Engineering transition metal compounds (TMCs) catalysts with excellent adsorption-catalytic ability has been one of the most effective strategies to accelerate the redox kinetics of sulfur cathodes. Herein, this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping, bimetallic/bi-anionic TMCs, and TMCs-based heterostructure composites. It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band, d/p-band center, electron filling, and valence state. Moreover, the electronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity, electron filling, and ion radius, resulting in electron redistribution, bonds reconstruction, induced vacancies due to the electronic interaction and changed crystal structure such as lattice spacing and lattice distortion. Different from the aforementioned two strategies, heterostructures are constructed by two types of TMCs with different Fermi energy levels, which causes built-in electric field and electrons transfer through the interface, and induces electron redistribution and arranged local atoms to regulate the electronic structure. Additionally, the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out. It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

Polymer-based composites with high thermal conductivity and dielectric breakdown strength have gained increasing attention due to their significant application potential in both power electronic devices and power equipment. In this study, we successfully prepared novel sandwich AlN/epoxy composites with various layer thicknesses, showing simultaneously and remarkably enhanced dielectric breakdown strength and thermal conductivity. The most optimized sandwich composite, with an outer layer thickness of 120 μm and an inner layer thickness of 60 μm (abbreviated as 120-60) exhibits a high through-plane thermal conductivity of 0.754 W/(m·K) (4.1 times of epoxy) and has a dielectric breakdown strength of 69.7 kV/mm, 8.1% higher compared to that of epoxy. The sandwich composites also have higher in-plane thermal conductivity (1.88 W/(m·K) for 120-60) based on the novel parallel models. The sandwich composites with desirable thermal and electrical properties are very promising for application in power electronic devices and power equipment.

Metal–organic frameworks (MOFs) with diverse structures have been projected as futuristic electrode materials for lithium-ion batteries (LIBs). In this work, two ternary Li–Co-MOFs of three-dimensional (3D) porous structures were synthesized, inspired by LiCoO₂ inorganic metal salts, through a simple solvothermal method and further applied as active cathode materials for the first time in lithium-ion batteries. In these MOF structures, the lithium atoms are located at the same (SNNU-73) or different (SNNU-76) sites as cobalt atoms, and the four-coordinated tetrahedron mode is used to coordinate with the oxygen atoms. The 3D porous frameworks provide a good channel for the embedding and de-embedding of lithium ions. The experimental results suggest that porous Li–Co-MOF ternary composites show excellent cycling stability. Particularly, the discharge capacity and average coulombic efficiency of SNNU-73 reach 155.6 mA h g⁻¹ and nearly 100% for 50 cycles at a rate of 50 mA g⁻¹. This synergistic effect of mixed Li and Co sites demonstrates great potential of MOFs as advanced electrode materials, and provides a promising route to designing porous materials for lithium-ion batteries in the future.

Developing highly active catalysts with bidirectionally catalytic activity is regarded as an effective strategy for enhancing redox reaction kinetics in lithium–sulfur (Li–S) batteries to boost cathode performance. High-entropy alloys (HEAs) possess unique characteristics, inheriting the functionalities of each of their components while co-adjusting electronic structures, thus showing great potential in catalyzing the complex redox reactions in the Li–S batteries. In this work, composites of HEA nanoparticle (FeCoNiZnCu)–nitrogen-doped carbon nanotubes (NCNTs) are synthesized with uniformly dispersed HEAs inside the NCNT matrix. The introduction of Cu, which has electronic donation capabilities, enhances the catalytic properties of FeCoNiZnCu by shifting the d band center of Fe, Co, and Ni upwards, while the relatively low d band center of Cu broadens the d band distribution in comparison to FeCoNiZn. Benefitting from these improved catalytic properties, batteries using the FeCoNiZnCu–NCNT-modified separator achieved a better rate performance at 2C with a capacity of 679.7 mA h g⁻¹ and cyclic stability at 1C with a decay rate of 0.072% for 600 cycles. This work provides insights into HEA design for optimizing catalytic effects in the Li–S batteries by selecting appropriate elements and adjusting their d band distributions.

Olivine-structure LiFePO₄ is considered as promising cathode materials for lithium-ion batteries. However, the material always sustains poor electron conductivity, severely hindering its further commercial application. In this work, zinc oxide and carbon co-modified LiFePO₄ nanomaterials (LFP/C-ZnO) were prepared by an inorganic-based hydrothermal route, which vastly boosts its performance. The sample of LFP/C-xZnO (x = 3 wt%) exhibited well-dispersed spherical particles and remarkable cycling stability (initial discharge capacities of 138.7 mAh/g at 0.1 C, maintained 94.8% of the initial capacity after 50 cycles at 0.1 C). In addition, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) disclose the reduced charge transfer resistance from 296 to 102 Ω. These suggest that zinc oxide and carbon modification could effectively minimize charge transfer resistance, improve contact area, and buffer the diffusion barrier, including electron conductivity and the electrochemical property. Our study provides a simple and efficient strategy to design and optimize promising olivine-structural cathodes for lithium-ion batteries.