Multi-layer Negative Electrode with Graded Binder Density

The patent applies different binder contents to different layers of the negative electrode. The first negative electrode mixture layer in contact with the current collector contains a binder at 1-10 wt% to ensure strong adhesion, while the second negative electrode mixture layer contains binder at 0.1-5 wt% to maintain sufficient adhesion with minimal binder. This local differentiation resolves the contradiction by providing high adhesion where needed (at the current collector interface) while reducing binder content elsewhere to maintain low internal resistance and high electron conductivity.

The patent concentrates the binder content in the first negative electrode mixture layer that is in direct contact with the current collector, where adhesion is most critical. The second negative electrode mixture layer, which contributes more to capacity, contains minimal binder. This spatial distribution of binder content resolves the contradiction by ensuring adequate adhesion only where structurally necessary, thereby preserving maximum capacity in the active material layers.

The patent applies a first negative electrode mixture layer containing binder (1-10 wt%) to the current collector before applying the second layer. This preliminary layer creates a stable, adhesive foundation that prevents electrode separation during subsequent coating, drying, and rolling processes. By establishing strong adhesion in advance at the current collector interface, the structure can support high amounts of active material in the second layer without separation, thus achieving high capacity while maintaining stability.