Volumetric energy density, of batteries

The slim or flat rectangular batteries are designed to meet the needs of lightweight and compact equipments. The rectangular shape permits more efficient battery assembly, eliminating the voids that occur with the assembly or cylindrical batteries. The volumetric energy density of batteries can be increased by a factor of about 20%. 

Though these alkaline silver-zinc batteries are quite expensive, they are frequently used in aerospace and military applications because they have high specific and volumetric energy density. These batteries may be kept in a dry state for several years and may be activated by introducing the electrolyte into the cells. Their status of technology and applications was presented by Karpinski et al. [346]... 

One of the obstacles to overcome is the largest volume occupied by DMFC (even when the volumetric energy density of methanol is higher than the Li-Ion batteries), due to the low efficiency with the current DMFC technology. 

The performance of the experimental vehicles was impressive and confirmed the technical feasibility of the sodium/sulphur battery for traction applications. At the same time it was recognised that for commercial viability it would be necessary to improve the volumetric energy density of the battery and to custom-design it for a particular vehicle, as well as extending the lifespan and reliability of the cells. These developments involve problems of cell and battery design and further work in Britain has been directed towards these goals. 

Table 2.2 shows the maximum amount of work that can be converted into electricity from various fuels, in theory. Compared with the gravimetric and volumetric energy density of 1 MJ kg or <2 MJ oflithium-ion and zinc-air batteries,... 

Energy density. Both the weight and size of the battery are critical, particularly in aerospace, military, and spacecraft applications when multiple battery modules are required to meet the output power level for the desired service life. For both the gravimetric and volumetric energy densities, LiCF batteries enjoy a distinct advantage. 

FIGURE 7.9 Volumetric energy density of primary battery systems. 

Flat cell designs increase the available space for the cathode mix because the package and electrical contacts are minimized, thereby increasing the energy density. In addition, a rectangular construction reduces wasted space in multi-cell assemblies, (which is, in fact, the only application for the flat cell). The volumetric energy density of an assembled battery using flat cells is nearly twice that of cylindrical cell assemblies. 

A solid-polymer credit-card battery has been developed by Yuasa Battery Co. in Japan. This 0.1-rrrm-thick battery is composed of MnOj, a solid-polymer electrolyte, and hthium, and has a volumetric energy density of 400 W h dm . It retains 70% of its capacity over 35 cycles of charge/dischatge. 

Commercially available oiganic liquid electrolyte primaiy batteries include Li/SOj, LiA jOs. Li/(CF)x, Li/MnOj, Li/FeSj, Li/CuS, and Li/CuO. Prototypes of oiganic liquid electrolyte secondary batteries such as the Li/TiSj and Li/MoSj systems, depending upon cell sizes, can deliver specific energies of 90 to 140 W h kg and volumetric energy densities of 0.16 to... 

High energy density A volumetric energy density of 300-500 Wh/dm is superior to most conventional battery systems. 

Direct Methanol Fuel Cell The liquid-fed direct methanol fuel cell (DMFC) is generally seen as the most viable alternative to lithium ion batteries in portable applications because DMFC systems require less ancillary equipment and can therefore potentially be more simphfied compared to an H2 PEFC. Additionally, the use of a liquid fuel simphfies storage. The DMFCs can potentially compete favorably with advanced Li ion batteries (which currently power many wireless portable apphcations) in terms of gravimetric energy density of 120-160 Wh/kg and volumetric energy density of 230-270 Wh/L. While both H2 PEFCs and DMFCs are strictly PEFCs (both use the same flexible polymer electrolyte), the DMFC feeds a liquid solution of methanol and water to the anode as fuel. The additional complexities of the low-temperature methanol oxidation reaction prevent the DMFC from... 

Commercial and non-commercial carbons were tested for their applicability as anode of lithium-ion battery. It was found that Superior Graphite Co s materials are characterized both by high reversible capacities and low irreversible capacities and thus can be regarded as good candidates for practical full cells. Cylindrical AA-size Li-ion cells manufactured using laboratory techniques on the basis of SL-20 anode had initial capacities over 500 mAh (volumetric energy density ca. 240 Wh/dm3). Boron-doped carbon... 

The primary objective of miniature battery design is to maximize the energy density in a small container. A compromise must be reached, however, since volumetric energy density decreases as cell volume decreases and the dead volume due to containers, seals, etc. becomes increasingly significant. A plot of energy density as a function of total volume is given in Fig. 3.28 for the zinc-mercuric oxide and zinc-silver oxide systems. 

In summarizing the status of these R D efforts, it can be said that Ca-TC cells are promising primary battery systems and, in several respects, appear superior to commercial Li-TC or Li-S02 cells. These include the volumetric energy density, which can be higher for Ca-TC cells than for Li-S02 cells by 30% [451]. In addition, the safety features of Ca-TC cells are better than those of Li-TC or Li-S02 batteries. While the melting point of Li (180°C) limits their use at temperatures well below this point, Ca-TC cells withstand heating up to 600°C and short circuiting at this temperature [452], The state of the art of these studies includes tests on the performance and safety features of Ca-TC cells sized from 3.5 A h to 7000 A h [453],... 

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