Multi-Layer Polymer Electrolyte for All-Solid Battery Interfacial Resistance
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Solution Overview
Problem
All-solid batteries with solid polymer electrolytes face challenges in achieving sufficient output and capacity due to low ionic conductivity and high interfacial resistance between lithium and the polymer electrolyte, which existing techniques have not adequately addressed.
Innovation Solution
A polymer electrolyte with a multi-layer structure is introduced, comprising a first polymer electrolyte layer with an EO:Li molar ratio of 1:1 to 7:1 and a second polymer electrolyte layer with an EO:Li molar ratio of 8:1 to 30:1, where the first layer is thin (1-5 µm) and the second layer is thicker (5-50 µm), and can be crosslinked to form a semi-IPN structure, reducing interfacial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid polymer electrolyte is used in all-solid batteries, then safety is improved by eliminating flammable organic solvents, but ionic conductivity is insufficient and interfacial resistance is high
Solution Approach 1:
The solid polymer electrolyte is divided into multiple layers with different EO:Li molar ratios. The first layer (near lithium electrode) has EO:Li of 1:1 to 3:1 for low interfacial resistance, while the second layer (near positive electrode) has EO:Li of 4:1 to 30:1 for high ionic conductivity. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between low interfacial resistance and high ionic conductivity.
Solution Approach 2:
Different regions of the electrolyte are assigned different compositions tailored to local requirements. The region adjacent to lithium (first layer) uses high lithium salt concentration to minimize interfacial resistance, while the region adjacent to the positive electrode (second layer) uses lower lithium salt concentration to maximize ionic conductivity. This local quality approach allows the electrolyte to simultaneously achieve low interfacial resistance and high bulk conductivity.
2Power
If the EO:Li molar ratio is increased to improve ionic conductivity, then power is improved, but interfacial resistance with lithium increases
Solution Approach 1:
The electrolyte is segmented into two layers with different EO:Li ratios. The first layer has low EO:Li (1:1 to 3:1) to minimize interfacial resistance with lithium, while the second layer has high EO:Li (4:1 to 30:1) to maximize ionic conductivity. This segmentation resolves the contradiction by spatially separating the conflicting requirements.
Solution Approach 2:
The first polymer electrolyte layer acts as an intermediary between lithium and the second layer. It provides a low-resistance interface with lithium while the second layer provides high ionic conductivity to the positive electrode. This intermediary structure mediates between the conflicting requirements of low interfacial resistance and high bulk conductivity.
3Device complexity
If a single-layer polymer electrolyte is used, then device complexity is reduced, but both interfacial resistance and ionic conductivity cannot be optimized simultaneously
Solution Approach 1:
The electrolyte is divided into two functional layers, each optimized for its specific role. This segmentation enables simultaneous optimization of interfacial resistance and ionic conductivity, overcoming the limitations of single-layer structures while maintaining relatively simple device architecture.
Solution Approach 2:
The electrolyte uses a composite structure combining two different polymer electrolyte compositions. The first layer uses high lithium salt concentration composition for low interfacial resistance, while the second layer uses low lithium salt concentration composition for high ionic conductivity. This composite material approach allows simultaneous optimization of multiple performance parameters.
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 significantly reduces interfacial resistance and discharge overvoltage, enhancing discharge capacity and output characteristics of the all-solid battery.
Implementation Method 1
the low ionic conductivity of the polymer electrolyte and second, the interfacial resistance between lithium and the polymer electrolyte can be mentioned
Implementation Method 2
This configuration significantly reduces interfacial resistance and discharge overvoltage, enhancing discharge capacity and output characteristics of the all-solid battery
Data Source
Figure 1~2
Figure 3(a)~4
AI summary
The present invention relates to a polymer electrolyte for an all-solid battery, having a multi-layer structure and, more particularly, to a polymer electrolyte having a multi-layer structure, which comprises a first polymer electrolyte layer and a second polymer electrolyte layer, wherein the EO : Li molar ratio of a poly(ethylene oxide) (PEO)-based polymer and a lithium salt is different between the first and second polymer electrolyte layers. The application of the solid polymer electrolyte of the present invention to the all-solid battery can remarkably reduce the interfacial resistance with lithium and the discharge overvoltage, resulting in a sufficient discharge capacity, and can improve output characteristics and energy density.