Tackling the Development of Rechargeable Calcium Batteries: The CARBAT Project

Abstract

While the cost of the state-of-the-art electrochemical energy storage technology, the Li-ion battery (LIB), has been reduced by 8% at the pack level annually during the last decade (1), it is nowreaching its fundamental limits in terms of energy density. Furthermore, the risk of limited lithium supply and associated cost increases cannot be ignored. Therefore, new sustainable battery chemistries must be developed. Calcium-based rechargeable batteries are proposed to help solving some of the Grand Challenges our modern society is facing: pollution, oil-dependency, and climate change. Batteries based on Ca have promise of leap-frog increase in energy densities and are especially attractive as Ca is the 5th most abundant element in the Earth’s crust and can indeed be used as a metallic anode with conventional wide potential window electrolytes (2,3). The CARBAT project builds on this breakthrough and its main objective is to achieve proof-of-concept for a Ca anode rechargeable battery. CARBAT combines scientific efforts of computational screening, solid-state and coordination chemistry, materials science, electrochemistry, and battery engineering, and apply these to: (i) develop cathode active materials operating at 4 V and with capacities of 200-300 mAh/g, (ii) optimize electrolyte formulations for fast Ca2+ transport (>1 mS/cm), and finally (iii) assemble a 100 mAh cell demonstrator. All developed materials and cells are validated and benchmarked vs. state-of-the-art LIB technology, both in terms of performance and sustainability indicators. (1) Nykvist, B.; Nilsson, M. Nat. Clim. Change, 2015, 5, 329. (2) Muldoon, J. Chem. Rev., 2014, 114, 11683. (3) Ponrouch, A.; Frontera, C.; Barde, F.; Palacin, M.R. Nat. Mater., 2016, 15, 169.