Can Sodium Replace Lithium EV Batteries?

Commercial lithium-ion batteries power numerous electronic products, including electric vehicles (EVs) and renewable electric power grid storage systems. Lithium comes primarily from hard rock mining of spodumene minerals, primarily in Australia, and brine evaporation in salt plains in South America. This makes lithium relatively expensive.

Lithium prices have fluctuated wildly over the past several years as EVs have become more widespread, driving up demand for the metal. But what if manufacturers could make a battery from a cheap and abundant material—how about sodium?

 

JAC Motors’ vehicle powered by sodium-ion batteries. Image used courtesy of JAC Motors

 

How Lithium Batteries Work

In a battery, lithium acts as a charge carrier. Lithium moves as an ion from the cathode (positive electrode) through a liquid electrolyte to the anode (negative electrode) during charging. During discharging, lithium moves from the anode to the cathode, releasing electrons to power an electronic device or drive a vehicle. 

Anodes in lithium-ion batteries are typically made from carbon graphite. In contrast, the cathodes in commercially available lithium-ion batteries are made from nickel oxides combined with cobalt and manganese or aluminum to make the high energy density but relatively expensive batteries frequently used in EVs. Lower energy density lithium-ion batteries using cathodes made from iron and phosphates (LFP) are also produced at lower cost. These are used in EVs with shorter ranges or less performance and in battery energy storage systems for renewable energy power grids. 

 

Sodium as a Charge Carrier

Sodium is much more abundant than lithium and more widely distributed—it is available in vast salt deposits and seawater. This widespread availability makes it much less expensive than its neighbor on the periodic table. Sodium is chemically similar to lithium.

The development of sodium-ion batteries began in the 1990s. Initially, the low energy density exhibited by sodium-ion batteries slowed development, but recently, Chinese battery giant Contemporary Amperex Technology Co. Ltd. (CATL) planned production of a sodium-ion battery capable of an energy density of 160 Wh/kg. The company expects to boost the density to 200 Wh/kg soon after production starts. By comparison, the nickel-based cathode lithium-ion batteries used by Tesla can produce 260 Wh/kg, while the LFP batteries used by Tesla in its Model 3 Standard Range, also produced in China, have an energy density around 200 Wh/kg. 

 

CATL’s sodium-ion battery. Image used courtesy of CATL

 

Compared to the lithium ions used in current batteries, sodium ions have a larger volume. This means they do not fit well into the cathode and anode materials used in lithium-ion batteries without creating excessive stress in the electrode materials. CATL has developed new cathode materials capable of accommodating the larger sodium ions. This improvement enables large amounts of storage and fast movements to allow more rapid charging (up to 80 percent state of charge in as little as 15 minutes). The battery also shows superior low-temperature performance when compared to lithium-ion-based cells. In addition, the cathode does not use expensive nickel or cobalt compounds, reducing the cost of the battery. 

 

Sodium-ion Batteries in EVs

Volkswagen is backing a new EV brand in China called Yiwei as part of the JAC Group, of which it owns 50 percent. The Chinese government owns the remaining 50 percent. The five-seat Yiwei 3 model features sodium-ion cells in a cylindrical format produced by a Chinese startup called HiNa Battery. It has a 25 kilowatt-hour (kWh) battery pack of sodium-ion cells with a 120 Wh/kg energy density, providing the small EV with a range of up to 155 miles (250 kilometers) on a single charge. The company claims recharging from 10 percent to 80 percent state of charge can be accomplished in 20 minutes. 

Just as LFP batteries are replacing nickel-based lithium-ion batteries in some applications, low-cost sodium-ion batteries could offer reasonable performance for small EVs.