Functional Carbon Surfaces for Stable Passivation of Sodium-Ion Battery Electrodes

像风能和太阳能这样的间歇性可再生能源需要大规模的、具有成本效益的能源储存方法。目前还没有一种技术能够以可接受的安全性、寿命和成本提供如此多的能量存储。与锂离子电池相比，可充电钠离子电池具有丰富的资源和更低的原材料成本，在大规模储能方面更有前景。然而，目前钠离子技术的寿命受到电池内部固体和液体材料之间低效界面的限制。在固态和材料化学项目的支持下，该项目将更好地理解这种界面化学。研究结果将使研究人员能够设计出使用寿命更长的材料，并比传统方法更快地预测这些材料的使用寿命。该项目的教育效益包括在电分析化学、电池科学、微制造和反应器设计方面对研究生和本科生的研究人员进行培训。PI还与当地一所高中的“编程女孩”分会合作，向高中生介绍电子和工程设计。技术描述固体电解质界面（SEI）（电极/电解质界面的表面膜）钝化不足限制了钠离子电池的寿命。即使是对SEI如何形成、生长和传输电荷的基本理解也严重缺乏。这项工作将应用微流控反应器，电化学发生器-收集器实验和氧化还原介质研究的创新组合，以开发对SEI形式和功能的关键见解的方法。减少反应器体积模拟了真实电池的表面体积比，而定义良好的对流场仍然适用于运输和动力学分析。这种非常规的方法控制了电解质降解反应的停留时间，并可用于将钝化效率映射到溶解的低聚物的浓度和链长。微流反应器还允许电化学发生器-收集器实验，以安培法检测反应产物。这种四电极测量在普通电池中是不可能的，它将允许对可溶性降解产物进行安培检测，并对SEI中的电荷传输和反应进行介质研究。模型几何图形的碳质电极将通过控制氧化热解光刻胶来合成。这些电极将在光谱和微观上进行表征，以便将它们的电化学性能与碳表面的性质联系起来。这项研究的结果将影响现有的和新兴的钠离子电池材料，通过确定如何使用碳表面化学来控制所需SEI产物的催化作用及其有效沉淀成稳定的薄膜。

Non-technical DescriptionIntermittent renewable energy sources like wind and solar require large-scale, cost-effective methods for energy storage. There is currently no technology that could provide this amount of energy storage with acceptable safety, lifetime, and cost. Rechargeable sodium-ion batteries are more promising than lithium-ion batteries for large-scale storage based on their earth-abundant resources and lower raw material cost. However, the lifetime of current sodium-ion technology is limited by inefficient interfaces between solid and liquid materials inside the battery. With the support of the Solid State and Materials Chemistry program, this project will develop better understanding of this interfacial chemistry. The results will allow researchers to design materials that last longer and to predict the lifetime of those materials much faster than traditional methods. The educational benefits of the project include graduate and undergraduate researcher training in electroanalytical chemistry, battery science, microfabrication, and reactor design. The PI has also partnered with a local high school's chapter of Girls Who Code to introduce high school students to electronics and engineering design.Technical DescriptionInsufficient passivation from the Solid Electrolyte Interphase (SEI), a surface film at the electrode/electrolyte interface, limits the lifetime of sodium-ion batteries. Even basic understanding of how the SEI forms, grows, and transports charges is severely lacking. This work will apply an innovative combination of microfluidic reactors, electrochemical generator-collector experiments, and redox mediator studies in order to develop methods for critical insight into the form and function of the SEI. Reducing reactor volume mimics the surface:volume ratio of a real battery while the well-defined convection field is still amenable to transport and kinetic analysis. This unconventional approach controls the residence time of the electrolyte degradation reactions and can be used to map passivation efficiency to the concentration and chain-length of solubilized oligomers. The microflow reactor also permits electrochemical generator-collector experiments to amperometrically detect reaction products. Such four-electrode measurements are not possible in a normal battery and will permit the amperometric detection of soluble degradation products and mediator studies of charge transport and reaction in the SEI. Patterned carbonaceous electrodes in model geometries will be synthesized by controlled oxidation of pyrolyzed photoresist. These electrodes will be characterized spectroscopically and microscopically in order to relate their electrochemical performance to the nature of the carbon surface. The results of the study will impact both existing and emerging materials for sodium-ion batteries by determining how carbon surface chemistry can be used to control both the catalysis of desirable SEI products and their effective precipitation into stable films.