Addressing the initial lithium loss of lithium ion batteries by introducing pre-lithiation reagent Li5FeO4/C in the cathode side

Abstract

The initial lithium loss caused by the formation of solid electrolyte interface (SEI) film in anode reduces the capacity of lithium-ion batteries. To solve this problem, adding a pre-lithiation reagent to the cathode is one of the most straightforward ways. Li5FeO4 (LFO) is a promising pre-lithiation reagent, but its relatively complex synthesis conditions and poor electronic conductivity limit its wide application. In this work, the Li5FeO4/C (LFO/C) composite is synthesized by low-temperature solid-phase route and used as pre-lithiation reagent in the LiFePO4 (LFP) cathode to assemble a full cell with graphite as anode. It has been found that the appropriate carbon content can clearly improve the electronic conductivity of the pre-lithiation reagent LFO, and the as-prepared LFO/C composite exhibits an ultra-high initial specific capacity of 719.95 mAh g−1. Besides, after adding the pre-lithiation reagent LFO/C to the LFP cathode, the initial charge capacity of the pre-lithiated LFP half cell is improved from 163.75 mAh g−1 to 186.68 mAh g−1. After 100 cycles, the cell keeps still good cycle stability. More importantly, after matching with the graphite anode, the discharge capacity of the full cell can increase from 132.2 mAh g−1 to 154.2 mAh g−1. After 50 cycles, no significant battery capacity decay is observed. Therefore, this study provides a new preparation method to improve the conductivity of the LFO and promote LFO industrialization.