Stable cross-linked gel terpolymer electrolyte containing methyl phosphonate for sodium ion batteries

Challenges and Breakthroughs in Enhancing Temperature Tolerance of Sodium-Ion Batteries

Lithium-based batteries (LBBs) have been highly researched and recognized as a mature electrochemical energy storage (EES) system in recent years. However, their stability and effectiveness are primarily confined to room temperature conditions. At temperatures significantly below 0 °C or above 60 °C, LBBs experience substantial performance degradation. Under such challenging extreme contexts, sodium-ion batteries (SIBs) emerge as a promising complementary technology, distinguished by their fast dynamics at low-temperature regions and superior safety under elevated temperatures. Notably, developing SIBs suitable for wide-temperature usage still presents significant challenges, particularly for specific applications such as electric vehicles, renewable energy storage, and deep-space/polar explorations, which requires a thorough understanding of how SIBs perform under different temperature conditions. By reviewing the development of wide-temperature SIBs, the influence of temperature on the parameters related to battery performance, such as reaction constant, charge transfer resistance, etc., is systematically and comprehensively analyzed. The review emphasizes challenges encountered by SIBs in both low and high temperatures while exploring recent advancements in SIB materials, specifically focusing on strategies to enhance battery performance across diverse temperature ranges. Overall, insights gained from these studies will drive the development of SIBs that can handle the challenges posed by diverse and harsh climates.

Tailoring the Properties of Gel Polymer Electrolytes for Sodium-Ion Batteries Using Ionic Liquids: A Review

Ionic liquids are an extraordinary group of compounds, fully ionic in structure like inorganic salts but with low melting points, that resemble organic molecular solvents. Their chemical, electrochemical, and thermal stability is what draws the attention and enables their use in many applications, including electrochemical power sources. Even though they are no longer considered eco-friendly because of nonnegligible toxicity and long bioaccumulation, they can still be efficiently recovered, purified, and reused. These attributes can be harvested to enhance the properties of gel polymer electrolytes for the emerging sodium-ion batteries. The variety of anions and cations for ILs and their influence on the final properties of the compound opens the road to tuning the properties of gel polymer electrolytes. Ionic liquids as plasticizers constitute a major part of gel polymer electrolytes (average of 70 wt%) and hence, they affect the fundamental properties of gel electrolytes like ionic conductivity and electrochemical window. They also improve the safety features of sodium-ion batteries, which is relevant for their anticipated applications in stationary energy storage and electric vehicles. The presented review paper aims to explain the relationship between the cation and anion in ionic liquid and the properties of gel electrolytes for sodium-ion batteries.

Effect of Layered Aminovanadic Oxalate Phosphate on Flame Retardancy of Epoxy Resin

To alleviate the fire hazard of epoxy resin (EP), layered ammonium vanadium oxalate-phosphate (AVOPh) with the structural formula of (NH₄)₂[VO(HPO₄)]₂(C₂O₄)·5H₂O is synthesized using the hydrothermal method and mixed into an EP matrix to prepare EP/AVOPh composites. The thermogravimetric analysis (TGA) results show that AVOPh exhibits a similar thermal decomposition temperature to EP, which is suitable for flame retardancy for EP. The incorporation of AVOPh nanosheets greatly improves the thermal stability and residual yield of EP/AVOPh composites at high temperatures. The residue of pure EP is 15.3% at 700 °C. In comparison, the residue of EP/AVOPh composites is increased to 23.0% with 8 wt% AVOPh loading. Simultaneously, EP/6 wt% AVOPh composites reach UL-94 V1 rating (t₁ + t₂ =16 s) and LOI value of 32.8%. The improved flame retardancy of EP/ AVOPh composites is also proven by the cone calorimeter test (CCT). The results of CCT of EP/8 wt% AVOPh composites show that the peak heat release rate (PHHR), total smoke production (TSP), peak of CO production (PCOP), and peak of CO₂ production (PCO₂P) decrease by 32.7%, 20.4%, 37.1%, and 33.3% compared with those of EP, respectively. This can be attributed to the lamellar barrier, gas phase quenching effect of phosphorus-containing volatiles, the catalytic charring effect of transition metal vanadium, and the synergistic decomposition of oxalic acid structure and charring effect of phosphorus phase, which can insulate heat and inhibit smoke release. Based on the experimental data, AVOPh is expected to serve as a new high-efficiency flame retardant for EP.

Gel Polymer Electrolytes Design for Na-Ion Batteries

Na-ion battery has the potential to be one of the best types of next-generation energy storage devices by virtue of their cost and sustainability advantages. With the demand for high safety, the replacement of traditional organic electrolytes with polymer electrolytes can avoid electrolyte leakage and thermal instability. Polymer electrolytes, however, suffer from low ionic conductivity and large interfacial impedance. Gel polymer electrolytes (GPEs) represent an excellent balance that combines the advantages of high ionic conductivity, low interfacial impedance, high thermal stability, and flexibility. This short review summarizes the recent progress on gel polymer Na-ion batteries, focusing on different preparation approaches and the resultant physical and electrochemical properties. Reasons for the differences in ionic conductivity, mechanical properties, interfacial properties, and thermal stability are discussed at the molecular level. This Review may offer a deep understanding of sodium-ion GPEs and may guide the design of intermolecular interactions for high-performance gel polymer Na-ion batteries.

Polymer Electrolytes for Lithium-Ion Batteries Studied by NMR Techniques

This review is devoted to different types of novel polymer electrolytes for lithium power sources developed during the last decade. In the first part, the compositions and conductivity of various polymer electrolytes are considered. The second part contains NMR applications to the ion transport mechanism. Polymer electrolytes prevail over liquid electrolytes because of their exploitation safety and wider working temperature ranges. The gel electrolytes are mainly attractive. The systems based on polyethylene oxide, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethylene glycol) diacrylate, etc., modified by nanoparticle (TiO₂, SiO₂, etc.) additives and ionic liquids are considered in detail. NMR techniques such as high-resolution NMR, solid-state NMR, magic angle spinning (MAS) NMR, NMR relaxation, and pulsed-field gradient NMR applications are discussed. ¹H, ⁷Li, and ¹⁹F NMR methods applied to polymer electrolytes are considered. Primary attention is given to the revelation of the ion transport mechanism. A nanochannel structure, compositions of ion complexes, and mobilities of cations and anions studied by NMR, quantum-chemical, and ionic conductivity methods are discussed.

Effects of Comonomers on the Performance of Stable Phosphonate-Based Gel Terpolymer Electrolytes for Sodium-Ion Batteries with Ultralong Cycling Stability

Gel polymer electrolyte (GPE) is one of the most promising alternatives to solve the bottlenecks of nonaqueous liquid electrolytes such as decomposition, safety hazards, and growth of dendrites. In this work, three novel methyl phosphonate-based crosslinking gel terpolymer electrolytes with different comonomers are designed and prepared by in situ radical polymerization. The gel polymer electrolytes have excellent thermal stability, wide electrochemical windows (≥4.9 V), and high ionic conductivities (±3 mS cm^-1), and may be used as less-flammable electrolytes for sodium-ion batteries. ³¹P NMR spectra, Arrhenius plot, and density functional theory (DFT) calculations confirm that multifunctional phosphonate structural units promote the dissociation of NaClO₄ and help to transport the sodium ions freely in the polymer framework. X-ray photoelectron spectroscopy (XPS) results show that the gel polymer electrolytes have the capability of inhibiting liquid electrolyte decomposition and the formation of the stable solid electrolyte interphase (SEI) film. The Na₃V₂(PO₄)₃/GPE/Na cells exhibit better ultralong cycling stability and enhanced temperature performance than those of liquid cells. Strikingly, GPE1 has the best comprehensive electrochemical performance, especially the rate performance and long-term cycling stability with a capacity retention ratio of 82.6% after 3500 cycles, which indicates that different comonomers have obvious effects on the performance. Therefore, the full cell of SnS₂/GPE1/Na₃V₂(PO₄)₃ is evaluated and delivers good cycling stability of 500 cycles, holding a great prospect for the design and production of phosphorus-containing electrolytes for safer sodium-ion batteries.

An Overview on Anodes for Magnesium Batteries: Challenges towards a Promising Storage Solution for Renewables

Magnesium-based batteries represent one of the successfully emerging electrochemical energy storage chemistries, mainly due to the high theoretical volumetric capacity of metallic magnesium (i.e., 3833 mAh cm-3 vs. 2046 mAh cm-3 for lithium), its low reduction potential (-2.37 V vs. SHE), abundance in the Earth's crust (104 times higher than that of lithium) and dendrite-free behaviour when used as an anode during cycling. However, Mg deposition and dissolution processes in polar organic electrolytes lead to the formation of a passivation film bearing an insulating effect towards Mg2+ ions. Several strategies to overcome this drawback have been recently proposed, keeping as a main goal that of reducing the formation of such passivation layers and improving the magnesium-related kinetics. This manuscript offers a literature analysis on this topic, starting with a rapid overview on magnesium batteries as a feasible strategy for storing electricity coming from renewables, and then addressing the most relevant outcomes in the field of anodic materials (i.e., metallic magnesium, bismuth-, titanium- and tin-based electrodes, biphasic alloys, nanostructured metal oxides, boron clusters, graphene-based electrodes, etc.).