A high-performance lithium ion capacitor (LIC) composed of activated carbon (as the positive electrode) and pre-lithiated C-coated Si/SiOx nanospheres (as the negative electrode) is investigated as a ...potential energy storage system for high-power and high-energy applications. Under optimized pre-lithiation conditions, the feasibility of pre-lithiated C-coated Si/SiOx nanospheres is thoroughly examined as an advanced negative electrode compared with a conventional graphite LIC using pre-lithiated C-coated Si/SiOx nanospheres. The pre-lithiated C-coated Si/SiOx nanospheres show much improved reversible capacity and rate capability with higher capacity retention at a high current density of 10C up to 1000 cycles compared with a conventional LIC. Such improvements may be attributed to the unique physical and chemical properties of C-coated Si/SiOx nanospheres. We believe that this approach provides a practical guideline for developing and successfully implementing advanced LICs.
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•C–Si/SiOx NE was pre-lithiated by contacting the NE with Li metal.•Pre-lithiated C–Si/SiOx NE were successfully adopted to LIC system.•Designed LIC showed superior energy density compared to the LIC with a graphite NE.•The LIC with C–Si/SiOx NE exhibits superior rate performance at a rate of 40C.
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•Graphite anodes were surface-modified with Co2P nanoparticles.•The modified anodes exhibited a remarkable charging time of 16.1 min (80 % SOC).•Stable cycling performance > 300 ...cycles was achieved with the Co2P@graphite anode.•LiP and Li3P reduced interfacial overpotential and increased reversibility.
Natural graphite (NG) is widely utilized as a practical anode in commercial lithium-ion batteries (LIBs) thanks to its high theoretical capacity and low operating voltage as well as high reversibility for Li+ storage. Recently, there has been a strong need to further enhance the fast-charging capability and reduce the charging time of NG for use in expanding electric vehicle applications. To enhance the charging performance of NG, various approaches have been explored to make its surface favorable for fast Li+ intercalation. Herein, we propose a surface modification of NG with functional cobalt phosphide (Co2P). Co2P nanoparticles can be introduced onto NG particles via a thermally induced phase transition process. Various structural and electrochemical investigations have provided insights into the crucial functions and reaction mechanisms of Co2P nanoparticles. We demonstrated that electrochemical conversion reactions of Co2P nanoparticles occurred during the first charging process, and the resulting phases induced effective surface stabilization and high-voltage operation during subsequent cycles. In particular, lithium phosphide (LiP and Li3P) formation is mainly responsible for reducing the overpotential for interfacial reactions between NG and the electrolyte, leading to the effective Li plating suppression and an increase in reversibility during cycles. In practice, the full-cell employing the Co2P@NG anode offered a superior cycling performance over 300 cycles and a charging time of 16.1 min (80 % SOC). We expect our findings make a valuable contribution to the advancement of fast-charging LIBs.
Lithium metal (Li) is an ideal anode for designing high-energy Li metal batteries (LMBs) due to its high specific capacity (3860 mAh g−1) and lowest electrochemical potential. However, the practical ...use of Li is currently impeded by uncontrollable dendritic growth during repeated Li plating and stripping, causing serious safety hazards such as electrical short circuits. To regulate Li growth behavior, various solid electrolyte interfaces (SEIs) have been explored. Despite intensive efforts, further understanding of the dendritic growth mechanism is still required. In this respect, herein, we clarify the origin and growth mechanism of Li dendrites by evaluating the critical role of an artificial SEI using a finite element method. Based on our theoretical study, we suggest that the relatively low ionic conductivity of the SEI layer is responsible for facilitating the growth of Li dendrites and the growth can be effectively suppressed by employing an artificial SEI with a higher ionic conductivity. The high-conductivity artificial SEI regulates local current distributions, directly affecting the growth of Li dendrites as determined by measuring the current density, exchange current density, and geometry. Our findings provide new insight into the design of artificial SEIs for improving the cycling performance of advanced LMBs.
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•Li dendrite growth in Li-metal batteries was probed using a finite element method.•The effects of natural and artificial SEIs on Li growth morphology were studied.•Nonuniform current density at electrolyte-electrode interface caused dendrite growth.•Dendrite growth was suppressed by a high-ionic-conductivity artificial SEI.•The results help secure the stable cycling of Li-metal anodes in Li-metal batteries.
CO + 3H2 → CH4 + H2O.
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•A Ni@SiO2core–shell catalyst was prepared by a sol–gel method.•Nano-sized Ni was stabilized even with a high Ni content.•This was far superior for CO ...methanation than the conventional Ni/SiO2 catalyst.•This was selective for selective CO methanation in CO2.
The specific catalytic activity of a supported metal catalyst increases with an increase in the number of active sites per mass of catalyst, which can be accomplished by increasing the metal content and/or decreasing the particle size of the metal. However, this leads to sintering of metal particles during the reaction, especially in highly exothermic reactions such as CO methanation. In this study, we prepared different SiO2-supported Ni catalysts by wet impregnation and sol–gel methods, and applied them to CO methanation. The prepared catalysts were characterized with N2 physisorption, X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction with H2 (H2-TPR), and transmission electron microscopy (TEM). Some problems associated with the wet impregnation method, such as sintering of Ni and the inability to load the silica with large amounts of Ni, were avoided by using the sol–gel method, in which size-controlled NiO was first synthesized using a polymer stabilizing agent, and then coated with a mesoporous silica shell through a polymerization approach. The prepared 55wt% Ni@SiO2 catalyst exhibited the co-presence of Ni nanoparticles (mean size=8.0±4.4nm) and nanorods (mean length=15.5±13nm, mean width=8.1±4.4nm). This catalyst was far superior for CO methanation than the conventional 33wt% Ni/SiO2 catalyst prepared by wet impregnation, in which the Ni particle size was 24.5nm. The 55wt% Ni@SiO2 catalyst also exhibited excellent catalytic performance for selective CO methanation in the presence of an excessive amount of CO2.
Prussian blue and its analogues that have three-dimensional open frameworks are promising cathode materials for sodium-ion batteries owing to their high theoretical capacity and low production cost. ...Unfortunately, these materials are electrically insulating, which results in adverse effects on their electrochemical performance, such as limited practical capacity and rate capability. In this study, we demonstrate a simple overlaying of a conductive polymer— poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)—on the surface of Prussian blue nanocubes at room temperature, with the aim to secure sufficient electrical conduction pathways and, by extension, improve the electrochemical performance of the nanocubes. The proposed surface-engineered Prussian blue nanocubes with 3.0 wt% poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) show a high reversible capacity (130.9 mA g−1) with stable cycle performance. Moreover, they exhibit a reversible capacity of approximately 112.6 mAh g−1 at the high rate of 1220 mA g−1, which corresponds to 86.0% of the capacity obtained at a current density of 12.2 mA g−1. Such improvements are mainly attributed to the formation of additional networks of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) that facilitate electric conduction in the electrode. Our proposed approach could be a practical solution to improving the electrochemical properties of Prussian blue and its analogues as potential cathode materials for high-performance sodium-ion batteries.
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•PEDOT:PSS overlaid the PB nanocubes prepared by a one-pot mixing process.•Spontaneous formation of 3D conductive networks in electrode by PEDOT:PSS layer.•Improved rate capability of PED-PB electrode by additional pathways of electrons.
Abstract Thick and dense graphite anodes used in lithium‐ion batteries (LIBs) suffer from sluggish reaction kinetics at the electrode level, causing Li metal plating on their surfaces and significant ...capacity decay at high charging currents. Thus, it is crucial to tailor electrodes based on a comprehensive understanding of the complex reaction kinetics to realize fast‐charging LIBs. A multi‐interface strategy is proposed for electrode tailoring using Al 2 O 3 nanoparticles to enhance fast‐charging capability while suppressing Li metal plating. Molecular dynamics simulations suggest that the incorporated Al 2 O 3 nanoparticles perturb the charge and molecule distributions in the boundary layer, forming an “interfacial highway” for facile Li + transport at the Al 2 O 3 /electrolyte interface. This pushes Li + deeper into the electrode and homogenizes the Li + flux across the electrode's top surface. A full cell assembled with the Al 2 O 3 ‐decorated graphite electrode (areal capacity of 4.4 mAh cm −2 ) exhibits excellent cyclability with a capacity retention of 83.4% over 500 cycles even at a 2C rate without any noticeable signal for undesirable Li plating. The role of interfacial highways predicted by theoretical computations is further validated using a pouch‐type full cell (500 mAh). These findings provide insights into the interfacial and microstructural design of high‐capacity graphite electrodes for fast‐charging, long‐cycling LIBs.
This article proposes an offline compensation method for current scaling gains in the AC motor drive systems with three-phase current sensors. Many articles have been presented about the current ...scaling gain compensations of inverters. Most of them can be adopted during rotations. Those were studied for two-phase current sensing. Applications, such as elevators and hoist cranes, generally measure three-phase currents directly using three current sensors in preparation for a fault in any one of them. In this article, we present a compensation method for a three-phase current sensing system. This article analyzes the effect of current scaling gain errors on the neutral current that is calculated with measured stator currents. Based on the analysis, a compensation strategy for the current scaling gains is presented. The proposed method is applicable only at a standstill. It can be used for initial commissioning since it works at a standstill regardless of whether the rotor is locked or not. The experiments that demonstrate the validity of the proposed method were carried out in an elevator system as well as a laboratory. The proposed method is simple to be implemented and it requires no additional hardware.
Irreversible formation of ZnO from Zincate ion is effectively suppressed by addition of alcohols, where some hydroxides are replaced with alkoxide ions.
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•Alcoholic additives can ...improve the cycle performance of Zn-air cells.•Irreversible formation of ZnO can be suppressed by forming alkoxide-modified zincates.•Monoalcohol is more effective than polyols for improving the cycle performance.
The irreversible formation of zinc oxide (ZnO) in Zn–air batteries is not avoidable. Because of the formation of ZnO, the battery capacity, potential, and coulombic efficiency decrease. The low electrochemical reactivity of ZnO is the main obstacle that interferes with building an electrochemically rechargeable Zn–air battery. In this work, electrolytic additives that suppress the formation of ZnO are studied. The zincate ion (Zn(OH)42−) is an intermediate ion, which transforms into ZnO in basic solutions during the discharge process. Some hydroxide ions in zincate can be replaced with alkoxide and acetate ions; this resulted in a clear improvement of the reversibility of Zn–air batteries. The modification of zincate with alkoxide/acetate suppresses its transformation into ZnO, which results in improved retention of capacity in cycle tests.
A new lithium‐doping method using a stable lithium metal oxide, Li2MoO3 as an alternative lithium source is proposed. By incorporating Li2MoO3 into cathodes, the necessary lithium‐doping process of ...lithium ion capacitors can be simplified and made more effective. At the same lithium‐doping level, better capacity and rate capability are obtained than for the conventional method using metallic lithium.
Lithium metal batteries have recently gained tremendous attention owing to their high energy capacity compared to other rechargeable batteries. Nevertheless, lithium (Li) dendritic growth causes low ...Coulombic efficiency, thermal runaway, and safety issues, all of which hinder the practical application of Li metal as an anodic material. In this review, the failure mechanisms of Li metal anode are described according to its infinite volume changes, unstable solid electrolyte interphase, and Li dendritic growth. The fundamental models that describe the Li deposition and dendritic growth, such as the thermodynamic, electrodeposition kinetics, and internal stress models are summarized. From these considerations, porous carbon-based frameworks have emerged as a promising strategy to resolve these issues. Thus, the main principles of utilizing these materials as a Li metal host are discussed. Finally, we also focus on the recent progress on utilizing one-, two-, and three-dimensional carbon-based frameworks and their composites to highlight the future outlook of these materials.
