Conductive-Coated Separator for Silicon Anode Network Stability
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Solution Overview
Problem
Existing lithium secondary batteries using silicon negative electrodes face issues with conductive network breakage due to overexpansion and overcontraction, leading to increased resistance and performance deterioration.
Innovation Solution
A conductive layer is formed on the surface of a separator to wrap the silicon active material, with a thickness greater than 50% of the D50 particle size, to maintain electron movement paths and prevent conductive network interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is used in a lithium secondary battery, then safety is improved by preventing direct contact between electrodes, but internal resistance increases due to electron blocking
Solution Approach 1:
The separator is designed with non-uniform conductivity distribution, having a first conductive layer with higher conductivity and a second conductive layer with lower conductivity. This local quality variation allows different regions of the separator to serve different functions: the first layer provides adequate electron blocking for safety while the second layer reduces overall resistance by providing selective conduction paths.
Solution Approach 2:
The separator is constructed as a composite structure combining two different conductive materials with distinct conductivity characteristics. The first conductive layer uses material with higher electron conductivity to maintain safety, while the second conductive layer uses material with lower conductivity to reduce internal resistance, creating a composite separator that balances both requirements.
2Reliability
If separator thickness is increased to improve safety, then electrode isolation is enhanced, but ion transport resistance increases
Solution Approach 1:
The separator employs a porous structure with controlled pore size and distribution that allows efficient ion transport while maintaining adequate thickness for electrode isolation. The porous architecture provides multiple parallel ion conduction pathways, reducing ion transport resistance even as thickness increases to improve safety.
Solution Approach 2:
The separator utilizes a three-dimensional porous network structure that separates electrodes in the thickness direction while providing extensive surface area and interconnected pores for ion transport. This dimensional approach allows the separator to be thick enough for safety without proportionally increasing ion transport resistance, as ions can take multiple pathways through the porous structure.
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
The conductive layer effectively prevents conductive network breakage, maintains electron flow, and enhances energy density by using high-capacity silicon active materials while minimizing thickness, thus improving battery performance and cycle characteristics.
Implementation Method 1
a first surface of the separator comes into contact with a first electrode and a second surface of the separator comes into contact with a second electrode, respectively. The conductive layer may facilitate electron transfer between the electrodes through the separator, thereby reducing internal resistance of the battery cell
Implementation Method 2
a separator is disposed between the first electrode and the second electrode to prevent direct contact between the electrodes
Data Source
AI summary
The present invention relates to an electrode assembly including a positive electrode having a positive electrode mixture layer formed on at least one surface of a positive electrode current collector, a negative electrode having a negative electrode mixture layer formed on at least one surface of a negative electrode current collector, and a separator interposed between the positive electrode and the negative electrode, wherein the negative electrode mixture layer includes a silicon active material, a conductive layer is formed on at least one surface of the separator, and the thickness of the conductive layer is greater than 50% of the D50 particle size of the silicon active material, and a battery cell including the same.