Four and a half years ago, I wrote a piece about how advances in battery design were increasing the energy density of batteries. Energy density is measured in Watt-hours per kilogram (Wh/Kg). These advances had led to improvements in energy density such that Lithium ion batteries had an energy density of about 250Wh/kg, such that they could be used for all modes of transport, even aircraft. At the time there was much research going on in trying to increase that energy density even further, with one company (Innolith) suggesting it had produced a battery with 1000Wh/kg1, but that was just wishful thinking, and it turned out to be not feasible “for automotive standards”. However, they have produced Lithium ion batteries with an energy density of 300Wh/kg2. This battery uses a new battery chemistry, and is supposedly safer and has better performance due to its high voltage, high conductivity, non-flammable electrolyte (always a bonus!) that also enables an improved working temperature range of -40°C to +60°C3.
Given that four and a half years is a long time in science and technology, it seems like the Lithium Ion battery may have reached somewhere near its limit, with advances now being mooted of attaining 350-400Wh/kg3, which is not far above what is already being produced. As everyone knows, electric vehicles (EVs) are expensive, with prices for your average sized car usually being from $60,000-$100,000, and with the small sedans being at least $40,0004. One of the reasons for the generally high cost of these is the price of Lithium, which is on the market as Lithium Carbonate. While the price per US ton (about 0.9 tonne) has dropped significantly in 2023 from $US600,000 in November 2022 to $96,500 in December 2023 (due to oversupply)5.
Lithium is a relatively rare element, and despite it being estimated that the planet has about 88 million tonnes of Lithium, only about 22 million tonnes is currently recoverable. This will likely increase as technology improves5. This Lithium cost premium has led to investigations of the possibility of batteries using other elements, with Sodium ion batteries occasionally being mentioned as an alternative.
The reason Lithium has dominated so much is that the atom is small and light. Despite being a metal, it is the third lightest atom behind Hydrogen and Helium, and its lighter mass was a way to reduce the weight of batteries in phones, computers and cars, while its smaller size allowed the batteries to be smaller6. Lithium is the lightest alkali metal while Sodium is the next lightest7. Being part of that group means that they have similar properties because they have only one electron in their outermost ‘shell’, which makes them highly reactive8.
The first vehicle with a Sodium-ion better has come off the production line (in China, of course). The vehicle is the Yiwei 3, a small four-door hatchback, and deliveries are expected to commence in January 20249. Yiwei is a new EV brand owned by Anhui Jianghuai Automobile (JAC), which was established in 2023. JAC’s parent company, Anhui Jianghuai Automobile Group Holdings (JAG), is 50% state-owned, and 50% owned to Volkswagen Group. The battery pack for this vehicle (initially demonstrated in another preproduction vehicle) has an energy density of about 120Wh/kg and the vehicle will have a maximum range of 505km (under the China Light-Duty Vehicle Test Cycle)10, which may be a considerable overestimate11.
While it is unlikely that Sodium-ion batteries will replace the Lithium version in vehicles that regularly travel long distances, they may be used for city runabouts and stationary energy storage (i.e. grid-scale storage batteries)10. Sodium is much more common than Lithium, with the US alone producing 12 million US tons of Sodium Carbonate in 202112. The oceans are also replete with the stuff, with each kilogram of ocean water containing about 10.5 grams of Sodium ions. The price of sodium carbonate (called soda ash in the commodity markets) is $US2790 per US ton12, less than one thirtieth the cost of lithium carbonate. That will likely make city runabouts and stationary storage batteries considerably cheaper.