NaSICON Solid Electrolyte Ionic Conductivity Optimization
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Solution Overview
Problem
There is a need to improve the ionic conductivity of solid electrolyte layers in all solid state batteries to enhance the battery characteristics of these devices.
Innovation Solution
A solid electrolyte with a NaSICON-type crystal structure, represented by the formula Li1+aZr2−bMc(PO4)3, is developed, where Li can be partially substituted with certain elements, and M contains elements that stabilize the tetragonal or cubic crystal structure of ZrO2, improving ion conductivity. The electrolyte is synthesized using partially stabilized zirconia, and the battery is produced by sintering the electrolyte layer with electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If M content is increased to improve ionic conductivity, then ion conductivity is improved, but a different phase forms which decreases ion conductivity
Solution Approach 1:
The patent optimizes the compositional parameters a, b, and c in the formula Li1+aZr2−bMc(PO4)3 to achieve maximum ionic conductivity. Specifically, it sets 0.01≤b≤1.90 and 0.01≤c≤1.90 with b+c≤1.91, and preferably 0.01≤c≤0.38, most preferably 0.02≤c≤0.20. This parameter optimization ensures sufficient M content to stabilize the tetragonal or cubic crystal structure while preventing excessive M content that would form different phases and reduce conductivity.
Solution Approach 2:
The patent uses composite substitution where M contains at least one first element (from Y, Ca, Mg, Sc, or lanthanoid elements) capable of stabilizing the tetragonal or cubic crystal structure of high-temperature phase ZrO2, and optionally at least one second element (from Al, Ga, Sc, In, Ge, Ti, Ru, Sn, Hf, Ce, V, Nb, Ta, Bi, or W). This composite approach allows the solid electrolyte to maintain stable crystal structure while achieving high ionic conductivity through synergistic effects of different elements.
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 improved ionic conductivity of the solid electrolyte layer results in all solid state batteries with enhanced battery characteristics, such as increased power density, although excessive M content can lead to decreased ion conductivity by forming a different phase.
Implementation Method 1
a solid electrolyte which has a NaSICON-type crystal structure... a solid electrolyte layer which has a high ion conductivity
Implementation Method 2
The positive electrode is joined by sintering to one surface of the solid electrolyte layer. The negative electrode is joined by sintering to the other surface of the solid electrolyte layer.
Data Source
AI summary
A solid electrolyte having a NaSICON-type crystal structure and represented by a general formula Li1+aZr2−bMc(PO4)3. In the general formula, Li may be partially substituted with at least one selected from the group consisting of Na, K, Rb, Cs, Ag, and Ca, P may be partially substituted with at least one of B and Si, M contains at least one first element capable of stabilizing or partially stabilizing the tetragonal or cubic crystal structure of a high-temperature phase of ZrO2, −0.50≤a≤2.00, 0.01≤b≤1.90, and 0.01≤c≤1.90.