Lithium dendrite growth has always been a major problem affecting the safety of lithium-ion batteries based on liquid electrolytes. In theory, solid-state lithium metal batteries using ceramic materials as solid electrolyte (SSE) can effectively inhibit the growth of lithium dendrites, and batteries using lithium metal as the negative electrode have higher energy density. However, one of the main reasons hindering the large-scale application of solid state batteries is that, compared with liquid electrolyte batteries, lithium dendrites seem to be more likely to form in solid electrolyte at high current density due to the conductivity of solid electrolyte and internal defects such as holes, grain boundaries and micro cracks, which in turn induce internal short circuit and fire. Based on the above problems, researchers use a variety of characterization methods to study the internal mechanism of the growth and destructive behavior of lithium dendrites in solid-state batteries. Up to now, the mechanism is still ambiguous.

Recently, Ze You Science and Technology assisted the teams of Professor Zhang Liqiang, Professor Tang Yongfu and Professor Huang Jianyu of Yanshan University to observe and study the dynamic process of lithium dendrites penetrating LLZTO(Li6.4La3Zr1.4Ta0.6O12) solid electrolyte in microbatteries using the high resolution and in-situ real-time advantages of in-situ electron microscopy technology, proving that electrochemical mechanical stress is sufficient to drive lithium dendrite dendrite to grow faster, causing solid electrolyte rupture and puncture. At the same time, they found that new lithium nucleation sites are generated during each lithium insertion cycle, and new "dead lithium" is formed in the subsequent delithiation cycle; Thus, the main Coulomb efficiency decay mechanism in solid-state lithium metal batteries is explained. Based on the above research results, they proposed a battery improvement idea to improve the performance of solid-state lithium metal batteries by reducing the crack size and electronic conductivity in the solid electrolyte. Relevant research results are published in the international academic journal ACS Nano under the title of "In Situ Visualization of Lithium Penetration through Solid Electrolyte and Dead Lithium Dynamics in Solid-Stat Lithium Metal Batteries. Dr. Haiming Sun, School of Materials Science, Yanshan University is the first author of this paper.

Original Link: https://pubs.acs.org/doi/abs/10.1021/acsnano.1c04864

In-situ STM Combined with AFM Study on Kinetic Behavior of Li Dendrite Penetrating LLZTO in CO2 Atmosphere

Schematic Diagram of Lithium Dendrite Piercing Solid Electrolyte

Research Found, metal lithium is deposited on the surface and internal pores of the solid electrolyte, grain boundaries and other defect sites. When the lithium in the solid electrolyte reaches saturation, the great stress generated by electrochemically driven metal lithium deposition causes cracks in the solid electrolyte, which eventually leads to lithium dendrites penetrating the solid electrolyte. In the process of dendrite piercing, fragments of the solid electrolyte can be brought out, causing serious damage to the solid electrolyte. During the delithiation process, the lithium continues to peel off, and a lithium carbonate shell that cannot be decomposed (referred to as "dead lithium") eventually remains. In addition, the researchers also found that new dendrites growing at different sites during each cycle are an important mechanism for the formation of "dead lithium. The failure of the cell ultimately leads to a decrease in coulombic efficiency.