【作者】 郭涛；

【导师】 魏子栋；

【作者基本信息】 重庆大学 ， 材料与化工（专业学位）， 2024， 硕士

【摘要】 锂氧电池,凭借其高达3600 Wh/kg的超高理论能量密度,被视为下一代能量存储系统中最具潜力的技术之一,尤其在需要大容量能量存储的应用场景中,如电动汽车。然而,尽管其理论潜力巨大,锂氧电池的实际开发和应用仍面临多个技术挑战。这些挑战包括低能量转换效率、倍率性能不足、短循环寿命及安全性问题,这些问题主要源于电极反应动力学的限制和电化学稳定性不足。特别是氧还原反应（ORR）和氧析出反应（OER）的本征动力学缓慢,导致电池在充放电过程中存在较大的过电势,严重影响电池的效率和寿命。为此,研究者们着力于开发新型高效催化剂,以期降低反应的活化能,提高反应速率,从而改善电池的整体性能。针对上述问题,我们在开发新型钌基催化剂以及研究催化反应机理方面进行了研究工作,研究成果如下:（1）第三章我们首先通过在电解液中添加不同浓度的均相催化剂来改善电池性能。该催化剂因其高分散性和高反应活性,在锂氧电池中表现出了优异的电化学性能,尤其是在充放电效率、放电容量、倍率性能及循环寿命方面,相较于传统固态催化剂展现出显著提升。我们接着对均相催化剂在电池充电过程中的作用机理进行了研究,通过弛豫时间分布（DRT）分析方法,我们对充电过程中电池阻抗的变化进行了深度剖析,明确了锂氧电池充电过电位产生的原因。通过我们对电池反应机理的研究发现,进一步的研究表明,均相催化剂能够直接在放电产物表面催化电化学反应,提升放电产物的导电性,减少电池反应的极化电压,从而显著提高了电池的循环稳定性。（2）第四章我们通过溶胶凝胶法合成均匀的纳米二氧化硅作为模版,制备出大孔负载钌的氮掺杂多孔碳催化剂。实验结果显示,钌纳米粒子均匀分散在氮掺杂多孔碳表面,表明采用的合成方法能有效控制纳米粒子的尺寸和分散性。将Ru NCs纳米催化剂作为锂氧电池正极材料,在100 mA g^-1的电流密度下进行深度充放电,其比容量高达16725 mAh g^-1,并且充放电极化电压仅有0.5 V。在截止容量循环测试中,最高稳定循环196圈,其电池性能明显优于其他样品,充分证明了Ru NCs纳米催化剂在促进氧还原反应、提高电池的循环稳定性方面的显著效果。本研究成功开发的Ru NCs纳米电催化剂不仅在ORR性能上表现出色,而且在锂氧电池的实际应用中展现优异的电化学性能和循环稳定性,为锂氧电池的发展提供新的材料选择和技术方向。更多还原

【Abstract】 Lithium-oxygen batteries,with their impressively high theoretical energy density of up to 3600 Wh/kg,are regarded as one of the most promising technologies for next-generation energy storage systems,particularly in applications requiring large-capacity energy storage such as electric vehicles.However,despite their enormous theoretical potential,the practical development and application of Lithium-oxygen batteries still face numerous technical challenges.These challenges include low energy conversion efficiency,insufficient rate performance,short cycle life,and safety issues,primarily due to limitations in electrode reaction kinetics and insufficient electrochemical stability.Specifically,the intrinsic kinetics of the oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）are slow,resulting in significant overpotentials during charging and discharging processes,which severely impact the efficiency and lifespan of the batteries.To address these issues,researchers have focused on developing novel,efficient catalysts to reduce the activation energy of reactions,thereby enhancing the reaction rate and overall performance of the batteries.In response to these challenges,we have conducted research on the development of new ruthenium-based catalysts and the study of catalytic reaction mechanisms,with the following findings:（1）In Chapter 3,we initially improved battery performance by adding different concentrations of homogeneous catalysts to the electrolyte.This catalyst,due to its high dispersibility and high reactivity,exhibited excellent electrochemical performance in Lithium-oxygen batteries,particularly in terms of charging and discharging efficiency,discharge capacity,rate performance,and cycle life,showing significant improvement over traditional solid-state catalysts.We then studied the mechanism of action of the homogeneous catalyst during the battery charging process.Using the distribution of relaxation times（DRT）analysis method,we conducted a deep analysis of the changes in battery impedance during the charging process,clarifying the cause of the overpotential generated during Lithium-Oxygen battery charging.Our research into the battery reaction mechanism revealed that the homogeneous catalyst could directly catalyze the electrochemical reaction on the surface of the discharge product,enhancing the conductivity of the discharge product,reducing the polarization voltage of the battery reaction,and thereby significantly improving the cycle stability of the battery.（2）In Chapter 4,we successfully synthesized uniform nanosilica as a template through the sol-gel method,and prepared large-pore nitrogen-doped honeycomb carbon catalysts,finally loading ruthenium particles on the honeycomb carbon via homogeneous precipitation.The experimental results showed that ruthenium nanoparticles were uniformly dispersed on the surface of nitrogen-doped honeycomb carbon,indicating that the adopted synthesis method could effectively control the size and dispersion of nanoparticles.Using Ru NCs nanocatalysts as the cathode material for Lithium-oxygen batteries and performing deep charge-discharge tests at a current density of 100 mA g^-1,the specific capacity reached up to 16725 mAh g^-1,and the charge-discharge polarization voltage was only 0.5 V.In the cutoff capacity cycling test,the batteries achieved a stable cycle life of up to 196 cycles,significantly outperforming other samples,fully demonstrating the remarkable effect of Ru NCs nanocatalysts in promoting the oxygen reduction reaction and improving the cycle stability of the battery.The Ru NCs nanoelectrocatalysts developed in this study not only exhibited excellent performance in ORR but also demonstrated outstanding electrochemical performance and cycle stability in the practical application of Lithium-oxygen batteries,providing new material choices and technical directions for the development of Lithium-oxygen batteries.更多还原