The factors that influence the electrochemical behavior of lithium metal anodes: electron transfer and Li-ion transport

Structured carbon-based hosts for the Li anode both improve the transport of Li-ions and reduce the electron transfer rate and have proven to be an effective way to suppress dendrite growth in lithium metal anodes. An in-depth understanding of these effects is needed to clarify the intrinsic electrochemical mechanism involved. We used the finite element method to simulate the two crucial processes controlling Li-ion behavior, electron transfer and Li-ion transport, and visualized the local deposition rate, the overpotential, and the Li-ion concentration in a three-dimensional (3D) Li//electrolyte//Li cell. Our analysis showed a competitive relationship between the rates of Li-ion transport and electron transfer. When the electron transfer rate is relatively slow, there are sufficient Li-ions available near the anode surface and the deposition behavior is controlled by electron transfer. However, when the number of Li-ions is low, Li-ion transport dominates the deposition process because it is unable to keep up with electron transfer, and this causes dendrite formation. Therefore, reducing the reactivity of the Li anode and accelerating Li-ion transport are the two key factors to produce uniform Li metal deposition on the anode, particularly under fast charging conditions and in practical use.