my country's research on lithium sulfide battery materials has made progress, which may promote the progress of electric vehicles -Lithium - Ion Battery Equipment
Recently, Zhang Yuegang's research group at the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences independently developed and designed an in-situ scanning/transmission electron microscope electrochemical chip, which enabled real-time observation of the charging process of lithium sulfide (Li2S) electrodes; in fully understanding Li2S charging Based on the discharge mechanism, a high-nitrogen-doped graphene-loaded lithium sulfide material was designed as the battery cathode. By controlling the charging capacity and voltage, the capacity utilization and cycle life of Li2S were significantly improved. The relevant results were published in the journal Advanced Energy Materials.
With the development of society and science and technology, human demand for electrochemical energy storage technology is increasing day by day. The emerging energy storage system-lithium-sulfur battery has the advantages of high theoretical capacity, low cost, and environmental friendliness, and has been favored by researchers at home and abroad. focus on. The research and development of high-capacity lithium-sulfur battery cathode materials is crucial to promoting the development of new energy electric vehicles, portable electronic devices and other fields.
The theoretical capacity of lithium sulfide (Li2S) material is as high as 1166mAhg-1, which is several times that of other transition metal oxides and phosphates; the volume shrinkage that occurs during the first delithiation charging process can provide space for subsequent lithium insertion discharge reactions, protecting The electrode structure is not damaged; it can be assembled with non-lithium metal anode materials (such as silicon, tin, etc.) to assemble batteries, effectively preventing safety hazards caused by lithium dendrite formation and other problems. It is a lithium-sulfur battery cathode with great development potential. Material. However, the material has low electronic/ion conductivity and problems such as the shuttle effect caused by the dissolution of polysulfide, the reaction intermediate product, in the electrolyte, which limits its practical application in lithium-sulfur batteries.(Lithium - Ion Battery Equipment)
In order to improve the capacity utilization and cycle life of lithium-sulfur batteries, researchers usually fill sulfur into porous materials with high specific surface area and high conductivity (such as carbon nanotubes, porous carbon, graphene and carbon fibers, etc.). In previous research work, Zhang Yuegang's research group found that the introduction of nitrogen-doped functional groups on graphene oxide can not only effectively reduce the dissolution of polysulfides in the electrolyte, but also optimize the distribution of polysulfides during the deposition process (NanoLetters, 2014, 14,4821−4827). In order to better improve the capacity utilization and cycle life of Li2S, the team used in-situ characterization technology to study the dissolution and redeposition mechanism of Li2S, and then proposed to adjust the initial activation battery voltage to 3.8V, and then control the voltage (1.7~2.4 V) and charging capacity can effectively prevent the formation of long-chain soluble polysulfides. This charge-discharge control method allows the electrode to retain a portion of insoluble Li2S as seeds during the charging process, allowing the Li2S material to be effectively activated and uniformly redeposited. . In addition, this study effectively increased the wrinkle rate and bending rate of graphene by coating the surface of graphene oxide before nitriding with glucose, thus providing more loading sites for polysulfides; during the reaction process, The method of heat treatment with ammonia water and high-temperature ammonia gas increases the nitrogen doping amount to 12.2%; this high-nitrogen-doped graphene material not only has high conductivity, but its surface nitrogen functional groups can effectively reduce the dissolution of polysulfides and optimize the uniformity of Li2S distributed. The lithium-sulfur battery prepared using this high nitrogen-doped graphene-Li2S composite cathode material can still maintain a capacity of 318mAhg-1 (converted to 457mAhg-1 based on the weight of sulfur element) after 2000 cycles (1C), and 3000 cycles ( 2C) It can still maintain 256mAhg-1 (368mAhg-1 based on the weight of sulfur element) after cycling, which is the longest cycle life reported so far.
This research work used newly developed in-situ scanning electron microscopy and in-situ transmission electron microscopy chip technologies for the first time to achieve real-time observation of the charging process of lithium sulfide electrodes, and developed a new voltage-capacity control method based on studying the charging and discharging mechanism of Li2S.
With the development of society and science and technology, human demand for electrochemical energy storage technology is increasing day by day. The emerging energy storage system-lithium-sulfur battery has the advantages of high theoretical capacity, low cost, and environmental friendliness, and has been favored by researchers at home and abroad. focus on. The research and development of high-capacity lithium-sulfur battery cathode materials is crucial to promoting the development of new energy electric vehicles, portable electronic devices and other fields.
The theoretical capacity of lithium sulfide (Li2S) material is as high as 1166mAhg-1, which is several times that of other transition metal oxides and phosphates; the volume shrinkage that occurs during the first delithiation charging process can provide space for subsequent lithium insertion discharge reactions, protecting The electrode structure is not damaged; it can be assembled with non-lithium metal anode materials (such as silicon, tin, etc.) to assemble batteries, effectively preventing safety hazards caused by lithium dendrite formation and other problems. It is a lithium-sulfur battery cathode with great development potential. Material. However, the material has low electronic/ion conductivity and problems such as the shuttle effect caused by the dissolution of polysulfide, the reaction intermediate product, in the electrolyte, which limits its practical application in lithium-sulfur batteries.(Lithium - Ion Battery Equipment)
In order to improve the capacity utilization and cycle life of lithium-sulfur batteries, researchers usually fill sulfur into porous materials with high specific surface area and high conductivity (such as carbon nanotubes, porous carbon, graphene and carbon fibers, etc.). In previous research work, Zhang Yuegang's research group found that the introduction of nitrogen-doped functional groups on graphene oxide can not only effectively reduce the dissolution of polysulfides in the electrolyte, but also optimize the distribution of polysulfides during the deposition process (NanoLetters, 2014, 14,4821−4827). In order to better improve the capacity utilization and cycle life of Li2S, the team used in-situ characterization technology to study the dissolution and redeposition mechanism of Li2S, and then proposed to adjust the initial activation battery voltage to 3.8V, and then control the voltage (1.7~2.4 V) and charging capacity can effectively prevent the formation of long-chain soluble polysulfides. This charge-discharge control method allows the electrode to retain a portion of insoluble Li2S as seeds during the charging process, allowing the Li2S material to be effectively activated and uniformly redeposited. . In addition, this study effectively increased the wrinkle rate and bending rate of graphene by coating the surface of graphene oxide before nitriding with glucose, thus providing more loading sites for polysulfides; during the reaction process, The method of heat treatment with ammonia water and high-temperature ammonia gas increases the nitrogen doping amount to 12.2%; this high-nitrogen-doped graphene material not only has high conductivity, but its surface nitrogen functional groups can effectively reduce the dissolution of polysulfides and optimize the uniformity of Li2S distributed. The lithium-sulfur battery prepared using this high nitrogen-doped graphene-Li2S composite cathode material can still maintain a capacity of 318mAhg-1 (converted to 457mAhg-1 based on the weight of sulfur element) after 2000 cycles (1C), and 3000 cycles ( 2C) It can still maintain 256mAhg-1 (368mAhg-1 based on the weight of sulfur element) after cycling, which is the longest cycle life reported so far.
This research work used newly developed in-situ scanning electron microscopy and in-situ transmission electron microscopy chip technologies for the first time to achieve real-time observation of the charging process of lithium sulfide electrodes, and developed a new voltage-capacity control method based on studying the charging and discharging mechanism of Li2S.
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