New Battery Comprised Solely of Lithium-Sulfur-Based Compound

Researchers at the University of Maryland have achieved a first in lithium-ion battery science: the development of a successful lithium-based battery using one material for all three core components of a battery -- anode, cathode, and electrolyte.

In research supported by the National Science Foundation, a team led by Chunsheng Wang, a professor in the University of Maryland's Department of Chemical and Biomolecular Engineering, has used a material composed of a mix of sulfur, germanium, phosphorus, and lithium to create a battery 600 microns thick, or about the size of a dime, he said in an article on UMD's website.

In an interview with Design News, Wang explained how he and his team were able to successfully design a battery using only one material to play all the key roles, which typically are composed of different materials in a standard battery.

"The conventional all-solid-state lithium-ion batteries consist of three distinct components: an anode, an electrolyte, and a cathode," he told us. "In addition, current collectors are also used to ensure the electron transport through the electrodes and the external circuit. The anode, cathode, and electrolyte normally use three different materials due to the stringent different requirements for each component."

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For example, the electrodes are expected to be reversibly lithiated/delithiated at a low potential for the anode, or a high potential for the cathode with good mixed electronic/ionic conductivities. In the meantime, the electrolyte should have a wide electrochemical stability window with a very high ionic conductivity, but negligible electronic conductivity, Wang said.

His team was able to realize a single-Li10GeP2S12 battery by using the lithium-sulfur and geranium-sulfur components as active centers for lithiation/deliation as a cathode and anode, respectively, when mixed with electronically conductive carbon. Pure Li10GeP2S12 was used as the electrolyte.

"Some solid electrolytes can decompose into composite containing electrode components when potential is beyond certain voltage window," Wang explained. "Normally, these electrode components have low electronic conductivity, limiting the reaction kinetics. However, if carbon is coated/mixed into these electrode, these materials can provide high energy and power density as a electrode."

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The realization of the single-Li10GeP2S12 battery is based on the fact that the Li-S and Ge-S components in Li10GeP2S12 could act as the active centers for lithiation and delithiation as a cathode and an anode, respectively, when electronically conductive carbon is mixed, Wang said.

There are a number of practical and scientific benefits to a one-material battery, he told us. It simplifies the battery fabrication process, reducing the cost, as well as paves the way for the fabrication of nano-batteries. Real-world applications for the battery include everything from nano devices to the electric vehicle, Wang said.

While not fully proven yet, the battery also should have long cycle life and high power density, as well as easily integrate into an electronic circuit board, Wang added.

Researchers will continue working to optimize the cell structure and battery materials, as well as apply the same concept to oxide electrolytes. There is not yet a timeline or roadmap for commercialization, which depends on future investment in and needs for the battery.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She has lived and worked as a professional journalist in Phoenix, San Francisco, and New York City. In her free time she enjoys surfing, traveling, music, yoga, and cooking. She currently resides in a village on the southwest coast of Portugal.

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