Formation gassing and high-temperature cycling of 5 Ah batteries with lithium-rich ferrite lithium as pre-lithiation reagent

Lithium-rich ferrite lithium (Li₅FeO₄, LFO) is a promising cathode pre-lithiation reagent for high-energy-density lithium-ion batteries, but its practical application is hindered by poor air stability and excessive gassing. In this work, we adopt a solid-phase synthesis method to prepare LFO and apply it as a cathode pre-lithiation reagent in 5 Ah lithium iron phosphate (LiFePO₄, LFP)/graphite (Gr) full cells. We show that LFO readily hydrolyzes to form LiOH, which further reacts with CO₂ even under low-humidity conditions. Adding 2 wt% LFO to a 5 Ah LiFePO₄/graphite pouch cell increases formation gassing from 18.1 ± 0.8 to 65.6 ± 1.6 cm³ and shifts the gas composition from predominantly reducing gases (93.6%) to a near-equal mixture (49.5%). Despite this, the LFO-containing cell retains 83.9% capacity after 1500 cycles at 45 °C, whereas the control cell reaches 82.9% after only 900 cycles. These findings highlight the trade-offs associated with LFO pre-lithiation and provide practical guidance for integrating lithium supplements into long-life, high-energy batteries.