Boosting Li+ transport kinetics and structural stability of Co-free LiNi0.9Mn0.1-xAlxO2 cathode materials

Abstract

This study successfully synthesized Li[Ni_0.9Mn_0.06Al_0.04]O₂ (NMA964) cathode material using an organic amine co-precipitation method combined with high-temperature solid-state synthesis. Mechanistic insight into Al³⁺ doping via theory-experiment synergy revealed that Al³⁺ doping plays a dual role in enhancing structural stability and electrochemical performance. First-principles calculations demonstrated that AlO covalent bonds effectively suppress cation mixing and mitigate anisotropic stress during H2-H3 phase transitions, while experimental analyses confirmed that these bonds stabilize the host lattice against crack propagation. Additionally, Al³⁺ doping optimizes Li⁺ transport kinetics by reducing electrostatic repulsion between adjacent Li layers. As a result, the NMA964 cathode delivers an ultrahigh initial discharge capacity of 228.3 mAh g⁻¹ at 0.1C (2.5–4.3 V) and retains 165.9 mAh g⁻¹ after 100 cycles at 0.5C (72.6 % capacity retention), outperforming the undoped Li[Ni_0.9Mn_0.1]O₂ counterpart. This work provides atomic-level guidance for designing high-energy cathodes through targeted doping.