Optimization of separator coating using crosslinked polyacrylic acid for lithium-Ion batteries

Abstract

Lithium-ion batteries (LIBs) are essential for energy storage devices and find wide applications due to their numerous advantages. The separator is a critical element in LIBS for maintaining safety by prevent the occurrence of short circuits. The common LIBs are using polyolefin membranes. However, using polyolefin membranes will some shortcomings such as the mechanical strength and resistance to high temperatures. Ceramic coatings are applied to improve the properties of polyolefin- based separators.

Thickener also plays a crucial role in aqueous binder formulation, improving viscosity and rheological properties. Carboxymethyl cellulose (CMC) is commonly used thickener as it can efficiently control the viscosity and able to improve the adhesion between ceramic particles and separator. In this study we used crosslinked polyacrylic acid (PAA) as a thickening agent, creating a three-dimensional network structure that could improve on the viscosity. Therefore, this report aims to study the effect of crosslinked polyacrylic acid (PAA) as a thickening agent and compare with CMC in lithium-ion battery separator coatings. This report will evaluate the total solid % of thickener and performance of the samples that meets the golden viscosity of 300- 400cP. It is observed that 0.1 TS% crosslinked PAA offer better adhesion between the coating and the separator surface. Also, better electrolyte uptake compared to 0.4 TS% CMC. Both CMC and crosslinked PAA samples demonstrate significant improved wettability compared to the bare treated separator. The coulombic efficiency is also consistent and have good specific capacity, which efficiently deliver and store charge without significant losses. Although the additional coating can affect the porosity and electrical properties of the separator. The porosity is comparable as it does not adversely affect the permeability. The difference in ionic conductivity is also considered small which will not significantly impact the overall conductivity of the separator.