Researchers Validate Benefits of Dry Processing in Lithium-Ion Battery Manufacturing

Researchers from the U.S. Department of Energy’s Oak Ridge National Laboratory (ORNL) in Tennessee recently tested an alternative manufacturing process that could allow electric vehicle battery makers to avoid toxic solvents in electrode production. 

 

This battery anode film was produced with dry processing, aiding its durability and flexibility. Image used courtesy of Navitas

 

The electrodes in conventional lithium-ion (Li-ion) batteries–now ubiquitous in the EV market–are typically made through a wet slurry process using N-methyl pyrrolidone (NMP) as a solvent. Despite its proliferation, this process has several technical disadvantages, such as cracking in thick electrodes, energy intensity in drying, and binder migration. 

NMP’s toxicity requires the solvent to be recycled, further adding to the already-high capital expenditures of production. The researchers estimate the electrode coating and drying process represents 11.5% of manufacturing costs and around 46% of energy consumption in Li-ion battery production. 

The researchers wanted to explore a low-cost, advanced solvent-free electrode processing technique offering favorable electrochemical performance with lower energy consumption. The team developed a powder-to-electrode dry processing approach primarily based on powder dry mixing and rolling/calendaring. 

Experiments showed the dry battery manufacturing technique removes the need for the toxic solvent while also boosting the battery’s durability, as it isn’t as burdened by inactive elements and can maintain high energy storage capacity.

Overall, thicker electrodes enable higher energy loading and reduce inactive ingredients that add weight and size. 

 

Benefits of Dry Processing

Dry processing is a relatively new but compelling alternative to conventional wet slurry processing, saving manufacturers energy, waste disposal, and additional startup expenses. In their recent study, the ORNL researchers mentioned that although the strategy was recently commercialized, little research has been published about it—particularly with both anodes and cathodes fabricated by dry processing. 

In a partnership with Navitas Systems, a Michigan-based energy storage provider, ORNL researchers explored how dry processing influences an electrode’s structural properties, electrochemical kinetics, and electrolyte passivation layers. According to ORNL, their concept mixes dry powders with a binder and then compacts the material for enhanced contact between the particles. 

A key practical benefit of dry processing is that it can be applied with current electrode production equipment, and plants can take advantage of its reduced environmental footprint to boost their overall sustainability. 

Bryan Steinhoff, a Navitas Systems research engineer who helped lead the project, said that dry processing could supplement the coating and solvent equipment otherwise required for battery production at a large scale. With dry processing, companies can cut their footprints by up to 40-50%, which equates to hundreds of millions of dollars in savings. They can also use it on domestic infrastructure, reducing reliance on international suppliers. 

 

Bryan Steinhoff, a Navitas Systems research engineer who helped lead the project, said that dry processing could supplement the coating and solvent equipment otherwise required for battery production at a large scale. With dry processing, companies can cut their footprints by up to 40-50%, which equates to hundreds of millions of dollars in savings.

 

These benefits are relevant to EV makers and their battery suppliers, which are increasingly investing billions in shoring up their manufacturing capacity in the United States. Several pairs have announced new plants in recent months, including General Motors (GM) and Samsung SDI, Hyundai and LG Energy Solution, and GM and Microvast. 

 

Results of the Study

ORNL researchers studied the degradation and electrochemical performance of Navitas electrodes in different conditions. In a recent study published in Chemical Engineering Journal, the team documented how dry-processed high-loading graphite anodes show promising electrochemical performance in fuel cells and half-cells. In the former case using fuel cells, the performance of electrodes from dry processing beat that of conventional slurry-based electrodes, delivering capacity retentions of 74.1% and 63.6% across 400 and 800 cycles, respectively. 

Since the electrode has more active materials, it faces fewer cracks even after cycling, equating to high energy density and long-term cyclability. Its mechanical flexibility also supports winding capabilities in mass production. 

In future research, ORNL and Navitas plan to stabilize the binder for the anode environment and reduce the use of carbon black material, which negatively impacts energy density.