Cars powered by table salt, you say?
Developments in electric vehicles and battery storage are rapidly helping the transport and energy markets move away from climate damaging fossil fuels.
But these technologies currently rely, for the most part, on a rare and expensive metal called lithium. It is a key component in energy storage and in recent years, demand has skyrocketed.
By 2025 lithium demand is expected to increase to approximately 1.3 million metric tonnes of LCE (lithium carbonate equivalent) – over five times today’s level. Much of this surge will come from a high demand of new electric vehicles.
It’s true that the auto industry will benefit from economies of scale; as more cars are built the more efficient and less polluting the manufacturing process should be. In addition, as more batteries are created for these electric vehicles, it will create a market for the recycling of these storage devices, thereby reducing the need for new mining endeavours.
However, a cheaper and resource-saving alternative to lithium-ion cells is needed and could be on the horizon.
For the past two decades, the performance of sodium-ion batteries has lagged behind that of lithium-ion batteries. But sodium could play a huge part in helping the world transition, even more sustainably, to a low carbon economy.
The two alkali metals lithium and sodium are chemically very similar. Although sodium does not have the energy density of the comparatively rare lithium, it is widely and cheaply available. Sodium-ion technology crucially does not consume any scare resources. In fact, it can actually be produced with simple table salt.
A South Korean sodium-ion battery managed to handle about 500 complete charging cycles before its capacity dropped to 80%. A battery with a slightly different chemical structure devised by a US-Chinese research group achieved 450 charge cycles with a similar charging capacity. And a Chinese sodium-ion battery had a slightly lower capacity, but still retained 70% of its capacity after 1,200 cycles of quick 12-minute charges.
All this may not sound like much, but in practice these batteries would probably survive many more charge cycles, because in everyday life batteries tend to be only partially charged and discharged. The complete loading and unloading of a battery in an experiment puts much more strain on the cell.
Sodium does have disadvantages. Firstly, it is three times heavier than lithium, so sodium-ion batteries are also heavier, even though lithium accounts for less than 5% of the total weight of a battery.
In addition, sodium batteries are less powerful because they inevitably lose around 10% of their energy density due to a 0.3-volt lower cell voltage. This is largely because the graphite anodes that have been used up to now in batteries absorb too little sodium.
But nanoscale carbon could come to the rescue here. A study by German and Russian researchers found that double layers of the wafer-thin carbon, graphene could store significantly more sodium atoms in the anode than the graphite used so far. They found that if graphene electrodes were to be incorporated into lithium batteries instead of the graphite anodes commonly used today, it might be possible to achieve significantly higher storage capacities.
“It’s like putting small balls between two sheets of paper,” explains HZDR physicist Dr. Arkady Krasheninnikov. “If you stuff more and more balls in, the sheets of paper are pushed apart, leaving more space between them.”
It will be some time before sodium-ion batteries reach a stage of technical maturity and can be produced in large quantities and installed in electric vehicles or mobile phones. But when that does happen, the changeover from lithium- to sodium-ion batteries should be largely unproblematic due to the fairly similar technology involved.
Electromobility is still a nascent market. It requires market demand to bring down costs and improve efficiencies. These vehicles are still more expensive than their fossil fuel guzzling counterparts but second hand vehicles are a great option. Costs in the next two years will come down dramatically so hold tight if you can’t afford one yet.
In the meantime, if you have a car that uses petrol or diesel try and limit its use. Take the train, share rides, walk, cycle. Although the systems will change eventually, we need to make sure what we’re doing today – right now – is not exacerbating climate change.
We can’t sit back and wait for the technologies to catch up with the emergency, we can do something about it today. It’s not your fault that you’re driving a car that’s not good for the environment: it’s cheaper – it’s all that’s been available for many decades – but it is your fault if you don’t reflect on that and try to change your habits for the sake of the planet and your health.
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