How does an EV battery actually work?
How does an EV battery actually work?
Lithium-ion batteries, also found in smartphones, power the vast majority of electric vehicles. Lithium is very reactive and batteries made with it can hold high voltage and exceptional charge, making it an efficient and dense form of energy storage. These batteries are expected to remain dominant in electric vehicles for the foreseeable future thanks to falling costs and improved performance.
Right now, electric car batteries typically weigh around 1,000 pounds, cost around $15,000 to manufacture, and have enough power to run a typical home for a few days. If their carrying capacity degrades over time, they should last 10-20 years.
Each battery is a dense collection of hundreds, if not thousands, of slightly pasty lithium-ion electrochemical cells, usually shaped like cylinders or pouches. Each cell consists of a positive cathode (which typically contains metal oxides made from nickel, manganese, and cobalt); a graphite-based negative anode; and a liquid solution in the middle, called the electrolyte.
This is where the reactivity of lithium comes in; its loose outer electron can easily be separated, leaving a lithium ion (the atom without its outer electron). The cell basically works by swinging these ions and electrons back and forth.
During the charging cycle, an electric current introduced via an external source separates the electrons from the lithium atoms in the cathode. Electrons flow around an outer circuit to the anode – which is usually made of graphite, a cheap, energy-dense and durable material that excels at storing energy – while ionized lithium atoms flow to the anode through the electrolyte and are reunited with their electrons. During discharge cycles, the process is reversed. The lithium atoms in the anode are again separated from their electrons; the ions pass through the electrolyte; and the electrons flow through the outer circuit, which powers the motor.
The expansion of electric vehicles has created a voracious demand for the minerals needed to manufacture batteries. The price of lithium carbonate, the compound from which lithium is extracted, remained relatively stable between 2010 and 2020, but increased almost tenfold between 2020 and 2022, stimulating new investments around the world. More than a dozen battery factories and numerous potential mining projects are in development in the United States alone.
But the quest for raw materials comes with huge environmental, political and social costs.
The vast majority of cobalt, a common cathode component, comes from the Democratic Republic of Congo, notorious for child labor and forced labor. Much of America’s raw material supply is on tribal lands. Chile, a major lithium producer, wants to wrest control of production from the multinationals. Meanwhile, mining companies and entrepreneurs intend to mine the seabed for minerals, which could damage a fragile and poorly understood ecosystem (Chile imposes a moratorium on such ocean mining) .
Battery developers are looking to reduce the use of rare metals and improve recycling. Startups and automakers are also racing to design and build next-generation batteries that eliminate hardware challenges and improve efficiency. A new generation of lithium-ion batteries has already phased out the use of cobalt, for example. Scientists also tested sodium-sulfur batteries, made from much cheaper and more abundant raw materials, and solid-state batteries, which, as their name suggests, replace the liquid electrolyte with compounds solid. They may offer a lighter, more stable and faster alternative.
Forecasts suggest that electric vehicles will reach price parity with cars based on internal combustion engines in just a few years, accelerating adoption. And experts predict rapid expansion, consolidation and experimentation in battery manufacturing as countries and companies vie for position among the dozen or so dominant players in the industry. The tiny journeys that ions take between the cathodes and anodes of battery cells are likely to become one of the most important journeys of the next decade.