Present battery systems

Clearly, the sizes of the particles and the pores (i.e. the porosity of the paste) are important in determining the performance of the battery. In practice, porosity should be about 50%. Below this value, the utilization of the active material suffers due to pore-blocking, and above it the mechanical stability becomes a problem. Hence, there is a trade-off between capacity and cycle life. 

The loading of the paste and the thickness of the porous layer, also affect performance (Table 11.6). Thin plates improve capacity, particularly at high discharge rates and also give a higher power density. 

5 PRESENT BATTERY SYSTEMS 11.5.1 Lead-acid batteries 

While all are based on the same electrochemistry, the Pb02-PbS04 positive electrode and the Pb-PbS04 negative electrode in aqueous H2SO4 (Table 11.1) a number of technologically quite different Pb-acid batteries are manufactured 

The most important market remains the car battery for starting, lighting and ignition with approximately 50 x 10 units per year being sold in the USA. Lead-acid batteries are, however, also used on a very large scale for traction (e.g. delivery vans, milk floats, forklift trucks, industrial trucks there are more than 100000 such vehicles in the UK) and for stationary back-up or emergency power supplies. More recently, small lead-acid cells to compete with high-quality primary and nickel-cadmium cells for instruments, radios, etc. have also become available. 

Invariably, SU car batteries are designed with each cell having parallel pasted electrodes and a separator, and Fig. 10.6 shows a cutaway diagram of a typical 

Energy densities for these larger batteries normally lie in the 20—30 Wh kg range although the contractors in the US Department of Energy car traction battery programme now claim values of 37—42 Wh kg for test Pb/acid units. 

Lead/acid batteries are used for many diverse remote and standby duties and hence are manufactured with a wide range of voltage and current capabilities and capacities. Pb/acid batteries do self-discharge slowly because of some reaction between the active materials and water as a result the batteries are often on constant trickle charge. 

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Present battery systems 559 Table 11.6 Effect of paste loading on performance... 

To judge which battery systems are reasonable for a possible application, a wide knowledge of the principles of functioning and the different materials utilized is necessary. The following sections therefore present a short introduction on this topic and on the basic mechanisms of batteries... 

At present batteries worth more than 30 billion USD are produced every year and the demand is still increasing rapidly as more and more mobile electronic end electric devices ranging from mobile phones to electric vehicles are entering into our life. The various materials required to manufacture these batteries are mostly supplied by the chemical industry. Ten thousands of chemists, physicists and material scientists are focusing on the development of new materials for energy storage and conversion. As the performance of the battery system is in many cases a key issue deciding the market success of a cordless product there is in fact a kind of worldwide race for advanced batteries. 

While during the NATO-CARWC, the session on metal-air batteries featured other important contributions, it is, perhaps, by coincidence that only presenters from the former Eastern Block submitted their papers for this volume. In this regard, the editors wish to note, that papers below may be of special interest to the western reader, as they offer a rather unique insight into the science and application of the metal-air battery systems from the... 

David P. Wilkinson, (Ballard Power Systems) and David Thompsett (Johnson Matthey Technology Centre), "Materials and Approaches for CO and CO2 Tolerance for Polymer Electrolyte Membrane Fuel Cells," presented at the 1997 Proceedings of the Second International Symposium on New Materials for Fuel Cells and Modern Battery Systems, Montreal, Quebec, Canada, July 6-10, 1997. 

A calculation of the power requirements of the smart dust mote underscores our point that the present generation of batteries cannot effectively power this device. Thin-film batteries are among the most advanced of the lithium battery systems, with a capability to scale down to dimensions on the same order of magnitude as the cubic millimeter of the dust mote. 3 The energy density for the thin-film system is 2 J mm , which matches or exceeds standard lithium ion systems, such as those that power laptop computers. A key design requirement for the smart dust mote is that the power consumption cannot exceed 10 juW. If the dust mote uses this power continuously over a day, it will consume 1 J. 

Like the Li/FeSx system, which is presently the most advanced rechargeable battery system based on a molten salt electrolyte, the Na/S system is presently the most advanced rechargeable battery system based on a solid electrolyte (beta-alumina) It operates at about 300 C. 

At the present time, a large number of spent batteries are disposed of directly into the urban waste stream without proper controls. In addition to the most common systems such as zinc-carbon, alkaline manganese and nickel-cadmium, these now include, at an increasing rate, nickel-metal hydride and lithium cells. Such disposal is of serious concern because of the possible effects of battery components on the environment. Consequently, most countries are now evolving policies for collection and recycling. The majority of lead-acid batteries are recycled, but the number of recycling plants in operation worldwide for other battery systems is still very small due to the unfavourable economic balance of such operations (see Table A3.1). Some of the procedures for the disposal and recycling of battery materials are now briefly described. 

Fig. 13.51. Theoretical specific energy plotted against the equivalent weight for various batteries. The present commercial battery systems are in the lower right corner. Types of electrolytes , molten salt or ceramic o, aqueous. (Reprinted from K. Kordesch, in Comprehensive Treatise of Electrochemistry, J. O M. Bockris, B. E. Conway, E. Yeager, and R. E. White, eds., Vol. 3, p. 123, Plenum, 1981.)...

The obvious drawback to the use of Li alloys instead of Li metal in batteries is the lower potential, specific charge, and specific energy of Li-alloy-based battery systems, compared with Li metal batteries. The work with Li alloys as alternatives for Li metal batteries began in the early 1970s [293], Table 8, taken from Ref. 294, presents some data on Li alloys tested as anodes in rechargeable Li battery systems. The various examples of Li alloys shown in Table 8 can be divided into three groups ... 

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