EV batteries are expensive.  It’s the Achilles’ heel that’s keeping new electric cars unaffordable for so many – and battery prices are only going up as demand grows for raw materials such as lithium and cobalt.

So, how can electric cars get cheaper when battery costs are rising?

Carmakers like TeslaBYD and MG are already adopting the lithium-iron-phosphate (LFP) cathode chemistry which doesn’t use cobalt and nickel to be around 20 per cent cheaper than regular nickel-manganese-cobalt (NMC) packs in 2022, according to BloombergNEF.

Yet, even LFP batteries were hit by a 27 per cent price rise last year.

That’s compared to 2021, and it’s happened because of the increased demand on mining for lithium, causing an EV battery shortage – and market costs aren’t expected to come down soon.

How about these solid-state batteries we’ve been hearing about?

Yes, solid-state batteries are mooted as the ‘holy grail’ for EVs to address driving range, weight and thermal safety concerns, but they aren’t expected to come to market until at least 2025 – and it’ll be even longer before they’re a properly affordable proposition.

Enter sodium-ion (Na-ion) batteries.

What do sodium-ion batteries contain?

Na-ion batteries are home to sodium in the cathode (positive terminal), sodium in the electrolyte (separator), and hard carbon to make the anode (negative terminal). On each electrode side, there’s an aluminium current collector for both the cathode and anode.

The anode’s hard carbon material allows a broader range of available electrolytes, resulting in a wider operating temperature range is possible and ultimately makes it safer to use.

In comparison, lithium-ion (Li-ion) batteries use lithium in the cathode and electrolyte, with graphite comprising the anode. For the outer electrodes, it adopts an aluminium current collector for the cathode and a copper collector for the anode.

Na-ion batteries have a similar construction and share alkali metal properties with Li-ion batteries, albeit slightly heavier and bigger.

How are sodium-ion batteries cheaper?

Energy density∼100-150Wh/kg, with potential to go beyond 200Wh/kg∼150Wh/kg for LFP, up to 275Wh/kg for NMC cathodes
Battery pack costN/A – expected to be 20 to 40 per cent cheaper than Li-ionAU$213 per kWh (2022 average)
Operating temperature-30°C to 60°C15°C to 35°C
SafetyLower thermal runaway risk; can be transported with no risk as it can be fully dischargedThermal runway risk; cannot be under 30 per cent during transportation
RecyclabilityLess raw materials included; simpler recovery processSeparating metals needed; more complex process

*Note: Data collated from C&EN research, BloombergNEF, Faradion, pv magazine, Digitimes Asia, and Ecotreelithium

Sodium is expected to be up to 40 per cent cheaper than lithium due to the abundant availability of sodium supply and lower extraction and purification costs.

Critically, it lacks expensive raw and unsustainable materials such as lithium, cobalt, copper and graphite – which are in short supply due to slow mining processes not keeping up with the strong demand.

When will EVs feature sodium-ion batteries?

Na-ion batteries are already being produced, but the questions is when they’ll debut in electric cars.

Cheaper manufacturing costs and the initially lower energy density – if comparable to LFP packs – means they’ll be found on smaller, more affordable entry-level EV models.

Chinese automaker Build Your Dreams (BYD) is rumoured to debut a Kia Picanto-sized BYD Seagull electric micro car using sodium-ion tech in base variants this year, as well as introducing it on the Dolphin small hatchback.

British startup Faradion has been developing sodium-ion batteries since its inception in 2011. Its batteries are already in production, with the first commercial energy storage battery installed in Australia late last year.

Meanwhile, the world’s largest EV battery maker Contemporary Amperex Technology (CATL) already released its own Na-ion batteries in 2021 and plans to ramp up production this year.

Although lithium-ion battery prices have increased, sodium-ion batteries are proving to be the new solution to reduce manufacturing costs, rely less on environmentally unsustainable materials, and offer better thermal safety to ultimately lower the cost barrier to electric vehicle adoption.

Extracted in full from: What are sodium-ion electric car batteries? (whichcar.com.au)