Gel Polymer Electrolytes Containing Anion-Trapping Boron Moieties for Lithium-Ion Battery Applications

Abstract

Gel polymer electrolytes (GPEs) based on semi-interpenetrating polymer network (IPN) structure for lithium-ion batteries were prepared by mixing boron-containing crosslinker (BC) composed of ion-conducting ethylene oxide (EO) chains, crosslinkable methacrylate group, and anion-trapping boron moiety with poly(vinylidene fluoride) (PVDF) followed by ultraviolet light-induced curing process. Various physical and electrochemical properties of the GPEs were systematically investigated by varying the EO chain length and boron content. Dimensional stability at high temperature without thermal shrinkage, if any, was observed due to the presence of thermally stable PVDF in the GPEs. GPE having 80 wt% of BC and 20 wt% of PVDF exhibited an ionic conductivity of 4.2 mS cm at 30 C which is one order of magnitude larger than that of the liquid electrolyte system containing the commercial Celgard separator (0.4 mS cm) owing to the facile electrolyte uptake ability of EO chain and anion-trapping ability of boron moiety. As a result, lithium-ion battery cell prepared using the GPE with BC showed an excellent cycle performance at 1.0 C maintaining 87 % of capacity during 100 cycles.

Magnesium Borate Fiber Coating Separators with High Lithium‐Ion Transference Number for Lithium‐Ion Batteries

“…As shown in Figure c and 4d, the t Li+ of MBO@PP have increased from 0.24 to 0.57 compared with that of PP separator. It can be concluded that the boron‐oxygen units in MBO acting as Lewis acid sites interacts with Lewis base , which restricts the migration of and in turn promotes the migration of Li + , so the t Li+ of MBO@PP increased . Furthermore, the one dimensional fiber structure we introduced to form the coating layer enlarges the contact sites with the anions in the liquid and also could construct an one dimensional Li + conduction pathway.…”

“…It can be concluded that the boron-oxygen units in MBO acting as Lewis acid sites interacts with Lewis base PF À 6 , which restricts the migration of PF À 6 and in turn promotes the migration of Li + , so the t Li + of MBO@PP increased. [20,21,26] Furthermore, the one dimensional fiber structure we introduced to form the coating layer enlarges the contact sites with the anions in the liquid and also could construct an one dimensional Li + conduction pathway. The increase of migration number is beneficial to reduce concentration polarization, especially in the case of high current density, and improve cell performance.…”

“…[11] In addition, it has been reported that electron-deficient functional group such as boron atoms in the borate ester polymers can also adsorb anions to increase the t Li + . [20][21][22] Inspired by the above works combined with our previous work, we envisage the application of borate inorganic ceramics with both BÀ O electron-deficient group and high thermal shrinkage resistance of ceramic materials on the polyolefin separator. On one hand, borate-based ceramics can improve the thermal stability of the polyolefin separator same as the mechanism of Al 2 O 3 /SiO 2 ceramics coating layer to ensure its dimensional stability at elevated temperature.…”

Hybrid Polymer Electrolyte for Lithium-Oxygen Battery Application

“…As shown in Figure 4-2, for all electrolyte samples, the addition of ETPTA polymer to liquid electrolytes with different salt concentrations does not change the shape of the TFSI -Raman spectrum as they all exhibit two distinct Raman shifts for unbounded and bounded TFSIconfirming that ETPTA polymer does not have any ion-trapping ability [145] and acts merely as an inert polymer. Furthermore, the addition of 1 wt.% glass microfillers to the GPEs at 0.1 and 1 mol·kg -1 LiTFSI shows that the dissociation level of LiTFSI increases as the Raman shift of bounded TFSI -(shoulder ≥ 744 cm -1 ) was significantly reduced.…”

“…The appropriate Li + solvation with solvent molecules may increase the favorable accessibility of superoxides to Li + by increasing the salt concentration, which in turn mitigates the electrolyte decomposition [142][143][144]. Gel polymer electrolytes (GPE) consisting of liquid electrolyte and polymer has been successfully used in lithium-ion batteries due to their high ionic conductivity and mechanical stability [91,145,146]. Recently, GPE with different electrolytes and polymers have also been developed for Li-O2 battery applications [61,64,97,98,147].…”