Actually, the base technology of this electric battery is not new. Sulfur-sodium (NaS) batteries were originally developed by the Ford Motor Company in the 1960s.. A few decades later, this technology was sold to the Japanese company NGK, who now manufactures battery systems for stationary applications. But Why is there talk of the new sodium-sulfur batteries?
Traditional sodium-sulfur technology
NGK Insulators company uses traditional technology, Focusing batteries for seasonal use. To understand this type of operation we must know that stationary batteries are also known as reserve batteries.
That is to say, They are designed for storing and waiting for a demand for energy caused by two possible factors: by a loss of current, by a cut in the supply of the network, which is known as a reserve situation, or regular consumption, caused by the use of the batteries at night, which is known as use stationary.
These types of batteries have a useful life period from 5 or 10 years to 25. are used in photovoltaic installationsUPS to supply computers and computing centerselevators, industrial generators, among others.
Traditional sodium-sulfur batteries work at high temperaturesfrom 300 to 350 °C, which can be an operational difficulty in case of intermittent operation. The efficiency in the charge-discharge cycle is around 90%which allows an efficient use of energy.
How does the traditional sodium-sulfur battery work?
Sodium-sulfur batteries are formed by a negative electrode of sodium and sulfur at the cathode. A beta-alumina ceramic tube functions as an electrolyte, allowing only sodium ions to pass through.
When downloaded, sodium is oxidized and sulfur is reduced to form polysulfide (Na2sx). In the loading phase, metallic sodium and elemental sulfur are recovered again. The battery operates at temperatures of about 300 °C or higher. In these conditions, when the battery is operational, both materials are in a liquid state.
To form batteries with sufficient charge density, sodium-sulfur cells are packaged in a module. In addition, we must know that the most common configuration of these batteries is for use in large installations, so 6 or more modules are assembled in a container. So, Batteries from 250 kW to 1,450 MWh are achieved.
News in sodium-sulfur battery technology
Researchers at the University of Sydney They have been working in recent years to improve this technology from the 60s of the last century. Although there is still not much information, since it is an investigation and in their scientific article they do not provide specific data, yes claim it can quadruple the charging capacity of current lithium-ion batteries.
In its scientific publication, it is stated that batteries are totally inorganic and solid state sodium-sulfur. Something that is improved on the current lead and current lithium. Thus, this research opens the door to a promising technology for stationary energy storage due to its high securityhigh energy and abundant resources of both sodium and sulfur.
Besides, current sodium-sulfur batteries have poor performance in terms of charge-discharge cycles and charge capacity. This is mainly due to its low physical contact between electrode and electrolyte, which causes a very high resistance to the passage of electrons.
Research at the University of Sydney has worked on an innovative approach to address the problem of interfacial contact. so, yese has used a carbon nanocomposite (Na3PS4-Nah2SC) as cathode for the new sodium-sulfur battery.
The Na3PS4 It is a highly ionic conductive solid electrolyte. In addition, it is an active material, ie, a catholyte, after mixing with electronically conducting carbon. This promotes interfacial contact between electrode and electrolytesince only one two-phase contact is required for the charge transfer reaction.
The introduction of sodium sulfide (Na2S) nano-structured in the nano-composite that forms the cathode, effectively improve the load-bearing capacity. The homogeneous distribution of nano-structured sodium sulfide, the solid state electrolyte of sodium (Na3PS4) and carbon in the nano-composite cathode can ensure high mixed (ionic and electronic) conductivity and sufficient interfacial contact.
The nano-composite cathode welcome3PS4-nanosified Na2S-carbon provides high discharge capacity starting 869.2 mAh g-1 at 50 mA g-1 with great cycling capacity and speed at 60°C. This represents the best performance of fully inorganic solid-state sodium-sulfur cells reported to date.
Therefore, it constitutes a significant step towards high-performance solid-state sodium-sulfur batteries for practical applications. This condition, together with its low production cost, would facilitate the amortization of self-consumption facilitiesor even in electromobility.
Advantages of the sodium-sulfur battery
In the event that this innovation can be applied to the industrial production of the new batteries, it will provide such significant benefits that it could revolutionize the current energy system. The great advantages it would bring are:
- Much cheaper batteries
The basic elements for its manufacture are sodium, sulfur and carbon. Very common elements throughout the planet and easily obtained. This would mean that there would be no monopoly on the exploitation of them and their price would be low.
In addition, it would facilitate its use in the storage of electricity from renewable energies such as photovoltaicwind or tidal power, among others.
- Less damage to the environment
Due to the ease of obtaining these elements, it would not be necessary to have large mines and its processing does not imply the contamination of water, as it does with cobalt and other rare earths.
According to the researchers’ studies, with carbon doping that facilitates contact between cell components, ion transfer is greatly improved. This means that the charging capacity could be up to 4 times that of the current lithium-ion battery.
- manufacturing ease
The elements of this new electric cell can be transformed and turned into batteries in the same factories that today produce lithium ones. This would facilitate its production on a large scale without having to create new infrastructure.