Silicon Anode Coating with Pyrogenic Oxides for Longer Cycle Life

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Solution Overview

Problem

Existing lithium ion batteries with silicon-based anode materials face challenges in maintaining structural integrity and cycle life due to significant volume changes and low conductivity, particularly when silicon content exceeds 7 wt.%, leading to poor electrochemical performance.

Innovation Solution

A coating layer comprising 5-80 wt.% of an organic binder and 20-95 wt.% of unmodified or surface-modified pyrogenic oxide particles, such as aluminum or magnesium oxides, is applied to the anode electrode to enhance stability and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon content in anode active material is increased to achieve high capacity, then specific capacity is improved, but structural integrity deteriorates due to volume expansion

Engineering Contradiction:

Improvespecific capacityVSAvoidstructural integrity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

A coating layer containing 20-95 wt.% metal compound particles is applied beforehand to the silicon-containing anode active material surface. This coating layer acts as a cushioning protective layer that accommodates the volume expansion of silicon during lithium insertion, preventing structural degradation while allowing high silicon content (≥7 wt.%) for high capacity

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent uses composite material structure where silicon-containing anode active material is combined with metal compound coating layer. The composite structure integrates the high capacity advantage of silicon with the structural stability advantage of metal compounds, enabling both high specific capacity and maintained structural integrity

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon content is increased to achieve high capacity, then specific capacity is improved, but cycle life deteriorates due to pulverization

Engineering Contradiction:

Improvespecific capacityVSAvoidcycle life

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The metal compound coating layer is applied beforehand to prevent pulverization during cycling. This protective layer absorbs mechanical stress from silicon expansion/contraction, preventing particle disintegration and maintaining electrode integrity over extended cycling, thus improving cycle life while maintaining high silicon content for high capacity

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The coating layer forms a flexible protective shell around silicon particles. This shell accommodates volume changes through elastic deformation rather than brittle fracture, preventing pulverization and delamination during repeated charge-discharge cycles, thereby extending cycle life

Inventive Principle:

Principle #30Flexible shells and thin films

3Stability of the object's composition

If coating layer thickness is increased to improve protection, then structural stability is improved, but energy density deteriorates

Engineering Contradiction:

Improvestructural stabilityVSAvoidenergy density

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The patent employs a thin coating layer (specific thickness not specified but implied to be thin) that provides sufficient protective function without excessive thickness. This thin film approach maintains structural stability while minimizing the non-active material volume, preserving high energy density despite the presence of protective coating

Inventive Principle:

Principle #30Flexible shells and thin films

4Manufacturing precision

If metal compound particle size is decreased to improve coating uniformity, then coating quality is improved, but aggregation increases

Engineering Contradiction:

Improvecoating uniformityVSAvoidaggregation

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent specifies metal compound particle size in the range of 5 nm to 100 nm (number mean primary particle size). This parameter optimization achieves sufficient coating uniformity for protective function while the small particle size reduces aggregation tendency. The specific size range balances coating quality and aggregation control

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP4625525A1Coated anode electrode with metal compound and organic binder

Publication Date: 2025.10.01 EVONIK OPERATIONS GMBH

AI summary

The invention provides an anode electrode for a lithium ion battery, containing an anode electrode containing at least 7 wt.-% silicon and a coating layer comprising 5-80 wt.% of an organic binder and 20-95 wt.% of a metal compound selected from the group consisting of unmodified or surface modified pyrogenic aluminum oxide, unmodified or surface modified pyrogenic magnesium oxide or unmodified or surface modified pyrogenic silicon oxide particles and mixtures thereof, wherein the metal compound consists of aggregates of primary particles with a number mean primary particle size d50 of 5 nm - 100 nm.