PNNL’s Sodium Battery Research Seeks to Enhance Affordable Energy Storage Solutions

Over the next decade, global energy demand is expected to continue to climb, driven by population growth, industrial expansion, and the shift toward high performance transportation. This forecast highlights the urgency of advancing energy storage technologies that can handle greater capacity, ensure reliability, and maintain affordability as the world works to meet its rising energy needs. To develop storage that meets all these needs, researchers at Pacific Northwest National Laboratory (PNNL) are exploring solutions that combine cost-effectiveness and scalability. 

Among them is Mark Weller, an early career materials scientist whose innovative research on enabling solid-state sodium batteries, an alternative to traditional lithium-based energy storage technology, was recently awarded $75,000 in funding from the Department of Energy’s Office of Electricity. 

Weller is optimistic about sodium’s potential to fill critical gaps in the energy storage market. It’s an Earth-abundant and cost-effective material with wide availability that supports the development of scalable and affordable battery systems, particularly for stationary applications like grid storage. However, sodium’s unique chemistry introduces challenges, particularly at the interface where the sodium anode meets the solid electrolyte. Dendrites, which are needle-like filaments, can form at this interface and cause short circuits, rapid degradation, and even safety hazards.

“One of the biggest challenges in solid-state batteries, especially those using alkali metals like lithium or sodium, is dendrite formation,” Weller explained. “With traditional liquid electrolyte batteries, a short circuit from dendrite formation may lead to fires or thermal events. While solid-state batteries are much less reactive, a dendrite-induced short circuit still destroys the battery.”

Weller’s project seeks to overcome these challenges, focusing on three key components: demonstrating a symmetric solid-state cell, designing a composite sulfur cathode to optimize material loading and performance, and developing a solid-state full cell capable of more than 90% capacity utilization. This proof-of-concept aims to show that solid-state sodium batteries can consistently tap nearly their entire theoretical energy capacity, cycle after cycle. 

“We’re starting with small-scale cells to show that these ideas work,” Weller said. “If we can demonstrate reliability and performance here, we can take the next step—scaling up to a full battery system.” 

Before pursuing this solid-state configuration, Weller’s research centered on molten sodium batteries, which operate at high temperatures of about 350°C, a level that limits their broader use. The team successfully reduced the operating temperature to a more practical range of 120°C to 180°C, closer to the 97.8 °C melting point of sodium. However, this progress brought another challenge: ensuring sodium interacts effectively with the ceramic electrolyte. 

“Sodium doesn’t easily wet the ceramic surface,” Weller explained. “It behaves like water on a waxed car, forming beads instead of making solid contact. Poor wetting limits a battery’s efficiency because good contact is critical to deliver power and utilize all the capacity in a battery. It turns out, solving the wetting problem in molten batteries also helps to solve the dendrite problem in solid-state batteries.” 

Drawing on his graduate work with lithium solid-state batteries, Weller adapted strategies to improve sodium’s behavior on ceramic surfaces. These insights, in conjunction with his work on molten sodium, laid the groundwork for his current research. By isolating and refining the performance of the sodium anode in symmetric cells, Weller and the team are working initially to address key issues like interface stability and dendrite formation. This foundation of a robust sodium anode will pave the way for integrating a composite cathode and developing a fully functional solid-state battery. 

While still in the early stages, this research could pave the way for larger-scale efforts that shape the future of energy storage, supporting intermittent energy integration, and the growing demand for safe, reliable, long-duration batteries for the grid.

“The goal of this project is to develop low-cost energy storage solutions. There’s a lot of exciting work going on at the Lab, and I’m hopeful we can get some good results with this project and really push the boundaries of solid-state batteries” Weller said.