Developing sustainable synthetic routes to lithium-ion battery electrodes

NMC-type cathodes (Li1+xNi1-x-y-zMnyCozO2) have replaced lithium cobalt oxide (LiCoO2) in several commercial battery applications, due to the higher energy density and lower cost of their reduced cobalt (Co) content. Yet, the synthesis of these materials is commonly achieved via a solid-state route, generally involving two high-temperature (~1000°C) calcination steps of about 15 hours each. Microwave (MW) synthesis obviates the need for this high energy and inefficient convective heating route by selectively, uniformly, and rapidly heating the sample. Compared to the conventional solid-state calcination, MW synthesis is reliable, cheap, and energy/time-efficient. As such, this project aims to develop a MW synthesis protocol for NMC-type cathodes, and to investigate differences in the structure and batteryperformance between electrodes synthesized via MW and conventional routes. Phase purity and composition of the samples will be assessed with X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. The microstructure and morphology of the electrode particles will be examined using scanning electron microscopy (SEM). Moreover, solid-state nuclear magnetic resonance (ss-NMR) and electron paramagnetic resonance (EPR) experiments will be conducted to identifythe effect of MW vs. convective heating on the local structure of the cathodes. Ex-situ and operando ss-NMR and EPR experiments can probe changes in the local structure of these cathodes as a function of state of charge; such changes can be directly related to the specific energy density, voltage and capacity fade, and efficiency. These identified structure-property relationships and synthesis development will conceivably lead to cheaper and more energy-efficient lithium-ion batteries.