POLYIMIDE-BASED BINDER FOR POWER STORAGE DEVICE, ELECTRODE MIXTURE PASTE, NEGATIVE ELECTRODE ACTIVE MATERIAL LAYER, NEGATIVE ELECTRODE SHEET FOR POWER STORAGE DEVICE, AND POWER STORAGE DEVICE

A polyimide-based binder for power storage device having a repeated breaking energy retention ratio of 70% or more. The use of the binder enables improvement of a power storage device having a high capacity.