The South Korean battery behemoth LG Energy Solutions and automotive giant Hyundai Motor Group are mulling over the adoption of the ‘Z-stacking’ method for their electric vehicle batteries joint venture in the US, according to announcements made earlier this month. The two conglomerates could make the switch as early as next month, following the successful deployment of the same technique in their first battery joint venture, HLI Green Power in Indonesia.
The Z-stacking method, a unique assembly process technology, is one of several developed by LG Energy Solutions, others being ‘single lamination’ and ‘direct stacking’. The method, however, is a frontrunner for large-scale mass production. Stacking refers to a layered arrangement of battery components such as cathodes, anodes, and separators. The eponymous ‘Z’ in Z-stacking comes from the folding pattern of the separator between alternating layers of anodes and cathodes.
LG Energy Solutions has been known to favour ‘lamination & stacking (L&S)’ technology for the Ultium Cells joint venture with General Motors (GM). However, Hyundai Motor Group’s decision in 2021 to adopt Z-stacking, instead of L&S, has marked a shift in the approach.
The proprietary version of Z-stacking used by LG Energy Solutions, Advanced Z-stacking (AZS), or ‘Ajis’, as it is colloquially referred, has been noted for its process speed enhancements, overcoming a traditional disadvantage of the Z-stacking method.
Both L&S and Z-stacking offer their unique benefits and challenges. While L&S trumps Z-stacking in productivity and can boost capacity by optimising internal battery space, it faces potential issues during the lamination process, including misalignment of the separator. An Advanced L&S (ALS) variant, called ‘Als’, has recently been developed to tackle these issues.
Ninetech, a supplier of AZS equipment, is expected to gain significant traction in the battery assembly process equipment business with the increased adoption of AZS. LG Energy Solutions has been operating a dedicated team since last year to enhance the technical proficiency of AZS under the leadership of managing director Kim Ki-tae.
Industry insiders note that up until now, electric vehicle battery technology has been predominantly guided by battery cell companies.