Southwest Research Institute develops battery interchangeability index

Researchers at the Southwest Research Institute (SwRI) have developed a new method to determine when sodium-ion batteries can provide comparable performance to lithium-ion batteries for specific applications. This approach uses a numerical measure called the Electrical Interchangeability Index (EII) to quantify how closely different battery technologies can satisfy the same electrical duty cycle.

While lithium-ion batteries are the current standard due to their high energy density and light weight, lithium mining is expensive and rising demand is straining global supply chains. Sodium-ion batteries offer a more affordable and abundant alternative using cheaper salts and lower-cost components, though they are typically heavier and store less energy.

The research team focused on the 18650-format cylindrical cells, which are widely used in consumer electronics, power tools, and electric vehicles. By assessing performance across various operating conditions rather than evaluating individual parameters like voltage or capacity in isolation, the EII helps manufacturers identify specific scenarios where sodium-ion cells can safely replace lithium-ion cells without sacrificing performance.