The effect of synthesis and zirconium doping on the performance of nickel-rich NCM622 cathode materials for Li-ion batteries

Among the cathode materials for advanced Li-ion batteries, nickel-rich Ni-Co-Mn (NCM) LiNi_xCo_yMn_yO₂ (x > 0.5, x + 2y = 1) attracts great interest as promising materials owing to their high capacity, low cost, good cycling stability, safety and the fact that their stable capacity can be extracted by charging up to 4.3 V vs. Li. In this work, the effect of the synthesis route—freeze-drying, self-combustion, solid state and co-precipitation on the performance of NCM622 (LiNi_xCo_yMn_yO₂, x = 0.6, y = 0.2) cathodes—in Li cells was thoroughly studied. The material prepared by freeze-drying exhibited superior electrochemical properties. The effect of in situ and ex situ Zr⁴⁺ cations doping on the electrodes’ capacity, stability and average voltage was also studied. Doping via a top–down, ex situ mode improved the performance in terms of capacity stabilization, whereas electrodes comprising materials that were doped via a bottom–up in situ approach showed stable average voltage upon prolonged cycling. These effects are discussed and explained herein. Graphical abstract: [Figure not available: see fulltext.]