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This 9v battery contained six cells stacked like a layer cake
(lemmy.sdf.org)
Picture of a disassembled Duracell 9v battery. Below the terminal assembly is a clear plastic case where you can see six sets of stacked rectangular terminals and fillings.
On older laptops they used cylindrical cells too. On mine, you can clearly nake out the shape of the housing on the removable battery.
Used to repurpose the individual cells of laptop batteries for ecig batteries. The cells were 18650s, same as most customizable ecig mods use.