Confining Li_2O_2 in tortuous pores of mesoporous cathodes to facilitate low charge overpotentials for Li-O_2 batteries

Achieving low charge overpotentials represents one of the most critical challenges for pursuing highperformance lithium-oxygen(Li-O₂)batteries.Herein,we propose a strategy to realize low charge overpotentials by confining the growth of lithium peroxide(Li₂O₂)inside mesoporous channels of cathodes(CMK-8).The CMK-8 cathode with tortuous pore structures can extend the diffusion distance of lithium superoxide(LiO₂)in the mesoporous channels,facilitating the further reduction of LiO₂ to lithium peroxide(Li₂O₂)inside the pores and preventing them to be diffused out of the pores.Therefore,Li₂O₂ is trapped in the mesoporous channels of CMK-8 cathodes,ensuring a good Li₂O₂/CMK-8 contact interface.The CMK-8 electrode exhibits a low charge overpotential of 0.43 V and a good cycle life for 72 cycles with a fixed capacity of 500 m Ah g^-1 at 0.1 A g^-1.This study proposes a strategy to achieve a low charge overpotential by confining Li₂O₂ growth in the mesoporous channels of cathodes.     

CeO_2@NiCo_2O_4 nanowire arrays on carbon textiles as high performance cathode for Li-O_2 batteries

The successful development of Li-O_2 battery technology depends on developing a stable and efficient cathode. As an important step toward this goal, for the first time, we report the development of CeO_2 nanoparticles modified NiCo_2O_4 nanowire arrays(NWAs) grown on the carbon textiles as a new carbon-free and binder-free cathode system. In this study, the Li-O_2 battery with the CeO_2@NiCo_2O_4 NWAs has exhibited much reduced overpotentials, a high discharge capacity, an improved cycling stability,outperforming the Li-O_2 battery with NiCo_2O_4 NWAs. These improvements can be attributed to both the tailored morphology of discharge product and improved oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) activity after CeO_2 NPs deposition. To a considerable extent, this idea of cathode construction including structure design and composition optimization can provide guidance for further researches in developing more powerful cathode for Li-O_2 battery.     

MOF-template derived hollow CeO_2/Co_3O_4 polyhedrons with efficient cathode catalytic capability in Li-O_2 batteries

Li-O_2 batteries(LOBs) have been perceived as the most potential clean energy system for fast-growing electric vehicles by reason of their environmentally friendlier,high energy density and high reversibility.However,there are still some issues limiting the practical application of LOBs,such as the large gap between the actual capacity level and the theoretical capacity,low rate performance as well as short cycle life.Herein,hollow CeO_2/Co_3 O_4 polyhedrons have been synthesized by MOF template with a simple method.And it is was further served as a cathode catalyst in Li-O_2 batteries.By means of the synergistic effect of two different transition metal oxides,nano-sized hollow porous CeO_2/Co_3 O_4 cathode obtained better capacity and cycle performance.As a result,excellent cyclability of exceeding 140 and 90 cycles are achieved at a fixed capacity of 600 and 1000 mAh/g,respectively.The successful application of this catalyst in LOBs offers a novel route in the aspect of the synthesis of other hollow porous composite oxides as catalysts for cathodes in LOBs systems by the MOF template method.     

In-situ deposition of Pd/Pd_4S heterostructure on hollow carbon spheres as efficient electrocatalysts for rechargeable Li-O_2 batteries

The sluggish kinetics of oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) have always restricted the development of lithium oxygen batteries(LOBs).Herein,hollow carbon spheres loaded with Pd/Pd_4S heterostructure(Pd/Pd_4S@HCS) were successfully prepared via the in-situ deposition to improve the electrocatalytic activities for both ORR and OER in LOBs.With the welldispersed Pd/Pd_4S nanoparticles,the hierarchical composite with large specific surface area offers favorable transport channels for ions,electron and oxygen.Especially,the Pd/Pd_4S nanoparticles could exhibit excellent electrochemical performance for ORR and OER due to their intrinsic catalytic property and interfacial effect from the heterostructure.Therefore,the LOBs with Pd/Pd_4S@HCS as cathode catalyst show improved specific capacities,good rate ability and stable cycling performance.     

Overview of multi-stage charging strategies for Li-ion batteries

To reduce the carbon footprint in the transportation sector and improve overall vehicle efficiency,a large number of electric vehicles are being manufactured.This is due to the fact that environmental concerns and the depletion of fossil fuels have become significant global problems.Lithium-ion batteries(LIBs)have been distinguished themselves from alternative energy storage technologies for electric vehicles(EVs) due to superior qualities like high energy and power density,extended cycle life,a...     

Effects of long-term fast charging on a layered cathode for lithium-ion batteries

Fast charging, which aims to shorten recharge times to 10–15 min, is crucial for electric vehicles(EVs),but battery capacity usually decays rapidly if batteries are charged under such severe conditions.Revealing the failure mechanism is a prerequisite to improving the charging performance of lithium(Li)-ion batteries. Previous studies have focused less on cathode materials while also mostly focusing on their early changes. Thus, the cumulative effect of long-term fast charging on cathode materia...     

Operando magnetometry on Li x CoO2 during charging/discharging

Journal of Solid State Electrochemistry - Operando measurements of the magnetic susceptibility χ during electrochemical charging of commercially used battery electrode materials are...     

The heat generation rate of nickel-metal hydride battery during charging/discharging

The heat generation rate of nickel-metal hydride battery is investigated during charging/discharging in this study. The heat capacity of 8 Ah cylindrical Ni-MH battery is measured using a large-scale calorimeter. An accelerating rate calorimeter is employed to provide an adiabatic environment for the battery. The generation rates of reaction heat, polarization heat, and combination heat are calculated through curve fitting. Results show that there exits a linear relationship between each generation rate of the three heat items and the charging/discharging currents. It is suggested that the ohm internal resistance of the battery needs to be as low as possible for reducing the ohm heat. In addition, it is better to avoid overcharging in the higher rate of 5 C for battery safety.     

The energy storage mechanisms of MnO2 in batteries

Manganese dioxide, MnO₂, is one of the most promising electrode reactants in metal-ion batteries because of the high specific capacity and comparable voltage. The storage ability for various metal ions is thought to be modulated by the crystal structures of MnO₂ and solvent metal ions. Hence, through combing the relationship of the performance (capacity and voltage) with the polymorphs of the MnO₂ and metal ions in different solvents (organic and aqueous), three main energy storage mechanisms were found to be responsible for the different electrochemical processes. Furthermore, this review summarizes the main challenge and gives a direction for profound study in the future.     

The unpredictability of electrostatic charging

Capricious charges: the electrostatic charging that occurs when two surfaces come into contact is familiar to everyone, and has been known for millennia. Nonetheless, the scientific understanding of the phenomenon is poor, and it is not possible to reliably predict which surface will charge positively and which will charge negatively. Recent work shows why electrostatic charging may never be predictable.     

Investigation of multi-step fast charging protocol and aging mechanism for commercial NMC/graphite lithium-ion batteries

Fast charging is considered a promising protocol for raising the charging efficiency of electric vehicles.However, high currents applied to Lithium-ion(Li-ion) batteries inevitably accelerate the degradation and shorten their lifetime. This work designs a multi-step fast-charging method to extend the lifetime of LiNi_0.5Co_0.2Mn_0.3O₂(NMC)/graphite Li-ion batteries based on the studies of half cells and investigates the aging mechanisms for different char...     

Hydrothermal synthesis of TiO2(B) nanowires with ultrahigh surface area and their fast charging and discharging properties in Li-ion batteries

We first report a facile hydrothermal route for preparing TiO(2)(B) nanowires with ultrahigh surface area, up to 210 m(2) g(-1). Due to the 1D structure, high BET surface area and shorter b-and c-axis channel across the nanowires, the obtained TiO(2)(B) nanowire was shown to be a good anode material for lithium-ion batteries, especially on the fast charging and discharging performance.     

Metal-metal and carbon-carbon bonds as potential components of molecular batteries

The reductive coupling of [M(salophen)] derivatives, where M is an early transition metal and salophen is N,N'-o-phenylenebis(salicylideneaminato) dianion, led to the formation of dimers linked through C-C and M-M bonds. Both of these bonds can potentially function as electron reservoirs: each bond can be used as a reversible source of a pair of electrons under the condition that it is not chemically transformed by the incoming substrate which functions as an electron acceptor. To explore this potential function as well as the competition in the redox processes between C-C and M-M bonds within the same molecular framework, we investigated the reduction of [(tBu4-salophen)NbCl3] (1) and [(tBu4-salophen)MoCl2] (7) as model compounds. In the former case, the reduction led to [(Nb-Nb)(tBu4-*salophen2*)] (2) which contains both a Nb-Nb bond (2.6528(7) A) and two C-C bonds across two imino groups of the ligand. Complex 2 can be reduced further to a transient compound 5 that contains an Nb=Nb bond. In the second case, the reduction of 7 by two electrons led to [(Mo[triplebond]Mo)(tBu4-salophen)2] (8), which does not contain any C-C linkages between the two salophen units. Complexes 2 and 5 are able to transfer one pair and two pairs of electrons, respectively, to give compounds 3, 4, and 6, with the consequent cleavage of the Nb-Nb and Nb=Nb bonds. In the present case, it is surprising that the C-C bonds do not participate in the reduction of the substrates. A careful theoretical treatment anticipates, both in the case of 1 and 7, the preferential formation of metal-metal bonds upon reduction. This is indeed the case for 7, but not for 1, where the formation of C-C bonds competes with that of M-M bonds, the latter being the first ones, however, to be involved in electron-transfer reactions. The theoretical approach allowed us to investigate the possibility of intramolecular electron transfer from C-C bonds to M-M bonds and vice versa.     

Biological potential of thiazolidinedione derivatives of synthetic origin

Thiazolidinediones are sulfur containing pentacyclic compounds that are widely found throughout nature in various forms. Thiazolidinedione nucleus is present in numerous biological compounds, e.g., anti-malarial, antimicrobial, anti-mycobacterium, anticonvulsant, antiviral, anticancer, anti-inflammatory, antioxidant, anti-HIV (human immunodeficiency virus) and antitubercular agent. However, owing to the swift development of new molecules containing this nucleus, many research reports have been generated in a brief span of time. Therefore seems to be a requirement to collect recent information in order to understand the current status of the thiazolidinedione nucleus in medicinal chemistry research, focusing in particular on the numerous attempts to synthesize and investigate new structural prototypes with more effective antidiabetic, antimicrobial, antioxidant, anti-inflammatory, anticancer and antitubercular activity.

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V2O5/rGO arrays as potential anode materials for high performance sodium ion batteries

Journal of Solid State Electrochemistry - Herein, we successfully deposit V2O5 nanobelt arrays on Ni foam uniformly coated with reduced graphene oxides (rGO), to manufacture V2O5/rGO arrays...     

The rise of lignin biorefinery

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The impedance of lithium-ion batteries

Cylindrical and flat one-layer lithium-ion batteries, as well as symmetrical cells with like electrodes, are studied using electrochemical impedance spectroscopy. Equivalent circuit is suggested, its parameters found, and the activation energies estimated for different stages of the electrode process.     

Molecular wiring of insulators: charging and discharging electrode materials for high-energy lithium-ion batteries by molecular charge transport layers

Self-assembled monolayers (SAMs) of redox-active molecules on mesoscopic substrates exhibit two-dimensional conductivity if their surface coverage exceeds the percolation threshold. Here, we show for the first time that such molecular charge transport layers can be employed to electrochemically address insulating battery materials. The widely used olivine-structured LiFePO4 was derivatized with a monolayer of 4-[bis(4-methoxyphenyl)amino]benzylphosphonic acid (BMABP) in this study. Fast cross-surface hole percolation was coupled to interfacial charge injection, affording charging and discharging of the cathode material. These findings offer the prospect to greatly reduce the amount of conductive carbon additives necessary to electrochemically address present metal phosphate cathode materials, opening up the possibility for a much improved energy storage density. When compared at equal loading, the rate capability is also enhanced with respect to conventional carbon-based conductive additives.