Pitch coating is the battery industry’s dirty little secret.

Originally published in Rho Motion Q1 2022 Magazine: The Batter Supply Challenge and its Solutions

EVs can be green, but only if every part of the materials value chain is focused on environmentally friendly processing.

When you hear the word “pitch,” you may think of baseball or even football (soccer to some), but a little-known industrial process called carbon pitch coating is responsible for a rather significant environmental impact in the manufacturing of batteries for EVs. This article explains what carbon pitch coating is, why it’s currently used, and how it can be replaced with something that’s lightyears better.

Carbon on Carbon?

Sounds strange, right? But that’s exactly what pitch coating is: carbon pitch coatings onto carbon graphite powders. Here’s how it works: pitch, a hard and shiny brown/black carbon from coal or petroleum, is chopped up into tiny pieces, mixed with graphite powder, heated, cooled, smashed, sieved, packaged, and shipped off to battery cell makers such as Panasonic, Samsung, CATL, and others who make your EV battery. In fact, a recipe for pitch coating might read a lot like a recipe for a very-burned cake mess … and you’d be right to think it doesn’t smell good either!

Is Pitch Coating a Necessary Evil?

Graphite needs to be coated with something to make it robust enough to last in a battery. Without a coating, the graphite quickly succumbs to unwanted side-reactions with the battery’s liquid electrolyte and the battery dies. The first cost-effective coating technology developed for graphite was pitch coating and thus it remains the technology used today by most graphite producers, despite its long list of significant inadequacies.

Pitch coating is dirty, expensive, inefficient, energy intensive, and difficult to implement:

  • Firstly, the pitch coating process emits toxic and carcinogenic compounds that are extremely bad for one’s health. 200 different chemicals are found in carbon pitch including arsenic, lead, chromium, selenium, and benzo[a]pyrene, a known procarcinogen with health effects causing damage to the nervous, immune, and reproductive systems.
  • At ~$1.50/kg, pitch coating is the most expensive step in making a graphite anode powder, keeping the cost of your new EV higher than you’d like.
  • Inefficient – the pitch coating process is a multistep process that takes a nicely rounded powder and turns it into a clumpy mess which needs to be broken up again before it can be used in a battery. This is akin to making popcorn, then drenching it in a home-made caramel sauce that’s too sticky and results in you having to break up that one giant lump of popcorn – what a pain!
  • To make the raw pitch ingredient, temperatures of over 1000°C are needed. This uses a lot of energy and creates a lot of CO2 emissions – and that’s just to make the pitch. The pitch is subsequently heated with the graphite to around 1000°C, again, for the coating process – think of all that wasted energy!
  • Pitch coating is a black art – the multistep batch processing, the inconstant pitch, and the various pieces of equipment needed mean that you need a lot of hands-on knowhow, continual adjustment, and outright luck to get a good coating.
  • Lastly, the pitch-coated graphite is very hard to recycle because the pitch is a soft coating that gunks up when you try to repurify graphite from used batteries. This is a serious barrier to cradle-to-cradle design.

Forge Nano and the Holy Grail of Graphite Coating

The majority of graphite producers, of which ~80% are based in China, have historically used pitch coating because “it works well enough and it’s cheap enough.” But, as non-Chinese graphite facilities come online with stricter environmental, social, and corporate governance (ESG) goals and higher land, labor, and equipment costs, producers are turning to Forge Nano’s coating technology to obtain a competitive edge in the market.

These companies, including Volkswagen, LG Chem, Sumitomo, Mitsui, Nouveau Monde Graphite, Gratomic, and Mineral Resource Commodities, don’t want to use pitch coating, but also don’t have time for small-scale research into alternative coating technologies. They need something that works today that is already both technologically and economically advantageous over pitch coating. Forge Nano provides exactly this with their proprietary atomic layer deposition technology and equipment developed specifically for the coating of graphite and other powders and particles.

Forge Nano scientists, nuzzled in the foothills of the Rocky Mountains of Colorado in the United States, are implementing a novel, cost-effective, and scaled process which is truly the holy grail of graphite coating. Their one-step, continuous process uses atomic layer deposition technology to replace carbon pitch with a high-purity, low-cost, gas-phase process leading to a 50%-70% cost reduction with 100% reproducibility. This process, scaled to 4,000T/yr per system, also provides a 70% lower environmental footprint. It has been validated by Forge’s Nano’s Fortune 500 and junior mining customers across research, pilot, and commercial systems with electrochemical testing in commercial battery cells sized over 40Ah in capacity.

Forge Nano’s systems create cost-effective coatings and are only available to joint development customers and supply chain partners with IP licensing. Indeed, Forge Nano partner Mineral Resource Commodities, Ltd. commented, “with Forge Nano’s ALD coating technology, we can produce a high-performing, cost-competitive graphite anode powder for lithium-ion batteries.” Forge Nano customers benefit from a turnkey solution and ongoing support for integration and operation of this equipment at their commercial production facilities, enabling them to meet the extreme demand growth of graphite materials for batteries.

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