Innovations in Direct Recycling Enhanced through a Design for Circularity Approach
Authors: Ziegler Simon , Hofmann Michael , Flegler Andreas , Deuso Sara Li , Mandel Karl Sebastian , Giffin Guinevere A. 
Published: December 2024

In principle, spent batteries represent a valuable source of secondary material to obtain strategic and critical raw materials. However, there is still a need to develop efficient, sustainable, and low energy recycling processes that allow easy access to these materials. The main battery recycling processes considered to date are pyrometallurgy and hydrometallurgy as well as direct recycling.[1] The latter approach has the decisive advantage that the materials are not down-cycled into precursors, but are maintained in their original structure, which in principle allows the direct reuse in the manufacture of new batteries. While pyrometallurgical and hydrometallurgical processes have already been industrialized by several companies, the technological maturity of direct recycling is rather low and needs further development.

One way to improve both direct recycling technologies and the quality of their material output is through the implementation of Design for Circularity concepts. The research presented within this contribution focuses on some of the key issues of direct recycling as a part of a Design for Recycling approach for lithium-ion batteries. These issues include aspects related to electrode processing, separation and classification of materials during recycling and a concept to facilitate sorting for recycling.

The use of aqueous-based electrode processing can be seen as a design concept to facilitate water-based direct recycling processes. In this context, the electrode binder plays a role in both the electrochemical performance and the detachment of the electrode mass during direct recycling. The results of this work showed that changing the cathode binder can improve the cycle life in full cells by 60% and also improve the detachment of the cathode active material (CAM) from the current collector. After detachment, the separation and classification of the cathode materials using a water-based process provides a CAM material that can be reused depending on its quality.

Direct reuse of the recovered CAM has not shown adequate performance due to the negative effect of water on the nickel-rich cathode material. To address this issue, an additional process step was introduced which resulted in a significant improvement in CAM performance during reuse. In subsequent work, this process step has been further developed into an in-situ process integrated into the cathode electrode production.

The quality of secondary materials can be improved by purifying material streams during recycling. To this end, an innovative marker technology based on supraparticles is introduced and the most suitable location for implementation in the battery cell is investigated, taking into account the effects of the markers on the cell performance and vice versa.

The aspects addressed within this contribution are some of the steps in a highly interdisciplinary approach to develop a complete process chain for direct recycling. The integration of Design for Circularity is expected to simplify the process chain and improve the quality of the secondary materials.

[1] A. Prazanová, V. Knap, D.-I. Stroe, Energies, 2022, 15, 1086.