Application of hyperdispersants for enhanced adhesion of ceramic coatings on plasma treated separators for lithium-ion batteries

• Main Author: Theodora Lynn
• Other Authors: Alex Yan Qingyu
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/165828
• Institution: Nanyang Technological University

Lithium-ion batteries (LIBs) dominate the current field of energy storage devices and have broad applications in various industries. With ever-increasing demands for high energy-density applications in emergent technologies, requirements for enhanced LIB safety also escalates. Separator is a component in LIB that is key in ensuring safety as it prevents the occurrence of internal short circuits. Polyolefin membranes, which are commonly used as LIB separators, have several limitations including poor thermal stability and mechanical strength. These shortcomings pose safety risks, especially in high-power applications of LIBs. A practical approach to enhance the properties of polyolefin-based separators is by incorporating ceramic coatings. Apart from ceramic particles, binders are also vital components within ceramic coatings. Binders play an important role in providing adhesion and cohesion of the ceramic coatings, thus mitigating the hazardous consequences resulting from delamination of coatings from polyolefin membranes. To date, PVDF is the binder mainly used for ceramic coated separators (CCS). However, the application of PVDF presents several disadvantages such as unoptimized adhesion strength due to its non-reactive structure, adverse environmental and health effects, and expensive processing. This creates the need for aqueous binders. Herein we introduce the application of a hyperdispersant containing multiple carboxylic acid anchor groups tied onto polyethylene glycol chains (COOH/PEG-HD) as a binder used in alumina coatings on plasma-treated polyolefin membranes. The high density of reactive carboxylic acid functional groups in this binder enables the attainment of high adhesion strength even when only a low concentration of COOH/PEG-HD is added. Additionally, the usage of COOH/PEG-HD as binder results in good capacity retention and cyclability of the assembled LIB, which could be attributed to the strong adhesion that prevents delamination of the alumina coating.