LLZO Ceramic Particle Coating for Low Grain-Boundary Resistance

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Solution Overview

Problem

LLZO-based materials face high grain-boundary electrical resistance, making cold-pressed products non-conductive, and existing solutions like sintering and conductive polymers suffer from unwanted reactions or low ionic conductivity.

Innovation Solution

A method involving coating LLZO ceramic particles with a liquid component containing a coating agent like tris(trimethylsilyl) phosphate, which enhances surface ionic conductivity and allows for cold pressing with low grain-boundary resistance without altering the LLZO structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sintering and hot-pressing are used to overcome grain-boundary resistance, then ionic conductivity is improved, but unwanted reactions occur between LLZO and cathode materials at temperatures greater than 1000°C

Engineering Contradiction:

Improveionic conductivityVSAvoidunwanted reactions

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the processing parameters from high-temperature sintering (>1000°C) to low-temperature cold pressing, thereby maintaining ionic conductivity while avoiding unwanted chemical reactions between LLZO and cathode materials. The coating agent enables this parameter change by providing surface modification that facilitates ionic transport without requiring thermal activation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The coating agent acts as an intermediary layer on the LLZO particle surface, enabling ionic conductivity without direct contact between LLZO and cathode materials. This intermediate coating prevents harmful chemical reactions while still allowing Li-ion transport, thus resolving the contradiction between conductivity and chemical stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If cold pressing is used to manufacture solid electrolyte, then processing complexity is reduced, but grain-boundary electrical resistance becomes too high for conduction

Engineering Contradiction:

Improveprocessing simplicityVSAvoidelectrical conductivity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality modification by coating only the surface of LLZO particles with a conductive coating agent. This localized treatment enhances grain-boundary ionic conductivity at the particle surfaces without altering the bulk LLZO structure, enabling cold-pressed electrolytes to achieve sufficient conductivity while maintaining processing simplicity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite structure where LLZO particles are coated with a conductive coating agent, forming a composite material that combines the high bulk conductivity of LLZO with the low grain-boundary resistance of the coating. This composite approach enables cold pressing to produce conductive solid electrolytes without complex processing.

Inventive Principle:

Principle #40Composite materials

3Reliability

If conductive polymer is added to LLZO to improve ionic conductivity, then conductivity is enhanced, but the ionic conductivity of polymeric components remains low

Engineering Contradiction:

Improveionic conductivityVSAvoidmaterial composition complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the use of conductive polymers with a coating agent that forms a thin, stable layer on LLZO particles. This coating approach is more effective than incorporating polymeric components, as it provides sufficient ionic conductivity without the low conductivity limitations of polymers, while also simplifying the material composition.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 coated ceramic particles exhibit high surface ionic conductivity and fast Li-ion transport, enabling the production of solid electrolytes with low grain-boundary resistance, as demonstrated by improved ionic conductivity measurements.

Implementation Method 1

covering, at least partially, the base ceramic particle with a liquid component containing a coating agent of formula AO[OSi(C m H 2m+i ) 3 ] 3

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

drying the liquid component such as to form a coating adhering to the surface of the base ceramic particle

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

the coated ceramic particle can be cold pressed to manufacture a solid electrolyte having a low grain-boundary resistance providing a fast Li-ions transport

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentEP4270578A1Method for producing a coated ceramic particle based on a LLZO material

Publication Date: 2023.11.01 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

Figure 1~2

AI summary

Method for producing a coated ceramic particle, the method comprising: a) having at least one base ceramic particle comprising, for at least 90 % of its weight, a LLZO material of formula LixLa3ZryMzO12 wherein 6≤x≤7, 1≤y≤2, 0≤z≤1, and M is chosen in the group consisting in Al, Ga, Nb, Ta, W and their mixtures, b) covering, at least partially, the base ceramic particle with a liquid component containing a coating agent of formula AO[OSi(CmH2m+1)3]3, wherein 1 ≤ m ≤ 20 and A is chosen in the group consisting in P, Si, B and their mixtures, c) drying the liquid component such as to form a coating adhering to the surface of the base ceramic particle.