Scientists from the University of Science and Technology of China’s Professor Ji Hengxing published a research result in “Science”, the world’s leading scientific magazine. The researchers have achieved a major breakthrough on the research of lithium-ion electrode materials.
Ji Hengxing stated that “if we use this technology, we may be able fully charge an electrical car in around 10 minutes and travel about 500 kilometers.” The charging time of electric cars has always been a major problem. Electric vehicles are currently “waiting” an hour before they can drive 500 kilometers. The electric vehicle industry has always aimed to develop large-capacity Li-ion batteries that can be charged quickly.
The material of the electrode is an important factor when determining battery performance indicators. “If you are looking to increase battery charging speed, then you need material that is fast in electrochemical reactions. It is important to check if the electrode material can conduct electrons andions. Ji Hingxing, a member of the research group, said that they hope to find an electrode material capable of meeting the expectations set by the industry for comprehensive performance indicators and also adapting to the industrial production process.
Dr. Hongchang Jin introduced the thesis by saying: “Energy flows into and out of the battery via the chemical reactions between lithium ions, and electrode materials. Determining the charging rate is based on the conductivity between the electrode materials and lithium ions. It is important to consider the amount.”
The Jixingxing research team discovered that black phosphorus was a good choice. Firstly, it has a very high theoretical capacity, only second to single crystal lithium or metallic silicon. Second, because it is a semi-conductor, its ability to conduct electronic currents is strong. Thirdly, the black sheet phosphorus structure is layered and the lithium ions can easily be conducted between its layers. This excellent property makes black phosphorus an electrode material which can be used to fast charge lithium-ion batteries.
Black phosphorus (an allotrope to white phosphorus) is an excellent electrode material for fast charging. Current studies show that there’s a gap between black phosphorus’s comprehensive performance indicators and what was expected. The edge of the layered black phosphorus structure is susceptible to structural damage, and measured performance is lower than expected. Ji Xingxing adopted the “interface-engineering” strategy to connect graphite and black phosphorus through phosphorus carbon covalent bonds. This made the structure more stable and allowed lithium ions into the black phosphorus to be easier.
“Under the optimization of interfaces between these two levels, black phosphorous has reached a breakthrough performance.” Ji Hingxing told the media.
“We use traditional process routes and parameters to convert the black-phosphorous composite material into electrode sheets.” Laboratory measurements show that electrode sheets can recover up to 80% after just 9 minutes and still retain 90% of their capacity after 2000 charging cycles. Xin, co-first writer of the paper, and a research scientist at the Institute of Chemistry of Chinese Academy of Sciences said that if mass-production of this material is possible, and matching materials for cathodes and other auxiliary components can be found then the optimized design should achieve an energy density of 350 Wh. It has a lithium ion battery that can be charged quickly and is capable of delivering 350 Wh/Kg. The battery will enable electric vehicles with a range of up to 1,000 kilometres, and the experience for electric vehicle users will be improved.
Jixingxing will continue its exploration in the areas of basic research, scale preparation technology and other related fields. For battery technology to advance and for electric vehicles and consumer electronics to develop, a deep understanding of scientific fundamentals is needed. This includes the microstructure of electrode materials and their physical and chemical properties. “There’s still work to be accomplished, but the future is full of hope.” Ji Hengxing spoke.
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