Battery Enhancement

In today s world, the number of portable and mobile devices is increasing exponentially. Driven by the increasing demands for computing, com-mimications, and transportation, these devices continue to become more advanced. All this progress requires batteries to deliver more performance in terms of power and energy. Actually, the power requirements of computer processors have increased steadily since 1986. Unfortunately battery manufacturers have not been able to catch up with the increasing needs of the new devices. Batteries are still limited by the dynamics and characteristics of the chemical reactions they create. 

In battery-powered portable systems such as laptops and other mobile applications, the span of time during which a device can operate before the energy reserve is depleted is called the battery run-time. For example, current battery technologies have typical energy densities of 200 W/kg, depending 

To increase the run-time of a battery-powered device, the traditional method is to simply increase the number of cells constituting a battery pack. However, this solution only increases the size, weight, and maintenance needs of a portable system and is not acceptable because it reduces device portability and market acceptance. 

In addition, the connection of an ES in parallel with a battery has the effect of reducing the peak value of the current supplied by the battery. This reduces internal losses of the system and the root mean square (rms) value of the current supplied by the battery. The power saved by this connection results in additional run-time for the system. 

Run-time extension during use of ES in combination with 3.6 V 600 mAh lithium ion battery with 2 A GSM load. (Source Smith, T. A., Mars, J. P., Turner, G. A. 2002. Proceedings of 33rd 

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Naoi, K. Iwama, E. Ogihara, N. Nakamura, Y. Segawa, H. Ino, Y., Nonflammable hydro-fluoroether for lithium-ion batteries enhanced rate capability, cyclabiUty, and low-temperature performance, J. Electrochem. Soc. 2009, 156, A272-A276. 

ES application areas include power electronics, memory protection, battery enhancement, portable energy sources, power quality improvement, adjustable speed drives (ASDs), high power actuators, hybrid electric vehicles, renewable and off-peak energy storage, and military and aerospace applications. All these application areas will be discussed in this chapter. 

Lead—Calcium-Tin Alloys. Tin additions to lead—calcium and lead—calcium—aluminum alloys enhances the mechanical (8) and electrochemical properties (12). Tin additions reduce the rate of aging compared to lead—calcium binary alloys. The positive grid alloys for maintenance-free lead—calcium batteries contain 0.3—1.2 wt % tin and also aluminum. 

The galvanic cell studied (shown in Fig. 5.24) utilizes a highly porous solid electrolyte that is a eutectic composition of LiCl and KCl. This eutectic has a melt temperature of 352 °C and has been carefully studied in prior electrochemical studies. Such solid electrolytes are typical of thermal battery technology in which galvanic cells are inert until the electrolyte is melted. In the present case, shock compression activates the electrolyte by enhanced solid state reactivity and melting. The temperature resulting from the shock compression is controlled by experiments at various electrolyte densities, which were varied from 65% to 12.5% of solid density. The lower densities were achieved by use of microballoons which add little mass to the system but greatly decrease the density. 

A variety of complexes exists in solid or liquid state at ambient temperature, in the range required for battery operation. Liquid polybromine phases are preferred since they enable storage of the active material externally to the electrochemical cell stack in a tank, hence enhancing the... 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

The overpotentials for oxygen reduction and evolution on carbon-based bifunctional air electrodes for rechargeable Zn/air batteries are reduced by utilizing metal oxide electrocatalysts. Besides enhancing the electrochemical kinetics of the oxygen reactions, the electrocatalysts serve to reduce the overpotential to minimize... 

Since the early days of using PVC separators in stationary batteries, there has been a discussion about the generation of harmful substances caused by elevated temperatures or other catalytic influences, a release of chloride ions could occur which, oxidized to perchlorate ions, form soluble lead salts resulting in enhanced positive grid corrosion. Since this effect proceeds by self-acceleration, the surrounding conditions such as temperature and the proneness of alloys to corrosion as well as the quality of the PVC have to be taken carefully into account. 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

In conclusion, it seems that solvents appropriate for lithium-ion batteries employing a graphite anode must have high solvation energy, high E°, and high /0 for reduction in order to slow the cointercalation of the solvated ion, and to enhance the formation of the SEI at the most positive potential (far from the Li/Li+ potential). 

The preparation and properties of a novel, commercially viable Li-ion battery based on a gel electrolyte has recently been disclosed by Bellcore (USA) [124]. The technology has, to date, been licensed to six companies and full commercial production is imminent. The polymer membrane is a copolymer based on PVdF copolymerized with hexafluoropropylene (HFP). HFP helps to decrease the crystallinity of the PVdF component, enhancing its ability to absorb liquid. Optimizing the liquid absorption ability, mechanical strength, and processability requires optimized amorphous/crystalline-phase distribution. The PVdF-HFP membrane can absorb plasticizer up to 200 percent of its original volume, especially when a pore former (fumed silica) is added. The liquid electrolyte is typically a solution of LiPF6 in 2 1 ethylene carbonate dimethyl car-... 

Improvement of the ionic current by fast transport in the electrodes. High electronic mobility and low electronic concentration favor fast chemical diffusion in electrodes by building up high internal electric fields [14]. This effect enhances the diffusion of ions toward and away from the solid electrolyte and allows the establishment of high current densities for the battery. 

Battery makers sometimes view separators with disdain the separator is needed but does not actively contribute to battery operation. Consequently, very little work (relative to that on electrode materials and electrolytes) is directed towards characterizing separators. In fact, development efforts are under way to displace microporous membranes as battery separators and instead to use gel electrolytes or polymer electrolytes. Polymer electrolytes, in particular, promise enhanced safety by elimi-... 

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