Lithium-ion batteries (LIBs) typically suffer from large irreversible capacities caused by active lithium loss during formation of a solid electrolyte interface (SEI) at the anode side. Cathode prelithiation with preloaded additives has emerged as an effective strategy to solve the above issue. With ultrahigh theoretical capacity, Li2O2 serves as an excellent cathode prelithiation additive, whereas poor ambient stability limits its further development. In this study, we report a surface protection strategy to enable ambient processing of the Li2O2 additive. Li2O2 is well confined in poly(methyl methacrylate) (PMMA) nanofibers (P-Li2O2) via electrospinning, which exhibits greatly enhanced ambient stability compared with the unprotected one. Notably, when P-Li2O2 is preloaded in LiNi0.5Co0.2Mn0.3O2 cathodes (NCM-P-Li2O2), PMMA nanofibers remain stable during cathode slurry processing but readily dissolve in electrolytes and expose Li2O2 for effective electrochemical oxidation. Fabrication of P-Li2O2 allows systematic investigation of prelithiation behavior in full cells (NCM-P-Li2O2 cathodes paired with Si/Graphite anodes) and its impact on the electrochemical performance. Rational tuning of the prelithiation degree provides guidance for optimizing the amount of the cathode additive, which brings appealing cell lifetime and energy density.
Keywords: active lithium loss; cathode prelithiation additive; prelithiation; prelithiation degree; stabilized Li2O2.