My brave nature is level level 94 and have 117 in it's speed stat. it also have 0 evs and iv in its speed stat.
the website say his Min stat should be 112 in speed.
have I done something wrong?
The minimum is 113, and if it's 117 it is either a glitch or you have at least a few IVs or EVs in speed. If you battled with it before, chances are you have a few EVs on there.
If you want a minimum speed Aegislash, yes. You've done something wrong.
Nature is fine, you either picked up some unwanted Speed EVs from wild Pokemon battles or have extra speed IVs.
Source: Tested minimum speed on PS!, here.