SYNTHESIS AND CHARACTERIZATION OF POLYMER ELECTROLYTE MEMBRANES DERIVED FROM MODIFIED CELLULOSE MATERIAL FOR LITHIUM ION BATTERY APPLICATION

• Main Author: SUDIARTI , TETY
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/24509
• Institution: Institut Teknologi Bandung

Lithium ion batteries have great potential as a candidate of large-scale electrical storage capacity because it has many advantages such as energy density and high working potential, fast charging/discharging, long life, and no memory effect. The main component of the battery consists of three parts, namely the anode part, the cathode part, and the electrolyte. As the electrolyte in the battery cell, the liquid electrolyte has a weakness, which is susceptible to leakage and more difficult in packaging, while a solid electrolyte is considered safer, easier to use, and can be made with smaller dimensions such as thin film or membrane. However, the use of solid electrolytes in the form of electrolytic polymers in lithium ion batteries needs to pay attention to environmental aspects, especially when it is used in large quantities. A polymer commonly used as a matrix in polymer electrolytes such as PEO (polyethylene oxide), is a hard-degraded polymer, which can lead to serious environmental problems such as soil and water pollution, bioaccumulation, difficult recycling and greenhouse effects. <br /> <br /> <br /> <br /> The purpose of this study was to develop a new electrolyte polymer from an environmentally friendly polymer matrix, i.e. modified cellulose-based polymers such as a cellulose acetate and a cellulose succinate. In this study, the electrolyte polymer is prepared by blending cellulose acetate with cellulose succinate and by blending cellulose acetate with polyvinyl alcohol (PVA), which is expected to produce membranes with sufficient ion conductivity to be applied as a solid electrolyte for lithium ion battery cells. The addition of cellulose succinate into cellulose acetate membrane is intended to open and enlarge membrane pores, to facilitate the transport of lithium ions to move more rapidly, so that it is expected to increase the ion conductivity of membranes. The addition of PVA into the cellulose acetate membrane because PVA is the most polymer produced, water-soluble, semi-crystalline, non-toxic, transparent, biocompatible polymer, has good chemical resistance, and is easily formed into film. This blending is thought to have a good ionic conductivity, since there is a complex-decomplexation process between the polymers used, thus facilitating the transport of ions in the polymer. <br /> <br /> <br /> <br /> The cellulose succinate was synthesized by MAOS method (Microwave Assisted Organic Synthesis) of cellulose and succinic acid anhydride that in ionic liquid (BMIM)Cl (1-butyl-3-methyl imidazolium chloride) with a microwave irradiation. The resulting cellulose succinate was then characterized by functional group analysis with using FTIR spectrophotometry and by their substitution degree analysis. Based on FTIR spectra of the synthesized cellulose succinate shows the appearance of a new peak at the wave number 1722.43-1726,29 cm-1 which is the absorption band for C=O ester (monoester) with the degree of substitution in the range 0.25 - 2.10. The dissolution conditions and reaction conditions influence the substitution degree of the produced cellulose succinate. The optimum conditions of cellulose succinate synthesis were as follows: the concentration of cellulose dissolution in [BMIM]Cl of 8.6% (w/w), the mole ratio of cellulose/succinic anhydride used was 1/10; microwave irradiation power was 100 Watt, temperature and time of reaction of 170 ºC and 30 minutes, respectively. <br /> <br /> <br /> <br /> In this study, it was prepared three types of electrolytic polymer membranes, namely cellulose acetate-lithium perchlorate (CA/Li+), cellulose acetate-lithium perchlorate-cellulose succinate (CA/Li+/CS), and cellulose acetate-lithium perchlorate-polyvinyl alcohol (CA/Li+/PVA) membranes. The cellulose succinate and polyvinyl alcohol in this study were used as additives to improve membrane characteristics. The preparation of electrolytic polymer membranes was done by solvent casting method, by means of controlled solvent evaporation. All the resulting membranes were characterized by functional group analysis (FTIR), ionic conductivity (EIS), mechanical properties (Tensile Tester), thermal properties (TGA), morphological analysis (SEM) and crystallinity analysis (XRD). <br /> <br /> <br /> <br /> Based on the results obtained show that the addition of lithium perchlorate, cellulose succinate, and polyvinyl alcohol on the cellulose acetate membrane affect the resulting membrane characteristics. The ionic conductivity of cellulose acetate membrane increases with the increase in the amount of lithium perchlorate added to the membrane, but the mechanical properties and thermal stability of the membrane decreases as well as their morphology is changed to become more porous and irregular. While the addition of cellulose succinate and polyvinyl alcohol into the CA/Li+ membrane, the ionic conduction and thermal stability of the membrane tends to increase, but the mechanical properties of the membrane tend to decrease, and their morphology tends to change into more porous and irregular. <br /> <br /> <br /> FTIR spectra analysis of the membrane shows the presence of a coordination complex between polymer and lithium perchlorate. The optimum membrane characteristics of CA/Li+ was obtained on lithium perchlorate content of 10% (w/w) i.e. ionic conductivity of 1.03 x 10-5 S/cm, tensile strength of 43.29 ± 3.523 MPa, elongation at break of 4.52 ± 1.37 %, and thermal resistance until at temperature of 265 C. In the addition of cellulose succinate, the optimum membrane characteristic of CA/Li+ was found on cellulose succinate content of 3% (w/w), i.e. ionic conductivity of 1.35 10-5 S/cm, tensile strength 28.03 ± 5.925 MPa, elongation at break of 2.85 ± 0.23%, and thermal resistant membrane up to temperature of 288 C. In addition of PVA, the optimal properties of CA/Li+ membrane was obtained on polyvinyl alcohol content of 5% (w/w), i.e. this membrane has the ionic conductivity of 1.39 10-5 S/cm, tensile strength of 29.51± 0.883 MPa, elongation at break of 6.01 ± 2.20 %, thermal resistant membrane up to temperature of of 275 C. XRD analysis supports the occurrence of a coordination complex between the polymer matrix and lithium perchlorate, and the membrane tendency to become more amorphous. Based on the results obtained above, the three membrane types are potential to be used as electrolytic polymer membranes for the application of lithium ion batteries. The best characteristic membrane based on the ionic conductivity is the SA/Li+/PVA membrane. <br /> <br /> <br />