In-situ Ti4+-doped modification of layer-structured Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode materials for high-energy lithium-ion batteries

Abstract

The further commercialization of layer-structured Ni-rich LiNi_0.83Co_0.11Mn_0.06O₂ (NCM83) cathode for high-energy lithium-ion batteries (LIBs) has been challenged by severe capacity decay and thermal instability owing to the microcracks and harmful phase transitions. Herein, Ti⁴⁺-doped NCM83 cathode materials are rationally designed via a simple and low-cost in-situ modification method to improve the crystal structure and electrode-electrolyte interface stability by inhibiting irreversible polarizations and harmful phase transitions of the NCM83 cathode materials due to Ti⁴⁺-doped forms stronger metal-O bonds and a stable bulk structural. In addition, the optimal doping amount of the composite cathode material is also determined through the results of physical characterization and electrochemical performance testing. The optimized Ti⁴⁺-doped NCM83 cathode material presents wider Li⁺ ions diffusion channels (c = 14.1687 Å), lower Li⁺/Ni²⁺ mixing degree (2.68 %), and compact bulk structure. The cell assembled with the optimized Ti⁴⁺-doped NCM83 cathode material exhibits remarkable capacity retention ratio of 95.4 % after 100cycles at 2.0C and room temperature, and outstanding reversible discharge specific capacity of 148.2 mAh g^-1 at 5.0C. Even under elevated temperature of 60 °C, it delivers excellent capacity retention ratio of 92.2 % after 100cycles at 2.0C, which is significantly superior to the 47.9 % of the unmodified cathode material. Thus, the in-situ Ti⁴⁺-doped strategy presents superior advantages in enhancing the structural stability of Ni-rich cathode materials for LIBs.

Keywords: In-situ modification; Layer-structured Ni-rich cathode; Lithium-ion batteries; Structural stability; Ti(4+)-doped.