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

Lithium-ion batteries incorporating Si-based anodes and nickel-rich LiNi_1-x-yCo_xMn_yO₂ (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 Li_2.19AlO_2.60 phase, which acts both as an HF scavenger and Li-ion conductor. The bifunctionality results in enhanced capacity retention and improved energy density in LiNi_0.5Co_0.2Mn_0.3O₂//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.