DOI: 10.22146/ajche.77318 ASEAN Journal of Chemical Engineering 2023, Vol. 23, No. 2, 1 – 11 The Deep Eutectic Solvent in Used Batteries as an Electrolyte Additive for Potential Chitosan Solid Elctrolyte Membrane Kindriari Nurma Wahyusi 1 Ika Nawang Puspitawati 2* Abdul Rachman Wirayudha 3 Chemical Engineering Department, Faculty of Engineering, Universitas Pembangunan Nasional Veteran Jawa Timur,Gunung Anyar, Surabaya, Indonesia * e-mail: ikanawangpuspita@gmail.com Abstract. The electrolyte or ion conductor acts as a bridge to transfer the ions the electrodes generate. In general, electrolytes are in the form of liquids. However, liquid electrolytes have drawbacks, including needing to be more practical and leaking quickly. Therefore, people switch to solid matrix electrolytes as battery electrolytes. An ideal solid electrolyte membrane must have chemical stability, thermal stability, high ionic conductivity, high flexibility, low cost, and abundant material availability. Lithium extraction from used batteries using Deep Eutectic Solvent (DES) was found to be an intelligent solvent. Mixing the method with lithium salt on a chitosan membrane can increase conductivity. This study aims to determine the lowest resistance value and highest conductivity of solid polymer electrolytes using Li2CO3 from used batteries. After separating the Lithium-Cobalt component from the used battery, it was extracted with deep DES solvent and precipitated using Na2CO3 to produce the Li2CO3 compound. Polymer electrolyte was synthesized by mixing polyvinyl alcohol and adding 0.2 grams, 0.4 grams, 0.6 grams, 0.8 grams, and 1 gram of chitosan. Li2CO3 variables are 0.2 grams, 0.4 grams, 0.6 grams, 0.8 grams, and 1 gram. The results showed that the higher content of chitosan and Li2CO3 led to an increase in ionic conductivity. These results concluded that the best solid electrolyte membrane was obtained with a variation ratio of 0.2 grams of chitosan with the addition of 1 gram of Li2CO3. Keywords: Chitosan, Conductivity, Deep Eutectic Solvent, Lithium-Ion, Solid Electrolyte Membrane INTRODUCTION The demand for batteries in electronic goods such as notebooks, cellphones, and electric vehicles has become so real and ubiquitous in recent years. Batteries are one of the most effective and reliable energy storage sources (Dehghani-Sanij et al., 2019). Interestingly, one of the improvements the commercial batteries that are widely used and famous is lithium-ion batteries (LIBs). LIBs are quite adequate among other energy storage systems in terms of durability and power or energy densities (Diouf et al.,, 2015; Li et al., 2018). Batteries consist of two essential components electrolytes as inactive and electrodes as active materials (Kasnatscheew et al., 2018). Electrolytes or Submitted 26 August 2022 Revised 11 April 2023 Accepted 07 May 2023