Forget other phones, buy xperia z3 and after 8h at work with a good use( facebook, music on headphones for 3h, and 20 minutes calls) you will still have 65-70% battery but with one condition : 40% brightness which is more than enough inside.
On top of fabulous battery life you get a sleek design, 20mp decent camera, 2.5ghz quad cpu, 3gb ram, 16( 10) gb rom, microsd card slot up to 128gb, dust and water protection and virtually no lag even if you got all your aps open on the same time in the background( tried with 47 apps, good memory management in lolipoop 5.1.1) , so think about before you buy!
