The Samsung Galaxy S25 Edge is only 5.8 millimetres thin, which requires compromises in terms of features: the high-end smartphone lacks a telephoto camera and the battery is very small at 3900 mAh. Nevertheless, the 6.7-inch device still proves to be quite durable.https://www.notebookcheck.net/Verdict-on-the-Samsung-Galaxy-S25-Edge-Extra-thin-smartphone-lasts-longer-than-expected.1044177.0.html
Samsung increased the density on these batteries and it is the same upgraded technology they will use on the Z7. This might be due to using the stainless steel casing.
Samsung should have included a higher density silicon carbon battery with the edge. Oh well, maybe next year