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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 (0.71 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, x-ray photoelectron spectroscopy, and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs. [ABSTRACT FROM AUTHOR]

Although the performance of the self-standing electrode has been enhanced for aqueous zinc-ion batteries (AZIBs), it is necessary to explore and analyse the deep modification mechanism (especially interface effects). Herein, density functional theory (DFT) calculations are applied to investigate the high-performance cathode based on the VO2/carbon cloth composites with heterostructures interface (H-VO2@CC). The adsorption energy comparisons and electron structure analyses verify that H-VO2@CC has extra activated sites at the interface, enhanced electrical conductivity, and structural stability for achieving high-performance AZIBs due to the presence of built-in electric field at the interfaces. Accordingly, the designed self-standing H-VO2@CC cathode delivers higher rate capacity, longer-life cyclability, and faster electronic/ion transmission kinetics benefiting from the synergistic effects. The risks of active material shedding and dissolution during the dis/charge process of two cathodes were evaluated via ex-situ ultraviolet—visible (UV-vis) spectrum and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) technique. Finally, this investigation also explores the charge storage mechanism of H-VO2@CC through various ex-situ and in-situ characterization techniques. This finding can shed light on the significant potential of heterostructures interface engineering in practical applications and provide a valuable direction for the development of cathode materials for AZIBs and other metal-ion batteries. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc-ion batteries (AZIBs) have garnered widespread attention as a new large-scale energy storage candidate owing to their low cost and high theoretical capacity. Because of the unique divalent state of Zn2+ and the existence of a strong electrostatic repulsion phenomenon, researchers are currently focusing on how to prepare high-performance cathode materials. In this study, we synthesized aluminum vanadate (AlV3O9) as a cathode material for AZIBs using a solvothermal method. Al3+ acted as a pillar in the resultant structure and stabilized it. Furthermore, this large interlayer spacing enhanced the ion diffusion coefficient and accelerated the ion transport process. Because of these advantages, the AlV3O9 (AVO) cathode exhibited excellent electrochemical performance, including a high capacity of 421.0 mA h g−1 at 0.1 A g−1 and a stable rate capability of 348.2 mA h g−1 at 1 A g−1. Moreover, it exhibited a specific capacity of 202 mA h g−1 even at a high current density of 3 A g−1 (the capacity retention rate reached 84.38% after 1600 cycles). The prepared ZIBs presented a high power density of 366.6 W kg−1 at an energy density of 286 W h kg−1. These extraordinary results indicate the great application potential of AVO as a cathode material for AZIBs. [ABSTRACT FROM AUTHOR]

• The reversible storage of Mg2+ in PANI at non-aqueous MIBs was first proved. • The binder-free flexible cathode was prepared by simple in-situ polymerization. • The CC stabilized the structure and improved conductivity of the cathode. • The double-ion storage mechanism provides capacity for the PANI/CC. • The capacity retention of 97.25% was obtained after 1500 cycles at 1 A g−1. Magnesium ion batteries (MIBs) attracted much attention in recently years due to the advantages of high theoretical capacity and low cost. However, the strong polarization effect of Mg2+ cause slow diffusion rate, hindering the development of MIBs. Herein, we designed and synthesized a binder-free polyaniline array/carbon cloth (PANI/CC) as cathode for MIBs. Given the benefit of improved electrical conductivity and alleviated agglomeration, the cathode exhibits enhanced electrochemical performance compared with the pure polyaniline cathode in MIBs. The PANI/CC cathode displays the highest specific capacity of 219 mA h g−1 at 200 mA g−1 and the capacity retention of 97.25% after over 1500 cycles at 1 A g−1. Then, the reversible redox transformation between quinone rings and benzene rings during charging and discharging process was demonstrated by the ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ Raman spectra. In addition, PANI/CC shows an initial capacity of 75 mA h g−1 at 50 mA g−1 in PANI/CC //Mg(TFSI) 2 // MNTO full cell. Our work demonstrates that PANI/CC is a promising cathode for MIBs, which may offer new insight for the development for high-performance MIBs. [ABSTRACT FROM AUTHOR]

• Hydrated zinc vanadate was formed from V 2 O 5 via an initial activated phase transformation process induced by H 2 O. • Hydrated zinc vanadate combines two modification strategies of special morphology and crystal structure adjustment. • Hydrated zinc vanadate exhibited considerable exhibited enhanced cycle performance and improved reaction kinetics. • Activated phase transformation was demonstrated to be an effective method to improve the electrochemical performance. Aqueous zinc-ion batteries have great potential applications in the field of energy storage; however, their development is limited by the low availability of high-performance cathode materials. In this study, the phase transformation of Yolk-shell V 2 O 5 (YS-V 2 O 5) to hydrated zinc vanadate (Zn 0.34 V 2 O 5 •0.37H 2 O; HZVO) was driven by water molecules via electrochemical activation. The resulting HZVO was used as the host material for the insertion/extraction of zinc ions. The HZVO material exhibited a specific capacity of 85.2% (113.3 mA h g−1) after 1000 cycles at a current density of 8.0 A g−1. Moreover, the diffusion coefficient of zinc ions was larger than that of conventional cathode materials, ranging from 10−9 to 10−8 cm2 s−1. We believe that our approach can contribute to the development of advanced cathode materials for application in zinc-ion batteries. [ABSTRACT FROM AUTHOR]

Lack of suitable cathode materials is one of the critical factors that hinder the advancement of aqueous zinc-ion batteries (AZIBs). Although low valent vanadium-based materials as zinc-ion host have high theoretical capacity, ineffectively discharge limits its application for AZIBs owning to the inherently unsuitable structure and physicochemical performance. Therefore, a ZnO/ZnV 2 O 4 composite hollow microsphere (ZVO-3) was fabricated via a facile free-template solvothermal method and assembled as a cathode for AZIBs. When a first charge strategy is adopted, the ZVO-3 cathode exhibits approximately an initial columbic efficiency of 97%, high-rate capacity (93.3 mAh g−1 at 8.0 ​A ​g−1), superior cycling ability (338 mAh g−1 at 0.1 ​A ​g−1, a capacity retention of 70% after 50 cycles) and excellent long-term cycling performance. Furthermore, the results of electrochemical dynamics indicate that the pseudo-capacitance dominated electrode reaction process with fast diffusion efficiency. This work not only exploits a method for designing hollow structures of ZVO-3, but also shed lights on the application of charged-optimized low valent vanadium-based cathode for AZIBs or other multivalent-ion batteries. [Display omitted] • ZnO/ZnV 2 O 4 composite is synthesized by free-template solvothermal method. • Charged-optimized strategy robust the specific capacity of ZnO/ZnV 2 O 4 cathode. • Superior rate performance is attributed to the hollow structure. • The fast diffusion coefficient is achieved by the pseudo-capacitance behaviors. [ABSTRACT FROM AUTHOR]