Surface Gradient Engineering Relaxes Stress Concentration in Ultrahigh-Ni Cathodes, Enabling Superior Cyclability in Pouch Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 41086362.
- Also identified by DOI 10.1021/acs.nanolett.5c04350.
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Abstract
Developing ultrahigh-Ni cathodes is critical for advancing next-generation high-energy Li-ion batteries (LIBs), yet reducing the Co content exacerbates mechanochemical degradation and lowers Li-ion transport. Herein, we design a surface low-Co-gradient-distributed and bulk Mg-doped Li(Ni<sub>0.97</sub>Mn<sub>0.03</sub>)<sub>0.995</sub>Ge<sub>0.005</sub>O<sub>2</sub> (GM-<i>g</i>-NMC) cathode, in which nonmagnetic Ge substitution for Co not only stabilizes the crystal structure synergistically with Mg but also promotes a near-surface Co gradient distribution by suppressing its diffusion. These features mitigate lattice contraction while enhancing surface mechanical robustness, thereby relaxing the stress concentration and preserving structural and interfacial stability. <i>Operando</i> characterizations and electrochemical analyses reveal a 5-fold reduction in potential polarization, along with the suppression of rock-salt phase formation. Consequently, GM-<i>g</i>-NMC delivers an ultrahigh reversible capacity of 229.0 mAh g<sup>-1</sup> at 0.1C and 151.7 mAh g<sup>-1</sup> at 10C. In pouch-type full cells, it retains 80.1% of its initial capacity after 1200 cycles at 1C, prolonging the service period relative to the previously reported ultrahigh-Ni cathodes.