This review is focused on the recent progress and strategies in the fabrication of high performance anode materials for Na-ion batteries.

Designed as a high-capacity, high-rate, and long-cycle life anode for sodium ion batteries, exfoliated-SnS2 restacked on graphene is prepared by the hydrolysis of lithiated SnS2 followed by a facile hydrothermal method. Structural and morphological characterizations demonstrate that ultrasmall SnS2 nanoplates (with a typical size of 20-50 nm) composed of 2-5 layers are homogeneously decorated on the surface of graphene, while the hybrid structure self-assembles into a three-dimensional (3D) network architecture. The obtained SnS2/graphene nanocomposite delivers a remarkable capacity as high as 650 mA h g(-1) at a current density of 200 mA g(-1). More impressively, the capacity can reach 326 mA h g(-1) even at 4000 mA g(-1) and remains stable at ∼610 mA h g(-1) without fading up to 300 cycles when the rate is brought back to 200 mA g(-1). The excellent electrochemical performance is attributed to the synergetic effects between the ultrasmall SnS2 and the highly conductive graphene network. The unique structure can simultaneously facilitate Na(+) ion diffusion, provide more reaction sites, and suppress aggregation and volume fluctuation of the active materials during prolonged cycling.

Metal sulfides (designated as MSs, M=Fe, Co, Ni, Cu, Mo, Ti, W, Sn, Sb, etc.) have recently attracted increasing research interest worldwide. Benefiting from their high electrochemical activities, these MSs will play significant roles for low-cost and environmentally friendly energy storage/conversion systems. In this review, we summarize the up-to-date progress on the rational design and efficient synthesis of MSs with controlled morphologies, sizes, compositions, and micro/nanostructures, along with their applications as electrode materials for lithium/sodium/magnesium-ion batteries and supercapacitors, and electrocatalysts for oxygen reduction reaction and hydrogen evolution reaction. The associated challenges, problem-solving strategies, and future trends to broaden the horizons of MSs for energy-related applications will also be presented. Please do not adjust marginsPlease do not adjust margins exfoliated to few-layered structures, which even display metallic conductivity. Moreover, layered MSs often provide appropriate interlayer spacing to enable fast and stable ion intercalation/de-intercalation. This is of great benefit for achieving high-rate and long-life electrodes of secondary batteries. Generally speaking, MSs especially with the layered structure are more likely to expose active sites for H adsorption than MOs, 22 leading to their superior electrocatalytic performance for HER. Recently, MCs and MNs are also considered as efficient electro-catalysts for ORR and HER, 23 but their fabrication usually requires multistep process and high temperature treatment, which makes the synthesis costly, complicated, or even uneconomical. To give an overall consideration, MSs are multifunctional materials and, paying attention to their progress in energy-related applications towards more prosperities is desired and necessary. Apart from the inherent advantages of MSs, it is well established that the composition, crystalline phase, structural and morphological features of functional materials, and the sur/inter-face properties between the electrode and electrolyte, would also greatly influence the performance of these distinctive MSs in energy-related systems. There is thereby an urgent need but it is still a significant challenge to rationally design and delicately synthesize the electroactive MSs for advanced LIBs, SIBs, MIBs, SCs, MABs, and hydrogen utilization. In order to display such a "structure-function" relationship, in this review, we mainly address the topic on the ingenious design and controllable synthesis of unique MSs for high-efficiency electrochemical energy storage/conversion. To make it a feasible task, we will introduce the recent progress of metal sulfides in four parts, that is, "Lithium-Ion Batteries", "Next-Generation Batteries and Supercapacitors", "Oxygen Reduction Reaction", and "Hydrogen-Related Applications". The advantages and limitations will be discussed, and the corresponding problem-solving strategies associated with structural/compositional engineering are also highlighted. Fina...