Characterisation of a 4680 Cylindrical Cell: Insights Into Cell Design and Performance

Abstract

Li-ion batteries are expected to tackle the demands of powering the automotive industry shift toward electrification. Selecting the right components by considering attributes like performance, safety, and longevity is crucial. These batteries come in various forms: cylindrical, pouch, and prismatic, each with its own set of pros and cons in terms of manufacturing, packaging, energy and power. Recently, there has been a proposal for cylindrical cells of the 46xx series, which allows increased capacity, potentially making them more viable for battery packs. This project aims to provide insights into the design and electrical testing of a 4680 cylindrical Li-ion cell with a lithium iron phosphate (LFP) cathode. This cell chemistry has recently gained more interest within the automotive sector due to its cost and safety. Insights into the cell design have been obtained through a thorough cell-teardown process. Unlike prismatic cells, which typically use aluminum cans, the cylindrical cell features a steel can, presenting unique challenges during the disassembly process. To address this, two methodologies for opening cylindrical cells were developed and reviewed. Additionally, the design for the cell considered within this study differs from existing tabless architectures for 4680 cylindrical cells found in literature. The materials harvested from the cell teardown were characterized to obtain information about the cell components, such as electrodes, electrolyte, separators, tabs, etc. Furthermore, electrical testing methods such as galvanostatic charge and discharge, hybrid pulse power characterization, and electrochemical impedance spectroscopy (EIS) provided additional valuable insights into cell performance. This study contributes to the benchmarking of 4680 cylindrical cell series, which are otherwise scarcely documented in literature.