Bulk analysis of battery black mass by CNA

Introduction

The shift to electric vehicles is crucial for combating climate change and improving air quality. By adopting electric mobility, we can drastically reduce greenhouse gas emissions and harmful pollutants into the environment. 

While EVs help reduce dependence on fossil fuels by offering cleaner alternatives to traditional combustion engines and promote a sustainable future, managing their end-of-life batteries poses a significant challenge. Hence, battery recycling is crucial for conserving natural resources and protecting the environment. By recovering valuable metals like nickel, cobalt, and manganese from old batteries, we reduce the need for mining and lessen the environmental impact associated with extraction. 

Black Mass, a powdery extract from crushed lithium-ion batteries, is essentially a concentrated form of cathode material rich in valuable metals like nickel, cobalt, and manganese. These metals can be recovered through hydrometallurgical or pyrometallurgical processes. 

Figure 1: Recycling of battery materials

Challenges

While the handheld devices are ideal for rapid screening of incoming black mass, more precise analysis is possible using X-ray fluorescence (XRF) instruments during the process by analysing powder and liquid samples.

The wide variety of cathode chemistries found in battery black mass (including NMC, NCA, LFP, and LCO), each with unique ratios of valuable metals such as nickel, manganese, and cobalt, is the primary reason for its significant heterogeneity. This inconsistency presents a major challenge in precise determination of the total metal content and economic value of the black mass before processing.

Precisely determining the metal content within black mass is vital for optimizing the recovery process and ensuring its efficiency. Unlike the LFP, NMC Li-ion batteries have diverse compositions, including variants like 622, 811, 111, 333, and 532. The black mass recovered from spent Li-ion batteries is highly inconsistent in composition, making traditional laboratory analysis through sampling a challenge. 

	NMC811	NMC523	NMC662	NCA+	LFP
Lithium	5 kg	7 kg	6 kg	6 kg	6 kg
Cobalt	5 kg	11 kg	11 kg	2 kg	0 kg
Nickel	39 kg	28 kg	32 kg	43 kg	0 kg
Manganese	5 kg	16 kg	10 kg	0 kg	0 kg
Graphite	45 kg	53 kg	50 kg	44 kg	66 kg
Aluminum	30 kg	35 kg	33 kg	30 kg	44 kg
Copper	20 kg	20 kg	19 kg	17 kg	26 kg
Steel	20 kg	20 kg	19 kg	17 kg	26 kg
Iron	0 kg	0 kg	0 kg	0 kg	41 kg

Table 1: Typical composition of a 60 kWh Li-ion battery

Analytical Solution

Owing to its high penetration depth, neutron activation analysis provides a 100% measurement of incoming black mass on a conveyor belt. The CNA Pentos, featuring a unique D-T PFTNA electrical neutron generator, offers a direct bulk analysis solution for incoming black mass, requiring no sample preparation.

Figure 2: Depth of penetration

During neutron activation, neutrons interact with the nuclei of atoms in a material and can be captured, forming an unstable, excited nucleus. 

The CNA utilizes neutrons generated by an electrically operated D-T PFTNA generator to interrogate the  sample. This process stimulates the emission of unique prompt gamma rays from the elements present. Real-time analysis of these signature emissions allows for the determination of the material's elemental composition. This valuable technique finds significant application in online process control for industries including cement, coal, and mining.

Figure 3: Gamma signal response for a typical black mass composition

The D-T PFTNA neutrons being high-energy fast neutrons of 14 MeV, can excite light elements like carbon and oxygen through inelastic scattering reactions, primarily (n, n'γ). This enables the direct measurement and estimation of the calorific value and volatile matter of black mass during pyrometallurgical treatment. 

Knowing the precise composition of black mass is essential. While a consistent supply from a single source might allow for periodic lab analysis, comprehensive elemental characterization is crucial when processing materials from various providers of discarded LIBs. Determining the presence of LFP or NMC variants directly influences the optimization of hydrometallurgical process parameters (pH, temperature), the efficient and accurate use of reagents (reducing waste and costs), the estimation and improvement of recovery rates, and the utilization of graphite content for yield calculations and its potential reducing effects during heat treatment.

Figure 4: Typical scheme of deployment of the CNA

Conclusion

While the electric vehicle transition offers substantial environmental benefits, the challenge of managing end-of-life batteries necessitates efficient recycling processes. The inherent heterogeneity of black mass derived from these batteries poses a significant analytical challenge for optimizing metal recovery. The Malvern Panalytical CNA, utilizing a D-T PFTNA neutron generator, emerges as a promising solution for providing rapid, non-destructive, and bulk elemental analysis of incoming black mass on conveyor belts, thereby facilitating more efficient and economically viable processing.