Qingdao Energy Research Institute has developed high specific energy storage magnesium cathode materials
As one of the most competitive energy storage systems in the post-lithium-ion battery era, rechargeable magnesium metal batteries are receiving increasing attention from the industry, academia, and research circles due to their high specific energy, high safety, and low cost. However, the development of magnesium metal batteries has been limited by two major bottlenecks: (1) the lack of a magnesium electrolyte system that takes into account both the demand for magnesium metal anodes and corresponding cathodes; (2) the lack of excellent performance magnesium storage cathode materials because of the bivalent magnesium The ion (Mg2 +) has a high charge density, which causes the Mg2 + to be pinned by the Coulomb force inside the crystal lattice of the cathode material and causes the ion diffusion speed to be slow, so common embedded cathode materials generally show poor reversible deintercalation of Mg2 + .
In response to magnesium electrolyte problems, the Bionic and Solid State Energy System Research Group led by Cui Guanglei, a researcher at the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences, has developed a series of boron-based magnesium electrolyte systems that exhibit excellent reversible deposition of dissolved magnesium and conduct Mg Capacity (Adv. Energy Mater., 2017, 1602055; Electrochem. Commun., 2017, 83, 72; Energy Environ. Sci., 2017, 10, 2616-2625; ACS Appl. Mater. Interfaces 2018, 10, 28, 23757 -23765; Advanced Materials, 2019, 31 (11): 1805930). Regarding the problems of magnesium storage cathode materials, researchers focused on conversion cathodes with high specific capacity characteristics. Based on the boron-based magnesium electrolyte system developed in the previous period, the research team has developed magnesium-sulfur and magnesium with high energy density. Selenium battery system (Adv. Funct. Mater., 2017, 1701718; Energy Storage Materials, 2020, 26: 23-31), and found that the introduction of metallic copper in the positive electrode such as sulfur and selenium can greatly increase the rate of the electrochemical reaction on the positive electrode side And reversibility, the reason for the analysis is that the presence of metallic copper promotes the formation of copper-selenium compounds and copper-sulfur compounds on the positive side, but the specific magnesium storage mechanism of copper-selenium compounds and copper-sulfur compounds remains to be revealed.
Recently, the research group published the latest research work in the international journal "German Applied Chemistry" and found that in the positive electrode of Cu3Se2, a copper-selenium compound, Cu + as an active carrier can effectively regulate the electrochemical magnesium / magnesium on the positive electrode side.化 process. Specifically, Cu + establishes a rapid and reversible chemical balance between the positive electrode material and the liquid electrolyte at the interface, thereby introducing Cu + / Cu redox couples on the positive electrode side, while Cu + / Cu is highly reversible Greatly reduces the polarization voltage on the positive side during charging and discharging and improves the specific capacity. Through the mediating effect of Cu +, the reversible surface capacity of the positive reaction of the magnesium battery can be increased to 12.5 mAh cm-2. It is worth mentioning that the Cu + balance between the electrode and the electrolyte may also exist in other copper-sulfur compounds or copper-selenium compound cathodes, such as Cu2S and Cu2Se. The discovery of this electrochemical reaction mechanism will be helpful for the development and research of a series of high specific energy magnesium storage cathode materials.
The above work is supported by the National Key R & D Program, the Strategic Pilot Project of the Chinese Academy of Sciences, the National Natural Science Foundation of China, the Youth Promotion Association of the Chinese Academy of Sciences, and the Shandong Province Key R & D Program.
Schematic diagram of the mechanism of Cu + regulating Cu3Se2 magnesiumization / demagnesization process
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