Polyanion incorporation strategy enables stable operation of Ni-rich NCM90 up to 4.5 V with tailored structural and electrochemical performance

Abstract

In this study, we developed an attractive synthesis approach for the incorporation of PO<inf>4</inf>3− polyanions during the co-precipitation of Li(Ni<inf>0.90</inf>Co<inf>0.05</inf>Mn<inf>0.05</inf>)O<inf>2</inf> (NCM90). This strategy effectively mitigates the inherent cycle stability issues at high cut-off voltages while enhancing both specific capacity and rate capability. By incorporating PO<inf>4</inf>3− polyanions into the NCM90 structure (denoted as P<inf>x</inf>-NCM90, where x = 0.0, 0.5, 0.7, and 0.9, representing the added mole % of PO<inf>4</inf>3−), the electrochemical performance was significantly improved. The optimized P<inf>0.7</inf>-NCM90 delivered a high discharge capacity of ∼230 mAh g−1 at 0.1 C within 3.0–4.5 V (vs. Li/Li+) with an initial Coulombic efficiency of ∼93.2 %. It also exhibited high rate capability (∼185 mAh g−1 at 4.0 C) and improved cycling stability, retaining ∼84 % of its capacity after 100 cycles at 1.0 C. Comprehensive physicochemical and electrochemical characterizations, including in-situ X-ray diffraction (XRD), revealed that the highly distributed PO<inf>4</inf>3− incorporation stabilizes the NCM90 structure. These findings highlight that PO<inf>4</inf>3− addition during co-precipitation is an effective strategy for improving the stability and electrochemical performance of high-Ni layered oxide cathodes at a high cut-off potential of 4.5 V (vs. Li/Li+). © 2025 Elsevier B.V., All rights reserved.