ScholarWorks@숙명여자대학교

초록

The introduction of ZrO2 in a Ni-rich cathode offers a balance between its surface protection and unavoidable capacity loss due to the chemical inertness and extremely low electrical conductivity of the cathode. Here, highly conductive black ZrO2-x spheres are successfully adopted as a bifunctional framework stabilizer and gas evolution reliever for the surface of a Ni-rich cathode by tuning the band-gap energy of ZrO2. Employing a facile reduction step, white monoclinic ZrO2 is converted into black oxygen-deficient tetragonal ZrO2-x, which significantly reduces the band-gap energy, improving the electrical conductivity. The interstitial occupancy of the black ZrO2-x spheres in the Ni-rich cathode improves the electron transport and surface structural stability via the resulting high electrical conductivity and excellent durability. The black ZrO2-x effectively suppresses the gas evolution from the Ni-rich cathode during charging at a high voltage of 4.5 V by inductively preserving the high oxidation state of Ni2+. These findings demonstrate that the oxygen-deficient ZrO2-x material exhibits multifunctionality to suppress gas evolution, as well as increase the capacity and protect the surface of the Nirich cathode. Thus, the bifunctionality of black ZrO2-x as an effective framework stabilizer and gas evolution reliever is demonstrated; it can be employed to produce Ni-rich cathodes exhibiting high capacity, long life, and high stability.

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