Novel conductive and binding fibers for ultra-thick lithium-ion battery electrodes

Using ultra-thick electrodes could be a promising strategy to increase the energy density of lithium-ion batteries. However, thickening electrodes leads to higher resistance for electron/ion transportation within the electrodes, resulting in a decrease in capacity and power. In addition, binder migration, which is a problem in the slurry coating process, becomes more pronounced. In this paper, we propose a novel fibrous conductive additive, conductive and binding fibers (CBFs), which are simply fabricated by combining two cost-effective materials—acetylene black and polyvinylidene fluoride—using electrospinning. We also report techniques to prepare CBF-based electrodes (CBFEs) using a solvent-free dry process. Morphological and electrochemical evaluations of the CBFEs (mass loading: 100 mg cm⁻²) reveal that the unique electrode structure formed by CBFs leads to high battery performance. The continuous efficient conductive networks formed by CBFs prevent electrical isolation of the active material particles. In addition, the CBFs serve as frameworks in electrodes because of their adhesion, forming larger pores (∼1 μm) and enhancing ion transport. Consequently, CBFEs achieve a discharge capacity of 91.9 mA h g_AM⁻¹ at 0.2C—a 1.6-fold improvement over conventional electrodes. The features of CBFs, which combine both conductivity and binding properties, enable the realization of a low-cost and high-performance electrode.