Enabling high-energy-density and long-life lithium-ion batteries through bifunctional cathode prelithiation.

Lithium-ion batteries incorporating Si-based anodes and nickel-rich LiNi1-x-yCoxMnyO2 (NCM) cathodes offer exceptional energy density compared to conventional systems. However, they still suffer from two critical challenges: irreversible lithium loss at the anode and interfacial degradation at the cathode. To simultaneously resolve both issues, we propose a bifunctional prelithiation strategy using a novel Li5AlO4 (LAO) material, which has remained unexplored due to sluggish delithiation kinetics and poorly understood lithium extraction mechanisms. Through comprehensive in-situ X-ray diffraction, differential electrochemical mass spectrometry and X-ray photoelectron spectroscopy, we demonstrate that LAO effectively compensates for lithium loss (delivering 601.1 mAh g-1 at 4.3 V) at the anode and stabilizes the cathode interface via the in-situ formed Li2.19AlO2.60 phase, which acts both as an HF scavenger and Li-ion conductor. The bifunctionality results in enhanced capacity retention and improved energy density in LiNi0.5Co0.2Mn0.3O2//Si-graphite full cells. By integrating lithium compensation and cathode stabilization into a single LAO agent, our work introduces a new paradigm for integrated electrode engineering beyond conventional prelithiation methods.