Model-informed design of microcrack-tolerant cathodes for fast-charging lithium-ion batteries

초록

Boosting the fast-charging capability of lithium-ion batteries (LIBs) is essential for the widespread adoption of electric vehicles. However, nickel-rich layered oxides—the leading cathode materials for high-energy LIBs—suffer from microcracking during fast-charge cycling, resulting in severe capacity fading. Here, we propose an advanced design strategy for mechanically robust bimodal Ni-rich layered oxide cathodes guided by three-dimensional (3D) electrochemo-mechanical modeling. The 3D models, constructed with realistic particle morphologies and electrode microstructures, resolve the evolution of reaction heterogeneity and mechanical stress in the cathodes upon fast charging. Combined with experimental validation, we reveal that the dominant degradation pathway is microcracking of large cathode particles (diameter ∼12 µm) near the separator driven by coupled electrode- and particle-level reaction heterogeneity—namely, sluggish electrolyte-phase ionic transport in densely packed electrodes and diffusion limitation within large particles. To address these issues, we develop a bilayer cathode architecture featuring a ∼10 µm-thick top layer of small single-crystalline particles (∼3 µm). Due to their uniform small size and mechanical robustness, the single-crystalline particles enable fast, homogeneous reactions in the current-concentrated region near the separator and simultaneously act as a mechanical buffer that suppresses localized stress in the underlying large particles. As a result, the bilayer cathode effectively suppresses microcrack formation and subsequent parasitic reactions, delivering a high capacity retention of 76.2% after 300 cycles at 3C, compared with 62.4% for a conventional cathode. This work establishes a practical electrode design principle for enabling durable, high-energy, fast-charging LIBs.

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