Segmented Silicon Anode Electrode for Battery Cycle Life
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in increasing capacity and maintaining cycle and load characteristics due to the high expansion and contraction of anode active materials like silicon or tin, leading to structural destruction and limited reaction areas.
Innovation Solution
A secondary battery electrode with an active material layer formed by stacking sub-layers and having pores along the boundaries, which are filled with electrolyte or reduction products, allowing deeper ion penetration and reducing stress on the interface between the active material and current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon or tin is used as the anode active material to increase battery capacity, then the battery capacity increases, but the anode active material layer expands and contracts significantly during charging and discharging, leading to structural destruction and separation from the current collector
Solution Approach 1:
The anode active material layer is divided into multiple sub-layers (first sub-layer, second sub-layer, third sub-layer) with different compositions and functions. The first sub-layer contains silicon or tin for high capacity, the second sub-layer contains binder material to provide mechanical strength, and the third sub-layer contains conductive material to maintain electron conductivity. This segmentation allows each sub-layer to perform its specific function, preventing the structural destruction that would occur if the entire layer expanded and contracted uniformly.
Solution Approach 2:
The anode active material layer is constructed as a composite structure combining different materials in specific sub-layers. The first sub-layer uses silicon or tin (high capacity materials), the second sub-layer uses binder materials (for mechanical stability), and the third sub-layer uses conductive materials (for electrical conductivity). This composite structure resolves the contradiction by integrating materials with complementary properties, allowing the layer to both expand/contract for capacity and maintain structural integrity for reliability.
2Reliability
If the anode active material layer is formed monolithically to suppress fine-dividing of the active material, then the initial discharge capacity and charge/discharge cycle characteristic are improved, but repetition of charging/discharging applies stress to the interface, causing separation of the active material layer from the current collector
Solution Approach 1:
The anode active material layer is segmented into multiple sub-layers, with the second sub-layer specifically designed as a binder material layer that adheres to the current collector. This segmentation creates a dedicated adhesion interface that is more robust than a monolithic structure, as the binder material is specifically selected and positioned to provide strong bonding to the current collector while allowing the other sub-layers to expand and contract.
Solution Approach 2:
Different sub-layers are assigned different local qualities and functions: the first sub-layer is optimized for lithium alloying capacity, the second sub-layer is optimized for adhesion to the current collector, and the third sub-layer is optimized for electron conductivity. This local quality differentiation allows the interface with the current collector to have superior adhesion properties without compromising the overall capacity and conductivity of the active material layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the load and cycle characteristics by utilizing the entire active material layer for reactions, preventing separation and structural destruction, and maintaining a stable electrode shape.
Implementation Method 1
pores of which pore diameter along the thickness direction of the active material layer is 3 to 300 nm are formed along the boundary between the active material sub-layers, and at least a part of the pores is filled with an electrolyte and/or a product arising from reduction of the electrolyte
Implementation Method 2
the degree of the expansion and contraction of the anode active material layer accompanying charging and discharging is high, which leads to a problem of the lowering of the cycle characteristic due to the turning of the active material into fine particles or the separation of the active material from the anode current collector
Data Source
AI summary
A secondary battery electrode includes an active material layer configured to be provided on a current collector and be obtained by stacking a plurality of active material sub-layers composed of an active material. Pores of which pore diameter along a thickness direction of the active material layer is 3 to 300 nm are formed along a boundary between the active material sub-layers, and at least a part of the pores is filled with an electrolyte and/or a product arising from reduction of the electrolyte upon assembling of a secondary battery.