Development of a Process for Direct Recycling of Negative Electrode Scrap from Lithium-Ion Battery Production on a Technical Scale and Its Influence on the Material Quality

Abstract

High production rates and the constant expansion of production capacities for lithium-ion batteries will lead to large quantities of production waste in the future. The desired achievement of a circular economy presupposes that such rejects could be recovered. This paper presents a two-staged process route that allows one to recover graphite and conductive carbon black from already coated negative electrode foils in a water-based and function-preserving manner, and it makes it directly usable as a particle suspension for coating new negative electrodes. In a first step, coating residues, which accumulate in production (as offcuts or rejects for example), are decoated in an aqueous ultrasonic bath. The ultrasonic bath also serves as a pre-thickener. As a result, high mass concentrations of active material can already be achieved in the water after the first process step. Water is then removed from the negative electrode suspension in a subsequent step by applying dynamic cross-flow filtration. With this unit operation, it is possible to concentrate the slurry residue to a solid content similar to that of the new electrode slurries used for coatings. An important criterion for the direct utilization of production waste is that the particle properties are affected as little as possible so that the suspension can be used directly for coating new films. This work presents the individual recycling process steps and their influence on the particle and slurry properties. The aim is to assess whether the recyclate is suitable for a coating of new negative electrodes and thus also for manufacturing batteries from 100% recycled material.

Keywords

• direct recycling of LIB
• dynamic cross-flow filtration
• particle properties
• ultrasonic decoating