Barry on Batteries: Adapting Hydromet for the Evolving Battery Market

Last month, we looked at the recycling processes for recovering cathode-active materials from black mass via pyrometallurgical, hydrometallurgical (Hydromet) and direct recycling methods. We also provided an overview of the pyrometallurgical process.

Building on that foundation, this article will take a more in-depth look at the Hydromet approach, which is a complex process involving numerous unit operations.

Let’s Take it From the Beginning

Once we produce black mass via a mechanical, drying or sorting recycling process, we then convey or transfer it to a separate location. Using the Hydromet process, material recovery is achieved via leaching in acids (or bases), impurity removal, metal extraction and lithium recovery.

Each step requires solid-liquid separation, clarification, process drying, reacting and solids handling. Given the number of steps, holistic chemical engineering is necessary to ensure optimum operations. 

In the initial stage, metal ions dissolve from the black mass, including nickel, cobalt, manganese, aluminum, iron and lithium. The most common leaching agent is a mixture of sulfuric acid and hydrogen peroxide.

The process requires several critical decisions. First, processors must choose the leaching agent – this could be an inorganic, organic or a bioleaching agent. 

They must then select a reducing agent, such as hydrogen peroxide, sodium-based compounds, glucose and others. When you consider the possible combinations and concentration ratios, the choices become exponential.

With the chemistry decided, it’s time to select the mixing technology or the solid-liquid separation technology with or without leaching or washing capabilities. 

The decision depends upon the leaching mechanism – if the chemistry is based on dissolution and contact time (mixing) or displacement (SLS). The SLS technology can be vacuum belt filters or filter presses depending upon cycle times, containment, leaching efficiencies via displacement washing, solids and liquid handling. 

Now, before you can process the leachate or clean filtrate to recover the valuable metals, there is a purification process to remove unwanted dissolved metal ions, such as aluminum and iron through precipitation with pH adjustment and SLS.

You also need to remove unleached solids, such as carbon and graphite, from the black mass. A future column will discuss graphite, which comes with additional challenges.

At this stage, the clean, solids-free leachate or filtrate is ready to move to the next process of recovering lithium, nickel, cobalt and manganese metals. For this recovery step there also are many options for ion exchange, including solvent extraction, chemical precipitation or electrolysis. In this step, you recover cobalt, nickel and manganese separately.

The leachate/filtrate then continues to lithium recovery via precipitation and/or crystallization. This adds further complexity to your SLS choices with a nutsche filter-dryer. 

This process recovers all high-purity battery metal materials for recycling. Battery manufacturers then reformulate these battery-grade materials into cathode-active components. However, the Hydromet process presents significant challenges.

It operates as a complex chemical refinery, demanding extensive chemistry knowledge, equipment expertise and the ability to seamlessly integrate each step. Mastering this intricate process poses considerable difficulty.

Hydromet Meets Lithium-iron-Phosphate

The focus here has been on recycling lithium-ion batteries. However, it's important to note that an alternative technology is gaining traction: lithium-iron-phosphate (LFP) batteries.

LFP batteries eliminate the need for cobalt, nickel and aluminum, making them less expensive to produce. The choice between LIBs and LFPs ultimately depends on the preferences of automotive manufacturers.

This evolving market landscape means the Hydromet process will need to demonstrate significant flexibility and adaptability to handle both LIB and LFP chemistries. Ongoing research aims to optimize these processes for cost, versatility, environmental impact and sustainability.

Overall, this is a rapidly changing field filled with opportunities for chemical experts and innovative plants. We all have a role to play in advancing these critical recycling technologies.

 The Hydromet process is already operational, and with continued improvements it can become an essential part of a more circular, sustainable battery ecosystem.