Performance and mechanism research of hierarchically structured Li-rich cathode materials for advanced lithium–ion batteries

The hierarchically structured cathode material Li_1.165Mn_0.501Ni_0.167Co_0.167O₂ (LMNCO) is successfully synthesized via a facile ultrasonic-assisted co-precipitation method with a two-step heat treatment by adopting graphene and carbon nanotubes (CNTs) as functional framework and modified material. The structure and electrochemical performance degeneration mechanism were systematically investigated in this work. The obtained LMNCO microspheres possess a hierarchical nano-micropore structure assembled with nanosized building blocks, which originates from the oxidative decomposition of the transition metal carbonate precursor and carbonaceous materials accompanied with the release of CO₂ (but still remain carbon residue). What’s more, the positive electrode exhibits enhanced specific capacities (276.6 mAh g⁻¹ at 0.1 C), superior initial coulombic efficiency (80.3 %), remarkable rate capability (60.5 mAh g⁻¹ at 10 C) and high Li⁺ diffusion coefficient (~10⁻⁹ cm² s⁻¹). The excellent performances can be attributed to the pore structure, small particle sizes, large specific surface area and enhanced electrical conductivity. (1 C = 250 mA g⁻¹).