Li-Nb-Ta Oxide Buffer Layers for Solid Electrolyte Interfaces
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Solution Overview
Problem
Existing all-solid-state batteries face challenges with lithium ion deficient layers at the cathode/solid electrolyte interface, which can be addressed by using effective buffer layers that enhance lithium ion conduction and reduce resistance.
Innovation Solution
The use of ternary Li-Nb-Ta oxides as buffer layers or solid electrolyte materials, with specific compositions and structures that provide high ionic conductivity and permittivity, is proposed to improve lithium ion transfer and reduce resistance at the cathode/solid electrolyte interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer layer is introduced at the cathode/solid electrolyte interface to enhance lithium ion transfer, then lithium ion conduction is improved, but the device structure becomes more complex
Solution Approach 1:
The patent combines multiple functions into a single buffer layer material (Li-Nb-Ta oxide). This material simultaneously provides high lithium ion conductivity, high permittivity for electrical stability, and chemical compatibility with both cathode and solid electrolyte, thereby improving lithium ion conduction while avoiding the need for multiple separate functional layers
Solution Approach 2:
The patent employs composite Li-Nb-Ta oxide materials with specific compositional ratios (0.3 ≤ Nb/(Nb+Ta) ≤ 0.7). This composite approach leverages the complementary properties of niobium and tantalum oxides to achieve optimal balance between ionic conductivity and permittivity, resolving the contradiction between improved conduction and structural complexity
2Reliability
If amorphous LiNbO3 or LiTaO3 is used as buffer layer to resolve high-resistance layers, then lithium ion transfer is enhanced, but the material selection is limited
Solution Approach 1:
The patent systematically varies the compositional parameters of Li-Nb-Ta oxides, specifically the Nb/(Nb+Ta) ratio within the range 0.3-0.7, and controls the crystalline/amorphous state through annealing temperature. This parametric approach enables continuous optimization of lithium ion conductivity and permittivity, greatly expanding material selection flexibility beyond fixed-composition LiNbO3 or LiTaO3
Solution Approach 2:
By creating a ternary Li-Nb-Ta oxide system rather than using binary LiNbO3 or LiTaO3 separately, the patent expands the available compositional space. The synergistic interaction between Li, Nb, and Ta allows for a broader range of properties to be accessed, enhancing both lithium ion transfer and material adaptability
3Power
If high permittivity materials are used at cathode/solid electrolyte interface to improve lithium ion conduction, then power density increases, but the ionic conductivity may be insufficient
Solution Approach 1:
The patent optimizes the annealing temperature parameter (400-600°C) to control the degree of crystallinity in Li-Nb-Ta oxide buffer layers. This thermal parameter control enables simultaneous achievement of high permittivity (for power density) and high ionic conductivity (for reliability), resolving the contradiction between these two properties
Solution Approach 2:
The Li-Nb-Ta oxide composite system provides a synergistic effect where the combination of Li2SiO3, Nb2O5, and Ta2O5 in specific ratios delivers both high permittivity and high ionic conductivity. The composite nature allows the material to satisfy both requirements for high power density and high reliability that cannot be met by single-phase materials alone
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 ternary Li-Nb-Ta oxides effectively alleviate lithium ion deficient layers, enhancing the power density of batteries by providing improved lithium ion conduction and permittivity, making them suitable for use as both buffer layers and solid electrolyte materials in all-solid-state lithium batteries.
Implementation Method 1
ternary Li-Nb-Ta oxides... providing effective lithium ion conduction... ionic conductivity of at least 2.0 x 10^-6 S/cm
Implementation Method 2
providing favourable ranges of both ionic conductivity and permittivity... said mixed oxide shows a permittivity of at least 100
Data Source
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AI summary
The present invention relates to mixed oxides of lithium, niobium and tantalum, as well as to a process for making the mixed oxides, and also to all-solid-state lithium batteries comprising the mixed oxides. The invention describes the use of the mixed oxides as buffer layers between a positive electrode active material and a solid electrolyte, in a battery, and the use of the mixed oxides as solid electrolyte materials.