Effect of ionotropic gelation of COOH-functionalized polymeric binders in multivalent ion batteries

Abstract

Multivalent ion batteries (MIBs) have received much attention as alternatives to the current lithium-ion batteries (LIBs) because of their high energy density and the possibility of using raw materials with high natural abundance. However, the mechanochemical stability and key electrochemical performance of MIB electrodes are easily impaired during cycling by the large volume expansion of active materials and sluggish ion transport, raising the necessity of developing advanced binder designs. Herein, we report a systematic investigation of polysaccharide and polyacrylic acid binders with carboxylic acid functional groups for MIBs based on Mg2+, Ca2+, Zn2+, and Al3+ in comparison with their monovalent counterpart. These binders with carboxylic acid functional groups form a rigid passivation layer on the electrode surface via the so-called egg-box mechanism involving the multivalent cations, imposing resistance and shortening the cycle life of the MIB cells. The series of comparative analyses provide useful information on the effect and design of popular carboxylic acid-functionalized binders for incorporation in MIBs.