Lithium electrode surface morphologies during cycling were measured in LiAsF6‐normalethylene carbonate false(ECfalse)/2‐normalmethyltetrahydrofuran false(2normalMeTHFfalse) and LiAsF6‐2normalMeTHF electrolytes. Particulate and needle‐like Li were observed on the Li electrode after cycling. Although the particulate Li could be stripped during discharge, much of the needle‐like Li remained. It appears that the needle‐like Li tends to become “dead‐Li” and is responsible for the loss of cycling of lithium electrodes.

Enhanced external counterpulsation therapy improved myocardial perfusion at rest and with dipyridamole and was associated with an increased exercise tolerance with(13)N-ammonia positron emission tomography and increased nitric oxide levels. These results suggest that one of the enhanced external counterpulsation mechanisms is development and recruitment of collateral vessels.

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The dependence of lithium cycling efficiency on stack pressure was studied for several electrolytes. To evaluate the cycling efficiency E, we calculated the figure of merit (FOM) of lithium as FOM = 1/(1-E). The effect of solvents on the FOM change with pressure was examined for LiAsF~ solute electrolytes containing 2-methyltetrahydrofuran (2MeTHF), ethylene carbonate (EC)/2MeTHF, propylene carbonate (PC), or EC/PC. The electrolyte LiAsF~-EC/2MeTHF showed the largest FOM (80 at 125 kg/cm2). With the electrolytes LiAsFs-PC and LiAsFs-EC/PC, FOM was less dependent on stack pressure than it was with the electrolytes LiAsF6-2MeTHF and EC/2MeTHF, probably because a different separator was used for the former electrolytes. Examining the effect of the solute on the FOM change with pressure showed that the FOMs for LiPF6-and LiCF3SO3-EC/2MeTHF reached maximum values at 50 and 75 kg/cm ~, respectively, and that the FOM values for LiAsFs-EC/2MeTHF increased with increasing stack pressure up to at least 125 kg/cm 2.

Lithium cycling efficiency was evaluated for LiAsF6-ethylene carbonate/2-methyltetrahydrofuran mixed-solvent electrolyte (LiAsF6-EC/2MeTHF) with several additives: tetraalkylammonium chlorides with a long n-alkyl chain and three methyl groups. The ammonium chlorides with n-alkyl group longer than n-Cl~H26-increased lithium cycling efficiency. Cetyltrimethylammonium chloride (CTAC) produced the best improvement in lithium cycling efficiency. A figure of merit (FOM) of lithium for 0.01M CTAC was 46, which was 1.5 times the FOM for the corresponding additive-free electrolyte. The LiAsF~-EC/2MeTHF with CTAC showed an increase in FOM with stack pressure, but the effect was less than that for the additive-free LiAsF6-EC/2MeTHF. Scanning electron microscope observation showed that the addition of CTAC decreased the needle-like lithium deposition and increased particulate lithium deposition. This deposition morphology may be the main cause of the increase in FOM. The additive had no effect on rate capability for cell cycling at 3 mA/cm 2 discharge and i mA/cm 2 charge.

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Zinc-based secondary batteries are promising power sources with high energy density but their deterioration modes such as dendritic growth and shape changes need to be solved. These drastic morphology changes of the zinc electrode come from the nature of the discharged product that is easily dissolved in the alkaline electrolyte as zincate species. In this study, we attempt to preserve the zinc electrode morphology by employing the zinc oxidation-reduction processes in the vicinity of electrode, which is attained by controlling the electrolyte solvent property with mixing an organic solvent propylene carbonate (PC). The results show that the use of PC-water mixed solvent is effective in restricting the zincates dissolution into the electrolyte and preserving the zinc electrode morphology with no dendrite formation through 500 oxidation-reduction cycles is demonstrated in the electrolyte with high PC concentrations.

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