Electrolyte Innovations

Advances in the understanding of ion desolvation and transport mechanisms have furthered the utility of these materials. However, environmental toxicity and safety issues associated with organic electrolytes coupled with their still limited operational potential windows shifted the focus to the development of ionic liquids as electrolytes for new ESs. With ionic liquid electrolytes, operating voltages can be increased to 3.5 V or more without instability issues arising. Moreover, ionic liquids have well defined ion sizes and do not have ion salvation and desolvation mechanisms that plague aqueous and organic electrolyte systems. 

The primary technical challenge facing their application is the limited 

The development of ionic liquid electrolyte-based ESs is a promising approach but it is still in an infancy stage. With further research on carefully selected ionic liquid combinations and compatibility investigations with various electrode active materials, marked progress is expected for the ES industry. 

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This new formulation of electrolytes based on a mixture of EC with a linear carbonate set the main theme for the state-of-the-art lithium ion electrolytes and was quickly adopted by the researchers and manufacturers. Other linear carbonates were also explored, including DEC, ° ethylmethyl carbonate (EMC), ° and propylmethyl carbonate (PMC), ° ° and no significant differences were found between them and DMC in terms of electrochemical characteristics. The direct impact of this electrolyte innovation is that the first generation carbonaceous anode petroleum coke was soon replaced by graphitic anode materials in essentially all of the lithium ion cells manufactured after 1993. At present, the electrolyte solvents used in the over one billion lithium ion cells manufactured each year are almost exclusively based on the mixture of EC with one or more of these linear carbonates, although each individual manufacture may have its own proprietary electrolyte formulation. 

The zinc chloride cell, which was first patented in 1899, IS actually an adaptation of the Leclanche cell. The major innovation was the development of plastic seals that permitted the replacement of animoliitim chloride in the electrolyte. 

The electrolyte was a solution of ammonium chloride that bathed the electrodes. Like Plante s electrochemistry of the lead-acid battery, Leclanche s electrochemistry survives until now in the form of zinc-carbon dry cells and the use of gelled electrolyte.12 In their original wet form, the Leclanche electrochemistry was neither portable nor practicable to the extent that several modifications were needed to make it practicable. This was achieved by an innovation made by J. A. Thiebaut in 1881, who through encapsulating both zinc cathode and electrolyte in a sealed cup avoided the leakage of the liquid electrolyte. Modern plastics, however, have made Leclanche s chemistry not only usable but also invaluable in some applications. For example, Polaroid s Polar Pulse disposable batteries used in instant film packs use Leclanche chemistry, albeit in a plastic sandwich instead of soup bowls.1... 

Foller PC (1993) Applications of gas diffusion electrodes in prospective electrolytic processes, Electrochem Processing, Innovations and Progress, April 21-23, Glasgow... 

The paper contains several innovations in the interpretation of polarographic reduction potentials, Eyi. One is the recognition that the Eyi obtained in the presence of base-electrolytes is not that of an isolated, solvent-solvated cation, but of one which is part of an ion-pair or of a higher aggregate. A practically useful innovation is to use the Em of the triphenylmethylium ion as the zero of the potential scale in all solvents. By means of this device one can compare a wide range of Ey2 differences in different solvents, and it is especially useful because that ion is stable in strongly acidic media in which the commonly used marker ferrocene decomposes. 

However, in addition to these advances, the paper contains two further innovations which are important outside the domain of polymer chemistry. One is the demonstration that in adequately pure systems aliphatic carbenium tetrahaloaluminates, R3C+A1X4" in solution are stable electrolytes. The other is the direct demonstration that A1X3 and isobutene form a stable, reversible, complex. 

Another useful innovation is the formulation of an equation relating Up to c IKD where c is the total concentration of the electrolyte and KD the dissociation constant of the ion-pairs. In a later paper it will be noted that this is the reciprocal of a (much simpler) equation relating KD/c to pH which had been derived previously by Bos and Treloar (A). 

Japan Fuji Electric has developed a 100 kWe on-site system. To date, they have tested a 50 kW power plant using innovative cell design that improves electrolyte management. They tested this stack (154 cells) for about 2,000. They have tested 65, 50 kWe units for a total cumulative operating tome of over 1 million hours. They have tested 3, 500 kWe units for a total of 43,437 hours. Their latest design, FPIOOE, has been shown to have a net AC efficiency of 40.2% (LHV). 

The materials of greatest interest in view of fundamental understanding and design are the polymer electrolyte membrane and the catalyst layers. They fulfill key functions in the cell and at the same time offer the most compelling opportunities for innovation through design and integration of advanced materials. 

D. Cahan, Kohlrausch and electrolytic conductivity instruments, institutes, and scientific innovation , Osiris, 2d Ser., 1989, 5, 167-85. 

The German public funded project NEMESIS focuses on the design and development of microreactors for the synthesis of ionic liquids at pilot scale [52], Scientific objectives are to increase the yield of the corresponding ionic liquid as well as to decrease reaction time from hours up to days currently. Ionic liquids, a new innovative class of materials, are synthesized using microreaction technology. Possible application fields are their use as electrolytes for the elaborate deposition of metals. A concept for regeneration of the electrolyte is also considered. 

The potential impact is extremely broad and fundamental in nature, because the research will explore a totally innovative approach to metal finishing technology, which has never been exploited previously. The use of this completely different type of solvent/electrolyte system, entirely changes the normal behavior of metal finishing processes seen in traditional aqueous electrolytes and an extensive range of entirely new processes and products can be expected. 

The use of gas discharges for electrochemical processes has been investigated for more than 100 years, and a full account is beyond the scope of this chapter. We will focus on a few innovative and seminal studies which can be regarded as major advances. The first plasma electrochemical experiments were already reported in 1887 by Gubkin [1], in the same year when Arrhenius published his most influential paper on electrolytic dissociation of salts in water [18]. Gubkin investigated... 

Electrolytes pose a special problem in chemical thermodynamics because of their tendency to dissociate in water into ionic species. It proves to be less cumbersome at times to describe an electrolyte solution in thermodynamic-like terms if dissociation into ions is explicitly taken into account. The properties of ionic species in an aqueous solution cannot be thermodynamic properties because ionic species are strictly molecular concepts. Therefore the introduction of ionic components into the description of a solution is an etfrathermodynamic innovation that must be treated with care to avoid errors and inconsistencies in formal manipulations.20 By convention, the Standard State of an ionic solute is that of the solute at unit molality in a solution (at a designated temperature and pressure) in which no interionic forces are operative. This convention implies that an electrolyte solution in its Standard State is an ideal solution,21 as mentioned in Section 1.2. 

This innovative renewable energy technology could leap frog other renewable energy technologies for electrolytic production of hydrogen—a potentially important transportation fuel for our future. 

D.A. Fanta etal, US Patent 6,350,545 (February 26, 2002) Assignee 3M Innovative Properties Company Utility Electrolyte in Lithium Batteries... 

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