Metal sulfide cells, lithium

Table I. Exploratory Test Results of Lithium—Metal Sulfide Cells...

Figure 6. 25-W-hr lithium-metal sulfide cell prior...

Figure 1. Lithium-metal sulfide investigative cell...

Lithium—Aluminum/Metal Sulfide Batteries. The use of high temperature lithium cells for electric vehicle applications has been under development since the 1970s. Advances in the development of lithium alloy—metal sulfide batteries have led to the Li—Al/FeS system, where the following cell reaction occurs. 

High-performance lithium-sulfur cells are being developed for use in off-peak energy storage batteries in electric utility networks. The cells, which operate at 400°C, consist of a lithium electrode, a sulfur or sulfide electrode, and molten LiCl-KCl electrolyte. The chemistry of the lithium electrode is relatively straightforward. However, the electrochemical reactions at the sulfur electrode involve the formation of several intermediate species that are sufficiently soluble in the electrolyte to limit the lifetime and capacity of the cells. Although this effect can be decreased with soluble additives such as arsenic or selenium in the sulfur, a more promising solution appears to be the use of metal sulfides, rather than sulfur, as the active material in the positive electrode. 

The cell reaction for a bivalent metal sulfide and metallic lithium couple can be written as follows ... 

Two long-term tests have been performed with copper sulfide electrodes, one in a small investigative cell of the type shown in Figure 1, the other in a sealed 25-W-hr cell which will be described later. The starting active material in both cells was CuS. In both cases, the lithium electrodes consisted of porous metal plates impregnated with molten lithium metal. The electrolyte was the LiCl-KCl eutectic salt mixture, saturated with Li2S and maintained at 380-400°C. 

In addition to competition from lower-cost zinc-carbon cells, the AA-size alkaline cell has experienced significant competition from the more expensive rechargeable nickel-metal hydride (Ni-MH) and nickel-cadmium (Ni-Cd) cells and the lithium-iron sulfide primary cell (Li-FeS2) because of their excellent high-rate... 

Liquid Organic Electrolyte Batteries. These cells use lithium metal for the negative electrode, a liquid organic aprotic solution for the electrolyte, and transition metal compounds (oxides, sulfides, and selenides) for the positive electrode. These transition metal compounds are insertion or intercalation compounds and possess a structure into which lithium ions can be inserted or from which they can be removed during discharge and charge, respectively. 

In all primary lithium cells, the negative electrode is made of metallic lithium. Thus, different types of lithium cells differ in the positive electrode material and in the type of electrolyte. A variety of oxidant materials was offered as the active material of the positive electrode. These included different oxides, sulfides, selenides, oxysulfides, oxychlorides, and some other substances perfluorinated carbon and sulfur. However, only a small number of electrochemical systems in the cells actually reached the industrial production stage. The electrochemical systems of the cells produced industrially are given in Table 11.1. This Table also presents the values of open circuit voltage (OCV) of these cells and the theoretical values of their energy density. 

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