【作者】 王晓；

【导师】 姜银珠；

【作者基本信息】 浙江大学 ， 材料科学与工程， 2020， 硕士

【摘要】 当前,发展可再生能源、推动电网智能化已成为能源领域的重要方向,作为平衡能源供给和消费的关键环节,电化学储能技术受到了广泛关注。钠离子电池具有与锂离子电池相似的工作原理,显著的资源和成本优势促使其有望在规模储能领域实现广泛应用。开发高性能正极材料对于钠离子电池的发展与应用至关重要。作为一类三维开框架结构材料,普鲁士蓝类似物可以实现钠离子可逆脱嵌,具有较高的理论比容量和工作电位。同时,资源丰富、合成简便和环境友好等优势使得其在钠离子电池中具有很好的应用前景。本文围绕普鲁士蓝类似物中极具应用前景的Na₂MnFe（CN）₆（MnHCF）和Na₂FeFe（CN）₆（FeHCF）两类材料展开了研究,通过PEDOT导电聚合物包覆提升了MnHCF的循环和倍率特性,结合合成温度和反应液成分调控实现了富钠FeHCF的制备。主要工作总结如下:（1）MnHCF具有组成元素资源丰富、工作电位高、富钠结构易得等显著优势。然而,其差的电子导电性导致了严重的电化学极化问题,同时在电化学循环过程中存在相变和过渡金属溶出等问题,造成电极循环性能较差。针对以上问题,本文通过原位聚合法成功制备了MnHCF@PEDOT复合材料,一方面抑制了循环过程中的相变和过渡金属溶出,另一方面促进了电容存储行为,实现了循环和倍率性能的显著提升。MnHCF@PEDOT在0.1 C时比容量高达147.9 mAh g^-1,在20 C大倍率条件下仍保持90.2 mAh g^-1,在10 C倍率1000次循环后,容量保持率达78.2%。甚至在-10℃的低温下,MnHCF@PEDOT仍可提供87.0 mAh g^-1的高比容量,500次循环后仍保持82.2%。（2）FeHCF作为钠离子电池正极材料普遍存在初始钠含量低的瓶颈问题。本文系统研究了反应液中合成温度、NaCl浓度等对FeHCF初始钠含量、形貌、结构和循环性能的影响。结果表明,提升合成温度有助于降低样品的缺陷含量、提升初始钠含量。在100℃、1 mol L^-1 NaCl添加的条件下实现了富钠FeHCF制备,其分子式为Na_1.89Fe[Fe（CN）₆]_0.93□_0.07·2.31H₂O(□代表[Fe（CN）₆]^4-空位),充放电比容量分别为160.3和146.6 mAh g^-1。更多还原

【Abstract】 In recent years,electric energy storage technology has received extensive attention due to the rapid development of renewable energy and smart grid.Among various candidates,sodium ion batteries（SIBs）are attracting increasing attention as a complement or an alternative to lithium ion batteries（LIBs）in the applications of large-scale energy storage systems（ESSs）because of the the practically inexhaustible,ubiquitous and low-cost sodium resources as well as the similar“rocking-chair”mechanism as LIBs.High-performance cathode materials are crucial for the development of SIBs,among which Prussian blue analogues（PBAs）possess the advantages of abundant resources,ease of synthesis and environmental friendliness.Furthermore,given the unique three-dimensional channels structure of PBAs,the reversible extraction-insertion of sodium ions is accessible,enabling a high theoretical capacity and thus exhibiting a good application prospect in SIBs.This thesis focuses on the promising materials of PBAs,including Na₂MnFe（CN）₆（MnHCF）and Na₂FeFe（CN）₆（FeHCF）.The specific research contents are as follows:（1）MnHCF is desirable because of its high working voltage,high specific capacity,as well as its abundant element resources and easy preparation of sodium-rich structure.However,MnHCF as cathode material suffers from poor cycling stability and unsatisfactory rate capability due to inferior intrinsic conductivity,phase transition and transition metals dissolution,extremely limiting its practical application.To solve above issues,the MnHCF@PEDOT composites were successfully prepared by a facile in-situ polymerization method.On one hand,the phase transition and transition metals dissolution are greatly suppressed,thus rendering the prolonged cycle life.On the other hand,the capacitance storage behavior is also enhanced,enabling the improved rate performance.Consequently,the composite exhibits a high capacity of 147.9 mAh g^-1 at0.1 C,90.2 mAh g^-1 at a high rate of 20 C,and 78.2%capacity retention after 1000cycles at 10 C.Furthermore,even at a low temperature of-10℃,MnHCF@PEDOT still delivers a high capacity of 87.0 mAh g^-1 and maintains 82.2%after 500 cycles.（2）FeHCF as a cathode material for SIBs generally has a bottleneck problem of low initial sodium content.FeHCF with different initial sodium contents,micromorphologies and properties were synthesized by controlling the synthesis temperature and the amounts of NaCl addition.Specifically,FeHCF exhibits decreared defects and increased sodium contents along with the enhancement of synthesis temperature.Furthermore,the electrochemical performance of FeHCF is optimal when the amount of NaCl added is 1 mol L^-1.Finally,sodium-rich FeHCF with the formula of Na_1.89Fe[Fe（CN）₆]_0.93□_0.07·2.31H₂O(□stands for the[Fe（CN）₆]^4-vacancies)was obtained under the condition of 100℃and 1 mol L^-1 NaCl,with charge and discharge specific capacities of 160.3 and 146.6 mAh g^-1.更多还原