Binders play an important role in battery systems. The lithium-sulfur (Li-S) batteries have poor cycling performance owing to large volume alteration of sulfur and shuttle effect. Herein, a novel water-soluble functional binder (named GN-BA) is prepared by the cross-linking effect between gelatin and boric acid. The excellent binder can effectively maintain the integrated electrode stable, buffer the volume changes, prevent active materials exfoliation from current collectors, and anchor polysulfides by chemical bonding. Sulfur electrodes in this binder also exhibit a loosely stacked porous structure, which is advantageous to the electrolyte permeation and fast ion diffusion. X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and density functional theory calculations further verified that the binder can anchor polysulfides by forming BOLi, COLi, and CNLi chemical bonds. At 0.5 C, a high initial capacity of 980 mA h g −1 can be obtained, which is higher than those sulfur cathodes with traditional poly(vinylidene fluoride) binder. When the sulfur loading is up to 5.0 mg cm −2 , a high areal specific capacity of 5.7 mA h cm −2 and excellent cycling stability are achieved. This study proposes an economical and environmentally friendly strategy for the construction of advanced binders and promotes the practical application of high-energy Li-S batteries.

Heterostructure engineering is one of the most promising modification strategies for reinforcing Na + storage of transition metal sulfides. Herein, based on the spontaneous hydrolysis-oxidation coupling reaction of transition metal sulfides in aqueous media, a VO x layer is induced and formed on the surface of VS 2 , realizing tight combination of VS 2 and VO x at the nanoscale and constructing homologous VS 2 /VO x heterostructure. Benefiting from the builtin electric field at the heterointerfaces, high chemical stability of VO x , and high electrical conductivity of VS 2 , the obtained VS 2 /VO x electrode exhibits superior cycling stability and rate properties. In particular, the VS 2 /VO x anode shows a high capacity of 878.2 mAh g −1 after 200 cycles at 0.2 A g −1 . It also exhibits long cycling life (721.6 mAh g −1 capacity retained after 1000 cycles at 2 A g −1 ) and ultrahigh rate property (up to 654.8 mAh g −1 at 10 A g −1 ). Density functional theory calculations show that the formation of heterostructures reduces the activation energy for Na + migration and increases the electrical conductivity of the material, which accelerates the ion/electron transfer and improves the reaction kinetics of the VS 2 /VO x electrode.

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Metal‐organic frameworks (MOFs) integrate several advantages such as adjustable pore sizes, large specific surface areas, controllable geometrical morphology, and feasible surface modification. Benefiting from these appealing merits, MOFs have recently been extensively explored in the field of advanced secondary batteries. However, a systematic summarization of the specific functional units that these materials can act as in batteries as well as their related design strategies to underline their functions has not been perceived to date. Motivated by this point, this review dedicates to the elucidation of diverse functions of MOFs for batteries, which involve the electrodes, separators, interface modifiers, and electrolytes. Particularly, the main engineering strategies based on the physical and chemical features to enable their enhanced performance have been highlighted for the individual functions. In addition, perspectives and possible research questions in the future development of these materials have also been outlined. This review captures such progress ranging from fundamental understanding and optimized protocols to multidirectional applications of MOF‐based materials in advanced secondary batteries.

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