The future of electric helicopters and other electric-powered transportation devices lies in super-capacitors or ultracapacitors. These devices have the potential to utterly revolutionise electric power as a power source that can compete with fossil fuels.
However, the breakthrough technology is still just an arm's reach away... but it's not impossible, and it's not alchemy.
Australia's CSIRO was in the forefront of super-capacitor development in the early 2000's, but has gone quiet on it, in recent times. I suspect that it's all due to substantially higher amounts of research money needed, than the Australian Govt is prepared to commit.
The other angle is that this Holy Grail is encouraging companies such as the Texas-based EEstor, who are supposedly producing breakthrough ultracapacitors, but who are essentially making claims they cannot support with actual commercial products.
The breakthrough is supposedly in the relatively-newly-discovered ultracapacitor insulation material, barium titanate. However, converting excellent lab test results involving barium titanate into commercial products seem to be eluding EEstor... who still claim, however, to have an outstanding commercial breakthrough.
Until the day comes when that "outstanding commercial breakthrough" with ultracapacitors happens... and can be displayed as a commercial, sustainable result... companies such as EEstor will continue to generate excitement (and continue to bleed investors), without producing anything that can be considered a major breakthrough.
I have no doubt that that day will come, and it's not far off. However, it will take more money than EEstor has, or is currently allocating to research (knowing full well that companies such as EEstor are happy to rate directors substantial entitlements, and luxury company vehicles, as higher priorities than actual research expenditure).
Supercapacitor "battery" could lead to instant charging, long charge life