Zhouliang Tan

Abstract Intergranular cracking of Ni‐rich layered LiNi 1‐x‐y Co x Mn y O 2 (1‐x‐y ≥ 0.8) cathode particles deteriorate the chemo–electro–mechanical stability of high‐energy lithium‐ion batteries (LIBs), thus presenting a challenge to typical modification methods to establish robust structures with highly efficient lithium‐ion storage. Herein, the ZrTiO 4 (ZTO) as an epitaxial layer to enhance mechanical stability of ultrahigh‐Ni LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM90) is reported for the first time. Intensive exploration from structure characterizations (X‐ray absorption spectroscopy and in situ X‐ray diffraction techniques), multi‐physics field analysis, and first‐principles calculations disclose that the conformal ZTO layers and Zr doping effectively suppresses the internal strain and the release of lattice oxygen, which prodigiously restrains the local stress accumulation during whole (de)lithiation processes, thereby maintaining good mechanical stability of the materials. Meanwhile, the protective ZTO layer also prevents electrolyte erosion, thus keeping an intact surface structure of NCM90. Notably, ZTO‐modified NCM90 achieves significantly improved cyclability under high‐voltage (4.5 V) operation, expressing a 17% increase in capacity retention (71% vs 88%) after 100 cycles. Overall, this work reveals the role of internal strain in the original degradation behavior and effectiveness of surface engineering strategy to solve the challenge, emphasizing that the conformal surface protection mitigates the internal stress of Ni‐rich NCM by anchoring the lattice oxygen.

TA is employed as a reducing agent to supply electrons in the hydrothermal reaction, followed by brief annealing to restore the Li + diffusion pathways along the [010] direction and facilitate the re-intercalation of Li + in spent LFP.

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.