Why are they so expensive?
The short answer is: they’re not! Over the lifetime of the battery, a Dragonfly Energy Li-ion battery pack is far cheaper than the lead acid alternative, because the cycle life more than compensates for the upfront premium. Nevertheless, it is fair to address what contributes to the upfront cost of the pack. Although there is some cost associated with the research and design that goes into the pack structure, battery management system, and relevant contacts and connections, most of the cost comes from the manufacture of the cells themselves. Unlike lead acid batteries, the performance of a Li-ion cell depends on nano-scale phenomena, including diffusion of Lithium ions through nano-pores and into nanoparticles. Thus, much of the cost comes from production of these nanostructures, which includes production of the nanopowder electrodes (in our case, the LiFePO4 cathode and the graphite anode), and coating of the nanopowder films onto metal foil substrates. Most notably, this coating entails forming a slurry from the nanopowders, a binder, and a solvent; and then coating the slurry and evaporation the solvent. This process requires very large scale mixers, coating machines, heaters, dryers, and vacuum driers. This complex and batch production process ensures that cell factories need to go to large scale production with large equipment in order to benefit from economies of scale. It is fair to note that these costs have come down fairly significantly over the last decade, making Li-ion an economically attractive alternative to lead acid for deep cycle applications.