Aqueous zinc‐ion batteries (AZIBs) attract much attention owing to their high safety, environmentally friendliness and low cost. However, the unsatisfactory performance of cathode materials is one of the unsolved important factors for their widespread application. Herein, we report NH4V4O10 nanorods with Mg2+ ion preinsertion (Mg‐NHVO) as a high‐performance cathode material for AZIBs. The preinserted Mg2+ ions effectively improve the reaction kinetics and structural stability of NH4V4O10 (NHVO), which are confirmed by electrochemical analysis and density functional theory calculations. Compared with pristine NHVO, the intrinsic conductivity of Mg‐NHVO is improved by 5 times based on the test results of a single nanorod device. Besides, Mg‐NHVO could maintain a high specific capacity of 152.3 mAh g−1 after 6000 cycles at the current density of 5 A g−1, which is larger than that of NHVO (only exhibits a low specific capacity of 30.5 mAh g−1 at the same condition). Moreover, the two‐phase crystal structure evolution process of Mg‐NHVO in AZIBs is revealed. This work provides a simple and efficient method to improve the electrochemical performance of ammonium vanadates and enhances the understanding about the reaction mechanism of layered vanadium‐based materials in AZIBs.

Lithium supply shortages have prompted the search for alternatives to widespread grid system applications. Potassium-ion batteries (PIBs) have emerged to promising candidates for this purpose. Nonetheless, the large radius of K (1.38 Å) impedes the march of satisfactory cathode materials. Here, we used solid-phase synthesis to prepare a layered K MnO ·0.25H O (KMO) cathode, comprising alternately connected MnO octahedra with a large interlayer spacing (0.64 nm) to accommodate the migration and transport of K ions. The cathode material achieved initial specific capacities of 102.3 and 88.1 mA h g at current densities of 60 mA g and 1 A g , respectively. The storage mechanism of K ions in PIBs was demonstrated ex situ using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs.

Polyaniline (PANI) is a promising electrode material for supercapacitors, but its reported specific capacitance is much lower than its theoretical capacitance. This is because the PANI molecular chains are tightly packed, and the electrolyte is left with a difficult path to penetrate into the interior regions of PANI. Large anions can be doped into PANI and expand the distance between adjacent PANI molecular chains, thereby increasing the utilization of PANI. In this work, Nafion-doped PANI was synthesized by in situ chemical polymerization in aniline monomer and Nafion solution and the Nafion content was tuned to improve the overall performance. The specific capacitance of Nafion-doped PANI with an optimized Nafion content (4.76 wt %) reached 603.9 and 378.4 F/g at 1 and 50 mV/s), which are both higher than that of PANI (580.0 and 347.7 F/g at 1 and 50 mV/s). The capacitance retention of Nafion (16.67 wt %)-doped PANI was 64.89 % after 1000 cycles, which is better than that of PANI alone (20.25 %). This work provides a facile approach to increasing the utilization of PANI as an electrode material for supercapacitors.[a] X.

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Lithium supply shortages have prompted the search for alternatives to widespread grid system applications. Potassium-ion batteries (PIBs) have emerged to promising candidates for this purpose. Nonetheless, the large radius of K+ (1.38 Å) impedes the march of satisfactory cathode materials. Here, we used solid-phase synthesis to prepare a layered K0.37MnO2·0.25H2O (KMO) cathode, comprising alternately connected MnO6 octahedra with a large interlayer spacing (0.64 nm) to accommodate the migration and transport of K+ ions. The cathode material achieved initial specific capacities of 102.3 and 88.1 mA h g-1 at current densities of 60 mA g-1 and 1 A g-1, respectively. The storage mechanism of K+ ions in PIBs was demonstrated ex situ using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs.