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When batteries are stored or used, unwanted reactions occur inside the battery leading to degradation of battery performance. Many of these unwanted reactions, such as transition metal dissolution, lithium inventory loss, and SEI growth, can be slowed or passivated by surface coatings. The Atomic Layer Deposition (ALD) process provides the best performing, most precise, reproducible, scalable, and cost-effective coating process to reduce unwanted reactions and enhance the performance of batteries. ALD can be applied to a wide variety of cathode and anode powders to produce benefits including longer cycle life, lower gas generation, slower impedance growth, and higher voltage utilization. Currently, multiple Fortune 500 companies are optimizing ALD coatings for their specific electrode powders and batteries with the use of high throughput ALD systems that can process 3,000 kg – 30,000 kg of powder per day (~10,000 tons per year per system) for <<$1/kg total coating costs (CAPEX + OPEX).
ALD coatings stabilize materials. ALD coatings on anode and cathode powders improve battery performance. The stabilizing nature of ALD coatings reduce metal dissolution, reduce SEI formation, and reduce lithium inventory loss. These effects can lead to the following benefits, depending on the application:
Cathode powders: NCM (>80%Ni, 811, 721, 622, 532), LCO (at 4.5V, 4.6V), NCA (>80%Ni, >90%Ni), LMO (spinel and non-spinel types), LMNO
Anode powders: natural graphite, synthetic graphite, Si/C composites, silicon
For coatings on cathode powders, the higher the Ni concentration, the less stable the cathode materials and the more important the surface coating. For high Ni materials, ALD coatings provide the most benefit versus other coating methods.For coatings on anode powders, even just a very thin ALD coating can provide significantly enhanced cell cycle lifetimes and higher voltage performance.When combining a coated cathode with a coated anode, even more benefits can be observed for certain systems such as LCO/graphite systems. These benefits include higher initial specific discharge capacities and higher capacity retention over cycle life.
ALD coatings of various materials have shown to enhance battery performance in different applications and in different ways. Aluminum oxide is the main chemistry of choice for most processes and can improve battery performance metrics discussed in this article. However, many companies are now exploring advanced coatings such as those designed to have higher Li-ion mobilities and transport numbers. These advanced ALD coatings are often applicable to lithium ion batteries, hybrid batteries containing solid state components, and fully solid-state battery systems. Advanced ALD coatings under current exploration for battery materials include metal oxides (other than aluminum oxide), lithium metal oxides, metal phosphates, metal fluorides. Advanced ALD coatings that may also be considered for battery materials include polymer coatings, hybrid oxide/carbon coatings, sulfur-coating coatings and others.
Although ALD coated materials show benefits on a variety of battery materials, recent coatings have shown particular benefit for fast charging of NMC 811 and high voltage operation of LCO. This recent work shown below is of importance for automotive batteries (NMC811) and consumer electronics (LCO).
Below; 811 fast charge (4C/1C) data showing ALD-coated NMC811 (blue, top line) is better than NMC811 without ALD (grey, bottom line). Both are cycled against uncoated graphite up to 4.2V
Below; Graphite fast charge (4C/1C) data showing ALD coated graphite (blue, top line) is better than uncoated graphite (grey, bottom line). Both are cycled against uncoated NMC811 up to 4.2V.
Below; LCO lifecycle data showing ALD coated LCO (blue, top line) is better than LCO without ALD
(grey, bottom line). Both are cycled against uncoated graphite.
Below; Graphite lifecycle data showing ALD coated graphite (blue, top line) is better than uncoated
graphite (grey, bottom line). Both are cycled against uncoated LCO up to 4.4V.
Below; LCO and Graphite, high V (4.5V) lifecycle data showing ALD coated graphite against ALD-coated LCO (blue, top line) is better than uncoated graphite (grey, bottom line) cycled against uncoated LCO.
40 Ah Automotive Pouch Cells (NMC 811)
Coin cells are a great method for screening materials, but larger cells are required to fully
understand the value ALD coatings can bring to battery materials. 40 Ah automotive pouch cells
have been created with ALD coatings and electrochemical testing is currently underway. The
goal of this project was to demonstrate that ALD coatings could enhance larger cells including
safety and performance. Check back with us soon at forgenano.com to see some new data for
these 40 Ah cells.
Below; Forge Nano’s recent 40 Ah automotive cells show enhanced performance and safety with ALD coatings.
Forge Nano is located in Colorado in the USA. They are the world leader in ultra-thin, surface
modification technology for markets including energy storage, catalysis, additive
manufacturing, electronic materials, adsorbents, and others. Forge Nano works with strategic
partners to jointly develop and integrate ALD-modified materials into commercial supply
Forge Nano has successfully raised over $20M from the following investors:
Including research, pilot, and commercial scale systems capable of processing
anywhere from 1.0 g to 30,000 kg powder per day.
Forge Nano assists customers daily with both R&D and commercialization of ALD enabled materials. For R&D, we both offer research services for proofs of concept and sell our R&D equipment globally. For commercialization, we offer joint development of products, production equipment, and IP licensing.
For additional information please contact us on our contact page.