China
Africa
Explore chapters and articles related to this topic
Nanocomposite Polymer Electrolytes for Electric Double Layer Capacitors (EDLCs) Application
Published in Hieng Kiat Jun, Nanomaterials in Energy Devices, 2017
The extensive delocalized electrons in TFSI− anion can promote the ion dissociation and thereby increase the ionic conductivity by weakening the interactions between alkali metals and nitrogen with the polyether oxygen (Ramesh and Lu 2008). The attempt of using LiTFSI in this work is because of its non-corrosive behavior towards electrodes, wide electrochemical stability, excellent thermal stability and superior thermal properties. Apart from that, this salt can dissociate very well even in low dielectric solvents. It is a new designed metal salt to replace the poor conducting lithium triflate (LiTf), the hazardous lithium perchlorate (LiClO4), the thermally unstable LiBF4 and lithium hexafluorophosphate (LiPF6), and the toxic lithium hexafluoroarsenate (LiAsF6) (Kang 2004).
Metal-Sulfur Batteries Based on Nanostructured Covalent Organic Frameworks
Published in Tuan Anh Nguyen, Ram K. Gupta, Covalent Organic Frameworks, 2023
Electrolyte directly affects the cycling life and safety of the battery. In liquid electrolytes, the serious shuttle effect results in the rapid attenuation of the battery capacity. The most common solvent is DOL and DME. DOL is conducive to the formation of stable SEI on lithium metal anode. DME has good solubility in polysulfides, which is conducive to the conversion reaction of polysulfides. Barchasz et al. [31] explored the effect of the content of oxygen in the solvent on the battery capacity and showed that the initial capacity of the battery increased with the enhancement of oxygen content. For example, the battery using polyethylene glycol dimethyl ether (PEGDME) with high oxygen content exhibits the best electrochemical performance. The common lithium salt for LSB is LiTFSI. LiTFSI has the advantages of high electrochemical stability and ionic conductivity. The viscosity of the electrolyte can be adjusted by changing the type and concentration of lithium salt. For example, adding lithium salt LiFSI to the electrolyte can reduce the viscosity of the electrolyte and improve the ionic conductivity at the same time [32]. The common additive for LSB is LiNO3 , which can generate stable SEI and stabilize the lithium metal anode [33]. In addition to a liquid electrolyte, a solid electrolyte is considered to be a more promising electrolyte. Due to the high safety and almost no polysulfide dissolution, the solid electrolyte has attracted many interests. However, its low ionic conductivity and poor compatibility with the electrode surface limit its commercial application.
Polymer-Ionic Liquid Gel Electrolytes for Lithium-Ion Batteries
Published in Prasanth Raghavan, Fatima M. J. Jabeen, Polymer Electrolytes for Energy Storage Devices, 2021
Lithium bis (trifluoromethane sulfonyl)imide (LiTFSI) is a hydrophilic salt with the chemical formula LiC2F6NO4S2. It is a widely accepted Li+-ion source in commercially available LIBs. After the introduction of LiTFSI, lithium hexafluorophosphate became less attractive because of its poorer performance when compared with LiTFSI. Free-standing PILGEs, consisting of a PIL, poly[diallyldimethylammonium] bis-trifluoromethane sulfonimide] (PDAD-MATFSI), an IL, 1-ethyl-3-methylimidazolium bis-trifluoromethane sulfonimide and a Li salt for LIB application, was developed by Safa et al. [17]. In a typical procedure, the pyrrolidinium-based PIL, PDAD-MATFSI, was synthesized by a simple anion-exchange reaction between the chlorinated polymer and LiTFSI. The as-synthesized PIL was insoluble in water but readily soluble in acetone. Furthermore, the IL, 1-ethyl-3-methyl imidazolium bis (trifluoromethane sulfonyl)imide (EMIM-TFSI), was synthesized by reacting [EMIM][Cl] and LiTFSI in de-ionized water. The as-synthesized IL was colorless, odorless, and a fluid, which was dried at 60°C in a vacuum oven for two hours and immediately stored in an oxygen-free and humidity-free glove-box until later use. Furthermore, the GPE was synthesized in a procedure consisting of mixing an already prepared 1 M LiTFSI in [EMIM][TFSI] with 20 wt.% of PIL (final composition 80:20 electrolyte: PIL by weight). This mixture was dissolved in acetone and stirred (or sonicated) until completely dissolved. The final solution was drop-cast on a 0.0127 m circular polydimethylsiloxane (PDMS) template and enough time was given to evaporate the acetone from it, before it was vacuum dried at 90°C for 72 hours. The PILGE film developed in this way was transparent and free-standing. The PILGE film was thermally stable and contained IL and salt contents of up to 80 wt.%. This high concentration was found to enhance the ionic conductivity of the electrolyte films. A high ionic conductivity of 3.35X10−3 S cm−1 was obtained for the electrolyte films. Combining PIL with the salt component has allowed the LIB to exhibit a wide electrochemical stability window of −0.1 to 4.9 V. An increased Li+-ion-transference number was also achieved. In addition, the PILGEs were found to suppress the formation of Li dendrites when compared with the pure IL component without the polymer.
Promoting ion and heat transfer of solid polymer electrolytes by tuning polymer chain length and salt concentration
Published in International Journal of Green Energy, 2023
Jiaqi Wang, Linhao Fan, Weizhuo Li, Ting Guo, Fang Wang, Qing Du, Kui Jiao
Unlike cathodes and anodes, SPEs are composed of a lithium salt and polymer matrix, in which the polymer matrix forms the framework of the composite materials (Meng et al. 2019). Among all the polymeric matrices considered for this purpose, polyethylene oxide (PEO) is considered to have good electrochemical and mechanical stability, a high dielectric constant, good compatibility with lithium salts, easy preparation methods, and good safety properties, making it a promising candidate polymer for a high-energy SPE matrix (Banitaba et al. 2020). The properties of PEO-based structures are largely dependent on the length of the PEO chain (Devaux et al. 2012). Short-chain PEO can be more flexible, enabling larger ionic diffusion coefficients, but has lower mechanical stability. To improve the stability of the framework, some modifications have been attempted, including the generation of block copolymers (Panday et al. 2009), comb-like (Liang, Wang, and Chen 2008), and cross-linked (Snyder, Carter, and Wetzel 2007) polymer structures. Another method is to add active fillers to improve the conductivity (Zheng et al. 2020). In the case of sufficiently long-chain PEO, the diffusion coefficient and diffusion mechanism are independent of the chain length and the nature of the polymer end groups (Timachova, Watanabe, and Balsara 2015). Among the lithium salts tested, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) remains the main candidate owing to its excellent thermal, chemical, and electrochemical stability (Devaux et al. 2012). The crystallization of lithium salts in SPEs limits the heat conduction and electrical conductivity in SPEs. Therefore, the PEO chain length and ion concentration in SPEs are very important for their ion transport and heat conduction.