Manufacturing costs of lithium-ion batteries cut in half with this new approach

A team of researchers from MIT and spinoff company 24M have developed a new manufacturing process for lithium-ion batteries that not only cuts production costs in half, but also promises a better performing battery that is easier to recycle.

The current process for manufacturing lithium-ion batteries has not changed in the two decades since the technology was first invented. By today’s standards, most consider it inefficient, with more steps and components than what is truly necessary. 

The new method is actually based on a concept half-a-decade old. It was developed by Yet-Ming Chiang, the Kyocera Professor of Ceramics at MIT and co-founder of 24M, and colleagues including W. Craig Carter, the POSCO Professor of Materials Science and Engineering. Referred to as a “flow battery”, electrodes are treated as suspensions of tiny particles carried by a liquid and pumped through the many different parts of the battery. 

The newer process, developed by Chiang, Carter, and their team, is a hybrid between this flow battery concept and the more conventional, solid ones; that is, while the electrode material doesn’t flow, per se, it is made up of a similar semisolid, colloidal suspension of particles. The team refers to it as a “semisolid battery.”

A battery such as this is super simple to manufacture. What’s more, it also makes it flexible and therefore, a bit more resistant to damage. 

Chiang arrived at this current concept after co-authoring a paper published in the Journal of Power Sources that analyzed the tradeoffs involved when choosing between solid and flow-type batteries; specifically, their applications and chemical components. What his team found during this analysis was that while a flow-battery system is great for battery chemistries with a low-energy-density, for high-energy-density devices (like lithium-ion batteries), the extra complexity and components of a flow system would add unnecessary cost.

“We realized that a better way to make use of this flowable electrode technology was to reinvent the [lithium ion] manufacturing process,” Chiang explains. 

The standard method of manufacturing a lithium-ion battery involves the application of liquid coatings to a roll of backing material, and then waiting for it to dry before moving on to the next step. The new manufacturing process keeps the electrode material in a liquid state, thereby eliminating the drying stage altogether. Also, this system uses fewer, thicker electrodes which, in turn, reduce the normal lithium-ion battery architecture’s number of distinct layers, as well as the amount of nonfunctional material in the structure, by an astounding 80%.

The obvious question here is how in the world are they able to use thicker electrodes? Well, having the electrode in the form of tiny suspended particles, as opposed to consolidated slabs, reduces in large form the path length for charged particles moving through the material. It’s a property known as “tortuosity.” So, in layman’s terms, by figuring out a less tortuous path for the electrodes to travel, the team was able to go with thicker electrodes which, in turn, simplifies production, and lowers cost.

To date, the company has about 10,000 batteries on its prototype assembly lines. Most of them are now going through testing by three industrial partners, including an oil company in Thailand and IHI Corporation, a heavy-equipment manufacturer in Japan. The team has already secured eight patents for this new process, and they have another 75 under review. They’ve also raised $50 million in financing from various venture capitalist firms and a US Department of Energy grant. 

Looking ahead, the MIT / 24M team will focus on grid-scale installations, with the goal being to hopefully smooth out power loads and provide backup for renewable energy sources that produce intermittent power (wind, solar). Beyond that, Chiang believes the process can also be applied to technologies where weight and volume are a bit more limited; this includes electric vehicles.

In terms of applying this new manufacturing process at the factory-level, Chiang points out the fact that his team’s method can be scaled up rather easily by adding identical units. This is completely counter to current lithium-ion plants, which must be built at large scale from the beginning in order to keep unit costs down (this requires much larger initial capital expenditures). Chiang estimates that 24M will have the means to produce batteries for less than $100 per kilowatt-hour of capacity. 

Read the team’s initial analysis, which served as the foundation for this development: Component-cost and performance based comparison of flow and static batteries.

Via MIT