An e-cigarette battery can come in many forms, shapes and sizes. Some can look remarkably similar to a ‘real’ cigarette and some can look nothing like a cigarette. The ones that depart from the traditional look of a cigarette do so for functionality – they provide much longer battery life as they are larger and can store more energy.
Always read all of the safety instruction for each battery prior to use – it should be treated with care. It is a storage of electrical power and it could be dangerous if mistreated.