Coupling Conductive Networks and Binder Chemistry to Balance Rate Capability and Mechanical Durability in Flexible NMC811 Cathodes

Abstract

The rapid growth of flexible and wearable electronics has created an increasing demand for lithium-ion batteries that can maintain high electrochemical performance while withstanding repeated mechanical deformation. In this research, we investigate the incorporation of single-walled carbon nanotubes (SWCNTs) as a conductive carbon dopant together with a polymer binder (VT475) in LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathodes. SWCNTs play a dual role in cathode performance. Mechanically, their one-dimensional nanostructure mitigates particle pulverization and improves tolerance to mechanical deformation (e.g., bending), which is essential for flexible and wearable applications. Electrochemically, SWCNTs form a percolated conductive network within the cathode, significantly improving electronic conductivity and facilitating efficient electron transport. This synergistic effect enhances capacity retention and cycling stability, even at high C-rates (132 mAh/g@5C). Pouch cells incorporating the SWCNT-doped cathodes were extensively characterized using galvanostatic testing at various C-rates, long-term cycling (1000 cycles), electrochemical impedance spectroscopy, and adhesion testing (ASTM D3359), among other methods. Relative to reference electrodes, the SWCNT-doped cathodes demonstrate synergistic improvement in electrochemical and mechanical performance. Based on the experimental results, a physics-informed semiempirical formulation model is developed to describe how the binder content influences the electrochemical and mechanical performance of the cathodes. The model supports slurry formulation selection by mapping the trade-off between rate capability, cycling stability, and adhesion according to application requirements.