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The layered transition metal oxides are an essential class of cathode materials in sodium-ion batteries. However, the capacity decay mechanisms of many materials at a wide voltage window are still ambiguous. Therefore, research on the intrinsic structure of materials at the electronic or atomic level is of great significance to unlock the potential of more materials. In this study, a new family of layered NaNi 0.45 Mn 0.3 Ti 0.2 M 0.05 O 2 (M = Nb/Mo/Cr) has been demonstrated to combine high specific capacity (NaNi 0.45 Mn 0.3 Ti 0.2 Cr 0.05 O 2 , 12 mA g−1, 185.7 mAh g−1, 2-4.2 V) with preferable Na+ insertion/extraction activity (1920 mA g−1, 111.2 mAh g−1). The participation of Ni2+/Ni3+ and Cr3+/Cr4+/Cr6+ in the redox reaction upon cycling significantly contributes to the superior specific capacity, and the diffusion kinetics calculation indicates that the substitution of Cr for Ni can create a more suitable path with a low energy barrier for Na+ movement, which is particularly crucial for the rate performance. Besides, the unfavorable cycling stability is affected by the distortion of the crystal structure, suggesting that the Jahn-Teller effect of Mn3+/Ni3+ and the second-order Jahn-Teller effect of Nb5+/Mo6+ (d0 transition metal) together with Cr6+ migration caused by disproportionation of Cr4+ have inescapable responsibilities. Additionally, the reversible phase transition between the O3 and P3 phases upon Na+ insertion/extraction at a wide voltage window is identified by in situ XRD measurements and verified to be the key factor of the high coulombic efficiency for NMTCr. An in-depth understanding of NMTNb and NMTMo can provide new insights for material design and exploitation. The composition-structure-property relationships behind the electrochemical performance can be comprehended profoundly by coupling the experimental verification with density functional theory calculations. • A new family of layered NaNi 0.45 Mn 0.3 Ti 0.2 M 0.05 O 2 (M = Nb/Mo/Cr) has been prepared. • The participation of Ni2+/Ni3+ and Cr3+/Cr4+/Cr6+ contributes greatly to the capacity. • The substitution of Cr provided a suitable path with low energy barrier for Na+ movement. • The Jahn-Teller effect of Mn3+/Ni3+ and second-order JT effect of Nb5+/Mo6+ are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three non-resonant SiOC-based meta-structures are synthesized by 3D printing. • The metamaterials achieve good impedance matching through structural design. • The reflection loss is −55.68 dB with an ultra-wideband absorption of 11.88 GHz. • The mechanisms between meta-structures and electromagnetic wave are investigated. Lightweight, wide-band ceramic-based electromagnetic (EM) absorbers have great application demand in the field of high-temperature EM wave absorption. However, it is difficult for traditional ceramic-based structural EM absorbing materials (EMAMs) to balance the contradiction between broadband absorption and good impedance matching due to resonance effect. Herein, three novel non-resonant SiOC-based triply periodic minimal surface (TPMS) meta-structures named Schoen G (SG), Schwarz D (SD) and Schwarz P (SP) with a density of 0.556 g/cm3 were successfully synthesized by digital light processing (DLP) 3D printing and polymer-derived ceramics (PDCs) method. Through the structural design of multilayer arrays and holes, three metamaterials achieve good impedance matching and broadband EM absorption. The effective absorption bandwidth (EAB) of all three meta-structures reaches 9.80 GHz (8.2–18.0 GHz) in a wide matching thickness range, covering the entire X-Ku band. In addition, the minimum reflection loss (RL min) of −55.68 dB is obtained at a matching thickness of 3.02 mm for SD meta-structure in X-band. Besides, the SG meta-structure tested by the arch method has an ultra-wide EAB of 11.88 GHz (6.12–18.0 GHz), exhibiting ultra-broadband EM absorption properties. It is significant that the intrinsic relationships between TPMS meta-structures and EM responses are explored by CST simulation. This work provides a new perspective for the design of lightweight, broadband ceramic-based EM metamaterial absorbers under high-temperature, harsh environments. [ABSTRACT FROM AUTHOR]