Sodium-ion battery technologies are known to suffer from kinetic problems associated with the solid-state diffusion of Na in intercalation electrodes, which results in suppressed specific capacity and degraded rate performance. Here, a controllable selective etching approach is developed for the synthesis of Prussian blue analogue (PBA) with enhanced sodium storage activity. On the basis of time-dependent experiments, a defect-induced morphological evolution mechanism from nanocube to nanoflower structure is proposed. Through in situ X-ray diffraction measurement and computational analysis, this unique structure is revealed to provide higher Na diffusion dynamics and negligible volume change during the sodiation/desodiation processes. As a sodium ion battery cathode, the PBA exhibits a discharge capacity of 90 mA h g, which is in good agreement with the complete low spin Fe(C) redox reaction. It also demonstrates an outstanding rate capability of 71.0 mA h g at 44.4 C, as well as an unprecedented cycling reversibility over 5000 times.

Rechargeable lithium-sulfur (Li-S) batteries have recently attracted global research interest due to their high theoretical specific capacity and energy density. To improve the performance and cycling stability of Li-S batteries, a clear understanding of the electrochemical reaction process and the degradation mechanisms of the sulfur redox chemistry are extremely important. In the past few decades, various advanced in situ/operando characterization tools have emerged, which have facilitated the understanding of the degradation mechanisms and the further development of high-performance Li-S batteries. In this review, we have summarized recent significant advances in in situ/operando characterization techniques for Li-S batteries. In particular, because of the existence of the soluble polysulfide species during the charge/discharge process, many creative ideas have been introduced into in situ/operando characterization of the electrochemical process in Li-S batteries.

In situ N-doped mesoporous carbon nanofibers synthesized by depositing magnesium hydroxide (Mg(OH)2) into polyacrylonitrile (PAN) nanofibers and combining carbonization with etching process exhibit excellent supercapacitive performance.

High capacity transition-metal oxides play significant roles as battery anodes benefiting from their tunable redox chemistry, low cost, and environmental friendliness. However, the application of these conversion-type electrodes is hampered by inherent large volume variation and poor kinetics. Here, a binary metal oxide prototype, denoted as nonhierarchical heterostructured Fe O /Mn O porous hollow spheres, is proposed through a one-pot self-assembly method. Beyond conventional heteromaterial, Fe O /Mn O based on the interface of (104) and (222) exhibits the nonhierarchical configuration, where nanosized building blocks are integrated into microsized spheres, leading to the enhanced structural stability and boosted reaction kinetics. With this design, the Fe O /Mn O anode shows a high reversible capacity of 1075 mA h g at 0.5 A g , an outstanding rate capability of 638 mA h g at 8 A g , and an excellent cyclability with a capacity retention of 89.3% after 600 cycles.