Polysiloxane Coating for Lithium Metal Anode Stability

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Solution Overview

Problem

Lithium metal anodes in lithium-ion batteries face challenges with high reactivity, large volume changes, low cycle efficiency, and dendrite growth, especially under high current density conditions, which affect their performance and longevity.

Innovation Solution

A polymer layer coating is applied to the lithium metal or lithium alloy electrodes, comprising a polysiloxane polymerization product derived from specific monomers, which enhances adhesion, stability, and cycle efficiency, thereby reducing dendrite formation and improving the electrodes' lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lithium metal anodes are treated with monochlorosilanes to form a siloxane layer, then cycle efficiency is improved and dendrite formation is decreased, but the treatment does not survive in high current density cycling

Engineering Contradiction:

Improvecycle efficiencyVSAvoidsurvival in high current density cycling

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent changes the chemical composition parameters of the coating layer by using divalent or trivalent metal halides (such as SiCl2, GeCl2, SnCl2, SbCl3) instead of monochlorosilanes. This parameter change results in a polymerized coating structure that maintains stability under high current density cycling conditions while improving cycle efficiency and reducing dendrite formation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite coating layer by polymerizing metal halides in situ on the lithium metal anode surface. This composite structure, formed by the polymerization of metal halide monomers, provides enhanced mechanical stability and chemical resistance compared to simple siloxane layers, enabling the coating to survive high current density cycling.

Inventive Principle:

Principle #40Composite materials

2Object-generated harmful factors

If a siloxane layer is formed on lithium metal anodes, then dendrite formation is reduced, but the layer does not provide sufficient protection under high current density conditions

Engineering Contradiction:

Improvedendrite formationVSAvoidprotection stability in high current density cycling

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The patent modifies the coating layer parameters by using metal halides with higher valency (divalent or trivalent) that polymerize to form cross-linked networks. This changes the physical and chemical properties of the coating, providing superior mechanical strength and adhesion that prevents dendrite formation while maintaining stability under high current density conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs in situ polymerization where the metal halide monomers automatically polymerize on the anode surface when exposed to moisture or electrolyte, forming a self-assembled protective layer. This self-service mechanism ensures uniform coverage and strong adhesion without requiring additional processing steps, providing reliable protection against dendrite formation.

Inventive Principle:

Principle #25Self-service

3Quantity of substance

If lithium metal anodes undergo large volume changes during cycling, then high capacity is achieved, but mossy structure forms and cycle efficiency decreases

Engineering Contradiction:

Improvelithium capacityVSAvoidstructural stability during volume changes

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies a thin polymerized coating layer that acts as a flexible protective shell on the lithium metal anode. This thin film structure accommodates the large volume changes during lithium insertion and extraction cycles while maintaining structural integrity, preventing the formation of mossy lithium structures and preserving cycle efficiency.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent forms a protective coating layer beforehand that cushions the lithium metal anode against the mechanical stress of volume changes during cycling. This pre-formed protective layer absorbs and distributes the mechanical stress, preventing structural degradation and mossy lithium formation that would otherwise occur during repeated expansion and contraction.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 polysiloxane coating significantly improves the cycle efficiency and extends the lifetime of lithium metal anodes by providing a stable and rigid layer that protects the electrodes from degradation, outperforming traditional siloxane coatings in high current density environments.

Implementation Method 1

the polymer layer includes a polymerization product of a monomer having Formula I

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentUS11515538B2In-situ polymerization to protect lithium metal electrodes

Publication Date: 2022.11.29 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An electrode including an electrode active material including lithium (Li) and a polymer layer coating at least a portion of the electrode active material is provided. The polymer layer includes a polymerization product of a monomer having Formula I:where R1 and R2 are independently an aryl or a branched or unbranched C1-C10 alkyl and X1 and X2 are independently chlorine (Cl), bromine (Br), or iodine (I).