synthesis-ionic-liquid-based-electrolytes-assembly-li-ion-batteries

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion ...

Boston University

A polystyrenylphosphonium polymer was synthesized and complexed with various carboxylic acid derivatives to form new solid-state polyelectrolyte-surfactant assemblies. The properties of these ionic materials were highly dependent on the nature of the anion and included a brittle material, a rubbery ball that bounces, or a sticky fiber. The values for the equilibrium modulus, storage modulus, and loss modulus were dependent on the composition of the carboxylic acid and the number of electrostatic interactions. Small-angle X-ray scattering studies on the supramolecular assemblies confirmed a bilayer structure for two of the assemblies.

From Brittle to Pliant Viscoelastic Materials with Solid State Linear Polyphosphonium - Carboxylate Assemblies.

The synthesis and characterization of a degradable version of poly(acrylic acid), poly(glyceric acid carbonate), are reported. Specifically, atactic and isotactic poly(benzyl glycidate carbonate)s are obtained via the ring-opening copolymerization of rac-/(R)-benzyl glycidate with CO2 using a bifunctional rac-/(S,S)-cobalt salen catalyst in high carbonate linkage selectivity (>99%) and polymer/cyclic carbonate selectivity (∼90%). Atactic poly(benzyl glycidate carbonate) is an amorphous material with a T(g) (glass transition temperature) of 44 °C, while its isotactic counterpart synthesized from enantiopure epoxide and catalyst is semicrystalline with a T(m) (melting temperature) = 87 °C. Hydrogenolysis of the resultant polymers affords the poly(glyceric acid carbonate). Poly(glyceric acid carbonate) exhibits an improved cell cytotoxicity profile compared to poly(acrylic acid). Poly(glyceric acid carbonate)s also degrade remarkably fast (t(1/2) ≈ 2 weeks) compared to poly(acrylic acid). Cross-linked hydrogels prepared from poly(glyceric acid carbonate) and poly(ethylene glycol) diaziridine show significant degradation in pH 8.4 aqueous buffer solution compared to similarly prepared hydrogels from poly(acrylic acid) and poly(ethylene glycol) diaziridine.

Synthesis and Characterization of Poly(glyceric Acid Carbonate): A Degradable Analogue of Poly(acrylic Acid).

Fabrication of lithium-ion batteries that operate from room temperature to elevated temperatures entails development and subsequent identification of electrolytes and electrodes. Room temperature ionic liquids (RTILs) can address the thermal stability issues, but their poor ionic conductivity at room temperature and compatibility with traditional graphite anodes limit their practical application. To address these challenges, we evaluated novel high energy density three-dimensional nano-silicon electrodes paired with 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide (Pip) ionic liquid/propylene carbonate (PC)/LiTFSI electrolytes. We observed that addition of PC had no detrimental effects on the thermal stability and flammability of the reported electrolytes, while largely improving the transport properties at lower temperatures. Detailed investigation of the electrochemical properties of silicon half-cells as a function of PC content, temperature, and current rates reveal that capacity increases with PC content and temperature and decreases with increased current rates. For example, addition of 20% PC led to a drastic improvement in capacity as observed for the Si electrodes at 25 °C, with stability over 100 charge/discharge cycles. At 100 °C, the capacity further increases by 3-4 times to 0.52 mA h cm(-2) (2230 mA h g(-1)) with minimal loss during cycling.

Ionic Liquid-Organic Carbonate Electrolyte Blends To Stabilize Silicon Electrodes for Extending Lithium Ion Battery Operability to 100 °C.

With the ongoing global effort to reduce greenhouse gas emission and dependence on oil, electrical energy storage (EES) devices such as Li-ion batteries and supercapacitors have become ubiquitous. Today, EES devices are entering the broader energy use arena and playing key roles in energy storage, transfer, and delivery within, for example, electric vehicles, large-scale grid storage, and sensors located in harsh environmental conditions, where performance at temperatures greater than 25 °C are required. The safety and high temperature durability are as critical or more so than other essential characteristics (e.g., capacity, energy and power density) for safe power output and long lifespan. Consequently, significant efforts are underway to design, fabricate, and evaluate EES devices along with characterization of device performance limitations such as thermal runaway and aging. Energy storage under extreme conditions is limited by the material properties of electrolytes, electrodes, and their synergetic interactions, and thus significant opportunities exist for chemical advancements and technological improvements. In this review, we present a comprehensive analysis of different applications associated with high temperature use (40-200 °C), recent advances in the development of reformulated or novel materials (including ionic liquids, solid polymer electrolytes, ceramics, and Si, LiFePO4, and LiMn2O4 electrodes) with high thermal stability, and their demonstrative use in EES devices. Finally, we present a critical overview of the limitations of current high temperature systems and evaluate the future outlook of high temperature batteries with well-controlled safety, high energy/power density, and operation over a wide temperature range.

Xinrong Lin

Department of Chemistry

Boston University

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

Xinrong Lin

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Chemistry

Boston University

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

Department of Chemistry