Electrolyte density

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 problem does indeed arise when the calculated transition time becomes more than a few seconds. The constant depletion of the electron acceptor makes the electrolyte density near the interface different from that in the bulk. These density differences in different regions of the electrolyte upset the initial condition of hydro-... 

Fig. 5.2 Approximate open circuit voltage and electrolyte density as a function of percentage service capacity for the lead-acid cell...

The electrolyte density is very important in order to obtain a good separation between melt and metal and to avoid the risk of mixing bath and metal. The density of molten cryolite has been measured by several authors [162-167], According to Edwards et al. [164] the temperature dependence of the density of cryolite is given by... 

Apart from the surface composition the bulk properties of a particle material will affect composite deposition. Particle mass transfer and the particle-electrode interaction depend on the particle density, because of gravity acting on the particles. Since the particle density can not be varied without changing the particle material, experimental investigations on the effect of particle density have not been performed. However, it has been found that the orientation of the plated surface to the direction of gravity combined with the difference in particle and electrolyte density influences the composite composition. In practice it can be difficult to deposit composites of homogeneous composition on products where differently oriented surfaces have to be plated. 

Figure 7. OCV and electrolyte density as a function of the percentage of discharge capacity for the lead-acid cell [1] (by permission of Arnold C.A. Vincent, B. Scrosati, Modern Batteries. An Introduction to Electrochemical Power Sources, 2nd edition, Edward Arnold, London, 1997).

In applying Eq. (14) to mass transport-controlled electrolytic processes, an important step is the estimation of the effect of the imposed magnetic field strength on properties of the diffusion boundary layer. Since electrolyte density is space-variant in this layer, the right-hand side of Eq. (14) is nonzero, even if the low-Rem approximation [i.e., curl(j B) = 0] is invoked. This is clearly shown by the expanded form... 

The detachment of the bubble occurs if the condition FB = Fc is satisfied. It follows that the mean bubble departure radius (Rd) is well defined for a given electrode—electrolyte configuration (typical values are around 50 pm [115]). It may be expected that the mean bubble departure radius is mainly a property of the electrode (the electrode surface roughness which influences D), the electrode wettability (through the contact angle i9), and the electrolyte (density and surface tension of the electrolyte), but not of the current density j. However, the question is whether a cavity (nucleation site) is active or non-active. The current density may influence the activation of the nucleation sites. 

Most of the safety concerns have been remedied in modern batteries. Older batteries had a cap on each cell for monitoring electrolyte density and replacing water lost on overcharging. During recharging, some water could be electrolyzed to H9 and O2, which could explode if sparked, and splatter H2SO4. Modern batteries are sealed, so they don t require addition of water during normal operation, and they use flame attenuators to reduce the explosion hazard. 

This section describes a procedure for predicting densities In multicoraponent electrolyte solutions comprised of strong electrolytes. The treatment is based upon a mixing rule which requires fitting binary (water electrolyte) density... 

The value employed for Az was 1.31, or about 2/3 the "ideal value of 2.0. One possible explanation of this result might be that Tq is lower than assumed, because of a less dense super-lattice structure than (2x2). The (2x2) structure, however, seems optimal, since (on a <100> Pt surface) it has about the same ion density as a <111> lattice layer in AgBr, which is the densest permissible packing for a layer of Br" ions. A less dense adsorption site spacing would correspond to a considerable drop in electrolyte density at the electrode surface, while a denser spacing would not permit free interchange between occupation by Ag" and Br". 

THE PROBLEM Electrosynthesis is to be carried out in a parallel plate reactor with electrodes 10 cm wide, the electrolyte gap being 0.5 cm. The synthesis is to take place in a fully developed turbulent hydrodynamic regime so that mass transfer characteristics will be well defined. Calculate the minimum flow rate required and the value of the mass transfer coefficient if the electrolyte density is llOOkg/m and its viscosity is 3 X 10 Ns/m. The diffusivity of the diffusing species is 0.92 x 10 m /s. 

Lead sulfate is formed on both types of plates and sulfuric add is consumed. The density of the sulfuric acid can thus indicate the charge/discharge condition. In a charged battery the electrolyte density is 1.2-1.3 g/cm. The operation of a lead accumulator is disturbed by contamination by certain elements in the electrolyte, especially chlorides, iron, manganese and platinum. Because of that, replenishment of electrolyte must always occur with ion-free water. 

Nominal capacity after 10 discharges electrolyte density 1.28 + 0.01 kg/L electrolyte temperature 25 °C. 

Nominal capacity after 10 discharges electrolyte density 1.28 + 0.01 kg/L electrolyte temperature 25 °C. Table 2.7 Lead-acid traction batteries in plastic trays with single cells and positive tubular plates (DIN 43 598 part 2). ... 

Low-maintenance and enclosed cells with tubular positive plates (PZS) conforming to the older DIN 43 595 are also offered with improved capacities, up to 20% compared to the normal design. This could be performed by increasing the electrolyte density from 1.27 to 1.29-1.31 kg/L, enlarged plates and reduced space for mud collection, and a lower electrolyte level above the plates. These measures reduce service life, and therefore these cells should be used only if the higher capacity per volume is really needed, e.g., if a second battery per shift is no longer needed. 

The measure for a successful equalizing charge is the electrolyte density, which only can be measured on vented cells. Valve-regulated cells need control of the open voltage after charge or a capacity test. 

With vented cells the sulfurization effect can be observed by measuring the electrolyte density when the nominal density cannot be reached. Vented cells need critical judgment of the open voltage or the result of a capacity test. 

Check the electrolyte density of all cells check the electrolyte temperature of a cell placed in the middle of the battery and make a written report. Control the fastening of the terminals. 

Perform equalizing charges of batteries showing sulfurization (if the nominal electrolyte density cannot be measured after a normal recharge). 

A variety of formation conditions are used, with variations in electrolyte density, charging rate (current), and temperature. Electrolyte is typically dilute, in the range of 1.050-1.150 specific gravity. The charging rate is usually fixed, but some manufacturers use a sequence of two or three different charging rates for different periods of time. 

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