The cost of the rechargeable lithium-ion batteries used for phones, laptops, and cars has fallen significantly over the last three decades, and has been a major driver of the rapid growth of those technologies. However, attempts to quantify that cost decline has produced ambiguous and conflicting results that have hampered attempts to project the technology’s future or devise useful policies and research priorities.
Now, MIT researchers have carried out an exhaustive analysis of the studies that have looked at the decline in the prices these batteries. The new study looks back over three decades, including analyzing the original underlying datasets and documents whenever possible, to arrive at a clear picture of the technology’s trajectory. An open-access paper on the work is published in the journal Energy and Environmental Science.
Lithium-ion cell prices. Time series and single-year records of lithium-ion cell prices for cylindrical (blue), prismatic (green), pouch (purple), and all types (orange) of cells, as well as representative price series for cylindrical (blue, bold, dashed) and all types (orange, bold, dashed) of cells. Records that did not specify cell type are included with series representing all types of cells. Series specifically describing cylindrical cells have annual decrease ratios between 0.048 and 0.22 while those describing all types of cells have ratios that span 0.11 to 0.23. The representative series of cylindrical cell prices has an annual decrease ratio of 0.14 (for 1991 through 2016) while that for all types of cells has a ratio of 0.13 (for 1991 through 2018). Ziegler and Trancik
Lithium-ion technologies are increasingly employed to electrify transportation and provide stationary energy storage for electrical grids, and as such their development has garnered much attention. However, their deployment is still relatively limited, and their broader adoption will depend on their potential for cost reduction and performance improvement. Understanding this potential can inform critical climate change mitigation strategies, including public policies and technology development efforts. However, many existing estimates of past cost decline, which often serve as starting points for forecasting models, rely on limited data series and measures of technological progress.
Here we systematically collect, harmonize, and combine various data series of price, market size, research and development, and performance of lithium-ion technologies. We then develop representative series for these measures, while separating cylindrical cells from all types of cells.
For both, we find that the real price of lithium-ion cells, scaled by their energy capacity, has declined by about 97% since their commercial introduction in 1991. We estimate that between 1992 and 2016, real price per energy capacity declined 13% per year for both all types of cells and cylindrical cells, and upon a doubling of cumulative market size, decreased 20% for all types of cells and 24% for cylindrical cells.
We also consider additional performance characteristics including energy density and specific energy. When energy density is incorporated into the definition of service provided by a lithium-ion battery, estimated technological improvement rates increase considerably. The annual decline in real price per service increases from 13 to 17% for both all types of cells and cylindrical cells while learning rates increase from 20 to 27% for all cell shapes and 24 to 31% for cylindrical cells. These increases suggest that previously reported improvement rates might underestimate the rate of lithium-ion technologies' change.
Moreover, our improvement rate estimates suggest the degree to which lithium-ion technologies’ price decline might have been limited by performance requirements other than cost per energy capacity. These rates also suggest that battery technologies developed for stationary applications, where restrictions on volume and mass are relaxed, might achieve faster cost declines, though engineering-based mechanistic cost modeling is required to further characterize this potential. The methods employed to collect these data and estimate improvement rates are designed to serve as a blueprint for how to work with sparse data when making consequential measurements of technological change.—Ziegler and Trancik
The work was supported by the Alfred P. Sloan Foundation.
Micah S. Ziegler and Jessika E. Trancik (2021) “Re-examining rates of lithium-ion battery technology improvement and cost decline” Energy Environ. Sci., doi: 10.1039/D0EE02681F