Do they technically actually do get lighter? Since it's a solid-state battery, nothing is actually moving outside the battery (the ions move from one electrode

Do they technically actually do get lighter? Since it's a solid-state battery, nothing is actually moving outside the battery (the ions move from one electrode to another, but they remain within the battery while charging/discharging) and because of law of conservation of mass, the weight should stay the same. But I'm no battery expert, maybe someone knows better.