No, they say it takes heat to recharge the thing. That's where the energy comes from.
But, it does sound at lest potentially promising as a storage mechanism, and portable, rechargeable source. Provided it holds more and weighs less than batteries.
Usefulness also would depend on the efficiency of the conversion of the heat to the stored energy.
Everything that I have read says that it isn’t but that it is in the same vein as a perpetual motion machine. Basically it breaks the laws of physics.