Flat-plate batteries

The tubular-plate technology is used in the manufacture of traction and stationary batteries. Figure 2.53 shows die main stages involved in the classical production process of mbular plates. Only the preparation of positive plates will be described briefly, since the other technological stages are identical to those discussed for flat-plate batteries. 

FIGURE 38.31 Aluminum dissolved oxygen flat-plate battery (attached to Woods Hole Oceanographic Institution buoy.) Courtesy of Alupower, Inc.)... 

The other example, called the nickel/ zinc battery [(-Zn)/KOH/NiOOH(+)], has attracted more attention in two different versions from the "application" and "cell design" viewpoints one is the small cylindrical consumer cell [30], the other one is the flat-plate module for electrotraction [31], A very interesting review with an extended collection of references was pub-... 

Fig. l.l. (a) Gaston Plante s cell and battery (b) flat plate (c) tubular positive plate (d) spiral-wound cell. 

Purpose-built batteries. Gel batteries with either tubular plates or thick, flat plates (> 5 mm) are recommended when a long cycle-life is required. Both designs have a high level of resistance to positive-plate degradation, and can tolerate high levels of positive-grid corrosion. 

The grids of both flat-plate and tubular batteries should not contain antimony or any other additive that may decrease the hydrogen overpotential of the negative electrode. Indeed, it is recommended that ultra-pure lead be used to manufacture both the grids and the active material in order to avoid the possibility of excessive self-discharge at either the positive or the negative plates. 

A flat-plate, gel battery has also been specifically designed for RAPS duty, especially in high-temperature applications [23]. The battery has thick positive plates (5.5 mm), has a large reservoir of moderate strength acid, and is constructed using an ultra-pure form of lead [28] that endows the battery with a high charging dfidency. It is claimed that the battery can provide over 1100 cycles to 100% DoD (3-h rate, 25°C) before the capacity decreases to 75% of the nominal value. 

Flat plate cells are usually made with electrodes spread on screens or grids like lead-acid batteries or industrial Ni-Cd batteries. In these types of batteries the electrodes itself are good metallic conductors To build manganese dioxide batteries as plate cells good conductive screens would be needed. A well known example for a bipolar Mn02-Zn cell in commercial production is the 6 Volt Polaroid camera film battery, a primary battery with a weakly acidic electrolyte. 

The classical technological scheme for the manufacture of flat-plate lead—acid batteries is presented in Fig. 2.52. This technological process is basically used for the production of SLI, traction and stationary batteries. The process involves the following main production stages ... 

Antimony alloys 4—11 wt% Sb, As, Sn, Cu (Ag) Flat plates, tubular plates for traction batteries, older types of stationary batteries... 

Tubular plates offer several advantages over the flat-plate grid design, flie most important of which is that they prevent shedding of the PAM during battery service as it is held within the tubes. Thus, a lower density of the active material can be used. The typical active mass density for tubular plates is 3.6—4.0 g cm (cf. 4.0—4.3 g cm for flat-pasted plates). In addition, the enhanced porosity of the tubular plates improves the active mass utilization coefficient. 

In industrial practice, it is possible to find examples of cells which use unstirred solutions (e.g. electrorefining, batteries), stirred or agitated solutions (e.g. electroplating) and flowing electrolytes (e.g. synthesis, water treatment). Moreover, it is unusual for the flow of solution and the current path, which depends on cell geometry, to be parallel and the electrode may not be equivalent to a flat plate (e.g. bed electrodes, cathodes for plating) as a result, we must write our mass transport expressions in three dimensions. Nor is it always possible to assume that migration of the electroactive species is unimportant. 

Flat plate and tubular positive plate cells are produced for stationary duty, but where reliability is a prime consideration, Plante cells are used. In a Plants cell, the positive electrodes are manufactured by a quite different process. The oxide is formed by electrochemical oxidation (say, 10 mA cm for 20 h) of a lead baseplate or grid, often shaped to increase its surface area, in an electrolyte which contains sulphuric acid and an anion (perchlorate or nitrate) wliich forms a soluble Pb " salt. This leads to a layer of thick porous oxide the nitrate or perchlorate is present to prevent total passivation of the lead surface. The resulting plate, thickness 6—12 mm, is then reduced to form spongy lead metal, is washed thoroughly, and is recharged when in a fabricated cell. The active material formed in this way adheres to the base lead better than pasted materials and therefore cycles more reUably. Against this, there is less active material on each plate and, inevitably, the energy density of the battery will suffer 7—12 Wh kg is typical. 

Lithium ion cells serve the smaU-sealed rechargeable battery market and compete mainly with the Ni-Cd and Ni-MH cells for the various applications. The Li-Ion cells are available in cylindrical and prismatic format as well as flat plate constructions. The cylindrical and prismatic constructions use a spiral-wrap cell core where the ceU case maintains pressure to hold and maintain compression on the anode, separator, and cathode. The lighter-weight polymer constructions utilize the adhesive nature of a polymer/laminate-based electrolyte to bond the anode to the cathode. 

Figure 6.2 Various configurations for extended-area polymer batteries. From left to right concertino, Swiss-roll and flat-plate versions. Electrode 1 (anode), electrolytic membrane, electrode 2 (cathode), current collector.

Lead-battery electrodes can be made as a flat plate with a lead grid as the current collector or as a tubular plate design with a lead rod current collector in the center of tubes. Monopolar electrode current collectors have a conductive lead grid that connects with the terminal. The current collector physically supports the electrode and also collects and carries the current to the electrical system. 

Tubular batteries have flat negative plates opposing the positive tubular plates. Recent approaches to preventing positive plate shedding with improved separator designs have limited the use of tubular positive plate batteries. They are primarily in applications that have deep-discharges or severe vibration. 

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