A Novel Chemical State of the Element Manganese Has Been Discovered

Scientists have discovered a novel chemical state of the element manganese. This chemical state, first proposed about 90 years ago, 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 direct proof of a previously unconfirmed charge state in a manganese-containing battery component could inspire new avenues of exploration for battery innovations.

X-ray experiments at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) were key in the discovery. The study results were published Feb. 28 in the journal Nature Communications.

Scientists at Berkeley Lab and New York University participated in the study, which was led by researchers at Natron Energy, formerly Alveo Energy, a Santa Clara, California-based battery technology company.

The battery that Natron Energy supplied for the study features an unconventional 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 atomic structure of the anode material that achieved high performance in a sodium-ion battery. Sodium (Na) atoms and manganese (Mn) atoms are labeled. (Credit: Berkeley Lab)

The atomic structure of the anode material that achieved high performance in a sodium-ion battery. Sodium (Na) atoms and manganese (Mn) atoms are labeled. (Image: Berkeley Lab)

The anode featured in this latest study is 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.

But in this case, both of the battery’s electrodes utilize the same type of materials based on elements known as “transition metals,” which are useful in chemistry because they can exhibit various charged states. The other electrode, called a cathode, contains copper, nitrogen, carbon, and iron.

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.

The battery has been shown 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 discharge capacity for 1,000 cycles. It offers an alternative to gravity-based energy storage systems for the electric grid, in which water is pumped uphill and then released downhill on demand to generate electricity.

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.

In the middle and right images, produced using an X-ray technique at Berkeley Lab, there is a clear contrast in an exploration of the manganese chemistry in a battery electrode material. Another technique, known as sXAS (graph at left) does not reveal the same level of contrast. (Credit: Berkeley Lab)

In the middle and right images, produced using an X-ray technique at Berkeley Lab, there is a clear contrast in an exploration of the manganese chemistry in a battery electrode material. Another technique, known as sXAS (graph at left) does not reveal the same level of contrast. (Image: Berkeley Lab)

Such a novel chemical state would enable a voltage range that is useful for battery anodes. But there hadn’t been any measurements confirming this monovalent form of manganese.

The Natron Energy researchers studied the battery materials at Berkeley Lab’s Molecular Foundry, a nanoscience center, and then offered up some sample battery cells for study at the ALS.

The first round of X-ray experiments at the ALS, which used a technique called soft X-ray absorption spectroscopy, appeared to show mainly the 2-plus form of manganese.

Then the team turned to a newly built system at the ALS, 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.

Commercial prototypes based on the battery tested at the Lab entered customer beta testing earlier this year, Wessells noted. In addition to grid applications, Natron Energy is promoting the technology for data centers’ emergency power, and for heavy equipment such as electric forklifts, among other possible applications.

Yang said that the chemical puzzle solved in the latest study could inspire other R&D in new types of :

Provided by: Lawrence Berkeley National Laboratory [Note: Materials may be edited for content and length.]

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