Rational composite materials made from transition metal sulfides and reduced graphene oxide (rGO) are highly desirable for designing high-performance lithium-ion batteries (LIBs). Here, rGO-coated or sandwiched CoS_x composites are fabricated through facile thermal sulfurization of metal–organic framework/GO precursors. By scrupulously changing the proportion of Co²⁺ and organic ligands and the solvent of the reaction system, we can tune the forms of GO as either a coating or a supporting layer. Upon testing as anode materials for LIBs, the as-prepared CoS_x-rGO-CoS_x and rGO@CoS_x composites demonstrate brilliant electrochemical performances such as high initial specific capacities of 1248 and 1320 mA h g⁻¹, respectively, at a current density of 100 mA g⁻¹, and stable cycling abilities of 670 and 613 mA h g⁻¹, respectively, after 100 charge/discharge cycles, as well as superior rate capabilities. The excellent electrical conductivity and porous structure of the CoS_x/rGO composites can promote Li⁺ transfer and mitigate internal stress during the charge/discharge process, thus significantly improving the electrochemical performance of electrode materials.

The preparation of novel one-dimensional core–shell Fe/Fe₂O₃ nanowires as anodes for high-performance lithium-ion batteries (LIBs) is reported. The nanowires are prepared in a facile synthetic process in aqueous solution under ambient conditions with subsequent annealing treatment that could tune the capacity for lithium storage. When this hybrid is used as an anode material for LIBs, the outer Fe₂O₃ shell can act as an electrochemically active material to store and release lithium ions, whereas the highly conductive and inactive Fe core functions as nothing more than an efficient electrical conducting pathway and a remarkable buffer to tolerate volume changes of the electrode materials during the insertion and extraction of lithium ions. The core–shell Fe/Fe₂O₃ nanowire maintains an excellent reversible capacity of over 767 mA h g⁻¹ at 500 mA g⁻¹ after 200 cycles with a high average Coulombic efficiency of 98.6 %. Even at 2000 mA g⁻¹, a stable capacity as high as 538 mA h g⁻¹ could be obtained. The unique composition and nanostructure of this electrode material contribute to this enhanced electrochemical performance. Due to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowires are promising anode materials for the next generation of high-performance LIBs.

Binary metal oxides have been deemed as a promising class of electrode materials for high-performance lithium ion batteries owing to their higher conductivity and electrochemical activity than corresponding monometal oxides. Here, NiFe₂O₄ nanoplates consisting of nanosized building blocks have been successfully fabricated by a facile, large-scale NaCl and KCl molten-salt route, and the changes in the morphology of NiFe₂O₄ as a function of the molten-salt amount have been systemically investigated. The results indicate that the molten-salt amount mainly influences the diameter and thickness of the NiFe₂O₄ nanoplates as well as the morphology of the nanosized building blocks. Cyclic voltammetry (CV) and galvanostatic charge–discharge measurements have been conducted to evaluate the lithium storage properties of the NiFe₂O₄ nanoplates prepared with a Ni(NO₃)₂/Fe(NO₃)₃/KCl/NaCl molar ratio of 1:2:20:60. A high reversible capacity of 888 mAh g⁻¹ is delivered over 100 cycles at a current density of 100 mA g⁻¹. Even at a current density of 5000 mA g⁻¹, the discharge capacity could still reach 173 mAh g⁻¹. Such excellent electrochemical performances of the NiFe₂O₄ nanoplates are contributed to the short Li⁺ diffusion distance of the nanosized building blocks and the synergetic effect of the Ni²⁺ and Fe³⁺ ions.

Formic acid (FA) and methanol, as convenient hydrogen-containing materials, are most widely used for fuel cells. However, using suitable and low-cost catalysts to further improve their energy performance still is a matter of great significance. Herein, PdCo and PdCo@Pd nanocatalysts (NCs) are successfully prepared by the facile method. Pd 3d binding energy decreases due to the presence of Co. Consequently, PdCo@Pd NCs exhibit high catalytic activity and selectivity toward FA dehydrogenation at room temperature. The gas-generation rate at 30 min is 65.4 L h⁻¹ g⁻¹. PdCo/C has the worst catalytic performance in this reaction, despite the fact that it has a high gas-generation rate in the initial 30 min. Furthermore, both PdCo and PdCo@Pd NCs have enhanced electrocatalytic performance toward methanol oxidation. Their maximum currents are 966 and 1205 mA mg⁻¹, respectively, which is much higher than monometallic Pd/C.

Hierarchical porous core–shell NiFe₂O₄@TiO₂ nanorods have been fabricated with the help of hydrothermal synthesis, chemical bath deposition, and a subsequent calcinating process. The nanorods with an average diameter of 48 nm and length of about 300–600 nm turn out have a highly uniform morphology and are composed of nanosized primary particles. Owing to the synergistic effect of individual constituents as well as the hierarchical porous structure, the novel core–shell NiFe₂O₄@TiO₂ nanorods exhibit superior electrochemical performance when evaluated as anode materials for lithium-ion batteries. At the current density of 100 mA g⁻¹, the composite exhibits a reversible specific capacity of 1034 mAh g⁻¹ up to 100 charge–discharge cycles, which is much higher than the uncoated NiFe₂O₄ nanorods. Even when cycled at 2000 mA g⁻¹, the discharge capacity could still be maintained at 358 mAh g⁻¹.

Core–shell hierarchical porous carbon spheres (HPCs) were synthesized by a facile hydrothermal method and used as host to incorporate sulfur. The microstructure, morphology, and specific surface areas of the resultant samples have been systematically characterized. The results indicate that most of sulfur is well dispersed over the core area of HPCs after the impregnation of sulfur. Meanwhile, the shell of HPCs with void pores is serving as a retard against the dissolution of lithium polysulfides. This structure can enhance the transport of electron and lithium ions as well as alleviate the stress caused by volume change during the charge–discharge process. The as-prepared HPC-sulfur (HPC-S) composite with 65.3 wt % sulfur delivers a high specific capacity of 1397.9 mA h g⁻¹ at a current density of 335 mA g⁻¹ (0.2 C) as a cathode material for lithium–sulfur (Li-S) batteries, and the discharge capacity of the electrode could still reach 753.2 mA h g⁻¹ at 6700 mA g⁻¹ (4 C). Moreover, the composite electrode exhibited an excellent cycling capacity of 830.5 mA h g⁻¹ after 200 cycles.