Just some objective information,
When a *normal* turbocharger is fitted to a car, it's RPM when the engine is IDLING is 25,000rpm. At this level, it's making no positive affect whatsoever on the air-flow.
A GT2560R BB turbo from Garrett will rev to around 120,000rpm.
The IHI turbo from a Fiat Uno Turbo will rev to 160,000rpm.
25,000rpm is nothing.
As a point of 'efficiency', in any physical system, there are always *ALWAYS* losses. The energy required from the alternator will be larger than supplied by the "electric charger" as in improvement in power. I would also wager that at 7,000rpm the flow of air through the motor would INCREASE it's RPM so it'd actually reduce power!
Andy
PS R.O.F.L !!