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Chinese and American researchers unlock next-generation solid electrolyte materials

2019-05-09 来源:亚科官网
 
The all-solid-state lithium battery can avoid the negative effect brought by the liquid electrolyte, improve the safety and service life of the battery; in addition, its solid characteristics can effectively prevent the penetration of lithium dendrites, making it possible to replace the traditional graphite anode material with lithium. At present, the industry generally believes that all-solid-state lithium-ion batteries will become the key technology for the next generation of lithium-ion batteries, achieving higher safety, energy density and longer cycle life.
The advantages of all solid lithium batteries
1) The safety is good, the electrolyte is non-corrosive, non-flammable, and there is no leakage problem;
2) High temperature stability, can work between 60 °C and 120 °C;
3) It is expected to achieve higher energy density. The solid electrolyte has good mechanical properties and effectively suppresses the short circuit caused by the growth of lithium elemental diameter, so that the electrode material with higher theoretical capacity can be selected, such as lithium element as the negative electrode; the solid electrolyte has a wider voltage window and can use a higher potential. The material does not hesitate to worry about electrolyte decomposition;
4) The solid electrolyte supports the thin film design of the battery, which can reach a minimum of several nanometers, broadens the application range of the lithium battery, and makes the battery self-contained flexibility possible.
5) It is possible to select materials with large resistance and large volume change during charge and discharge process as positive and negative electrodes, and thin film positive and negative materials, as long as the film forming performance is good, even if the material resistance is too large, as long as it is thin enough, it will still not It has a significant impact on battery characteristics.
Disadvantages of all solid lithium batteries
1) When the temperature is low, the internal resistance is relatively large;
2) The conductivity of the material is not high and the power density is difficult to increase;
3) difficulty in manufacturing large capacity monomers;
4) The positive and negative film forming technologies in large-scale manufacturing are still in the study of concentrated firepower.
Halogen inorganic solid electrolyte
Recently, the research group of Professor Mo Yifei of the Department of Materials Science and Technology of the University of Maryland cooperated with the research group of Professor Sun Qiang of the Materials Department of Peking University to study the halogen-based inorganic fast lithium ion conductor through first-principles calculation, and proposed and confirmed the chloride and bromine. As a fast ion conductor, it has good electrochemical stability and high ionic conductance. It is a potential next-generation solid electrolyte material. Based on the simulation of density functional theory, the team studied two materials, Li3YCl6 and Li3YBr6, recently reported by Panasonic Corporation, and theoretically confirmed that these materials have high ionic conductivity and a wide electrochemical window (0.6 to 4.2 V), and good compatibility with the layered oxide positive interface. On this basis, they further found through calculation that the anion lattice of the halide has a low lithium ion migration barrier intrinsic. Different from the design principle of traditional oxide and sulfide fast ion conductors, halogen compounds do not require a bulk-centered cubic anion framework structure and a coordinated transition transport mode, and can also have a lower lithium ion transition barrier. This provides guidance for further design of new solid state fast ion conductors.
In addition, another key technical issue for all-solid-state lithium batteries is the interface compatibility and stability between the solid electrolyte and the electrodes. The team found that chlorides and halides have a wide electrochemical window through the calculation of lithium-containing ternary halides in the Materials Project database, enabling coverage of the 4V battery voltage. And chloride and bromide exhibit good interfacial compatibility with the widely used positive electrode material LiCoO2. The good oxidation resistance of chloride ions can effectively inhibit the decomposition side reactions that occur during the delithiation process of the positive electrode material. Matsushita recently reported that all solid-state batteries assembled based on Li3YCl6 and Li3YBr6 exhibit good cycle stability and high coulombic efficiency without coating protection, confirming the good interface stability of the halide solid electrolyte, and The good processability of the material is also beneficial to further enhance the electrode/electrolyte contact area and reduce the interface impedance.
Edited by Suzhou Yacoo Science Co., Ltd.