Lithium energy density

High energy density batteries with long shelf life, developed originally for military use, are based on lithium and thionyl chloride. These batteries are used ia backup or standby power sources for computer, missile, and telephone systems (191,192). 

Fig. 25. Lithium—sulfur dioxide and lithium —tbionyl chloride high rate batteries profile with (a) power density vs energy density, and (b) specific power vs...

Lithium—Thionyl Chloride Cells. Lidiium—thionyi chloride cells have very high energy density. One of the main reasons is the nature of the ceU reaction. 

Table 1. Theoretical Energy Densities for Rechargeable Lithium Systems...

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. 

Because of lithium s low density and high standard potential difference (good oxidation reduction characteristics), cells using lithium at the anode have a very high energy density relative to lead, nickel and even zinc. Its high cost limits use to the more sophisticated and expensive electronic equipment. 

Cylindrical batteries can be classified into two basic types one with a spiral structure, and one with an inside-out structure. The former consists of a thin, wound cathode and the lithium anode with a separator between them. The latter is constructed by pressing the cathode mixture into a high-density cylindrical form. Batteries with the spiral construction are suitable for high-rate drain, and those with the inside-out construction are suitable for high energy density. 

Lithium-vanadium oxide rechargeable batteries were developed as memory backup power sources with high reliability and high energy density. 

The batteries feature a high operating voltage of 2.0-3.3 V. The energy density of SL621 (diameter 6.8 mm, height 2.1 mm) is 6.5 Whl"1. It is applicable to various types of small, thin equipment requiring backup for memory and clock function. Table 15 shows the specifications of lithium—polyacene batteries [58],... 

Secondary lithium-metal batteries which have a lithium-metal anode are attractive because their energy density is theoretically higher than that of lithium-ion batteries. Lithium-molybdenum disulfide batteries were the world s first secondary cylindrical lithium—metal batteries. However, the batteries were recalled in 1989 because of an overheating defect. Lithium-manganese dioxide batteries are the only secondary cylindrical lithium—metal batteries which are manufactured at present. Lithium-vanadium oxide batteries are being researched and developed. Furthermore, electrolytes, electrolyte additives and lithium surface treatments are being studied to improve safety and recharge-ability. 

Table 1. Theoretical capacities, rechargeable capacities, average operating voltages, and energy densities of secondary lithium batteries with insertion materials...

Of these requirements (1) - (4) relating to the energy density and requirements (8) and (10) associated with safety are most important behavior criteria for insertion materials for lithium-ion batteries, even in basic research. 

The mobility of lithium ions in cells based on cation intercalation reactions in clearly a crucial factor in terms of fast and/or deep discharge, energy density, and cycle number. This is especially true for polymer electrolytes. There are numerous techniques available to measure transport... 

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