Recently, the reporter learned from the Qingdao Institute of Bioenergy and Processes of the Chinese Academy of Sciences (hereinafter referred to as the Qingdao Institute of Energy) that the Solid State Energy System Technology Center of the Institute has carried out a lot of research work on key scientific issues in magnesium batteries. A series of achievements have been made in key scientific issues and core materials. The series of results have been recently published in the international authoritative journals "German Yinghua", "Advanced Materials" and "Advanced Energy Materials".
Potential magnesium metal secondary battery
Magnesium metal secondary batteries are not a concept that emerged in recent years. This electrochemical system has been developed for more than 20 years since Israeli scientist Doron Aurbach first proposed the magnesium metal secondary battery model in 2000. Cui Guanglei, a researcher at the Solid State Energy System Technology Center of the Qingdao Energy Institute, explained that a magnesium metal secondary battery refers to a recyclable battery with metal magnesium as the negative electrode. Material.
According to reports, metal magnesium has a very high volume capacity and is an excellent choice as a negative electrode for high volume energy density batteries. The working principle of magnesium metal 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. It is easy to process and operate, and it is also safer than lithium; magnesium batteries do not have the dendrite growth problems similar to lithium batteries; in terms of price, because magnesium is more abundant in the earth's crust, its price is cheaper than lithium.
With the implementation of the "dual carbon" strategy, new energy has ushered in a leap-forward development. As one of the key equipments that are widely used in the field of new energy, the importance of secondary batteries has received attention from all parties.
Cui Guanglei said that although researchers have made important progress in key materials such as magnesium storage cathodes, magnesium-conducting electrolytes, and magnesium metal anodes, there are still many basic scientific problems for magnesium metal secondary batteries that need to be overcome, and the industrial application is still in its early stages. exploration phase.
Specifically, the development of magnesium metal secondary batteries mainly faces two bottlenecks. Cui Guanglei said that first, magnesium electrolyte, as the "blood" in the battery system, plays an important role in the transmission of magnesium ions between the positive and negative electrodes. It directly contacts the positive and negative electrode materials inside the battery system, so it is necessary to take into account the magnesium metal at the same time. The special requirements of negative electrodes and high-energy magnesium storage positive electrodes greatly limit the choice of magnesium electrolyte components. It is of great significance to develop a new magnesium electrolyte system with good compatibility with the positive and negative interfaces. Second, because divalent magnesium ions not only carry It has two charges and is "small". This is not only the mystery of magnesium ions being able to store more charges under the same volume conditions, but also causes magnesium ions to have the characteristics of high charge density and strong polarization, and strong polarization. The effect will cause magnesium ions to be pinned by a large Coulomb force inside the lattice of the cathode material, resulting in a slow diffusion rate of magnesium ions. Therefore, the common intercalated cathode material structures of magnesium metal secondary batteries generally show poor reversible de-intercalation. The ability of magnesium ions to develop new efficient magnesium storage cathode materials is imminent.
Solve a series of problems in the research and development of magnesium metal secondary batteries
Focusing on the above-mentioned key problems to be solved in magnesium batteries, under the leadership of Cui Guanglei, the research team of Qingdao Energy Institute has carried out a lot of research work for many years.
In response to the problem of magnesium electrolytes, Cui Guanglei's research team established the synthesis route of boron (aluminum)-based magnesium salts through a large number of screening tests and theoretical analysis, and developed a series of high-performance boron (aluminum)-based magnesium electrolyte systems. Excellent Mg ion transport properties and Mg metal anode compatibility.
Cui Guanglei said that the researchers further expanded the choice of magnesium electrolyte components through the interface optimization project of magnesium metal anodes, which greatly improved the interface compatibility between various magnesium electrolyte systems and magnesium metal anodes. The research team also deeply analyzed the microscopic electrochemical reaction process at the interface of magnesium metal anode, and realized the efficient regulation of magnesium metal deposition/dissolution behavior, laying an important theoretical foundation for the efficient and recycling of magnesium metal anode.
"In addition to the above-mentioned liquid magnesium electrolyte system, in order to give full play to the high safety characteristics of magnesium metal batteries, the researchers have also designed and developed a variety of polymer-based solid magnesium with single-ion conductor concepts based on years of technical accumulation in solid-state lithium batteries. The electrolyte system shows excellent room-temperature magnesium ion transport performance and positive and negative interface compatibility. The researchers also successfully prepared the corresponding solid-state magnesium metal secondary battery device, realizing the wide temperature range and long cycle operation of magnesium metal battery, It provides sufficient technical reserves for the research and development of special power sources suitable for extreme working conditions such as underground resource exploration and space exploration." Cui Guanglei said, in addition, for the problem of magnesium storage cathode materials, the research team focused on the transformation with high specific capacity characteristics. type positive.
Cui Guanglei believes that among the many emerging battery technologies under research, magnesium metal secondary batteries have become extremely developed in the "post-lithium-ion battery" period with many advantages such as high volumetric energy density, high safety, high natural abundance and low cost. One of the potential battery systems.
At present, the research team and partners have published more than 30 high-impact SCI papers in the field of magnesium metal secondary batteries, and applied for more than ten related patents, basically forming the core technology of magnesium metal batteries with completely independent intellectual property rights. In terms of practical application scenarios, the team has broken through the key technical bottleneck in the production process of magnesium metal secondary batteries, and developed a single battery with an energy density of 560 Wh/kg, guided by the Chinese Academy of Sciences' deep-sea intelligent technology pilot project. The magnesium-sulfur battery system designed and assembled based on the single cell has not only successfully passed the simulated pressure test in the deep-sea high-voltage environment, but also has followed the research ship of the Institute of Deep Sea Research of the Chinese Academy of Sciences to achieve a continuous 30-hour stable operation in the deep-sea environment in the South China Sea. Demonstration applications of magnesium metal secondary batteries were successfully realized. Currently, larger application demonstration projects are also under preparation.
Cui Guanglei said that although the large-scale application of magnesium metal secondary batteries is still in the early stage of exploration, it has important potential in improving the safety of secondary batteries, reducing the cost of secondary batteries, and alleviating the pollution of secondary batteries. It is expected to partially replace lithium batteries or lead-acid batteries in multiple application scenarios.
(Original title "Progress in Electrolyte Research and Development: Magnesium Metal Secondary Batteries with Better Transmission and Higher Compatibility Move toward Large-scale Application")