A Template-Free Fabrication Strategy for Low-Tortuosity Porous LiCoO ₂ Thick Electrodes Enabling High-Rate Performance

Conventional lithium-ion batteries employing thin electrodes are approaching their energy density limits. Thick electrode technology represents a promising solution by increasing mass loading while maintaining efficiency and cost-effectiveness. However, they suffer from a severe ionic transport bottleneck due to elongated and tortuous ion diffusion pathways, which hinder their practical application. In this work, we present a template-free strategy for fabricating low-tortuosity thick LiCoO2 (LCO) electrodes (denoted as A-LCO and S-LCO) with 40 mg cm–2 active material mass loading, and using NH4HCO3 and NaHCO3 as foaming agents, respectively. The resulting porous structure electrodes exhibit substantial improvements over conventional plate electrodes (C-LCO), with A-LCO showing superior performance due to the facile decomposition of NH4HCO3. A-LCO delivers a specific capacity of 74.5 mAh g–1 at 2C, in stark contrast to the nearly negligible capacity of 0.2 mAh g–1 for C-LCO. The enhanced performance of A-LCO is attributed to optimized ion transport (with tortuosity reduced from 20.35 to 10.92), improved electrolyte wettability (contact angle decreased from 28.624° to 8.706°), and more uniform Li+ distribution (concentration gradient reduced by 69%). By regulating the ion transport paths through rational structural design to address the fundamental ionic transport bottleneck, this approach offers a promising pathway toward high-energy-density batteries without compromising rate capability or cycling stability.