Solid Polymer Electrolytes Based on Cross-Linked Polybenzoxazine Possessing Poly(ethylene oxide) Segments Enhancing Cycling Performance of Lithium Metal Batteries

Abstract

Solid polymer electrolytes (SPEs) are suitable materials for safety enhancements of high-energy-density lithium metal batteries. Low ionic conductivity and poor interfacial compatibility could be the major issues to be addressed for SPEs. In this work, a cross-linked polybenzoxazine polymer with poly(ethylene oxide) (PEO) segments (CR-PEO-PBz) has been synthesized and used as a polymeric matrix for preparation of SPEs. The cross-linked structure contributes to suppression of PEO crystallization. PEO-PBz is also used as a binder to reduce the interfacial resistance between the electrode and the electrolyte. The features enhance the lithium ion transportation and increase the ionic conductivity of the corresponding SPE (5.32 × 10 −1 mS cm −1 at 60 °C). CR-PEG-PBz also exhibits the ability to prevent lithium dendrite growth with promotion of uniform lithium deposition. The LiFePO 4 /Li coin cells made with the SPEs demonstrate a high initial capacity of 142 mAh g −1 at 0.2C and 60 °C and a 93% initial capacity after a 100-cycle test. The cells could be operated at 30, 40, and 50 °C, thus proving the capability of the SPE at various temperatures.

Formaldehyde-Free Synthesis of Fully Bio-Based Multifunctional Bisbenzoxazine Resins from Natural Renewable Starting Materials

“… − Holly and Cope prepared the first monofunctional BZ, 3,4-dihydro-2 H -1,3-benzoxazine, through Mannich condensation . Although the chemical structures of PBZs are similar to those of traditional phenolic resins, PBZs are generally prepared by using simple and self-catalyzed polymerization processes and display good heat resistance, high degradation and glass transition ( T g ) temperatures, near-zero volumetric shrinkage during polymerization, excellent flame retardancy, good mechanical properties, low dielectric constants, water absorption properties, and variable surface free energies. ,− In addition, high flexibility in the molecular design of BZ resins allows a variety of physical and mechanical properties to be introduced into the resulting PBZ materials. − Moreover, the properties of PBZs lead to many potential applications in, for example, adsorbents, metal capture, energy storage, gas uptake, shape-memory and self-healing polymers, anticorrosion coatings, adhesives, and electronic materials. − The syntheses and characteristics of mono-, bi-, tri-, and tetrafunctional BZs have been investigated in detail by many research groups. ,,,,,,, In general, monofunctionalized BZs tend to form linear polymers of relatively lower molecular weight, while bifunctional BZs form cross-linked macromolecules featuring more stable networks …”

Poly(ionic liquid)@PEGMA Block Polymer Initiated Microphase Separation Architecture in Poly(ethylene oxide)-Based Solid-State Polymer Electrolyte for Flexible and Self-Healing Lithium Batteries

“…Organic polymer electrolytes have the characteristics of light weight, good flexibility, and easy processing as a substitute for liquid electrolyte. Meanwhile, the utilization of a lithium anode is put on the agenda again, which presents pleasing specific capacity and a strong advantage in redox potential. − Nevertheless, the poor ion conductivity, the low Li + transference number, and growth of dendritic lithium still seriously hindered the pace of SPEs’ industry development …”

Safe and Energy-Dense Flexible Solid-State Lithium–Oxygen Battery with a Structured Three-Dimensional Polymer Electrolyte

“…Rechargeable lithium–oxygen batteries (LOBs) have the highest theoretical energy density (about 3500 Wh kg –1 ) among existing metal-based chemical battery systems and are expected to be a candidate for green energy storage devices. − Nevertheless, there are still several issues limiting the practical application of LOBs. One major bottleneck relates to the use of organic liquid electrolytes, which leads to several safety issues such as volatility, flammability, and leakage of organic solvents. − In addition, the diffusion of oxygen in the liquid LOB system is limited by the dissolved oxygen gas in the air electrode filled with an organic liquid electrolyte, which results in large polarization, poor rate performance, and weak reversibility. − Safer and reliable electrolytes are urgently needed to substitute for the organic liquid electrolytes currently used. Compared with inorganic solid electrolytes, polymer electrolytes display stronger processing adaptation and better flexibility and thus serve as a better candidate and have great potential applications on flexible power sources. − However, polymer electrolytes still present various concerns limiting their widespread use.…”