Lithium Dendrite Formation in Li-ion Batteries
A paper has been published about how the morphology of the Li deposits leads to improved Coulombic efficiency. The study was performed using an operando electrochemical cell. An in-situ liquid stage was used for direct observation of the growth phenomena, which enabled direct correlation of the Li deposits with the presence of additives.
The paper is written by a team from Pacific Northwest National Laboratory, Florida State University, Penn State University and the University of Washington: B. Layla Mehdi, Andrew Stevens, Jiangfeng Qian, Chiwoo Park, Wu Xu, Wesley A. Henderson, Ji-Guang Zhang, Karl T. Mueller and Nigel D. Browning. The paper is published by nature.com and available to read online.
Increasing Energy Density
Replacing the graphite anode with a Li metal anode is way of increasing the energy density of lithium Li-ion batteries. However, the use of Li metal is related to issues with dendrite growth and low Coulombic efficiency (CE), which limits its practical use.
Testing Electrolytes and Li Metal
In this study, operando electrochemical scanning transmission electron microscopy (STEM) was used to image the deposition/stripping of Li at the anode-electrolyte interface in a Li-based battery. It was found that using a non-aqueous electrolyte containing a small quantity of H2O as an additive produces significantly different deposition/stripping properties, compared to a “dry” electrolyte under the same electrochemical conditions.
Effect of Additives on Li Dendrite Formation
The study showed that the electrolyte with the additive deposits more Li during the first cycle. The grain sizes of the Li deposits are significantly larger and more variable. Upon discharge, the Li stripping is more complete, i.e. there is a higher cycling CE. This suggests that larger grain sizes signify better performance, with more uniform Li deposition. There is less Li dendrite formation overall, and a reduction in side reactions with electrolyte components. This indicates the potential for applications of Li metal in battery technology.
In-Situ Electrochemical Measurements
The measurements were performed using the Protochips Poseidon microfluidic in-situ electrochemical stage. This enables electrochemical measurements to be observed, simultaneously with video showing the dynamics of the Li dendrite deposition/stripping process at the Pt electrode surface in a liquid environment.
The use of in-situ liquid stages for TEM together with electrochemistry enables first-hand observation of nucleation/growth phenomena and biological systems. This gives unique insights into molecular-level interactions. In this study, it enabled direct correlation of deviations in the microstructure evolution with the presence of the additive.
Read the Scientific Paper
A full description of the method and discussion of the results is in the scientific paper, which is published by Nature.com and available to read online: