Safe, Sustainable Discharge of Electric Vehicle Batteries as a Pre-treatment Step to Crushing in the Recycling Process

• Main Author: Nembhard, Nicole
• Format: Others
• Language: English
• Published: KTH, Kraft- och värmeteknologi 2019
• Subjects: Energy Systems; Energisystem
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255597

According to the Intergovernmental Panel on Climate Change, an increase in global temperature to above 1.5°C can be halted but would require immediate intervention to reach net zero emissions in the next 15 years. This intervention would have to make use of sustainable energy technologies such as net-zero carbon systems for automobiles. Electric vehicle (EV) use is set to increase 3000% between 2016 and 2030. Due to the inherent toxicity of the chemicals within Li-ion batteries, they must be recycled to be sustainable. Recycling using energy recovering, hydrometallurgical process reduces greenhouse gas emissions. However, due to the high energy and power density within EV batteries, discharging the batteries is an important safety step in the pre-treatment process. There is no industry standard for discharging EV batteries. Many processes are suggested in literature with little information as to the methods used. The aim of this thesis is to explore four processes that could be suitable for industrial use. A suitable process should be ‘safe’, meaning it reduces the risk to the facility by minimizing the fire or explosion hazard, minimizes or eliminates human interaction with the battery pack and limits voltage rebound of an individual cell to 0.5V. The process should also be ‘rapid’, meaning it ensures that discharging does not become a bottleneck in recycling, ‘sustainable’ meaning it has no polluting fluid waste streams and ‘feasible’ that is, is cost efficient. Three processes were found effective. The first, is a combination of salt-solution and metal powder discharge methods using sodium carbonate and steel. This method is intended for battery packs and modules of less than 500V at 0% SOC. The second, is energy recovering electronic load discharge for battery backs greater than 500V or at greater than 0% SOC.  Finally, inductive, wireless discharge with BMS ‘override’ is suggested. This method is suitable for future battery packs of all sizes equipped with wireless charging technology.