High Temperature Lithium Alloy Cells With Improved Low Temperature Performance

Abstract

Lithium-thionyl chloride cells are widely used in downhole applications where the temperatures exceed 100°C. These cells cannot be used above the melting point of lithium, 180°C, but modified oxyhalide cells are available that use higher-melting lithium alloy anodes that allow safe operation at temperatures as high as 200°C. However, the higher temperature capability comes at the cost of low temperature performance; the alloy cells typically show very poor rate capability below 50°C. The low temperature rate limitations can be particularly disadvantageous in cases where a tool is started up at the surface, where the ambient temperatures are cooler, before it is placed into operation downhole. Here we present test results defining and characterizing the capabilities and limitations of various types of lithium alloy cells at lower temperatures, as well as discharge results at higher temperatures for new cell types that have been designed for improved rate capability at both lower and higher temperatures.