SEOUL, November 04 (AJP) - A research team in South Korea built an electrode material that worked in two batteries that store energy in different ways, a sodium-ion battery and a copper-ion battery that runs on a water-based electrolyte.
The team, led by Choi Jae-won, a chemistry professor at Sookmyung Women's University, and Hong Seung-woo, a professor in Ewha Womans University's Department of Chemistry and Nanoscience, made the material by combining copper indium sulfide particles with carbon nanotubes.
Used as the negative electrode of a sodium-ion battery, the material held a capacity of 339.1 milliampere-hours per gram after 1,000 charge-discharge cycles under high-current conditions. Capacity here means how much electric charge each gram of electrode material can store. As the positive electrode of a water-based copper-ion battery, the same material held 243.1 milliampere-hours per gram after 2,000 cycles.
Sookmyung said the ability to use one material in batteries that operate differently widened the options for developing materials for next-generation rechargeable batteries.
The findings were published Oct. 22 in Small, an international journal covering nanoscale science and materials. Jin Young-ho, a researcher with a doctorate, was the first author, and Choi and Hong served as co-corresponding authors.
Rising demand for electric vehicles and energy storage systems, the large battery banks that hold electricity for later use, has pushed researchers to look for batteries that can supplement lithium-ion cells. Sodium-ion batteries draw interest because sodium, their key raw material, is abundant. Copper-ion batteries that use a water-based electrolyte, the liquid through which charged particles called ions travel inside a battery, are also being studied as a new way to store energy.
Improving either battery depends on how its electrodes hold up. A battery stores and releases energy as ions move in and out of its electrodes during charging and discharging. If that movement is sluggish, or if repeated use deforms the electrode's structure, the battery loses performance.
The team turned to carbon nanotubes, extremely thin tubes made of carbon atoms that conduct electricity well. The nanotubes created paths for electrons to move between the electrode particles, and the team designed the electrode so its structure would hold up through repeated charging and discharging.
The university said the test results showed the material could be reused many times even under conditions that demand fast charging and discharging.
The researchers also examined how the same material behaved in each battery. In the sodium-ion battery, the crystal structure inside the electrode changed as it charged and discharged. In the copper-ion battery, the basic crystal structure largely stayed intact.
The two batteries stored energy differently because they relied on different ions and electrolytes. In both, however, the carbon nanotubes helped electrons move and kept the electrode particles connected.
The university's announcement reported tests of the electrode material's performance. It did not report results from full-size battery cells or finished products, and it gave no timeline for commercial use.
"Because we used carbon nanotubes to raise the electrode's electrical conductivity and structural stability, we expect this to contribute to developing high-performance electrode materials that can be applied to a range of next-generation rechargeable batteries," Choi said.
The research was funded by the National Research Foundation of Korea's Basic Research Laboratory program, among other sources, and by Gyeongsang National University's Glocal University 3.0 Project Fund.
[Reference Information]
Journal/Source: Small (IF 11.9, JCR top 8.1%)
Title: Colloidal CuInS2@CNT Electrode Enabling High-Rate Sodium Storage and Durable Aqueous Copper-Ion Batteries
Link/DOI: https://doi.org/10.1002/smll.75255
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