Multi-Cation LLZO Doping for Cubic Phase Stability and Conductivity
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Solution Overview
Problem
Existing oxide-based solid electrolytes for Li-ion batteries have lower conductivity compared to liquid or sulfide electrolytes, and conventional doping methods to stabilize the cubic LLZO phase in Li-garnet materials can decrease Li-ion conductivity and increase costs.
Innovation Solution
Incorporation of multiple aliovalent cation dopants into the Li 7 La 3 Zr 2 O 12 material, including subvalent and supervalent cations, to stabilize the cubic LLZO structure without inducing significant Li vacancies, maintaining Li content and charge balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If substitutional dopants are incorporated to stabilize cubic LLZO phase, then room temperature conductivity is improved (exceeding 1 mS/cm), but Li content decreases due to induced Li vacancies
Solution Approach 1:
The patent changes the doping strategy from single-element substitution to multi-element co-doping, where multiple dopants work synergistically to stabilize the cubic phase while minimizing Li vacancy formation. This parameter change in the doping approach allows maintaining higher Li content while achieving phase stabilization.
Solution Approach 2:
The patent uses composite doping with multiple elements (e.g., Al + Ta, Ga + Nb) where each dopant contributes different properties. This composite approach allows the material to achieve cubic phase stability through synergistic effects while reducing the need for excessive Li vacancies, thereby preserving Li content.
2Stability of the object's composition
If Li-site dopants (e.g., Al3+, Ga3+) are used to stabilize cubic phase, then cubic structure is achieved, but conductivity decreases due to reduced Li content
Solution Approach 1:
The patent merges Li-site doping with Zr-site doping in a co-doping strategy. By combining dopants at different sites (e.g., Al at Li-site and Ta at Zr-site), the material achieves cubic phase stability while the Zr-site dopants compensate for conductivity losses by inducing additional Li vacancies without significantly reducing Li content.
Solution Approach 2:
The patent applies local quality by placing different dopants at different crystallographic sites (Li-site and Zr-site) to achieve different local effects. Li-site dopants provide structural stabilization while Zr-site dopants primarily generate Li vacancies for conductivity enhancement, allowing each dopant to optimize its local function.
3Stability of the object's composition
If higher valance elements are used to induce Li vacancies for cubic stabilization, then cubic phase is stabilized, but material cost increases due to use of high-cost elements
Solution Approach 1:
The patent segments the doping function across multiple elements with different valences. Instead of relying solely on expensive high-valance elements (5+, 6+), the patent combines lower-cost lower-valance elements (2+, 3+) with smaller amounts of high-valance elements, dividing the stabilization task among multiple dopants to reduce overall material cost.
Solution Approach 2:
The patent replaces expensive high-valance dopants with cheaper alternative dopants (such as Mg2+, Ca2+, Y3+) that can achieve similar cubic phase stabilization effects. This substitution with lower-cost elements reduces material expenses while maintaining the desired cubic structure and conductivity properties.
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 multi-dopant strategy enhances Li-ion conductivity, increases material stability through entropy benefits, and reduces costs by utilizing lower-cost elements, while retaining high Li content and achieving a cubic phase at room temperature.
Implementation Method 1
stabilize the cubic LLZO structure without inducing Li vacancies. Potential benefits of this multi-dopant strategy are (1) higher conductivity, due to higher retained Li content, (2) higher stability due to entropy benefits associated with larger number of dopants
Data Source
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AI summary
A lithium garnet material has the formula Li7+δLa3Zr2-x-y-zM1xM2yM3zO12, where M1 is one or a combination of (Y, In, Mg, Ca, Ba, Sc, Sr, Ru) with oxidation number (valence) lower than 4+, M2 is one or a combination of (Bi, Ta, Nb, Mo, Sb, Te) with oxidation number (valence) higher than 4+, and M3 is one or a combination of (Hf, Ti, Sn, Si) with oxidation number (valence) equal to 4+, subject to 0<x≤1, 0<y≤1, 0≤z≤2, 0<x+y+z≤2, and -0.2<δ<0.2. Also provided is a lithium garnet material which is the same as the aforementioned lithium garnet material except that M1 is one or a combination of (Y, In, Mg, Ca, Ba, Sr, Ru) and M2 is one or a combination of (Bi, Ta, Nb, Mo, Sb, Te, W). Lithium oxide solid-state electrolyte materials have the same formula as the aforementioned lithium garnet materials but also include Ge for M3.