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Zr‐modified LiNi1/3Co1/3Mn1/3−xZrxO2 samples were prepared through a rheological‐phase method. The results indicate that there is only partial Zr doping into the bulk phase of the LiNi1/3Co1/3Mn1/3O2 particles, whereas the rest of the Zr remained on the surface to form a Li2ZrO3 coating layer during the Zr‐modification process. The Zr‐modified LiNi1/3Co1/3Mn1/3−xZrxO2 samples show lower discharge specific capacities at low rates, however, which exhibit clearly improved rate capabilities than that of pristine LiNi1/3Co1/3Mn1/3O2. Among the Zr‐modified LiNi1/3Co1/3Mn1/3−xZrxO2 samples, LiNi1/3Co1/3Mn1/3−0.01Zr0.01O2 (x=0.01) shows the best rate capability, which exhibts158, 142, and 132 mAh g−1 at 1.0, 2.0, and 3.0 C, respectively. The related results indicate that the doped Zr in pristine LiNi1/3Co1/3Mn1/3O2 could improve the structure stability and the formation of an inactive Li2ZrO3 coating layer which could suppress the interfacial side reaction of LiNi1/3Co1/3Mn1/3O2.

In this work, a LiNi1/3Co1/3Mn1/3O2/CNT/Graphene (NCM/CNT/GN) hybrid material with 3D conductive network and excellent rate capability has been successfully prepared by a facile wet chemical method.

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Systematic electrochemical impedance spectroscopic (EIS) combining with cyclic voltammograms (CV) and charge/discharge test have been used to investigate the reaction and capacity fade mechanism of LiNi0.5Co0.2Mn0.3O2 electrode with high cutoff voltage 3.0–4.5 V and high working temperature 55°C. It was found that the phase transformation and the Li-Ni site exchange in lattice at high voltage (>4.3 V) acted on charge transfer process were the main reasons of capacity fading with the cutoff voltage of 3.5–4.5 V. The degradation of LiNi0.5Co0.2Mn0.3O2 cathode with high-temperature was mainly associated with the strong catalytic activity of Ni4+ which can cause the side reaction between electrode and electrolyte to form unstable SEI film as well as the acceleration of phase transformation on the surface of electrode with high electrode polarization potential. Furthermore, it was found that improving the performance of SEI film should be one of the most important methods for improving the cycling performance of LiNi0.5Co0.2Mn0.3O2 cathode under high-temperature and we have proved it by systematic discussing the EIS results of the LiNi0.5Co0.2Mn0.3O2 cathode in electrolyte with fluoro-ether as an additive.

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