Ternary Poly(ethylene oxide)/Poly(l,l-lactide) PEO/PLA Blends as High-Temperature Solid Polymer Electrolytes for Lithium Batteries

Abstract

Lithium batteries are in high demand in different technological fields. However, the operating temperature is required to be below 70 °C, and this limits their use in applications demanding high-energy rechargeable batteries that are able to operate at temperatures above 100 °C. Poly(ethylene oxide) (PEO) is, currently, the reference solid polymer electrolyte (SPE) employed in solid-state lithium batteries. However, the application of PEO at higher temperatures is restricted due to the loss of mechanical properties. In this article, we show that the polymer blending strategy of blending PEO with poly(L,L-lactide) (PLA) allows extending its use in batteries at high temperatures (100 °C). This improvement is due to the mechanical reinforcement of PEO solid electrolytes associated with the presence of PLA crystals. Thus, two solid electrolyte systems based on PEO/PLA blends with either a LiTFSI salt or a lithium single-ion polymer (poly(lithium-1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethanesulfonyl)imide), PLiMTFSI) were investigated and compared. Differential scanning calorimetry (DSC) results indicate that regardless of the concentration of LiTFSI or PLiMTFSI in the blend, crystals of PLA are present with melting peaks at 160−170 °C and the lithium salt distributes preferentially in the PEOrich amorphous phases. The ionic conductivity is negatively affected by the incorporation of PLA in the blends. However, at high temperatures (>70 °C), ionic conductivities of ∼10 −4 S cm −1 were obtained for both systems. DMTA results showed that PLA addition increases the mechanical properties of the electrolytes, yielding storage modulus values of ∼10 6 Pa for the PEO/PLA/ LiTFSI blend and ∼10 7 Pa or higher for the PEO/PLA/PLiMTFSI blend at high temperatures (100 °C). Finally, both ternary blends were compared in a symmetrical lithium battery at 100 °C, and the single-ion conducting PEO/PLA/PLiMTFSI system presented lower overpotentials, which is reflected in a lower polarization inside the lithium battery.

Facile Access to CO2‐Sourced Polythiocarbonate Dynamic Networks And Their Potential As Solid‐State Electrolytes For Lithium Metal Batteries

“…[24] However, it has certain disadvantages, such as crystallization that restricts ionic conductivity, and a decrease in mechanical properties depending on the concentration of lithium salt in the system. [25] Polycarbonates have been studied as another polymeric matrix in SPEs for lithium batteries, [26][27][28] as they have shown good ionic conductivity, electrochemical stability and a higher transport number than in the case of PEO. The carbonate group shows weaker coordination with lithium cations compared to the ether groups, which is reflected in increased electrochemical properties.…”

“…The most studied polymer for this application is polyethylene oxide (PEO), due to its great capacity to dissolve lithium salts [24] . However, it has certain disadvantages, such as crystallization that restricts ionic conductivity, and a decrease in mechanical properties depending on the concentration of lithium salt in the system [25] . Polycarbonates have been studied as another polymeric matrix in SPEs for lithium batteries, [26–28] as they have shown good ionic conductivity, electrochemical stability and a higher transport number than in the case of PEO.…”

Polyethylene Oxide/Sodium Sulfonamide Polymethacrylate Blends as Highly Conducting Single-Ion Solid Polymer Electrolytes

“…In this work, polymer blending as an inexpensive and practical technique for the development of materials was employed to develop sodium single-ion conducting polymer electrolytes. The successful strategy of high-conducting single-ion conducting polymer blends for lithium metal batteries has been previously reported. − Here, we applied a similar method to the design of sodium single-ion polymer electrolytes with high conductivity. Thus, single-ion polymer electrolytes were prepared by blending polyethylene oxide (PEO) and poly­(sodium 1-[3-(methacryloyloxy) propylsulfonyl]-1-(trifluoromethanesulfonyl) imide) (PNaMTFSI).…”

Single-Ion Conducting Polyurethane-Ester Solid Polymer Electrolyte Membrane toward Lithium Metal Batteries

“…Researchers have been interested in polymer systems comprising −CH 2 CH 2 O– (−EO−) moieties for all-solid polymer electrolytes in LIBs. − Polyethylene oxide (PEG) has ether coordination sites that are capable of dissociating various salts, together with flexible backbones that facilitate ionic diffusion . However, the large crystalline regions of PEG hinder ion transport at room temperature, and the polymer loses dimensional stability above the melting temperature (∼65 °C) . In short, the development of PEG-based SICPEs has been hindered by the issue that it is difficult for the designed single-ion conductors to exhibit excellent ionic conductivity and mechanical properties over an extensive temperature range …”