【作者】 王立；

【导师】 袁凯； 陈义旺；

【作者基本信息】 南昌大学 ， 化学， 2022， 博士

【摘要】 锌离子电容器（Zinc ion capacitors,ZICs）是一种新兴可持续的电化学能源存储器件,集成了水系锌离子电池（Zinc ion batteries,ZIBs）高能量密度和超级电容器（Supercapacitors,SCs）高功率密度的优点。然而,金属Zn负极和电容型正极的动力学和容量不匹配、碳质正极材料比容量低、倍率性能差、活性位点利用率低、循环寿命不理想等问题仍然是该技术的致命弱点。本论文主要围绕ZICs存在的问题与挑战,基于碳质正极材料的设计和制备,通过对材料比表面积,孔结构,缺陷以及杂原子的调控,显著提升了材料的电化学性能。其次,结合系列非原位测试以及原位电化学石英晶体微天平（Electrochemical quartz crystal microbalance,EQCM）和原位拉曼光谱等原位测试技术重点阐释了材料的储能机理,提出了双电层电容（Electrical double-layer capacitance,EDLC）和氧化还原的耦合机制,双离子吸附和可逆化学吸附协同机理。最后提出了通过消除材料的微孔限域效应实现材料孔尺寸与载流子的良好匹配、提高材料活性位点利用率,以及发现了Zn²⁺,H⁺和SO₄^2-的共吸附机制与可逆化学吸附的协同作用提升Zn²⁺存储能力。针对水系ZICs面临的问题和挑战,本论文在关键正极材料设计、材料结构和组成的调控、正负极材料动力学匹配及储能机理等几方面展开了研究,成功构筑了高性能水系ZICs储能器件。具体研究内容如下:1、碳质正极材料不能有效匹配锌负极的高理论容量,导致ZICs电化学性能较差。本文通过原位自活化的策略构建了氧功能化分级多孔碳材料（HPC）。优化的HPC-600材料具有较高的比表面积、合适的孔结构、丰富的缺陷和含氧官能团,为Zn²⁺存储提供了丰富的活性位点。因此,构筑的ZICs表现出优异的电化学性能(可逆比容量高达169.4 mAhg^-1,能量密度为125.1 Whkg^-1,功率密度为16.1 k W kg^-1)和良好的循环稳定性（60000次循环容量保持率93.1%）。系统的机理研究表明,在充/放电过程中,多孔碳高容量和高能量密度来源于EDLC和氧官能团可逆转化所产生赝电容的协同作用。2、碳质正极材料与锌负极在容量和动力学方面的良好匹配是实现高能量和高功率密度ZICs的关键。本文通过引入不同离子尺寸和反应活性的碱金属离子（Li⁺,Na⁺,K⁺,Rb⁺,和Cs⁺）对材料进行刻蚀,从而实现了材料比表面,孔径尺寸、氧含量以及材料缺陷的有效调控。优化的Rb PC展示出较高的比表面积,丰富的多孔结构,大量的缺陷和丰富的活性位点暴露,以及良好的浸润性和电导率。因此,Rb PC表现出与金属Zn负极更好的匹配性。构筑的ZICs表现出优异的电化学性能,较高能量密度(178.2 Whkg^-1)和功率密度(72.3 k W kg^-1)。此外,通过系列的非原位表征和原位EQCM测试研究表明材料优异的电化学性能归因于双离子吸附(Zn²⁺和CF₃SO₃^-分别在不同的电压区间被吸附)和可逆的化学吸附（氧官能团参与化学反应形成-C-O-Zn键增加容量贡献）的耦合机制。3、研究表明,[Zn（H₂O）₆]²⁺为充/放电过程中主要的载流子,但其较大的离子尺寸限制了其在更小尺寸的孔中存储。孔结构与载流子尺寸不匹配现象称之为微孔限域效应。本文通过消除微孔限域效应,同时提升活性位点利用率,为提高活化氮掺杂分级多孔碳材料（ANHPC-x）的Zn²⁺存储能力提供了新思路。通过简单的活化策略调控了材料比表面积、孔径尺寸、活性位点和氧官能团,实现了材料孔尺寸与载流子的良好匹配,并且显著提高了材料活性位点密度和利用率。碳质正极材料的分级多孔结构为[Zn（H₂O）₆]²⁺提供了更多的传输通道,缩短了离子传输距离,减小了传输阻力,实现了超快的Zn²⁺储存。构筑的ZICs展现出良好的电化学性能(比容量199.1 mAhg^-1,高能量密度155.2 Whkg^-1,和高功率密度为41.4 k W kg^-1)和超长的循环寿命（65000次）。进一步通过系列非原位表征、原位EQCM和原位拉曼光谱测试表明材料优异的电化学性能归因于Zn²⁺,H⁺和SO₄^2-的共吸附机制和可逆化学吸附的协同作用。更令人鼓舞的是,构筑的准固态ZICs也展示出优异的电化学性能,良好的机械稳定性和100000次的超长循环寿命。更多还原

【Abstract】 Zinc-ion capacitors（ZICs）,as an emerging hybrid device that inherit the advantageous characteristics of high energy of ZIBs and high power of supercapacitors,have attracted extensive attention.However,the mismatch of kinetics and capacity between Zn anode and capacitive-type cathode,worse Zn²⁺storage capability,poor rate performance,the low utilization of active sites and unsatisfactory cycle life are still the Achilles’heel of this technology.This thesis focuses on the problems and challenges of ZICs,and based on the design and preparation of carbonaceous cathode materials,which significantly improve the electrochemical performance of the materials by the regulation of specific surface area（SSA）,pore structure,defects and heteroatoms of material.Secondly,the energy storage mechanism of the materials in electrochemical reactions.Systematic ex-situ characterization analysis coupled with in-situ electrochemical quartz crystal microbalance and Raman spectra measurements testify that the energy storage mechanism of the materials,including the coupling mechanism of electric double-layer capacitance and redox reaction of oxygen functional groups,the dual ion adsorption and reversible chemical adsorption.Finally,it is proposed to achieve a good match between material pore size and carrier by eliminating the microporous domain-limiting effect of the material,to improve the active site utilization of the material,and to identify a co-adsorption mechanism of Zn²⁺,H⁺and SO₄^2-with reversible chemisorption to synergistically enhance the Zn²⁺storage capability.This thesis addresses the problems and challenges faced by aqueous ZICs,and successfully constructs high-performance aqueous ZICs energy storage devices by investigating the design of positive materials,the regulation of material structure and composition,the kinetic matching of positive and negative materials,and the energy storage mechanism.The details are as follows:1.The carbon cathode material cannot effectively match the high theoretical capacity of the Zn cathode,resulting in worse electrochemical performance of ZICs.Herein,we report the fabrication of oxygen functionalized hierarchical porous carbon（HPC）materials by direct annealing of potassium citrate and used for ZICs.The material structure and oxygen functional groups can be efficiently regulated by adjusting the pyrolysis temperature.The porous carbon material affords more Zn²⁺adsorption/desorption sites by the high SSA and the suitable pore structure promotes the ions fast transport.Additionally,oxygen functional groups,especially the hydroxyl group of HPC-600 can effectively boost the chemical adsorption of Zn²⁺.Therefore,HPC-600-based ZIC demonstrates prominent electrochemical properties,with specific capacity as high as 169.4 mAhg^-1 at current density of 0.1 A g^-1 and impressive specific energy of 125.1 Whkg^-1.Even at a high specific current of 20 A g^-1,the HPC-600 can still achieve high specific capacity and power density of 97.6 mAhg^-1 and 16.1 k W kg^-1,respectively.Moreover,the corresponding quasi-solid ZICs also exhibit satisfactory rate properties and high cyclic stability.Furthermore,the ex-situ mechanism investigation deciphering that the outstanding electrochemical characteristics are stem from the synergically contribution of the electric double-layer capacitance（EDLC）of porous carbon and pseudocapacitances of oxygen functional groups reversible transformation.2.A good match in capacity and kinetics between carbon cathode materials and zinc cathodes is essential for the construction of high energy/power densities ZICs.Herein,the tetra-alkali metal pyromellitic acid salts（PMA4M,M=Li,Na,K,Rb,and Cs）were used as precursors to prepare porous carbons via a carbonization/self-activation procedure.The optimized rubidium activated porous carbon（Rb PC）demonstrates affluent defect-rich graphitic tissue,high SSA of 1527.7 m² g^-1,hierarchical porous structure and high oxygen doping of 6.02 at%.Benefiting from the advantageous features,the Rb PC-based ZICs delivered excellent electrochemical performance with high energy density(178.2 Whkg^-1)and power density(72.3 k W kg^-1).Meanwhile,the Rb PC-based quasi-solid-state ZIC holds particular promise for serving as energy storage components for wearable electronics.Systematic ex-situ spectral investigations in combination with in-situ electrochemical quartz crystal microbalance experiments certify that the remarkable electrochemical capability is ascribed to the synergistic effect of dual-ion adsorption and reversible chemical adsorption of Rb PC.The numerous lattice defects providing a multitude of sites for the adsorption of Zn²⁺and CF₃SO₃^-,which exhibit outstanding capacitive kinetics.Moreover,the strong interaction between oxygen functional groups and Zn ion resulting in affluent redox-active pseudocapacitance further boost the ZICs electrochemical capability.3.Acknowledgedly,[Zn（H₂O）₆]²⁺,as the main solvation structure with a large ion size of 0.86 nm,is identified as the primary charge carriers for ZICs during charge/discharge processes.Due to the micropore confinement effect（the mismatch between pore size and Zn hydrate ion）,the large ion size of[Zn（H₂O）₆]²⁺is difficult to access the deep micropores of the microporous-based carbon materials,resulting in a severe loss of space utilization and poor Zn²⁺storage capability.Herein,we provide new insights to boost the Zn²⁺storage capability of activated nitrogen-doped hierarchical porous carbon materials（ANHPC-x）by effectively eliminating micropore confinement effect and synchronously enhancing the utilization of active sites.The optimized ANHPC-2 displays a SSA as high as 3553.1 m² g^-1,suitable pore size,sufficient active sites,and abundant oxygen functional groups,thus favorable for promoting the chemical adsorption and accelerating the kinetics of Zn²⁺storage.Importantly,the more matchable pore size can be favorable to improve the accommodation of[Zn（H₂O）₆]²⁺charge carriers,leading to excellent capability of Zn²⁺storage.Consequently,the as-fabricated ZIC with ANHPC-2 cathode delivers a specific capacity as high as 199.1 mAhg^-1,high energy density(155.2 Whkg^-1),high power density(41.4 k W kg^-1),and excellent cycling stability（99.1%capacity retention over65000 cycles）.Systematic in situ electrochemical quartz crystal microbalance（EQCM）and Raman spectra measurements testify that the excellent electrochemical properties are attributed to the synergistic effect of the Zn²⁺,H⁺,and SO₄^2-co-adsorption mechanism and reversible chemical adsorption.More encouragingly,the quasi-solid-state ZIC demonstrates superior rate property,favorable mechanical stability,and ultralong lifespan up to 100 000 cycles with 98.8%capacity retention.更多还原