Black Phosphorus Graphite Composite is a new composite material made from Black phosphorus and graphite. Black phosphorus (BP) is a desirable anode material for alkali metal ion storage owing to its high electronic/ionic conductivity and theoretical capacity. An in-depth understanding of the redox reactions between BP and the alkali metal ions is key to reveal the potential and limitations of BP, and thus to guide the design of BP‐based composites for high‐performance alkali metal-ion batteries.
A few days ago, the team of Professor Ji Hengxing from the University of Science and Technology of China published a scientific research result in the top international magazine "Science"-they have made a major breakthrough in the research of new lithium-ion battery electrode materials: a newly designed black phosphorus composite material is possible A lithium-ion battery with the three advantages of high capacity, fast charging and long life is prepared.
Ji Hengxing introduced that if this technology is put into use, "we may be able to fully charge an electric car in about 10 minutes and drive about 500 kilometers." Long charging time has always been the shortcoming of electric vehicles. Currently, the most advanced electric vehicles on the market need to "wait" for an hour to drive about 500 kilometers. The development of large-capacity lithium-ion batteries with fast charging capabilities has always been an important goal of the electric vehicle industry.
The electrode material is a key factor in determining battery performance indicators. "If you want to increase the battery charging speed, you need a material with a fast electrochemical reaction. One of the very important criteria is whether the electrode material has a strong ability to conduct electrons and ions." Ji Hingxing said the research team hopes to discover An electrode material that can not only give the industry expectations in terms of comprehensive performance indicators but also adapt to the industrial battery production process.
The first author of the thesis, Dr. Hongchang Jin, introduced: "Energy enters and exits the battery through the chemical reaction between lithium ions and electrode materials. Therefore, the conductivity of the electrode material to lithium ions is the key to determining the charging speed; in addition, the electrode material per unit mass or volume contains lithium ions. The amount is also an important factor."
The Jixingxing team found that black phosphorus is an excellent choice. First of all, its theoretical capacity is very high, second only to single crystal silicon or metallic lithium. Secondly, as a semiconductor material, it has a strong ability to conduct electrons. Third, black phosphorus has a layered structure, and lithium ions can be quickly conducted between the layers of the black phosphorus sheet. These excellent properties make black phosphorus a very promising electrode material that can realize the fast charging of lithium-ion batteries.
Black phosphorus is an allotrope of white phosphorus, and it is an electrode material with great potential to meet the requirements of fast charging. However, a series of current studies have found that there is a certain gap between the comprehensive performance indicators of black phosphorus and expectations. Black phosphorus is prone to structural damage from the edge of the layered structure, and the measured performance is far lower than theoretical expectations. For this reason, Ji Xingxing team adopted the strategy of "interface engineering" to connect black phosphorus and graphite through phosphorus-carbon covalent bonds to make its structure more stable, and the process of lithium ions entering the black phosphorus particles is easier, which greatly improves Lithium-ion conduction, which may have been limited, is eliminated.
In addition, the electrode material will be wrapped in chemicals that gradually decompose the electrolyte during the working process. Some substances will prevent lithium ions from entering the electrode material, just like dust on the glass surface hinders light penetration. The research team put a layer of clothing on the composite material for this purpose. They used a thin polymer gel to make a dust-proof coat and "worn" on the surface of the black phosphorous graphite composite material to allow lithium ions to enter smoothly.
"Under the interface optimization of these two levels, this black phosphorous composite material has achieved a breakthrough in performance." Ji Hingxing said.
"We use conventional process routes and technical parameters to make the black phosphorous composite material into the electrode sheet. Laboratory measurement results show that the electrode sheet can recover about 80% of the power after 9 minutes of charging, and it can still maintain 90% of the capacity after 2000 cycles." Xin Sen, the co-first author of the paper and a researcher at the Institute of Chemistry of the Chinese Academy of Sciences, said that if mass production of this material can be achieved, and matching cathode materials and other auxiliary materials can be found, the optimized design will be expected to achieve an energy density of 350 Wh. /Kg, and has a lithium-ion battery with fast charging capability. This means that it can make electric vehicles travel close to 1,000 kilometers, and will increase the user experience of electric vehicles to a higher level.
On this basis, the Jixingxing team will continue to explore in terms of basic research and scale preparation technology. In-depth understanding of basic scientific issues such as the microstructure, physical and chemical properties, and electrochemical reaction process of electrode materials, as well as the performance requirements of the industry for core materials, are necessary to achieve breakthroughs in battery technology and promote the development of consumer electronics, electric vehicles, and other related fields condition. "To achieve this vision, there is still a lot of work to be done, but we are full of hope for the future." Ji Hengxing said.
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