The zwitterion effect in high-conductivity polyelectrolyte materials

Abstract

The future of lithium metal batteries as a widespread, safe and reliable form of high-energy-density rechargeable battery depends on a significant advancement in the electrolyte material used in these devices. Molecular solvent-based electrolytes have been superceded by polymer electrolytes in some prototype devices, primarily in a drive to overcome leakage and flammability problems, but these often exhibit low ionic conductivity and prohibitively poor lithium-ion transport. To overcome this, it is necessary to encourage dissociation of the lithium ion from the anionic polymer backbone, ideally without the introduction of competing, mobile ionic species. Here we demonstrate the effect of zwitterionic compounds, where the cationic and anionic charges are immobilized on the same molecule, as extremely effective lithium ion 'dissociation enhancers'. The zwitterion produces electrolyte materials with conductivities up to seven times larger than the pure polyelectrolyte gels, a phenomenon that appears to be common to a number of different copolymer and solvent systems.

Ionic Liquid–Heteropolyacid: Synthesis, Characterization, and Supercapacitor Study of Films Deposited by Electrophoresis

“…In this respect, we can mention a recent report of supercapacitor electrodes based on conducting polymers and metal oxides 17 and conducting polymers and heteropolyacids. 18,19 Heteropolyacids have been applied as electrolyte components in several patents [20][21][22] and as electrolyte in electrochemical supercapacitors.23 Their use as active materials for electrochemical supercapacitors in combination with Ru, conducting polymers, or carbon nanotubes and nanofibers has been recently reported.24-32 On the other hand, ionic liquids have been studied extensively for batteries and fuel cells, [33][34][35][36][37][38] and hybrids of ionic liquid-heteropolyacid based especially on Keggin structures have been reported recently for applications in photochromism, 39 homogeneous catalysis, 40 and as fast proton conductors. 41,42 In this paper, we have investigated the use of ionic liquidheteropolyacid hybrids for applications as supercapacitor electrodes in an environmentally friendly neutral pH electrolyte.…”

Organic Solvents Containing Zwitterion as Electrolyte for Li Ion Cells

“…Although these zwitterions have high Tm values, it has been known that the zwitterion/lithium salt mixture exhibited ionic conductivity 18 and BIm-4S act as a lithium ion dissociation enhancer in Li-polymer electrolytes. 17 Therefore, it is considered that liquid domain may not be affected by the addition of appropriate amounts of zwitterion into the liquid electrolyte composed of 1 M LiPF 6 , EC-EMC-DMC (1:1:1 (v/v)), and would increase the ionic conductivity resulting in the positive effect on the performance of Li-ion full cell. BIm-4S and DMIm-3S were found to be 40 mA, 90 mA and 60 mA, respectively.…”

“…The zwitterion produced electrolyte materials with conductivities up to seven times larger than the pure polyelectrolyte gels. 17 The influence of the TiO 2 nanoparticles and the zwitterionic addition on a poly (Li-AMPSco-DMAA) polyelectrolyte was also reported. 19 There are many efforts on utilization of zwitterions in Li batteries, and most of the investigations are focused on ionic conductivity of the zwitterions/lithium salt mixture or ion-conductive poly (zwitterion)s. 20 However, the additive effect of zwitterions on the performance of Li-ion cell (w.r.s liquid electrolyte system) is far less studied.…”

“…Since both cation and anion are tethered in a zwitterion, it is expected that the ions cannot migrate with the potential gradient. 17 Extensive study by Ohno group found that an equimolar mixture of lithium salt such as LiTFSI, LiBF 4 , and LiClO 4 etc. with various kinds of zwitterions showed only a glass transition temperature Tg, and established the relationship between Tg and ionic conductivity of the zwitterion/lithium salt mixture.…”

N719 and N3 dyes for quasi-solid state dye sensitized solar cells - A comparative study using polyacrylonitrile and CsI based electrolytes

“…Figure 4 shows the conductivity as a function of 1000/T for the three electrolyte samples, namely a, b and c. In general, the ionic conductivity in an electrolyte depends on the degree of dissociation of the ionic species in the electrolyte. The greater the ionic dissociation, the better is the conductance (Sharma, 1995;Tiyapiboonchaiya et al, 2004). Thus the increasing trend of conductivity with increasing temperature is an expected behavior.…”