Porosity-gradient dry-processed graphite electrode with deformable primer layer for boosting fast-charging capability of lithium-ion batteries

초록

To improve the fast-charging capability of lithium-ion batteries, it is critical to engineer the electrode microstructure, particularly the electrolyte-filled pore network that governs Li+ transport. Herein, we present a facile and scalable approach for fabricating a porosity-gradient graphite electrode via a solvent-free dry process, where the upper region exhibits higher porosity than the bottom region, thereby facilitating fast ion transport. Unlike previous methods that require additional post-processing, the porosity gradient is spontaneously induced during the lamination step by tuning the mechanical deformability of a primer layer through polymer binder selection (poly(acrylic acid), carboxymethyl cellulose, or polyvinylidene fluoride). 3D XCT and FIB-SEM tomography reveal that dry electrodes incorporating a ductile polyvinylidene fluoride-based primer layer exhibit the steepest porosity gradient. Consequently, these electrodes demonstrate enhanced fast-charging performance (3C, 10.5 mA cm−2) compared to less-gradient dry electrode and conventional wet electrode while effectively suppressing lithium plating. Reconstructed 3D microstructure-driven pore network analysis and electrochemical simulations further confirm that the gradient pore structure enhances long-range pore connectivity and facilitates Li+ transport. This work highlights the pivotal role of dry electrode microstructure design in achieving fast-charging capability with manufacturing compatibility and scalability.

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