固态锂空气电池三维多孔正极界面构筑及电化学机理研究

Solid-state lithium-air batteries show great potential to achieve both high energy density and reliable safety. Since the lithium ion conductivity of solid-state electrolyte has been improving, the effective cathode design has become the bottleneck for developing solid-state lithium-air battery. The two-dimensional planar electrode without corresponding optimization toward solid-state battery cannot effectively conduct lithium ion, oxygen and electron and cannot provide fitting space for product storage, which severely discount the volumetric energy density. Herein, we propose the construction of three-dimensional porous cathode by manipulating flexible sacrificial agent and the precise regulation of lithium ion-oxygen-electron “three-phase” interfaces as well as storage spaces fitting the growth size of products, thus realizing large improvement of battery capacity and volumetric energy density. Furthermore, we will promote the catalytic activity of carbon materials by doping heteroatom to enhance oxygen reduction/evolution reaction and/or ameliorate the physicochemical property of products by introducing functional catalyst to break through the limitation of intrinsic low conductivity toward battery capacity. This strategy aims at further improving volumetric energy density, simultaneously reducing the charge overpotential and stabilizing cycling ability. In addition, the transient intermediate products, product growth mechanism and oxidative decomposition process in pore channels of cathode will be carefully explored by in-situ Raman spectrum, transmission electron microscope and differential electrochemical mass spectrometry. The influence of current density and gas component toward electrochemical reaction and battery performance will be studied, which will provide insights into battery application.

固态电解质和锂空气电池的结合使固态锂空气电池具有同时实现高能量密度和可靠安全性的潜力。随着固态电解质离子传导率的提升，制约固态锂空气电池发展的瓶颈逐渐转移至正极。未优化的二维平面电极不能有效传输锂离子、氧气和电子，不能提供合适的产物存储空间，严重损害电池的体积能量密度。本项目利用柔性模板法，构筑具有三维多孔结构的正极，精确调控气（氧气）-固（锂离子传导）-固（电子传导）三相界面，定制预留孔空间，匹配产物的生长尺寸，提升电池容量和体积能量密度。进一步通过元素掺杂提升碳材料催化活性，通过特异性催化剂改变产物的物理化学性质，突破产物原本较低的传导率对电池容量的限制，继续提升体积能量密度，同时降低电池充电电压并改善循环稳定性。利用原位拉曼、透射电子显微和微分电化学质谱技术，获取中间产物瞬态信息，研究产物在孔道中生长和分解机制，理解电流密度和气体组分对电化学反应和电池性能的影响，为电池应用提供指导。

固态锂空气电池兼具高能量密度（~3500 Wh/kg）和高安全优势，是一种非常有潜力的电池技术。本项目针对固态正极反应动力学缓慢问题，进行多级孔结构设计强化传质，引入高效催化剂降低反应能垒。本项目发展了冷冻浇注方法可控构建有序多级孔道结构的固相界面，缩短氧气传输路径，实现了氧气快速传质；基于晶面工程调控策略精准设计了双功能催化剂，发现了光电协同催化效应诱导产物均匀有序成核和生长行为的现象，揭示了产物无定型化转变的生长机制，有效降低了电池充放电过电位，提升了空气环境下电池的容量和循环稳定性。同时，本项目针对负极结构稳定性差问题，优化离子配位环境及界面双电层结构，调控锂金属负极固态电解质界面层组成及柔韧性，提升锂负极的利用效率及稳定性；基于液态金属提出局部电荷传输动力学强化的“自适应”策略，提出分子桥联自组装方法构建层状混合导体表面层，形成一体化高韧性固态电解质界面层，获得高体积容量和高稳定硅负极。本项目的实施为发展固态体系气体催化电极结构设计原则提供了重要的理论依据，同时对锂及硅负极在固态电池中的应用提供了支撑，对推动固态锂空气电池发展具有重要意义。