Chemical Origins of a Fast-Charge Performance in Disordered Carbon Anodes

Abstract

Fast charging of lithium-ion cells often causes capacity loss and limited cycle life, hindering their use in high-power applications. Our study employs electrochemical analysis and a multiphysics model to identify and quantify chemical and physical constraints during fast charging, comparing state-of-the-art graphite and nanocluster carbon (nC, a disordered carbon) anodes. The combination of modeling material phase separation phenomena with ion-electron transfer theory reveals significant insight. The active material strongly influences charge transfer kinetics and solid-state lithium diffusion. Unlike graphite, nC supports lithium insertion without phase separation, enabling faster lithium diffusion, better volume utilization, and lower charge transfer resistance. We demonstrate practical implications of these material phenomena through multilayer pouch cells made with nC anodes, which withstand over 5000 fast-charge cycles at 2C without significant degradation (<10% at reference 0.2C).