battery life would need many changes. Phones are honestly doing really good considering what in the current leader in phone technology, The Galaxy S4.
But the demand for thinner phone but bigger screen is the most direct cause of shit for battery life. Naturally the best solution for now is simply to carry a spare battery, But if people could be convinced that just a bit thicker is not bad we could get more time out of the phones.
Laptops last so long because of SSDs and the fact the longest running models have most of their mass made up of battery.