High-Throughput Synthesis of Size-Controlled Nanoparticles for Lithium Ion Battery using Tandem-Coil Modulated Induction Thermal Plasmas

High-capacity silicon nanoparticles (Si NPs) are promising anode materials for next-generation lithium-ion batteries, but practical use requires both high-throughput production and controllable particle size. This study investigates whether millisecond-scale waveformengineering of the lower-coil current in a tandem-coil modulated induction thermal plasma with time-controlled feedstock feeding (Tandem-MITP+TCFF) can control Si NP formation. A coupled numerical model consisting of electromagnetic thermofluid dynamics, Lagrangian feedstock tracking, and aerosol kinetics clarifies that modulation waveforms with steep current decay, such as rectangular and sawtooth waveforms, induce stronger transient cooling and coldgas entrainment into the Si-vapor region, thereby promoting supersaturation, enhancing nucleation, and suppressing particle growth. As a result, the simulated primary particle diameter becomes much smaller than that under triangular modulation. Representative experiments for rectangular and triangular modulation qualitatively validate this trend. In addition, half-cell testing confirms that Si NPs synthesized at high throughput show practically promising electrochemical performance, with an initial capacity of ~3500 mAh/g and a stable reversible capacity of ~1200 mAh/g after the initial cycles. These results indicate that millisecond-scale waveform engineering provides a physically grounded approach to controlling nanoparticle formation and linking plasma-scale transient behavior to nanoparticle functionality.