Protective Coating for Electrode Preventing Polysulfide Release

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Solution Overview

Problem

Electrochemical energy accumulators face issues with the release of chemically active materials during discharge, leading to reduced capacity and lifetime, and increased risk of short circuits due to incomplete elementalization of polysulfides and degradation of active materials.

Innovation Solution

A protective coating comprising methionine and a metal oxide, such as aluminum oxide, is applied to the active material layer, allowing only lithium ions to pass through while preventing polysulfides from escaping, thereby maintaining the chemically active material within the electrode and reducing degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the chemically active material is intercalated into the electrically conductive matrix to enable electrochemical reactions, then the electrochemical performance is improved, but the chemically active material is released during discharge leading to reduced capacity and lifetime

Engineering Contradiction:

Improveelectrochemical performanceVSAvoidlifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

A protective coating comprising metal oxide and methionine is applied to the active material layer before electrochemical reactions occur. This coating prevents polysulfide dissolution and active material degradation from the outset, counteracting the harmful release effects before they can degrade the electrode structure and reduce lifetime.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The protective coating combines metal oxide (such as aluminum oxide) with methionine (a sulfur-containing amino acid) to create a composite protective layer. This composite structure provides both physical barrier properties and chemical stability, effectively preventing polysulfide release while maintaining electrochemical performance.

Inventive Principle:

Principle #40Composite materials

2Duration of action of stationary object

If a protective coating is applied to prevent chemically active material release, then lifetime is improved, but ion transport may be hindered

Engineering Contradiction:

ImprovelifetimeVSAvoidion transport speed

Core Design Contradiction:

Duration of action of stationary objectVSSpeed

Solution Approach 1:

The protective coating is designed with a porous structure that allows lithium ions to diffuse through while physically blocking larger polysulfide molecules. The pore size is optimized to permit fast ion transport necessary for maintaining electrochemical performance while preventing harmful material release.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The protective coating acts as an intermediary layer between the active material and the electrolyte. It mediates the interaction by allowing beneficial ion transport while blocking harmful polysulfide dissolution, thus protecting the electrode without hindering electrochemical reactions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If polysulfides migrate to the counter electrode, then capacity is reduced, but short circuit risk increases

Engineering Contradiction:

ImprovecapacityVSAvoidshort circuit risk

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The protective coating converts the harmful effect of polysulfide mobility into a beneficial selective barrier function. It allows the electrode to maintain its electrochemical activity while preventing polysulfides from migrating to the counter electrode, thus eliminating both capacity loss and short circuit risks simultaneously.

Inventive Principle:

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

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 protective coating significantly enhances the lifetime of electrochemical energy accumulators by preventing the release of chemically active materials and reducing the risk of short circuits, ensuring consistent performance and extended service life.

Implementation Method 1

The protective coating comprising methionine and at least one metal oxide is only permeable to certain ions, such as lithium ions, but not to polycompounds of the chemically active material of the electrode, such as polysulfide

Methodology Applied

Scientific EffectIon-selective permeation: Semipermeable Membrane

Implementation Method 2

both methionine and the metal oxide are largely chemically stable under the influence of the electrolyte, a function of the protective coating is retained during operation of the electrochemical energy accumulator

Methodology Applied

Scientific EffectChemical stability:

Implementation Method 3

This is made possible by specifying a pore size of less than 2 micrometers with a layer thickness of more than 3.5 micrometers. Furthermore, the metal oxide is chemically stable against an electrolyte

Methodology Applied

Scientific EffectPhysical containment through porous structure: Porosity

Data Source

PatentUS10897041B2Electrode, electrochemical energy accumulator with an electrode, and method for producing an electrode

Publication Date: 2021.01.19 MERCEDES BENZ GROUP AG

AI summary

An electrode for an electrochemical energy accumulator includes a catalyst layer, where the catalyst layer includes an electrically conductive matrix and a chemically active material which is intercalated into the electrically conductive matrix. A protective coating is disposed on the catalyst layer, where the protective coating includes at least one metal oxide and methionine.