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Visualization of solid state battery in action via operando TEM

The liquid electrolytes that are typically used in traditional Li-ion batteries are flammable, especially at higher operating voltages and temperatures. By contrast, an all-solid-state battery (ASSB) makes use of a solid electrolyte, which reduces the risk of flammability. However, the presence of the solid−solid electrolyte−electrode interface in ASSBs introduces different challenges from those of the traditional liquid−solid electrode−electrolyte interface. First, in batteries containing liquid electrolytes, the entire surface of the electrode particles is wetted by electrolytes, whereas the electrode particles and solid electrolytes in ASSBs are connected primarily at point contacts, which are limited in terms of their numbers (as not all electrode particles are in direct contact with electrolyte particles); therefore, ionic transport is basically restricted, diminishing the specific capacity of these batteries. Decomposition reactions at electrode−electrolyte interfaces during battery cycling causing the formation of passivating layers as well as electrode volume changes during battery cycling result in the loss of contacts between the electrode and electrolyte particles, further decreasing direct ion exchange pathways. Second, inhomogeneous (de)lithiation through point contacts can induce strain, which affects electrode mechanical integrity leading to capacity fade.

With operando transmission electron microscopy by visualizing the solid–solid electrode–electrolyte interface of silicon active particles and lithium oxide solid electrolyte as a model system, we show that (de)lithiation (battery cycling) does not require all particles to be in direct contact with electrolytes across length scales of a few hundred nanometers. A facile lithium redistribution that occurs between interconnected active particles indicates th

ACS Appl. Energy Mater. 2020, 3, 6, 5101–5106

Publication Date: May 8, 2020