Thin Sodium Ion Solid Electrolyte Sheet Design
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Solution Overview
Problem
Reducing the thickness of solid electrolytes in sodium ion batteries increases internal resistance, leading to decreased battery characteristics such as discharge capacity and operating voltage, and results in low ionic conductivity due to surface layer Na2O concentration variations and flatness issues during the production of sodium ion-conductive crystal-containing solid electrolyte sheets.
Innovation Solution
A sodium ion-conductive crystal-containing solid electrolyte sheet with a thickness of 500 μm or less and a flatness of 200 μm or less, using β″-alumina and NASICON crystals, with controlled Na2O concentration gradients to maintain high ionic conductivity, and a pre-firing method to reduce contraction and volatilization of sodium components during firing, ensuring uniform electrode application and reduced cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the solid electrolyte is reduced to increase energy density, then the energy density per unit volume increases, but the internal resistance increases and battery characteristics deteriorate
Solution Approach 1:
The patent uses a slurry formulation technique analogous to hydraulic/pneumatic processing, where raw material powder is mixed with a specific solvent ratio (5-15 mass%) to create a flowable slurry. This allows the slurry to be uniformly applied to form thin solid electrolyte sheets with controlled thickness (50-500 μm), achieving high energy density while maintaining uniform composition that prevents excessive internal resistance
Solution Approach 2:
The patent systematically optimizes multiple parameters including solvent ratio (5-15 mass%), firing temperature (900-1400°C), and firing time (1-24 hours) to achieve the desired balance between thinness and performance. By controlling these parameters, the solid electrolyte maintains low internal resistance even at reduced thickness, resolving the contradiction between energy density and reliability
2Volume of moving object
If the thickness of the solid electrolyte is reduced, then the energy density increases, but the discharge capacity and operating voltage decrease
Solution Approach 1:
The patent employs precise parameter control including firing temperature (900-1400°C) and time (1-24 hours) to optimize the sintering process. This ensures that even at thin thickness (50-500 μm), the solid electrolyte develops sufficient density and crystalline structure to maintain high ionic conductivity, thereby preserving discharge capacity and operating voltage while achieving high energy density
Solution Approach 2:
The patent uses composite raw material formulations containing specific ratios of metal oxides (e.g., Al2O3, SiO2, P2O5, Na2O) that form interconnected crystalline phases during firing. This composite structure ensures adequate mechanical strength and ionic conduction pathways are maintained even in thin sheets, preventing degradation of power characteristics
3Ease of manufacture
If the green sheet is fired to produce solid electrolyte, then the solid electrolyte sheet is formed, but the ionic conductivity decreases due to surface layer Na2O concentration variations
Solution Approach 1:
The patent applies preliminary actions by carefully formulating the slurry composition before firing, including controlling the solvent ratio (5-15 mass%) and ensuring homogeneous mixing of raw materials. This preliminary preparation prevents excessive sodium loss during firing by establishing a stable green sheet structure, thereby maintaining surface layer Na2O concentration and preserving ionic conductivity in the final product
Solution Approach 2:
The patent optimizes firing parameters including temperature (900-1400°C) and time (1-24 hours) to control the degree of sintering and sodium volatilization. By precisely controlling these parameters, the patent achieves sufficient densification for good manufacturability while minimizing surface layer composition changes, thereby maintaining high ionic conductivity
4Ease of manufacture
If the flatness of the solid electrolyte is poor, then the production process becomes easier, but the electrode application becomes uneven and internal resistance increases
Solution Approach 1:
The patent uses slurry formulation with controlled solvent ratio (5-15 mass%) to create a flowable mixture that can be uniformly applied to form sheets with excellent flatness. The hydraulic properties of the slurry allow for smooth, defect-free application that produces flat surfaces, enabling both easy handling and precise electrode coating with uniform thickness, thereby resolving the contradiction between ease of manufacture and manufacturing precision
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 solution enables sodium ion batteries with improved battery characteristics, increased ionic conductivity, and reduced production defects, such as cracks, by maintaining uniform thickness and Na2O concentration, thus enhancing discharge capacity and energy density while minimizing internal resistance.
Implementation Method 1
a solid electrolyte sheet containing at least one type of sodium ion-conductive crystal selected from β″-alumina and NASICON crystal
Implementation Method 2
making a raw material powder for the solid electrolyte into a slurry, forming a green sheet from the slurry, and then firing the green sheet
Data Source
AI summary
Provided are a sodium ion-conductive crystal-containing solid electrolyte sheet capable of giving excellent battery characteristics even when reduced in thickness, and an all-solid-state battery using the same. The solid electrolyte sheet contains at least one type of sodium ion-conductive crystal selected from β″-alumina and NASICON crystal and has a thickness of 500 μm or less and a flatness of 200 μm or less.