I just replaced the battery in my Nexus 5 due to earlier stages of the same issue. The battery failure was causing a lot of random device shutdowns that I had initially thought were related to the rollout of Lollipop. There's a long support thread of people with similar issues at: https://productforums.google.com/forum/#!topic/nexus/IJSOuc7... Several of the posters there noticed that their battery had started bulgin…
It's annoying really because in the end, there is absolutely NO accountability from either LG or Google that the battery won't work as expected after about two years. Thing is, the price range of the Nexus 4 doesn't exist in the Google mobile lineup anymore, with the Nexus 5 being about twice as expensive. So ultimately, I'll either have to stop buying Nexus phones or spend $400 on a Nexus 5.