Garnet Solid Electrolyte Composition to Suppress Impurity Electron Paths
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Solution Overview
Problem
Conventional solid-state batteries using garnet-type solid electrolyte ceramics face issues with increased electron conductivity due to impurity formation, leading to short-circuiting and leakage current, especially when transition metal elements are present in large amounts.
Innovation Solution
A solid electrolyte ceramic with a garnet-type crystal structure, comprising lithium, lanthanum, oxygen, and one or more transition metal elements like cobalt, nickel, manganese, or iron, is developed, with specific chemical composition and content ratios to suppress electron conductivity while maintaining excellent ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transition metal elements are contained in relatively large amounts to suppress Li-Bi-O-based compound production, then electron conductivity increase is suppressed, but impurities containing transition metal are produced which increase electron conductivity
Solution Approach 1:
The patent changes the chemical composition parameters by specifying precise ranges for Li (α: 5.0≤α≤8.0), La (β: 2.5≤β≤3.5), and transition metal elements (γ: 1.5≤γ≤2.5) in the garnet-type structure. This parameter optimization ensures sufficient transition metal content to suppress Li-Bi-O compound formation while preventing excessive transition metal that would create impurities, thereby resolving the contradiction between electron conductivity suppression and impurity formation
Solution Approach 2:
The patent creates a composite solid electrolyte ceramic material combining multiple elements (Li, La, and specific transition metals: Co, Ni, Mn, or Fe) in a garnet-type crystal structure. This composite approach allows the material to benefit from the electron conductivity suppression provided by transition metals while the controlled composition prevents harmful impurity formation, achieving both objectives simultaneously
2Reliability
If Bi is added to garnet-type solid electrolyte to improve ion conductivity, then ion conductivity increases, but Li-Bi-O-based compounds are produced at grain boundaries which increase electron conductivity
Solution Approach 1:
The patent optimizes the Bi content parameter within the garnet-type structure by defining specific ranges for the D element (which includes Bi) where γ satisfies 1.5≤γ≤2.5. This controlled parameter change allows Bi to be present in sufficient amounts to maintain high ion conductivity while preventing excessive Bi that would lead to Li-Bi-O compound formation at grain boundaries, thus resolving the contradiction between ion conductivity improvement and harmful compound formation
Solution Approach 2:
The patent converts the potential harm of Bi into a benefit by carefully controlling its content within the garnet-type structure. The controlled Bi content promotes high ion conductivity (benefit) while the same controlled content prevents Li-Bi-O compound formation (avoiding harm). The transition metal elements further assist by suppressing impurity formation, transforming the Bi-related issue into a controlled compositional parameter that delivers net benefit
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 ceramic effectively reduces electron conductivity, preventing short-circuiting and leakage current, even when transition metal elements are present in large amounts, while maintaining high ion conductivity.
Implementation Method 1
the solid electrolyte layer contains a solid electrolyte ceramic, and is responsible for ion conduction between the positive electrode layer and the negative electrode layer
Data Source
AI summary
A solid electrolyte ceramic that has a garnet-type crystal structure, and contains: at least Li (lithium), La (lanthanum), and O (oxygen); and one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron), wherein, when a content of La and a total content of the one or more transition metal elements are denoted respectively by X (mol %) and Y (mol %), the solid electrolyte ceramic satisfies any one of the following relational expressions (1) to (3): (1) 0.01≤Y≤6.0 in the range of 147.5<X<150.0; (2) 0.01≤Y≤9.0 in the range of 145.0<X<147.5; and (3) 0.01≤Y≤12.0 in the range of 132.0≤X≤145.0.