Penetrating into the inner surface of porous metal-oxide nanostructures to encapsulate the conductive layer is an efficient but challenging route to exploit high-performance lithium-ion battery electrodes. Furthermore, if the bonding force on the interface between the core and shell was enhanced, the structure and cyclic performance of the electrodes will be greatly improved. Here, vertically aligned interpenetrating encapsulation composite nanoframeworks were assembled from Cl − /SO 3 2− -codoped poly(3,4-ethylenedioxythiophene) (PEDOT) that interpenetrated and coated on porous Fe 2 O 3 nanoframeworks (PEDOT-IE-Fe 2 O 3 ) via a onestep Fe 3+ -induced in situ growth strategy. Compared with conventional wrapped structures and methods, the special PEDOT-IE-Fe 2 O 3 encapsulation structure has many advantages. First, the codoped PEDOT shell ensures a high conductive network in the composites (100.6 S cm −1 ) and provides interpenetrating fast ion/ electron transport pathways on the inner and outer surface of a single composite unit. Additionally, the pores inside offer void space to buffer the volume expansion of the nanoscale frameworks in cycling processes. In particular, the formation of Fe−S bonds on the organic−inorganic interface (between PEDOT shell and Fe 2 O 3 core) enhances the structural stability and further extends the cell cycle life. The PEDOT-IE-Fe 2 O 3 was applied as lithium-ion battery anodes, which exhibit excellent lithium storage capability and cycling stability. The capacity was as high as 1096 mA h g −1 at 0.05 A g −1 , excellent rate capability, and a long and stable cycle process with a capacity retention of 89% (791 mA h g −1 ) after 1000 cycles (2 A g −1 ). We demonstrate a novel interpenetrating encapsulation structure to highly enhance the electrochemical performance of metal-oxide nanostructures, especially the cycling stability, and provide new insights for designing electrochemical energy storage materials.

Multivalent metal‐ion hybrid capacitors (MMHCs) have drawn much attention in recent years because of their advantages of high energy density (similar to metal‐ion batteries) as well as high power density, high rate capability, and ultra‐long cycle life. However, there are still challenges in developing high‐performance MMHCs, e. g., high‐capacity capacitive materials are particularly needed to be developed to match high‐energy battery‐type electrodes. Therefore, designing novel electrode materials and exploring suitable electrolytes are of particular importance. Herein, we focus on the recent progress of MMHCs in relation to their cathode/anode materials, electrolytes, electrochemical properties, and energy storage mechanisms. Additionally, the current challenges or bottlenecks and future research trends regarding MMHCs are summarized. This review provides a comprehensive understanding of the research framework of MMHCs and will be beneficial in the development of high‐performance MMHC devices.

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