Structural batteries for aircraft - and how about as part of smart electricity grid?
I'm sure BAe Systems, as an aerospace company (civil as part of the Airbus consortium, and military too) is probably thinking mainly about airframe components that serve a dual purpose especially as part of a highly expensive capital item where upfront cost can to some extent be traded for weight/future-fuel savings/performance in terms of additional batteries and or other means of electrical generation from a jet aircraft (alternators in jet engine rotating parts or Thermo Electric Generators maybe)
In some cases total required battery capacity may be modest while the amount of aerodynamic structural real estate might be huge. Consideration of safety might also rule out certain efficient battery types that could be subject to thermal runaway like some infamous laptop batteries of the past.
Potentially, as part of a smart electricity grid, buildings with very cheap batteries (or supercapacitors) incidental to their structure could, combined with electric vehicles, provide distributed storage for time-varying renewable supplies such as solar and wind to provide for peak demand when it could be economically viable to sell back to the grid at a premium and to provide backup facilities locally for computers and emergency lighting if there's a power cut due to a line fault elsewhere. For this to work, though, it would have to add virtually no cost to the structure of the building. With electric vehicles, the battery cost factor isn't so important as they require a battery anyway as part of their primary function.
A good analogy for a smart grid is, if my Electric Car in the year 2030 has a 180 mile range left while I'm parked up and plugged in at work and knows I plan to drive 30 miles that evening (my smartphone will keep it informed of my plans and guess the likelihood I'll make a trip on impulse), it might sell back premium-priced peak demand electricity to the smart grid leaving me with no less than 90 miles and only eat into the 60 miles of buffer range if the price premium increases to compensate me for the chances I'll have to take a diversion before getting home and charging up on low-cost, sporadic off-peak electricity when it's cheap enough.