This review summarizes the development history, basic characteristics, special co-intercalation mechanism, origin of the superior performance of ether-based electrolytes in sodium-ion batteries and their advancements in other batteries.

In lithium metal batteries (LMB), unrestricted growth of lithium dendrites will pierce the separator and cause an internal short circuit. Therefore, we designed modified separator with an InN thin layer, which could be in situ converted into a binary mixed-modified layer of Li–In alloy and Li3N during the lithium plating/stripping process. Among them, Li–In alloy induces the lateral growth of lithium dendrites and prevents the separator from being pierced; Li3N balances ion distribution at the lithium anode/separator interface, which is beneficial to inhibit the growth of lithium dendrites. Under the synergistic effect of the two phases, the performance of LMBs was obviously improved. In addition, the separator modification does not need to be carried out in a protective atmosphere and is suitable for large-scale roll-to-roll processing.

Hard carbon (HC) has attracted extensive attention due to its rich material source, environmental non-toxicity, superior sodium storage capacity, and lower sodium storage potential, and is considered most likely to be a commercial anode material for sodium-ion batteries (SIBs). Nevertheless, the limited initial Coulombic efficiency (ICE) of HC is the main bottleneck hindering its practical application. To alleviate this issue, herein, a ZrO2 coating was skillfully constructed by using a facile liquid phase coating method. The ZrO2 coating can act as a physical barrier to prevent direct contact between the HC surface and the electrolyte, thus effectively reducing irreversible sodium adsorption and inhibiting the continuous decomposition of the electrolyte. Meanwhile, this fresh interface can contribute to the generation of a thinner solid electrolyte interface (SEI) with high ionic conductivity. As a result, the ICE of the ZrO2-coated HC electrode can be optimized up to 79.2% (64.4% for pristine HC). Furthermore, the ZrO2-coated HC electrode delivers outstanding cyclic stability so that the capacity retention rate can reach 82.6% after 2000 cycles at 1 A g−1 (55.8% for pristine HC). This work provides a flexible and versatile surface modification method to improve the electrochemical property of HC, and hopefully accelerate the practical application of HC anodes for SIBs.

MOF-based materials are a class of efficient precursors for the preparation of heteroatom-doped porous carbon materials that have been widely applied as anode materials for Na-ion batteries. Thereinto, sulfur is often introduced to increase defects and act as an active species to directly react with sodium ions. Although the sulfur introduction and high surface area can synergistically improve capacity and rate capability, the initial Coulombic efficiency (ICE) and electrical conductivity of carbon material are inevitably reduced. Therefore, balancing sodium storage capacity and ICE is still the bottleneck faced by adsorbent carbon materials. Here, sulfur-encapsulated microporous carbon material with nitrogen, sulfur dual-doping (NSPC) is synthesized by postprocessing, achieving the reduced specific surface area by encapsulating sulfur in micropores, and the increased active sites by edge sulfur doping. The synergy between encapsulation and sulfur doping effectively balances specific capacity, rate capability, and ICE. The NSPC material exhibits capacities of 591.5 and 244.2 mAh g −1 at 0.5 and at 10 A g −1 , respectively, and the ICE is as high as 72.3%. Moreover, the effect of nitrogen and sulfur on the improvement of electron/ion diffusion kinetics is resonantly demonstrated by density functional theory calculations. This synergistic preparation method may reveal a feasible thought for fabricating excellent-performance adsorption-type carbon materials for Na-ion batteries.

Graphene is considered as a promising cathode candidate for Li–O2 batteries because of its excellent electronic conductivity and oxygen adsorption capacity. However, for Li–O2 batteries, the self-stacking effect caused by two-dimensional (2D) structural properties of graphene is not conducive to the rapid oxygen transport and mass transfer process, thereby affecting the electrode kinetics. Here, we successfully prepared three-dimensional (3D) graphene with different scales by plasma-enhanced chemical vapor deposition and physical pulverization strategies, in which CH4 is the carbon source and H2/Ar mixed gas is the etching gas. Meanwhile, we fabricated 3D graphene-based Pt nanocatalysts by an ultraviolet-assisted construction strategy and then applied them in Li–O2 batteries. Systematic studies reveal a special relevance between electrochemical performance and graphene particle size, and the smaller-sized 3D graphene can better maintain the microstructure distribution in both the Pt embedding process and electrochemical applications, which is beneficial to the transport of oxygen and Li ions, lowering the decomposition energy barrier of Li2O2, and further obtaining reduced charge overpotential (0.22 V) and prolonged cycle life for Li–O2 batteries. Finally, we anticipate that this work could promote the practical application of 2D materials and larger-sized 3D materials in Li–O2 batteries.