American and British researchers race to find the greenest alternative to lithium-ion batteries
Earlier this year, we reported on how researchers at Stanford University in America had developed an aluminium (Al-ion) battery that could rival the lithium-ion (Li-ion) batteries currently used in electric vehicles (EVs).
It has since been revealed that Sheffield-based Faradion has developed another solution – a sodium-ion (Na-ion) battery.
Why do we need to replace Lithium-ion batteries anyway?
While sales of EVs are on the rise, they are still lagging behind petrol and diesel alternatives, which outstrip them by 50 to one.
This is due to the high price of EVs, which is largely down to the cost of producing and housing Li-ion batteries.
Li-ion batteries need to be encased inside a heavy shield to minimise the risk of fire. An Al- or Na-ion battery would not need this casing – therefore they could be produced cheaper.
Sodium vs aluminium – head to head
| Sodium (Na) | Aluminium (Al) |
|---|---|
| Easy-to-source base materials | Inexpensive materials |
| Can be transported in a totally discharged state | Lightweight to transport |
| Sodium salts are abundant (6th most abundant element in the earth’s crust) | Aluminium is abundant (3rd most abundant element in the earth’s crust) |
| 140 to 150 watt-hours per kilogram. (On track to increase this to 220 Wh per kg by 2017.) | 40 watt-hours per kilogram |
| After 1,000 cycles, the battery still delivers 93% of its original energy capacity. (Equal to lithium-ion.) | After over 7,500 cycles, Stanford’s battery had no capacity loss |
| Sodium is environmentally benign | Aluminium can be recycled repeatedly. Its flexibility means it can be recycled for several different uses. |
| Heavier than Li-ion batteries | Lighter than Li-ion batteries |
It seems that while Na-ion and Al-ion both hold advantages over the Li-ion batteries currently used in EVs in most areas, they are both still lagging behind on power.
Indeed, Elon Musk tweeted shortly after the news broke of Stanford’s Al-ion battery:
Musk identified the major flaw of the Al-ion battery, which can also be applied to the Na-ion battery.
In defence of their Al-ion battery, Stanford chemistry professor Hongjie Dai suggests a solution:
‘Improving the cathode material could eventually increase the voltage and energy density.’
For the UK sodium camp, Faradion’s researchers are hoping to optimise the active materials in their battery through enhanced particle size distribution. They are also exploring ways to improve porosity and other electrode properties. So far, they are closer than Stanford in bringing an alternative battery in line with Li-ion capabilities.
However, there are drawbacks of the Na-ion battery as outlined in the table above, notably weight and the shorter charge cycle than Stanford’s Al-ion counterpart.
Who’s your money on? Let us know in the comments below.