Demand for energy in day to day life is increasing exponentially. However, existing energy storage technologies like lithium ion batteries cannot stand alone to fulfill future needs. In this regard, ...potassium ion batteries (KIBs) that utilize K ions in their charge storage mechanism have attracted considerable attention due to their unique properties and are therefore established as one of the future battery systems of interest among the scientific community. Nevertheless, the development and identification of appropriate electrode materials is very essential for practical applications. This review features the current development in KIBs electrode and electrolyte materials, the present challenges facing this technology (in the commercial aspect), and future aspects to develop fully functional KIBs. The potassium storage mechanisms, evolution of the KIBs, and the advantages and disadvantages of each category of materials are included. Additionally, various approaches to enhance the electrochemical performances of KIBs are also discussed. This review is not only an amalgamation of different viewpoints in literature, but also contains concise perspectives and strategies. Moreover, the potential emergence of a novel class of K‐based dual ion batteries is also analyzed for the first time.
The development and identification of appropriate electrode and electrolyte materials is very essential for practical potassium ion storage applications. Hence, an understanding of the current development in potassium‐based electrode and electrolyte materials and the present performance challenges is critical.
Abstract
Iron phthalocyanine (FePc) is a promising non-precious catalyst for the oxygen reduction reaction (ORR). Unfortunately, FePc with plane-symmetric FeN
4
site usually exhibits an ...unsatisfactory ORR activity due to its poor O
2
adsorption and activation. Here, we report an axial Fe–O coordination induced electronic localization strategy to improve its O
2
adsorption, activation and thus the ORR performance. Theoretical calculations indicate that the Fe–O coordination evokes the electronic localization among the axial direction of O–FeN
4
sites to enhance O
2
adsorption and activation. To realize this speculation, FePc is coordinated with an oxidized carbon. Synchrotron X-ray absorption and Mössbauer spectra validate Fe–O coordination between FePc and carbon. The obtained catalyst exhibits fast kinetics for O
2
adsorption and activation with an ultralow Tafel slope of 27.5 mV dec
−1
and a remarkable half-wave potential of 0.90 V. This work offers a new strategy to regulate catalytic sites for better performance.
The reasonable design of electrode materials for rechargeable batteries plays an important role in promoting the development of renewable energy technology. With the in‐depth understanding of the ...mechanisms underlying electrode reactions and the rapid development of advanced technology, the performance of batteries has significantly been optimized through the introduction of defect engineering on electrode materials. A large number of coordination unsaturated sites can be exposed by defect construction in electrode materials, which play a crucial role in electrochemical reactions. Herein, recent advances regarding defect engineering in electrode materials for rechargeable batteries are systematically summarized, with a special focus on the application of metal‐ion batteries, lithium–sulfur batteries, and metal–air batteries. The defects can not only effectively promote ion diffusion and charge transfer but also provide more storage/adsorption/active sites for guest ions and intermediate species, thus improving the performance of batteries. Moreover, the existing challenges and future development prospects are forecast, and the electrode materials are further optimized through defect engineering to promote the development of the battery industry.
Recent advances regarding defect engineering on electrode materials for rechargeable batteries are systematically summarized, with a special focus on application in metal‐ion batteries, lithium–sulfur batteries, and metal–air batteries. The defects can not only promote diffusion of ions and charge transfer, but also maintain structural stability and provide more energy storage/adsorption/active sites, thus improving the performance of the batteries.
A modified electrode for vanadium redox flow battery (VRFB) has been developed in this paper. The electrode is based on a traditional carbon felt (CF) grafted with the short-carboxylic multi-walled ...carbon nanotubes (MWCNTs). The microstructure and electrochemical property of the modified electrode as well as the performance of the VRFB single cell with it have been characterized. The results show that the MWCNTs are evenly dispersed and adhere to the surface of carbon fibres in the CF. The electrochemical activities of the modified CF electrode have been improved dramatically and the reversibility of the VO2+/VO2+ and V3+/V2+ redox couples increased greatly. The VRFB single cell with the modified CF exhibits higher coulombic efficiency (93.9%) and energy efficiency (82.0%) than that with the pristine CF. The SEM analysis shows that the MWCNTs still cohere with carbon fibres after charge and discharge test, indicating the stability of the MWCNTs in flowing electrolyte. Therefore, the composite electrode presents considerable potential for the commercial application of CF in VRFB.
▸ A carbon felt (CF) supported carbon nanotubes (CNTs) catalysts composite electrode has been developed. ▸ The composite electrode improve the reversibility of the VO2+/VO2+ and V3+/V2+ redox couples greatly. ▸ The CNTs can be stabilized on the CF evenly and strongly by Nafion which is stable in vanadium solution. ▸ The VRFB single cell with the modified CF with MWCNTs content of 0.94 wt.% exhibits excellent performance.
The vanadium redox flow battery (VRFB) is one of the promising large-scale energy storage technologies. The electrode is one of the key components of the VRFB, and its design has an important effect ...on its electrochemical redox kinetics and battery performance. The ideal VRFB electrode material has high catalytic activity, good conductivity, and high stability. Carbon-based electrodes are the most commonly used electrode materials for VRFBs. However, its reaction kinetics and catalytic active sites are low. This paper summarizes the methods of carbon-based electrode modification of the electrochemical performance in VRFBs. Three representative methods including metal/metal oxide modification, nonmetal atom modification, and defect engineering for graphite felt in VRFBs are generally reviewed. First, metal and metal oxides have high catalytic activity, which can enhance the chemical reaction process of vanadium ions and greatly improve the reversibility of the redox reaction of vanadium ions. Then, nonmetal atom modification can generally improve the hydrophilicity of carbon-based electrodes, enhance the adsorption/desorption capacity of vanadium ions, and improve the reaction kinetics. Moreover, defect engineering can lead to the formation of the micropore structure on the surface and increase the specific surface area of the material, thus generating more redox reaction active sites. Finally, the development direction of electrode modification in VRFBs is prospected, and it is expected that this review will provide useful insights into the development of VRFBs.
A novel composite membrane blended the sulfonated poly (ether ether ketone) (SPEEK) with modified carbonaceous mudstone (SPEEK/MCM) has been developed for vanadium redox flow battery (VRB). Using a ...strong acidification treatment, a large amount of hydrophilic oxygen functional groups was introduced on the modified carbonaceous mudstone (MCM) particles, which has been evidenced to enhance the proton conductivity. It is found that the MCM particles help to retard the permeation of vanadium ions through the membrane. With these merits, the VRB single cell based on our novel SPEEK/MCM membrane exhibits outstanding device performance. Notably, the coulombic efficiency (CE) of the cell is as high as more than 99% and the per-cycle capacity loss is only 0.15% under a high current density of 120 mA cm−2. Our work provides a simple method to prepare low cost and high-performance membranes for VRB. More importantly, the SPEEK/MCM membrane has promising potential in other battery applications.
•A composited SPEEK/ carbonaceous mudstone (SPEEK/MCM) membrane is fabricated for vanadium redox flow battery.•The SPEEK/MCM membrane shows much lower vanadium ion permeability compared to Nafion 212 membrane.•A vanadium redox flow battery assembled with a SPEEK/MCM membrane shows excellent cell performance.
Manipulating a quantum state via electrostatic gating has been of great importance for many model systems in nanoelectronics. Until now, however, controlling the electron spins or, more specifically, ...the magnetism of a system by electric-field tuning has proven challenging
. Recently, atomically thin magnetic semiconductors have attracted significant attention due to their emerging new physical phenomena
. However, many issues are yet to be resolved to convincingly demonstrate gate-controllable magnetism in these two-dimensional materials. Here, we show that, via electrostatic gating, a strong field effect can be observed in devices based on few-layered ferromagnetic semiconducting Cr
Ge
Te
. At different gate doping, micro-area Kerr measurements in the studied devices demonstrate bipolar tunable magnetization loops below the Curie temperature, which is tentatively attributed to the moment rebalance in the spin-polarized band structure. Our findings of electric-field-controlled magnetism in van der Waals magnets show possibilities for potential applications in new-generation magnetic memory storage, sensors and spintronics.
Graphene deposited on the surface of a carbon felt (CF) using a solution coating method has been developed as a high-performance positive electrode for an all vanadium redox flow battery (VRB). A key ...to obtain excellent electrochemical activity towards the VO2+/VO2+ redox couple is to wrap the CF using the graphene with high specific surface area and superb conductivity. It is found that the dipping times of CF into the graphene/Nafion solution significantly affect its electrochemical activity. The cyclic voltammetry (CV) results indicate that with 5 dipping times, the graphene coated CF (G/CF) exhibits the highest peak current and lowest peak potential difference towards the VO2+/VO2+ redox couple. More importantly, the VRB assembled with our novel G/CF cathodic electrode shows a decreased polarization during charge/discharge process compared with the control VRB with the pristine CF. Consequently, both the voltage efficiency and energy efficiency of the VRB with G/CF electrode have increased compared to the one with pristine CF. Our work provides a simple solution coating process to fabricate graphene modified CF electrode for VRB with high performance and this simple method is believed to be promising in other electrocatalysts applications.
•A graphene coated carbon felt electrode (G/CF) for has been fabricated.•The graphene is homogenous dispersed on the surface of fiber of carbon felt.•The G/CF electrode displays high activity towards the VO2+/VO2+ redox couple.•The G/CF electrode shows much better cell performance compared to pristine carbon felt electrode.
A novel sandwich-type sulfonated poly(ether ether ketone) (SPEEK)/tungstophosphoric acid (TPA)/polypropylene (PP) composite membrane for a vanadium redox flow battery (VRB) has been developed with ...improved properties: the permeability of vanadium ions is greatly reduced and the performance of the VRB cell is greatly increased. The membrane is based on a traditional SPEEK membrane embedded with TPA but PP is used to enhance the membrane for the first time. Although its voltage efficiency (VE) is a little lower than that of a Nafion 212 membrane, it is expected to have good prospects for VRB systems because of its low cost and good performance.
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