Mazda has announced what is considered the holy grail of petrol / gasoline engines, the Homogenised Charge Compression Ignition engine.
The engine will be introduced into Mazda production cars from 2019. A 2 litre HCCI engine is claimed to be as powerful as a 2.5 litre engine with the economy of a 1.5 litre engine. The engine burns a much leaner charge than it is possible to ignite with a spark, and has much higher combustion pressures which generate more power than conventional spark ignition engines for the same amount of fuel, and much lower emissions than current petrol or diesel engines.
https://www.youtube.com/watch?v=9KhzMGbQXmY
Looks like carrying batteries around will soon be a thing of the past.