Boosting electrochemical performance of Co-free Ni-rich cathodes by combination of Al and high-valence elements

Ni-rich layered oxides, such as LiNixCoyMn1_ x_yO2/LiNixCoyAl1_x_ yO2, are promising cathode materials for lithium-ion batteries due to their high capacity. However, the commercial applicability of these materials is hindered by their inferior cyclic stability and limited cobalt supply. Herein, a cost-effective Al-substituted, Cofree, Ni-rich cathode (LiNi0.96Al0.04O2, NA96) is proposed and optimized by doping with high-valence molybdenum or tungsten. It is demonstrated that the introduction of Mo or W refines of primary particles and creates more compact microstructures. Moreover, Mo/W doping effectively mitigates deleterious H2 -> H3 phase transitions, formation of cracks, and surface lattice oxygen loss, as confirmed through ex/in situ characterizations and density functional theory calculations. As a result, both Mo-NA96 and W-NA96 exhibit superior structural integrity, long-term cyclability, rate capability, and thermal stability compared to the undoped counterparts. Notably, W-NA96 displays exceptional rate capability, achieving a discharge capacity of 185.9 mAh g_ 1 at a high current rate of 10C, even without Co. Furthermore, the 2 Ah pouch-type full cells using W-NA96 paired with graphite exhibit excellent capacity retention (89% after 300 cycles at 1C). These findings highlight the potential of combining Al and high-valence elements in Co-free, Ni-rich cathodes, offering a new perspective for designing high-performance cathodes.