J. Electrochem. Sci. Technol., 2021, 12(2), 217-224 - 217 - Investigation of Lithium Transference Number in PMMA Composite Polymer Electrolytes Using Monte Carlo (MC) Simulation and Recurrence Relation Renwei Eric Koh*, Cha Chee Sun, Yee Ling Yap, Pei Ling Cheang, and Ah Heng You Faculty of Engineering and Technology, Multimedia University, 75450 Melaka, Malaysia ABSTRACT In this study, Monte Carlo (MC) simulation is conducted with recurrence relation to study the effect of SiO with different particle size and their roles in enhancing the ionic conductivity and lithium transference number of PMMA composite poly- mer electrolytes (CPEs). The MC simulated ionic conductivity is verified with the measurements from Electrochemical Impedance Spectroscopy (EIS). Then, the lithium transference number of CPEs is calculated using recurrence relation with the MC simulated current density and the reference transference number obtained. Incorporation of micron-size SiO (≤10 µm) fillers into the mixture improves the ionic conductivity from 8.60×10 S/cm to 2.35×10 S/cm. The improve- ment is also observed on the lithium transference number, where it increases from 0.088 to 0.3757. Furthermore, the addi- tion of nano-sized SiO (≤12 nm) fillers further increases the ionic conductivity up towards 3.79×10 S/cm and lithium transference number of 0.4105. The large effective surface area of SiO fillers is responsible for the improvement in ionic conductivity and the transference number in PMMA composite polymer electrolytes. Keywords : Solid Polymer Electrolytes, Monte Carlo Simulation, Transference Number, Recurrence Relation, Ionic Conductivity Received : 21 September 2020, Accepted : 3 November 2020 1. Introduction Solid Polymer Electrolytes (SPE’s) are electro- lytes in solid form which consist of dissolved inor- ganic salts as charge carriers. SPEs eliminated the need for a separator. As a result, it is safer than tradi- tional liquid and gel electrolytes. Besides, SPEs are extremely flexible and had better compatibility with most electrode materials. However, the application of SPEs on energy powered devices is hindered due to their high degree of crystallinity at room temperature. Due to the higher degree of crystallinity in tradi- tional polymer electrolytes, i.e. PEO based polymer electrolytes, the motion on Li + ions among the poly- mer chain is stalled, and this causes the film to gener- ate a significant amount of internal resistance that results in low ionic conductivity and lithium transfer- ence number. Agrawal et al. [1] reported an ionic conductivity of 1×10 -7 S/cm for PEO-LiClO 4 at room temperature in their study of solid polymer electro- lytes system. Also, Pozyczka et al. [2] reported a lith- ium transference number of 0.054 to 0.059 for PEO- LiTFSI SPEs with a molar ratio of 6:1 at 70 o . Ionic conductivity and lithium transference number reported in the above studies for PEO SPEs are insuf- ficient for practical application [3]. Moreover, ion transport in polymer electrolytes is a temperature-dependent process [4], ions received energy via thermal vibration to overcome the energy barrier so that they can have enough activation energy to hop to a nearby open vacant site. Thus, low activation energy and availability of open bond is essential for ionic transport in SPEs. Nevertheless, ionic conductivity and lithium transference numbers in SPEs can be boosted via the addition of ionic salts, plasticizers, and ceramic fillers [5-7]. Qian et al. [8] reported an improvement in ionic conductivity from 1.30×10 -7 S/cm for (PEO) 16 LiClO 4 Research Article *E-mail address: 1142701349@student.mmu.edu.my DOI: https://doi.org/10.33961/jecst.2020.01459 This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.