Barry on Batteries: Black Mass Testing Methods Need Industry Standards

Key Takeaways    

• Black-mass quality depends on a variety of factors. Battery type, origin and composition directly impact recycling value and the suitability for downstream metallurgical processes like pyrometallurgy and hydrometallurgy.
• The absence of an industrywide standard for measuring elemental composition in black mass represents an opportunity for chemical industry expertise and standardized instrumentation methods.
• Depending on the desired end-use requirements, multiple analytical techniques offer different strengths in accuracy, speed, and applicability for black-mass testing.

The recycling requirements for lithium-ion batteries varies depending on their application. Think about small-format batteries, those you would find in your smartphone, as an example. The components in these batteries are different than, say, those found in medium-format batteries that power equipment like leaf blowers, and the largest batteries found in motor vehicles. 

Small-format batteries will have much higher cobalt concentrations.  The result of all of this is that the revenue stream from the recycling process will be different, having an impact on the downstream metallurgical processes to produce battery-grade material.  

During one analysis we performed for a client, the black mass from electric-vehicle battery production scrap contained more than 18 different metallic compounds.  Each of the metallurgical processes require a difference black mass quality. For example, the pyrometallurgical process involves high temperature smelting or roasting, which usually requires burning and subsequent separation. This is the most forgiving process.  

The hydrometallurgical, or hydromet, process is achieved using aqueous chemistry, via leaching in acids or bases and subsequent concentration and purification. This requires high-quality black mass.  

Further down the supply chain, the battery-grade material from the above processes then must be validated by the battery cell manufacturer, so it can be reused in the specific battery category.  

Industry Moves Toward Classification Standards

There are different ideas in the supply chain to address recycling variations and black-mass quality.  Recently, I attended a presentation from the Battery Association for Supply Chain.  The association formed in April 2021, and its mission is to enhance the Japan's battery supply chain green and competitive initiatives.  

The group proposed a black-mass classification system based upon the percentages of nickel and cobalt with subclassifications based upon battery origin (cell, module, pack), battery types and process method. 

As we all know in chemical engineering, before you can classify components, you must measure them through data collection and analysis.  I can certainly analyze the data; however, I must admit that I am not an instrumentation or electrical engineer, and there is a completely different language compared with chemical engineering.  

What I do know is that there are currently no industry standards for determining elements in black-mass samples either for lab analyses with grab-sample preparation or in real time during production operations. This is clearly an area where the chemical industry can bring expertise and guidance to the recycling arena. 

Four Testing Methods Show Promise for Quality Analysis

Currently, there are three established instrumentation approaches and a newer technology called laser ablation laser ionization time of flight mass spectrometry, or LALI-TOF-MS that are available for black-mass quality testing. Here’s a closer look at each method:

Inductively coupled plasma optical emission spectroscopy (ICP-OES) can be used to determine the elements in black mass. This technique can analyze 18 elements quickly with small sample sizes. The performance data shows that ICP-OES can be used for routine, accurate measurement of high- and low-concentration elements in black-mass samples for valuable elements, such as Co, Mn, Ni and Li, as well as contaminant elements such as Fe, Cu and Zn.

Another technique is to use a handheld laser-induced breakdown spectroscopy instrument (LIBS) in combination with an artificial neural network (ANN) algorithm to analyze the black-mass materials. The combination of the ANN algorithm speed and robustness with the reliability of the LIBS instrument allows for the quantitative analysis of lithium and other metals in the black mass extracted from the different types of batteries.

Microwave digestion of black-mass samples is another technique being employed with individual sample data. The microwave temperature, pressure and power are controlled to provide reproducible results from sample to sample. This approach provides the bulk composition of the material but does not show how the elements may change spatially or in depth. Depending upon the end use, this data may be important for battery-grade material validation. It also may be applicable to demonstrate that the recycling process of mechanical pretreatment and vacuum drying does not alter the material properties.  

LALI-TOF-MS is a new approach that’s effective if element changes are critical to the downstream or end-use process. This analysis is performed under vacuum, which is important for air-sensitive products and no “wet-chemistry” is needed which also is important in the production environment.

Finally, if you have a chance to visit a specialty chemical lab, you will find a host of instruments for determining particle size, compression and temperature stability, tensile strength, moisture, and other product specific characteristics. These measurements can be easily transferred into the recycling process because, in realty, the recycling process is producing specialty chemicals.