Three birds with one stone: A mechanically robust and highly ion-conductive LiAlO2 artificial layer enables Si anodes with high initial coulombic efficiency, fast kinetics, and ultralong cyclability

The practical applications of silicon (Si) anode is limited by its severe volume expansion, sluggish Li + transport, interfacial side reactions, and low initial Coulombic efficiency (ICE). Beyond the known capacity loss from SEI formation and “dead” Li x Si domains insulated by solid electrolyte interphase (SEI) layer, the kinetically trapped electro-active lithium in Li x Si—a frequently overlooked factor—also critically limits ICE and Li + transport. Herein, we construct a mechanically robust and Li + -conductive artificial LiAlO 2 interphase on Si surface via an evaporation-controlled hydrolysis, followed by an in situ chemical prelithiation, and a thermal annealing process. Calculations show that the LiAlO 2 /Si interface facilitates the interfacial Li + diffusion by lowering the Li + migration barrier from 0.90 to 0.31 eV. Benefiting from the improved interfacial stability and enhanced Li + transport kinetics, the Si@LiAlO 2 anode reduces the capacity loss from trapped active Li, trapped inactive Li, and SEI Li consumption to 2.3%, 0.3%, and 10.4%, respectively (vs 10.8%, 1.5%, and 16.8% for pristine Si). Consequently, Si@LiAlO 2 delivers a high capacity of 3020.2 mAh g −1 with a high ICE of 87.1% at 0.2 A g −1 , far exceeding 70.9% of Si anode. The Si@LiAlO 2 anode also exhibits excellent rate capability (809.1 mAh g −1 at 8 A g −1 ), and remarkable cycling durability (980 mAh g −1 after 1000 cycles at 4 A g −1 , 80.1% capacity retention). Furthermore, incorporating 10 wt% Si@LiAlO 2 can enhance the energy density of the LiFePO 4 ||graphite full cell by 25%, underscoring its promising potential for practical high-energy-density LIBs.