Preserving the structural stability of LiNi0.92Co0.04Mn0.04O2 cathode by Ti4+-ion doping for lithium-ion batteries

Abstract

Given the exponential rising demand for high-performance lithium-ion batteries (LIBs), Ni-rich layered LiNixCoyMn(1-x-y)O2 (LN) cathode materials have gained significant attention. Nevertheless, poor structural stability of LN cathode materials is a critical hurdle to their use in LIBs. In this regard, Ti-doped LN cathode materials are designed to enrich the structural reliability of LN cathode materials, and their underlying behaviors are elucidated. Once Ti is replaced in the layered sites of the LN cathode materials, it strongly binds to lattice oxygen owing to its outstanding binding affinity. Therefore, Ti-doped Ni-rich LN cathode materials exhibit increased thermal stability and mechanical rigidity compared with bare LN cathode materials. In terms of cycling behavior, the Ti-doped Ni-rich LN cathode materials deliver remarkably improved cycling retention; the 2.0% Ti-doped Ni-rich LN cathode material yields an 88.0% retention, while the bare Ni-rich LN cathode material yield a 52.2% retention after 100 cycles. Further analyses of the recovered Ni-rich LN cathodes indicate that structural deformations, such as microcracks and phase transitions, are evidently suppressed in the Ti-doped LN cathode, and additional parasitic reactions, such as electrolyte decomposition, are also inhibited after cycling. This means that incorporating Ti in Ni-rich LN cathode materials not only suppresses structural deformation but also simultaneously increases the interfacial stability upon cycling, thus leading to a comprehensively improved cycling behavior.