Differences between graphite and disordered carbon anodes for high-power Li-ion batteries

The increasing demand for Li-ion batteries necessitates the development of batteries capable of fast-charging in low time. However, limitations in mass transport and kinetic factors within battery electrodes, especially at the anode, bottlenecks fast-charge performance and induces parasitic processes (e.g., lithium plating), which can significantly reduce battery capacity. Graphite, the most widely used anode material, exhibits suboptimal fast-charge performance due to phase separation during lithium intercalation, leading to capacity degradation [1]. Disordered carbon anodes have emerged as a potential alternative to graphite, offering high capacity retention and resistance to lithium plating. However, a comprehensive understanding of the physical processes underlying their improved performance compared to graphitic electrodes is still lacking. In this study [2], we employ electrochemical analysis and a validated multi-physics model [1,3-4] to identify and quantify the chemical and physical origins of performance differences between state-of-the-art graphite and nanocluster carbon (a disordered carbon) anodes during fast-charging. Our model, validated against galvanostatic intermittent titration techniques (GITT) and charge/discharge curves, predicts the Li concentration distribution at the particle scale, revealing the effects of various intercalation mechanisms on fast-charge performance (Figure 1). By quantifying the contributions of activation, concentration, and diffusion overpotential losses to the electrochemical response, we elucidate how the active material influences charge transfer kinetics and solid-state lithium diffusion. Unlike graphite, nanocluster carbon enables lithium insertion without phase separation, facilitating faster lithium diffusion, improved volume utilization, and reduced charge transfer resistance. Consequently, nanocluster carbon demonstrates enhanced performance and higher capacity retention during fast-charge than graphite. To demonstrate the practical implications of these material phenomena, we fabricate multi-layer pouch cells with nanocluster carbon anodes, which withstand over 5,000 fast-charge cycles at 2C without significant degradation (Figure 2).