How can electrical energy be stored in liquids? Is it possible? If so, can energy also easily be captured using any type or particular types of liquid? For example, NaCl in liquefied form has sodium positive and chloride negative charged free moving ions. It can conduct electricity but storing electrical energy in it raises some questions in my mind.Can it be done? Or by other means by manipulating the liquid form.
 A: Let's say it's an extremely windy night, and you're producing much more energy than the grid uses. You can store the energy produced by the wind turbines in water as simply as lifting it high up somewhere - like pumping it from a lower dam into one that's higher, thus increasing the water's potential energy. You expend energy by pumping the water, and can then use the water to drive turbines when you need the extra energy, like during a particularly hot day when the ACs are running everywhere.
A: Another method is cryogenic energy storage where you use excess power e.g. generated by wind energy at night to liquefy air. You can then extract energy from the stored liquid air by letting it heat up which generates huge pressures that can be used to drive a turbine.
A: Absolutely. The only what you need is a reversible, first-order phase transition where the phase with the higher energy is liquid.
For example, in a <0C environment, you can store energy in liquid water. If you meld a cup of ice (store energy in it), and as it freezes down, it releases that energy. Thus it works as an energy storage. Although it perfectly unpractical for any battery-like application.
Your idea about storing energy in melt NaCl could work, but it is also impractical (although not so hardly as my example). The problems with it are that NaCl melts on 900C, and and that chlorine is a highly reactive gas, especially on 900C.
But there are similar, working battery-like applications for that with sodium and sulfur. $Na_2 S$ melts on 300C, which is already enough to make it to the border of the profitability with heat insulation. These batteries are workkng essentially by electrolizing $Na_2 S$ on charge and by the reverse process on discharge.
The reason why aren't they used as large-scale buffer power plants is that the German green energy switch became a failure, and out of them nobody has both the money and the will to produce them. The capacity of the largest sodium-sulfur battery plant  is around 150MWh and it is in Japan.
