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Lithium batteries

Today, energy harvesting equipment typically employs alkaline rechargeable batteries in button or cylindrical form. We have noted that there is a big mismatch between the need for life of ten years or more and most battery guarantees of far less. The environmental credentials of energy harvesting are tarnished by materials in these batteries that are either rare, like silver, or toxic, like lithium and various electrolytes. Here we look to the future.
Wireless Sensor Networks often employ primary batteries some of which, such as lithium iodine and lithium thionylchloride are claimed to last 20 years with appropriate duty cycles. This is instead of EH, which can rarely demonstrate 20 year life as yet, though it is often claimed. However, USN increasingly employs EH to recharge secondary batteries. Most other EH uses lithium rechargeable batteries. Laminar versions offer major advantages over coin cells as detailed in Appendix 3 by supplier Cymbet. Excellatron, EaglePicher, Tadiran and Varta are among the companies capitalizing on existing lithium technologies to offer micro batteries for energy harvesting applications. Leeds Lithium Power and others make these batteries reel to reel. Laminar batteries are more appropriate for many applications but the manganese dioxide zinc ones of Enfucell, Power Paper, GSI, Blue Spark and others are not rechargeable and they store only modest amounts of power with limited shelf life. They are therefore of little relevance to energy harvesting because they are usually unsuitable even as backup though they have huge potential markets elsewhere. The rechargeable versions actually in production by other companies are all lithium ion or lithium polymer, both having environmental issues though not the danger of fire and explosion all too graphically demonstrated with the larger lithium batteries in some laptop computers and electric vehicles. Infinite Power Solutions and others are now offering damage tolerant laminar lithium batteries.
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