High-Energy-Density and Long-Lifetime Lithium-Ion Battery Enabled by a Stabilized Li 2 O 2 Cathode Prelithiation Additive.

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, Li 2 O 2 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 Li 2 O 2 additive. Li 2 O 2 is well confined in poly(methyl methacrylate) (PMMA) nanofibers (P-Li 2 O 2 ) via electrospinning, which exhibits greatly enhanced ambient stability compared with the unprotected one. Notably, when P-Li 2 O 2 is preloaded in LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathodes (NCM-P-Li 2 O 2 ), PMMA nanofibers remain stable during cathode slurry processing but readily dissolve in electrolytes and expose Li 2 O 2 for effective electrochemical oxidation. Fabrication of P-Li 2 O 2 allows systematic investigation of prelithiation behavior in full cells (NCM-P-Li 2 O 2 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.