Cross-linked Composite Gel Polymer Electrolyte using Mesoporous Methacrylate-Functionalized SiO2 Nanoparticles for Lithium-Ion Polymer Batteries

Abstract

Liquid electrolytes composed of lithium salt in a mixture of organic solvents have been widely used for lithium-ion batteries. However, the high flammability of the organic solvents can lead to thermal runaway and explosions if the system is accidentally subjected to a short circuit or experiences local overheating. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures.

Figure 1

Schematic illustrations for (a) synthesis of mesoporous MA-SiO₂ particles, and (b) different lithium ion transport behavior when employing non-porous MA-SiO₂ particles and mesoporous MA-SiO₂ particles in the cross-linked composite gel polymer electrolyte.

Figure 2. Schematic illustrations of the synthesis of the cross-linked composite gel polymer electrolyte using the fibrous PAN membrane, mesoporous MA-SiO₂ nanoparticles and gel electrolyte precursor containing TEGDA.

Figure 3

FE-SEM images of (a) non-porous MA-SiO₂ nanoparticles and (b) mesoporous MA-SiO₂ nanoparticles. TEM images of (c) non-porous MA-SiO₂ nanoparticles and (d) mesoporous MA-SiO₂ nanoparticles.

Figure 4. Nitrogen adsorption-desorption isotherms for non-porous MA-SiO₂ and mesoporous MA-SiO₂ nanoparticles.

Figure 5

FE-SEM images of electrospun PAN membrane (a,b), composite PAN membrane with non-porous MA-SiO₂ nanoparticles (c,d) and composite PAN membrane with mesoporous MA-SiO₂ nanoparticles (e,f) at two different magnifications.

Figure 6

(a) Charge and discharge curves of lithium-ion polymer cell assembled with the cross-linked composite gel polymer electrolyte using mesoporous MA-SiO₂ nanoparticles and (b) discharge capacities of lithium-ion polymer cells assembled with different electrolytes at 25 °C (0.5 C CC & CV charge, 0.5 C CC discharge, cut-off voltage: 3.0–4.5 V). (c) AC impedance spectra of lithium-ion polymer cells assembled with different electrolytes, which were measured after 300 cycles.

Figure 7

(a) Discharge curves of lithium-ion polymer cell assembled with cross-linked composite gel polymer electrolyte employing mesoporous MA-SiO₂ particles and (b) discharge capacities of lithium-ion polymer cells assembled with different electrolytes as a function of C rate.

Figure 8

(a) Discharge capacities of lithium-ion polymer cells assembled with different electrolytes at 55 °C (0.5 C CC & CV charge, 0.5 C CC discharge, cut-off voltage: 3.0–4.5 V). (b) HF content in the different electrolytes after being stored at 55 °C for 3 days.