US battery start-up Bedrock Materials says it is pausing the development of sodium-ion batteries and returning the majority of the capital back to investors.

Co-founder and ceo Spencer Gore claims that sodium-ion cannot compete with lithium-ion counterparts in the current market, as depressed lithium prices and technological advances are driving down battery costs. He says that Bedrock tried to boost energy density, which “came with steep technical, market, and environmental trade-offs” and did not yield a product “meaningfully better” than lithium iron phosphate chemistries available on the market.

“As for sodium-ion’s supposed performance advantages, we found that many could be matched by modest tweaks to existing lithium-ion chemistries,” Gore wrote on LinkedIn.

Spun out of Stanford University, the company came out of stealth last year, raised $9 million in seed funding and set headquarters in Chicago, Illinois. It also secured an incentives package from the state government under the Reimagining Electric Vehicles in Illinois Act, which Gore says will be fully returned.

Sodium-ion has emerged as a cheaper and more environmentally friendly alternative to lithium-ion, as sodium is widely available in most countries and does not need to be mined. It is also independent from most of the battery minerals supply chain, which tends to be affected by geopolitical events, Kallanish notes.

A Stanford University study published in January finds that sodium-ion “might reach cost-competitiveness” with low-cost lithium-ion variants in the 2030s, which can be achieved by increasing energy densities to decrease materials’ intensity.