EV batteries

Li—Al/FeS cells have demonstrated good performance under EV driving profiles and have deUvered a specific energy of 115 Wh/kg for advanced cell designs. Cycle life expectancy for these cells is projected to be about 400 deep discharge cycles (63). This system shows considerable promise for use as a practical EV battery. 

Efforts to develop commercially viable EV versions of advanced battery systems continue. The ultimate goal is to develop battery technology suitable for practical, consumer-acceptable electric vehicles. The United States Advanced Battery Consortium (USABC) has been formed with the express purpose of accelerating development of practical EV batteries (83). 

L.Chen, F.Wu, M.Tong et al. Advanced nanocrystalline Zr-based AB2 hydrogen storage electrode materials for NiMH EV batteries. Journal of alloys and compounds, 293-295, 508-520 (1999)... 

Fig. 7.34 Specification of the Sony Corporation lithium ion EV battery. (By permission of Sony Co.)...

A commercial nickel-zinc battery is considered to be the most likely candidate for electric vehicle development. If the problems of limited life and high installation cost ( 100-l50/kW-h) are solved, a nickel-zinc EV battery could provide twice the driving range for an equivalent weight lead-acid battery. Work is developmental there is no commercial production of nickel-zinc batteries. 

In general, the specific peak power decreases with the depth of discharge (DOD) (cf. Fig. 3). Therefore, EV battery specification with respect to range and allowable depth of discharge limit should pertain to (whichever comes first) DOD values at which EV becomes incapable of the demanded acceleration, or to which the system... 

Battery price is calculated on the basis of the material and manufacturing costs. The cost of the active materials is directly related to their availability. With the exception of Na-S, Fe-air, and a few other exploratory systems, all EV battery candidates are based on materials whch are either not too abundant worldwide, reside in diluted ores, or can be extracted viably only from ores located geographically in a few areas. The Imports may be subject to politically Induced shortages or stoppages, in analogy to the gasoline situation. In some cases, even the domestic resource utilization may become prohibitive because of the environmental impact. 

These examples illustrate the tremendous technological challenge involved in the simultaneous optimization of several attributes required for a viable EV battery. 

The improvements, aimed at a >60-Whkg system, have to date resulted in EV battery prototypes with specific energies close to 50Whkg at C/3. Their dynamometer tested range is, at best, some 20% higher than that of the Pb-A EV prototypes. 

The energy efficiency of the EV battery is <50%. The major cause of coulombic inefficiency (10-30%) is the chemical reaction of zinc with dissolved chlorine. Thanks to kinetic inhibitions, only about 1% inefficiency (over the complete cycle) derives from the evolution of hydrogen and carbon oxides. The latter derive from... 

A very tentative comparison of the quantitative characteristics of EV battery candidates is given in Table 6 for near-term and advanced systems. (Information concerning many exploratory systems is hardly available, even for approximate extrapolations). Values quoted in Table 6 must be treated with considerable caution. 

Zinc-Bromine Battery Development, Sixth Program Review, Phase III, Exxon Research and Engineering Company to DOE/SANDIA, 16-3187 (May 1984). Insulation and Enclosure Development for High Temperature EV Batteries, Final Report, Union Carbide, Linde Division to DOE, Contract No. DE-AC02-8DET25426 (May 1982). 

C under the Dynamic Stress Test for EVs in accordance with the United States Advanced Battery Consortium Procedure 5B. This has a variable discharge profile based on specific power requirements, with a maximum of 150 Wkg when related to a full-sized EV battery. For the experimental cells, the peak power was equivalent to a current density of 16.3mAcm . ... 

As a result of such considerations, the surface area, particularly fine-fibre content of AGM separators has been the subject of two ALABC projects on EV batteries. In the first project [16], acid stratification was found to decrease as the surface area of the separator was increased, see Table 7.5. Nevertheless, any advantage in terms of battery cycle-life was less clear-cut, see Table 7.6. 

It remains to be seen which of the many separator materials will be successful in commercial applications. Obviously, this will depend on costs and market requirements, as well as on performance. Although most of the developments reviewed here have been directed towards EV batteries, many of the findings are equally applicable to valve-regulated lead-acid batteries intended for use in other applications. 

Fig. 11.4. Cycle-life dependence on DoD for flooded lead-acid, VRLA, and Ni-MH batteries. Based on nominally ambient cycling conditions, moderate rates of discharge (< 1C rate), short cell strings, and periodic full recharge data from 12-V automotive, Ni-MH EV batteries, and VRLA EV batteries...

---