Lighter, less expensive lithium-ion batteries through coating

A process for lithium-ion batteries that improves conductivity and durability and reduces manufacturing costs could lead to lighter, less expensive batteries, including solid state versions especially relevant for airplanes…and boats.

The ‘One Pot’ process has been developed by Nano One Materials of Vancouver, Canada, who have been working on it since 2011 with the first proof of concept announced in 2013. Since then they have built a pilot plant, been granted multiple international patents and partnered with companies like Volkswagen and Pulead Technology, one of China’s leading lithium-ion battery cathode producers.

Cathode of lithium-ion batteries is the key

‘Cathode producer’ is the key here. There are three main parts to a battery – the electrolyte, anode and cathode. The anode (the negative pole of the battery) and electrolyte (the part the ions flow through from one pole to the other) haven’t changed much in a Li-ion battery since 1991. The anode is carbon based and the electrolyte is a lithium salt dissolved in a liquid or gel. On the other hand the cathode (positive pole) has seen a lot of changes and comes in many variations.

The cathode contains lithium mixed with some other metal or combination of metals and the image above –  from an excellent infographic on the Nano One website – illustrates some of them. Two of the most common for lithium ion batteries are Nickel/Manganese/Cobalt (NMC) and  Nickel/Cobalt/Aluminum (NCA) while a LiFePo4 battery has a Lithium Iron Phosphate version.

Read about a new glass battery in development from one of the inventors of lithium-ion 

There is no ‘perfect’ combination of chemicals, each has some advantages but also disadvantages. Cobalt, for instance, is not only expensive, but includes ethical issues because of the treatment of miners in places like the Democratic Republic of the Congo. Some cathodes charge quickly but heat up faster than others. Other combinations develop dendrites, stalactites of microscopic needles that can cause all kinds of problems over time. 

As we wrote last week, Samsung is one company working on the dendrite issue, but their research is limited to one kind of chemistry in the cathode. The Nano One difference is that it can improve the performance – and lower the manufacturing costs – for all kinds of cathode chemical combinations. 

Nano One process coats individual crystals

One of the current methods for addressing some cathode deficiencies is coating the cathode materials. Among other things coating can help improve the flow of ions in and out of the cathode and means metals like metals like nickel can replace some of the cobalt. 

What the Nano One process does is take that a step further, by coating individual nano-crystals in the cathode material, not clumps of the material. It is called the ‘One Pot Process’ because it also does it in a different way. To be simplistic, all of the cathode metals can be mixed together with the coating material and everything ‘cooked’ all at once in a kiln. The standard process requires two kiln firings over a course of days while the one pot process only takes a few hours.

The Nano One website explains that the coated clusters made with the standard process (Left, above) are prone to cracking and degradation from battery assembly and repeated charging, especially at high voltage. The One Pot Process (Right) coats each individual particle – nano-crystal – for better durability and longer battery life.

Solid state batteries for airplanes, boats

Solid State Batteries (SSBs) is where the ‘lighter’ part of the battery equation comes in. SSBs are the big goal in electric cars, because they can hold more energy in the same space as a liquid or gel sort. Solid state batteries using LMN (Lithium/Manganese/Nickel) cathodes hold big promise for electric airplanes, partly because they would also use ultrathin and light lithium metal anodes. But there are challenges.

Nano One’s Chief Technical Officer, Dr. Stephen Campbell, says the largest single challenge “is to design a stable and commercially viable interface between the solid electrolyte, of polymer, ceramic or glass composition, and the solid cathode and anode materials on either side of this electrolyte”. Nano One and (unnamed) automotive companies recently announced that tests they performed on solid state batteries of differing compositions had ‘positive results’.

In some ways, aviation batteries are more akin to what marine propulsion needs because  airplanes and boats both need to ‘float’. One of the encouraging aspects of these SSB tests is that the One Pot Process looks like it can reduces costs. The single kiln firing is one advantage and the other is that the nano-particle coating makes nickel a viable and cheaper alternative to cobalt.

The road to market viability

Whenever we write about batteries it is important to say that it is a long journey from the drawing board and test results to something available to consumers. Nano One has a strategy, though, that might speed up that process.

The company’s business model does not include doing the processing of the materials themselves. Instead they will license the technology to companies like VW, Pulead and potentially others, who presumably already have the factories, personnel and distribution channels to get it to market fairly easily.