FCL8

Any battery consists of an electrochemically reactive couple separated by an ion-transport medium, or electrolyte. In most familiar batteries the electrolyte is a liquid. However, the availability of solids capable of being fabricated into electronically insulating elements with fairly low overall ionic resistance has stimulated the development of solid-electrolyte batteries. A few of these types of batteries have become available commercially and are important power sources at normal ambient temperatures (25oC) for heart pacemakers, for preserving volatile computer memory, and for other low-power applications requiring long shelf and service lives. A chronology of various types of solid-electrolyte cells developed since 1950 is shown in Table 1. Two trends are indicated in this table. First, the low energy silver-based systems have been replaced largely by developments of high-energy lithium anode-based batteries. Second, the batteries have gone from being pellet-based devices with relatively thick electrolyte layers (on the order of a millimeter) to thin film devices with electrolyte thicknesses on the order of micrometers. This reduction in the inter-electrode distance has been necessary in order to overcome the ohmic losses due to the more resistive lithium-ion conducting electrolytes.