Battery types, metallic negatives

Although one of the most common storage batteries is called the nickel/cadmium system ( NiCad ), correctly written (-)Cd/KOH/NiO(OH)(+), cadmium is not usually applied as a metal to form a battery anode. The same can be said with regard to the silver/cadmium [(-) Cd / KOH / AgO (+)] and the MerCad battery [(-)Cd/KOH/HgO(+)]. The metallic negative in these cases may be formed starting with cadmium hydroxide, incorporated in the pore system of a sintered nickel plate or pressed upon a nickel-plated steel current collector (pocket plates), which is subsequently converted to cadmium metal by electrochemical reduction inside the cell (type AB2C2). This operation is done by the customers when they start the application of these (storage)... 

While the development of primary cells with a lithium anode has been crowned by relatively fast success and such cells have filled their secure rank as power sources for portable devices for public and special purposes, the history of development of lithium rechargeable batteries was full of drama. Generally, the chemistry of secondary batteries in aprotic electrolytes is very close to the chemistry of primary ones. The same processes occur under discharge in both types of batteries anodic dissolution of lithium on the negative electrode and cathodic lithium insertion into the crystalline lattice of the positive electrode material. Electrode processes must occur in the reverse direction under charge of the secondary battery with a negative electrode of metallic lithium. Already at the end of the 1970s, positive electrode materials were found, on which cathodic insertion and anodic extraction of lithium occur practically reversibly. Examples of such compounds are titanium and molybdenum disulfides. 

Most proposed battery types employed lithium-negative electrodes. In such batteries the electrolyte must contain a lithium salt and the electrode processes on the lithium electrode consist of simple transfer of the lithium ions from the crystal lattice of the metal to the melt and back. 

Lithium-polymer batteries (LPBs) use intercalated carbon for the negative electrode, a polymer electrolyte, and metallic lithium that is deposited as a thin film as the negative electrode. This battery type is under development but not yet introduced to the market for electric vehicles. 

The first use of lithium alloys as negative electrodes in commercial batteries to operate at ambient temperatures was the employment of Wood s metal alloys in lithium-conducting button-type cells by Matsushita in Japan. Development work on the use of these alloys started in 1983 [10], and they became commercially available somewhat later. 

Those rare-earth AB -type hydrides were quickly utilized in rechargeable nickel metal hydride batteries where electrochemical hydrogen charging and discharging take place at ambient temperature. Such electrochemical hydrogen storage is reversible, when the negative hydride electrode (anode) is combined with the positive Ni electrode (cathode) in the battery cell.. 

A nickel-metal hydride battery (Ni-MH), which is a type of rechargeable battery comparable to a nickel-cadmium (Ni-Cd) battery, uses a hydrogen-absorbing alloy for the negative electrode... 

The application of A-type GIC materials in rechargeable batteries has frequently been investigated, namely in metal/graphite cells in concentrated sulfuric acid by Fujii (Me = Pd) [153,154] and in acids of medium concentration by Beck and Krohn (Me = Pb or Zn) [155-157]. The latter electrolytes have an improved compatibility with the negative metal electrode. Metal-free accumulators with GIC as a positive electrode were built with anthraquinone in aqueous acids [80] and with polypyrrole in aprotic electrolytes [58,158,159]. General discussions of the potentialities of graphite-type active materials in rechargeable batteries have been published by Besenhard and Fritz [160] and Beck et al. [5-10]. At the end of this review (Section 9) the discussion relevant to batteries will be summarized. 

The best-known example of a metal-air battery is the miniature button-type zinc-air battery widely used in hearing aids and other electronic devices of small size. Metallic zinc is the negative electrode in these batteries (usually in the form of highly disperse powder). When current is drawn, the zinc dissolves anodically in a concentrated alkaline solution according to the equation ... 

When two dissimilar metals are in electrical contact with one another and both are contacting the same electrolyte, one of the metals will preferentially corrode, a process known as galvanic corrosion (also the principle by which certain types of batteries function). The more active metal will corrode, which is the metal having the more negative open-drcuit (or corrosion) potential, when immersed all by itself in the electrolyte the more noble metal (having the more positive open-circuit potential) will support the reduction reactions. The more active metal is, therefore, the anode and corrodes faster than it would all by itself, whereas the other more noble metal becomes the cathode and corrodes slower than it would alone (or maybe not at all). The electrolyte resistance, important in all corrosion processes, may play a particularly influential role in this type of corrosion process. 

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