Layered Silicon-Graphite Anode Binders for Stable Lithium Batteries

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Solution Overview

Problem

Lithium secondary batteries face challenges in mechanical stability and capacity due to mechanical deformation caused by changes in anode binders, leading to reduced battery life and performance.

Innovation Solution

A lithium secondary battery design featuring a multi-layered anode active material structure with a first layer using a styrene-butadiene rubber (SBR) binder and a second layer using an acryl-based binder, along with a mixture of silicon and graphite-based active materials, to enhance adhesion and prevent electrode expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single-type anode binder is used, then the structure is simple and manufacturing is easy, but mechanical deformation occurs and stability deteriorates

Engineering Contradiction:

Improvebinder application simplicityVSAvoidanode mechanical stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The anode binder is segmented into two distinct types: a first binder (SBR-based) for the first anode active material layer and a second binder (acryl-based) for the second anode active material layer. This segmentation allows each binder to be optimized for its specific layer, preventing mechanical deformation while maintaining manufacturing feasibility through a systematic coating process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different binder materials are applied to different locations/layers of the anode structure. The first binder is used in the first anode active material layer adjacent to the current collector, while the second binder is used in the second anode active material layer. This local differentiation addresses specific mechanical stability requirements of each layer.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If silicon-based active material is used to increase capacity, then energy density improves, but mechanical deformation and electrode wrinkling occur

Engineering Contradiction:

Improvebattery capacityVSAvoidelectrode mechanical stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The anode is segmented into two layers: a first anode active material layer with graphite-based material providing structural stability, and a second anode active material layer with silicon-based material providing high capacity. This segmentation allows the silicon to contribute to capacity without causing overall electrode deformation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The anode uses a composite structure combining graphite-based active material in the first layer and silicon-based active material in the second layer. This composite approach leverages the dimensional stability of graphite to constrain the expansion and contraction of silicon, preventing electrode wrinkling while maintaining high capacity.

Inventive Principle:

Principle #40Composite materials

3Reliability

If a multi-layered anode structure with different binders is used, then mechanical stability and capacity are improved, but device complexity increases

Engineering Contradiction:

Improvebattery mechanical stabilityVSAvoidanode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The anode is divided into two functional layers with different binders, where the first layer uses SBR-based binder and the second layer uses acryl-based binder. This segmentation improves mechanical stability by matching binder properties to specific layer requirements, while the layered structure remains manageable through systematic manufacturing processes.

Inventive Principle:

Principle #1Segmentation

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 multi-layered structure improves mechanical and chemical stability, prevents electrode wrinkling, and enhances output and capacity by effectively managing silicon-based active material expansion and contraction.

Implementation Method 1

a first anode binder containing a styrene-butadiene-based rubber (SBR) binder and a second anode binder containing an acryl-based binder

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

Each of the first anode active material and the second anode active material includes a silicon-based active material... effectively managing silicon-based active material expansion and contraction

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11876217B2Lithium secondary battery

Publication Date: 2024.01.16 SK ON CO LTD

AI summary

A lithium secondary battery includes a cathode, a separator, and an anode including an anode current collector and an anode active material layer formed on the anode current collector and facing the cathode with the separator interposed therebetween. The anode active material layer includes a first anode active material layer formed on the anode current collector and including a first anode active material and a first anode binder containing a styrene-butadiene-based rubber (SBR) binder and a second anode active material layer formed on the first anode active material layer and including a second anode active material and a second anode binder containing a acryl-based binder. Each of the first anode active material and the second anode active material includes a silicon-based active material and a graphite-based material and contains 2 to 9.5 parts by weight of silicon with respect to the 100 part by weight of the graphite-based active material.