Voltage primary batteries

All lithium based batteries use nonaqueous electrolytes because of the reactivity of lithium in aqueous solution and because of the electrolyte s stability at high voltage. The majority of these cells use microporous membranes made of polyolefins. In some cases, nonwovens made of polyolefins are either used alone or with microporous separators. This section will mainly focus on separators used in secondary lithium batteries followed by a brief summary of separators used in lithium primary batteries. 

The main reason for avoiding water as a solvent is the fact that the electrolysis of aqueous solutions of alkali and alkaline-earth metal salts commences at 1.7-2.0 volts (depending on the electrode material) and results in the evolution of O2 and H2. If the cell itself has a higher voltage, internal electrolysis can, but not always does occur, accompanied by the evolution of H2 and O2 and by self-discharge (117). However, this fact does not preclude attempts to create moist primary batteries with Li, Na or Ca, if the activity of H2O is kept sufficiently low. 

If GO is used as a host lattice for Li+ in aprotic electrolytes, reversibility is improved [577]. The potential level is distinctly more positive than with donor GIC, at about —1 V vs. SHE. An all-solid-state Li/GO battery with PE0/LiC104 as solid electrolyte was reported by Mermoux and Touzain [578], but rechargeability is poor. Recently, the structure of graphite oxide was studied by its fluorination at 50-2()0 °C [579]. C-OH bonds were transformed into C-F bonds. The examples, in conjunction with Section 2, show that the formation or cleavage of covalent C-O (C-F) bonds makes the whole electrochemical process irreversible. Application was attempted in lithium primary batteries, which have a voltage of 2-2.5 V. Really reversible electrodes are only possible, however, with graphite intercalation compounds, which are characterized by weak polar bonds. 

Leclanche s cells are produced in cylindrical and flat (prismatic) designs in different sizes. Their energy density at 20 °C is very low (65 Wh kg-1 for the cylindrical size, see Table 2) compared to the other primary battery technologies. Fiowever, they are the cheapest batteries available in the market (see Table 2). Their nominal voltage is 1.5 V, which is comparable with other battery technologies (see Table 2). 

Another problem is the cost of the fuel - sodium borohydride costs 55/kg. The fuel contribution to the cost of electricity (COE) for the DBEC will be 9.7/kWh, even if the operating voltage of the DBFC can reach 1.0 V. It is 100 times that of the hydrogen gas. At present it is very difficult to apply the DBEC to high power applications such as a car or a home power generator. However, it is very possible that DBFCs could be used in place of batteries in low power applications such as primary batteries or secondary batteries for notebook computers, cordless electric tools and so on because the COE for batteries is rather high. For example, the COE for an alkaline primary battery is up to 450/kWh. 

One of the important advantages of primary batteries eonsists of very simple maintenance procedures. Most such batteries require no servicing. Before a battery is switched on, its appearance and the remaining service life are checked sometimes actual parameters are measured (open-circuit voltage (OCV) and the initial discharge voltage). Correct polarity and reliable contacts must be ensured a violation of polarity correspondence may result in serious disorders and even in the breakdown of load circuitry, especially circuits involving transistors and electrolytic capacitors. 

Fig. 3.6 Discharge voltage profile of the Mn02 (0H) cathode of a Zn/Mn02 primary battery showing solid-solution (one-phase) and two-phase compositional ranges...

Lithium-Metal Salt secondary batteries are analogous to the Lithium-seawater primary battery [3]. A Li -ion solid electrolyte separates a nonaqueous anolyte and an aqueous cathode. For example, a Lithium anode with a carbonate anolyte and an aqueousFe(CN)g /Fe(CN)g cathode has been shown to give aflat voltage F 3.4 V with an efficiency that increases with the molar ratio of iron cyanide in the cathode solution [27]. This promising approach requires development of a Li-ion solid electrolyte having a (Tli > 10 8/cm at room temperature that is stable to an acidic cathode solution and is not reduced by contact with a Li° dendrite on the anode side. 

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