Dual-Layer Binder Electrode for Lithium Secondary Battery Adhesion
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Solution Overview
Problem
Lithium secondary batteries face a decrease in charge/discharge capacity and lifespan due to increased inner resistance and volumetric changes of electrode active materials during repeated charge/discharge cycles, leading to poor adhesion between the electrode and current collector, and between active materials.
Innovation Solution
The use of binders with different glass transition temperatures (Tg) in the electrode mix, where a binder with a lower Tg is applied near the current collector and a binder with a higher Tg is applied further away, enhancing adhesion between the current collector and active materials while maintaining adhesion between active materials, thus minimizing electron migration pathway loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single binder is used in the electrode mix, then the manufacturing process is simple, but adhesion between the current collector and active material deteriorates during repeated charge/discharge cycles due to volumetric changes
Solution Approach 1:
The electrode mix is segmented into two distinct layers: a first electrode mix layer adjacent to the current collector containing a first binder, and a second electrode mix layer away from the current collector containing a second binder. This segmentation allows each layer to be optimized for its specific function, with the first binder providing strong initial adhesion to the current collector and the second binder maintaining adhesion during volumetric expansion and contraction cycles.
Solution Approach 2:
Different binder properties are assigned to different locations within the electrode structure. The first binder near the current collector has specific properties optimized for strong substrate adhesion, while the second binder in the outer layer has properties optimized for maintaining integrity during volumetric changes. This local differentiation of material properties resolves the contradiction between manufacturing simplicity and adhesion reliability.
2Quantity of substance
If silicon-based active material with high theoretical capacity is used, then energy density is improved, but volumetric expansion by about 300% causes electrode mix to release from current collector
Solution Approach 1:
The electrode mix is divided into two layers with different binder compositions to handle the extreme volumetric expansion of silicon-based materials. The first layer provides anchoring to the current collector, while the second layer accommodates the expansion without losing adhesion, enabling the use of high-capacity silicon materials without sacrificing structural integrity.
Solution Approach 2:
The electrode employs a composite structure with two different binder materials in separate layers. This composite approach combines the advantages of each binder type: the first binder provides strong substrate bonding, while the second binder provides flexibility and adhesion retention during large volumetric changes, enabling the electrode to withstand silicon's 300% expansion.
3Productivity
If repeated charge/discharge cycles are performed, then battery capacity is increased, but inner resistance increases due to separation between electrode active materials and current collector
Solution Approach 1:
By segmenting the electrode mix into two layers with specialized binders, the structure prevents separation between active materials and current collector during cycling. The first binder ensures牢固 attachment to the current collector, while the second binder maintains cohesion during expansion/contraction, preventing the increased inner resistance that normally occurs with repeated charge/discharge cycles.
Solution Approach 2:
The dual-layer binder structure is prepared in advance to preemptively address the adhesion problems that occur during cycling. The first binder pre-establishes strong bonding to the current collector, and the second binder pre-configures the outer layer to accommodate volumetric changes, preventing separation and resistance increase before they can occur during subsequent charge/discharge cycles.
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 approach maintains high adhesion and cycle characteristics of the battery, preventing adhesion decrease and electron migration pathway loss despite volumetric changes, thereby enhancing the battery's capacity and lifespan.
Implementation Method 1
binders having different glass transition temperatures (Tg) near an interface of a current collector and in an electrode mix on the current collector
Implementation Method 2
high adhesion is exhibited between the current collector and an active material and between active materials
Data Source
AI summary
Disclosed is an electrode for secondary batteries including an electrode mix, which includes an electrode active material and a binder, coated on a current collector. More particularly, the electrode includes a first electrode mix layer including a first binder, a glass transition temperature (Tg) of which is lower than that of a second binder, and an electrode active material, and coated on the current collector; and a second electrode mix layer including the second binder, a glass transition temperature (Tg) of which is higher than that of the first binder, and an electrode active material, and coated on the first electrode mix layer.