Compositional core-shell design by nickel leaching on the surface of Ni-rich cathode materials for advanced high-energy and safe rechargeable batteries

초록

Ni-rich layered oxides are promising cathode candidates for Li-ion batteries because of their high discharge capacity, high energy density, and low cost. However, poor cycling stability and thermal instability during cycling limit their commercial application in electric vehicles. To overcome these drawbacks, Ni-rich transition metal hydroxide precursors comprising a Ni-rich core and Ni-less surface region are successfully prepared in this study by a simple treatment process with dilute sulfuric acid. The final cathode materials have a compositional core-shell design, taking advantage of the stable cyclability and high thermal stability of the Ni-less surface layer as well as the high capacity of the Ni-rich core. The cycling stability of this Ni-rich cathode significantly improves after leaching, showing a capacity retention of 82.3% after 150 cycles at a rate of 0.5C and elevated temperature of 60 degrees C, much higher than that of a pristine Ni-rich cathode (65.4%). Furthermore, the thermal stability of the prepared Ni-rich cathode improves remarkably after leaching. These results suggest that the prepared cathode meets the energy storage demands of electric vehicles in terms of energy density, power, and cycling life; therefore, it is a promising cathode material for electric vehicle applications.

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