Are Batteries Still the Best Choice for the Climate?

Batteries are at the heart of the European Union’s strategy to decarbonize its economy and energy system. However, this technological solution is embedded in a complex socioeconomic reality that forces researchers to constantly reinvent it.

This text was published to mark the appearance of an article by Prof. Jean-Marie Tarascon, holder of the Chair in Chemistry of Materials and Energy, on the cover of Nature Sustainability .

Like many economic sectors, the French automotive market has struggled over the past two years, hit hard by the COVID-19 health crisis and the semiconductor shortage. One segment, however, has managed to stand out. Sales of electric vehicles surged by about 46%, reaching a 10% market share in 2021 (France Info ). This is unprecedented. The electrification of our cars is well underway, driven by a strong commitment from the French government and the European Union. At the heart of this transformation are batteries, or accumulators, which are inexorably replacing internal combustion engines and enabling our vehicles to run on electricity. In addition to this application, batteries offer a viable solution for storing large amounts of electricity generated from renewable energy sources (notably solar and wind) and for redistributing it as needed.

Nevertheless, batteries are not a technological “Holy Grail.” They exist within a complex and ever-changing economic, social, and geopolitical context. Their use and commercialization must be accompanied by a multifaceted and holistic approach. Here are a few examples. Batteries are designed to replace gasoline engines. If these batteries are powered by coal-fired power plants, the associated indirect emissions will exceed those of a running engine. On the other hand, batteries recharged by solar or wind energy will yield a genuine environmental benefit. By way of comparison, to produce the same amount of energy, coal emits 18 times more CO2 equivalents than solar power and 75 times more than wind power (figures from the 2014 IPCC report). Deploying batteries without considering the energy mix is pointless and could even prove counterproductive. Similarly, whether used to power electric vehicles or to store renewable energy, batteries are produced using numerous metals—such as nickel, cobalt, and especially lithium—that are unevenly distributed across the globe. However, Europe possesses neither these resources on its own soil nor the industrial capacity to process and refine them. Lithium, the main component of batteries, for example, comes 86% from three countries (International Energy Agency): Australia, Chile, and China. Worse still, China alone accounts for 58% of the world’s lithium refining capacity. If China decides to halt its exports of refined lithium, Europe’s electrification strategy will be seriously called into question.

In light of these risks and in order to mitigate them, European researchers—particularly those at the Collège de France—are focusing their research on two main areas: recycling and real-time monitoring of battery health. Recycling has the advantage of changing the way we view used batteries. What was once considered “waste” becomes a potential source of metals that, once reprocessed, can be reintroduced into the production of new batteries. This is the concept of an “urban mine” [ which refers to a mass of waste from which raw materials can be extracted through physical and chemical processes ]. The technical challenge here is to improve recycling solutions, which currently remain very energy-intensive and require large amounts of chemicals. Professor Jean-Marie Tarascon, holder of the Chair in Chemistry of Materials and Energy at the Collège de France, also advocates for rethinking battery design from the outset so that they are built to be modular. This way, if a battery fails, it is no longer necessary to reprocess the entire battery, but only the damaged component.

The ability to monitor the health of batteries in real time also plays a role. Indeed, a battery whose performance no longer allows it to power an electric vehicle can still be repurposed for another use, such as storing renewable energy. This is what researchers call a “second life.” Knowing the exact health status of a battery makes it possible to optimize its reuse. More ambitiously, effective and continuous monitoring of batteries would allow for immediate intervention in the event of a problem detected within the storage system itself, through controlled and localized chemical reactions. This would drastically extend the lifespan of batteries and thus reduce their carbon footprint. While Europe has fallen far behind Asia in general—and China in particular—in terms of battery production capacity, it can still make a difference by investing in disruptive innovation and ensuring that the batteries of the future are fully “green.”