Three-Layer Silicon Negative Electrode for Conductivity-Capacity Balance

The patent applies local quality by creating a multilayer structure where different layers have different conductive material compositions. The first and third layers (adjacent to current collector and separator) have higher conductive material content to ensure electron transport, while the second layer (with silicon particles) has lower conductive material content to maximize lithium ion absorption capacity. This localized differentiation resolves the contradiction between capacity and charging rate.

The patent uses composite materials by combining multiple active material layers with different compositions. The negative electrode active material layer comprises a composite of carbon-containing particles (first active material layer), silicon-containing particles (second active material layer), and conductive materials distributed across all layers. This composite structure enables both high capacity from silicon and fast charging from conductive material networks.

The patent implements local quality by varying the conductive material distribution across different layers. The first and third active material layers contain conductive material at 0.1-5 wt% to maintain electrical conductivity for electron transport. The second active material layer (silicon-containing) contains conductive material at 0.01-1 wt%, minimizing non-active material while ensuring sufficient conductivity for lithium ion absorption. This localized optimization resolves the contradiction between conductivity and energy density.

The patent applies parameter changes by adjusting the concentration of conductive material in each layer based on functional requirements. The conductive material content is optimized differently in each layer: higher in outer layers for electron transport, lower in the silicon layer for maximum capacity. This parameter optimization enables both adequate conductivity and high energy density.

The patent applies the nested doll principle by placing silicon-containing particles (second active material layer) between two carbon-containing particle layers (first and third active material layers). The outer carbon layers act as protective shells that constrain silicon volume expansion during lithium ion absorption, while the conductive material distributed across all layers ensures electrical conductivity stability. This nested structure resolves the contradiction between capacity and reliability.

The patent implements beforehand cushioning by positioning carbon-containing particle layers adjacent to the silicon-containing layer before lithium ion absorption occurs. These outer layers serve as cushioning structures that accommodate silicon volume expansion during charging, preventing structural degradation and maintaining electrical conductivity stability over cycles. This preventive design resolves the reliability issue.