A Review of Functional Separators for Lithium Metal Battery Applications

Abstract

Lithium metal batteries are considered “rough diamonds” in electrochemical energy storage systems. Li-metal anodes have the versatile advantages of high theoretical capacity, low density, and low reaction potential, making them feasible candidates for next-generation battery applications. However, unsolved problems, such as dendritic growths, high reactivity of Li-metal, low Coulombic efficiency, and safety hazards, still exist and hamper the improvement of cell performance and reliability. The use of functional separators is one of the technologies that can contribute to solving these problems. Recently, functional separators have been actively studied and developed. In this paper, we summarize trends in the research on separators and predict future prospects.

Polydopamine-Based Polymer Layer for Enhanced Interfacial Properties of Hybrid Ceramic–Polymer Solid Electrolytes

“…For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 −3 to 10 −4 S cm −1 across the polymer separator, based on a MacMullen number of 10. 61 The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup. Another solid electrolyte, LIPON, has been successfully commercialized, with even lower conductivity of ∼10 −6 S cm −1 , by minimizing the thickness of the film to keep resistances reasonable.…”

“…While the choice of battery active materials is outside the scope of this work, this study has confirmed that a battery could be made from such composite solid electrolyte materials while satisfying each of these criteria. For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 –3 to 10 –4 S cm –1 across the polymer separator, based on a MacMullen number of 10 . The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup.…”

Polydopamine-Based Polymer Layer for Enhanced Interfacial Properties of Hybrid Ceramic–Polymer Solid Electrolytes

“…For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 −3 to 10 −4 S cm −1 across the polymer separator, based on a MacMullen number of 10. 61 The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup. Another solid electrolyte, LIPON, has been successfully commercialized, with even lower conductivity of ∼10 −6 S cm −1 , by minimizing the thickness of the film to keep resistances reasonable.…”

“…While the choice of battery active materials is outside the scope of this work, this study has confirmed that a battery could be made from such composite solid electrolyte materials while satisfying each of these criteria. For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 –3 to 10 –4 S cm –1 across the polymer separator, based on a MacMullen number of 10 . The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup.…”

Quantifying the Effect of Separator Thickness on Rate Performance in Lithium-Ion Batteries

“…The initial increase is roughly linear with a slope of 5.8 × 10 6 s m −1 and an extrapolated zero-L S τ-value of ∼150-200 s. This linear regime includes practically relevant separator thicknesses (commercial Li ion batteries tend to have separator thicknesses between 20 and 25 μm). [2][3][4]35 However, for L S above ∼65 μm, τ appears to saturate at a value of ∼600 s.…”

Enhanced Performance of Solid Polymer Electrolyte Separator Lithium Battery with Cellulose Acetate From Empty Palm Fruit Bunch Coated Al2O3-Polyacrylic Acid

“…This indicates that the Al2O3-PAA coated treatment on SPE4, contributes to increasing the charge storage and release capacity during the electrochemical process. The electrochemical stability of the separator also improves ion transport and reduces resistance during charge-discharge cycles [43][44]. The Al2O3-PAA coated treatment can affect the ionization of surface carboxylic acid groups on the separator.…”

Polydopamine-Based Polymer Layer for Enhanced Interfacial Properties of Hybrid Ceramic–Polymer Solid Electrolytes

“…For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 −3 to 10 −4 S cm −1 across the polymer separator, based on a MacMullen number of 10. 61 The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup. Another solid electrolyte, LIPON, has been successfully commercialized, with even lower conductivity of ∼10 −6 S cm −1 , by minimizing the thickness of the film to keep resistances reasonable.…”

“…While the choice of battery active materials is outside the scope of this work, this study has confirmed that a battery could be made from such composite solid electrolyte materials while satisfying each of these criteria. For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 –3 to 10 –4 S cm –1 across the polymer separator, based on a MacMullen number of 10 . The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup.…”

Quantifying the Effect of Separator Thickness on Rate Performance in Lithium-Ion Batteries

“…The initial increase is roughly linear with a slope of 5.8 × 10 6 s m −1 and an extrapolated zero-L S τ-value of ∼150-200 s. This linear regime includes practically relevant separator thicknesses (commercial Li ion batteries tend to have separator thicknesses between 20 and 25 μm). [2][3][4]35 However, for L S above ∼65 μm, τ appears to saturate at a value of ∼600 s.…”

Enhanced Performance of Solid Polymer Electrolyte Separator Lithium Battery with Cellulose Acetate From Empty Palm Fruit Bunch Coated Al2O3-Polyacrylic Acid

“…This indicates that the Al2O3-PAA coated treatment on SPE4, contributes to increasing the charge storage and release capacity during the electrochemical process. The electrochemical stability of the separator also improves ion transport and reduces resistance during charge-discharge cycles [43][44]. The Al2O3-PAA coated treatment can affect the ionization of surface carboxylic acid groups on the separator.…”

Polydopamine-Based Polymer Layer for Enhanced Interfacial Properties of Hybrid Ceramic–Polymer Solid Electrolytes

“…For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 −3 to 10 −4 S cm −1 across the polymer separator, based on a MacMullen number of 10. 61 The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup. Another solid electrolyte, LIPON, has been successfully commercialized, with even lower conductivity of ∼10 −6 S cm −1 , by minimizing the thickness of the film to keep resistances reasonable.…”

“…While the choice of battery active materials is outside the scope of this work, this study has confirmed that a battery could be made from such composite solid electrolyte materials while satisfying each of these criteria. For reference, typical lithium-ion batteries with a liquid electrolyte and separator have conductivity ∼10 –3 to 10 –4 S cm –1 across the polymer separator, based on a MacMullen number of 10 . The conductivity of the composite solid electrolyte in this study is sufficiently close to that of the traditional liquid electrolyte to make a reasonable alternative to the traditional setup.…”

Quantifying the Effect of Separator Thickness on Rate Performance in Lithium-Ion Batteries

“…The initial increase is roughly linear with a slope of 5.8 × 10 6 s m −1 and an extrapolated zero-L S τ-value of ∼150-200 s. This linear regime includes practically relevant separator thicknesses (commercial Li ion batteries tend to have separator thicknesses between 20 and 25 μm). [2][3][4]35 However, for L S above ∼65 μm, τ appears to saturate at a value of ∼600 s.…”

Enhanced Performance of Solid Polymer Electrolyte Separator Lithium Battery with Cellulose Acetate From Empty Palm Fruit Bunch Coated Al2O3-Polyacrylic Acid

“…This indicates that the Al2O3-PAA coated treatment on SPE4, contributes to increasing the charge storage and release capacity during the electrochemical process. The electrochemical stability of the separator also improves ion transport and reduces resistance during charge-discharge cycles [43][44]. The Al2O3-PAA coated treatment can affect the ionization of surface carboxylic acid groups on the separator.…”