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As the power density of electronic devices continuously increases, there is a growing demand to improve the heat conduction performance of thermal management materials for addressing heat dissipation issues. Single-/few-layer graphene is a promising candidate as a filler of a metal matrix due to its extremely high thermal conductivity ( k ); however, the well-arranged assembly of 2D-component graphene with a high volume fraction remains challenging. Herein, we integrated a novel graphene-based macroscopic material of graphene film (GF) into a Cu matrix by infiltrating molten Zr-microalloyed Cu into a spirally folded and upright-standing GFs skeleton. The microstructure of the GF/Cu composites was regulated by an interface modification strategy. The GF/Cu composites with a spirally layered microstructure exhibit a superior k of 820 W/m K in the axial direction, much higher than that of Cu-matrix composites reinforced with graphene nanosheets (generally <500 W/m K) and twice that of Cu. The thermal transfer mechanisms were investigated by experiments and theoretical calculations. The results reveal that the excellent performance is attributed to the construction of high-heat conduction channels and a positive coordinating effect at the Zr-modified GF/Cu interface. Meanwhile, the relation between interfacial microstructure and heat transfer is established in the composites using interfacial thermal resistance as a bridge. This work yields in-depth insight into the heat conduction mechanism in highly oriented structures and provides a promising solution for the thermal management issues of high-power electronics.

MXenes have been used as substrate materials for single-atom catalysts (SACs) due to their unique two-dimensional (2D) structure, high surface area, and high electronic conductivity. Oxygen is the primary terminating group of MXenes; however, all of the reported Pt SACs till now are fabricated with F-terminated MXenes. According to the first-principles calculations of this work, the failure of using O-terminated MXenes as substrates is due to the low charge density around Pt and C, which weakens the catalytic activity of Pt. By adjusting the electronic structure of M 2 C using a second submetal with a lower work function than M, 18 potential bifunctional Pt SACs are constructed based on O-terminated bimetal MXenes. After further consideration of some important practical application factors such as overpotential, solvation effect, and reaction barriers, only four of them, i.e., Cr 2 Nb 2 C 3 O 2 -V O -Pt, Cr 2 Ta 2 C 3 O 2 -V O -Pt, Cr 2 NbC 2 O 2 -V O -Pt, and Cr 2 TaC 2 O 2 -V O -Pt, are screened as bifunctional oxygen reduction reaction/oxygen evolution reaction (ORR/OER) catalysts. All of these screened SACs are originated from Cr-based MXenes, implying the significance of Cr-based MXenes in designing bifunctional Pt SACs.

A novel metallic carbon allotrope, Q-carbon, was discovered using first-principles calculations. The named Q-carbon possessed a three-dimensional (3D) cage structure formed by carbon atoms with three ligands. The energy distribution of electrons in different orbitals revealed that Q-carbon has a low degree of s-p orbital hybridization. The calculated Li + binding energies suggested Li + aggregation inside Q-carbon during lithiation. As a result, a Li 8 C 32 phase was formed and gradually expanded in Q-carbon, implying a typical two-phase transition. This allowed Q-carbon to have a constant theoretical voltage of 0.40 V, which effectively inhibited Li dendrite formation. A stable Li 8 C 32 /C 32 two-phase interface was confirmed by stress-strain analysis, and a calculated Li + diffusion barrier of ∼0.50 eV ensured effective Li + diffusion along a 3D pathway. This study was of great significance for the understanding of two-phase transition of Li + storage materials and provided a new insight into the design of new carbon materials for energy storage applications.

Transition metal polysulfides with high S content, such as VS 4 , TiS 4 , and MoS 3 , have high specific Li + capacities, but their reaction mechanisms for lithium-ion batteries remain unclear due to unknown intermediate products. In this work, first-principles calculations based on the density functional theory were performed to reveal the electrochemical properties of VS 4 for lithium-ion batteries. The results demonstrated multiple phase transformations during Li + insertion, starting with nucleation transformation from VS 4 to Li 3 VS 4 and followed by gradual decomposition reactions. Enthalpy-driven long-range migration of Li 2 S molecules resulted in crystalline to amorphous transformation during decomposition. S and V successively behaved as redox centers for Li x VS 4 before and after x = 3. Moreover, low activation energy and high Li + diffusivity were observed at room temperature, revealing superior rate capability of the material.