Comparative life cycle assessment of lithium-ion battery chemistries for residential storage

Abstract

Residential storage deployment is expected to grow dramatically over the coming decade. Several lithium-ion chemistries are employed, but the relative environmental impacts of manufacturing them is poorly understood. This study presents a cradle-to-gate life cycle assessment to quantify the environmental impact of five prominent lithium-ion chemistries, based on the specifications of 73 commercially-available battery modules used for residential applications. Three impact categories (global warming potential, cumulative energy demand and mineral resource scarcity) are analysed across two functional units (storage capacity and lifetime energy delivered). Most chemistries have embodied carbon footprints of around 200 kg CO2e per kWh of useable storage capacity, which corresponds to 43–84 g CO2e per kWh of lifetime energy delivered with daily cycling operation. Energy delivered on energy invested is also calculated at values of 2–4, which falls to 0.54–0.66 with the energy for charging included (cf. a round-trip efficiency of 82–89%). Environmental impact depends more on cycling frequency than chemistry choice, and none of the battery chemistries convincingly outperforms the others. Cells only constitute a third to a half of the environmental impact, which is comparable to the inverter. Routes to making residential lithium-ion battery systems more environmentally benign include reducing the reliance on cobalt, nickel and copper, increasing the specific useable energy, developing comprehensive recycling initiatives, and maximising the utilisation (cycle frequency) once in operation.