Three battery technologies that could power our future

The world needs more power, preferably in a form that’s clean and renewable. Our energy-storage strategies are currently shaped by lithium-ion batteries – at the cutting edge of such technology – but what can we look forward to in years to come?
Let’s begin with some battery basics. A battery is a pack of one or more cells, each of which has a positive electrode (the cathode), a negative electrode (the anode), a separator and an electrolyte. Using different chemicals and materials for these affects the properties of the battery – how much energy it can store and output, how much power it can provide or the number of times it can be discharged and recharged (also called cycling capacity). 
 
Battery companies are constantly experimenting to find chemistries that are cheaper, denser, lighter and more powerful. We spoke to Saft Research Director Patrick Bernard, who explained three new battery technologies with transformative potential.
 

Sodium-ion

WHAT IS IT?
The way that sodium-ion (Na-ion) batteries work is similar to lithium-ion (Li-ion) batteries; as the name suggests, the main difference is the replacement of lithium by sodium. A variety of sodium-based materials can be used as the battery’s positive electrode, which is decisive when it comes to performance - longer life or cycling capacity for example.
 
WHAT ARE ITS ADVANTAGES?
Na-ion batteries offer numerous advantages. The main one is that they are cheaper than Li-ion batteries (by up to 30 per cent per cell). However, this technology will not be able to compete with Li-ion in terms of energy density – neither by weight nor volume – and could only be used for stationary applications where this is not a major requirement. These might include storing excess electricity generated by renewable energy sources such as solar or wind power.
 
WHEN CAN WE EXPECT IT?
Many of the cell components and manufacturing processes are the same as for current Li-ion batteries. The main development is focused on electrode materials. Na-ion batteries might be ready to enter production in three to four years’ time.
 

Lithium-sulfur

WHAT IS IT?
In Li-ion batteries, the active materials are layered between the lithium ions in stable host structures during charge and discharge. In lithium-sulfur (Li-S) batteries, there are no host structures. While discharging, the lithium anode is consumed and sulfur transformed into a variety of chemical compounds; during charging, the reverse process takes place. 
 
WHAT ARE ITS ADVANTAGES?
A Li-S battery uses very light active materials: sulfur in the positive electrode and metallic lithium as the negative electrode. This is why its theoretical energy density is extraordinarily high: four times greater than that of Li-ion. That makes it a good fit for the aviation and space industries.
 
WHEN CAN WE EXPECT IT?
Li-S technology needs further research and development work to improve its life expectancy and to continue to increase specific energy density. It is not expected to be ready for applications requiring long battery life for at least five years.
 
 

Solid-state

WHAT IS IT?
Solid-state batteries represent a paradigm shift in terms of technology. In modern Li-ion batteries, ions move from one electrode to another across the liquid electrolyte (also called ionic conductivity). In all-solid-state batteries, the liquid electrolyte is replaced by a solid compound which nevertheless allows lithium ions to migrate within it. This concept is far from new, but over the past 10 years – thanks to intensive worldwide research – new families of solid electrolytes have been discovered with very high ionic conductivity, similar to liquid electrolyte, allowing this particular technological barrier to be overcome. 
 
WHAT ARE ITS ADVANTAGES?
The first huge advantage is a marked improvement in safety at cell and battery levels: inorganic solid electrolytes are non-flammable when heated, unlike their liquid counterparts. Second, it permits the use of innovative, high-voltage high-capacity materials, enabling denser, lighter batteries with improved safety performance and better shelf-life as a result of reduced self-discharge. As the batteries can exhibit a high power-to-weight ratio, they may be ideal for use in electric vehicles.
 
WHEN CAN WE EXPECT IT?
Several kinds of all-solid-state batteries are likely to come to market as technological progress continues. The first could be solid-state batteries with graphite-based anodes, bringing improved energy performance and safety. In time, lighter solid-state battery technologies using a metallic lithium anode should become commercially available.