Many recycling processes have been developed for spent Li-ion batteries (LIBs), such as pyrometallurgy, hydrometallurgy, and direct recycling. For all the recycling methods, however, impurities are always introduced from the current collectors or casing materials, especially aluminum (Al), which might lead to negative effects on recovered electrode materials. Therefore, it is significant to determine the impacts of Al impurity on recovered materials. Here, the influence of the Al impurity for the synthesized LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) precursor and cathode is systematically studied. The cell with 0.2 at % Al impurity displays the highest reversible capacities (145.2, 130.5, and 100.3 mAh g −1 from 2, 3, and 5 C, respectively) and striking cycling capability at 2 C after 100 cycles with the highest retention capacity of 138.5 mAh g −1 . Meanwhile, the excess Al ions (5 at %) lead to the Li/Mn superlattice structure and deteriorate electrochemical performance of the synthesized NCM622 cathode.

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The lithium-manganese-rich layered oxide cathode (LMR-NMC), xLi2MnO3·(1 – x)­LiMO2 (M = Co, Ni, and Mn), is on demand because of its high specific capacity of over 250 mA h g–1 between the voltage range 2.0–4.8 V (vs Li/Li+). Because of the requirement of activating the Li2MnO3 phase in the first cycle, oxygen extraction from the lattice structure occurs. Consequently, capacity fading and voltage fading during cycling are still major obstacles to the commercialization of LMR-NMC in battery applications. Here, codoping Na and F into LMR-NMC via facile hydroxide coprecipitation followed by solid-state reaction is introduced. Na and F are partially substituted into Li and O sites, respectively. These dopant ions enlarge the Li slab, which in turn eases Li diffusion and minimizes oxygen loss, thereby stabilizing the structure. The codoped sample exhibits both high capacity retention (97%) and high voltage retention (91%) over 100 cycles with an initial discharge capacity of 260 mA h g–1 at 0.1 C. Compared to other reports on LMR-NMC as obtained by coprecipitation, results from this study show the best capacity retention. The developed codoping approach may provide a new strategy for designing high-performance LMR-NMC cathodes for next-generation lithium ion batteries.

P2‐type sodium‐manganese‐based layered cathodes, owing to their high capacity from both cationic and anionic redox, are a potential candidate for Na‐ion batteries (NIBs) to replace Li‐ion technology in certain applications. Still, the structure instability originating from irreversible oxygen redox at high voltage remains a challenge. Here, a high sustainability cobalt‐free P2‐Na0.72Mn0.75Li0.24X0.01O2 (X = Ti/Si) cathode is developed. The outstanding capacity retention and voltage retention after 150 cycles are obtained in half‐cells. The finding shows that Ti localizes on the surface while Si diffuses to the bulk of the particles. Thus, Ti can act as a protective layer that alleviates side reactions in carbonate‐based electrolyte. Meanwhile, Si can regulate the local electronic structure and suppress oxygen redox activities. Notably, full‐cells with hard carbon (≈300–335 W h kg−1 based on the cathode mass) deliver the capacity retention of 83% for P2‐Na0.72Mn0.75Li0.24Si0.01O2 and 66% for P2‐Na0.72Mn0.75Li0.24Ti0.01O2 after 500 cycles; this electrochemical stability is the best compared to other reported cathodes based on oxygen redox at present. The superior cycle performance also stems from the ability to inhibit microcracking and planar gliding within the particles. Altogether, this finding offers a new composition for developing high‐performance low‐cost cathodes for NIBs and highlights the unique role of Ti/Si ions.