Positive Electrode Binder Gradient for Folding Strength

The patent applies local quality by creating non-uniform binder distribution within the positive electrode composition layer. The binder concentration is specifically increased at the surface side (a/b ≥ 2) compared to the current collector side, providing localized reinforcement where folding stress concentrates during electrode assembly and operation. This gradient structure allows the electrode to maintain high power output while resisting breakage at critical stress points.

The patent resolves this contradiction by implementing local quality through spatially varying binder concentration. While the overall electrode density is maintained at high levels (≥3.95 g/cm3) for energy density, the binder is specifically concentrated at the surface region (a/b ≥ 2) to provide localized mechanical reinforcement. This allows the bulk material to achieve high density for energy storage while the surface layer provides the necessary folding strength.

The patent applies inversion by reversing the conventional binder distribution approach. Instead of placing maximum binder quantity at the current collector side (as in prior art), the patent concentrates the binder at the surface side (a/b ≥ 2). This inverted distribution maintains folding strength while preserving discharge capacity, as the surface-located binder provides mechanical reinforcement without creating the same detrimental effects on ion transport that collector-side binder placement causes.