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As the economy started to recover from the COVID pandemic, the price of Li2CO3 is skyrocketed to the highest. This situation has aggravated concerns on the supply chain for lithium-ion...

While lithium, manganese-rich (LMR) layered oxide cathode materials offer high energy density (>900 Wh kg–1) and low cost, LMR is susceptible to continuous capacity and voltage decay from the oxygen migration and side reaction with aqueous electrolyte at high voltage. Herein, the integration of Na/F co-doping (CD) and AlF3 coating on LMR is achieved without the need of complex atomic layer deposition. Akin to pristine and CD samples, CD with 1 wt % AlF3 (CD-1.0 wt %) shows excellent electrochemical performance with the capacity and voltage retentions of 93 and 91% after 150 cycles at 0.5C, respectively, and increased ionic conductivity. Spectroscopic analysis indicates that the coating mainly influences the Co distribution, where Co is enriched on the surface, and partial diffusion of Al3+ ions toward the bulk, leading to a slight change of transition-metal (TM) valence states at the nanometer scale and the formation of a stable Li x (CoAl)­O y phase. Post-cycling analysis reveals that CD-1.0 wt % can alleviate the formation of rock-salt structure and Mn dissolution. Besides, little to no metal segregation is detected for the cycled CD-1.0 wt % sample. This finding presents the first instance to apply co-doping and AlF3 coating as a new strategy to enhance the structural homogeneity and takes another step toward their commercial viability.

With the proliferation of market demand for lithium-ion batteries (LIBs) over the past decades, battery recycling has aroused extensive attention due to the environmental, supply, and economic issues caused by waste batteries. The hydrometallurgical recycling method has been widely adopted to recover cathode materials as a result of its wide applicability and high productivity. However, it is hard to completely eliminate impurities such as copper, aluminum, and carbon, which could bring significant impacts on recovered materials. Here, the influence of the carbon impurity on recovered LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode material is systematically investigated. It shows that the carbon impurity promotes nucleation during coprecipitation and forms holes in the cathode secondary particles after sintering which could enhance cyclability of the NCM622 cathode. The cathode with 0.2 atom % of carbon impurity displays the highest capacity of 159.9 mAh/g with a striking capacity retention rate of 97.9% after 100 cycles at 0.33C, but performs worse at high rates. Nonetheless, excess carbon (5 atom %) results in severe cation disorder and lattice distortion which significantly deteriorates the electrochemical properties of the NCM622 cathode. Therefore, it is important to strictly control carbon impurity during the recycling process for spent LIBs.

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Iron impurities are generally included in the obtained leaching liquor solution during the hydrometallurgical recycling method of spent lithium-ion batteries (LIBs) due to the usage of iron in battery casings and machinery parts of recycling equipment, which would definitely affect the physical and electrochemical features of the recovered active materials. In this work, the effects of iron impurity with different valence states (Fe2+ and Fe3+) and gradient concentrations (0.2, 1.0, and 5.0 at. %) for the obtained LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes are fully studied. It is found that Fe3+ impurity could easily lower the tap density and average size of NCM622 particles and even introduce some impurity phases in the NCM622 structure at high concentration (5.0 at. %), leading to much lower specific capacity, worse rate capability, and cycling performance of the Fe3+-based NCM622 cathode. On contrast, with certain concentrations of Fe2+ impurity (0.2 and 1.0 at. %), the NCM622 cathode material exhibits comparable and much better electrochemical properties compared with the virgin NCM622 materials. Based on these results, the valence of Fe impurity should be considered and controlled as well as its concentration during the recycling process design for spent LIBs.