【作者】 王悦；

【导师】 徐吉静；

【作者基本信息】 吉林大学 ， 无机化学， 2022， 硕士

【摘要】 可充电锂氧电池由于其超高的理论能量(3,500 Wh kg^-1),成为最有潜力的下一代储能电池。然而在锂氧电池的实际应用过程中面临着许多挑战:缓慢的ORR/OER动力学导致往返能量效率低、电化学不稳定导致循环性能差、负极枝晶和腐蚀带来安全隐患。氧化还原介体（RMs）作为一种可溶性催化剂应用于有机系锂氧电池,可有效提升ORR/OER动力学,降低充放电反应过电位。不幸的是,RMs在电解液中的穿梭效应通常会导致锂金属负极的腐蚀,导致RMs的不必要消耗和电池的劣化。针对上述问题,我们研究了抑制氧化还原介体穿梭的方法和其催化反应机制,取得的成果如下:首先将导电吡咯单体（Py）与氧化还原活性分子4-羟基-2,2,6,6-四甲基哌啶-1-基氧基（4-OH-TEMPO）接枝成单体4-（3-（吡咯-1-基）丙酰氧基）-2,2,6,6-四甲基哌啶-1-基氧基（Py-TEMPO）,通过原位电化学沉积的方法在三维导电阵列上聚合,成功制备出固定化氧化还原活性导电正极,将其应用于锂氧电池中,展现出优异的电化学性能。原位合成的氧化还原正极（Zn O@C@PPy-TEMPO/NF）具有高导电率、高比表面、高活性位点,有益于电子、锂离子的快速传递,同时保留了TEMPO的氧化还原活性,大大降低了电池的充电电位,改善了锂氧电池倍率性能和循环稳定性。探究了固定化TEMPO在锂氧电池中充放电机理以及对负极的保护。放电过程中,由于Li⁺和聚吡咯基底通过cation-π作用形成大量强吸附中心和成核位点,使得反应中间体Li O₂难以脱落,从而在纳米棒表面均匀地生成Li₂O₂纳米片,实现放电产物的同型生长。充电过程中,TEMPO被正极上沿着导电PPy长链传递的电子电化学氧化为TEMPO⁺,锚定的TEMPO⁺从下到上分解三维阵列上同型生长的纳米片状Li₂O₂,获得优异的充电效率。由于TEMPO的穿梭效应被抑制,因此减轻了锂负极的腐蚀,提升了锂氧电池性能。本工作对抑制氧化还原介体穿梭以及研究固定化正极催化机理有重要借鉴意义。更多还原

【Abstract】 Rechargeable lithium-oxygen batteries have become the most potential energy storage batteries for the next generation due to their ultra-high theoretical energy(3,500 Wh kg^-1).However,many challenges are faced in the practical application of lithium-oxygen batteries:slow ORR/OER kinetics lead to low round-trip energy efficiency,electrochemical instability leads to poor cycling performance,anode dendritic and corrosion brings safety hazards.Redox mediators（RMs）,as soluble catalysts used in organic lithium oxygen batteries,can effectively improve ORR/OER kinetics and reduce the overpotentials of charge and discharge reaction.Unfortunately,the shuttling effect of RMs in the electrolyte solution usually causes corrosion of the lithium metal anode,resulting in unnecessary consumption of RMs and deterioration of the battery.In view of the above problems,we investigated the method to inhibit the redox mediator shuttle and its catalytic reaction mechanism,and the results obtained are as follows:First,the conductive pyrrole monomer（Py）was fiest grafted with the redox active molecule 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy（4-OH-TEMPO）into a monomer4-（3-（pyrrol-1-yl）propionyloxy）-2,2,6,6-tetramethylpiperidin-1-yloxy（Py-TEMPO）,which was polymerized on the three-dimensional conductive array by in-situ electrochemical deposition,and the immobilized redox active conductive cathode was successfully prepared,which was applied to lithium oxygen batteries and exhibited excellent electrochemical performance.The in-situ synthesized redox cathode（Zn O@C@PPy-TEMPO/NF）has high conductivity,high specific surface,and high active sites,which is conductive to the rapid transfer of electrons and Li⁺while retaining the redox activity of TEMPO,which significantly reduces the charging overpotential of the battery,and improves the doubling performance and cycle stability of the lithium oxygen battery.The charging and discharge mechanism of immobilized TEMPO in the lithium oxygen battery and the protection of the Li anode were explored.During the discharge process,due to the formation of a large number of strong adsorption centers and nucleation sites by Li⁺and the polypyrrole substrate through the cation-πinteraction,making the reaction intermediate Li O₂difficult to fall off,whereby generating Li₂O₂nanosheets uniformly on the nanorod surface and achieving isomorphic growth of the discharge product.During the charging process,TEMPO is electrochemically oxidized to TEMPO⁺by electrons transported along the long conductive PPy chains on the cathode,and the anchored TEMPO⁺decomposes the nanosheet Li₂O₂grownon the 3D array from bottom to top,resulting in excellent charging efficiency.Since the shuttle effect of TEMPO is suppressed,the corrosion of the lithium anode is alleviated and the performance of the lithium-oxygen battery is improved.This paper has important reference significance for inhibiting redox-mediated shuttling and studying the catalytic mechanism of immobilized cathodes.更多还原