LiVPO 4 F: A New Cathode for High-Energy Lithium Ion Capacitors

Guo

ACS Appl. Energy Mater.

et al. 2020

Li-ion capacitors (LICs), a typical hybrid configuration constructed by combining a capacitive cathode and a battery-type anode with Li-salt based organic electrolytes, are drawing research attention to increase energy densities of the existing state-of-the-art supercapacitors. However, the promising future of hybrid devices is injured by the imbalance of electrochemical kinetics and capacities between the battery-like anodes and capacitive cathodes. Herein, we devise a bio-template strategy to synthesize the highly porous carbon and Fe derivatives@carbon (Fe@C) composite from the same precursor of strawberries. The obtained porous carbon shows a sheet-like morphology with a high specific surface area of 2987 m2/g. Electrochemical evaluation of the 2D porous carbon sheet delivers a high specific capacity of 140.3 mAh/g (202 F/g) and excellent rate capability. The achieved mesoporous Fe@C composite delivers a high specific capacity of 576.3 mAh/g at 0.1 A/g, and even 202.8 mAh/g at 10 A/g. A novel LIC assembled using the porous carbon and Fe@C composite as the positive and negative electrodes yields a high energy density of 97 Wh/kg at 250 W/kg. The scalable methodology here paves the way for widespread commercialization of the advanced yet cost-efficient LICs.

Section: Resultsmentioning

confidence: 76%

Green Bio-template Fabrication of Fe Derivatives@Carbon Composites and Porous Carbon Sheets toward Advanced Li-Ion Capacitors as Low-Cost Electrodes

Guo

ACS Appl. Energy Mater.

et al. 2020

“…After selecting the most suitable electrolyte (1 M H 3 PO 4 acetonitrile) for the LiVPO 4 F electrode, ex situ XRD was performed to analyze its structural evolution (Figure 3a and b). Pattern 0 shows the pristine LiVPO 4 F, in which the peak at 22.5° is known as a characteristic peak for it [14] . When charged to 1.1 V, an obvious phase transformation was observed and the peak at 22.5° totally disappeared, along with the appearance of a new peak at 25°, corresponding to the XRD result of delithiated VPO 4 F [16] .…”

Section: Resultsmentioning

confidence: 99%

“…In the following cycles, reversible proton insertion/extraction happened. The XRD pattern and corresponding parameters of LiVPO 4 F are shown in Figure 1a and Table S1, in which all peaks are well indexed to the triclinic structure of LiVPO 4 F. [14] Scanning electron microscopy (SEM) analysis (Figure 1b) reveals that the LiVPO 4 F nanoparticles are aggregated into micron-sized secondary spheres ( � 7 μm). A thin amorphous carbon layer coated on the surface of LiVPO 4 F is illustrated in Figure S2, which is verified to be approximately 2.3 wt % through thermogravimetric analysis (Figure S3).…”

Section: Introductionmentioning

confidence: 99%

VPO₄F Fluorophosphates Polyanion Cathodes for High‐Voltage Proton Storage

Liao

Cao

et al. 2022

Angew Chem Int Ed

Proton batteries are emerging in electrochemical energy storage because of the associated fast kinetics, low cost and high safety. However, their development is hindered by the relatively low energy density due to the limited choice of cathode materials. Herein, metal phosphate polyanion cathodes are proposed as the proton cathode for the first time. Combining experimental results and theoretical simulations, a universal criterion for the proton cathode was put forward. Vanadium fluorophosphate (VPO 4 F) was demonstrated as a promising high-voltage proton cathode material with a specific capacity of 116 mAh g À 1 at a high potential of 1.0 V (vs. SHE). The proton insertion/ extraction mechanism in the VPO 4 F electrode was also verified through X-ray diffraction (XRD) and photoelectron spectroscopy (XPS). Furthermore, the stability of VPO 4 F was investigated in various electrolytes and the optimized electrolyte enabled the stable operation of VPO 4 F for 300 cycles. This work provides new inspiration in the exploitation of new electrode materials for electrochemical proton storage devices.

“…Moreover, the thermal stability of LiVPO 4 F is better than that of LiFePO 4 and LiCoO 2 (Wang et al, 2014 ; Xu et al, 2015 ). If the shortcoming of electronic conductivity is solved, LiVPO 4 F will be an outstanding cathode material (Reddy et al, 2010 ; Ma et al, 2013b ; Satish et al, 2016 ). Some improvements have been adjusted to LiVPO 4 F cathode, such as cation doped, carbon coated and various synthesized routes (Wang et al, 2013a ; Liu et al, 2016 ; Wu et al, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

Effect of Environmental Temperature on the Content of Impurity Li3V2(PO4)3/C in LiVPO4F/C Cathode for Lithium-ion Batteries

et al. 2018

Previous studies have shown that the impurity Li3V2(PO4)3 in LiVPO4F will adversely affect its electrochemical performance. In this work, we show that the crystalline composition of LiVPO4F/C is mainly influenced by the environmental temperature. The content of Li3V2(PO4)3 formed in LiVPO4F/C is 0, 11.84 and 18.75% at environmental temperatures of 10, 20, and 30°C, respectively. For the sample LVPF-30C, the SEM pattern shows a kind of alveolate microstructure and the result of selected area electron diffraction shows two sets of patterns. The LiVPO4F/C cathode without impurity phase Li3V2(PO4)3 was prepared at 10°C. The selected area electron diffraction result proves that the lattice pattern of LiVPO4F is a regular parallelogram. Electrochemical tests show that only one flat plateau around 4.2 V appears in the charge/discharge curve, and the reversible capacity is 140.4 mAh·g−1 at 0.1 C, and 116.3 mAh·g−1 at 5 C. From these analyses, it is reasonable to speculate that synthesizing LiVPO4F/C at a low environmental temperature is a practical strategy to obtain pure crystalline phase and good electrochemical performance.