Electric car batteries could soon get a second lease on life

As climate concerns increase, electric vehicles are growing in popularity. In Switzerland, some 5.5% of passenger cars have a battery, and more than half of all new registrations in Q4 2021 were for electric or hybrid cars, according to the Swiss Federal Office of Energy. But what will happen to these vehicles’ lithium-ion batteries once the cars reach the end of their useful lives? “Even when the batteries are no longer suitable for electric vehicles, they still have 70%–80% of their capacity left,” says Mario Paolone, a professor at EPFL’s Distributed Electrical Systems Laboratory (DESL).

The CircuBAT initiative, which officially kicked off today, aims to turn the production, use, and recycling of electric-vehicle lithium-ion batteries into a closed-loop process. The project will run for four years and be carried out by a consortium of seven Swiss research institutions and 24 companies, with the goal of making batteries last longer by optimizing each stage of their lifecycle. The research will focus on three areas: extending a battery’s lifespan, finding them a second life, and recovering and recycling materials.

DESL will be involved on the topic of second-life battery applications of the project. One avenue that the lab’s engineers will explore is using the batteries to store power for regulating grid frequency and other parameters. “We’ll investigate the best ways to implement recycled batteries in power grids,” says Paolone. “We’ll take into account the state of the battery when it starts its second life, as well as how it ages as it’s used.” The engineers will test second-life batteries (supplied by other project members) on DESL’s full-scale microgrid, under real-world yet controlled conditions.

Aging rather than dying

Based on the results of their tests, the DESL team will develop a model for characterizing the batteries’ aging process. Their model could then be applied to any battery, regardless of how it was treated during its first life. “A battery is characterized by its energy capacity – i.e., how much energy it can store at different charge and discharge rates – and by the power at which it can be charged and discharged,” explains Paolone. “These macroscopic characteristics change as a battery age and are affected by its operating cycle. Our goal is to model precisely how these characteristics shift over time, so they can be controlled effectively during the batteries’ first and, crucially, second life.” The engineers’ model should help operators make optimal use of batteries in their second life.

Ultimately, the DESL team hopes to develop a method for certifying batteries for second-life applications, attesting to the battery’s capacity both at the beginning of its second life and over several years of use. The later a lithium-ion battery is recycled, the smaller its carbon footprint. And reducing the carbon footprint is one of the key aims of CircuBAT: “Our goal is to minimize the overall environmental impact of electric vehicles. That will include expanding batteries’ storage capacity in order to support the energy transition and developing designs that require fewer resources,” says Andrea Vezzini, who heads the CircuBAT project team at Bern University of Applied Sciences.