Amorphous Protective Layers to Reshape Inorganic-Rich Interphases for High-Voltage Sodium-Ion Batteries

Although sodium-ion batteries (SIBs) are competitive for large-scale electrical energy storage, the high-voltage instability of the cathode–electrolyte interphase (CEI) formed on the cathode surface results in the dissolution of the transition metal (TM) and the sluggish interfacial electrochemical reaction kinetics, which deteriorates both the energy density and the cycle life of the SIBs. Herein, we propose a surface modification strategy to reconstruct the interphase of P2-type Na 0.7 Li 0.03 Mg 0.03 Ni 0.27 Mn 0.6 Ti 0.07 O 2 (LM′NMT) cathode with amorphous SiO 2 (denote as SiO 2 @LM′NMT) by a wet chemical method. This approach facilitates the reconfiguration of a more stable, inorganic-rich CEI due to enhanced adsorption catalysis of an amorphous coating with ample defects, resulting in improved Na + transport kinetics and inhibition of subsequent side reactions, TM dissolution, and structural degradation. As a result, the modified SiO 2 @LM′NMT-5 cathode exhibits an impressive capacity of 131.6 mAh g −1 at 0.1 C and maintains exceptional cycling stability, with 91.7% capacity retention after 150 cycles at 1 C within the voltage window of 2.2 to 4.4 V. This study grasps insights into optimizing the CEI to push forward practical application of SIBs under high voltages.