Ammonium Complex Metal Halide Electrolytes for Low-Temperature Synthesis
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Solution Overview
Problem
Current solid electrolyte materials for solid-state lithium batteries face challenges such as high synthesis temperatures, brittleness, hygroscopicity, safety concerns, and limited ionic conductivity, making them unsuitable for mass production and posing risks due to their reactivity with moisture and heat.
Innovation Solution
Development of ammonium-containing complex metal halides with specific compositions and structures that enhance bulk ion conductivity, allowing for safer and more efficient production methods, including a range of ionic conductivities from 0.001 mS/cm to 15 mS/cm across various temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide based materials are used for solid electrolyte, then chemical and electrochemical stability is improved, but synthesis temperature must be above 1000-1200 °C and ionic conductivity is limited to up to 1.0 mS/cm at room temperature
Solution Approach 1:
The patent changes the chemical composition parameters by introducing fluorine and ammonium into the solid electrolyte structure, forming compounds like (NH4)3Li3YCl9 and (NH4)3Li3YBr9. This compositional parameter change enables synthesis at lower temperatures (400-650°C) while achieving ionic conductivities exceeding 1 mS/cm at room temperature, resolving the contradiction between stability and synthesis energy requirements
Solution Approach 2:
The patent creates composite electrolyte materials combining ammonium-containing complex metal halides with specific stoichiometric ratios of lithium, rare earth metals, and halogens. These composite structures achieve both the chemical stability of oxide materials and the lower synthesis temperature/higher ionic conductivity characteristics of halide materials
2Adaptability or versatility
If halide solid electrolytes are used, then deformability and plasticity are improved allowing high compatibility with active electrode materials, but they are hygroscopic and form hydrates or undergo hydrolysis upon exposure to moisture
Solution Approach 1:
The patent applies local quality by creating specific crystal structures where fluorine atoms are positioned to shield the hydrolytically sensitive metal-halogen bonds. The fluorine substitution at specific lattice positions creates localized regions of enhanced stability while maintaining the overall deformability and plasticity of the halide structure, resolving the contradiction between adaptability and moisture resistance
3Reliability
If sulfide solid electrolytes are used, then ionic conductivity is improved (up to 25 mS/cm), but they have poor electrochemical stability and release toxic H2S gas when reacting with water and heat
Solution Approach 1:
The patent converts the harmful reactivity of sulfides by replacing the sulfur component with fluorine-containing ammonium complexes. The fluorine atoms, which are highly electronegative and form strong bonds, replace the weak S-H bonds that lead to H2S release. This transformation maintains high ionic conductivity (exceeding 1 mS/cm at room temperature) while eliminating the toxic gas generation hazard, effectively converting a harmful material system into a safe one
4Reliability
If high energy ball milling based solid-state synthesis methods are used for halides, then room temperature ionic conductivity above 1 mS/cm is achieved, but expensive binary halide reactants and high temperature annealing are required making mass production difficult
Solution Approach 1:
The patent applies preliminary action by pre-forming ammonium halide complexes with controlled stoichiometry before the final sintering step. The reactants are prepared in advance with precise compositional ratios, and the synthesis proceeds in a single low-temperature step (400-650°C) without requiring subsequent high-temperature annealing or expensive binary halide reactants, enabling straightforward mass production while achieving ionic conductivities above 1 mS/cm
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 ammonium-containing complex metal halides provide improved ionic conductivity and safety, enabling cost-effective mass production of solid-state lithium batteries with reduced risks from moisture and heat reactivity.
Implementation Method 1
The solid electrolyte material can have improved bulk ion conductivity. In embodiments, the solid electrolyte material can have a bulk ion conductivity ranging from 0.001 mS/cm to 15 mS/cm for a temperature range from -80°C to 200°C
Data Source
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AI summary
A solid electrolyte material can include an ammonium-containing complex metal halide, in an embodiment, the ammonium-containing complex metal halide can be represented by (NH4)nM3-z(Mek+)fXn+3-z+k*f, wherein 0<n, 0≤z<3, 2≤k<6, 0≤f≤1; M comprises at least an alkali metal element, X comprises a halogen, and Me comprises a divalent metal element, a trivalent metal element, a tetravalent metal element, a pentavalent metal element, a hexavalent metal element or any combination thereof.