Yu Liu

Driven by lithium resource constraints and cost volatility, there is a critical need for high-performance, universal anodes for non-lithium systems such as Na and K, while maintaining rapid ion transport and structural stability. Addressing the limited intrinsic interaction between graphene and alkali-metal ions─and the resulting capacity limitations─this study proposes and systematically evaluates, based on density functional theory (DFT), a design strategy for dual Fe-atom-doped graphene, D²-Fe₂C₁₂. Introducing dual Fe atoms breaks local symmetry, reconstructs the electronic states near the Fermi level, and creates a high density of strong anchoring sites, thereby synergistically enhancing adsorption thermodynamics and surface diffusion kinetics. Calculations show that the theoretical specific capacity for Na reaches 2513.25 mAh/g, and those for Li and K are 1675.50 and 837.75 mAh/g, respectively, markedly outperforming conventional carbon-based anodes. Structural analysis further indicates that the lattice variation induced by ion adsorption is less than 5%, corroborating structural stability under multi-ion storage. Meanwhile, favorable electronic conductivity and low migration barriers (Li/Na/K all 2-Fe₂C₁₂ achieves a balanced optimization of high capacity, low strain, and superior kinetics, demonstrating strong potential as a universal anode for Li/Na/K systems and providing a reusable theoretical foundation for the atomistic, rational design of dual-Fe-doped two-dimensional carbon materials.

Metal–organic frameworks (MOFs) represent a novel electrochromic material system but are limited in tunable color versatility, rapid switching speed, and long‐term cycling stability. A new multicolor electrochromic behavior is reported, with transitions from green to blue to purple, in conducting nickel‐catecholate (Ni‐CAT‐1) MOFs. The system significantly improves cycling stability to 2000 cycles and reduces switching time to 3.6 s, both of which outperform most state‐of‐the‐art MOF systems. An in‐depth understanding of the coloring mechanism, particularly the interconversion among C─O, C─O ^• , and C = O groups is revealed. Water molecules play diverse roles in this redox process. Specifically, water molecules induce distortions in Ni─O bonds, facilitating C = O bond formation and expediting the oxidized coloring process, while also aiding the dissociation of ions from solvation complexes to enhance the reduction process. The practical applications of these findings are demonstrated by designing flexible multicolor electrochromic devices (FMEDs) for use in camouflage, flexible displays, and augmented reality (AR).

A rapid in situ method was employed to synthesize the β-Ni(OH) ₂ @NF integrated electrode for a high performance ASC device.

The pursuit of high capacity is one of the key challenges for the development of alkaline ion batteries (AIBs, namely Li/Na/K-ion batteries; LIBs, NIBs, or KIBs). Carbon-based anode materials represented by graphite have been widely used in secondary batteries; however, their storage capacity is generally not high. Graphene was once considered a promising candidate, but it has proven to be incapable of interacting strongly with alkali ions. Here, by first-principles calculations, we predict an allotrope of graphene that may soon be experimentally synthesized, called T-graphene, which is a promising anode material for AIBs. We find that when it is used as the anode for NIBs, its theoretical capacity can be as high as 2232 mA h g⁻¹ (Na₆C₆), which is six times that of graphite. For LIB and KIB anodes, the specific capacities are 744 mA h g⁻¹ and 1116 mA h g⁻¹, corresponding to the Li₂C₆ and K₃C₆ chemical formula, respectively. We first demonstrate that the material is mechanically stable. We further show that the material has good electrical conductivity whether it is before or after adsorption of Li(Na or K). We also studied the diffusion of Li(Na or K) on its surface and found that their corresponding diffusion barriers are very low (Li, Na and K are about 0.37 eV, 0.35 eV and 0.25 eV, respectively), which means good rate performance. It is calculated that the average open circuit voltage of the corresponding three half-cells at full charge is also low (LIBs is about 0.20 V, NIBs is about 0.12 V, and KIBs are about 0.37 V), which is beneficial for increasing the operating voltage of the full battery. In addition, during the adsorption of lithium, sodium and potassium, the lattice change of the material is very small (about 1.0% for lithium, about 1.4% for sodium, and about 1.9% for potassium), which means good cycling performance. These results indicate that T-graphene is expected to replace graphene and become a very attractive anode material for AIBs.