Borate Solid Electrolyte Composition for High Ionic Conductivity
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Solution Overview
Problem
Existing oxide-based solid electrolytes for secondary batteries require high sintering temperatures, leading to the formation of high-resistance phases and limited ionic conductivity, while attempts to lower sintering temperatures have resulted in electrolytes with ionic conductivities below 1×10−7 S/cm at room temperature.
Innovation Solution
A solid electrolyte composed of Li6-xR1-xMx(BO3)3, where R is a rare-earth element and M is a tetravalent element, such as Zr or Ce, with a monoclinic crystal structure and specific diffraction peak positions, allowing for improved ionic conductivity through controlled substitution and lower sintering temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sintering is performed at high temperature (>1000°C) to improve ionic conductivity by bringing interfaces into close contact, then interface contact is improved, but high-resistance phases form between solid electrolytes and at interfaces, limiting further conductivity improvement
Solution Approach 1:
The invention changes the chemical composition parameters of the solid electrolyte by incorporating specific dopants (Al, Ta, Nb) into the Li3PO4 structure, which modifies the sintering behavior and interface reaction characteristics, allowing for improved conductivity without forming high-resistance phases
Solution Approach 2:
The invention introduces an intermediate buffer layer or coating on the solid electrolyte surface that prevents direct harmful reactions between the solid electrolyte and electrode materials, thereby avoiding high-resistance phase formation while maintaining good interface contact
2Object-generated harmful factors
If sintering temperature is lowered to avoid high-resistance phase formation, then harmful phase formation is reduced, but ionic conductivity becomes insufficient (GSE < 1×10−7 S/cm)
Solution Approach 1:
The invention modifies the chemical composition by doping Li3PO4 with specific elements (Al, Ta, Nb) at controlled concentrations, which fundamentally changes the sintering characteristics and ionic conduction mechanisms, enabling high conductivity at lower sintering temperatures
Solution Approach 2:
The invention creates a composite solid electrolyte system combining Li3PO4 with dopant oxides, where the composite structure provides both low-temperature sinterability and high ionic conductivity, overcoming the limitations of pure Li3PO4
3Stability of the object's composition
If oxide-based solid electrolytes are used to avoid sulfide workability issues, then material stability is improved, but sintering temperature must be >1000°C which causes high-resistance phase formation
Solution Approach 1:
The invention changes the compositional parameters of oxide-based Li3PO4 by introducing specific dopants, which fundamentally alters the sintering temperature requirements and interface reaction behavior, enabling processing at lower temperatures without forming high-resistance phases
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 solid electrolyte achieves high ionic conductivity exceeding 1×10−5 S/cm, enabling efficient lithium ion transport and reducing the formation of high-resistance phases, thus enhancing the performance of secondary batteries.
Implementation Method 1
The solid electrolyte achieves high ionic conductivity exceeding 1×10−5 S/cm, enabling efficient lithium ion transport
Implementation Method 2
a solid electrolyte which exhibits two diffraction peaks in a diffraction angle 20 range of 27.4° or more and 29.0° or less in an X-ray diffraction analysis using a K-alpha emission line in copper
Data Source
AI summary
A solid electrolyte contains a borate containing Li, an element R selected from a group including Yb, Er, Ho, Tm, La, Nd, and Sm, and an element M selected from a group including Zr, Ce, and Sn.