Conductive Agent-Controlled Tortuosity in Solvent-Free Thick-Film Electrodes for High-Energy Lithium-Ion Batteries

Abstract

Rapid developments in lithium-ion battery (LIB) technology have been fueled by the expanding market for electric vehicles and increased demands for energy storage. Recently, thick electrode fabrication by solvent-free methods has emerged as a promising strategy for enhancing the energy density of LIBs. However, as electrode thickness increases, the tortuosity of lithium-ion transport also increases, resulting in severe polarization and poor electrochemical performance. Here, we investigate the effect of conductive agent morphology on the structural and electrochemical properties of 250 μm thick lithium iron phosphate (LFP)/conductive agent/polytetrafluoroethylene (PTFE)-based electrodes. Three commercially available conductive additives, namely 0D Super P, 1D multi-walled carbon nanotubes (MWCNTs), and 2D graphene nanoplatelets (GNPs), were incorporated into LFP-based electrodes. The MWCNT-incorporated electrode with a high loading mass (42 mg cm⁻²) exhibited a high porosity (ε = 51%) and low tortuosity (τ = 4.02) owing to its highly interconnected fibrous network of MWCNTs. Due to the fast lithium-ion transport kinetics in the MWCNT-incorporated electrode, the electrochemical performances exhibited a high specific capacity of 157 mAh g⁻¹ at 0.1 C and an areal capacity of 7.16 mAh cm₋₂ at 0.1 C with a high-rate capability and excellent cycling stability over 300 cycles at 0.1 C. This study provides a guidance for utilizing conductive agents to apply in the low tortuous thick electrode fabricated by a solvent-free process. Additionally, this work paves the way to achieve scalable and sustainable dry processing techniques for developing next-generation energy storage technologies.