Effects of Polymer Coating Mechanics at Solid‐Electrolyte Interphase for Stabilizing Lithium Metal Anodes

Abstract

Lithium metal batteries are next‐generation energy storage devices that rely on the stable electrodeposition of lithium metal during the charging process. The major challenge associated with this battery chemistry is related to the uneven deposition that leads to dendritic growth and poor coulombic efficiency (CE). A promising strategy for addressing this challenge is utilizing a polymer coating on the anodic surface. While several works in the past have evaluated polymer coatings, the requirements for polymer design are still unclear. In this work, the effect of polymer dynamics on lithium metal deposition is specifically investigated. Electrolyte (solvent) blocking perfluoropolyether polymer networks with evenly spaced H‐bonding sites of various strengths are designed, resulting in significant differences in the molecular ordering, as analyzed by X‐ray scattering measurements. The differences in the H‐bonding strength directly impact the mechanical properties of these materials, thus providing a controlled set of samples with a range of polymer dynamics for electrodeposition studies. Finally, a systematic evaluation of the lithium metal electrodeposition quality with these polymers as anodic coating shows that polymers with flowability or faster polymer dynamics exhibit higher CE. These experimental findings provide rational design principles for soft polymer coatings on lithium metal anodes.

A Solution‐Processable High‐Modulus Crystalline Artificial Solid Electrolyte Interphase for Practical Lithium Metal Batteries

“…In addition to the aforementioned practical considerations, the physical and chemical properties of ASEIs can be rationally designed to overcome the drawbacks of native SEIs. Several key features of ASEIs have been identified as essential to protect Li metal anode, [ 4,28,30–34 ] such as high ionic conductivity, good mechanical stability and electrolyte‐phobic feature. As elaborated in the previous reports, [ 24,30,32 ] the incorporation of all the desired properties into one multifunctional ASEI material system can be challenging; therefore, synergistic effects are needed to further achieve realistic Li metal batteries.…”

“…[3][4][5][6] Generally, the native SEIs in conventional/ commercial carbonate electrolytes are mechanically brittle, heterogeneous in ionic conduction, and fail to passivate the Li surface during long-term cycling.To solve these issues associated with Li metal anodes, several strategies have been proposed, such as liquid electrolyte engineering, [7][8][9][10][11][12][13][14] solid-state electrolytes, [15][16][17][18] Li metal hosts, [5,19] or pretreatment of Li metal. [20][21][22] Artificial SEIs (ASEIs) [23][24][25][26][27][28] have garnered increasing attention due to their potential compatibility with commercial electrolytes [24] and the possibility for scalable manufacturing. [23] Particularly, it is critical to develop production-friendly solution-processable ASEIs for Li metal anodes, so that the ASEIs can be implemented through scalable coating methods, [29] such as spray coating, slot-die coating, gravure coating, or inkjet printing.In addition to the aforementioned practical considerations, the physical and chemical properties of ASEIs can be rationally designed to overcome the drawbacks of native SEIs.…”

“…[23] Particularly, it is critical to develop production-friendly solution-processable ASEIs for Li metal anodes, so that the ASEIs can be implemented through scalable coating methods, [29] such as spray coating, slot-die coating, gravure coating, or inkjet printing.In addition to the aforementioned practical considerations, the physical and chemical properties of ASEIs can be rationally designed to overcome the drawbacks of native SEIs. Several key features of ASEIs have been identified as essential to protect Li metal anode, [4,28,[30][31][32][33][34] such as high ionic conductivity,The solid electrolyte interphase (SEI) has been identified as a key challenge for Li metal anodes. The brittle and inhomogeneous native SEI generated by parasitic reactions between Li and liquid electrolytes can devastate battery performance; therefore, artificial SEIs (ASEIs) have been proposed as an effective strategy to replace native SEIs.…”

“…To solve these issues associated with Li metal anodes, several strategies have been proposed, such as liquid electrolyte engineering, [7][8][9][10][11][12][13][14] solid-state electrolytes, [15][16][17][18] Li metal hosts, [5,19] or pretreatment of Li metal. [20][21][22] Artificial SEIs (ASEIs) [23][24][25][26][27][28] have garnered increasing attention due to their potential compatibility with commercial electrolytes [24] and the possibility for scalable manufacturing. [23] Particularly, it is critical to develop production-friendly solution-processable ASEIs for Li metal anodes, so that the ASEIs can be implemented through scalable coating methods, [29] such as spray coating, slot-die coating, gravure coating, or inkjet printing.…”

“…In addition to the aforementioned practical considerations, the physical and chemical properties of ASEIs can be rationally designed to overcome the drawbacks of native SEIs. Several key features of ASEIs have been identified as essential to protect Li metal anode, [4,28,[30][31][32][33][34] such as high ionic conductivity,…”