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The repetitive cycling of lithium metal electrodes in Li metal | ionic liquid electrolytes | Li metal coin cells was investigated. Lithium metal electrodes achieved 800 charge-discharge cycles at current densities of 0.1, 10 and 100 mA cm −2 . Voltage-time plots show evidence for instabilities manifesting themselves as voltage spikes. SEM imaging of cycled electrodes crucially shows no evidence for dendrite formation capable of leading to short circuit conditions, under all cycling regimes. SEM study shows evidence for surface corrosion. Based on the SEM study and cycling behavior a corrosion based equivalent circuit is presented and fitted to impedance data. SEM and impedance data are used to describe the changes in the voltage-time plots and ascribe the voltage spikes observed to changes in the lithium metal surface and subsequent corrosion. FTIR spectroscopy was used to analyze lithium electrodes after cycling and evidence for IL surface coordination and LiOH formation was found.Current demand for portable energy storage devices (i.e., batteries) is growing. The combination of increases in device complexity and functionality in portable electronics as well as development and commercialisation of electric vehicles has resulted in the requirement for increased energy and power from portable energy sources. Due to higher power and energy density, the use of lithium batteries continues to rise, largely at the expense of the traditional chemistries (lead-acid and alkaline nickel). 1 However, use of lithium ion intercalation battery chemistry presents potential issues in terms of safety, thermal stability and ultimate cycle-ability. Moreover, many hold the view that ultimately lithium-ion will also fail to meet growing requirements for power and energy. 2 Addressing the longer term, there are now major research efforts in developing the next generation of lithium batteries, based on either Li-air (oxygen) 3 or Li-sulfur 4 chemistries. Both of these types of battery chemistry offer the promise of significantly more energy and power (e.g. specific capacities of 3842 mAh g −1 (Li-air) and 1675 mAh g −1 (Li-S) compared to 372 mAh g −1 for a Li-ion technology). However, achievement of these impressively high values is predicated on the successful deployment of a reversible lithium metal electrode which, to date, has provided one of the major limitations to further development of this technology.Due to the nature of the currently employed electrolytes, the reactive lithium metal has the ability to chemically or electrochemically react with the electrolyte system to form unstable surface/electrolyte interfaces which ultimately lead to degradation in device performance. 5,6 Furthermore, unstable dendritic growth during the plating reaction of the charging process can, under some circumstances, lead to short circuiting behavior and eventual fire risks. 7 This problem is exacerbated when lithium metal is used with the current generation of aprotic battery electrolytes. 8 A number of researchers have shown that lithium metal i...

In batteries the separator plays a crucial role within the cell. Commercially available separators, e.g. polyolefins, glass fibres, or polyolefins with ceramic coatings, do not have ideal compatibility with ionic liquid (IL) electrolytes. In this study, we report on the use of electrospinning to fabricate poly(vinylidene fluoride) (PVDF) membranes for use with IL electrolyte based batteries. Four electrospun membranes have been prepared; a neat PVDF, PVDF doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and two LiTFSI-doped membranes based on either thermal or UV cross-linking. The membranes were characterised by a number of techniques and the key characteristics of all electrospun membranes included small fibre sizes and high porosity. The tensile strengths of the cross-linked membranes approached those of commercial membranes. Electrochemical performance was measured using coin cell cycling and the thermally cross-linked membrane gave the lowest cell overpotential as well as the lowest cell resistance.

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The effect of ionic strength on the electrodeposition of silver has been investigated in acetonitrile (MeCN) containing TBAPF or in the ionic liquid [EMIm][OTf]. The use of an ionic liquid allows a greater ionic strength to be investigated as the solubility limits of supporting electrolytes in organic solvents can be overcome using neat ionic liquid. The SEM and XRD data show that polycrystalline silver is deposited in a fcc structure and that dendrite formation is retarded at high ionic strength. Electrochemical measurements undertaken in electrolytes of low ionic strength indicate that the deposition and growth of a few nuclei is preferred and leads to dendrite formation. However, at higher ionic strength, the deposition and growth of significantly more nuclei is observed and therefore dendrite growth rates and tip currents are lower leading to the deposition of spherical particulates. Crucially, the data shows that if the ionic strength of the electrolyte is controlled there are no differences between ionic liquids and molecular solvents for the electrodeposition of silver.

The repetitive cycling of lithium metal electrodes in Li metal | ionic liquid electrolytes | Li metal coin cells was investigated. Lithium metal electrodes achieved 800 charge-discharge cycles at current densities of 0.1, 10 and 100 mA cm-2. Voltage-time plots show evidence for instabilities manifesting themselves as voltage spikes. SEM imaging of cycled electrodes crucially shows no evidence for dendrite formation capable of leading to short circuit conditions, under all cycling regimes. SEM study shows evidence for surface corrosion. Based on the SEM study and cycling behavior a corrosion based equivalent circuit is presented and fitted to impedance data. SEM and impedance data are used to describe the changes in the voltage-time plots and ascribe the voltage spikes observed to changes in the lithium metal surface and subsequent corrosion. FTIR spectroscopy was used to analyze lithium electrodes after cycling. Evidence for IL surface coordination and LiOH formation was found.

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