All-Solid-State Battery Separator With Iodine Gradient for Lower Resistance
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Solution Overview
Problem
All-solid-state batteries with sulfide solid electrolytes face challenges in reducing battery resistance, which affects their performance.
Innovation Solution
The use of a sulfide solid electrolyte with a specific composition and iodine concentration distribution, measured by SEM-EDX, in the separator layer of the battery, where the iodine concentration gradient is controlled to optimize ionic conduction, is proposed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium halide is added to sulfide solid electrolyte to improve ionic conductivity, then ionic conductivity increases, but battery resistance reduction is insufficient
Solution Approach 1:
The patent applies local quality by creating a non-uniform iodine concentration distribution within the solid electrolyte layer. The iodine concentration is higher near the negative electrode and lower near the positive electrode, forming a gradient structure. This localized variation in composition optimizes ionic conductivity at different positions, particularly enhancing conductivity near the negative electrode where it is most needed, thereby more effectively reducing overall battery resistance than uniform distribution could achieve.
Solution Approach 2:
The patent employs parameter changes by systematically varying the iodine concentration as a continuous gradient rather than a fixed value. The concentration parameter changes from approximately 1-5 wt% near the negative electrode to lower concentrations near the positive electrode. This continuous parameter variation allows optimization of the electrolyte's ionic conductivity profile to match the specific operational requirements at different electrode interfaces, achieving superior battery resistance reduction.
2Stability of the object's composition
If iodine is uniformly dispersed in sulfide solid electrolyte, then ionic conduction becomes uniform, but battery resistance cannot be sufficiently reduced
Solution Approach 1:
The patent applies local quality by creating a non-uniform iodine concentration distribution within the solid electrolyte layer. The iodine concentration is higher near the negative electrode and lower near the positive electrode, forming a gradient structure. This localized variation in composition optimizes ionic conductivity at different positions, particularly enhancing conductivity near the negative electrode where it is most needed, thereby more effectively reducing overall battery resistance than uniform distribution could achieve.
Solution Approach 2:
The patent inverts the conventional approach of uniform distribution by deliberately creating a non-uniform gradient structure. Instead of dispersing iodine uniformly throughout the electrolyte, the concentration is intentionally varied with position, being highest at the negative electrode interface and decreasing toward the positive electrode. This inversion of the distribution pattern allows targeted optimization of ionic conductivity where it most impacts battery resistance.
3Reliability
If specific composition ratio of LiI and LiBr is used in sulfide solid electrolyte, then ionic conductivity is optimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes by systematically varying the iodine concentration as a continuous gradient rather than a fixed value. The concentration parameter changes from approximately 1-5 wt% near the negative electrode to lower concentrations near the positive electrode. This continuous parameter variation allows optimization of the electrolyte's ionic conductivity profile to match the specific operational requirements at different electrode interfaces, achieving superior battery resistance reduction.
Solution Approach 2:
The patent uses composite materials by combining sulfide solid electrolyte with lithium halide compounds (LiI and LiBr) in specific proportions. The composite structure integrates multiple components with complementary properties: the sulfide base provides structural stability while the lithium halide additives enhance ionic conductivity. The optimized composition range (LiI: 10-20 mol%, LiBr: 0-15 mol%) balances performance enhancement with manufacturing feasibility.
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 reduces battery resistance by ensuring uniform iodine distribution, enhancing ionic conductivity and overall battery performance.
Implementation Method 1
The solid electrolyte serves as a separator as well as an ion conduction pathway. The ionic conductivity of a solid electrolyte is one of factors that dictate the battery resistance of an all-solid-state battery.
Data Source
AI summary
The all-solid-state battery includes a positive electrode layer, a separator layer, and a negative electrode layer. The separator layer includes a sulfide solid electrolyte. In a cross section parallel to the thickness direction of the separator layer, a line analysis is performed by SEM-EDX to measure an atom concentration of sulfur and an atom concentration of iodine on a straight line extending from the negative electrode layer to the positive electrode layer in parallel to the thickness direction. A regression line is derived from the results of the line analysis, and the regression line has a slope of 0.019 to 0.036. The independent variable of the regression line is a position in the thickness direction of the separator layer. The dependent variable of the regression line is a ratio of the atom concentration of iodine to the atom concentration of sulfur.