Alloyed Copper Foil Orientation Control for Crack-Resistant Li-Ion Collectors

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Solution Overview

Problem

Copper foils used in lithium ion secondary batteries suffer from poor mechanical properties, such as relaxation, wrinkling, and cracking due to thermal expansion and contraction during charge-discharge cycles, affecting the reliability and lifetime of the batteries.

Innovation Solution

A copper foil with controlled amounts of silver, titanium, and sulfur, along with specific crystal orientation indices, enhanced tensile strength, and a treatment layer, to improve mechanical and electrical conductivity, reducing wrinkles and cracks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If copper foil is used as negative current collector, then electrical conductivity is improved, but mechanical properties deteriorate causing relaxation and wrinkling

Engineering Contradiction:

Improveelectrical conductivityVSAvoidmechanical properties

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The patent applies composite material principle by combining copper with small amounts of other elements (silver: 1-50 ppm, titanium: 1-10 ppm, sulfur: 1-20 ppm) to create a composite copper foil structure. This composite structure maintains the excellent electrical conductivity of copper while the added elements form precipitates and strengthen the crystal structure, thereby improving mechanical properties and preventing relaxation and wrinkling.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies parameter changes principle by precisely controlling the concentration of alloying elements (silver, titanium, sulfur) within specific ranges and controlling the crystal orientation index M(220) to 2.05-3.08. By adjusting these parameters, the copper foil achieves optimal balance between electrical conductivity and mechanical strength, preventing both relaxation and wrinkling while maintaining good conductivity.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If copper foil thickness is reduced to achieve small volume, then energy density is improved, but mechanical integrity deteriorates causing cracks

Engineering Contradiction:

ImprovevolumeVSAvoidmechanical integrity

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent uses composite material principle by incorporating silver, titanium, and sulfur elements into the copper matrix. These elements form fine precipitates and strengthen the crystal structure through solid solution strengthening and precipitation hardening, enabling thin foils to maintain high mechanical integrity and resist cracking during thermal expansion and contraction cycles.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies parameter changes by precisely controlling the alloying element concentrations and crystal orientation index M(220) to 2.05-3.08. These parameter optimizations enhance the strength-to-thickness ratio, allowing the copper foil to maintain mechanical integrity at reduced thicknesses, thereby achieving high energy density without compromising reliability.

Inventive Principle:

Principle #35Parameter changes

3Duration of action of moving object

If copper foil undergoes thermal expansion and contraction during charge-discharge cycles, then battery operation is enabled, but cracks develop due to mechanical stress

Engineering Contradiction:

Improvecharge-discharge cyclesVSAvoidcrack resistance

Core Design Contradiction:

Duration of action of moving objectVSStrength

Solution Approach 1:

The patent applies composite material principle by combining copper with silver, titanium, and sulfur elements. The added elements form precipitates and strengthen the crystal structure through solid solution strengthening and precipitation hardening, significantly improving crack resistance and enabling the copper foil to withstand repeated thermal expansion and contraction during charge-discharge cycles.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies parameter changes by controlling the alloying element concentrations and crystal orientation index M(220) to 2.05-3.08. These parameter optimizations enhance the material's fatigue resistance and ductility, allowing it to accommodate thermal stress during cycling without developing cracks, thereby extending battery lifetime.

Inventive Principle:

Principle #35Parameter changes

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 copper foil exhibits improved resistance to relaxation and cracking, maintaining electrical conductivity and mechanical integrity, thus enhancing the performance and longevity of lithium ion secondary batteries.

Implementation Method 1

a copper foil with good electrical conductivity

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

withstand the thermal expansion and contraction during charge-discharge cycles

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20250300189A1Copper foil, current collector and lithium ion secondary battery

Publication Date: 2025.09.25 CHANG CHUN PETROCHEMICAL CO LTD

AI summary

Provided is a copper foil, including 2 ppm to 21 ppm silver, 0.5 ppm to 5.5 ppm titanium, and 2 ppm to 80 ppm sulfur, wherein an orientation index of (220) surface of the copper foil is from 2.05 to 3.08. Also provided are a current collector for a lithium ion secondary battery and a lithium ion secondary battery.