Gradient Lithiated Binder Layer for Silicon Anode Adhesion

The binder layer is designed with a gradient lithiation degree distribution, where different regions of the binder layer have different lithiation degrees. The region close to the current collector has a lower lithiation degree for strong binding, while regions farther away have progressively higher lithiation degrees for improved lithium conductivity. This spatial variation in composition resolves the contradiction between binding capability and lithium-conducting capability.

The lithiation degree of the binder is changed as a continuous parameter across the binder layer thickness. By controlling the lithiation degree to increase from the current collector interface toward the electrode interior, the binder simultaneously achieves strong adhesion (through lower lithiation degree regions) and high lithium conductivity (through higher lithiation degree regions), resolving the performance trade-off.

Different regions of the binder layer are assigned different lithiation degrees to fulfill different functions. The region adjacent to the current collector maintains a lower lithiation degree to ensure strong binding capability and prevent detachment, while regions farther from the current collector have higher lithiation degrees to provide excellent lithium-conducting capability. This local differentiation resolves the contradiction between binding strength and lithium conductivity.

The solution transitions from a uniform binder composition to a spatially varying composition along the thickness direction of the binder layer. By introducing a gradient in lithiation degree across the binder layer thickness, the system simultaneously achieves strong binding at the current collector interface and high lithium conductivity in the bulk, resolving the performance contradiction through dimensional variation.

The gradient lithiated binder layer is designed in advance to accommodate and buffer the volume expansion of silicon particles during lithiation. The binder's gradient structure provides mechanical cushioning and structural support before silicon particle rupture can occur, maintaining electrode integrity and preventing detachment while allowing high-capacity silicon materials to be used.

The negative electrode is designed as a composite structure combining silicon particles with a gradient lithiated binder matrix. This composite architecture leverages the high capacity of silicon while the gradient binder provides structural stability and mechanical support, preventing particle rupture and electrode detachment, thus enabling high energy density with maintained structure stability.