Composite Protective Layer for Lithium Metal Anodes

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Solution Overview

Problem

Lithium-based secondary batteries face challenges with dendrite growth and electrolyte instability, leading to short circuits and reduced cycle stability due to the uneven separation and dissolution of lithium, as well as decomposition of electrolyte components during operation.

Innovation Solution

A composite protective layer is introduced on the lithium metal anode with a lithium-ion-conducting material and a polymer, featuring conductive paths and a lattice-like structure, along with an intermediate layer to prevent direct contact with the electrolyte, reducing internal resistance and enhancing flexibility and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a lithium metal anode is used to achieve high specific energy density, then the energy density is improved, but dendrite formation occurs leading to short circuits and reduced reliability

Engineering Contradiction:

Improvespecific energy densityVSAvoidshort circuit prevention

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A composite protective layer is introduced as an intermediary between the lithium metal anode and the electrolyte. This layer includes a lithium-ion-conducting inorganic material (such as garnet-type Li7La3Zr2O12 or sulfide-based Li10GeP2S12) combined with a polymer matrix, forming a stable interface that prevents direct contact between lithium and electrolyte, thereby eliminating dendrite formation while maintaining high ionic conductivity for energy efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The protective layer is constructed as a composite material combining inorganic lithium-ion-conducting ceramics (providing structural stability and ion conductivity) with organic polymer matrices (providing flexibility and mechanical stability). This composite structure simultaneously achieves high specific energy density by enabling lithium metal anode usage while preventing dendrite growth through the stable composite interface

Inventive Principle:

Principle #40Composite materials

2Reliability

If a coating with inorganic material is applied to the negative electrode, then dendrite growth is inhibited, but the number of interfaces increases leading to higher internal resistance

Engineering Contradiction:

Improvedendrite growth inhibitionVSAvoidnumber of interfaces

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The inorganic lithium-ion-conducting material and polymer matrix are merged into a single integrated composite protective layer structure. This unified composite layer reduces the number of discrete interfaces compared to multi-layer coatings, minimizing interfacial resistance while maintaining effective dendrite growth inhibition through the combined properties of both materials

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If multiple protective layers are used to prevent dendrite growth, then reliability is improved, but the device complexity and internal resistance increase

Engineering Contradiction:

Improvecycle stabilityVSAvoidmulti-layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of using multiple separate protective layers, the invention employs a single composite material combining inorganic lithium-ion-conducting phases with polymer matrices. This composite approach achieves the protective functions of multiple layers (dendrite prevention, mechanical stability, ionic conductivity) within a unified structure, reducing device complexity and minimizing interfacial resistance while maintaining high cycle stability

Inventive Principle:

Principle #40Composite materials

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 composite material effectively inhibits dendrite growth, improves cycle stability, and reduces internal resistance by minimizing interfaces, thereby enhancing the performance and longevity of lithium-based batteries.

Implementation Method 1

the first material is a lithium-ion-conducting material and the second material is a polymer, and the protective layer has conductive paths which are formed through material channels in the lithium-ion-conducting material

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentEP3075018B1Electrochemical cell and method for producing an electrochemical zell

Publication Date: 2021.09.22 ROBERT BOSCH GMBH

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AI summary

The invention relates to an electrochemical cell, comprising a negative electrode, a positive electrode, a protective layer which is arranged on the negative electrode and isolates the negative electrode from the positive electrode, and an electrolyte, wherein the negative electrode at least partially comprises metallic lithium, and wherein the protective layer arranged on the negative electrode is formed from a composite material comprising at least a first material and a second material. The invention furthermore relates to a corresponding method for producing an electrochemical cell.