Surface Coupling between Mechanical and Electric Fields Empowering Ni-Rich Cathodes with Superior Cyclabilities for...

Ni-rich cathodes with high energy densities are considered as promising candidates for advanced lithium-ion batteries, whereas their commercial application is in dilemma due to dramatic capacity decay and poor structure stability stemmed from interfacial instability, structural degradation, and stress-strain accumulation, as well as intergranular cracks. Herein, a piezoelectric LiTaO₃ (LTO) layer is facilely deposited onto Li[Ni_x Co_y Mn_{1- x - y} ]O₂ (x = 0.6, 0.8) cathodes to induce surface polarized electric fields via the intrinsic stress-strain of Ni-rich active materials, thus modulating interfacial Li⁺ kinetics upon cycling. Various characterizations indicate that the electrochemical performances of LTO-modified cathodes are obviously enhanced even under large current density and elevated temperature. Intensive explorations from in situ X-ray diffraction technique, finite element analysis, and first-principle calculation manifest that the improvement mechanism of LTO decoration can be attributed to the enhanced structural stability of bulk material, suppressed stress accumulation, and regulated ion transportation. These findings provide deep insight into surface coupling strategy between mechanical and electric fields to regulate the interfacial Li⁺ kinetics behavior and enhance structure stability for Ni-rich cathodes, which will also arouse great interest from scientists and engineers in multifunctional surface engineering for electrochemical systems.