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The structural instability of high-nickel materials severely limits their commercial applications. In this article, a one-step high-temperature solid-phase sintering method is applied to form a Ta2O5 protective layer on the surface of LiNi0.8Co0.15Al0.05O2 (NCA) with Ta5+ entering the lattice, which achieves the double-effect of coating and doping. The Ta2O5 protective coating can inhibit the side reaction between the electrode material and electrolyte, and Ta5+ doping can relieve the Li+/Ni2+ disorder ratio. These significantly enhance the structural stability of NCA. The obtained NCA-Ta2O5 displays an excellent capacity retention rate (94.46%, at 1C after 200 cycles), which is much better than that (60.97%) of the pristine NCA. The exploration of structural evolution reveals that NCA-Ta2O5 can maintain a good spherical structure without obvious cracks after 200 cycles at 1C, while the original NCA has a serious structural collapse. Besides, NCA-Ta2O5 presents outstanding discharge capacity (151.02 mAh g–1 vs NCA: 131.70 mAh g–1) at a high rate of 10C. This work provides ideas for improving the performance of high-nickel materials, which is of great significance to the optimization of the cathode material for lithium-ion batteries.

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In this paper, we propose a graphene-dielectric metasurface to enhance the light-matter interactions in graphene. The dielectric metasurface consists of periodically arranged silicon split rings placed on the silica substrate, which supports a symmetry-protected bound state in the continuum (BIC). When perturbation is introduced into the system to break symmetry, the BIC will transform into the quasi-BIC with high quality (Q)-factor. As the graphene layer is integrated with the dielectric metasurface, the absorption of graphene can be enhanced by the quasi-BIC resonance and a bandwidth-tunable absorber can be achieved by optimizing the Fermi energy of graphene and the asymmetry parameter of the metasurface to satisfy the critical coupling condition. By varying the Fermi energy of graphene, the quasi-BIC resonances can be effectively modulated and the max transmission intensity difference is up to 81% and a smaller asymmetry parameter will lead to better modulation performance. Our results may provide theoretical support for the design of absorber and modulator based on the quasi-BIC.