Synergistic bulk lattice and interface modulation by hierarchical tungsten engineering toward stable ultrahigh Ni- and Co-free cathodes

Ultrahigh Ni- and Co-free cathodes have emerged as promising candidates for next generation lithium-ion batteries by virtue of their high energy density and cost-effectiveness. However, the intrinsic structural instability and interfacial issues of these cathodes severely restrict their practical application. Traditional single-modification strategies hardly realize synchronous optimization of the bulk lattice structure and the electrode interface. In this work, a hierarchical tungsten (W) engineering strategy was employed to synergistically modify the LiNi_0.95Mn_0.05O₂ (NM95) cathode. The results indicate that W doping can create robust W–O–Ni hybridization orbitals, thereby efficiently reducing the electronic activity of Ni and O atoms. It restrains drastic Ni valence oscillation and irreversible lattice oxygen release. Meanwhile, in situ Li₂WO₄ coating constructs fast Li⁺ diffusion pathways, alleviating polarization and the Li⁺ migration barrier. Moreover, the hierarchical W modification significantly alleviates detrimental H2–H3 phase transition and suppresses microcrack propagation, reinforcing the structure's reversibility. Interface side reactions and CEI layer growth are also significantly reduced. Thus, NM95 cathodes exhibit outstanding electrochemical stability: after 200 cycles at 1C, the capacity retention rates at 2.7–4.3 V and 2.7–4.5 V were 93.7% and 80.8%, respectively. After 200 cycles at 0.5C, the capacity retention rate still remains at 84.8%. This provides a reliable technical route for the large-scale application of high-performance ultrahigh Ni- and Co-free cathodes.