Revealing the Assembly Design of a BYD 46120 LFP Cylindrical Cell Through Systematic Teardown Analysis

ABSTRACT A detailed understanding of internal assembly design is essential for interpreting the manufacturing logic of modern cylindrical lithium‐ion batteries. However, such information is rarely disclosed for commercial cells. Here, we reveal the assembly design of a BYD 46120 LFP cylindrical cell through systematic mechanical teardown and structural analysis. Controlled disassembly enables reconstruction of the internal architecture, including the tabless electrode configuration, engineered anode and cathode disk structures, laser‐welding patterns, and gas‐release features. The jelly‐roll assembly consists of single‐sheet anode and cathode layers supported by a separator‐core mandrel, ensuring mechanical stability during winding and cell assembly. Quantitative measurements of electrode dimensions and stacking geometry identify deliberate assembly strategies, such as an oversized anode relative to the cathode and the incorporation of an alumina‐based insulation layer on the cathode current collector. Microstructural and crystallographic analyses confirm the use of natural graphite and LiFePO 4 active materials processed via conventional slurry‐based coating. By reconstructing the internal assembly architecture of a commercial 46120 cylindrical cell, this work provides an assembly‐oriented reference for cylindrical lithium‐ion battery design and manufacturing.