A rechargeable aqueous manganese-ion battery based on intercalation chemistry

Aqueous rechargeable metal batteries are intrinsically safe due to the utilization of low-cost and non-flammable water-based electrolyte solutions. However, the discharge voltages of these electrochemical energy storage systems are often limited, thus, resulting in unsatisfactory energy density. Therefore, it is of paramount importance to investigate alternative aqueous metal battery systems to improve the discharge voltage. Herein, we report reversible manganese-ion intercalation chemistry in an aqueous electrolyte solution, where inorganic and organic compounds act as positive electrode active materials for Mn2+ storage when coupled with a Mn/carbon composite negative electrode. In one case, the layered Mn0.18V2O5·nH2O inorganic cathode demonstrates fast and reversible Mn2+ insertion/extraction due to the large lattice spacing, thus, enabling adequate power performances and stable cycling behavior. In the other case, the tetrachloro-1,4-benzoquinone organic cathode molecules undergo enolization during charge/discharge processes, thus, contributing to achieving a stable cell discharge plateau at about 1.37 V. Interestingly, the low redox potential of the Mn/Mn2+ redox couple vs. standard hydrogen electrode (i.e., −1.19 V) enables the production of aqueous manganese metal cells with operational voltages higher than their zinc metal counterparts.

Electrochemical Properties of a Lithium-Impregnated Metal Foam Anode (LIMFA Fecral) for Molten Salt Thermal Batteries

Although numerous cathode materials with excellent properties have been developed for use in molten salt thermal batteries, similar progress is yet to be made with anode materials. Herein, a high-performance lithium-impregnated metal foam anode (LIMFA) is fabricated by impregnating molten lithium into a gold-coated iron–chrome–aluminum (FeCrAl) foam at 400°C. A test cell employing the LIMFA FeCrAl anode exhibited a specific capacity of 2,627 As·g−1. For comparison, a cell with a conventional Li(Si) anode was also discharged, demonstrating a specific capacity of 982 As·g−1. This significant improvement in performance can be attributed to the large amount (18 wt.%) of lithium incorporated into the FeCrAl foam and the ability of the FeCrAl foam to absorb and immobilize molten lithium without adopting a cup system. For thermal batteries without a cup, the LIMFA FeCrAl provides the highest-reported specific capacity and a flat discharge voltage curve of molten lithium. After cell discharge, the FeCrAl foam exhibited no lithium leakage, surface damage, or structural collapse. Given these advantageous properties, in addition to its high specific capacity, LIMFA FeCrAl is expected to aid the development of thermal batteries with enhanced performance.

Thermal Energy Production in an Electrochemical Cell and Heat Transfer to Its Dark Surroundings

The theoretical formulation presented in this abridged paper was developed to predict the transient cell average temperature of a lithium-based cell during its discharge in dark, extremely low material density surroundings where the predominant mechanism of heat exchange between its shroud surface and surroundings is the thermal radiation process for a given cell discharge current and its initial temperature. The average computed temperature of an ideal lithium-based button cell, such as Li(s)/electrolyte/CF(s), is presented as a function of time in the form of plots at two discharge currents as an example of the application of the derived formulation. The presented data are briefly discussed in light of the lithium-based cell component stability and its safe discharge operation.

Thermal Energy Production and Heat Exchange between an Electrochemical Cell and Its Surroundings

The theoretical formulation presented in this paper was developed to predict the cell average temperature as a function of time for a given cell discharge current and its initial temperature under adiabatic and nonadiabatic conditions. The cell average temperature versus time data calculated from the derived formulation is presented in the form of plots for an ideal lithium-based button cell (for example, lithium(s)/electrolyte/carbon monofluoride(s)) during its discharge period. The presented data are briefly discussed in light of cell component stability and safe discharge operation.

Investigation of Mg2+ ion on Structural, Morphological, FTIR, Dielectric and AC Conductivity of PVDF-HFP Based Solid Polymer Electrolytes and Application to Electrochemical Cell

In this paper, solid polymer electrolytes comprising of Poly (vinylidene-fluoride-hexafluoropropylene) (PVDF-HFP) polymer and Mg (ClO4)2 salt were prepared by employing the solution casting technique. The fabricated polymer-salt electrolyte membranes are exposed to XRD, FTIR and SEM studies. The real and imaginary part of dielectric permittivity is illustrated with the Cole-Cole plot. Static dielectric constant \({(\epsilon }_{s})\), dynamic dielectric constant \(\left({\epsilon }_{\infty }\right)\), dielectric strength \(({\Delta }\epsilon\)), dielectric loss (tanδ) and relaxation time (τ) are determined using the Cole-Cole plot. The electrochemical properties; cell stability, cell discharge characteristics, dc and ac conductivity are analyzed. Structural studies of XRD peaks are broadened to confirm the amorphous phase of polymer matrix. Morphological studies shows the presence of interlinked micro-pores promote for ease of mobility of Mg2+ ions which attribute to enhance ionic conductivity. The static dielectric constant \({(\epsilon }_{s})\), dynamic dielectric constant \(\left({\epsilon }_{\infty }\right)\), dielectric strength \(({\Delta }\epsilon\)), dielectric loss (tanδ) reach maximum but relaxation time (τ) decreases for an optimal concentration ratio of (100:40) PVDF-HFP: Mg (ClO4)2 that reveals fast hopping of ions from one site of the polymer chain to another. The highest ionic conductivity of 7.73333x 10− 4 Scm− 1 is obtained at room temperature for [PVDF-HFP: Mg(ClO4)2] polymer-salt electrolyte. The cell discharge characteristics of OCV and SCC of Mg/ [PVDF-HFP: Mg(ClO4)2] /I + C cell are found to be 1.8 V and 120 mA respectively The electrochemical stability was observed with a constant voltage of 0.43volt in a positive cycle and 0.4 volts of negative potential which favors an electrochemical membrane for battery applications

Understanding rapid charge and discharge in nano-structured lithium iron phosphate cathodes

A Doyle–Fuller–Newman (DFN) model for the charge and discharge of nano-structured lithium iron phosphate (LFP) cathodes is formulated on the basis that lithium transport within the nanoscale LFP electrode particles is much faster than cell discharge, and is therefore not rate limiting. We present some numerical solutions to the model and show that for relevant parameter values, and a variety of C-rates, it is possible for sharp discharge fronts to form and intrude into the electrode from its outer edge(s). These discharge fronts separate regions of fully utilised LFP electrode particles from those that are not. Motivated by this observation an asymptotic solution to the model is sought. The results of the asymptotic analysis of the DFN model lead to a reduced order model, which we term the reaction front model (or RFM). Favourable agreement is shown between solutions to the RFM and the full DFN model in appropriate parameter regimes. The RFM is significantly cheaper to solve than the DFN model, and therefore has the potential to be used in scenarios where computational costs are prohibitive, e.g. in optimisation and parameter estimation problems or in engineering control systems.

Stellate cell computational modeling predicts signal filtering in the molecular layer circuit of cerebellum

The functional properties of cerebellar stellate cells and the way they regulate molecular layer activity are still unclear. We have measured stellate cells electroresponsiveness and their activation by parallel fiber bursts. Stellate cells showed intrinsic pacemaking, along with characteristic responses to depolarization and hyperpolarization, and showed a marked short-term facilitation during repetitive parallel fiber transmission. Spikes were emitted after a lag and only at high frequency, making stellate cells to operate as delay-high-pass filters. A detailed computational model summarizing these physiological properties allowed to explore different functional configurations of the parallel fiber—stellate cell—Purkinje cell circuit. Simulations showed that, following parallel fiber stimulation, Purkinje cells almost linearly increased their response with input frequency, but such an increase was inhibited by stellate cells, which leveled the Purkinje cell gain curve to its 4 Hz value. When reciprocal inhibitory connections between stellate cells were activated, the control of stellate cells over Purkinje cell discharge was maintained only at very high frequencies. These simulations thus predict a new role for stellate cells, which could endow the molecular layer with low-pass and band-pass filtering properties regulating Purkinje cell gain and, along with this, also burst delay and the burst-pause responses pattern.

Stellate cell computational modelling predicts signal filtering in the molecular layer circuit of cerebellum

The functional properties of cerebellar stellate cells and the way they regulate molecular layer activity are still unclear. We have measured stellate cells electroresponsiveness and their activation by parallel fiber bursts. Stellate cells showed intrinsic pacemaking, along with characteristic responses to depolarization and hyperpolarization, and showed a marked short-term facilitation during repetitive parallel fiber transmission. Spikes were emitted after a lag and only at high frequency, making stellate cells to operate as delay-high-pass filters. A detailed computational model summarizing these physiological properties allowed to explore different functional configurations of the parallel fiber – stellate cell – Purkinje cell circuit. Simulations showed that, following parallel fiber stimulation, Purkinje cells almost linearly increased their response with input frequency but such an increase was inhibited by stellate cells, which leveled the Purkinje cell gain curve to its 4 Hz value. When reciprocal inhibitory connections between stellate cells were activated, the control of stellate cells over Purkinje cell discharge was maintained only at very high frequencies. These simulations thus predict a new role for stellate cells, which could endow the molecular layer with low-pass and band-pass filtering properties regulating Purkinje cell gain and, along with this, also burst delay and the burst-pause responses pattern.

Dentate spikes and external control of hippocampal function

Mouse hippocampus CA1 place-cell discharge typically encodes current location but during slow gamma dominance (SGdom), when slow gamma oscillations (30-60 Hz) dominate mid-frequency gamma oscillations (60-90 Hz) in CA1 local field potentials, CA1 discharge switches to represent distant recollected locations. We now report that dentate spike type 2 (DSM) events initiated by MECII→DG inputs promote SGdom and change CA1 discharge, whereas type 1 (DSL) events initiated by LECII→DG inputs do not. Just before SGdom, LECII-originating slow gamma oscillations in dentate gyrus and CA3-originating slow gamma oscillations in CA1 become optimally phase and frequency synchronized at the DSM peak when the firing rates of DG, CA3, and CA1 principal cells increase to promote DG→CA3→CA1 cofiring optimized for the 5-10 ms DG-to-CA1 neuro-transmission that coincides with SGdom. Several properties and consequences of DSM demonstrate extrahippocampal control of SGdom, identifying a cortico-hippocampal mechanism that switches between memory-related hippocampal information processing modes.