World’s first anode-free sodium solid-state battery a ‘breakthrough’

Utilising this new research, LESC – a collaborative project between UChicago Pritzker School of Molecular Engineering and the University of California San Diego’s Aiiso Yufeng Li Family Department of Chemical and Nano Engineering – has been able to edge closer to a reality where inexpensive, fast-charging, high-capacity batteries are present. Find more eco-news here.

“Although there have been previous sodium, solid-state, and anode-free batteries, no one has been able to successfully combine these three ideas until now,” said UC San Diego PhD Candidate Grayson Deysher.

The paper, published on the 3^rd July in Nature Energy, detailed the new sodium battery architecture capable of stable cycling for several hundred cycles. The design eliminated the anode and utilised inexpensive, abundant sodium in place of lithium, making the battery more affordable and environmentally friendly to produce. Its innovative solid-state design also ensured safety and high performance.

This development represents both a scientific advancement and a crucial step towards bridging the battery scaling gap required to transition the global economy away from fossil fuels.

“To keep the United States running for one hour, we must produce one terawatt hour of energy,” Meng said. “To accomplish our mission of decarbonizing our economy, we need several hundred terawatt hours of batteries. We need more batteries, and we need them fast.”

Sodium’s sustainability superiority

The lithium typically used for batteries is relatively scarce, comprising about 20 parts per million of the Earth's crust. In contrast, sodium constitutes about 20,000 parts per million. This scarcity, coupled with the rising demand for lithium-ion batteries in laptops, phones, and electric vehicles, has driven prices up, making these essential batteries increasingly unaffordable.

Lithium deposits are highly concentrated, with the "Lithium Triangle" of Chile, Argentina, and Bolivia accounting for more than 75% of the world's supply. Other significant deposits are found in Australia, North Carolina, and Nevada. This geographical concentration benefits certain nations over others in the decarbonisation efforts needed to combat climate change.

Meng noted: “Global action requires working together to access critically important materials.”

Lithium extraction also has significant environmental impacts, whether through the use of industrial acids to break down mining ore or the more common brine extraction method that involves pumping large amounts of water to the surface to dry.

In contrast, sodium, which is abundant in ocean water and soda ash mining, is a more environmentally friendly battery material. The research from LESC has also demonstrated its potential to be a powerful alternative.

Creating new battery architecture

To achieve a sodium battery with the same energy density as a lithium battery, the team had to develop a new sodium battery architecture.

Traditional batteries include an anode to store ions during charging. When the battery is in use, ions move from the anode through an electrolyte to a current collector (cathode), providing power to devices and vehicles.

Anode-free batteries eliminate the anode, storing ions on an electrochemical deposition of alkali metal directly on the current collector. This method allows for higher cell voltage, lower cost, and increased energy density, but it presents its own set of challenges.

Deysher explained: “In any anode-free battery, there needs to be good contact between the electrolyte and the current collector. This is typically very easy when using a liquid electrolyte, as the liquid can flow everywhere and wet every surface. A solid electrolyte cannot do this.”

However, liquid electrolytes lead to a buildup called solid electrolyte interphase, which steadily consumes the active materials, diminishing the battery’s effectiveness over time.

Creating a solid-liquid

The team adopted an innovative approach to this problem. Instead of using an electrolyte that surrounds the current collector, they designed a current collector that surrounds the electrolyte.

They constructed their current collector from aluminium powder, a solid material that can flow like a liquid. During battery assembly, the powder was densified under high pressure to form a solid current collector while maintaining liquid-like contact with the electrolyte. This design enabled low-cost and high-efficiency cycling, advancing this transformative technology.

Deysher remarked: “Sodium solid-state batteries are usually seen as a far-off-in-the-future technology, but we hope that this paper can invigorate more push into the sodium area by demonstrating that it can indeed work well, even better than the lithium version in some cases.”

The ultimate goal is an energy future with a variety of clean, inexpensive battery options that store renewable energy and are scalable to meet society’s needs.

Meng and Deysher have filed a patent application for their work through UC San Diego’s Office of Innovation and Commercialisation.