Perovskite Solid Electrolyte for High Conductivity and Stability
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Solution Overview
Problem
Lithium ion batteries with inorganic solid electrolytes face challenges due to the reactivity between titanium-based electrolytes and negative electrode materials, leading to electronic conductivity and potential internal short-circuiting, which reduces their practical application and lithium ionic conductivity.
Innovation Solution
A solid electrolyte material with a perovskite crystal structure, represented by ABO3, is developed, where the A-site includes Li and vacancies, and the B-site contains Ti or other elements like Ta, Cr, Fe, Co, and Nb, optimizing the unit cell volume and infrared absorption spectrum to maintain high lithium ionic conductivity while enhancing chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium is used in the solid electrolyte to achieve high lithium ionic conductivity, then the lithium ionic conductivity is improved, but the electrolyte reacts with the negative electrode material having a strong reducing property to exhibit electronic conductivity due to the reduction of tetravalent titanium into trivalent titanium
Solution Approach 1:
The patent introduces a dual-element substitution strategy where elements at both A-site and B-site work together as intermediaries to protect the titanium from reduction. The A-site element (e.g., La, Sr, Na) provides structural stability and ionic conductivity, while the B-site element (e.g., Ta, Nb, W) with higher reduction resistance than titanium acts as a protective intermediary, preventing direct reduction of titanium by the negative electrode material.
Solution Approach 2:
The patent creates a composite solid electrolyte material with the formula A1-x-yLixM1-y-zTizO3-w, combining multiple elements in specific proportions. This composite structure integrates the high ionic conductivity of lithium-containing perovskite with the reduction resistance of elements like Ta, Nb, or W, achieving both high lithium ionic conductivity and chemical stability simultaneously.
2Stability of the object's composition
If constituent elements are replaced with elements having higher reduction resistance to improve stability, then the reduction resistance is improved, but the lithium ionic conductivity degrades considerably to about 1/10 to 1/100
Solution Approach 1:
The patent optimizes the compositional parameters x, y, z, and w in the formula A1-x-yLixM1-y-zTizO3-w to achieve the best balance between reduction resistance and ionic conductivity. By carefully controlling the substitution ratios and maintaining specific parameter ranges, the patent achieves both high stability and high lithium ionic conductivity, overcoming the trade-off between these two properties.
Solution Approach 2:
The patent applies different substitution strategies at different sites of the perovskite structure. The A-site substitution with elements like La, Sr, or Na provides local structural stability and maintains ionic conductivity pathways, while the B-site substitution with Ta, Nb, or W provides localized reduction resistance. This local differentiation allows each site to contribute its optimal property to the overall material performance.
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 achieves high lithium ionic conductivity at room temperature, avoiding the reduction in conductivity caused by constituent element differences and improving the stability of the electrolyte, thus enhancing the performance and practicality of lithium ion batteries.
Implementation Method 1
Perovskite compounds which have a high lithium ionic conductivity and are easily obtainable by a solid phase reaction in an air atmosphere are attracting attention. A representative example of such a material is La0.67−XLi3XTiO3. One of the compounds having a composition of X=0.11 shows a high lithium ionic conductivity at room temperature Of 1.5×10−3 S/cm
Implementation Method 2
A peak top νtop of an absorption peak in an infrared absorption spectrum satisfies Expression (1) νtop (cm−1)=4.7×V1/3 (pm)−b
Data Source
AI summary
According to one embodiment, a solid electrolyte material is an oxide represented by ABO3, wherein an A-site includes Li and vacancies. A cubic root V1/3 of a unit cell volume is within a range of 386 pm≦V1/3≦397 pm. A peak top νtop of an absorption peak in an infrared absorption spectrum satisfies Expression (1)νtop (cm−1)=4.7×V1/3 (pm)−b (1),provided that 1220≦b≦1240.