained a high discharge specific capacity（116.9 m Ah/g）after 500 cycles at a current density of 2.0 A/g,and the capacity retention is about 94.3%.The materials still have 89.0 m Ah/g discharge specific capacity at 5.0 A/g high current density after 1000 cycles,the capacity retention rate is about98.5%.Experiments show that the co-intercalation of Na and Ca metal ions can further expand the layer spacing and improve the stability of the material.The flower structure Na,Ca-VOH material has a large contact area with the electrolyte.The material has a short Zn²⁺diffusion path and effectively improves the diffusion kinetics of Zn²⁺.（3）（NH₄）₂V₆O₁₆·1.5H₂O/Ca V₆O₁₆·3H₂O composites（NVO/CVO materials）were synthesized by hydrothermal method with NH₄VO₃ as vanadium source and Ca（CH₃COO）₂·H₂O as calcium source,and the electrochemical properties ware compared with pure V₂O₅ materials prepared by same method.The NVO/CVO material with short film structure can cycle for 2000 cycles at 2.0 A/g current density,and the specific discharge capacity can still be maintained at 89.8 m Ah/g.The experimental results show that NVO/CVO composites have rich phase interfaces which expand the diffusion channel of zinc ions and effectively improve the diffusion kinetics of Zn²⁺,capacity,rate performance and cycle stability of the materials.更多还原