Co₃V₂O₈ Sponge Network Morphology Derived from Metal–Organic Framework as an Excellent Lithium Storage Anode Material

Metal–organic framework (MOF)-based synthesis of battery electrodes has presntly become a topic of significant research interest. Considering the complications to prepare Co₃V₂O₈ due to the criticality of its stoichiometric composition, we report on a simple MOF-based solvothermal synthesis of Co₃V₂O₈ for use as potential anodes for lithium battery applications. Characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution electron microscopy, and porous studies revealed that the phase pure Co₃V₂O₈ nanoparticles are interconnected to form a sponge-like morphology with porous properties. Electrochemical measurements exposed the excellent lithium storage (∼1000 mAh g^–1 at 200 mA g^–1) and retention properties (501 mAh g^–1 at 1000 mA g^–1 after 700 cycles) of the prepared Co₃V₂O₈ electrode. A notable rate performance of 430 mAh g^–1 at 3200 mA g^–1 was also observed, and ex situ investigations confirmed the morphological and structural stability of this material. These results validate that the unique nanostructured morphology arising from the use of the ordered array of MOF networks is favorable for improving the cyclability and rate capability in battery electrodes. The synthetic strategy presented herein may provide solutions to develop phase pure mixed metal oxides for high-performance electrodes for useful energy storage applications

Na₂V₆O₁₆·3H₂O Barnesite Nanorod: An Open Door to Display a Stable and High Energy for Aqueous Rechargeable Zn-Ion Batteries as Cathodes

Owing to their safety and low cost, aqueous rechargeable Zn-ion batteries (ARZIBs) are currently more feasible for grid-scale applications, as compared to their alkali counterparts such as lithium- and sodium-ion batteries (LIBs and SIBs), for both aqueous and nonaqueous systems. However, the materials used in ARZIBs have a poor rate capability and inadequate cycle lifespan, serving as a major handicap for long-term storage applications. Here, we report vanadium-based Na₂V₆O₁₆·3H₂O nanorods employed as a positive electrode for ARZIBs, which display superior electrochemical Zn storage properties. A reversible Zn²⁺-ion (de)­intercalation reaction describing the storage mechanism is revealed using the in situ synchrotron X-ray diffraction technique. This cathode material delivers a very high rate capability and high capacity retention of more than 80% over 1000 cycles, at a current rate of 40C (1C = 361 mA g^–1). The battery offers a specific energy of 90 W h kg^–1 at a specific power of 15.8 KW kg^–1, enlightening the material advantages for an eco-friendly atmosphere

Aqueous Magnesium Zinc Hybrid Battery: An Advanced High-Voltage and High-Energy MgMn₂O₄ Cathode

Driven by energy demand and commercial necessities, rechargeable aqueous metal ion batteries (RAMBs) have gained increasing attention over the last few decades as high-power and high-energy hubs for large-scale and ecofriendly energy storage devices (ESDs). However, recently explored RAMBs still do not provide the performance needed in order to be realized in grid-scale storage operations due to their poor electrochemical stability, low capacity, low working voltage, and apparently low specific energies. Herein, we have fabricated a new RAMB using MgMn₂O₄ as the cathode and zinc as the anode for the first time. The stable electrochemical performance of this RAMB at high current rates (∼80% capacity retention at 500 mA g^–1 after 500 cycles) and a very high specific energy of 370 Wh kg^–1 at a specific power of 70 W kg^–1 make this newcomer to the family of RAMBs a serious contender for the exploration of safe and green ESDs in the near future

Monoclinic-Orthorhombic Na_1.1Li_2.0V₂(PO₄)₃/C Composite Cathode for Na⁺/Li⁺ Hybrid-Ion Batteries

Monoclinic Li₃V₂(PO₄)₃ (LVP) has been considered a promising cathode material for lithium-ion batteries for the past decade because of its high average potential (>4.0 V) and specific capacity (197 mAh g^–1). In this paper, we report a new monoclinic-orthorhombic Na_1.1Li_2.0V₂(PO₄)₃/C (NLVP/C) composite cathode synthesized from monoclinic LVP via a soft ion-exchange reaction for use in Na⁺/Li⁺ hybrid-ion batteries. High-resolution synchrotron X-ray diffraction (XRD), thermal studies, and electrochemical data confirm room temperature stabilization of the monoclinic-orthorhombic NLVP/C composite phase. Specifically, we report the application of a monoclinic-orthorhombic NLVP/C composite as cathode material in a Na half-cell. The cathode delivered initial discharge capacities of 115 and 145 mAh g^–1 at a current density of 7.14 mA g^–1 in the 2.5–4 and 2.5–4.6 V vs Na/Na⁺ potential windows, respectively. In the lower potential window (2.5–4 V), the composite electrode demonstrated a two-step voltage plateau during the insertion and extraction of Na⁺/Li⁺ ions. Corresponding in situ synchrotron XRD patterns recorded during initial electrochemical cycling clearly indicate a series of two-phase transitions and confirm the structural stability of the NLVP/C composite cathode during insertion and extraction of the hybrid ions. Under extended cycling, excessive storage of Na ions resulted in the gradual transformation to the orthorhombic NLVP/C symmetry due to the occupancy of Na ions in the available orthorhombic sites. Moreover, the estimated average working potential and energy density at the initial cycle for the monoclinic-orthorhombic NLVP/C composite cathode (3.47 V vs Na/Na⁺ and 102.5 Wh kg^–1, respectively) are higher than those of the pyro-synthesized rhombohedral Na₃V₂(PO₄)₃ (3.36 V vs Na/Na⁺ and 88.5 Wh kg^–1) cathode. Further, the cathode performance of the composite material was significantly higher than that observed with pure monoclinic LVP under the same electrochemical measurement conditions. The present study thus showcases the feasibility of using a soft ion-exchange reaction at 150 °C to facilitate the formation of composite phases suitable for rechargeable hybrid-ion battery applications

An Enhanced High-Rate Na₃V₂(PO₄)₃‑Ni₂P Nanocomposite Cathode with Stable Lifetime for Sodium-Ion Batteries

Herein, we report on a high-discharge-rate Na₃V₂(PO₄)₃-Ni₂P/C (NVP-NP/C) composite cathode prepared using a polyol-based pyro synthesis for Na-ion battery applications. X-ray diffraction and electron microscopy studies established the presence of Na₃V₂(PO₄)₃ and Ni₂P, respectively, in the NVP-NP/C composite. As a cathode material, the obtained NVP-NP/C composite electrode exhibits higher discharge capacities (100.8 mAhg^–1 at 10.8 C and 73.9 mAhg^–1 at 34 C) than the NVP/C counterpart electrode (62.7 mAhg^–1 at 10.8 C and 4.7 mAhg^–1 at 34 C), and the composite electrode retained 95.3% of the initial capacity even after 1500 cycles at 16 C. The enhanced performance could be attributed to the synergetic effect of the Ni₂P phase and nanoscale NVP particles, which ultimately results in noticeably enhancing the electrical conductivity of the composite. The present study thus demonstrates that the Na₃V₂(PO₄)₃-Ni₂P/C nanocomposite is a prospective candidate for NIB with a high power/energy density