Reinforcing Layer for Lithium Battery Current Collectors

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Solution Overview

Problem

Lithium secondary batteries face issues with the breakage of current collectors due to volume expansion caused by non-uniform lithium deposition, leading to poor durability and lifespan, especially in all-solid-state batteries using lithium metal as a negative electrode material.

Innovation Solution

A lithium secondary battery design incorporating a reinforcing layer with a polymer matrix and thermally conductive fillers on the current collectors to mitigate stress and strain from volume expansion, comprising a negative electrode current collector, a negative electrode layer with amorphous carbon and lithium metal, an intermediate layer, a positive electrode layer, and a reinforcing layer applied via a coating solution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lithium metal is used as a negative electrode material to increase energy density, then the theoretical capacity increases to 3,860 mAh/g, but non-uniform lithium deposition causes local volume expansion and current collector breakage

Engineering Contradiction:

Improvetheoretical capacityVSAvoidcurrent collector breakage

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A flexible buffer layer is introduced between the lithium metal negative electrode and the current collector. This buffer layer absorbs and accommodates the local volume expansion that occurs during non-uniform lithium deposition, preventing stress concentration and subsequent breakage of the current collector while maintaining electrical contact and ionic conductivity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The buffer layer is constructed from composite materials with specific mechanical and electrochemical properties that enable it to withstand volume expansion while maintaining structural integrity. The composite structure combines materials that provide both flexibility for expansion accommodation and sufficient strength to prevent current collector failure.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon-based material is used as a negative electrode active material to achieve high energy density, then the energy density increases about 10 times greater than graphite, but the degree of expansion during charging reaches about 400%

Engineering Contradiction:

Improveenergy densityVSAvoidexpansion degree

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

A flexible buffer layer is positioned between the silicon-based negative electrode active material and the current collector. This buffer layer provides a compliant interface that absorbs the extreme 400% volume expansion of the silicon material during lithium ion insertion, preventing mechanical failure of the current collector while maintaining electrical connectivity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The buffer layer's mechanical properties are specifically designed to match and accommodate the expansion characteristics of the silicon-based material. By adjusting the buffer layer's thickness, composition, and mechanical properties, the system can tolerate the large volume changes without compromising the structural integrity of the battery components.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If graphite is used as a negative electrode active material, then the structure stability is maintained with about 10% expansion, but the energy density is limited and cannot meet high energy density requirements

Engineering Contradiction:

Improvestructure stabilityVSAvoidenergy density

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

The invention uses composite negative electrode structures that combine graphite with higher-capacity materials such as silicon-based materials or lithium metal. The buffer layer in this composite structure is specifically designed to accommodate the expansion of the high-capacity material while maintaining the overall structural stability needed for repeated cycling, thereby achieving both high energy density and structure stability.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS20230178715A1Lithium secondary battery with high durability and manufacturing method thereof

Publication Date: 2023.06.08 HYUNDAI MOTOR CO LTD

AI summary

Provided are a lithium secondary battery having high durability and a method for manufacturing the same. The lithium secondary battery includes a reinforcing layer positioned on the outside of at least one of a negative electrode current collector and a positive electrode current collector and including a matrix containing a polymer and a thermally conductive filler dispersed in the matrix.