Recycling Potential of Lithium–Sulfur Batteries—A First Concept Using Thermal and Hydrometallurgical Methods

Abstract

High-energy battery systems are gaining attention in the frame of global demands for electronic devices and vehicle electrification. This context leads to higher demands in terms of battery system properties, such as cycle stability and energy density. Here, Lithium–Sulfur (Li–S) batteries comprise an alternative to conventional Li-Ion battery (LIB) systems and can be asserted to next-generation electric storage systems. They offer a promising solution for contemporary needs, especially for applications requiring a higher energy density. In a global environment with increasing sustainable economics and ambitions towards commodity recirculation, the establishing of new technologies should also be evaluated in terms of their recycling potential. In this sense, innovative recycling considers highly valuable metals but also mobilizes all technologically relevant materials for reaching a high Recycling Efficiency (RE). This study uses an approach in which the recycling of Li–S batteries is addressed. For this purpose, a holistic recycling process using both thermal and hydrometallurgical steps is suggested for a safe treatment in combination with a maximum possible recycling efficiency. According to the batteries’ chemical composition, the containing elements are recovered separately, while a multi-step treatment is chosen. Hence, a thermal treatment in combination with a subsequent mechanical comminution separates a black mass powder containing all recoverable resources from the metal casing. The black mass is then treated further in an aqueous solution using different solid/liquid ratios: 1:20, 1:50, 1:55, and 1:100. Different basic and acidic leaching solutions are compared with one another: sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), and NaOH. For further precipitation steps, different additives for a pH adjustment are also contrasted: sodium hydroxide (NaOH) and potassium hydroxide (KOH). The results are evaluated by both purity and yield; chemical analysis is performed by ICP-OES (inductively coupled plasma optical emission spectrometry). The aim of this recycling process comprises a maximum yield for the main Li–S battery fractions: Li, S, C, and Al. The focal point for the evaluation comprises lithium yields, and up to 93% of lithium could be transferred to a solid lithium carbonate product.

Recycling of Lithium‐Ion Batteries—Current State of the Art, Circular Economy, and Next Generation Recycling

“…[ 264–266 ] However, some approaches were reported in the literature. [ 267 ] While the challenges with regard to the Li metal are discussed in the section above, the separator, binder and electrolyte can be subject to similar recycling procedures which are used or investigated for LIBs. Nevertheless, it is necessary to carry out further studies on the applicability and possible upscaling for industrial processes.…”

“…In best cases, these gases can be converted to elemental sulfur or precipitated as sulfides, for example with copper. [ 267 ] However, in combination with the highly reactive Li metal anode, separation and handling of the electrodes will complicate future recycling.…”

Environmentally Friendly Recovery of Lithium from Lithium–Sulfur Batteries

“…A first recycling approach can be found in [18]. Here, lithium was recovered by conventional leaching.…”

“…Li-losses in the different filter cakes were found and Li-losses in the residual filtrate and impurities in the product. An LCA (Life Cycle Analysis) of this process path for lithium-ion batteries demonstrated that pH-adjustment by NaOH, which was used in [18], significantly contributes to the GWP (global warming potential), TAP (terrestrial acidification potential) and FDP (fossil depletion potential) of this process [19]. NaOH production makes up the largest part in FDP and GWP, hence it demonstrates the highest impact regarding the environmental impact categories of the process [18,19].…”

“…Independently from the type of hydrometallurgical treatment, namely acidic/alkaline leaching or aqueous leaching, a filter cake containing mainly aluminum and graphite/carbon materials [18] was obtained. To follow a circular economy, this material should be treated for raw material recovery.…”