VOPO4⋅2H2O Nanosheet Cathode for Enhanced Sodium Storage

Abstract

Na-ion batteries (SIBs) are anticipated to capture a broad development space in the field of large-scale energy storage due to the abundant sodium resources. High-performance cathode materials are very critical. VOPO 4 •2H 2 O with a two-dimensional (2D) layered structure is a very promising candidate for SIBs because of its high working voltage and theoretical specific capacity. Herein, a simple one-step reflux method is designed to fabricate a cathode of VOPO 4 •2H 2 O nanosheets. It exhibits a high average operating potential of ∼3.5 V, remarkable specific capacity (e.g., 135 mAh g −1 at 0.05 C), favorable high current charge-discharge ability (e.g., 58 mAh g −1 even at 20 C) as well as extralong cyclability (e.g., 0.026% capacity fading rate for per cycle at 20 C during 1000 cycles). The kinetic analysis implies that the superior sodium storage performance is mainly benefiting from the advantages of unique nanosheet structure, accelerating the rapid Na-ion diffusion.

A Binder‐Free and Flexible VOPO4/CNT Film as Cathode for Aqueous Rechargeable Zn‐Metal Battery

“…84–0111). [ 37,38 ] The additional low‐intensity diffraction peaks also correspond to the (101), (200), (201), and (202) diffraction planes of VOPO 4 .2H 2 O, confirming the phase purity in the bulk VP sample. The VP/fCNT‐P sample exhibits a similar diffraction pattern with a slight shift in the peak positions compared to the bulk VP.…”

“…Upon deconvolution of the V 2p XPS spectra, the V 2p 3/2 and V 2p 1/2 doublets in the VP sample ( Figure a) signify the dominance of the V 5+ (519.0 and 526.6 eV) oxidation state with a small contribution from the V 4+ (517.3 and 525.7 eV) state. [ 38 ] On the other hand, the V 2p spectra in the composite samples (Figures 4b,c) show a small shift in the binding energy to the lower values and an increased peak intensity for the V 4+ state (the binding energy comparison is given in Table S1, Supporting Information). This difference originates from the reduction of a significant fraction of V 5+ to V 4+ in the composites due to the interaction of the VP phase with the electron‐rich fCNT (Figure 4b).…”

“…[41] The ATR-FTIR spectra of the samples in Figure 3c also show several intense peaks related to the bending and stretching modes of the V-O (940 and 673 cm −1 ) and P-O (1080 and 950 cm −1 ) bonds from the VOPO 4 phase. [38,42,43] A slight shift of the FTIR peaks in VP/fCNT-P and VP/fCNT-F indicates the interaction of the VP nanoflakes with fCNTs.…”

Electrodeposited Layered Sodium Vanadyl Phosphate (NaxVOPO4·nH2O) as Cathode Material for Aqueous Rechargeable Zinc Metal Batteries

“…The scope of employing VOPO 4 as the cathode material is already known for several nonaqueous battery chemistries, where the ionic radius of the metal cation of interest (e.g., Li + , Na + , K + , etc.) is small. − However, VOPO 4 as the cathode material in ARZMBs is still in the early stages of development. The large hydrated ionic radius of Zn 2+ ions (≈4.3 Å) in mild aqueous electrolytes − makes it difficult for the pristine VOPO 4 host with a low interlayer spacing (≈4 to 7 Å depending on the synthetic procedure and phase) ,− to withstand/relieve the morphological strain developed during repeated Zn 2+ insertion/extraction processes.…”

Ionic Liquids Achieve the Exfoliation of Ultrathin Two-Dimensional VOPO4·2H2O Crystalline Nanosheets: Implications on Energy Storage and Catalysis

“…The composite metal oxidation of vanadium-phosphorus oxides (V-P-O) is widely used in the chemical industry and energy storage field, and the structure plays an important role in their performance. VOPO 4 ·2H 2 O (HVPO), the typical composite metal oxidation of V-P-O, is characteristic of corner-sharing VO 6 octahedra linking to PO 4 tetrahedra to form a layered structure, and the H of lattice water in the interlayer would form a strong H (H 2 O) ···O (VOPO 4 ) hydrogen bond with the oxygen on the layered plates with an interlayer spacing of 7.4 Å. , HVPO is one of the renowned heterogeneous catalysts for selective oxidation of hydrocarbons in industries, , and the polyanionic VOPO 4 laminates can serve as a very versatile host to prepare functional organic–inorganic hybrid materials. , Also, it has a high charge/discharge voltage platform and conductivity, showing good potential and development in the field of vanadium batteries. − There are some recent reports on the applications of two-dimensional (2D) VOPO 4 nanomaterials in Table S1, which show promising applications in energy storage and catalysis. However, most of them used the layered (the best is less than six atomic layers) structure and may cause a reduction in crystallinity.…”