Revitalizing battery performance: Li2CuO2 additive for compensating irreversible lithium loss in LiFePO4-Based full cells

Abstract

The solid electrolyte interphase (SEI) formation significantly consumes the limited Li⁺ and fades capacity in commercial lithium-ion batteries (LIBs). An effective strategy is to introduce auxiliary lithium at cathode to Li⁺ consumption. In this work, the Li₂CuO₂ was synthesized via simplified sintering process and exhibited excellent moisture stability, functions as a promising lithium compensation agent. The high delithiation capacity of approximately 490mAh g⁻¹ with two distinct voltage plateaus at ∼3.3V and ∼4.1V vs. Li/Li⁺ makes it compatible with commercial LFP cathode to enhance energy density, prolong cycle life, and even facilitate the direct recycling of spent cathode materials. Adding 5 wt% Li₂CuO₂ can improve the performance of LFP||Graphite and LFP||Si@C, especially the LFP||Graphite increased initial discharge capacity by 13mAh g⁻¹ (to 155mAh g⁻¹@0.1C) and enhanced cycling stability. Furthermore, a functional prelithiation separator (PP@Li₂CuO₂) was developed for spent LFP (S-LFP) regeneration. The S-LFP||PP@Li₂CuO₂||Gr cell achieved 153mAh g⁻¹ initial capacity (vs. 102mAh g⁻¹ for S-LFP||Gr cell, graphite anode) and retained 115mAh g⁻¹ after 60 cycles, reactivating degraded LFP.