All batteries have essentially the same components: electrolytes, positive and negative terminals and separators integrated into 'cells'. Battery types are differentiated primarily on the basis of the nature of the material from which its components are made. The most important component of a battery is the electrolyte. Mostly, a battery is differentiated on the basis of the nature or technology of its electrolyte or any other of its core chemical components.
In a saltwater battery, saltwater produced from seawater or made by saturating water with salt, is used as the electrolyte with sodium as the main conductor. Unlike the traditional battery technologies, these batteries are manufactured using entirely non-hazardous materials, like saltwater, carbon, and manganese. This makes them easy to recycle, transport and handle and friendly to the environment. They have the mark of being the safest types of batteries because they are non-inflammable; they do not pose any danger of explosion or the release of toxic chemical gases and fumes.
Pros
1. Safest Battery Technology So Far
With saltwater as their electrolyte, they pose no fire or explosion risks. in their system. As a result, there is no fire risk. They are manufactured using entirely non-hazardous materials, like saltwater, carbon, and manganese. This makes them safe to handle, transport and easy to recycle. They are the only batteries in the world to achieve ‘Cradle to Cradle' certification.
Since they are non-flammable and entirely without the risk of explosion, they can be used beyond the indicated cycles without any fear of explosion.
2. Easy to Recycle
Recycling reduces waste, prevents pollution, and benefits the environment in many ways. As they do not use heavy metal chemical materials, they are easy to recycle. The absence of harmful chemicals or material requiring special instructions to dispose makes them very easy to dispose.
3. Higher Depth of Discharge
Saltwater batteries can endure a 100% depth-of-discharge capability.
4. Maintenance-free
Saltwater batteries can endure a 100% depth-of-discharge capability without any damage to the battery. Also, fully discharging the battery does not affect the life cycle of the storage system. In addition, the battery can stay in storage for weeks or days without charge and without the need for maintenance.
5. Eco-Friendly
Heavy metals mined are required to make other types of batteries. Extracting those materials harms the ecosystem. Saltwater batteries eliminate the political tensions that have aggregated around mining heavy metals to meet the demand for renewable energy sources.
Cons
1. Low Energy Density and Immense Size
They have a very low energy density. They store lesser energy in the same amount of space. Due to the lower energy density, there is a demand for larger sized batteries. The larger the batteries are, the more the materials for making them are required. This explains why they come in very large bulks.
2. Low 'C' Rating
They have a low 'C' rating, the lowest of all battery types. A “C” rating is simply a battery’s capacity when discharged over a specific period of time. Learn more here. With 'C' rating of 0.5, they can discharge to half of their capacity at once.
3. Expensive
Since saltwater batteries have a low energy density, larger batteries are required as is more materials for their production. With high manufacturing costs come high purchase costs. At the present, this is the greatest challenge to the mass production of saltwater batteries. In comparison, the costs for making lithium-ion and lead-acid batteries have been in steady decline.
Also, saltwater batteries have a faster degradation rate than Lithium-ion batteries. They are also less efficient than Lithium-ion batteries. Their output have been described as low and inconsistent [here].
Regardless of its great promise, the first and only venture into introducing saltwater batteries into the solar industry ended in a failure. The first and only company so far to take up the challenge of mass-producing saltwater batteries, Aquion Energy. After raising up to $190M from investors including Bill Gates' Microsoft, Aquion first offered saltwater batteries in 2014 at insanely high prices. In 2017, Aquion filed for voluntary bankruptcy. It emerged from bankruptcy and was sold to China Titans in 2017. Afterwards, it effectively disappeared from the radar and with its disappearance came the disappearance of saltwater batteries.
However, due to its great promises, interest in the battery technology remains and continues to grow considerably. At the present, the greatest challenge to the scaling of saltwater battery technology is the steady decline in the production costs of lithium-ion batteries. This makes it difficult to speak of their future with any optimism.