Layered Silicon-Graphite Anode Structure for Low Interface Resistance

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Solution Overview

Problem

Existing lithium secondary batteries face limitations in energy density due to the use of graphite-based materials, with Si-based materials experiencing volume expansion issues leading to interface resistance, adhesive force deterioration, and reduced lifespan.

Innovation Solution

A negative electrode structure with layered active materials, including varying ratios of artificial and natural graphite, and silicon-based materials, to enhance adhesive force and reduce interfacial resistance, improving energy density and lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Si-based material is used to improve energy density, then theoretical capacity increases, but volume expansion occurs leading to adhesive force deterioration

Engineering Contradiction:
Improvetheoretical capacityVSAvoidadhesive force
Core Design Contradiction:
Quantity of substanceVSStrength

Solution Approach 1:

The patent uses a composite material system combining Si-based active material with graphite-based active material and binder polymer. The graphite component accommodates volume expansion while maintaining structural integrity, and the binder polymer provides adhesive force to prevent electrode detachment during charging-discharging cycles.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent optimizes the content ratio of Si-based active material to graphite-based active material, and adjusts binder polymer content based on the Si-based material content. By dynamically adjusting these parameters, the electrode maintains both high capacity and sufficient adhesive force under different operating conditions.

Inventive Principle:
Principle #35Parameter changes

2Quantity of substance

If Si-based material is used to improve energy density, then theoretical capacity increases, but interface resistance increases due to side reactions with electrolyte

Engineering Contradiction:
Improvetheoretical capacityVSAvoidinterface resistance
Core Design Contradiction:
Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The graphite-based active material acts as an intermediary between the Si-based material and the electrolyte. It provides a stable interface that reduces direct contact between the reactive Si-based material and electrolyte, thereby minimizing side reactions and interface resistance while still allowing lithium ion transport.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Stability of the object's composition

If SiOx material is used to reduce volume expansion, then lifespan characteristics improve, but interface resistance increases due to side reactions

Engineering Contradiction:
Improvevolume expansion rateVSAvoidinterface resistance
Core Design Contradiction:
Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent combines SiOx-based active material with graphite-based active material and binder polymer in a composite structure. This composite approach maintains the low volume expansion advantage of SiOx while using graphite and binder to reduce interface resistance and prevent electrode detachment.

Inventive Principle:
Principle #40Composite materials

4Quantity of substance

If Si-based material is used to improve energy density, then theoretical capacity increases, but electrode detachment occurs due to adhesive force reduction

Engineering Contradiction:
Improvetheoretical capacityVSAvoidelectrode detachment
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

The patent adjusts the binder polymer content as a function of Si-based active material content. When Si-based material content is high, binder polymer content is increased to provide sufficient adhesive force, preventing electrode detachment while maintaining high capacity.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS20250336957A1Negative Electrode for Lithium Secondary Battery and Lithium Secondary Battery Including the Same
Publication Date: 2025.10.30 SK ON CO LTD

AI summary

Provided are a negative electrode for a lithium secondary battery and a lithium secondary battery including the same, the negative electrode for a lithium secondary battery including a current collector; a first negative electrode active material layer disposed on the current collector and including a first graphite-based active material containing artificial graphite and natural graphite, and a first silicon-based active material; and a second negative electrode active material layer disposed on the first negative electrode active material layer and including a second graphite-based active material containing artificial graphite and natural graphite, and a second silicon-based active material. The first graphite-based active material has a content of the artificial graphite equal to or less than that of the natural graphite, and the second graphite-based active material has a content of the artificial graphite greater than that of the natural graphite.