Beta-Alumina Electrolyte Sheet With Na2O Gradient for Fast Sodium Cycling
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Solution Overview
Problem
Conventional beta-alumina-based solid electrolyte sheets used in all-solid-state sodium secondary batteries exhibit high irreversible capacity, leading to poor first charge and discharge capacities and rapid charge and discharge characteristics.
Innovation Solution
A solid electrolyte sheet with a higher concentration of Na2O on its surface compared to its middle thickness direction (C1 > C2) is developed, which enhances the first charge-discharge efficiency and rapid charge and discharge characteristics by facilitating sodium ion conduction and reducing irreversible capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional beta-alumina-based solid electrolyte sheet is used, then the battery structure is simple and easy to manufacture, but the irreversible capacity is high leading to poor first charge and discharge capacities
Solution Approach 1:
The solid electrolyte sheet employs a concentration gradient structure where Na2O concentration varies through the thickness direction, with higher concentration at the surface (C1) than at the middle (C2). This local variation in composition creates an Na2O-rich phase at the surface that serves as a buffer to cancel irreversible capacity while maintaining overall structural simplicity.
Solution Approach 2:
The invention changes the compositional parameter of Na2O concentration through the thickness direction of the electrolyte sheet. By controlling that C1 > C2 (where C1 is surface concentration and C2 is middle concentration), the sheet achieves improved first charge-discharge efficiency without requiring complex multi-layer structures.
2Productivity
If a conventional beta-alumina-based solid electrolyte sheet is used, then the manufacturing process is straightforward, but the rapid charge and discharge characteristics are poor
Solution Approach 1:
The surface of the electrolyte sheet is engineered with a distinct Na2O-rich phase (higher concentration C1) compared to the interior (concentration C2). This localized compositional difference creates favorable conditions for rapid sodium ion exchange at the electrode interface, improving charge-discharge rates while maintaining straightforward manufacturing of the overall sheet structure.
Solution Approach 2:
The electrolyte sheet is pre-formed with a concentration gradient (C1 > C2) during manufacturing, so that the Na2O-rich surface phase is already in place before battery assembly. This preliminary structuring enables immediate improvement in rapid charge-discharge characteristics without requiring additional post-processing or complex manufacturing steps.
3Quantity of substance
If the thickness of the solid electrolyte is reduced to increase energy density, then the energy density per unit volume increases, but the manufacturing precision requirements increase
Solution Approach 1:
Rather than requiring uniform high precision throughout a thin sheet, the invention employs a controlled local variation in Na2O concentration through the thickness direction. The surface layer (with concentration C1) is distinguished from the interior (with concentration C2), allowing the sheet to be thin for high energy density while the concentration gradient provides functional benefits without demanding extreme manufacturing precision.
Solution Approach 2:
The electrolyte sheet functions as a composite structure with different Na2O concentrations at different locations (surface vs. interior). This composite approach, where C1 > C2, allows the thin sheet to achieve both high energy density and improved electrochemical performance, as the Na2O-rich surface phase compensates for the reduced overall thickness.
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 proposed solid electrolyte sheet significantly improves the first charge and discharge capacities and rapid charge and discharge characteristics of all-solid-state sodium secondary batteries, addressing the limitations of conventional sheets.
Implementation Method 1
sodium ions are released, instead of those in the negative electrode, from Na2O contained in the surface of the solid electrolyte sheet
Implementation Method 2
an Na2O-rich phase is present in the surface of the solid electrolyte sheet, a sodium ion-conducting path can be easily formed at the interface between the electrode layer and the solid electrolyte sheet
Data Source
AI summary
Provided is a beta-alumina-based solid electrolyte sheet capable of increasing the first charge and discharge capacities and rapid charge and discharge characteristics of an all-solid-state sodium secondary battery. A solid electrolyte sheet contains β-alumina and/or β″-alumina and satisfies C1>C2 where C1 represents a concentration of Na2O in a surface of the solid electrolyte sheet and C2 represents a concentration of Na2O in a middle of a thickness direction of the solid electrolyte sheet.