Life cycle assessment on calcium zincate production methods for rechargeable batteries.

The world's energy transition from fossil to renewable energy is unthinkable without further research in energy storage. Decreasing the environmental impacts from the production of energy storage technologies is essential for achieving a green energy transition. Calcium Zincate (CAZN) is used as active material in rechargeable zinc-based batteries (and other products, such as heterogeneous catalysts for biodiesel or antifungal products). They present a low-cost, safer, alternative to Lithium based batteries and are targeted as replacement solutions for lead-acid batteries. We propose a novelty in the synthesis of CAZN, the hydro-micro-mechanical process (HMMS). The residence time of this new route is about 20 times lower than the traditional processes, so its production needs less infrastructure and can deliver quicker at an industrial scale. In addition, laboratory tests indicate that HMMS CAZN has more reaction surface area and the activation of the battery is 1.77 times faster. Using the life cycle assessment (LCA) method, we compare this new process with the current best option, hydro-thermal synthesis (HTS). The cradle-to-gate results per kg of CAZN already indicates that HMMS is an environmentally better alternative for all indicators; especially when considering the normalization of the results with the residence time and the surface area, HMMS delivers better results, with improvements of 97 % in global warming, for instance. With this, we demonstrate that, outside of the cradle-to-gate, variables that make the final products better service units or give more function should be considered as valuable additional information when deciding among alternatives. This also highlights the importance of life cycle thinking when working with chemical processes and substances. In the sensitivity analysis, we developed 7 scenarios related to the energy demand of the processes, and we incorporated the projection in the European electricity mix for 2030 and 2050.