Potassium-ion batteries (KIBs) have recently attracted intensive attention because of the abundant potassium resources and their low cost and high safety. However, the major challenge faced by KIBs lies in the lack of stable and high-capacity materials for the intercalation/deintercalation of large-size potassium ions. A unique pistachio-shuck-like MoSe /C core/shell nanostructure (PMC) is synthesized herein as an advanced anode for boosting the performance of KIBs. This PMC is featured with a few layers of molybdenum selenide as the core with an expanded interlayer spacing of ≈0.85 nm, facilitating the intercalation/deintercalation of K ions, and a thin amorphous carbon as the shell, which can confine the active molybdenum selenide nanosheets during cycling for maintaining the high structural stability. Most importantly, as a whole, the PMC has the advantages of reducing the surplus hollow interior space for improving its packing density and buffering the volume expansion during the K-ion intercalation for further enhancing the stability. As a consequence, the PMC shows a very high capacity of 322 mAh g at 0.2 A g over 100 cycles, and can still remain 226 mAh g at 1.0 A g for a long period of 1000 cycles, which is among the best-reported KIBs anodes.

The solid polymer electrolyte (SPE) is one type of the most promising solid‐state electrolytes for next‐generation solid‐state batteries, due to its good compatibility with Li‐metal, high flexibility, and safety. To compete with currently used conventional Li‐ion batteries in energy density, SPEs must be integrated with high energy density cathode of LiNixMnyCozO2 (x + y + z = 1, 0.5 < x < 1) (NMC). However, the application of SPEs with NMC is limited by the narrow redox window of single SPEs and interfacial decomposition of SPEs by NMC. To overcome these challenges, a strategy is proposed utilizing a polymeric‐catholyte/‐anolyte‐composed dual‐polymer electrolyte and a cathode coating: a low voltage stable polyether works as a separator and stabilizes the interface with Li‐metal, while a high voltage stable polyoxalate functions as the catholyte and NMC particles are precoated by TiO2. This cell model not only widens the voltage window of the electrolyte system, but also protects the polyoxalate in the cathode from interfacial decomposition. With this strategy, cycling stability of all‐solid‐state Li‐metal/LiNi0.6Mn0.2Co0.2O2 (NMC622) cells is significantly improved. Meanwhile, large volume expansions of deposited lithium on both the Li‐metal anode and the copper collector are observed, which deserve more attention in the investigation of all‐solid‐state cells.

Morphological and magnetic anisotropy can be combined in colloidal assembly to create unconventional secondary structures. We show here that magnetite nanorods interact along a critical angle, depending on their aspect ratios and assemble into body-centered tetragonal colloidal crystals. Under a magnetic field, size-dependent attractive and repulsive domains develop on the ends and center of the nanorods, respectively. Our joint experimentcomputational multiscale study demonstrates the presence of a critical angle in the attractive domain, which defines the equilibrium bonding states of interacting rods and leads to the formation of non-close-packed yet hard-contact tetragonal crystals. Small-angle x-ray scattering measurement attributes the perfect tetragonal phase to the slow assembly kinetics. The crystals exhibit brilliant structural colors, which can be actively tuned by changing the magnetic field direction. These highly ordered frameworks and well-defined three-dimensional nanochannels may offer new opportunities for manipulating nanoscale chemical transformation, mass transportation, and wave propagation.

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With its inherent zig-zag layered structure and open framework, NaTiO (NTO) is a promising anode material for potassium-ion batteries (KIBs). However, its poor electronic conductivity caused by large band gap (∼3.7 eV) usually leads to low-performance KIBs. In this work, we synthesize the fluff-like hydrogenated NaTiO (HNTO) nanowires grown on N-doped carbon sponge (CS) as a binder-free and current-collector-free flexible anode for KIBs (denoted as HNTO/CS). High-resolution X-ray photoelectron spectroscopy (XPS) and electron spin-resonance spectroscopy (ESR) confirm the existence of Ti-OHs and O vacancies in HNTO. The first-principles calculation discloses that both Ti-OHs and O vacancies are equivalent to n-type doping because they can shift the Fermi level up to the conduction band, thus leading to a higher electronic conductivity and better performance for KIBs. In addition, the N-doped CS can further reinforce the conductivity and avoid the aggregation of HNTO nanowires during cycling. As a result, the as-made HNTO/CS can deliver a capacity of 107.8 mAh g at 100 mA g after 20 cycles, and keep the capacity of 90.9% and 82.5% after 200 and 1555 cycles, respectively, much better than the samples without hydrogenation treatment or N-doped CS and reported KTi O-based materials. Our work highlights the importance of hydrogenation treatment and N-doped CS in enhancing the electrochemical property for KIBs.