تولید سلول های لیتیوم یون در منطقه بزرگ - پیش شرطی سازی، سلول انباشته و تضمین کیفیت

In times of climate change and shortage of fossil fuels, electro mobility provides a clean and sustainable solution. The growing number of electric vehicles generates a huge demand on lithium-ion cells. Due to higher quality requirements and different conditions of operation compared to consumer cells adapted production processes and systems are needed. Consequently, this paper analyses the process chain for lithium-ion cells and proposes solutions for the automation of important process steps suitable for mass production, in particular the pre-conditioning of the electrodes and the cell stacking. Additionally, an approach for the detection of particles on electrode surfaces is presented.

The reduction of greenhouse gas (GHG) emissions is the answer of most governments to climate change. Furthermore, alternatives for fossil fuel applications need to be found due to its future shortage. In terms of vehicles for individual mobility, the substitution of the internal combustion engine (ICE) by an electric drive train provides a solution for both issues [1]. On the one hand, battery electric vehicles (BEV), like the MUTE shown in Fig. 1, do not emit GHG. On the other hand, the high well-to-wheel efficiency of electric vehicles reduces the carbon footprint. If a BEV is charged with electricity entirely made from renewable energy sources, there will be no GHG emissions at all in the utilization phase of the vehicle. Consequently, electric mobility is promoted in many countries, so that automobile OEMs have begun to include electric vehicles, such as BEVs, in their product ranges. The increasing number of electric vehicles in these days and the prospective market penetration leads to an enormous demand in energy storage solutions for electric vehicles. Focusing on BEVs, lithium-ion technology will be the preferred solution for this decade, mainly motivated by the energy density provided by corresponding battery systems. Nevertheless, current automotive lithium-ion battery systems store approximately two magnitudes less energy than fuel tanks of medium-sized ICE vehicles. Cell manufacturers have proclaimed a target value for the specific energy of lithium-ion cells of about 250 Wh/kg. Despite electrochemical improvements, it is a production engineering challenge to increase the energy density of the cells. In general, large lithium-ion cells are predicted to be the first choice for automotive applications, since they provide higher energy densities accompanied with fewer assembly operations on battery level. The energy density of the cell is influenced by the coating parameters, the cell assembly process and the cell housing. This paper focuses on the cell assembly, which entails several challenges in the field of process design, preconditioning as well as quality assurance. Chapter 2 compares the available variants of large lithium-ion cells and their properties. The process chain for large lithium-ion cells is detailed in chapter 3, which provides the basics for the following chapters focusing on single process steps and quality measures investigated at the iwb.

Electromobility is a significant future trend. Energy storage, as one of the key issues, is provided by large battery systems. For the battery cells, production processes for small geometries already exist. Large area cells require enhanced production processes. At the iwb, the automation of two important process steps, cell stacking and preconditioning has been implemented and investigated. The novel z-folding process enables continuous separator processing and gentle handling of single electrodes. Laser cutting of the electrodes provides flexibility and can become an economic alternative to mechanical cutting. Particles on the electrode surfaces have a harmful influence on the cell performance and must be avoided. A system for the optical detection of small particles has been built up. In order to decrease the detectable particle size, other methods like thermographic inspection have been investigated. In the near future the complete production chain for lithium-ion cells will be implemented at the iwb. Thus, every single process step and its effect on the cell quality can be evaluated by aging and testing cells produced with defined process parameters. Additionally, the existing systems have to be advanced in order to increase their economic relevance. The final goal is to establish a complete and powerful production chain for lithium-ion battery systems.