Lattice Engineering to Refine Particles and Strengthen Bonds of the LiNi0.9Co0.05Mn0.05O2 Cathode toward Efficient Lithium Ion Storage

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.