Unfortunately, I'm mostly on the supply side of the battery equation, consuming those few PDFs that are smuggled out.
The most surprising thing, to me, is that battery tech moves in a zig-zag shape. The best battery that money can buy, for two of pretty much the most important applications (can't elaborate further, sorry) was only made from ~2012 until ~2014. A lot of really expensive things that need that battery are now running off of old stock, which will of course eventually run out. The best comparable battery made in 2016 has less than half its performance.
Another example of this is energy density. For practical purposes, the best density you could reasonably buy was fixed around 90 Wh/kg for a while (until about 1997), then suddenly jumped to ~180 Wh/kg (~2002), then went in 2006 to ~260 Wh/kg... and sat there, where it has sat for eleven years now with practically zero improvement. [0] If I teleported to today from 2006 I'd expect to have some fantastic 400 Wh/kg batteries that would enable all kinds of new technologies... but nope, the best energy density you can get is literally the same as it was eleven years ago.
Worth noting that since 2006 discharge rates of high capacity batteries have gone up, to be perfectly fair. Still though, energy density remains stagnant.
[0] Looking at graphs on Google Images will give you the wrong idea. They typically show the best batteries that year, not necessarily ones you can actually buy, and the numbers are often pulled out of thin air. This graph [1] is the least worst, but that's not saying much.
[1] http://media.greenmonk.net/greenmonk/files/2015/11/Li-IonDen...