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Na-ion batteries (NIBs) capture intensive research interest in large-scale energy storage applications because of sodium’s abundant resources and low cost. However, the low capacity, poor conductivity, and short cycle life of the commonly used anodes are the main challenges in developing advanced NIBs. Here, stimulated by the recent successful synthesis of biphenylene [Science 2021, 372, 852], we show that these problems can be curbed by assembling armchair biphenylene nanoribbons of different widths into three-dimensional architectures, which lead to homogeneously distributed nanopores with robust structural and mechanical stability. Through density functional theory and molecular dynamics calculations combined with the tight-binding model, we find that the assembled 3D biphenylene structures are metallic and thermally stable up to 2500 K, where the metallicity is further identified to originate from the pz-orbitals (π-bonds) of the sp2 carbon atoms. Especially, the optimal assembled structures HexC28 (HexC46) deliver a gravimetric capacity of 956 (1165) mA h g–1 and a volumetric capacity of 1109 (874) mA h mL–1, which are much higher than those of graphite and hard carbon anodes. Moreover, they also show a suitable average potential, negligible volume change, and low diffusion energy barrier. These findings demonstrate that assembling biphenylene nanoribbons is a promising strategy for designing next-generation NIB anodes.

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Superatom-based superionic conductors are of current interest due to their promising applications in solid-state electrolytes for rechargeable batteries. However, much less attention has been paid to their thermal properties, which are vital for safety and performance. Motivated by the recent synthesis of superatom-based superionic conductor Na3OBH4 consisting of superhalogen cluster BH4, we systematically investigate its lattice dynamics and thermal conductivity using the density functional theory combined with a self-consistent phonon approach. We reveal the bonding hierarchy features by studying the electron localization function and potential energy surface and further unveil the rattling effect of the BH4 superatom, which introduces strong quartic anharmonicity and induces soft phonon modes in low temperatures by assisting Na displacements, thus calling for the necessity of quartic renormalization and four-phonon scattering in calculating the lattice thermal conductivity. We find that the contribution of four-phonon processes to the lattice thermal conductivity increases from 13 to 32% when the temperature rises from 200 to 400 K. At room temperature (300 K), the phonon scattering phase space is enlarged by 133% due to the four-phonon interactions, and the lattice thermal conductivity is evaluated to be 5.34 W/mK, reduced by 24% as compared with a value of 6.99 W/mK involving three-phonon scattering only. These findings provide a better understanding of the lattice stability and thermal transport properties of superionic conductor Na3OBH4, shedding light on the role of strong quartic anharmonicity played in superatom-based materials.