Lithium Dendrite Suppression through Controlled Mass Transfer

Lithium dendrite formation is a critical challenge that limits the lifetime of lithium (Li) metal batteries including lithium oxygen, and lithium sulfur systems. Dendrite growth occurs at the interface between the electrolyte and the Li metal anode. The formation of dendrites affects the local transport properties, the scale of the critical physics of the anode, leads to increased Joule heating and eventual breakage of the dendrites, which can cause short circuits leading to overheating and possible fires. Dendrite formation also decreases the Li available for the electrochemical reactions of the battery, which causes a decrease in cell capacity. In addition to Li metal batteries, dendrite growth is also a problem for other battery chemistries, such as Li-ion, NaS and NiCd. Among previous experimental studies, it has been shown that the dendrites in Li batteries can form one of two structures depending on the operating conditions. Under high current conditions, dendrite formation is typically dense and considered mossy or bush-like in structure; while under low current conditions dendrites form dense needle-like structures. In addition to charging current, many other factors are reported to influence dendrite growth. A close relation between Li ion mass transfer and dendrite growth rate have been shown; while other groups have found a strong influence between convection effects and the morphology of the dendritic structure. Measuring dendrite growth in situ is challenging, and examining the dendrites post mortem is difficult as they can fall apart during disassembly. To better understand dendrite growth and morphology, computational modeling can be used to investigate the electrode-electrolyte interface and how operating conditions and battery design effect dendrite growth and morphology. In this work, we use a Lagrangian particle based method known as smoothed particle hydrodynamics (SPH) to simulate the reactive transport in the interfacial region to understand Li ion transport effects on dendrite growth. This includes investigation of material properties and battery design, including the use of hybrid electrolytes and separators to restrict Li ion transport. Further studies are conducted to consider how operation and charging rates effect growth. Results of these computational studies show that restricted Li ion transport can suppress dendrite growth without sacrificing battery performance. This can be accomplished by changing the materials of electrolyte or using hybrid electrolyte designs. Additionally the charging profile can also be used to effectively suppress dendrites.