Microstructural degradation of Ni-rich cathode materials is a major bottleneck limiting their widespread applications, originating from their microcracks due to lattice strain. Herein, a facile lattice engineering strategy (praseodymium substitution at octahedral 3b Ni sites) is constructed to greatly reduce the lattice strain of the LiNi0.9Co0.05Mn0.05O2 cathode. The relationship between the lattice strain and electrochemical performance is systematically examined to gain insights into the Pr activity-governing mechanisms. Furthermore, the experimental and DFT calculations reveal that praseodymium substitution not only reduces the lattice strain during the de-/lithiation and enhances the electronic activity near the Fermi level but also reduces local stress buildup by refining the primary particles to grow along the radial direction. The ameliorated LiNi0.9Co0.05Mn0.05O2 shows low lattice strain and achieves a record capacity retention of 92.3% after 100 cycles, higher than that of the original sample (capacity retention of 78.7%). Moreover, it still exhibits an ultrahigh capacity of 168 mA h·g–1 even at 10 C due to a lower Li+ migration energy barrier. This work deeply investigates the information on the bulk structure, electronic properties, and interaction mechanism between substitution cations and Ni-rich layered oxides, which provides a new insight into the design and construction of advanced high-capacity cathode materials.

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P2-type Na 0.67 MnO 2 with a stable structure and an open framework can provide numerous channels for fast Na + de/intercalation, for which it is considered to be advantageous in application of the cathode material for Na-ion batteries. However, the complex phase transition occurring during cycling and the lattice distortion triggered by the Jahn−Teller effect severely restrict its development. Herein, the modified Na 0.67 MnO 2 with Cu or Fe single-element doping as well as Cu and Fe double-element doping was synthesized by the sol−gel method, and the effects of doping on the crystal structure and electrochemical performances of Na 0.67 MnO 2 were studied. It was demonstrated that the phase of the material did not change after the introduction of Cu and Fe elements, and the cycling stability and rate performance were greatly improved by Cu and Fe double-doping owing to their synergistic effect. The Na 0.67 Mn 0.92 Fe 0.04 Cu 0.04 O 2 (NMFCO) cathode delivers discharge specific capacities of 110.5 mA h g −1 at 5 C and 91.8 mA h g −1 at 10 C and exhibits the high-capacity retention of 94.35% at 1 C and 90.68% at 5 C after 100 cycles. Overall, this study offers a guiding direction for accelerating the modification of P2-type Na 0.67 MnO 2 as a cathode active material for high performance Na-ion batteries.

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LiNixCoyAlzO2(NCA) cathode materials are drawing widespread attention, but the huge gap between the ideal and present cyclic stability still hinders their further commercial application, especially for the Ni‐rich LiNixCoyAlzO2 (x > 0.8, x + y + z = 1) cathode material, which is owing to the structural degradation and particles' intrinsic fracture. To tackle the problems, Li0.5La2Al0.5O4 in situ coated and Mn compensating doped multilayer LiNi0.82Co0.14Al0.04O2 was prepared. XRD refinement indicates that La–Mn co‐modifying could realize appropriate Li/Ni disorder degree. Calculated results and in situ XRD patterns reveal that the LLAO coating layer could effectively restrain crack in secondary particles benefited from the suppressed internal strain. AFM further improves as NCA‐LM2 has superior mechanical property. The SEM, TEM, XPS tests indicate that the cycled cathode with LLAO–Mn modification displays a more complete morphology and less side reaction with electrolyte. DEMS was used to further investigate cathode–electrolyte interface which was reflected by gas evolution. NCA‐LM2 releases less CO2 than NCA‐P indexing on a more stable surface. The modified material presents outstanding capacity retention of 96.2% after 100 cycles in the voltage range of 3.0–4.4 V at 1C, 13% higher than that of the pristine and 80.8% at 1 C after 300 cycles. This excellent electrochemical performance could be attributed to the fact that the high chemically stable coating layer of Li0.5La2Al0.5O4 (LLAO) could enhance the interface and the Mn doping layer could suppress the influence of the lattice mismatch and distortion. We believe that it can be a useful strategy for the modification of Ni‐rich cathode material and other advanced functional material.