Battery charger fundamentals
On the output of your PFC you will need an isolated DC-DC converter for safety reasons.  An LLC resonant converter would be one approach, due to the high efficiency and pre-regulated 400V input.  Be sure to follow all the regulatory requirements for isolation/creepage/clearance etc.

Here's an example of a PFC-LLC design that's very close to your requirements: PFC-LLC design

Next you will need a charge controller capable of charging your battery.  Here's an example of a design: 48V Li-Ion charger

You can read all the application notes from the main players in power management to get a better idea of what's required.  It's not a simple task to go from a non-isolated PFC output to a battery charger, so you might want to get some help if you haven't done offline power before.