Binder, preparation method therefor, secondary battery, battery module, battery pack and power consuming device

A method for preparing a binder, characterized in that the method comprises:

• preparation of an intermediate polymer:
• polymerizing a monomer represented by formula III to form the intermediate polymer containing at least cyano, an aldehyde group or an ester group,
• wherein in the formula III, R1, R2, and R3 are each independently selected from hydrogen and substituted or unsubstituted C1-3 alkyl, and R4 is selected from hydrogen, cyano, an aldehyde group, or an ester group;
• and
• modification reaction:
• subjecting the intermediate polymer and an aqueous solution of an alkaline substance to a modification reaction, such that at least part of the cyano, aldehyde groups or ester groups in the intermediate polymer are converted into COOM groups, wherein M is selected from H, Li, Na, K or NH4.