“Fe-locking” effect by g-C3N4 stabilizing lithium iron oxide pre-lithiation additives

Li5FeO4 (LFO) is an ideal cathode pre-lithiation reagent to improve on lithium-ion batteries due to its high irreversible capacity, cheapness and suitable de-lithiation platform. However, the transition metal (iron) dissolution during cycling hinders its further application. Here, the correlation between the degree of dissolution of iron upon cycling and battery performance is deeply disclosed. More importantly, an effective strategy of ultrathin C3N4 protective layers on the LFO surface is also proposed in this regard. In conjunction with theoretical analyses, it is found that the protective layer formed on LFO is not only conducive to the lithium ions diffusion but also effectively suppressing the dissolution of iron. Consequently, the full-cell capacity is increased by 37.7 mAh g−1 when C3N4@Li5FeO4 (C3N4@LFO) is introduced into LiNi0.8Co0.1Mn0.1O2 cathode material. This work offers a rational viewpoint and a widely applicable strategy for boosting battery performance.