43 Battery production technology | Insight E-Mobility Engineering | July/August 2024 accelerating development, mitigating risk and streamlining on-site commissioning of the line.” More on that later. Developments in battery production machinery are focused on efficiency, scalability, quality and sustainability. The implementation of a continuous process, from mixing to ageing, including the ability to track and trace individual cells in modern gigafactories, is one of the latest advances, says Jörg Rottkord, global industry manager, automotive, at Beckhoff Automation. Continuous mixing In mixing, conventional practice is to prepare electrode slurries in discrete batches, which is suited to small-scale production and custom formulations. The alternative for volume production is continuous mixing; innovations aim to achieve more uniform electrode slurries, in turn improving the quality and consistency of anodes and cathodes. The use of high-performance, twin-screw extruders is coming to the fore. “This process enables more efficient production with highest-end product quality and minimal waste. In addition, it gives manufactures high flexibility regarding recipe and the electrode production process itself, producing slurries or electrodes in a semi-dry or dry process,” says Massimo Bernert, sales manager at Coperion. “We see a growing demand in highly accurate feeding to optimise both active material production and continuous manufacturing of battery masses. The precise feeding of ingredients plays a crucial role in the process.” Two-sided coating As well as speeding up the process, advances in slot-die coating are intended to enhance precision to create electrode layers that are as uniform in thickness as possible, which improves battery performance and reduces waste. Dürr has developed a simultaneous, two-sided coating process that features a straight-path product flow through a single coating station, offering unique benefits, such as a smaller manufacturing footprint and no edge curl after drying. Bernhard Bruhn, vice-president of the lithium-ion battery global business unit at Dürr Systems, says the process consists of slot-die coating on a backing roll and tensioned-web, slot-die coating of both sides of the foil in one pass. He says the simultaneous coating process optimises drying. Air bars suspend the coated film to protect it from damage, while an even circulation of warm air on both sides creates a floating cushion effect, ensuring there is no contact with the film in the dryer. Measuring systems check the basis weight to ensure the film is completely dry. The need for post-processing steps such as smoothing is eliminated. Formation is the initial cycle of charging and discharging to form the solid electrolyte interphase (SEI) on the anode, which is critical for the battery’s performance, capacity retention and service life. A good SEI is essential to provide a combination of electrical insulation and ionic conductivity. It needs to be thin to minimise the loss of cyclable lithium ions, and mechanically stable to accommodate expansion and contraction during charge/discharge cycles. Finally, the SEI is essential to inhibit the growth of lithium dendrites that could cause internal short circuits. Gasses generated during the formation process must be discharged safely. The purpose of ageing is to ensure the electrolyte completely wets the anode, cathode and separator, and to allow the SEI layer to stabilise, and to extract residual gases before the cells are sealed. The process normally takes several weeks, depending on factors such as temperature and the formation protocol. The next step is assembly of the cells into modules and then into packs, or directly into packs in the case of cell-topack architectures. At this stage, the cells are connected in groups in series to achieve the required voltage, and these groups are connected in parallel to achieve the required capacity. While battery production can be improved with better machinery, the entire process can benefit from an extension of the digital-twin concept, according to Roland Echter at ATS Industrial Automation. “Where digital twin refers to the virtual replication of a single machine or device within a digitalised environment, ‘system twin’ is the 3D digitalisation of the entire production line at a system level, including all the individual machines and devices contained within that line,” he says. “This enables the complete system and components to be simulated in a virtual environment, driving significant time and cost savings, and speeding timeto-market for battery manufacturers by Innovations such as two-sided coating of anodes and cathodes fed from rolls speed up the manufacture of cells (Image courtesy of Dürr Systems)
RkJQdWJsaXNoZXIy MjI2Mzk4