People have been eagerly looking forward to achieving “long endurance” for drones, electric vehicles, and electric planes. However, due to the lack of a power system with stable “energy storage” and “power supply” capabilities, this expectation will always come to nothing.Fortunately, there has been good news recently-using3D printingTechnology may help solve the bottleneck problem faced by “long endurance”.
A few days ago, Sun Jingyu, a professor at the School of Energy of Soochow University, and a team of Liu Zhongfan, an academician of the Chinese Academy of Sciences and a professor at Peking University, established3D printingSulfur cathode, and obtained a lithium-sulfur battery with high rate performance and high areal capacity. Related technologies can also be extended to other emerging energy storage devices, providing an important reference for the development of new, efficient and large-scale electrode construction methods.
Relevant research results were recently published in the high-level international energy journal “Nano Energy”.
The “shuttle effect” in lithium-sulfur batteries
With the development of human society, people have also put forward higher requirements for energy storage systems.
Lithium-sulfur batteries are considered to be one of the most promising energy storage systems for the next generation because of their higher theoretical energy density, lower electrode material cost, and the advantages of environmentally friendly sulfur as the cathode material and rich resources. “Lithium-sulfur batteries have huge industrial application prospects in the fields of unmanned aerial vehicles, electric vehicles and military portable power supplies.” Sun Jingyu, the co-corresponding author of the paper, told China Science Daily. Unfortunately, due to the low conductivity of sulfur and its discharge products, the shuttle of polysulfides and the slow reaction kinetics, the utilization rate of sulfur is low, the cycle stability and rate performance are poor.
In recent years, in order to increase the utilization rate of active material sulfur and improve the electrochemical performance of lithium-sulfur batteries, researchers have conducted a large number of exploratory studies, striving to find suitable sulfur host materials, binders and electrolytes.
Although many research progress and achievements have been made in these fields, most lithium-sulfur battery systems still have problems such as low sulfur loading, low surface capacity, and excessive use of electrolyte, which are far from meeting the requirements of practical applications and commercialization.
Relevant studies have shown that one of the important factors leading to insufficient energy density and short battery cycle life of current lithium-sulfur batteries is the “shuttle effect” of polysulfides. Chen Jian, a researcher at the Dalian Institute of Chemistry and Physics, Chinese Academy of Sciences, told the Chinese Journal of Science that the so-called “shuttle effect” refers to the electrochemical reduction of sulfur during the discharge process of a lithium-sulfur battery, which is a two-electron, multi-step reaction. Sulfide (Li2Sx) intermediate product, soluble in ether electrolyte. If it diffuses to the negative electrode, it reacts with lithium to form insoluble lithium sulfide, which is corroded, consumes active materials, causes irreversible loss of capacity, and reduces the cycle life of the battery.
“Suppressing the’shuttle effect’ is one of the keys to the study of lithium-sulfur batteries. The most important thing is how to bind the long-chain polysulfides generated in the reaction to the side of the sulfur positive electrode, or fundamentally inhibit the production of polysulfides. This It is feasible in principle, but it needs further exploration.” Chen Jian said.
3D printingTechnology “blessing”
3D printingSince its birth, the technology has been applied to various fields such as medical, military, aerospace, automotive, electronics and so on. In addition, it has also been initially used in energy storage systems such as lithium-ion batteries, lithium-oxygen batteries, and zinc-ion batteries. The teams of Liu Zhongfan and Sun Jingyu have been paying attention to and carrying out research on olefinic carbon energy materials and application technologies for a long time.In recent years, they have changed from3D printingNew breakthrough ideas and enlightenments have been found in technology. Sun Jingyu introduced,3D printingThe technology has many advantages, such as helping to construct a self-supporting non-collector electrode with a hierarchical pore structure, and facilitating the rapid transmission of ions and electrons.3D printingThe technology realizes the control of the electrode material load by controlling the number of printed layers, breaking through the thickness limitation of the electrode prepared by the conventional coating method, so as to obtain a battery system with a high unit area capacity. In terms of practical applications, it can meet the construction needs of customized and large-scale energy storage devices.
“However, for energy storage applications3D printingThere are still many key bottlenecks in the technology, such as the higher requirements of the printing accuracy of the electrode on the equipment configuration, the urgent need for systematic exploration of the printing ink preparation process, and the lack of large-scale printing equipment. “Sun Jingyu said. The researchers used3D printingTechnology, convenient, efficient and convenient to construct a high-load sulfur cathode. The architecture has optimized ion/electron transport channels and sufficient porosity, which is conducive to efficient management of polysulfides.
In order to better suppress the “shuttle effect” mentioned above, the researchers also have a unique design for the printing ink. Sun Jingyu introduced that in recent years, the industry has shown great interest in the construction of high-performance lithium-sulfur batteries with metal borides. Among them, metallic lanthanum hexaboride (LaB6) with similar properties has been widely used in many fields as a low-cost and sustainable compound.
Based on this, they designed a mixed ink containing sulfur/carbon and LaB6 electrocatalyst for printing high-performance sulfur cathodes.The metallic LaB6 electrocatalyst can be evenly distributed in3D printingWithin the framework, it spontaneously ensures that there are abundant active sites for the fixation and conversion of polysulfides, so as to achieve a high-efficiency discharge or charging process.
“This has played a positive role in the management and control of polysulfides, and more effectively inhibits the’shuttle effect’, thereby obtaining a lithium-sulfur battery system with excellent performance. At the same time, it is also for designing the positive electrode structure of lithium-sulfur batteries and improving the reaction of sulfur positive electrodes. Kinetics provides new ideas and strategies.” Liu Zhongfan said that this research work is the first to introduce high-efficiency electrocatalysts into printable ink.3D printingSulfur cathode, a lithium-sulfur battery with high rate performance and surface capacity is obtained.
There are still “barriers” towards practicality
In recent years, the continuous innovation of new technologies and new methods and the accelerated transformation of scientific and technological achievements have promoted the practical development of high-performance lithium-sulfur batteries. The lithium-sulfur battery pack produced by Chen Jian’s team and China Science and Technology Energy Storage Technology Co., Ltd., which is incubated by the scientific and technological achievements of the Dalian Institute of Chemistry and Physics, Chinese Academy of Sciences, has been successfully tested on large-wingspan drones and high-speed drones. . “The battery life of this lithium-sulfur battery is 2.5 times that of a lithium-ion battery of the same weight.” Chen Jian said that the number of cycles of the battery needs to be further increased in the future, and to achieve this goal, it is necessary to solve the “shuttle effect” problem.
“In the process of moving towards practicality and industrialization, there are still many key issues in lithium-sulfur electrodes that need to be resolved. Development3D printingThe self-supporting structure of the sulfur cathode is worthy of attention. “Liu Zhongfan said. Sun Jingyu added that in addition to the requirements for the large-scale preparation of high-load sulfur electrodes, three issues need to be considered. The first is the carbon content of the positive electrode. Sun Jingyu pointed out that in order to solve the insulation of sulfur The problem is that it is usually necessary to add a larger amount of conductive carbon to balance, resulting in a low volume energy density of lithium-sulfur batteries. Therefore, in order to obtain a lithium-sulfur battery with high volume energy density, it is necessary to increase the tap density of the sulfur cathode and use less carbon There is even no carbon and sulfur host.
The second is the amount of electrolyte. “Due to the porosity of the sulfur positive electrode, a large amount of electrolyte needs to be consumed. In order to obtain a lithium-sulfur battery with high energy density, it is necessary to optimize the pore structure of the positive electrode and reduce the amount of electrolyte.” Sun Jingyu said.
In addition, the metal lithium anode is also one of the key issues, that is, in the large-scale lithium-sulfur system, it is necessary to adopt strategies to inhibit its dendritic growth to ensure the safety of the lithium anode. “In the future, as an extension of this research, we hope to develop a lithium-sulfur battery system that is truly low-carbon or even carbon-free, lean electrolyte, and high-sulfur loading.” Sun Jingyu said.
(Editor in charge: admin)
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