Positive/Negative button

Coin and Button Cell Commercial Systems. Initial commercialization of rechargeable lithium technology has been through the introduction of coin or button cells. The eadiest of these systems was the Li—C system commercialized by Matsushita Electric Industries (MEI) in 1985 (26,27). The negative electrode consists of a lithium alloy and the positive electrode consists of activated carbon [7440-44-0J, carbon black, and binder. The discharge curve is not flat, but rather slopes from about 3 V to 1.5 V in a manner similar to a capacitor. Use of lithium alloy circumvents problems with cycle life, dendrite formation, and safety. However, the system suffers from generally low energy density. 

Switching to lithium-alloy negative electrodes, some voltage loss must be noted. LiAl has Uu = -1-385 mV, Li4.5Pb has Uu = 388 mV. Entries 18-20 in Table 10(b) represent three examples of rechargeable cells, which have been, at least temporarily, commercialized. The first (No. 18) is due to a lithium alloy/carbon black battery conunercialized by the Matsushita Co. [248]. The lithium alloy components are Pb -I- Cd -I- Bi -h Sn (Wood s alloy). Button cells in the range 0.3 to 2.5 mAh were offered. The electrolyte was LiC104 in an unknown solvent. The practical energy densities, 2Wh/kg, were rather low. The c.b. positive electrode acts as a double... 

Figure 10.15 Construction of a nickel/cadmium sintered plate button cell Key 1, positive cup 2, positive connection 3, insulating ring 4, positive plate 5, separator 6, negative plate 7, negative connection 8, spring 9, negative cup. Diagram supplied by SAFT Ltd,...

Tbe constraction of the Li/CuO button-type battery shown in Fig. 14.87a is similar to other conventional and lithium/solid-cathode cells. Copper oxide forms the positive electrode and lithium the negative. The electrolyte consists of lithium perchlorate in an organic solvent (dioxolane). 

The constraction of a tubular or pocket plate nickel-iron cell is shown in Fig. 25.2. The active materials are filled in nickel-plate perforated steel tubes or pockets. The tubes are fastened into plates of desired dimensions and assembled into cells by interleaving the positive and negative plates. The container is fabricated from nickel-plated sheet steel. The cells may be assembled into batteries in molded nylon cases or mounted into wooden traps. The steel cases may be coated with plastic or mbber for insulation or spaced by insulating buttons. 

Commonly used button cells use lithium or zinc as the negative pole and iodine, manganese(IV) oxide or silver oxide as the positive pole. 

The SAFT range consists of button and cylindrical types and the VR series. The button cells have very thin sintered positive and negative plates with a porous separator enelosed by two nickel-plated steel cups. Capacities are up to SOOtnAh at 1.2 V for a size approximately 35 mm diameter x 10 mm thick with a weight of lOOg, Plastics-sleeved packs of button cells are available eonnected in series to give up to 12 V. Similar metal-clad packs are also available. 

---