Engineering Mesoporous Single Crystals Co-Doped Fe₂O₃ for High-Performance Lithium Ion Batteries

To achieve high-efficiency lithium ion batteries (LIBs), an effective active electrode material is vital. For the first time, mesoporous single crystals cobalt-doped Fe₂O₃ (MSCs Co–Fe₂O₃) is synthesized using formamide as a pore forming agent, through a solvothermal process followed by calcination. Compared with mesoporous single crystals Fe₂O₃ (MSCs Fe₂O₃) and cobalt-doped Fe₂O₃ (Co–Fe₂O₃), MSCs Co–Fe₂O₃ exhibits a significantly improved electrochemical performance with high reversible capacity, excellent rate capability, and cycling life as anode materials for LIBs. The superior performance of MSCs Co–Fe₂O₃ can be ascribed to the combined structure characteristics, including Co-doping and mesoporous single-crystals structure, which endow Fe₂O₃ with rapid Li⁺ diffusion rate and tolerance for volume change

Significantly Improving Lithium-Ion Transport via Conjugated Anion Intercalation in Inorganic Layered Hosts

Layered hydroxides (LHs) have emerged as an important class of functional materials owing to their unusual physicochemical properties induced by various intercalated species. While both the electrochemistry and interlayer engineering of the materials have been reported, the role of interlayer engineering in improving the Li-ion storage of these materials remains unclear. Here, we rationally introduce pillar ions with conjugated anion dicarboxylate groups, cobalt oxalate ions ([CoOx₂]^2–), into the interlayers of Co­(OH)₂ nanosheets [denoted as I-Co­(OH)₂ NSs]. The pillar ion guarantees excellent structural stability, high electrical conductivity, and accelerated Li-ion diffusion. The structure delivers high-rate cycling performance for lithium-ion batteries. This work provides insights for the design of LH-based high-performance electrode materials by a rational interlayer-engineering strategy

Metallic Transition Metal Selenide Holey Nanosheets for Efficient Oxygen Evolution Electrocatalysis

Catalysts for oxygen evolution reaction (OER) are pivotal to the scalable storage of sustainable energy by means of converting water to oxygen and hydrogen fuel. Designing efficient electrocatalysis combining the features of excellent electrical conductivity, abundant active surface, and structural stability remains a critical challenge. Here, we report the rational design and controlled synthesis of metallic transition metal selenide NiCo₂Se₄-based holey nanosheets as a highly efficient and robust OER electrocatalyst. Benefiting from synergistic effects of metallic nature, heteroatom doping, and holey nanoarchitecture, NiCo₂Se₄ holey nanosheets exhibit greatly enhanced kinetics and improved cycling stability for OER. When further employed as an alkaline electrolyzer, the NiCo₂Se₄ holey nanosheet electrocatalyst enables a high-performing overall water splitting with a low applied external potential of 1.68 V at 10 mA cm^–2. This work not only represents a promising strategy to design the efficient and robust OER catalysts but also provides fundamental insights into the structure−property−performance relationship of transition metal selenide-based electrocatalytic materials

Two-Dimensional Holey Co₃O₄ Nanosheets for High-Rate Alkali-Ion Batteries: From Rational Synthesis to in Situ Probing

A general template-directed strategy is developed for the controlled synthesis of two-dimensional (2D) assembly of Co₃O₄ nanoparticles (ACN) with unique holey architecture and tunable hole sizes that enable greatly improved alkali-ion storage properties (demonstrated for both Li and Na ion storage). The as-synthesized holey ACN with 10 nm holes exhibit excellent reversible capacities of 1324 mAh/g at 0.4 A/g and 566 mAh/g at 0.1 A/g for Li and Na ion storage, respectively. The improved alkali-ion storage properties are attributed to the unique interconnected holey framework that enables efficient charge/mass transport as well as accommodates volume expansion. In situ TEM characterization is employed to depict the structural evolution and further understand the structural stability of 2D holey ACN during the sodiation process. The results show that 2D holey ACN maintained the holey morphology at different sodiation stages because Co₃O₄ are converted to extremely small interconnected Co nanoparticles and these Co nanoparticles could be well dispersed in a Na₂O matrix. These extremely small Co nanoparticles are interconnected to provide good electron pathway. In addition, 2D holey Co₃O₄ exhibits small volume expansion (∼6%) compared to the conventional Co₃O₄ particles. The 2D holey nanoarchitecture represents a promising structural platform to address the restacking and accommodate the volume expansion of 2D nanosheets for superior alkali-ion storage