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

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 Ni-O 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 Ni-Li 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 Ni-O 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 similar to 12% higher than the pristine sample. Our approaches illustrate the importance of Ni-O network and provide a novel thought to further improve these promising cathodes. (c) 2018 Elsevier Ltd. All rights reserved.