Improved stability of Ni-rich cathode by the substitutive cations with stronger bonds

Abstract

In this work, we select four types of substitute cations, Ti4+, Al3+, Mg2+ and Zn2+, to compare their influence on LiNi0.8Co0.1Mn0.1O2. After modification, the average lengths of NiO bonds are elongated with the turn of the Ti, Al, Mg, pristine and Zn-substituted, namely the bond energies are diminished with this sequence, according to their roughly inverse square relation. This tendency is also obeyed by oxygen defects, which induces the NiLi exchanging and surface decomposition, and then exert the effect on electrochemical behavior of Ni-rich cathodes. Among the investigated samples, the Ti-modified sample, which possesses the highest NiO bond energy, presents the best cyclic stability and rate capability, retaining 93.8% in the 200th cycle and 155.1 mAh g−1 under 5C, which is ∼12% higher than the pristine sample. Our approaches illustrate the importance of NiO network and provide a novel thought to further improve these promising cathodes.