LAUSR

Significance Magneto-ionics promise ultralow-field sensor technologies. Meanwhile, the extent of real-time ion insertion/extraction of an electrode is the key state-of-charge (SOC) feature in batteries. We report lithiating magneto-ionic material to enable the precise SOC sensor monitoring in Li-ion battery using a molecular magnetic electrode. A microwave-excited spin wave reveals the lithiation level in the molecular-magnetic cathode, enabling precise magneto-ionic-based SOC monitoring under a lowest frequency and magnetic field of 0.35 GHz and 100 Oe, respectively, significantly lower than that of an inorganic magnetic electrode. More importantly, the magneto-ionic-based sensor shows a more than 2,000% increase in accuracy and a more than 5,000% reduction in response time. The findings provide the pathway toward the real-time accurate SOC estimation using molecular magnetic electrode.