Multilayer Positive Electrode Structure for Crack-Resistant Compaction

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Solution Overview

Problem

Lithium secondary batteries face challenges in achieving high compaction density and stability due to particle cracking in bimodal-type positive electrode active materials, particularly in high-Ni lithium transition metal oxides, leading to reduced life characteristics and thermal instability.

Innovation Solution

A positive electrode with a multilayer structure comprising a first layer of primary and secondary macroparticles and a second layer of secondary microparticles, along with single-walled carbon nanotubes as a conductive material, to enhance compaction density and prevent cracking during manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If secondary particles formed by agglomeration of primary microparticles are used to increase output and compaction density, then the specific surface area increases, but particle strength decreases causing cracking during rolling process

Engineering Contradiction:

Improveoutput and compaction densityVSAvoidparticle strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent applies segmentation by dividing secondary particles into two distinct size categories: secondary microparticles (D50: 3-7 μm) and secondary macroparticles (D50: 7-20 μm). This bimodal distribution allows smaller microparticles to fill voids between larger macroparticles, increasing compaction density while the smaller size of microparticles reduces stress concentration points that lead to cracking during rolling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements local quality by assigning different functional roles to particles of different sizes within the same electrode structure. Secondary microparticles primarily contribute to filling void spaces and increasing surface area for lithium insertion, while secondary macroparticles provide structural framework and electron conduction pathways. This differentiated functional assignment optimizes both density and mechanical integrity.

Inventive Principle:

Principle #3Local quality

2Reliability

If rolling pressure is increased to prevent short circuit, then electrode stability improves, but particle cracking increases causing gas production and reduced life characteristics

Engineering Contradiction:

Improveelectrode stabilityVSAvoidgas production from particle cracking

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-forming secondary particles through controlled agglomeration of primary microparticles before electrode manufacturing. This pre-agglomeration creates particles with optimized internal structures and reduced defect density, enabling the electrode to withstand rolling pressures without excessive cracking while maintaining stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs composite materials by creating a bimodal mixture of secondary microparticles and secondary macroparticles. The combination of different particle sizes creates a more robust composite structure where smaller particles reinforce the matrix between larger particles, distributing stress more evenly during rolling and reducing gas-generating cracks.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If high nickel content is used to ensure high capacity, then energy density increases, but chemical and thermal stability deteriorate due to structural problems

Engineering Contradiction:

Improvenickel content for high capacityVSAvoidchemical and thermal stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by controlling the particle size distribution parameters of the nickel-based positive electrode active material. By optimizing the D50 ranges of secondary microparticles (3-7 μm) and secondary macroparticles (7-20 μm), and their respective content ratios, the material achieves high nickel content for capacity while the specific particle size parameters prevent structural degradation that would compromise stability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12614725B2Positive electrode for lithium secondary battery and positive electrode and lithium secondary battery comprising the same

Publication Date: 2026.04.28 LG ENERGY SOLUTION LTD

AI summary

A positive electrode for a lithium secondary battery comprising a multilayer structure of electrode active materials. The first positive electrode active material layer comprising a positive electrode active material particles and a conductive material on at least one surface of the current collector. The second positive electrode active material layer positioned on the first positive electrode active material layer and comprising positive electrode active material particles and a conductive material.