USTC breaks the bottleneck in 18650 lithium-ion battery solid electrolyte research

　　Recently, the top academic journal "Matter" published the latest results of Professor Ma Cheng of the University of Science and Technology of China and his collaborators. They proposed a new strategy that can effectively solve the key problem of poor contact between electrode materials and solid electrolytes in the next generation of solid-state lithium batteries. problem, the synthesized solid-state composite electrode exhibits excellent capacity and rate performance.

　　Compared with the commonly used cold pressing method, the new solution can achieve full and close contact between the solid electrolyte and the electrode at the atomic scale. The atomic-resolution electron micrograph pictured here directly confirms this close contact. Photo courtesy of University of Science and Technology of China

　　According to reports, current mainstream lithium batteries use liquid electrolytes, which pose safety risks such as fires, and the energy that can be stored in a specific volume is limited. However, there are still many unsolved problems in the next generation of solid-state lithium batteries that can solve these problems.

　　Replacing the organic liquid electrolyte in traditional lithium-ion batteries with solid electrolytes can greatly alleviate safety issues and is expected to break through the "glass ceiling" of energy density. However, mainstream electrode materials are also solid substances. Since the contact between two solid substances is almost impossible to be as full as solid-liquid contact, current batteries using solid electrolytes are difficult to achieve good electrode-electrolyte contact, and the overall performance of the battery is also unsatisfactory.

　　"The electrode-electrolyte contact problem of solid-state batteries is like the short plate of a wooden barrel." Professor Ma Cheng said, "In recent years, researchers have developed a variety of electrodes and solid electrolytes with excellent performance, but it is difficult to achieve good performance between the two. contact, the transmission efficiency of lithium ions is greatly limited."

　　The approach of Ma Cheng's team and his collaborators holds promise for solving this conundrum. They conducted atomic-level observations of the impurity phase in a solid-state electrolyte with a classic perovskite structure. Although the structures of the impurities and the solid-state electrolyte were very different, the researchers observed that their atoms could be arranged in a mutually epitaxial manner at the interface.

　　After a series of detailed structural and chemical analyses, the researchers found that this impurity phase has the same structure as the high-capacity lithium-rich layered electrode. In other words, the above-mentioned classical solid-state electrolyte can be crystallized using the atomic structure of a high-performance cathode as a template to form a tight interface at the atomic scale.

　　"This is a surprise." said Li Fuzhen, the first author of the article and a master's student at the University of Science and Technology of China. "The existence of defects in materials is a very common phenomenon. It is so common that it is ignored by people most of the time. However, in After observing them in detail, we discovered unexpected epitaxial behavior, which inspired our strategies for improving solid-solid contacts."

　　Using the observation results, the researchers crystallized amorphous powder with the same composition as the perovskite solid electrolyte on the surface of the lithium-rich layered particles, and successfully achieved sufficient and tight contact between the two solid-state materials in the new composite electrode. touch. Solving the electrode-electrolyte contact problem, the rate performance of this solid-solid composite electrode is comparable to that of solid-liquid composite electrodes.

　　More importantly, the researchers also found that this epitaxial solid-solid contact can tolerate large lattice mismatches, so their proposed strategy can be applied to a variety of perovskite solid-state electrolytes and layered electrodes.

　　"This work points to a new direction worth exploring." Professor Ma Cheng said, "Applying this principle to other important materials may lead to better battery performance and lead to more interesting scientific questions. We are Quite looking forward to it.”

　　The research team will continue to explore along this direction and apply their proposed strategy to other high-capacity, high-potential cathodes.

　　The cooperative team includes the team of Academician Nan Cewen of Tsinghua University and Dr. Lin Zhou of Ames Laboratory in the United States. "Matter" is a new flagship academic journal launched by Cell Publishing Group.

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