LITHIUM-ION: ANATOMY OF A CELL
Adding one improvement after another in the last several years, lithium-ion batteries are now highly sought after by electric vehicle makers. The batteries actually consist of hundreds of “cells” (7,000 for the latest Tesla model, for example), each of which has three components. The cathode is an aluminum plate to which active metal particles bind. The particles capture the lithium ions when the vehicle is operating. The anode is a copper plate to which graphite particles bind, capturing the lithium ions when the battery is being charged. The two electrodes are separated by a porous plastic composite (the “separator”) bathed in electrolytes. The liquid solvent contains lithium salts whose ions migrate between the cathode and anode, as the battery’s charging/discharging cycles alternate. Meanwhile, the electrons take the outside road.
ARE LITHIUM-SULFUR AND SOLID-STATE BATTERIES SOLUTIONS OF THE FUTURE?
Although the current market for electric powertrains is overwhelmingly dominated by lithium-ion batteries, other technologies may emerge in the medium term. One example may be lithium-sulfur batteries, now used in drones and avionics because of their light weight. “Arkema is partnering with the specialist Oxis on R&D to improve their performance for the transportation market,” says Dominique Plée, Scientific Director Batteries. We are also taking a close interest in solid-state batteries, considered by some to be the real technology of the future. In these batteries, the liquid electrolyte is replaced by a ceramic or polymer conductive plate. It would give vehicles unparalleled range, while reducing charging times to a few minutes. It would be a truly disruptive innovation, and certain specific Arkema polymers may well play a key role in it.
R&D AND PRODUCTION: A PROACTIVE STRATEGY
A world leader in PVDF to protect separators, Arkema is also the top producer in China of the fluoropolymers used in electrodes. “We doubled the volume of Kynar® materials produced for both applications between 2014 and 2018, and predict strong growth in the next five years,” says Thomas Fine, Global Market Manager Batteries, Technical Polymers. A proactive industrial strategy has given us very solid positions. “We’re the only global producer to have PVDF production capacity on the three continents where market growth is now happening, with our Changshu plant in China, our Calvert City facility in Kentucky and the Pierre-Bénite site in France,” points out Thomas Fine. Arkema stays ahead of OEM expectations through a non-stop, dedicated R&D effort. In addition to our battery center of excellence in King of Prussia, Pennsylvania, we work closely with battery makers at our technical centers in China, Japan and South Korea — the three countries in which global production of batteries and electric vehicles is now concentrated. Arkema is also the only PVDF producer to have developed processes for making “green” PVDF grades — that is, using aqueous (solvent-free) methods — for membranes and electrodes.
