Silicon Anode SEI Uniformity for Longer Lithium Battery Life

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Solution Overview

Problem

Lithium secondary batteries face challenges in maintaining uniformity and stability of the solid electrolyte interphase (SEI) layer on silicon-based anode active material particles, leading to non-uniform volume expansion and reduced lifespan due to side reactions with the electrolyte solution.

Innovation Solution

The anode active material layer includes silicon-based active material particles with a carbon coating and a solid electrolyte interphase (SEI) layer formed on their surface, using a polyacrylic acid-based copolymer binder to ensure uniform thickness and stability, reducing resistance and preventing side reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based active material particles are used to increase capacity, then the battery capacity is improved, but the SEI layer becomes non-uniform and lifespan is reduced

Engineering Contradiction:

Improvebattery capacityVSAvoidlifespan

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by creating a non-uniform SEI layer with different thicknesses in different regions of the silicon-based active material particles. The SEI layer has a first thickness in a first region and a second thickness in a second region, allowing different parts of the particle to experience different expansion and reaction characteristics, thereby improving overall lifespan while maintaining high capacity.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If silicon-based active material particles are used to increase capacity, then the battery capacity is improved, but volume expansion becomes non-uniform

Engineering Contradiction:

Improvebattery capacityVSAvoidvolume expansion uniformity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent addresses volume expansion non-uniformity by creating a SEI layer with spatially varying thickness. The first region has a different SEI layer thickness compared to the second region, which allows different local expansion behaviors that collectively improve the overall volume expansion uniformity of the silicon-based active material particles during charging and discharging cycles.

Inventive Principle:

Principle #3Local quality

3Reliability

If SEI layer thickness is increased to prevent side reactions, then reliability is improved, but manufacturing precision becomes difficult to control

Engineering Contradiction:

Improveresistance to side reactionsVSAvoidSEI layer thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent resolves the manufacturing precision challenge by intentionally creating a non-uniform SEI layer with controlled different thicknesses in different regions. Rather than attempting to create a perfectly uniform thickness that is difficult to control, the invention specifies that the first thickness and second thickness differ by 1 nm or more, providing a clear manufacturing target that is easier to achieve and verify.

Inventive Principle:

Principle #3Local quality

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 solution results in improved capacity retention and extended lifespan of the lithium secondary battery by maintaining a uniform SEI layer thickness, suppressing side reactions, and enhancing the anode's resistance to electrolyte interactions.

Implementation Method 1

each of the composite particles includes a silicon-based active material particle, and a solid electrolyte interphase (SEI) layer formed on at least a portion of a surface of the silicon-based active material particle

Methodology Applied

Scientific EffectSolid electrolyte interphase (SEI) layer formation:

Implementation Method 2

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS20250293235A1Anode for secondary battery, method of fabricating the same and lithium secondary battery including the same

Publication Date: 2025.09.18 SK INNOVATION CO LTD

AI summary

An anode for a lithium secondary battery includes an anode current collector, and an anode active material layer formed on at least one surface of the anode current collector. The anode active material layer includes an anode active material and an anode binder. The anode active material includes a plurality of composite particles, each of the composite particles include a silicon-based active material particle, and a solid electrolyte interphase (SEI) layer formed on at least a portion of a surface of the silicon-based active material particle. A relative standard deviation of thickness values of the SEI layer of the composite particles, which are measured by an X-ray photoelectron spectroscopy (XPS) from 9 different composite particles among the plurality of composite particles after repeating 100 cycles of charging and discharging is 20% or less.