Synthesis of Aminopolyolefins with Tunable Hydrophilicity and Chain Flexibility for Application as Binders in Aqueous Rechargeable Batteries

Rechargeable Zn-ion batteries (ZIBs) are an attractive alternative to Li-ion batteries (LIBs) for delivering sustainable energy storage systems for stationary applications due to their high energy density, use of earth-abundant materials, lower cost, and improved safety. Although ZIBs have theoretically high energy densities, maintaining the long-term performance of high-mass-load ZIBs remains a challenge. While polymeric binders are known to maintain mechanical integrity during cycling and prolong battery life, diverse binder materials have not been widely explored for the development of new ZIB technologies. As binders, recently disclosed aminopolyolefins (APOs) have the potential to offer good charge and mass transport properties to improve the electrochemical performance of the cell. Here, different types of APO-based binders with variable mechanical properties and hydrophilicities have been synthesized. The chain flexibility and hydrophilicity of the APO binders were found to have a profound influence on the ZIB cycling performance. APOs with self-healing and hydrophilic properties were preferred for assembling aqueous ZIBs that are not limited to low active material loading but show that a high active material loading is possible. The tunability of APOs was exploited to assemble near-neutral aqueous Zn/MnO2 batteries, with up to 25 mg cm^-2 of MnO2, to deliver modified performance and cyclability of up to approximate to 100 mAh g^-1MnO2 at the 100th cycle. These results show that novel APOs are a promising platform for the development of materials with tunable hydrophilicity and chain flexibility to push toward the enhanced long-term performance of ZIBs.