Nickel-rich layered oxides with their large reversible capacity are considered to be some of the most promising cathode materials for high-energy Li-ion batteries. However, the fast decay of capacity and potential of Ni-rich layered oxides occurs unavoidably during long-term cycling, which is harmful to the stable output of energy density of Li-ion batteries. In this work, Na-ion doping is introduced into LiNi 0.8 Co 0.15 Al 0.05 O 2 in order to stabilize both the capacity and potential. In this work, 1 wt % Na ions are doped into LiNi 0.8 Co 0.15 Al 0.05 O 2 with a gradient distribution from the surface to the bulk. In addition, the morphology of the spherical oxide particle is not damaged by Na-ion doping. Comparing with the pristine sample, Na-doped LiNi 0.8 Co 0.15 Al 0.05 O 2 presents lower potential polarization, higher initial Coulombic efficiency, and better rate capability. In particular, the cycle stability of both potential and capacity is greatly enhanced for the Na-doped sample, which is very important for stabilizing the energy density of cathode. In addition, the integrated spherical morphology of the Na-doped sample particle is retained even after long-term cycling, which is attributed to the pillaring effect of Na ions with large radiuses.

A nanoscale cobalt gradient substitution is introduced to suppress the P2–O2 phase transition and improve the Na+ kinetics of high-voltage P2-Na2/3[Ni1/3Mn2/3]O2 cathodes for sodium-ion batteries.

A Ni/Mn-graded surface is proposed to suppress the unwanted phase transformations and side-reactions of high-energy lithium-rich layered oxide cathodes, and thus to mitigate their capacity and voltage decay.

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High-Ni layered oxides are potential cathodes for high energy Li-ion batteries due to their large specific capacity advantage. However, the fast capacity fade by undesirable structural degradation in liquid electrolyte during long-term cycling is a stumbling block for the commercial application of high-Ni oxides. In this work, a functional gel polymer electrolyte, grafted with sodium alginate, is introduced to increase the stability of high-Ni oxide cathodes at the levels of both the particle and electrode. An in situ generated ion-conducting layer appears on the interface through the chemical interaction between transition-metal cations of the cathode and the metalophilic reticulum group in sodium alginate. Such a tailoring layer can not only enhance the interfacial compatibility on the cathode/electrolyte interface, reducing the interfacial resistance, but also inhibit the HF corrosion, suppressing the dissolution of transition-metal cations and harmful gradient distribution of components through the oxide cathode at the electrode level. Meanwhile, detrimental microcracks in oxide microspheres and between primary crystallites are impressively inhibited at the particle level. The high-Ni oxide cathode with the metalophilic gel polymer electrolyte shows excellent cycle stability with large initial capacity of 204.9 mA h g −1 at a 1.0C rate and high discharge capacity retention within 300 cycles at high temperature.