Elemental lithium electrodes

The interest in ever-higher energy content has caused the development of cells with relatively high voltages to receive much attention in the lithium battery research community in recent years. This has led to the exploration of a number of positive electrode materials that operate at potentials of about 4 V, or even more, positive of the potential of elemental lithium. 

This is a common problem when using elemental lithium negative electrodes in contact with electrolytes containing organic cationic groups, regardless of whether the electrolyte is an organic liquid or a polymer [4]. 

Fig. 5b. It has the typical golden color of LiC. This means that the additive has decomposed dnring the eqnihbration cycles and has deposited at the active sites of graphite, preventing the formation of metallic lithium. We believe that electrolyte additives improve the performance of the graphite electrodes by changing the kinetics of elemental lithium deposition. Because the electrolyte additives make the usage of highly crystalline graphite anodes possible and at the same time suppress the coexistence of elemental Li along with the hthiated graphite, they are considered to be a key material in the LIB industry.

The technicians have always been well aware of the problems not only in finding a suitable positive electrode, but also in dealing with this available and therefore not-too-precious element. Lithium reacts with humidity, especially with water, and has its melting point at 180°C. Apart from this, the fact that perchlorates and hydrides of hthium are poisonous and must be coped with. 

The highest voltages are obtained by the use of elemental lithium in the negative electrode. The use of negative electrode reactants with lithium activities of less than unity results in electrodes with more positive potentials, thus reducing the cell voltage. 

Small nodules or roughness elements on electrodes typically form a sharp tip with small radius of curvature, causing the (primary) current density at the tip to become very high. As a consequence, these sharp tips tend to propagate very rapidly, restricted only by the kinetics limitations at the tip. Consequently, electrodes with very reversible kinetics, e.g., lithium, silver, lead, and zinc, tend to evolve needles and dendritic growth quite readily, while less reversible metals, e.g., nickel and iron, do not. 

Lead Telluride. Lead teUuride [1314-91 -6] PbTe, forms white cubic crystals, mol wt 334.79, sp gr 8.16, and has a hardness of 3 on the Mohs scale. It is very slightly soluble in water, melts at 917°C, and is prepared by melting lead and tellurium together. Lead teUuride has semiconductive and photoconductive properties. It is used in pyrometry, in heat-sensing instmments such as bolometers and infrared spectroscopes (see Infrared technology AND RAMAN SPECTROSCOPY), and in thermoelectric elements to convert heat directly to electricity (33,34,83). Lead teUuride is also used in catalysts for oxygen reduction in fuel ceUs (qv) (84), as cathodes in primary batteries with lithium anodes (85), in electrical contacts for vacuum switches (86), in lead-ion selective electrodes (87), in tunable lasers (qv) (88), and in thermistors (89). 

Comparison of the Daniell element, the nickel/cadmium accumulator, and, the lithium/manganese dioxide primary cell, as examples, shows the influence of the electrode materials on different cell parameters (Table 1). 

Table 8 shows results obtained from the application of various bulk and surface analysis methods to lithium metal at rest or after cyclization experiments, as well as at inert and carbon electrodes after cathodic polarization. The analytical methods include elemental analysis, X-ray photoelectron spectroscopy (XPS or ESCA), energy-dispersive analysis of X-rays (X-ray mi-... 

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