Breaking the bottleneck of solid electrolytes in 18650 lithium ion battery 3.7v, China University of Science and Technology proposes atomic-level solutions

　　Current mainstream 18650 lithium ion battery 3.7v 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 18650 lithium ion battery 3.7v 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. By conducting atomic-level observations of the impurity phase in a solid electrolyte with a classic perovskite structure, the researchers observed that although the impurities and the solid electrolyte have very different structures, their atoms can 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.

　　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. "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, and it is so common that it is ignored by people most of the time. However, 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 close 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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