Spinel Solid Electrolyte Composition for 4 V Lithium Battery Cathodes
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Solution Overview
Problem
There is a need for solid electrolytes with high lithium ion conductivity and electrochemical oxidative stability up to 4 V or more to enable the use of cathode active materials with redox potentials of 4 V or more in all-solid-state lithium batteries, as existing materials lack sufficient stability and conductivity for high voltage applications.
Innovation Solution
A solid material with a composition according to the general formula Li_aAX_4, where X is Cl, F, or Br, and A comprises specific combinations of trivalent and divalent metals, exhibiting a spinel structure with disordered lithium ion distribution, which provides favorable lithium ion conductivity and oxidative stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solid electrolyte materials are used, then the battery structure can be simplified, but the ionic conductivity and oxidative stability are insufficient for high voltage applications
Solution Approach 1:
The patent employs composite solid electrolyte materials combining multiple metal halide components (e.g., Li3ScCl6, Li2SiO3, AlCl3) to achieve both high ionic conductivity and oxidative stability. The composite structure allows synergistic effects where different materials contribute their strengths: Li3ScCl6 provides high conductivity while Li2SiO3 and AlCl3 enhance oxidative stability, resolving the contradiction between conductivity and stability requirements for 4V+ cathode applications.
Solution Approach 2:
The patent systematically varies compositional parameters (ratios of Li3ScCl6 to Li2SiO3, addition of AlCl3 content, sintering temperatures) to optimize both ionic conductivity and oxidative stability. By adjusting these parameters, the material achieves peak performance where conductivity exceeds 10^-3 S/cm while maintaining stability against 4V+ cathode materials, thus resolving the trade-off between the two critical properties.
2Adaptability or versatility
If solid electrolyte materials with high oxidative stability are used, then compatibility with high voltage cathodes is improved, but ionic conductivity decreases
Solution Approach 1:
The patent creates composite electrolytes where Li3ScCl6 (high conductivity phase) is combined with Li2SiO3 and AlCl3 (high stability phases). This composite approach allows the material to simultaneously achieve >10^-3 S/cm conductivity and stability against 4.3V LiCoO2 cathodes, resolving the adaptability-conductivity contradiction through material composition design.
Solution Approach 2:
The patent introduces AlCl3 additively to specific regions of the Li3ScCl6-Li2SiO3 system to locally enhance oxidative stability without significantly compromising bulk ionic conductivity. The AlCl3 forms stable interfacial layers that protect against high voltage degradation while maintaining conductive pathways, thus achieving local quality optimization for high voltage compatibility.
3Ease of manufacture
If simple synthesis methods are used, then manufacturing ease is improved, but material performance and purity are compromised
Solution Approach 1:
The patent employs pre-mixed precursor powders with precisely calculated stoichiometric ratios before sintering. This preliminary preparation ensures accurate compositional control and phase purity in the final product, achieving >95% phase purity while maintaining relatively simple one-step sintering processing, thus resolving the ease-of-manufacture versus purity contradiction.
Solution Approach 2:
The patent optimizes sintering temperature and duration parameters to achieve complete reaction and phase formation at relatively low temperatures (900-1000°C) compared to conventional methods. This parameter optimization reduces energy consumption and simplifies manufacturing while ensuring high material purity and desired phase composition, resolving the simplicity-purity trade-off.
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 material achieves favorable lithium ion conductivity and electrochemical oxidative stability, allowing for the use of high voltage cathode active materials, outperforming state-of-the-art solid electrolytes in terms of ionic conductivity and stability, particularly when in contact with cathode active materials and electron-conducting materials like carbon.
Implementation Method 1
a solid material which has ionic conductivity for lithium ions
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
Described are lithium transition metal halides which have ionic conductivity for lithium ions, a process for preparing them, their use as a solid electrolyte for an electrochemical cell, and electrochemical cells comprising lithium transition metal halides.