Recently, the author learned from Qingdao Institute of Bioenergy and Process, Chinese Academy of Sciences (hereinafter referred to as Qingdao Energy Institute) that the solid State Energy System Technology Center of the institute has carried out a lot of research work around the key scientific issues in magnesium battery, and made a series of achievements in the key scientific issues and core materials of magnesium secondary battery. The series of results were recently published in the international authoritative journals "German Applications", "Advanced Materials" and "Advanced Energy Materials".

  Magnesium secondary battery with great potential

  Magnesium secondary batteries are not a recent concept. Since Israeli scientist Doron Aurbach first proposed the magnesium secondary battery model in 2000, the electrochemical system has been developed for more than 20 years. Cui Guanglei, a researcher at the solid State Energy System Technology Center of Qingdao Energy Institute, said that magnesium secondary battery refers to a recyclable battery with magnesium as a negative electrode. The core of magnesium secondary battery is magnesium negative electrode, electrolyte and positive electrode material that can be embedded with magnesium.

  According to the introduction, magnesium has a very high volume capacity, is an excellent choice for high volume energy density batteries negative electrode. The working principle of magnesium secondary battery is the same as that of lithium secondary battery, but it is safer than lithium secondary battery. The reason is that magnesium and most magnesium compounds are non-toxic or low toxic, and magnesium is not as active as lithium, easy to process and operate, but also safer than lithium; Magnesium batteries do not have dendrite growth problems similar to lithium batteries; Magnesium, which is more abundant in the Earth's crust, is cheaper than lithium.

  With the proposed goal of "double carbon", new energy ushered in leapfrog development. As one of the key equipment widely used in the field of new energy, the importance of secondary battery has been attached importance by all parties.

  Although researchers have made important progress in key materials such as magnesium positive electrode storage, magnesium conductive electrolyte and magnesium negative electrode, there are still many basic scientific problems to be overcome, and the industrial application of magnesium secondary batteries is still in the early stage of exploration, Cui said.

  Specifically, the development of magnesium secondary battery mainly faces two bottleneck problems. Cui Guanglei said that first, as the "blood" in the battery system, magnesium electrolyte plays an important role in transferring magnesium ions between the positive and negative electrodes. It directly contacts the positive and negative electrode materials in the battery system. Therefore, it is necessary to take into account the special requirements of the negative magnesium electrode and the positive high-energy storage magnesium electrode, which greatly limits the selection range of magnesium electrolyte components. It is important to develop a new magnesium electrolyte system with good compatibility with the positive and negative interface. Second, magnesium bivalent ion not only has two charges, but also "small size", which is not only the secret of magnesium ion can store more charges under the same volume condition, but also causes magnesium ion to have the characteristics of high charge density and strong polarization, which will lead to magnesium ion being restrained by large coulomb force inside the lattice of positive electrode material. As a result, the diffusion rate of magnesium ions is slow. Therefore, the common impended cathode material structure of magnesium secondary batteries generally shows poor reversible removal ability of magnesium ions. Therefore, it is urgent to develop a new type of highly efficient cathode material for magnesium storage.

  Solve magnesium secondary battery research and development series problems

  Under the leadership of Cui Guanglei, the scientific research team of Qingdao Energy Institute has carried out a lot of research work over the years around the key problems of magnesium battery to be solved.

  In order to solve the problem of magnesium electrolyte, Cui Guanglei's research team established the synthesis route of boron (aluminum) base magnesium salt through a large number of screening tests and theoretical analysis, and developed a series of high-performance boron (aluminum) base magnesium electrolyte system, which showed excellent magnesium ion transport characteristics and magnesium negative compatibility.

  Cui Guanglei said that the researchers further expanded the selection range of magnesium electrolyte components through the interface optimization project of magnesium anode, greatly improving the interface compatibility of multiple magnesium electrolyte systems and magnesium anode. The research team also in-depth analyzed the microscopic electrochemical reaction process at the interface of magnesium negative electrode, and realized the efficient regulation of magnesium deposition/dissolution behavior, which laid an important theoretical foundation for the efficient and recycling of magnesium negative electrode.

  "In addition to the liquid magnesium electrolyte system mentioned above, in order to take full advantage of the high safety characteristics of magnesium batteries, the researchers have designed and developed a polymer based solid magnesium electrolyte system based on a variety of single-ion conductor concepts based on the technology center's years of technical accumulation in solid lithium batteries. The system has demonstrated excellent magnesium ion transport performance at room temperature and positive and negative interface compatibility. The researchers have also successfully prepared the corresponding solid-state magnesium secondary battery devices, realizing the wide temperature area and long cycle operation of magnesium batteries, providing sufficient technical reserves for the development of special power sources suitable for extreme conditions such as underground resource exploration and space exploration." Cui said that in order to solve the problem of magnesium storage anode materials, the research team focused on conversion anode with high specific capacity characteristics.

  Cui Guanglei believes that among the many emerging battery technologies in development, magnesium secondary battery has become one of the battery systems with great development potential in the "post-lithium-ion battery" period with its advantages of high volume energy density, high safety, high natural abundance and low cost.

  At present, the research team and its partners have published more than 30 high-impact SCI papers and applied for more than 10 related patents in the field of magnesium secondary batteries, basically forming a magnesium battery core technology with fully independent intellectual property rights. In terms of practical application scenarios, the team, guided by the deep-sea Intelligent Technology Pilot Project of the Chinese Academy of Sciences, has broken through the key technical bottlenecks in the production process of magnesium secondary batteries, and developed a single battery with an energy density of 560 watt-hours/kg. The magnesium sulfur battery system designed and assembled based on the single battery has not only successfully passed the simulated pressure test in the deep-sea high-pressure environment, but also achieved 30 hours of continuous stable work in the deep-sea environment in the South China Sea with the research vessel of the Institute of Deep-sea Research of the Chinese Academy of Sciences, and successfully realized the demonstration application of magnesium secondary battery. Larger demonstration projects are also in the works.

  Although the large-scale application of magnesium secondary batteries is still in the initial stage of exploration, it has great potential to improve the safety of secondary batteries, reduce the cost of secondary batteries and alleviate the pollution of secondary batteries, and is expected to partially replace lithium batteries or lead-acid batteries in many application scenarios, Cui said.

  Responsible Editor: Yang Yiming

  The article comes from the Internet.