Revisiting the High-Entropy Paradigm for Ni-Rich Cathodes: Dopant-Induced Surface Engineering as the Key to Stability

초록

High-entropy doping is a promising strategy for stabilizing high-Ni layered cathodes, yet the origin of performance enhancement-whether from configurational entropy or specific dopant chemistry-remains ambiguous. Here, we systematically deconvolute these competing effects in Co-free, Ni-rich cathodes. By comparing materials with identical entropy but different dopants (W-Nb-Mg vs Zr-Ti-Mg), we demonstrate that dopant chemistry is the dominant factor governing electrochemical performance. The W/Nb/Mg-doped cathode exhibited vastly superior cycling stability, which is attributed to the formation of a thin, passivating rock-salt surface phase that fosters a robust, LiF-rich cathode-electrolyte interphase. In contrast, increasing configurational entropy by adding more elements (W-Nb-Mg-Zr-Ti-Al) primarily enhanced bulk mechanical properties and suppressed detrimental phase transitions, but yielded only marginal gains in cycling stability over the lower-entropy W/Nb/Mg-doped counterpart. Our findings underscore that individual dopant chemistry remains paramount, even within high-entropy strategies. We therefore challenge the prevailing paradigm of maximizing entropy, proposing instead that a chemically informed doping strategy focused on engineering stable surface phases is a more rational and effective pathway toward next-generation lithium-ion battery cathodes with exceptional durability.

키워드