Energy Band Specific to Injected Li-Ion-Induced Formation of Lithium Dendrites in Garnet Solid Electrolytes

As one of the most significant challenges in solid-state batteries, thorough investigation is necessary on the formation process of lithium dendrites in solid-state electrolytes. Here, we reveal that the growth of lithium dendrites in solid electrolytes is a physical-electrochemical reaction process caused by injected lithium ions and electron carriers, which requires a low electrochemical potential. A unique energy band specific to injected Li ions is identified at the bottom of the conduction band, which can be occupied by electron carriers from low-potential electrodes, leading to dendrite formation. In this case, it is quantitatively determined that the employed anodes with higher working voltages (>0.2 V versus Li/Li⁺) can effectively prevent dendrite formation. Moreover, lithium dendrite formation exclusively occurs during the charging process (i.e., lithium plating), where lithium ions meet electrons at mixed conductive grain boundaries under highly reductive potentials. The proposed model has significant scientific significance and application value.