As we all know, lithium-ion battery is widely used in contemporary society because of its excellent energy density. Although it is easy to form dendrites and SEI films in the process of recycling, which leads to battery performance damage, failure and even the risk of fire, there is no perfect new technology to replace it.
For a long time, scientists have been trying their best to find new ways to overcome these bottlenecks. It is reported that researchers at the University of Arkansas (the University of Arkansas) recently developed a new type of lithium-containing cross-linked polymer material. The new material, called LiGL (GL= glycerol / glycerol), helps solve the above two problems with commercial lithium metal anodes.
It is said that the LiGL polymer film has excellent properties, which can effectively prevent the dendrite growth of lithium metal anode and the formation of SEI film, and realize the long-term stable cycle performance of lithium electrode. The study was recently published in the journal Progress in Energy Materials (Energy Material Advances).
So far, a variety of technical strategies have been reported to solve the problems of lithium anode, such as three-dimensional (3D) lithium load-bearing framework, electrolyte additives, solid electrolytes and surface coatings. "Surface coating is still a simple and effective way in these efforts," said Xiangbo Meng, a professor in the Department of Mechanical Engineering at the University of Arkansas and the study's newsletter author.
"Molecular layer deposition of (MLD) has recently become a new research direction, which was first put into practice in 2018," Meng said. "these polymer films precisely synthesized by MLD are more flexible than inorganic films and help to provide better protection, thereby improving the performance of lithium metal anodes."
Meng and his team have developed three lithium-ion polymer MLD processes and studied the protective effects of these polymer film coatings in an attempt to achieve long-term stable cycle performance with little formation of lithium dendrites and lithium electrode SEI.
"in this work, we developed for the first time a new type of lithium-containing cross-linked polymer material, a lithium ketone that can provide excellent protection for lithium metal anodes," Meng said. "We found that LiGL lithium ketone can be used as a special polymer protective film to cover the lithium metal anode."
According to him, this kind of LiGL MLD shows excellent protective effect on lithium electrode, that is, it can significantly inhibit lithium dendrite and reduce the formation of SEI. Numerical simulations and experiments also show that the MLD LiGL film is electrically insulating and ionic conductive.
In their study, the experimental data show that the lithium electrode coated with LiGL lithium ketone has excellent cycle stability. When the current density is 5 mA/cm2, and the area capacity is 1 mAh/cm2, the number of lithium stripping or plating cycles in the Li/Li symmetrical cell can reach more than 13600 without failure.
At present, the updated results show that the trouble-free cycle capacity has increased to more than 20000 lithium stripping / plating cycles (more than 10, 000 hours or more than one year). It is understood that this is the best cycle performance reported so far. Therefore, MLD LiGL technology lays a technical way to solve the problem of lithium anode.
"the properties of LiGL coatings, such as mechanical properties and electrical conductivity, are the basis for their excellent protection against lithium metal electrodes," Meng said. "the new LiGL we have developed represents a simple and effective solution to the existing problems of lithium negative electrodes and may pave the way for technically feasible lithium metal batteries."
