Put two pieces of different types of metal in a medium that allows ionic exchange and you have a battery. Don’t believe it? Just do an Internet search for “Potato Battery.” The point is that dissimilar metals create an electric potential between them and that potential can be used to generate electrical current. From such a simple thing springs a whole world of misunderstanding, misdirection, hype, and, occasionally, outright lies.
A Miracle a Month
It seems almost every month an announcement comes about a new battery that is safer, cheaper, and will last millions of miles. A breakthrough. A game-changer. The Holy Grail. Is it real? Since the early 1990s, more than 300,000 battery patents have been filed, so it certainly seems people are trying. But it’s easy to make grand claims without providing any real evidence.
It’s About the Lithium
Lithium-ion batteries are today’s most important batteries for cell phones and handheld devices, laptops, and electric vehicles (EVs). Lithium is a highly reactive metal and is used in the form of ions that travel between a metal oxide cathode and a carbon graphite anode. Lithium metal, which potentially could have a much higher energy density, cannot be used with liquid electrolytes (more on that later) as spikey dendritic lithium crystals form on the metal surface during charging. These crystals can grow large enough to create a short circuit between the anode and cathode, potentially creating a fire hazard.
In a lithium-ion battery, a metal oxide cathode is used instead of lithium metal and it is the key to commercial lithium-ion battery performance. Just about every other element on the Periodic Table has been tried in combinations of metals and metal oxides for this application. Sodium, fluorine, magnesium, potassium, calcium, zinc, and aluminum have all had their turn. Currently, iron with phosphate (LFP), or nickel, with cobalt and either manganese (NCM) or aluminum (NCA), are the most commonly used cathode materials in commercial batteries for EVs.
Besides the various mixtures of either nickel or iron, other possibilities include lithium-air (using oxygen from the air—tiny hearing aid batteries are already made this way), and lithium-sulfur (an experimental version of which was used to set altitude and endurance records with an unmanned solar-powered aircraft called Zephyr in 2008).
A Million Miles!
Earlier this year, Tesla hinted that it will have a battery that will last more than a million miles, at a significant lower cost than the current battery technology that it shares with Panasonic. Commercial lithium-ion batteries are expected to last 100,000 to 200,000 miles. The new battery, a result of a collaboration with the Chinese battery giant Contemporary Amperex Technology (CATL), eliminates expensive cobalt from its chemistry, moving the purchase price of an EV closer to parity with its gasoline-engine counterpart.
Another Million Miles!
In March, General Motors (GM) announced its Ultium advanced battery system. Created with its Korean battery maker LG Chem, the claim is also for a million-mile lifetime. A million miles seems a popular theme for battery and EV companies. The batteries will be produced at a new joint-venture battery plant at Lordstown, Ohio, and use a nickel, cobalt, manganese, aluminum chemistry—the aluminum addition allows a reduction in the amount of cobalt, reducing costs.
IBM Research’s Battery Lab, at the end of 2019 announced a new battery design that uses “a cobalt and nickel-free cathode material, as well as a safe liquid electrolyte with a high flash point.” IBM claims, “The unique combination of the cathode and electrolyte demonstrated an ability to suppress lithium metal dendrites during charging, thereby reducing flammability.” The company also claimed it takes less than five minutes to reach an 80 percent state of charge for its wonderous new battery. No mention of a million miles. The company says the battery will be made from materials derived from seawater and that it is made up of “three new and different proprietary materials, which have never before been recorded as being combined in a battery.”
Low cost, high power, and energy density are also claimed for this battery breakthrough.
Is the IBM battery a breakthrough? How would we know? The company media release is long on hype and promise but provides little or no substantive information about the chemistry of the configuration of the battery. Shouldn’t we expect more from “Big Blue”?
Another way to increase lithium-ion battery performance and safety is through the use of a solid electrolyte. Present-day lithium-ion batteries use an organic liquid electrolyte (see above) that provides mobility of lithium ions between the anode (negative) and cathode (positive) electrodes. That organic solvent is flammable, however, and thus can be a fire hazard should the battery cell become damaged or if it overheats or is overcharged.
A ceramic or polymer solid electrolyte can be substituted for the organic solvent, which would help make the battery safer. According to an Oak Ridge National Laboratory study, “The key to improving density lies in developing a powerful thin solid electrolyte.” Also, when lithium metal foil is used to replace the current graphite anode, the combination could increase battery performance and storage capacity by 2-3 times.
Toyota has announced that it will have solid-state electrolyte batteries on the market in it’s EVs by 2025. The company had intended to showcase its new lithium-sulfur solid electrolyte technology at the 2020 Tokyo Olympics, an event that has been postponed to 2021. The claim is that the new batteries can recharge fully in less than 15 minutes and will last more than 30 years.