Life Cycle Assessment of Sodium-Nickel-Chloride Batteries

Abstract

Battery storage systems are a crucial factor for the decarbonization of energy systems, to balance the fluctuating energy generation of renewable energy sources. However, some battery types have disadvantages regarding their environmental impact, due to their material composition. Recently, sodium-nickelchloride (NaNiCl 2 ) batteries are considered for a wider range of application, especially for off-grid storage applications.NaNiCl 2 batteries offer several advantages: Due to the ceramic electrolyte the battery has no electrochemical self-discharge. The batteries have a high tolerance toward overcharging and deep discharging. The materials are not as expensive and rare as materials for alternative battery types. Manufacturers state that both discharge and charge operations are nearly independent of outside temperature. Furthermore, the batteries are expected to have a lifetime of more than 15 years or 4,500 charging cycles. However, when in stand-by, the battery still needs a stable temperature between 250 °C and 320 °C, to keep the electrodes in a molten state. This is leading to a certain self-discharge, limiting the feasible applications of the battery.Facing these benefits and downsides of NaNiCl 2 batteries, this paper aims to analyse their ecological impacts based on a Life Cycle Assessment using the example of greenhouse gas (GHG) emissions. It addresses the research question whether NaNiCl 2 batteries offer advantages compared to alternative battery types, such as lithium-ion and lead-acid. The assessment is based on the analysis of a Bill-of-Materials and implemented for the use-case of a solar mini grid in Tema, Ghana. It considers two scenarios each regarding end-of-life (EoL) and battery lifetime. Depending on the scenario, the GHG emissions of the NaNiCl 2 battery amount to 9.1 -22.7 g CO 2 eq per kWh discharged and consumed, compared to 31.3 g CO 2 eq for lithium-ion and 122.1 g CO 2 eq for lead-acid batteries. The GHG emissions of the whole mini grid are decreased by 32%, if NaNiCl 2 batteries are implemented, compared to a mini grid configuration based on a mix of NaNiCl 2 , lead-acid and lithium-ion batteries.