Electrolytes and Separators

The organization of the Handbook of Battery Materials is simple, dividing between aqueous electrolyte batteries and alkali metal batteries and further in anodes, cathodes, electrolytes and separators. There are also three more general chapters about thermodynamics and mechanistics of electrode reactions, practical batteries and the global competition of primary and secondary batteries. 

Separators for batteries can be divided into different types, depending on their physical and chemical characteristics. They can be molded, woven, non-woven, microporous, bonded, papers, or laminates. In recent years, there has been a trend to develop solid and gelled electrolytes that combine the electrolyte and separator into a single component. 

Lithium secondary batteries can be classified into three types, a liquid type battery using liquid electrolytes, a gel type battery using gel electrolytes mixed with polymer and liquid, and a solid type battery using polymer electrolytes. The types of separators used in different types of secondary lithium batteries are shown in Table 1. The liquid lithium-ion cell uses microporous polyolefin separators while the gel polymer lithium-ion cells either use a PVdF separator (e.g. PLION cells) or PVdF coated microporous polyolefin separators. The PLION cells use PVdF loaded with silica and plasticizer as separator. The microporous structure is formed by removing the plasticizer and then filling with liquid electrolyte. They are also characterized as plasticized electrolyte. In solid polymer lithium-ion cells, the solid electrolyte acts as both electrolyte and separator. 

An ultrasonic nebulizer (USN) has been found to be amenable to CE-ICP-MS interfacing [102]. The ground path was again provided by a sheath electrolyte, and separations were superior to those obtained by using a concentric nebulizer. It should be noted that the noisy background obtained by the USN may not give better detection limits than other nebulizers. 

Nation 117 is the PEM and functions simultaneously as electrolyte and separator. Current densities up to 0.4A/cm" and current efficiencies up to 90% were obtained [184c]. 

Both the anode and the cathode are composed of a coating of the electrochemically active material onto a current collector (copper or aluminum). Another key component of the battery is the separator that physically separates the two electrodes and prevents contact between them. In the case of a liquid technology battery, a polyolefin separator is typically used and a liquid electrolyte is used to transport the Li ions from one side of the porous separator to the other. In the case of a polymer Li ion battery, a polymer, such as PVDF, is used to form a porous structure, which is then swollen with a Li" " conducting liquid electro-lyte. " This results in a gel-type electrolyte, which plays the dual role of electrolyte and separator, with no free liquid present. 

The PE MFC has a solid ionomer membrane as the electrolyte, and a platinum, carbon-supported Pt or Pt-based alloy as the electrocatalyst. Within the cell, the fuel is oxidized at the anode and the oxidant reduced at the cathode. As the solid proton-exchange membrane (PEM) functions as both the cell electrolyte and separator, and the cell operates at a relatively low temperature, issues such as sealing, assembly, and handling are less complex than with other fuel cells. The P EM FC has also a number of other advantages, such as a high power density, a rapid low-temperature start-up, and zero emission. With highly promising prospects in both civil and military applications, PEMFCs represent an ideal future altemative power source for electric vehicles and submarines [6]. 

The electrochemical membrane reactor utilizes platinized Nafion 117 as the PEM. It functions both as the electrolyte and separator. Hicks and Fedkiw [2.454] present results for the oxidation, at atmospheric pressures, of acetic acid (in the vapor phase with a nitrogen diluent) to ethane and carbon dioxide, accompanied with hydrogen evolution at the counter electrode. For cell voltages ranging from 4 to 10 V, current densities from 0.06 to... 

The basic design of a fuel cell, an ionically conducting electrolyte and separator layer sandwiched between two electronically conducting gas diffusion electrodes (the fuel anode and the oxidant cathode, respectively), is shown schematically in Fig. 2 for a polymer electrolyte fuel cell with an acidic electrolyte and hydrogen and oxygen as the corresponding reactants. Typically, under open circuit conditions, H2/air fuel cells exhibit a cell voltage of... 

Fig. 13.15 Wettability study of the cell materials. Sequence of contact angle change of the electrolyte and separator (a) without Phoslyte (b) with Phoslyte...

The discovery and the characterization of ionically conducting polymeric membranes (see Chapters 1 and 2) have provided the interesting possibility of developing new types of lithium batteries having a thin-layer, laminated structure. Various academic and industrial laboratories [1-5] are presently engaged in the development of this revolutionary type of battery, i.e. the so-called Lithium Polymer Battery (LPB). The key component of the LPB is the polymeric ionic membrane which acts both as electrolyte and separator furthermore, the membrane can be easily fabricated in the form of a thin film (typically 50 jum thickness) by a number of convenient casting techniques. 

The electrolyte and separator in Ni-Cd batteries do not contribute significantly to overall impedance due to the use in such batteries of highly conductive, concentrated KOH/LiOH solution. The effect of electrolyte and current collector resistance adds to the serial resistance of the cell. Typical impedance spectra of a Ni-Cd battery is shown in Figure 4.5.15. 

A typical lithium-ion PHEV2 cell with 26 Ah and 3.7 V weighs 716 g [1,3]. To calculate the required amount of cathode, anode, electrolyte and separator materials, we approximate the values for a ternary mixture nickel cobalt manganese (NCM). The exact material split depends on the cathode/anode material type and the cell chemistry. For our calculation, we use the following proportions ... 

New developments on the material side (mainly cathodes, but also anodes, electrolytes and separators) and in production technology will drive costs down even further. But these new developments will require more investments for their... 

It is a rechargeable battery and consists of the following main materials positive electrode, negative electrode, electrolytes, and separators. However, in some reports, the positive electrode and negative electrode are called as cathode and anode, respectively. Scientifically speaking, this calUng is not pertinent. 

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