All-solid battery electrolyte softening for ion conduction
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Solution Overview
Problem
All-solid lithium ion secondary batteries face challenges with high ion conduction resistance at interfaces, poor charge-discharge behavior, safety risks due to sulfide decomposition, and the need for high-temperature processing, which affects electrode layer formation and ion conductivity.
Innovation Solution
Incorporating a first inorganic solid electrolyte with a low transition metal content and a second inorganic solid electrolyte with a high transition metal content into the battery, where the first electrolyte softens and enters voids formed by the second electrolyte, forming a well-connected ion and electron conduction path, reducing ion conduction resistance and enabling lower-temperature processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintering is performed to physically connect constituent particles between or within layers, then mechanical connection is improved, but ion conduction resistance increases due to substance generation at sintered interfaces
Solution Approach 1:
The patent introduces a glass body as an intermediary substance at the interfaces between solid electrolyte particles and electrode particles. This glass body fills the gaps and forms a eutectic composition that reduces ion conduction resistance while maintaining mechanical connection, resolving the contradiction between mechanical strength and ion conduction performance.
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating a glass body with specific composition (containing SiO2, B2O3, and metal oxides) that forms a eutectic composition at the sintered interfaces. This compositional change enables lower sintering temperatures and reduces ion conduction resistance while maintaining mechanical integrity.
2Ease of manufacture
If glass body with softening temperature of 700°C or higher is added to promote sintering, then sintering is promoted, but processing temperature must be increased to 700°C or higher
Solution Approach 1:
The patent changes the softening temperature parameter of the glass body by selecting specific composition ranges (SiO2: 30-70 wt%, B2O3: 5-40 wt%, metal oxides: 5-20 wt%) that create a eutectic composition with lower melting point. This enables sintering at temperatures below 700°C while still achieving effective particle connection and reduced ion conduction resistance.
3Adaptability or versatility
If sulfide-based solid electrolyte is used, then all-solid battery structure is achieved, but harmful gas generation occurs due to decomposition
Solution Approach 1:
The patent converts the harmful decomposition behavior of sulfide-based solid electrolytes into a beneficial process by using the decomposition temperature characteristic to form a protective glass phase. The glass body composition is designed to stabilize the interface and prevent harmful gas generation while maintaining the all-solid battery structure and ion conduction 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
This approach enhances lithium ion conductivity, charge-discharge performance, and safety by forming a stable ion conduction path and reducing harmful gas generation, while allowing for battery formation at lower temperatures.
Implementation Method 1
the first electrolyte softens and enters voids formed by the second electrolyte
Implementation Method 2
enhances lithium ion conductivity, charge-discharge performance, and safety by forming a stable ion conduction path
Data Source
AI summary
In the all-solid secondary battery of the present invention, a positive electrode layer and a negative electrode layer are disposed on both sides of a solid electrolyte layer, a first inorganic solid electrolyte and a second inorganic solid electrolyte are included into at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, the content of transition metal in the first inorganic solid electrolyte is less than 15% by mass on oxide basis, and the content of transition metal in the second inorganic solid electrolyte is 15% by mass or more on oxide basis.