Battery Cathodes with Optimized Interfacial Stability Through the Tailored Design of Core-Shell Architectures

可充电锂离子电池通过存储风能和太阳能等间歇性可再生能源产生的电力，或为使用可再生能源充电的零排放电动汽车提供动力，有助于实现可持续能源系统。然而，锂离子电池的性能在重复充电循环中会下降，因为在电池电极和电解质之间的边界会发生不必要的反应。这个项目将开发新的电极材料来防止这些不必要的反应。关键的创新是在锂基储能材料的纳米级晶体上覆盖一层非常薄的其他材料，这些材料可以阻止这些不希望发生的反应，但保持性能。涂层均匀地涂在所有的纳米晶体上，因此当晶体形成电极时，涂层中没有缝隙。与此项目相关的教育活动包括指导本科生进行暑期研究，并向芝加哥地区的高中生推广。外展活动的目标是向芝加哥地区不同群体的高中生传达现代社会中储能技术的价值，并鼓励这些学生在STEM领域接受教育和职业。这项研究的总体目标是通过最大化界面稳定性来提高锂离子电池阴极承受极端循环环境的能力，同时不牺牲能量存储容量、电力输送和充电时间。阴极电解质的不稳定性与电极表面的电活性过渡金属的存在有关。这些不稳定性导致这些界面发生不可逆的转变，形成绝缘层，阻碍传输以及由于腐蚀造成的材料损失。核壳架构可以解决界面不稳定性问题。壳层将富含非活性铝离子，使界面上的不可逆转变最小化，而芯层将由具有高电荷存储能力的活性过渡金属氧化物（Mn, Ni, Co）组成。此外，外壳将变薄以减少存储容量损失，并符合所有接口的钝化。为了对这些核壳阴极材料保持电极稳定性的能力有一个基本的了解，研究计划有三个目标。第一个目标是为高电压、高能电池阴极制造核心外延壳纳米晶体。第二个目标是在二级粒子水平上设计和评估核壳结构，第三个目标是构建完整的锂离子电池并表征其操作界面机制。作为这项研究的一部分，将开发合成和制造工具，以有效地用定制材料覆盖所有界面，并创建集成的阴极结构，在该结构中，适当水平的电子和离子传输被赋予。

Rechargeable lithium ion batteries help to enable sustainable energy systems by storing electricity generated by intermittent renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. However, the performance of lithium ion batteries degrades over repeated recharging cycles because of unwanted reactions that occur at the boundary between the battery electrode and the electrolyte. This project will develop new electrode materials for preventing these unwanted reactions. The key innovation is to coat nanoscale crystals of the lithium-based energy storage material with a very thin layer of other materials that are tailored to block these undesired reactions but maintain performance. The coating is uniformly applied to all the nanocrystals, and so that when the crystals are formed into an electrode, there are no gaps in the coating. The educational activities associated with this project involve mentoring of undergraduate students for summer research, and outreach to high school students in the Chicago area. The goals of the outreach activities are to communicate the value of energy storage technology in modern society to diverse groups of high school students in the Chicago area, and to encourage these students to pursue education and careers in STEM fields. This overall goal of this research is to improve the ability of lithium ion battery cathodes to withstand extreme cycling environments by maximizing interfacial stability without sacrificing energy storage capacity, power delivery, and recharging time. Cathode-electrolyte instabilities have been linked to the presence of electroactive transition metals at the surface of the electrode. These instabilities result in irreversible transformations at these interfaces, with formation of insulating layers that impede transport as well as material loss due to corrosion. Core-shell architectures can address interfacial instability. The shell will be rich in inactive aluminum ions that minimize irreversible transformations at the interface, and the core will be composed of active transition metal oxides (Mn, Ni, Co) with high charge storage capacity. Furthermore, the shell will be thin to reduce storage capacity loss, and conformal to passivate all interfaces. To gain a fundamental understanding of the ability these core-shell cathode materials to maintain electrode stability, the research plan has three objectives. The first objective is to fabricate core-epitaxial shell nanocrystals for high voltage, high energy battery cathodes. The second objective is to design and evaluate core-shell architectures at the secondary particle level, and the third objective is to construct of full lithium ion cells and characterize of their interfacial mechanisms of operation. As part of this research, synthesis and fabrication tools will be developed to effectively coat all interfaces with tailored materials and create integrated cathode architectures where appropriate levels of electron and ion transport are imparted.