Natron Energy’s Unique Cell Chemistry Shines in Collaborative Study with Lawrence Berkeley Lab and New York University
A collaboration between Natron Energy and scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and New York University has resulted in the discovery of a novel chemical state of the element manganese – first proposed about 90 years ago. This chemical state enables a high-performance, low-cost sodium-ion battery that could quickly and efficiently store and distribute energy produced by solar panels and wind turbines across the electrical grid. This evidence of a previously unconfirmed charge state in a manganese-containing battery component could also inspire new avenues of exploration for battery innovations.
Researchers at Natron Energy, formerly Alveo Energy, a Palo Alto, California-based battery technology company led this study in collaboration with scientists from Berkeley Lab and New York University. The battery samples were supplied by Natron Energy, and featured a unique design for an anode, which is one of its two electrodes. Compared with the relatively mature designs of anodes used in lithium-ion batteries, anodes for sodium-ion batteries remain an active focus of R&D. The anodes were made up of a blend of elements – including manganese, carbon and nitrogen – that is chemically similar to the formula of the iron-containing paint pigment known as Prussian Blue.
X-ray experiments were conducted at Berkeley Lab, the results of which were published on February 28, 2018 in the journal Nature Communications.
“Typically, in lithium-ion and sodium-ion batteries, the anode is more often carbon-based,” said Wanli Yang a staff scientist at Berkeley Lab’s Advanced Light Source (ALS), a source of X-rays that were used in the battery experiments.
But in this case, both of the battery’s electrodes utilize the same type of materials based on elements known as “transition metals” that are useful in chemistry because they can exhibit various charged states. The other electrode, called a cathode, contains copper, nitrogen, carbon, and iron.
“The very interesting part here is that both electrodes are based on the chemistry of transition metals in the same type of materials,” Yang added, with iron in the cathode and a special manganese chemistry in the anode.
“One of the direct benefits of utilizing such materials for both electrodes in the battery is that neither of the two electrodes fundamentally limits the power capability, cycle life, or cost of the device,” said Colin Wessells, CEO at Natron Energy. The battery outperforms the U.S. Department of Energy’s cycle-life and price targets for grid-scale energy storage, as the researchers report in their latest study.
Wessells noted that the battery is very stable, its materials are abundant, its overall cost is competitive with conventional lead-acid batteries, and it has a lesser environmental footprint than conventional batteries.
“Natron’s battery provides remarkably high power and long life, two aspects critical for certain industrial power and grid energy storage applications. Moreover, I expect lower total ownership cost compared with lead-acid or Li-ion alternatives, with higher safety and lower environmental impact,” said Bart Riley, founding CTO of A123 Systems and current CEO of Metalenz.
The battery has been demonstrated to deliver up to 90 percent of its total energy in a very fast, five-minute discharge, and to retain about 95 percent of its nominal capacity after over a thousand full charge-discharge cycles.
Just how the battery achieves its high performance, though, had puzzled researchers.
There was speculation, dating back to a 1928 German-language journal article, that manganese could exist in a so-called “1-plus” or “monovalent” state, which means that a manganese atom in this state loses only a single electron. This is unusual, as manganese atoms typically are known to give up two or more electrons, or no electrons, in chemical reactions, but not just one.
Such a novel chemical state would enable charge storage in an electrochemical potential range that is useful for battery anodes. But there hadn’t been any measurements confirming this monovalent form of manganese.
Natron Energy researchers studied the battery materials at Berkeley Lab’s Molecular Foundry, a nanoscience center, and then provided some sample battery cells for study at ALS.
The first round of X-ray experiments used a technique called soft X-ray absorption spectroscopy, and appeared to show mainly the 2-plus form of manganese.
“We only caught a hint (of another form) in the initial tests, and had to rely heavily on theory to speculate about a different state,” said Andrew Wray at New York University, who performed the theoretical calculations.
Then, the team turned to a newly built system dubbed in situ resonant inelastic X-ray scattering, or iRIXS. The technique, which provides a high-sensitivity probe of the internal chemistry of materials, showed a telltale contrast in the electrons during the battery’s charge and discharge cycles. Though conventional spectroscopic techniques were unable to clearly discern the existence of the manganese 1-plus state from the more commonly observed 2-plus state, the RIXS technique immediately identified the 1-plus state in fully charged anodes.
Wray added, “The analysis of the RIXS results not only confirms the manganese 1-plus state, but also shows that the special circumstances giving rise to this state make it easier for electrons to travel in the material. This is likely why such an unusual battery electrode performs so well.”
Commercial prototypes based on the initial battery tests entered customer beta testing earlier this year, Wessells noted. In addition to grid applications, Natron Energy is promoting the technology for data centers’ mission-critical backup power, and for heavy equipment such as electric forklifts, among other possible applications.
“The success of this study in both understanding longstanding scientific problems and then translating that understanding into a technology that could have a real world impact illustrates both the importance of collaboration between industry groups, national labs, and academic groups, but also the need for public and private funding agencies to support fundamental and applied research,” Wessells said.