Recycling of Lithium-Ion Batteries

This chapter outlines a wide range of reasons for the wide dissemination of lithium-ion batteries (LIBs) in our everyday lives and establishes a relationship between renewable energy, its storage and changes in European regulations regarding guidelines for a more efficient recycling of LIBs. To promote a clear understanding of current challenges in technological development of appropriate recycling strategies, the basic components and basic operation principles of a LIB are explained. Next, the most widespread types of commercial LIBs and processes for their manufacturing are presented in a more detailed way. Hereafter, two existing and practically used recycling methods are described and analyzed from the perspective of strengths and weaknesses.

The LithoRec projects were funded by the German Federal Ministry of the Environment, Nature Conservation Building and Nuclear Safety and VDI/VDE Innovation+Technik GmbH. The projects aimed to develop a new recycling process for lithium-ion batteries from electric and hybrid electric vehicles with a focus on energy efficiency and a high material recycling rate. The developed process route combines mechanical, mild thermal and hydrometallurgical treatment to regain nearly all materials of a battery system.

Due to their high voltage, high stored energy, and reactive components, lithium-ion batteries present a specific and significant hazard potential. This especially comes into play during recycling because nearly every safety precaution of a battery system and battery cell needs to be bypassed. Because the project partners of LithoRec II spared a thermal pre-treatment step to deactivate the batteries, the hazard potential and its handling played a major role. This chapter gives an overview of the hazards associated with lithium-ion batteries and describes their role in every process step.

A main objective of the project LithoRec II is to study the overdischarge of Li-Ion batteries for the purpose of recycling. For safety and functional reasons, the batteries need to be overdischarged before undergoing the process steps of disassembly and crushing. In this study, various devices for overdischarging are set up and investigated together with corresponding battery behavior. Device properties such as cost, safety, discharge time and discharge flexibility are assessed. Furthermore, the study focused on parameters like battery heating during discharge and pole reversal, relaxation amounts and heights as well as short circuit currents. The investigations show, that it is most advisable to discharge whole battery systems by energy recuperation into grid with electronic adjustable loads, because of efficiency and safety reasons. Overdischarging is not problematic if crucial battery parameters are observed. It is recommended that overdischarging of automotive traction batteries should only be done by high-voltage specialists.

Traction batteries are composed of various materials that are both economic valuable and environmentally relevant. Being able to recover these materials while preserving its quality is not only economically attractive, but it can also contribute to decrease the environmental impact of electric vehicles. Disassembly can play in this regard a key role. On the one hand it might allow to separate potential hazardous substances and avoid an uncontrolled distribution of these substances into other material flows. One the other hand disassembly might promote improving the rate of material recovered while preserving its quality and decreasing disassembly costs. In this chapter we present a methodology for the estimation of disassembly sequences and for the estimation of automation potentials for the disassembly of traction batteries. The methodology is illustrated with an experimental case study.

The rising number of electric vehicles will lead to an increase of EV batteries reaching their end-of-life. Efforts are therefore being made to develop technologies and processes for recycling, remanufacturing and reusing EV batteries. One important and necessary step for the recycling process is the disassembly of EOL EV batteries. Unpredictable lot sizes and volumes, as well as significant variations in battery design between different car models challenges the disassembly automation. Disassembly is therefore currently carried out manually. Fully-automated disassembly would require high product specific investments which is not economically feasible in changing production environments. Human robot collaboration aims to overcome those problems with partial-automation by incorporating sensor integrated robotics in more fields of human activity. This chapter presents the implementation of human robot collaboration for disassembly of lithium-ion Batteries. While the human operator performs the more complex tasks, the robot performs simple, repetitive tasks such as removing screws and bolts. An intuitive programming environment, which does not require experience in robot programming, is combined with cost efficient tooling and additional 3D safety sensors to realize a safe, productive and ergonomic workspace.

Crushing is a substantial process step for the following separation, as it transfers the battery cells or modules to a storable and conveyable bulk material. Crushing also leads to the opening of the battery cells and release of valuable materials. Because of the deliberate destruction of the battery cells, this process has a high hazard potential due to the remaining attached energy of the battery cells and the flammable electrolyte components. The project partners evaluated requirements for the design of a crusher and drafted a concept for the realization of a safe and efficient crushing process.

The recycled lithium-ion batteries are shredded to access value components for further processing. The material that has been shredded before must be dried. This is important not only because of the simplified separation of dry material, but also due to safety issues. A material loaded with electrolyte will be surrounded by a gaseous atmosphere loaded with electrolyte. Such a mixture of electrolyte and air has an environmental impact and can build an explosive atmosphere. Therefore, undried material requires gas tight as well as explosion protected equipment. Drying can be achieved by high temperature, low pressure and rinsing with inertization gas. To support process design and optimization, the influence of each parameter and advantageous parameter combinations can be determined with a flow sheet simulation. However, experimental investigations are required to verify simulation data and to identify critical aspects regarding handling of the material. This chapter discusses application and results of a flow sheet simulation as well as experimental investigations on drying.

The extraction of electrolyte from lithium-ion batteries is a possibility to remove the high boiling organic components and the conducting salt from the battery material in the recycling of lithium-ion batteries. In these studies, dimethyl carbonate was employed as organic solvent. The influence of temperature and solvent to solid mass ratio have been tested with Panasonic CGR 18650 batteries in a stirred vessel. Although the conducting salt was successfully extracted with a crossflow extraction with four stages, the remaining fluoride loading of the battery material was too high for further processing. Therefore, a second series of extractions with water was used to remove fluoride. The combination of four extraction stages with dimethyl carbonate and six stages with water for the processing of hybrid electric vehicle batteries resulted in a fluoride loading of 173.3 mg per kg fine fraction of the raffinate. Suggestions for the design of an extraction apparatus based on the experiments were worked out.

This chapter reports on experiments aimed at investigating the capability of pressurized carbon dioxide to extract the electrolyte from commercial available LIBs on a laboratory scale. Two different phase conditions of carbon dioxide (subcritical and supercritical) and two different extraction (static and dynamic) have been considered and analyzed for their strengths and weaknesses. Furthermore, the addition of co-solvents is examined with regard to their contribution to higher recovery rates. After reporting the optimized extraction method, the extracted electrolyte was analyzed by gas and ionic chromatography methods for potential de-composition products and their relative amount.

Some process steps in the recycling process containing a significant amount of volatile organic compounds, such as shredding and drying, need to be inertised by flushing with dry nitrogen. Consequently, the off gas of this inertization is loaded with electrolyte or extraction solvents. Due to environmental restrictions, this off gas has to be cleaned before it is released. This chapter addresses the off gas cleaning with adsorption onto activated carbon and gives a basic understanding of the operation mode of a fixed bed adsorber and the database to design an adsorptive off gas cleaning. Relevant data of adsorption equilibria of single as well as binary mixtures of electrolyte components onto activated carbon at temperatures from 20 to 60 °C are presented. Additionally, binary equilibria were calculated with the Ideal Adsorbed Solution Theory and compared to experimental results. Finally, results of the adsorption in a fixed bed are discussed. Breakthrough behavior and temperature profiles of the adsorption process are presented and compared to the adsorption equilibria. Another focus is set onto decomposed electrolyte components that may occur during the lifetime of a battery, the recycling process and the adsorption itself. These decomposition products can affect the adsorption equilibrium and therefore have to be considered.

The material separation processes combine all mechanical treatments after crushing and drying, which aim to separate the different materials of lithium-ion battery modules. In the following text, the input material for these processes is characterized before the multistage separation and different process influences are described. The resulting process is a combination of mixing, zig-zag-sifting, crushing, and sieving processes, leading to an overall material recycling rate of 75–80% of an electric vehicle (EV) battery system.

In this chapter, electrodes containing the cathode material Li[Ni_0.33Co_0.33Mn_0.33]O₂ (NCM) were recycled in order to test a newly developed recycling concept which is aiming towards commercial application. The possibility of graphite recovery from spent LIBs by means of three different treatment methods is demonstrated.

This chapter describes the areas and aggregates, as well as the operating cycle of the realized temporary demonstration plant in Braunschweig. This plant was run by employees of TU Braunschweig and Lion Engineering GmbH. As especially safe processing of entire battery systems had to be assured, the developed safety concept is presented. Overall, the demonstration plant processed 1.4 tons of the battery systems of electric vehicles, reaching a material recycling rate of up to 80%.

The successful implementation of an industrial-scale recycling process depends strongly on its economic feasibility. Thereby, the economics are influenced by many drivers such as the amount of returned batteries, the prices that can be obtained from selling the recycled material fractions, and investments and operating costs resulting from the process configuration. In this chapter, an analysis of the economic feasibility of the LithoRec process is carried out using an optimization model for technology and capacity planning. The model is applied to different scenarios describing the development of the amount of spent batteries and factor prices for the European market. From this, optimal investment plans and financial performance indicators are determined. Overall, the results indicate that the process can be operated economically in the long run. In most scenarios, the operation pays off by selling the recycled materials. Only when the amount of returned batteries is low, moderate gate fees or economic incentives by policy makers would be required.

Recycling lithium-ion traction batteries is expected to contribute decreasing the environmental impact of electric vehicles. Recycling might not only help reducing the amount of primary material required to be supplied to the battery industry but also preventing landfill and incineration activities. Nevertheless, recycling does not imply per se an environmental benefit as its impact is affected by different issues such as the quality of the material recovered, the energy and material consumption by the process itself and the efforts caused by the required logistics. This chapter presents an analysis of the most relevant aspects of the recycling process of lithium-ion batteries from an environmental perspective. It first introduces a framework to understand the different ways in which a recycling industry might affect the environment. This framework is further applied to describe the potential environmental effects of recycling traction batteries. Using primary data, we conducted an energy and materials flow analysis of the process developed within the LithoRec project. Finally, we discuss the results of the life cycle assessment (LCA) performed within the context of the LithoRec project and identify key issues to be considered in order to develop recycling processes that contribute to develop an environmentally consistent recycling strategy parallel to the rising traction battery industry.