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Abstract Vanadium acetylacetonate, or V(acac) 3 , provides a model chemistry for investigating the performance of nonaqueous disproportionation flow batteries. A flow reactor was developed to implement studies of efficiency, energy capacity, and power capability with respect to electrolyte flow rate and current density. Reactors incorporating a porous separator allowed V(acac) 3 to be cycled without appreciable capacity fade at current densities up to 100 mAcm−2. Experiments at the lowest flow rate, 12.5 mLmin–1, revealed limitations imposed by residence time within the reactor, which manifested as high charging overpotentials. These overpotentials vanish above 25 mLmin–1. A higher flow rate of 50 mLmin–1 yielded performance similar to cells at 25 mLmin–1, but could improve performance at current densities above 100 mAcm−2. Extrapolation of power density's dependence on current suggests a maximum power of 0.22 Wcm−2 for cells run at 206 mAcm−2. Energy efficiency passes through a maximum of 71% at 40 mAcm−2 and the corresponding energy density suggests that the chemistry can, in principle, deliver above 13 WhL−1 in acetonitrile solutions and above 24 WhL−1 in mixed-solvent solutions with higher V(acac) 3 solubility. A V(acac) 3 cell run at 40 mAcm−2 is shown to exhibit stable capacity and performance for more than 150 cycles. Highlights • A new reactor design resolves materials compatibility issues in nonaqueous RFBs. • Effects of flowrate and power on disproportionation electrochemistry are elucidated. • Vanadium acetylacetonate cycles stably, supporting charge/discharge for >150 cycles. • The nonaqueous support does not strictly limit power; cells tolerate 100 mAcm−2. [ABSTRACT FROM AUTHOR]

Silicon (Si)-based materials have attracted significant research as an outstanding candidate for the anode material of lithium-ion batteries. However, the tremendous volume change and poor electron conductivity of bulk silicon result in inferior capacity retention and low Coulombic efficiency. Designing special Si with high energy density and good stability in a bulk electrode remains a significant challenge. In this work, we introduce an ingenious strategy to modify micro silicon by designing a porous structure, constructing nanoparticle blocks, and introducing carbon nanotubes as wedges. A disproportion reaction, coupled with a chemical etching process and a ball-milling reaction, are applied to generate the desired material. The as-prepared micro silicon material features porosity, small primary particles, and effective CNT-wedging, which combine to endow the resultant anode with a high reversible specific capacity of up to 2028.6 mAh g −1 after 100 cycles and excellent rate capability. The superior electrochemical performance is attributed to the unique architecture and optimized composition. [ABSTRACT FROM AUTHOR]

The micro-sized SiO-based composite anode material (d-SiO/G/C) for lithium-ion batteries (LIBs) is achieved via the disproportionation reaction of SiO followed by a pitch pyrolysis reaction. The d-SiO/G/C composite exhibits an initial reversible capacity of 905 mAh g −1 and excellent cycling stability. The initial Coulombic efficiency of the d-SiO/G/C composite can be significantly improved from 68.1% to 98.5% by the prelithiation of the composite anode using stabilized lithium metal powders (SLMP), which counteracts the irreversible capacity loss caused by the solid electrolyte interphase (SEI) formation and irreversible conversion reaction during the first lithiation. The micro-sized d-SiO/G/C composite anode with SLMP prelithiation maintains an excellent cycling stability, suggesting its great potential in practical application for high specific energy lithium ion batteries. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of SiO negative electrodes for lithium ion batteries is thermodynamically and experimentally investigated. The analysis of the reaction pathway and the calculation of the reaction potentials during the Li insertion/extraction reactions are carried out by the construction of the ternary phase diagram for the Li–Si–O system. In the initial reaction of Li insertion, metallic Si and lithium silicates are formed above 0.37 V vs. Li/Li + as a conversion reaction of the SiO negative electrode. Further Li insertion produces Li–Si alloys as reversible reaction phases. The decomposition of the Li 4 SiO 4 phase begins before the formation of the Li–Si alloy is completed. The measured electrode behavior of the SiO negative electrode basically agrees with the thermodynamic calculations, especially at a low reaction rate; deviations can be ascribed to kinetic factors and electrode resistance. The values of over 1898 mA h g −1 and 71.0% were obtained for the discharge capacity and the coulombic efficiency, respectively. Furthermore, the overvoltage for an amorphous SiO electrode was smaller than that for a disproportionated SiO electrode into Si and SiO 2 phases. [ABSTRACT FROM AUTHOR]

We confirmed the existence of LiO 2 by electrochemical quartz crystal microbalance (EQCM) in TEGDME based Li-O 2 batteries. Our results indicated that Li 2 O 2 is generated through stepwise electrochemical reactions rather than disproportionation. We report for the first time that the formed Li 2 O 2 oxidizes to LiO 2 at relative negative potential and O 2 at positive potential respectively. Our conclusions were based on both experimental observations and quantitative analysis. This may enlighten us to reconsider the Li-O 2 batteries mechanisms in a quantitative way. [ABSTRACT FROM AUTHOR]

We introduce a one-step process that consists of thermal disproportionation and impurity doping to enhance the reversible capacity and electrical conductivity of silicon monoxide (SiO)-based negative electrode materials in Li-ion batteries. Transmission electron microscope (TEM) results reveal that thermally treated SiO at 900 °C (H–SiO) consists of uniformly dispersed nano-crystalline Si (nc-Si) in an amorphous silicon oxide (SiO x ) matrix. Compared to that of prinstine SiO, the electrochemical performance of H–SiO shows improved specific capacity, due mainly to the increased reversible capacity by nc-Si and to the reduced volume expansion by thermally disproportionated SiO x matrix. Further electrochemical improvements can be obtained by boron-doping on SiO (HB–SiO) using solution dopant during thermal disproportionation. HB–SiO electrode without carbon coating exhibits significantly enhanced specific capacity superior to that of undoped H–SiO electrode, having 947 mAh g −1 at 0.5C rate and excellent capacity retention of 93.3% over 100 cycles. Electrochemical impedance spectroscopy (EIS) measurement reveals that the internal resistance of the HB–SiO electrode is significantly reduced by boron doping. [ABSTRACT FROM AUTHOR]

Superoxide reacts with carbonate solvents in Li–air batteries. Tris(pentafluorophenyl)borane is found to catalyze a more rapid superoxide (O 2 − ) disproportionation reaction than the reaction between superoxide and propylene carbonate (PC). With this catalysis, the negative impact of the reaction between the electrolyte and O 2 − produced by the O 2 reduction can be minimized. A simple kinetic study using ESR spectroscopy was reported to determine reaction orders and rate constants for the reaction between PC and superoxide, and the disproportionation of superoxide catalyzed by Tris(pentafluorophenyl)borane and Li ions. The reactions are found to be first order and the rate constants are 0.033 s −1 M −1 , 0.020 s −1 M −1 and 0.67 s −1 M −1 for reactions with PC, Li ion and Tris(pentafluorophenyl)borane, respectively. [ABSTRACT FROM AUTHOR]

Abstract: To overcome the disproportionation reaction and Jahn-Teller distortion of Mn3+ in LiMn2O4 cathode materials, we demonstrate a facile route to synthesize hierarchical porous Li4Mn5O12 nano/micro structure, which consists of numerous well-crystallized nanoparticles with diameters of 20–30 nm. The unique structure combines the advantages of both nanostructure and microstructure. When applied as cathode materials for Li-ion batteries, it exhibited a very high specific capacity of 161 mAh g−1 (theoretical value: 163 mAh g−1) with intriguing rate performance and cycling stability. [Copyright &y& Elsevier]

Abstract: An anode material with improved electrochemical performances for Li-ion batteries is prepared using the disproportionation reaction of SiO followed by a high energy mechanical milling process. The modified SiO is composed of embedded Si nano-crystallites in a Si-oxide matrix. Si-oxide matrix could be divided into two parts by reactivity with Li-ion. The inactive Si-suboxide matrix would buffer the volume expansion of embedded Si nano-crystallites and active amorphous SiO2 during the lithiation. This modified SiO electrode shows a large reversible capacity, close to 1000 mAh g−1, and good cyclability, over 50 cycles. [Copyright &y& Elsevier]

Abstract: A life model is developed for a lithium ion cell with a spinel-based cathode. It is assumed in the proposed model that the Mn(III) disproportionation reaction causes the degradation of the spinel cathode. The Mn(III) disproportionation reaction leads to the Mn(II) dissolving into the electrolyte and the formation of an inactive material layer which causes a resistance increase in the cathode. The proposed model is used to investigate the effects of ambient temperature and voltage range of cycling on the loss of the cell capacity and the changes in the volume fraction of the cathode active material, the radius of the cathode particle and the resistance of the cathode. [Copyright &y& Elsevier]