Lowering the Bar on Battery Cost

Abstract

In this Backstory, Yet-Ming Chiang and colleagues explain how their cost-focused approach led to the discovery of an affordable battery technology based on readily available materials. The ProblemCan batteries ever reach the cost of pumped hydroelectric storage, which today constitutes more than 99% of the deployed energy storage in the world, but has limited growth potential due to its geographical and environmental constraints? This was the overarching question that motivated our project team, which had a 5-year mandate from the U.S. Department of Energy's Joint Center for Energy Storage Research (JCESR) to answer such challenges. If achieved, such storage could scale in a way that allows intermittent renewable generation (wind and solar) to truly compete with fossil fuel-based electricity generation. Of JCESR's audacious goals captured by their motto ''5-5-5'' (meaning 5 times reduction in cost, 5 times increase in energy density, accomplished in 5 years), for grid storage the authors considered the cost challenge to be the most important by far, since almost any electrochemical approach would have a hundred times or higher energy density compared to pumped hydro. Energy density was mainly important insofar as it enabled more compact systems of lower cost. Thus, we obsessed about the cost-per-stored-energy metric, US$/kWh, although other attributes such as lifetime, safety, and toxicity of components would naturally also be important.

Energy storage emerging: A perspective from the Joint Center for Energy Storage Research

“…In a separate grid effort, JCESR identified the emerging need for inexpensive long-duration storage (16,18) and sought to address it with an entirely new kind of flow battery, an air-breathing aqueous sulfur battery (48,49). Targeting storage needs with discharge times of days to weeks to firm electricity delivery in grids with high fractions of variable wind and solar, this battery employs exceptionally low cost materials: sulfur, an abundant byproduct of oil refining, water, and oxygen drawn from air.…”

On the Reversibility and Fragility of Sodium Metal Electrodes

“…[1] A rechargeable battery technology which replaced the graphitic carbon host material at the anode with an electrochemically active metal such Li or sodium (Na) could produce substantial increases in storage capacity of the battery anode (from 360 mAh g -1 to 1166 mAh/g (for Na) or 3860 mAh g -1 (for Li)), lowering anode material costs. [2] Such rechargeable metal anode batteries would also enable use of commensurate high-energy cathode materials, such as sulfur (S 8 ) [3][4][5] and oxygen/carbon dioxide (O 2 /CO 2 ) mixtures [6][7][8][9][10][11][12][13] , among others. Use of rechargeable batteries in which an energy-dense metallic anode is paired with an energy-dense cathode offer potential for significant improvements in specific energy on either a volumetric or mass basis (e.g.…”

Thermal energy grid storage using multi-junction photovoltaics

“…There is significant concern nonetheless, that even this lower asymptote for Li-ion is still not cheap enough to enable the eventual 100% penetration of renewables needed to truly mitigate climate change. In this respect, alternative solutions to the storage problem are needed, and it is likely that costs closer to $50/kWh-e and below 13,14 will be needed to eventually realize 100% penetration and full abatement of CO2 emissions from the stationary power sector. This low cost requirement arises from the fact that a levelized cost of storage (LCOS) below the $0.06/kWh average electricity price 15 and 10 or more hours 16 of storage are needed to reliably and cost-effectively supply the grid.…”