Bilayer Solid Electrolyte for Moisture-Stable Lithium-Air Batteries

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Solution Overview

Problem

Lithium air batteries face instability due to the formation of lithium hydroxide (LiOH) at the cathode, leading to decreased ionic conductivity and potential cracking of the solid electrolyte, which is exacerbated by alkaline conditions.

Innovation Solution

A bilayer solid electrolyte structure is introduced, comprising a first electrolyte layer with an inorganic lithium ion conductor and a second layer containing a compound represented by Formula 1 (Li1−3x+4y(HfaM1−a)2−y(PO4−xQx)3, which provides stability against moisture and strong bases, thereby protecting the first layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a solid electrolyte is used in a lithium air battery, then high capacity and theoretical specific energy of 3,500 Wh/kg are achieved, but the electrolyte degrades due to moisture and alkaline conditions at the cathode

Engineering Contradiction:

Improvespecific energyVSAvoidelectrolyte stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The solid electrolyte is divided into two distinct layers: a first layer comprising an inorganic lithium ion conductor that provides high ionic conductivity for battery operation, and a second layer comprising a compound of formula (1) that provides chemical stability against moisture and alkaline conditions. This segmentation allows each layer to specialize in one function, resolving the contradiction between energy performance and stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite electrolyte structure combining two different material systems: inorganic lithium ion conductors (such as LATP, LLZO, or LISICON) and hafnium-based phosphate compounds (HfaM1-a)2-y(PO4-xQx)3. This composite approach leverages the high ionic conductivity of inorganic materials while the hafnium phosphate layer provides exceptional chemical inertness against LiOH and moisture, thus achieving both high specific energy and reliable stability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If moisture is blocked completely at the cathode, then electrolyte stability is improved, but lithium hydroxide formation and alkaline conditions still occur during discharge

Engineering Contradiction:

Improveelectrolyte stabilityVSAvoidalkaline conditions

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Instead of trying to prevent the formation of LiOH and alkaline conditions (which are inherent to lithium air battery discharge chemistry), the invention uses the second electrolyte layer comprising hafnium-based phosphate compounds that are specifically designed to be stable in strong alkaline environments. The material converts the harmful alkaline conditions into a manageable environment where the electrolyte remains stable and functional.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte by introducing hafnium-based phosphate compounds with specific stoichiometric ratios (formula (1) where M is monovalent to hexavalent, Q is halogen or pseudohalogen, and a, x, y are within specific ranges). These parameter changes give the material unique chemical stability properties that allow it to withstand the alkaline conditions generated during battery discharge without degrading.

Inventive Principle:

Principle #35Parameter changes

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 bilayer structure maintains excellent ionic conductivity and prevents degradation, enhancing the stability and lifetime of lithium air batteries under humid and alkaline conditions.

Implementation Method 1

a first electrolyte layer including an inorganic lithium ion conductor

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 2

heat-treating the mixture to remove the vehicle and form the compound represented by Formula 1

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

heat-treating the mixture to remove the vehicle and form the compound represented by Formula 1

Methodology Applied

Scientific EffectThermal decomposition: Pyrolysis

Data Source

PatentUS12362386B2Solid electrolyte, preparation method thereof, lithium air battery including the solid electrolyte, and electrochemical device including the solid electrolyte

Publication Date: 2025.07.15 SAMSUNG ELECTRONICS CO LTD

AI summary

A solid electrolyte includes: a first electrolyte layer including an inorganic lithium ion conductor; and a second electrolyte layer disposed on at least one side of the first electrolyte layer and including a compound represented by Formula 1Li1−3x+4y(HfaM1−a)2−y(PO4−xQx)3 Formula 1wherein in Formula 1, M is at least one of a monovalent to a hexavalent element, wherein 0<a≤1, 0≤x<⅓, and 0≤y<2, and Q is F, Cl, Br, I, a pseudohalogen, or a combination thereof.