Analysis and modelling of calendar ageing in second-life lithium-ion batteries from electric vehicles

The reuse of Li-ion batteries from electric vehicles is a promising alternative to recycling nowadays. However, the technical and economic viability of these second-life (SL) batteries is not yet clear. Degradation assessment plays a key role not only to analyse the impact of ageing factors in reused batteries, but also to quantify their durability. In this context, this contribution aims to analyse calendar ageing behaviour in SL cells. 16 reused Nissan Leaf modules are aged during 750 days under three temperatures and four State of Charge (SOC), covering a State of Health range from 72.2 % to 13 %. The impact of temperature and SOC as stress factors is firstly analysed, concluding that their increase accelerates ageing. Temperature rise is found to have a major impact, accelerating up to 27 times capacity fade and almost 6 times resistance increase when compared to light ageing conditions, while increasing SOC nearly doubles ageing rates. The worst ageing case is found to be the combination of 60 ◦C and 66 % of SOC. Regarding degradation trends, they are proven to be constant during all SL lifetime. This work also proposes and validates a calendar ageing model for SL cells. Accuracy of validation results show a fitting Rsq of 0.9941 in capacity fade and 0.9557 in resistance increase, thereby tracking the heterogeneous degradation of the SL cells under calendar ageing.We would like to acknowledge the support of the Spanish State Research Agency (AEI) grant PID2019-111262RB-I00/AEI/10.13039/501100011033, the European Union H2020 Project STARDUST (74094) and the Government of Navarre Ph.D. scholarship

Integration of second-life batteries in residential microgrids and fast charging stations

The potential of batteries from electric vehicles to be given a second life in stationary applications could be starting to become a reality in few years. However, the technical and economic feasibility of such second-life batteries (SLBs) is still uncertain. In this context, this paper analyses the real operation of a SLB in three scenarios: two of residential microgrids with photovoltaic generation under different strategies, and a fast charging station for electric mobility. To this end, three energy management strategies are developed, the first of which seeks to maximise the self-consumption of a typical household with photovoltaic generation; the second, in addition to maximising self-consumption, presents a night-time charge and peak shaving of the contract power from the grid; and the last refers to an urban bus charging station in which the aim is to reduce the contract power from the grid. Experimental validation of SLB during more than three weeks of operation in each of the scenarios have proved the technical viability of these batteries in the applications analysed.Spanish State Research Agency (AEI) grant PID2019-111262RB-I00/AEI/10.13039/501100011033; European Union H2020 Project STARDUST (74094). E. Braco was supported by a Predoctoral Contract of the Government of Navarra