Why Sulfates Are Worse for EV Batteries Than They Are for Hair

Many of us fret about sulfates in shampoo and sulfites in wine, but I just learned about the awful effect of employing sulfates in battery cathode production. Apparently, the way most lithium-ion cathodes have been made for 30 years results in a colossal amount of waste. Fortunately, I learned about this problem while discovering a potential solution.

The cathode is a battery’s positive electrode, where charging energy is applied. In most of today’s lithium-ion batteries, these are made of lithium-nickel-manganese-cobalt (NMC). The way these have been made involves mining the metals, turning them into metal sulfates or salts, converting lithium carbonate to lithium hydroxide, then transporting these materials to the cathode manufacturer where they’re mixed in water. A caustic material like sodium hydroxide gets added to precipitate out a powder precursor that gets mixed with the lithium hydroxide and baked in a furnace to form grains of lithiated cathode material. A special coating is then applied in a separate process.

The process yields at least 1.8 times as much sodium sulfate waste as it does cathode material. It’s not particularly harmful to humans or the environment, but there is little real market for this, so it ends up diluted with water and dumped or landfilled. This setup was relatively tolerable when processing 10,000 tons per year to power personal electronics and a small EV fleet; it’s unsustainable at forecast EV production volumes.

A terawatt-hour of battery production by this process—enough for 10 million battery packs averaging 100 kWh—will generate more than 2 million tons of sodium sulfate waste. Need a visual? That’s 500 NFL football fields spread a foot deep in waste. Even pollution-tolerant China is running out of ways to dispose of this waste stream. To make matters worse, the shipping cost and environmental footprint of metal sulfates is five times greater than it is for metal powders.

Nano One Materials Corporation proposes a better, sulfate-free idea. Its One-Pot Metals to Cathode Active Materials (M2CAM) process mixes pure metal, lithium-carbonate, and coating materials in a chemical process to form coated lithiated powders once they are fired in a furnace. This simpler, more direct process requires less energy and capital investment and hence is cost-competitive with the legacy process now and promises to undercut it with further improvement.

Patents are pending, so Nano One isn’t letting all its cats out of the bag, but it tells us the sulfate-free M2CAM process takes place in water (using 60 percent less of it) at room temperature and atmospheric pressure. The chemistry is environmentally sustainable, results in no waste, and slashes shipping costs for raw materials by a factor of four or five.

Nano One says it can modify the process to produce various cathode chemistries for use in traditional or solid-state battery formats, by modifying formulations, coatings, and process parameters. And because its One-Pot Process coats the cathode materials as they’re formed, the coatings are applied to each individual crystal within the larger particle. This helps prevent side reactions like lithium spikes (which can short a battery), thereby improving durability.

What about obtaining those pure metals, you ask? Depending on the mine and the metal ore, a refiner might crystalize the metal using a process involving chemical reactions, filters, membranes, and various electrochemical methods, or they may plate it out with electricity to achieve battery-grade purity. This sounds expensive, yet in most cases we’re assured these approaches typically cost less than producing metal salts—and remember, the pure metal powders are lighter and cheaper to ship.

When might these “greener” no-sulfate cathodes hit the road? Nano One is working with automotive companies and suppliers to create demand for its cathode materials while actively seeking a potential licensee or joint-venture production partner. The company hopes to open a pilot production facility by 2024. For the sake of those 500, foot-deep football fields, let’s hope it can stick to that timing.

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