Breakthrough in solid state lithium battery research

On August 21, the top academic journal matter published the latest achievements of Professor Ma Cheng and his collaborators from University of science and technology of China. This achievement proposes a new strategy, which can effectively solve the key problem of poor contact between electrode materials and solid electrolyte in the next generation of solid-state lithium batteries. The synthesized solid-state composite electrode shows excellent capacity and rate performance.
At present, the mainstream lithium batteries use liquid electrolyte, which has potential safety hazards such as fire, and the energy stored in a specific volume is limited. However, the next generation of solid-state lithium batteries that can solve these problems still have many unsolved problems. Replacing organic liquid electrolytes in traditional lithium-ion batteries with solid electrolytes can greatly alleviate the safety problem, and is expected to break through the "glass ceiling" of energy density. However, the mainstream electrode materials are also solid materials. Because the contact between the two solid materials is almost impossible to be as full as the solid-liquid contact, it is difficult to achieve good electrode electrolyte contact for the battery using solid electrolyte at present, and the overall performance of the battery is not satisfactory.
Ma Cheng's team and their collaborators observed the impurity phase in a typical perovskite structure solid electrolyte at atomic level. Although the structure of impurity and solid electrolyte is very different, the researchers observed that their atoms can be arranged in the form of mutual epitaxy at the interface. After a series of detailed structural and chemical analysis, it was found that this impurity phase has the same structure as the high capacity lithium rich layered electrode.
Based on the observation results, the amorphous powder with the same composition as perovskite solid electrolyte was crystallized on the surface of lithium rich layered particles, and the full and close contact between the two solid materials was successfully achieved in the new composite electrode. The rate performance of the solid-solid composite electrode is comparable to that of the solid-liquid composite electrode. More importantly, the researchers also found that the epitaxial solid-solid contact can tolerate large lattice mismatch, so their proposed strategy can be applied to a variety of perovskite solid-state electrolytes and layered electrodes.