This is a Battery-Pack for Lego Power Functions which uses Li-Ion 18650 cells.
Battery holder:https://de.aliexpress.com/item/5-pcs-lot-7-4V-Plastic-2-pcs-Standard-Size-18650-Battery-Storage-Case-Holder-With/32825974161.html?spm=a2g0s.9042311.0.0.3ygReR
switch:https://de.aliexpress.com/item/R251-Free-shipping-10pcs-mini-Pull-switch-snap-switch-with-bracket-3-foot-2-file-handle/32691501327.html?spm=a2g0s.9042311.0.0.3ygReR
