Recently, a research and development team from Nanyang University in South Korea announced the successful development of a new type of lithium-sulfur battery. The battery has the same charge-discharge cycling performance as compared with the lithium-ion battery currently in commercial use. At the same time, its energy density can reach more than twice that of lithium-ion batteries. The R&D team is a diversified research team formed by South Korea and Italy. Among the above highly reliable lithium-sulfur batteries, R&D personnel use a highly reversible dual-mode sulfur cathode (dual-mode sulfur anode refers to the solid state Sulfur Electrode and Sulfide Electrolyte) and a Lithiated Silicon/Silicon Oxide Nanoanode.
The lithium-sulfur battery R&D team published the research results in the Nano Letters magazine of the American Chemical Society. In this article, the R&D personnel detailed the series of properties of the lithium-sulfur battery, including quite high Energy density, excellent charge and discharge efficiency, excellent charge and discharge cycle life, and can still achieve 750 mA/g to 1000 mAh/g when the number of charge/discharge cycles of the battery reaches 500 times the original capacity of 85%. Energy Density. It is the new lithium-sulfur battery that uses the new anode design and cathode optimization structure to make the battery achieve the above-mentioned advanced performance.
Because the sulfur used in lithium-sulfur batteries is low in cost and rich in content, and the theoretical capacity density of lithium-sulfur batteries can reach 1675 mAh/g (about 2500 watt-hour/kg), lithium-sulfur batteries will likely become the next-generation battery. Application Technology. In addition, the application of lithium-sulfur batteries also has many well-known difficulties and challenges, including the low utilization of lithium-sulfur battery active materials, in addition, soluble lithium sulfide may also reduce the sulfur electrode stability.
Lee from the research team described in the article: “The current optimization design for sulphur electrodes has made a consistent progress, in which sulfur leaching can be achieved through the use of conductive carbonaceous matrices and metal-organic frameworks and appropriate electrolytes. A number of research organizations have reported that adding lithium sulfides to lithium-sulfur batteries can effectively improve the charge-discharge cycle performance and energy density of lithium-sulfur batteries.
Another key issue for the above lithium-sulfur batteries is that they use lithium metal anodes. It is well known that there are some key problems in lithium metal anodes, including the fact that lithium metal anodes react with organic electrolytes when the lithium-sulfur battery is in operation. As a result, lithium dendrites grow. This problem will greatly reduce the cycle work efficiency of the battery and also cause safety problems. In addition to the above, lithium-sulfur batteries will also use sulfur cathodes. Lithium metal reacts with lithium sulfide during the operation of the battery to form a layer of Li2S insoluble material on the surface of lithium metal. This will directly lead to the loss of lithium metal. Will greatly reduce the battery cycle performance.
Alloy anode material instead of lithium anode
In order to further solve the problem of lithium metal excess caused by lithium metal anodes in lithium-sulfur batteries, a research group recently used alloy anode materials instead of lithium metal anodes. The lithium metal used in the lithium metal anode is often used as the structural material of the battery to ensure the cycle life of the battery, and the excessive lithium metal problem caused by the lithium metal anode further reduces the energy density of the battery and even affects the battery. Safety performance. Although a considerable amount of research results have shown that the use of sulfur cathodes in lithium-sulfur batteries can effectively ensure the cycle life and energy density of the batteries, further research is needed to apply alloy anodes to the actual lithium-sulfur battery application market. ”
In order to solve the above problems, the research team's researchers designed a lithium-sulfur battery using a dual-mode sulfur cathode and a lithiated silicon/silicon oxide nano-anode. The lithium-sulfur battery also has an optimized design. Liquid electrolyte.
The sulfur cathode of the above lithium-sulfur battery uses a gas diffusion layer electrode composed of an activated carbon-sulfur composite material and does not use a Li2S8 cathode solution. The maximum energy density of the above lithium-sulfur battery can reach 1300 mAh/g, and the unit energy density of the battery requires a total of 1.2 mg of sulfur, and about 0.2 mg of solid sulfur is consumed on the cathode of the battery. 1.024 mg of sulfur was dissolved in 80 μl of lithium polysulfide electrolyte.
At a C/3 operating speed, the lithium-sulfur battery has a cathode energy density of 1000 mAh/g. In the first working cycle of the battery, its overall working efficiency can reach 99.3%, and its overall working efficiency can exceed 99% even after more than 100 cycles.
The lithium/silicon oxide nano-anode obtained by lithiation of the lithium-sulfur battery has very high cycle work stability, and its energy density can still reach 800 mAh/g after the battery cycle times exceed 100 times. Work efficiency can even reach 100%.
Based on the results of the above study, the new lithium-sulfur battery achieves an average energy density of 750 milliampere-hours/gram when the average operating voltage is maintained at 1.8 volts, which corresponds to an energy density of approximately 497 watt-hours per kilogram.
Lee, a researcher at the above lithium-sulfur battery research group, said: “Through the above studies, we believe that lithium-sulfur batteries will promote the practical application of the battery. Among them, the lithium-sulfur battery will likely be used in some emerging markets, including Portable equipment, electric cars, large-scale power storage systems for renewable energy, etc."
