Revealing the interface-rectifying functions of a Li-cyanonaphthalene prelithiation system for SiO electrode

Chemical prelithiation is regarded as a crucial method for improving the initial Coulombic efficiency (ICE) of Li-storage anodes. Herein, a substituent-engineered Li-cyanonaphthalene chemical prelithiation system is designed to simultaneously enhance the ICE and construct a multifunctional interfacial film for SiO electrodes. X-ray photoelectron spectroscopy (XPS), electron energy-loss spectroscopy (EELS), nuclear magnetic resonance (NMR) spectroscopy and atomic force microscopy (AFM) prove that the Li-cyanonaphthalene prelithiation reagent facilitates the formation of a rectified solid electrolyte interface (SEI) film in two ways: (1) generation of a gradient SEI film with an organic outer layer (dense N-containing organics, ROCO2Li) and an inorganic LiF-enriched inner layer; (2) homogenization of the horizontal distribution of the composition, mechanical properties and surface potential. As a result, the prelithiated SiO electrode exhibits an ICE above 100%, enhanced CEs during cycling, better cycle stability and inhibition of lithium dendrite formation in the overcharged state. Notably, the prelithiated hard carbon/SiO (9:1)‖LiCoO2 cell displays an enhancement in the energy density of 62.3%.