All of the electricity storage solutions available right now for commercial use are chemical types. For end-users, batteries are the only storage option that is available widely, and they are pretty convenient too. The small AAA or AA batteries fit almost in any electronic equipment and probably the most efficient type of energy storage option available today. But even the more advanced and famous lithium-ion batteries, again a type of chemical type, are prone to the same disadvantages in the category.
Since solar power is becoming more economical, one primary disadvantage is that solar plants only provide with power during the daytime, and are completely off at night. Thus, the grid or homes using solar power require some kind of storage solution. To push the world being powered from 100% renewable energy, efficient storage solutions are very important and critical.
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Storage capacity fade issue, limited number of useful cycles, critical safety circuits to avoid overcharging and discharging along with a potential of catching fire to name a few. The chemicals used in the batteries also, during their lifecycle from being produced to being disposed of, cause damage to the environment.
To combat these issues, multiple other companies are trying to come up with a physical storage solution that doesn't require any chemical reaction to release or store energy. These solutions use the changes in physical forces and properties to store and generate energy. One such solution is the gravity well, where energy is used to raise dead weights at a certain height and lowered over a pulley, connected to a generator that generates electricity from gravitational force. Another such solution is freezing purified air into the liquid using industrial refrigerators and then allowing it to again expand back to gas, and using the energy released during this process to drive generators.
As you can see all the types of physical storage options, use energy or electricity precisely to store energy in a physical form of force like potential energy and then convert it to electricity when required.
Advantages of Physical electricity storage solutions over Chemical storage:
They don't face capacity fade issue over life
Much more long useful life compared to chemical storage
Safe on the environment, don't use harmful chemicals
Don't require complex safety circuits to limit the charging or discharging cycle
No risk of catching fire
Disadvantages of Physical electricity storage solutions over Chemical storage:
Low energy density, requires much more space for a similar capacity storage solution
Not as quick starting as chemical types, but can be coupled with chemical-based storage to provide uninterrupted power
Unviable for home-based or smaller sized operations