Cathode Loading and Porosity Balance to Prevent Winding Cracks

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Solution Overview

Problem

Cracks occur in the electrode current collector during the winding process of the electrode assembly in lithium secondary batteries with high energy density, leading to disrupted lithium movement paths and side reactions that deteriorate the battery's long-term performance.

Innovation Solution

A positive electrode for lithium secondary batteries is designed with specific loading amount, porosity, and tap density relationships (Y = 10 × L / P × T^2 < 7) to enhance resistance to plastic deformation, using lithium nickel-based transition metal oxides with controlled particle sizes and distributions, ensuring minimal permanent deformation and crack occurrence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the loading amount of active material is increased to improve energy density, then the utilization of limited space is improved, but cracks occur in the electrode current collector during winding

Engineering Contradiction:

Improveloading amount of active materialVSAvoidcrack occurrence in current collector

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies parameter changes by optimizing the loading amount of active material to a specific range (40-60 mg/cm²) and controlling the porosity (20-40%) and tap density (1.8-2.5 g/cc) of the active material layer. These parameter adjustments ensure the electrode has sufficient mechanical strength to prevent cracks during winding while maintaining high energy density through increased active material content.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If the loading amount of active material is increased, then energy density is improved, but the electrode structure becomes more prone to deformation

Engineering Contradiction:

Improveloading amount of active materialVSAvoidresistance to plastic deformation

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent controls the porosity and tap density parameters of the active material layer to optimize the balance between loading amount and mechanical strength. By maintaining porosity within 20-40% and tap density between 1.8-2.5 g/cc, the electrode structure retains sufficient rigidity to resist plastic deformation even with increased active material loading.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining the active material with a binder and conductive additive to form a slurry that is coated on the current collector. This composite structure provides mechanical reinforcement to the active material layer, enhancing its resistance to deformation during the winding process while maintaining high active material content.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP4675696A1Cathode and lithium secondary battery comprising same

Publication Date: 2026.01.07 LG ENERGY SOLUTION LTD

AI summary

The present invention provides a positive electrode for a lithium secondary battery, comprising: a positive electrode current collector; and a positive electrode active material layer positioned on the positive electrode current collector, and satisfying Equation (1) below. Y=10×L/P×T2<7 In Equation (1), L is a loading amount (mg/cm2) of the positive electrode, P is a porosity (%) of the positive electrode, and T is a tap density (g/cc) of a positive electrode active material comprised in the positive electrode active material layer.