Functionalized Si/SiNx Nanoparticles as Anodes for High-Performance Lithium-Ion Batteries: Gas-phase synthesis, Structural and Electrochemical Investigation

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Generally, nano-Si-based anode materials are considered highly promising for high-performance lithium-ion batteries (LIBs). In preliminary studies, multi-functional Si/SiNx nanostructures showed promising capabilities to overcome critical issues of Si-based anodes, namely their structural and electrochemical instabilities. So far, however, Si/SiNx anodes have not been realized. This is due to the unavailability of processes that generate sufficient amounts of materials with targeted properties. Based on the established hot-wall reactor technique for the synthesis of Si nanoparticles it is expected that gas-phase synthesis enables the generation of Si/SiNx nanoparticles in the required quality and quantity. The overall goal of this project is to investigate the formation of Si/SiNx nanoparticles by scalable gas-phase synthesis and to study their electrochemical properties as anodes for LIBs. This includes two main tasks: Understanding the synthesis-conditions - materials-characteristics correlation and understanding the materials-characteristics - electrochemical-performance correlation. To fulfil the first task, systematic experiments will be carried out to study how synthesis parameters such as NH3/SiH4 ratio, temperature, and residence time determine the phase composition and the particle size of the Si/SiNx nanoparticles. The second task requires the synthesis and investigation of a series of Si/SiNx materials with well-defined characteristics. These materials will be implemented in LIB anodes for electrochemical tests to reveal how their characteristics influence the battery performance in terms of capacity, Coulombic efficiency, cycling stability, and charging rate-capability. The structure and the composition evolution on the Si/SiNx anodes at different cycling stages will be analyzed by various methods, including in situ synchrotron XRD in collaboration with the Argonne National Laboratory. As results, optimized materials including scalable synthesis and processing methods will be developed in an iterative way in this project.