It’s a huge deal and it’s about reversible energy storage. Energy is neither created nor destroyed, but can only change state. Energy is stored in batteries electro-chemically, as opposed to just chemically, as it is in fuels such as gasoline, oil, coal, natural gas, and even hydrogen. Energy stored in batteries is fundamentally different than traditional energy carriers by the fact that electro-chemical energy stored in secondary rechargeable batteries is a reversible process, whereas energy stored in fossil fuels is a non-reversible process.
Due to the shortcomings of fossil fuels not being able to reversibly store energy, we have labeled them “sources of energy” rather than “storage of energy”, and common parlance considers fossil fuels as energy sources, rather than energy carriers, which is in fact what they are. While batteries are correctly considered energy carriers, they have the added benefit of being extremely efficient and reversible.
Fossil fuels are nothing more than energy carriers that were charged millions of years ago by energy originating from the sun, trapped in plankton and other little creatures and plants for our use today. The drawback of fossil fuel energy systems is that they are not reversible. Energy released by burning hydro-carbon chains of any type is not a reversible process, once a fossil fuel has been burned to chemically extract its heat value through reaction with atmospheric oxygen to form the products of CO2 and H2O gas, the process is in no way reversible.
So, what’s the big deal about batteries? Simply put, they are incredible in their ability to easily, efficiently, and reversibly store energy. No other portable mechanism comes even close to their ability to effectively store and return large amounts of useful energy in a controlled and reversible manor. Battery energy storage and retrieval efficiency is typically between 85-95% for a complete charge-discharge cycle, meaning that for every 1000 Watt-hours of electrical power delivered to the battery of an electric scooter or electric car, that battery will return 850-950 Watt-hours of useful energy to drive the wheels, run the air conditioner, blow the heater, and play the radio… and that is quite a big deal from which future ramifications will be enormous.